fall design report team19

7/17/2019 Fall Design Report Team19

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Paul McKinnon (B00377619)

Justin Pruss (B00547700)

Raymond Doiron (B00525545)

Justin Wong (B00563186)

Project Supervisor:

Dr. Peter Allen

Project Coordinator:

Dr. Clifton Johnston

Team 19

Fall Design Report

MECH 40153 December 2013



MECH 4015 Team #19

Combined Heat and Power

Dept. of Mechanical Eng. of 53



MECH 4015 Team #19



Table of Contents

Table of Contents .......................................................................................................................................... 3

List of Figures ................................................................................................................................................ 5

List of Tables ................................................................................................................................................. 6

1. Project Information ............................................................................................................................ 7

1.1. Project Title ................................................................................................................................. 7

1.2. Project Customers ....................................................................................................................... 7

1.3. Group Members .......................................................................................................................... 7

1.4. Useful Definitions and Acronyms ................................................................................................ 7

2. Executive Summary ............................................................................................................................ 9

3. Background and Context .................................................................................................................. 10

3.1. Background and Overall Objective............................................................................................ 10

3.2. Requirements ............................................................................................................................ 11

4. Summary of Conceptual Design Alternatives ................................................................................... 13

4.1. Air Cooled Generator ................................................................................................................ 13

4.2. Shell and Tube Heat Exchanger................................................................................................. 13

4.3. Plate Heat Exchanger ................................................................................................................ 14

4.4. Selected Design Concept ........................................................................................................... 14

5. System Architecture ......................................................................................................................... 16

5.1. Selected Design ......................................................................................................................... 16

5.2. Subsystem Components ........................................................................................................... 17

5.2.1. Generator ........................................................................................................................... 17

5.2.2. Control system ................................................................................................................... 18

5.2.3. Exhaust heat exchanger ..................................................................................................... 19

5.2.4. Engine heat exchanger ....................................................................................................... 26

5.2.5. Photovoltaics and battery bank ......................................................................................... 29

6. Feasibility and Risk Assessment ........................................................................................................ 30

6.1. Engine Type ............................................................................................................................... 30

6.2. Motor Alternative ..................................................................................................................... 33

6.3. Cooling Methods ....................................................................................................................... 33

6.4. Fuel Type ................................................................................................................................... 34

6.5. Starting and Control System ..................................................................................................... 34

6.6. Structural System ...................................................................................................................... 35

6.7. Heat Exchanger ......................................................................................................................... 35

7. Testing and Verification .................................................................................................................... 36

7.1. Methodology ............................................................................................................................. 36



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7.2. Preliminary testing .................................................................................................................... 36

7.2.1. Exhaust temperatures ........................................................................................................ 36

7.2.2. Engine temperatures .......................................................................................................... 37

7.3. Complete system testing and verification ................................................................................ 37

8. Project Management Plan ................................................................................................................ 40 8.1. Organizational Responsibilities ................................................................................................. 40

8.2. Work Breakdown Structure ...................................................................................................... 40

8.3. Schedule .................................................................................................................................... 42

8.4. Specialized Facilities and Resources ......................................................................................... 43

9. Cost Estimates and Budget ............................................................................................................... 44

Bibliography ................................................................................................................................................ 46

Bibliography – CAD Drawings...................................................................................................................... 48

Appendix A Potential Loading Scenarios ............................................................................................... 49

Appendix B Honda GX 160cc Power Curve ............................................................................................ 50

Appendix C Theoretical Engine Exhaust Characteristics ....................................................................... 51

Appendix D Shell and Coil Heat Exchanger Design ................................................................................ 52

Appendix E CFD Model of Coolant through Shell and Coil Heat Exchanger .......................................... 53



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List of Figures

Figure 1 Air cooled engine fins ............................................................................................................. 13

Figure 2 Example of plate heat exchanger ........................................................................................... 14

Figure 3 CHP Deliverable ...................................................................................................................... 15

Figure 4 CHP Generator CAD Image ..................................................................................................... 17

Figure 5 CSD-01 CHP Control System P&ID Diagram ........................................................................... 18

Figure 7 Staggered tube configuration ................................................................................................. 20

Figure 6 Aligned tube configuration ..................................................................................................... 20

Figure 8 Finless heat exchanger* ......................................................................................................... 22

Figure 9 Finned heat exchanger* ......................................................................................................... 22

Figure 10 Cross section of shell and coil heat exchanger ....................................................................... 26

Figure 11 Shell and coil heat exchanger specifications .......................................................................... 27

Figure 12 Generator selection risk chart ................................................................................................ 30

Figure 13 Control and starting system risk chart ................................................................................... 34 Figure 14 Structural enclosure risk chart ............................................................................................... 35

Figure 15 Exhaust heat exchanger risk chart ......................................................................................... 35

Figure 16 Engine heat exchanger risk chart ........................................................................................... 35

Figure 17 Actual vs. Theoretical HP calculator ....................................................................................... 37

Figure 18 Testing process flow diagram ................................................................................................. 39

Figure 19 Organizational Breakdown ..................................................................................................... 40

Figure 20 Work breakdown structure .................................................................................................... 41

Figure 21 Fall Project Schedule .............................................................................................................. 42

Figure 22 Winter Project Schedule ......................................................................................................... 42



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List of Tables

Table 1 Dwelling description ............................................................................................................... 11

Table 2 Summary of micro-CHP system components ......................................................................... 16

Table 3 Overall heat transfer coefficients ........................................................................................... 21

Table 4 Finless vs. Finned heat exchanger example ........................................................................... 22 Table 5 Single vs. double pass example values ................................................................................... 24

Table 6 Single vs. double pass velocity results .................................................................................... 24

Table 7 Material properties ................................................................................................................ 25

Table 8 Generator set feasibility assumptions .................................................................................... 31

Table 9 Price per GJ comparison ......................................................................................................... 34

Table 10 Project design and conceptualization facilities ...................................................................... 43

Table 11 Project construction facilities ................................................................................................. 43

Table 12 Project testing facilities .......................................................................................................... 43

Table 13 Budget breakdown ................................................................................................................. 44



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1.

Project Information

1.1. Project Title

Micro combined heat and power system for a residential dwelling.

1.2.

Project Customers

Peter Allen [email protected]

Paul Sajko [email protected]

Thermo Dynamics Limited, Burnside, Nova Scotia

1.3. Group Members

Justin Pruss [email protected]

Paul McKinnon [email protected]

Justin Wong [email protected]

Raymond Doiron [email protected]

1.4. Useful Definitions and Acronyms

CHP – Combined Heat and Power. The production of electricity through the use of

a generator while recovering waste heat for household heating.

Efficiency – the ratio of energy delivered by a system to the energy supplied for its

operation.

ICE – Internal combustion engine.

Engine – Internal combustion engine to provide the work to the motor.

Motor – A brushed DC electric motor which receives work from the engine to

produce electricity.

Generator – The combination of both an engine and a motor.

SI – Spark ignition. Spark initiated combustion.



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CI – Compression ignition. Adiabatic combustion process.

WOT – Wide open throttle, indicating engine is operating at peak output.

BHP – Brake horsepower, total available horsepower from an engine.

NG – Natural Gas.

PG – Propane Gas.

HX – Heat exchanger.

PHE – Plate heat exchanger

DHW – Domestic hot water.

PV – Photovoltaics.



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2. Executive Summary

This report supports the development of combined heat and power technologies through an

intensive engineering analysis of their:

Economic viability

Optimal generator specifications

Potential heat exchanger designs

Domestic integration process

Risks as a full time power source

A breakdown and justification of the system architecture is provided with detailed calculations

highlighting the design selection process. Componentry involved in the final design includes:

10 kW, natural gas fired, reciprocating generator

Cross flow, tube bank exhaust heat exchanger

Concentric shell and coil coolant heat exchanger

Thermally adjusted control system

Simulated photovoltaic input with battery bank

Integration and flexibility is a founding principle for the feasibility of the designed combined heat

and power system. Ensuring that the system can operate on or off grid, easily switch between

natural gas and propane, and function with supplementary inputs is an asset for introducing this as

a competitive energy alternative.

The project management is organized as a top down approach, with Dr. Peter Allen heading the

team and the four students equally sharing responsibilities. Each student has specialized in a

particular field for the project and will continue to focus there in order to increase the level of

detail.

The next steps forward are to acquire a generator before the end of December 2013 to allow for the

finalization of detailed design. Construction on the heat exchangers is scheduled to begin byJanuary 24th 2014.



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3. Background and Context

3.1.

Background and Overall Objective

Nationally the cost of energy, and in particular electricity, is steadily on the rise. In Nova Scotia, the

residential electricity rates are 13.790 ȼ per kilowatt hour and also include a $10.83 per month fee

from the only company allowed to provide electricity (www.nspower.ca). The fact that profits of

this company have risen every year since 2009 is not lost on the consumers and has left some

looking for alternative sources.

A recent solution for the residential market has been micro CHP systems which can be integrated

into the home heating and power system, in a relatively small package. This gives home-owners a

source of efficient and low cost energy, relative to electricity obtained from local power companies.

Micro CHP systems also give home-owners the opportunity to produce enough energy where extra

energy can be sold back to the grid for profit. Micro CHP packages can incorporate other

complimenting systems such as photovoltaics, battery banks, and wind turbines which can

ultimately lead to a home becoming completely self-sufficient with no reliance on power from the

grid.

The market for micro CHP systems for residential use is still small, mostly due to the fact that with

limited economies of scale the systems are expensive to obtain and install (Paparone, 2009). This is

common across the board for renewable energy resources; the large initial cost is unattractive tohome-owners, even if it pays off in the long run. The benefit of CHP systems is that they are more

flexible than other off grid systems, and unlike other sources such as wind and solar, CHP systems

provide predictable and reliable heat and power. This project intends to challenge the large

principal investments needed to enter the independent energy market through affordability and

integration with existing residential systems.



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3.2.

Requirements

The primary requirement for this project is to provide a fully testable micro-CHP system. This

system will be economically viable and competitive with reference to current turn-key CHP

systems. During testing, this micro-CHP system will provide the equivalent heating and electrical

loads of a specified single family dwelling. The requirements for this project are based off of the

characteristics of the dwelling and are described as follows:

Table 1 Dwelling description

Component Details

Physical Description 2 story detached dwelling

2000 ft2

Wood frame construction

Unheated; below grade foundation

R20 walls and R40 roof Double glazed; 1/4” air gap windows

Electrical Demands 8 – 9 kW peak load demand

Thermal Demands 18 – 20 kW peak load demand

Additional project design constraints have been provided by the project customer.

Liquid cooled generator set

Economically competitive fuel source

From this description, and the design constraints, the following project requirements have beendeduced for this CHP system:

Construct a CHP system.

o Satisfy minimum 8 kW electrical load

o

Satisfy minimum 18 kW thermal load

Harness waste heat from engine to assist in satisfying thermal loads

o

Achieve an overall system (thermal) efficiency of 80% or greater.

o Exhaust

Construct gas to liquid heat exchanger

o Engine block

Construct liquid to liquid heat exchanger



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Simulation of the theoretical integration of photovoltaic and battery systems.

o

Theoretical photovoltaic system size

o Theoretical battery bank size

Quantifiable and repeatable project results



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4. Summary of Conceptual Design Alternatives

4.1.

Air Cooled Generator

A major design consideration for this project is the type of cooling system employed by the

generator. Initially, it was considered that an air cooled engine be used due to their simplicity and

reduced cost. The air cooled engine uses annular fins around the cylinder head and engine body to

radiate heat created during the combustion process, seen in Figure 1. However since this heat is

radiated to atmosphere, this design fundamentally

contradicts the purpose of the entire project which is to

recover the waste heat from the engine. The engine

cooling system is responsible for dissipating nearly 40% of

the total heat during the combustion process which is a

substantial quantity of thermal energy (Pulkrabek 2004).

To observe this quantitatively, a typical 10 kW generator,

running at full capacity, burns the energy equivalent of 50

kW in natural gas (Cutler-Hammer). Since the internal

combustion engine is only about 25 % efficient, this means

75 % of the energy in the fuel, or 35 kW, is lost to heat, sound, and vibrations. From this, 35 % of

the heat dissipation is accomplished through the engine cooling system, amounting to over 13 kW.

Being that this is a sizeable portion of the project ’s thermal load, this shows quantitatively that theheat from the engine must also be collected.

4.2.

Shell and Tube Heat Exchanger

The team had initially decided to use a shell and tube heat exchanger to extract heat from the

exhaust gases. However, after consultation with industry experts, it was decided that it was too

difficult to build a shell and tube heat exchanger with the resources available and therefore, it has

been decided that a tube bank heat exchanger would be a more viable option. This was not a major

change in design, the exception being for manufacturing, as a lot of the features of the tube bank

heat exchanger will remain the same as those decided for the shell and tube. The tube bank heat

exchanger will utilize a cross flow, staggered tubes design, with multiple tube passes and even the

same materials as the shell and tube heat exchanger.

Figure 1 Air cooled engine fins



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4.3.

Plate Heat Exchanger

To further recover heat from the engine, a liquid to liquid heat exchanger will replace the radiator

to heat water instead of radiating the heat to the atmosphere. The initially chosen type of heat

exchanger to recover this heat was a plate heat exchanger (PHE). These heat exchangers are ideal

for liquid to liquid heat transfer due to their effectiveness and compactness. PHEs consist of

patterned plates separated by gaskets. The liquids flow between the plates in an alternating and

counter flow manner as shown in Figure 2.

Figure 2 Example of plate heat exchanger

(http://www.solarme.com/heatexchanges.html)

The downfall of this design is the manufacturing of the plates themselves. The plates are sized and

shaped using large metal presses which can produce the plates with a consistent pattern so when

they are bolted together; there is no leakage or mixing of liquids. Forming these plates consistently,

without a specialized metal press, would be difficult and time consuming. These presses required

for manufacturing are not widely available and acquiring a press or special ordering plates would

prove to be a large expense. Due to budgetary and time constraints, it was concluded that it would

be beneficial to choose a different type of heat exchanger that could be more easily fabricated with

available resources.

4.4. Selected Design Concept

The selected design for this project will consist of a controlled power generating system with heat

recovery, as well as simulated supplemental power sources and storage. CHP systems incorporate

many different components to produce electricity, harness and provide heat, and control the overall

system functioning. They are also able to have other sources of energy supplement the system to

enhance its overall output and efficiency. The goal of this design is to bring all of these areas

together, focusing on the main cogeneration system, while providing a full simulation,

incorporating renewable energy sources, and power storage and distribution systems.



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The design that will be undertaken will have a 15

kW generator as the foundation of the system. This

generator will utilize an 18-20 hp, liquid cooled, NG

fired engine, from which heat will be recovered.

Given that ICE’s are 25-30 % efficient, this leaves up

to 30 % of the energy wasted through the engine

block and between 30-50 % of the energy released

to the atmosphere from the exhaust (Ugursal,

2005). Harnessing this heat can raise the

efficiency of the system substantially. Heat will be recovered from the sources above through two

heat exchangers. The existing radiator on the liquid cooled engine will be replaced by a liquid to

liquid shell and coil heat exchanger to extract the heat from the engine coolant. The heat from the

exhaust will be harnessed using a gas to liquid tube bank heat exchanger incorporated into the

existing system. The recovered heat will be used to produce DHW.

CHP systems can also be supplemented with photovoltaics to increase energy production as well as

battery banks to store produced electricity. Of course, these systems contain many other

components and control systems which would have to be properly sized to the design load. In

order to demonstrate the system’s ability to integrate with supplementary energy sources, the CHP

system will be designed to respond to simulated PV input.

Figure 3 CHP Deliverable



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5. System Architecture

5.1.

Selected Design

The selected design for this project, as explained in the previous section, will consist of a 10 kW

generator. Heat will be recovered from the engine through two heat exchangers to provide DHW.

The system will also be simulated with photovoltaic input as well as power storage through the use

of a battery bank. The CHP system and sub components are explained in more detail below.

Table 2 Summary of micro-CHP system components

Sub-System Component Details

Engine Reciprocating internal combustion engine Duel fuel input options:

Natural gas or propane

3200-4500 RPM

18-20 HP range

Long-term maintenance

plans

Generator DC electric motor 10-14 kW range

Brushed motor

Heat Generation Exhaust waste heat driven exchanger

Engine waste heat driven exchanger

Tube bank (Counter Flow)

Gas to liquid heat transfer

Shell and Coil (Counter Flow)

Liquid to liquid heat transfer

Control System Microcontroller Arduino Uno

Analog and digital inputs

Digital outputs

Supplementary

Systems

Photovoltaics

Battery bank

Simulated system input

Simulated system input

Structural System mounting frame for mobility and

transportation Fit inside the wheel wells of

standard half-ton truck

Aid in engine waste heat

collection

L x W restriction is 6’ by 4’6”

Steel construction

Unit enclosure



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5.2.

Subsystem Components

5.2.1. Generator

The electrical demands of the specified dwelling dictate

the size of the generator selected for the CHP system.

For selection purposes, the size of a generator is defined

by its electrical output and not the engine output since

there are losses in the conversion of mechanical energy

to electrical energy. These loses are solved for in the

feasibility section of the report.

5.2.1.1. Generator sizing

It is important to correctly size the generator set powering the CHP. An undersized generator will

be over worked and suffer premature wear which will most likely result in the failure of the system.

An oversized generator will suffer from inefficiencies and in extreme cases may even begin carbon

fouling (Briggs and Stratton). In the case of our specified dwelling, the generator set will be sized at

10kW, which will allow for the engine to work within safe operating conditions while not being so

large that its power is not utilized. This conservative generator sizing will:

Ensure adequate power and heat supply

Reduce the likelihood of overheating

Increase the time between service intervals

5.2.1.2. Cooling methods

The type of cooling system employed by the engine is a very important aspect of the generator

selection. Generally an ICE is expected to lose 30 % of its waste heat through the block, which when

operating in the kW range, is a significant amount of heat (Urgusal 2005). The complication with

this feature is that below 10 kW nearly all generators are air cooled and therefore release that heat

to atmosphere; and given the importance of heat extraction in a CHP, this becomes an undesirable

feature. Liquid cooling has been classified as a necessity to achieving the overall efficiency of 80 %or above. Fortunately, since we have elected to conservatively estimate the size of the generator,

liquid cooling is a more readily available engine feature.

The engine and generator are selected as a unit since the complications of specifying and mating an

internal combustion engine with an electric motor exceed the scope of the project.

Figure 4 CHP Generator CAD Image



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5.2.2. Control system

The inputs from the household power control system will be fairly simple; the CHP will receive a

binary signal, off or on, depending on the system parameters set by the household management

system. The CHP control system is going to need to respond to the state of the household heating

system and the operating state of the engine and the in order to optimize the effectiveness of the

heat recovery processes as well as manage the temperature of the engine.

Figure 5 represents the first iteration of the piping, instrumentation, and control plan for the CHP

system. Presently the system is scheduled to be controlled by an Arduino Uno microcontroller; it is

capable of handling up to 14 digital inputs/outputs, 6 of which can be used as pulse-width

modulation outputs, and 6 analog inputs. Refer to Figure 5 for the system descriptions in the

following sections.

Figure 5 CSD-01 CHP Control System P&ID Diagram



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5.2.2.1. Engine coolant circuit

The temperature of the coolant leaving the engine will be measured using a thermistor (TT03)

wired into a bridge circuit connected to an analog input of the microcontroller (A0). This

temperature will be compared to the incoming water temperature (TT01) to determine if sufficient

engine cooling can be accomplished through the engine side HX; if yes, then a motorized valve

(MV04) will divert coolant flow to the engine HX, if not then the valve will divert the coolant flow to

the radiator and the radiator fan will be turned on. Both paths of the engine coolant return to a

common pipe that flows back to the engine for recirculation. The coolant pump will likely be

operated by the native engine control circuit, further control system design and planning may be

required once the generator has been acquired, depending on its design.

5.2.2.2. Engine exhaust circuit

The engine exhaust will be ducted to the ambient through one of two possible paths: the exhaust

HX, or a pipe directly to atmosphere. The microcontroller will read the incoming water

temperature (TT01) compare it to the outlet water temperature of the exhaust HX and determine if

the system is thermally saturated; if no, then exhaust gasses will be routed through the HX, if yes,

then the exhaust will be vented directly to the ambient to prevent overheating the water or damage

to the HX. Direction of the exhaust gasses will be accomplished by a motorized valve (MV01).

5.2.2.3. Domestic hot water circuit

The microcontroller will compare the temperature difference between the HX supply (TT01) to theexiting temperatures of both the engine and exhaust HXs (TT04 and TT02 respectively). This

information will be used to modulate the flow of water to each of the HXs (MV02 and MV03) to

optimize heat recovery. In order to maintain the desired flow in each of the parallel how water

circuits the microcontroller will record the pressure drop across each of regulating valves (PT02 vs.

PT01 and PT03 vs. PT01 for engine and exhaust HXs respectively); this information will be used, in

conjunction the position information of the engine coolant valve (MV04) and the exhaust diverter

valve (MV01) positions, to control the speed of the water pump.

5.2.3. Exhaust heat exchanger

The selection process of the exhaust side heat exchanger is one that involves many different aspects

of heat exchanger design. Since the exhaust side will be using a gas to liquid interface, a tube bank

heat exchanger will be used due to the additional turbulence created from the cross flow

configuration. Tube bank heat exchangers also allow for a more robust and easily constructible



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design which is desirable given the time constraints of the project. The design parameters of the

exhaust heat exchanger are outlined in detail throughout this section.

5.2.3.1. Staggered tubes versus aligned tubes

The evaluation of tube configuration for a cross flow tube bank heat exchanger lies between astaggered or aligned design. This variation in tube configuration is important for gas to liquid heat

exchangers where having additional turbulence is especially important for increasing the heat

transfer coefficient. Bergman (2011, pg 469) supports this by saying that …”the more torturous

flow of a staggered arrangement, heat transfer is favoured.” Figure 6 and Figure 7 illustrate the

difference between staggered and aligned tube configurations.

Figure 7 Staggered tube configuration

Heat transfer, in this case, is affected by improving the heat transfer coefficient ho which contributes

to the overall heat transfer coefficient U through:

where,

and

⁄

These equations show that by increasing the Nusselt number, , then the heat transfer coefficientcan be increase which serves to improve the effectiveness of the heat exchanger.

The staggered design improves the Nusselt number through the coefficients C1 and C2, which can be

found in tables 7.5 and 7.6 of Bergman (2012) pg470 and 471, respectively. For each of the cases,

Figure 6 Aligned tube configuration



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these coefficients are large for the staggered configuration, proving that this offset type

configuration is advantageous for this design.

As a result, the exhaust tube bank heat exchanger will be constructed using a staggered tube

configuration.

5.2.3.2. Tube fin evaluation

The purpose of fins, with regards to any form of heat transfer, is to increase the effective surface

area thereby improving the amount and the rate at which heat is transferred. Generally fins are

especially important in gas to liquid heat exchangers since the gas tends to lower the overall heat

transfer coefficient. In order to evaluate the rate at which heat is transferred, the heat transfer

equation can be employed:

Where: A is the total area

U is the total heat transfer coefficient

is the log mean temperature

To get an idea of just how much the heat transfer coefficient is compromised due to the low thermal

conductivity (k) of the exhaust gas Table 3 from Bergman 2011 shows some common heat transfer

coefficients.

Table 3 Overall heat transfer coefficients

Fluid Combination U ( ⁄ )

Water to water 850-1700

Water to oil 110-350

Steam condenser (Water in tubes) 1000-6000

Ammonia condenser (Water in tubes) 800-1400

Alcohol condenser (Water in tubes) 250-700

Tube heat exchanger (Water in tubes, air in cross flow) 25-50

In this project the exhaust heat exchanger, with a gas to liquid interface, is shown above to yield an

overall heat transfer coefficient of 25-50 W/m2K, whereas the engine cooling system heat

exchanger will experience a heat transfer coefficient in the order of 850-1700 W/m 2K. This is an

entire order of magnitude different requiring compensation to ensure heat transfer effectiveness.



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Generally increasing the area of the heat exchanger is the solution to this problem; accomplished

through the addition of fins on the tubes or simply by using more tubes. Exhaust heat exchangers

provide a unique situation which requires careful consideration due to the high temperature of the

gases entering the heat exchanger and the fouling that inherit with hydrocarbons.

Solving for the surface area then becomes and if all other variables are held constant,

the effect that fins have on this heat exchanger can be quantified. A short example best illustrates

this.

If, for example, the objective is to rid 12 kW of heat, using a calculated of 220.71 K and a heat

transfer coefficient of 40 W/m2K, as listed above (Bergman 2011), the required surface area of the

heat exchanger is then 2.265 m2. This area can then be satisfied through a finned or finless

configuration as seen below.

Figure 8 Finless heat exchanger* Figure 9 Finned heat exchanger*

*(Images from real-world-physics-problems)

Table 4 Finless vs. Finned heat exchanger example

Finless heat exchanger Finned heat exchanger

Area of 1 Tube

Fin area

Number of fins per tube

=

=

=

0.0236 m2

0.0 m2

0

Area of 1 tube

Fin area(4cmx4cmx0.01cm)

Number of fins per tube

=

=

=

0.0236 m2

7.3e-4 m2

30

Number of tubes needed = 40 tubes = 21 tubes

While the example does show that fins reduce the number of tubes needed for the equivalent heat

transfer rate, it also shows that the reduction in the number of tubes is not so substantial that it

cannot be overcome through simpler means. This is because the temperature at which the exhaust



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enters the heat exchanger is so large the log mean temperature effectively acts as that

compensation in the heat transfer equation.

Finless tubes also assist in reducing the fouling factor of the heat exchanger. This will increase the

time between service intervals and simplify the maintenance procedures during cleaning. With thissimplification in the design, the manufacturing difficulty and cost for the tube bank heat exchanger

is greatly reduced.

With this in mind, and on the direction of the project supervisor, the area requirements of the

exhaust heat exchanger will be met using finless tubes.

5.2.3.3. Tube multi-pass evaluation

The single pass heat exchanger offers a simple build, where the fluid enters at one end and then

exits at the other end. However, heat transfer rates are highly dependent on fluid velocity and thus

the Reynolds and Nusselt numbers (Thulukkanam, 2013). One way to increase the fluid velocity is

by increasing the number of passes that the fluid makes within the same size shell. For example, if

there are 40 tubes in the shell in a single pass, the volume of water is evenly divided among the 40

tubes. Conversely, if a double pass system is used, then 20 tubes will carry the fluid in and out the

same side of the heat exchanger. This effectively doubles the lengths of the tubes, but also

decreases the number of tubes by half, from 40 to 20. If the mass flow rate (kg/s) remains the same

then the fluid velocity (m/s) will have to increase by:

Mass flow rate,

Velocity,

Since the mass flow rate and density remain constant, but the cross sectional area reduces by a

factor of two, the velocity must also increase by a factor of two.



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For example, if the given data set is as follows:

Table 5 Single vs. double pass example values

ṁ 5.0 kg/s

ρ 998.0 kg/m3

AC single pass 0.0785 m2

AC double pass 0.0393 m2

Radius, r 0.025 m

N double pass 20

N single pass 40

Then the resulting fluid velocities are shown in the table below.

Table 6 Single vs. double pass velocity results

Velocity for single pass Velocity for double pass

0.0638 m/s 0.1276 m/s

Doubling the velocity and length also quadruples the Reynolds number, as it is calculated by:

This then lends to the desirable effect of an increased heat transfer rate with the same material

amount of tubes simply by increasing the passes from one to two. The Nusselt number increases in

relation to the Reynolds number, shown by:

⁄

⁄

The choice to go with a multi-pass tube bank heat exchanger will depend on the complexity of

manufacturing a multi-pass heat exchanger compared to a single pass heat exchanger. However,

the number of passes is also restricted by the increased pressure drop that is incurred due to the

longer tubes (Thulukkanam, 2013). The preference would be to build a multi-pass for its increased

heat transfer rate with essentially the same bill of material.



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5.2.3.4. Material selection

Material selection is pertinent to a heat exchangers efficient and reliable operation. CHP

exchangers in particular are subject to high thermal stresses due to large temperature gradients

and rapid rates of heating. Exhaust side engine temperatures can exceed 700°C, all the while the

cold water enter the exchanger can be as low at 10°C. Allowing for mixed flow on the shell side of

the heat exchanger is one method to minimizing thermal stresses however much of the design

comes down to using the appropriate materials. A balance between effective temperature working

ranges, thermal conductivities, rates of thermal expansion, and of course unit costs are all crucial

for optimizing material selections.

Copper, steel, stainless steel, and aluminum are the primary materials under evaluation. Titanium

is far too expensive for this section of project and as such will not be considered. Table 7 is a

summary of the important properties of each material.

Table 7 Material properties

Copper Steel Aluminum Stainless Steel

Cost (2’x2’x¼”)* $427.58 $208.33 $92.00 $241.00

Thermal expansion x 106 ** 16.6 13.0 22.2 17.4

Thermal conductivity

** 398-400 43-51 215-258 12-44

Safe working temperature range** Up to 400 °F

(Soldered ends)

Up to 700 °F Up to 300 °F Up to 1500 °F

*McMaster - Carr 2013

**Engineering Toolbox

From these properties we can see that finding a single material to work for the entire exchanger is a

difficult task. For the purposes of performance the main consideration is the thermal conductivity,

and we see that copper exhibits the highest conductivity by far. With this in mind however, copper

does not have the same broad range of operating temperatures as other materials such as stainless

steel. This means that any material sustaining a high temperature, in our case upwards of 1100 °F,

even for a very brief section, will most likely have to be stainless steel. A final consideration is the

workability of these materials for manufacturing. Copper and stainless steel cannot be soldered or

brazed by any means making any required bonding between them prohibitively difficult (Injection

Welding, 2013).



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From this evaluation the exclusive use of stainless steel, for the tubes and enclosure of the tube

bank, allows for the best balance between performance and reliability.

5.2.4. Engine heat exchanger

The heat will be recovered from the engine block through the engine coolant. Liquid cooled enginesuse a radiator to cool the coolant, through the use of fans, by passing air over finned tubes. A shell

and coil heat exchanger will be used to harness this heat from the engine coolant. Shell and coil

heat exchangers consist of a concentric cylinder shell around a helically wound tube, as shown in

Figure 10. This heat exchanger was chosen for its simplicity and effectiveness. Shell and coil heat

exchangers are compact due to the coiled tube

within the shell which creates a large heat

transfer surface area. Water will flow tube

side while engine coolant flows over the tubes

on the shell side.

The shell and coil heat exchanger for this

project will be sized according to the

characteristics of the generator acquired using

the spreadsheet as shown in Appendix D,

taking the design parameters discussed below

into account.

5.2.4.1. Coil design

The coil dimensions are constrained by the applications of the heat exchanger and the flow it will be

experiencing, which ultimately comes down to the inner and outer diameter of the tube. For the

purposes of this project, ½” copper tube is sufficient with minimal wall thickness since thepressures within the heat exchanger will not reach unreasonable values. This dimension is then

used to determine the shell dimensions.

Another dimension of the coil that must be specified is the pitch. The pitch of the coils is set to

maximize the turbulent flow through the shell over the coils as well as the heat transfer area

Figure 10 Cross section of shell and coil heat

exchan er



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created by the helical coil. The pitch is optimized to ensure the compactness of the heat exchanger.

Creating too small of a pitch, the turbulence decreases with the surface area increasing whereas a

large pitch increases the turbulence while decreasing the surface area (Jayakumar, 2012). A typical

coil pitch is optimized by setting the pitch equal to 1.5 times the outer diameter of the coil tube (d o),

as shown by p Figure 11 (Patil, Shende, & Ghosh, 1982).

Figure 11 Shell and coil heat exchanger specifications

*(Patil, Shende, & Ghosh, 1982)

The final specification of the coil is the length of tube, or number of coils required to achieve the

required heat transfer. Depending on the amount of heat available from the coolant, the length of

coil will be such that the allowable heat transfer from the coolant is maximized. The heat exchanger

cannot extract too much heat to have coolant return to the engine at too low a temperature which

would negatively affect the operation of the engine and its components. For the aforementioned 15

kW generator, the minimum temperature of coolant to the engine is specified at 76 °C (Caterpillar,

2007), which would be similar across different manufacturers.

5.2.4.2. Shell dimensions

The shell of shell and coil heat exchangers house fluid which is turbulent due to the helical coil. The

shell dimensions are based off of the coil chosen for the heat exchanger so it can be properly housed

to make the heat exchange as effective as possible. Further, t he concentric cylinder’s dimensions

must be such that the flow is not impeded to create too large of a pressure drop and must allow the



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fluid to flow at a velocity which meets the heat transfer requirements for that heat exchanger (Patil,

Shende, & Ghosh, 1982).

In the case of generators, the engine coolant will be flowing at a velocity created by the engine’s

water pump and controlled by the thermostat. Since generator engines generally run at constantRPM for the production of electricity, the flow rate for the engine coolant will also remain constant.

With a constant flow rate of engine coolant, the shell dimensions are decided based on an

acceptable pressure drop through the shell. In an engine with a coolant flow rate of 0.0063 m3/s,

the pressure drop through the radiator is approximately 10 000 Pa (Stewart Components, 2004).

Since the flow rate for a typical 15 kW generator engine is approximately 0.00075 m3/s (Caterpillar,

2007), and knowing that the pressure drop is proportional to the flow rate of the coolant, as long as

the pressure drop through the heat exchanger follows this proportionality, the flow rate of the

coolant will not be dramatically affected. In the case of the 15 kW generator, a pressure drop of1100 Pa or less is well within the acceptable range.

It then follows that once the dimensions of the shell are determined; a pressure drop calculation

must be performed to ensure that the allowable pressure drop from above is not exceeded. A

general rule of thumb for the dimensions of the outer and inner diameter of the shell are such that

there is a space between the wall of the shell and the coil equal to half of the outer diameter of the

coil tube as shown in Figure 11(Patil, Shende, & Ghosh, 1982). The length of the shell is determined

based on the number of coils and the pitch. Once these two dimensions are specified, the length of

the shell which covers the coils is simply the product of the pitch and the number of coils.

5.2.4.3. Material selection

The typical materials used in heat exchangers are copper due to its attractive heat transfer

properties and steel due to its strength and cost. Heat exchangers which do not utilize copper are

those which deal with temperatures exceeding 400°C, however in the case of engine coolant,

temperatures will not exceed this range making copper an ideal material. Since copper makes a

very effective heat transfer interface between fluids, it is not necessary to use it as the shell material

to conduct heat out of the exchanger, along with the higher cost of copper. For this reason, stainless

steel will be used as the shell material due to its strength, corrosion resistance, and lower cost.

Stainless steel also has a lower thermal conductivity than copper allowing more heat from the

coolant to stay within the heat exchanger.



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5.2.5. Photovoltaics and battery bank

CHP systems can be integrated with a photovoltaic (PV) system as well as a battery bank as an

alternative energy source to supplement the generator. The current market is expanding with

more efficient solar panels at lower costs becoming available. PV systems can supplement CHP

systems to provide power in the summer when heat is not necessarily required from running the

generator. A PV system could also provide power to the battery bank, and at times when the PV

system cannot keep the batteries above a certain voltage, the CHP system can start up to supply the

extra power required. This configuration requires a control system to monitor the battery bank

voltage, determine when the CHP needs to turn on, and when heat must be released. For the

purposes of this project, the PV input will be simulated as well as only a small scale battery bank

used due to budgetary constraints.

5.2.5.1.

Photovoltaic system

PV systems use solar energy to produce electrical energy. In Halifax, NS, the average solar power

that can be harnessed for a horizontal surface is 3.52 kWh/m2 per day in the summer (Green Power

Labs, 2009). This translates into satisfying the 500 kWh base load of a typical residential dwelling

with only 18 m2 of panel. This demonstrates the feasibility of supplementing a CHP system with

photovoltaics which would allow the owner to save on operating costs for the CHP while the PV

system is providing power.

5.2.5.2.

Battery bankAlthough the project will require batteries to be charged when running the CHP, to determine the

energy produced by the system, these will not be used to store the energy for use, but simply for

testing purposes. For an installed CHP system, battery banks are typically sized towards the load

for the dwelling, and store the energy from the CHP and complementing systems. Battery banks

store the electricity as DC current, and utilize an inverter to switch to AC current when there is a

draw on the batteries from the house. Battery banks are useful because they created a source of

instant energy for the dwelling rather than the delay from the generator having to start up. The

battery bank is also useful if other sources of energy are used, such as photovoltaics, which can

charge the batteries, and minimize the use of the generator when heating is not required.



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Manufacturing

Difficulty

1 2 3 4

E n g i n e e r i n g D i f f i c u l t y 1

2

3 3

4

Figure 12 Generator selection risk chart

6. Feasibility and Risk Assessment

6.1.

Engine Type

With the electrical power output demanded of this system being around 10kW, detailed evaluation

has shown that the reciprocating internal combustion engine is going to be the most cost effective

and efficient power plant. ICEs are the most common generator engine for systems below 50 kW

due mainly to the problems with blade heat dissipation with micro-turbines (ICF, 2008). With

regards to maintenance, ICEs demand more maintenance when compared to micro-turbines found

in a similar power range; however the small scale of the system required means that economically

speaking micro turbines are not a viable alternative.

It was decided that building the generator

from the ground up is outside of the scope of

the project. This greatly reduced the

manufacturing and design risks within this

section, as shown by the selection risk table

to the right. The risk selection table is a

graphical way of illustrating the

manufacturing vs. engineering difficulty of

the particular component. This allows the

group to better allocate time and resources

to more demanding areas of the CHP system. The primary risk remaining for the generator

selection is now a result of monetary consequences.

At this stage in the project is important to, at least in an approximate fashion, prove the feasibility

of the using an ICE through quantitative means. Despite the generator section of the system

yielding a low risk assessment in terms of design and manufacturing, it is the largest economical

risk and as such warrants serious investigation. As an example, by choosing a 525 cc engine to

power the generator set with an operational speed of 3600 RPM its can be shown that theaforementioned 10 kW electrical load and 20 kW base load can be satisfied.



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Some assumptions for this calculation are as follows:

Table 8 Generator set feasibility assumptions

Combustion Efficiency

ηc = 95%

Specific gas constant

Rair = 0.287 kJ/kg K

Atmospheric Temperature

To = 298 K

Volumetric Efficiency

ηv = 90%

Specific volume air

Cv-air = 0.821 kJ/kg K

Atmospheric Pressure

Po = 101 kPa

Mechanical Efficiency

([email protected]:1)

ηm = 85%

Specific pressure exhaust

Cp-ex = 1.214 kJ/kg K

Compression Ratio

Rc = 8.5 : 1

Thermal Efficiency

ηth = 25%

Specific heat ratio

k = 1.35

Heating value of Natural Gas

49770 kJ/kg

Electrical Motor Efficiency

ηem = 95%

Air fuel ratio of Natural Gas

17.2 : 1

*No energy lost through sound

or vibration.

*Assumptions provided by Pulkrabek 2011

Using the standard operating conditions of To = 298 K and Po = 101 kPa we will further assume that

T1 will experience around a 35 °C increase from T o due to intake preheating from the hot engine

block and intake manifold.

From here the total electrical energy available can be found by:

First we must find the heat energy input to the combustion engine from:

where,

and,

as a result,

Finally,



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Therefore at the output of the electric generator we have 3.32 kJ of energy available, to convert this

to a power output:

⁄ ⁄

The results of 9.95 kW shows that we are definitely in the range of the estimated 10 kW base load.

From this it then possible to find the heating energy available to the exhaust side heat exchangers,

defined by:

where

( )

⁄

⁄

Then to find the exhaust temperature (Tex) we need to find the temperatures at all point of the

combustion cycle.

where,

finally,



MECH 4015 Team #19



Manufacturing

Difficulty

1 2 3 4

E n g i n e e r i n

g D i f f i c u l t y 1

2

3 6

4

Figure 13 Control and starting system risk chart

6.4.

Fuel Type

The most common fuel for generator systems within the 10 kW range is gasoline. It is an

unattractive alternative for long term use given it has a limited shelf life because of its volatile

nature. Gasoline also has a high cost per unit of energy, and highly variable market price. Table 9

compares the price per GJ of energy of relevant fuel sources.

Table 9 Price per GJ comparison

Heritage Gas 2013 ( *Average National prices from 2012)

1 GJ of Natural gas $13.99

1 GJ of Fuel oil $27.93*

1 GJ of Propane $28.34*

1 GJ of Electricity $38.31*

1 GJ of Gasoline $35.66

Natural gas and propane are the primary fuel alternatives to this project. Each present great shelflife properties and market accessibility, however natural gas is economically more viable and

therefore will be used for calculations and estimates. Given the nature of the fuels, being in a gas

state with similar heating values, a spark ignition ICE can be easily retrofitted to seamlessly run off

either fuel. This has not been deemed a requirement for the system yet is feature that is

undergoing consideration.

6.5. Starting and Control System

The control system is designed to monitor and control the status of the CHP system. Electric start isa mandatory feature of the system. In order to allow the system to respond when an electric and or

thermal load is signalled the starting system must be connected to the

CHP control module. This communication will be achieved through an

arduino and a relay box that will activate the starter. It is a reliable

and simple system to implement making it a moderately low risk

design item, seen graphically below.



MECH 4015 Team #19



Manufacturing

Difficulty

1 2 3 4

E n g i n e

e r i n g D i f f i c u l t y 1

2 4

3

4

Figure 14 Structural enclosure risk chart

6.6.

Structural System

To allow for storage flexibility for indoor and outdoor environments an enclosed system is to be

considered for the CHP. With the engine being liquid cooled the circulation of air inside the

enclosure is no longer a concern making the enclosure a viable and preferred feature. Construction

and design of the enclosure and structure is a relatively simple endeavour and can be considered a

low risk event.

An enclosed system allows for;

Reduction of operating noise

Protection of components against elements

Improved aesthetics

Greater control over engine temperature

6.7. Heat Exchanger

The heat recovery section of the CHP system is broken down into the engine side and the exhaust

side heat exchangers. As explained in the system architecture section of this report the engine side

will employ a shell and coil heat exchanger to take advantage of the liquid to liquid interface. The

exhaust side will use tube bank heat exchanger to optimize the conduction from gas to a liquid. The

heat exchangers represent the largest area of risk in the project given their difficulty in design and

construction. However given that the resources made available specialize in this field of

engineering, our primary risk in the heat exchangers is in manufacturing; which is intended to be

mitigated through simple yet effective designs.

Manufacturing Difficulty

1 2 3 4


2

3

4 12

Figure 16 Engine heat exchanger risk chart

Manufacturing Difficulty

1 2 3 4


2

3 9

4

Figure 15 Exhaust heat exchanger risk chart



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7. Testing and Verification

7.1.

Methodology

The CHP system will initially be sized towards a specific application; in the case of this project, this

is a residential dwelling. Heating loads and electrical loads are determined to specify the size of the

generator required. Once a generator size is determined, the amount of heat recovery will be

determined, with the design of heat exchangers for the engine block and exhaust. The sizing of a PV

system will depend on the available space, and the battery bank is specified for the electrical load

that the dwelling requires. Once the system is created, it will be tested by measuring energy inputs

(fuel) and energy outputs (electricity and heat) to determine the systems overall efficiency.

7.2.

Preliminary testing

A CHP system is heavily dependent on input and output temperatures ranging from coolant

temperatures, exhaust temperature, and water inlet and outlet temperatures. To design the

necessary heat exchanging equipment, tests must be done to determine approximate figures that

can be expected, even though a generator has not yet been acquired.

7.2.1. Exhaust temperatures

Initially the testing completed will be theoretical; using computer models and programs to verify

methods of componentry sizing. The expected exhaust temperatures were calculated using an

engine output calculator created with Microsoft Excel. This calculator was used to take an engine

displacement and speed and output the volumetric flow rate and temperature of the exhaust, in

addition to the BHP produced. The accuracy of this calculator was tested using a Honda GX160;

which is a common single cylinder engine similar in design to what the generator will employ.

The calculator provided a linear approximation for the BHP over a specified RPM which was

compared to the actual horsepower curve of the engine, as seen in Figure 17. The results are nearly

identical, with a maximum difference of 4.3 %, which verifies the functionality of this power

calculator. The actual engine power curve of the Honda GX 160 is provided in Appendix B.



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Figure 17 Actual vs. Theoretical HP calculator

7.2.2. Engine temperatures

For the engine side heat exchanger, the temperatures of interest are the inlet and outlet

temperatures of the water and engine coolant. Water temperatures were determined based on the

typical water temperatures that would be found in a residential dwelling. A thermocouple was

used to determine the temperature of cold tap water and hot tap water where approximate values

of 10 °C and 55 °C were found respectively. Engine coolant temperatures are typically regulated

around 90 °C by thermostats. These temperature tent not to drop substantially through the

radiator, since having large temperature differences in coolant throughout the engine may causevarying amounts of thermal expansion in the materials. Taking this into account, an entering

coolant temperature of 85 °C was determined as a safe number. An infrared temperature gun was

used to verify these figures on an automobile engine, measuring the temperatures of the inlet and

outlet tubes of the radiator. Once the temperatures for the engine side heat exchanger were

determined, a spreadsheet was created to calculate the approximate size of a plate heat exchanger

was determined. This provides a general idea of the dimensions of the heat exchanger that will be

required for the system.

7.3.

Complete system testing and verification

Testing and verification of the complete assembly will be done with simulated conditions in a

controlled environment. We will be aiming to measure the heat and electrical output per unit fuel

consumed. This will yield the thermal efficiency and thus illustrate the net benefits of running the

CHP as compared to supplying heat and power independently.

0

1

2

3

4

5

6

2000 2200 2400 2600 2800 3000 3200 3400 3600

H o r s e p o w e r

RPM

Honda GX 160cc Actual vs. Theoretical HP

Calculated HP

Actual HP



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Electrically, the system will be tested by charging a battery bank which will simulate the load of the

specified house. Since electrical loads are satisfied via batteries in an actual CHP system, this will

provide an accurate testing load. At the battery bank we will be able to measure the current and

voltage provided. Through this the power is found by equation 1:

The thermal system will be tested by measuring the temperature and flow rate of the water

entering the heat exchanger and the temperature and flow rate of the water leaving the heat

exchanger. Then, by using equation 2, we can calculate the heat transferred to the water from the

waste heat.

The energy input will be measured from the mass flow of fuel into the engine. By having the mass

flow of the fuel we find equation 3 yields energy in.

where is the combustion efficiency of the combustion engine

and is the heating value of the fuel being used.

Finally, with the data collected, we can determine the overall thermal efficiency through equation 4

(Ugursal, 2005).

Figure 18 graphically illustrates what points in the system measurements will be taken to provide

the data required to solve for our overall efficiency. Only four primary measurement locations are

needed to fulfil equation 4:

1. Fuel flow into the engine

2. Cold water into the heat exchanger

3. Heat output from the heat exchanger

4.

Electrical output from the generator



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Figure 18 Testing process flow diagram



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8. Project Management Plan

8.1.

Organizational Responsibilities

The organizational responsibilities of the project have been broken down through a typical

hierarchical tree as seen in Figure 19. Dr. Allen heads the group with the four students all having an

equal level of responsibility in the project. Dr. Clifton Johnston is the program coordinator and has

a high degree of input on the structure of the deliverables and their deadlines.

Figure 19 Organizational Breakdown

8.2.

Work Breakdown Structure

The work break down structure is designed to improve the efficiency and reduce administrative

errors during the project. Many operations are time or sequence sensitive which requires early

planning and or assembly preparation. Having an overall breakdown of what needs to happen in

what order means that the project can progress in an orderly and predictable fashion.

Consequently this also makes status updates and progress reports far easier to produce.

Dr. Peter Allen

Justin Pruss Raymond Doiron Paul McKinnon Justin Wong



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Figure 20 Work breakdown structure



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8.3.

Schedule

Project schedule has been dictated by the course curriculum. For the fall term this outline has been,

and continues to be, followed diligently. The fall term schedule can be seen in Figure 21.

Figure 21 Fall Project Schedule

The winter term starts on January 6th 2014. Figure 22 loosely displays the expected schedule come

the winter semester. It is critical to complete all the required objectives for the fall semester to

ensure there are no delays starting the construction phase of the project.

Figure 22 Winter Project Schedule

25-Sep 2-Oct 9-Oct 16-Oct 23-Oct 30-Oct 6-Nov 13-Nov 20-Nov 27-Nov

Design Review

Conceptual Design Report

Embodiment Design Report

Interim Presentations

Logbooks

Web PagePeer Assessment

Fall Design Report

Fall Project Schedule

Start Date Duration

6-Jan 15-Jan 24-Jan 2-Feb 11-Feb 20-Feb 1-Mar 10-Mar 19-Mar 28-Mar 6-Apr

Winter Kickoff

Material Acquisition

Project Contruction

Design Iterations

Logbooks

Project Testing

Project Wrap-up

Final Presentations

Winter Project Schedule

Start Date Duration



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8.4.

Specialized Facilities and Resources

This viability of the project is greatly enhanced though having access to specialized facilities and

resources. Additionally these facilities are operated by highly skilled and experienced individuals.

These facilities and personnel are listed in Table 10 through Table 12.

Table 10 Project design and conceptualization facilities

Facilities Personnel

Thermodynamics LTD Dr. Peter Allen

Paul Sajko

Dalhousie Dr. Georgetta Bauer

Dr. Clifton Johnston

Table 11 Project construction facilities



Paul Sajko

Dalhousie Welding Albert Murphy

Angus MacPherson

Johnathon MacDonald

Mark MacDonald

Machining

Control Systems

Mechanical

Table 12 Project testing facilities



Paul Sajko

Dalhousie Control Systems Johnathon MacDonald

Peter Jones

Dr. Lukas Swan

Mark MacDonald

Electrical Integrity

Measurements

Engine Tuning



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9. Cost Estimates and Budget

Table 13 Budget breakdown

High Low AverageParts

Generator 12000 8600 10300Control System 300 200 250

Materials

Propane/Natural Gas 150 100 125Stainless Steel Sheets 1689 1206 1448Stainless Steel Piping 240 120 180Copper Tubing 300 150 225Insulation 200 100 150

Labour

Hours NA NA NA

Total 14879 10476 12678

This project has a relatively simple cost breakdown due to the fact that it has substantial student

and university components that eliminate a few categories. For example, the shop hours that

Thermodynamics Ltd. and Dalhousie University allot to the building of components such as the heat

exchangers are initially discounted until the market feasibility is considered. Another item that

does not need to be accounted for are the batteries in the battery bank, as they are already located

in Dr. Allen’s lab.

The team is in conversation with a few suppliers to acquire a new or used 15 kW generator that will

cost between $10,000 and $15,000. Right now, the team is waiting for quotes on generators from

two companies, Cummins Atlantic and DAC Industrial Engines Inc. that will give a better idea of the

overall impact on the budget. The other pre-existing components that will be purchased are those

for the control system. This system will consist of an Arduino board, a servomotor, a solenoid and

wiring. A portion of this system has already been acquired at a cost of $100 from robotshop.com.

The project requires the acquisition of raw material such as stainless steel Type 304, both in pipe

and sheet form. This is to build the heat exchangers, as well as the piping and encasement for the

whole unit. The Copper tubing is going to be used for the tube portion of the shell and coil heat



MECH 4015 Team #19



exchangers that is being manufactured to extract heat from the engine block coolant. The insulation

is going to be used on the inside of the case to keep as much heat inside as possible and to shield

people that may be working or around the unit. All of the raw materials have been sourced from

McMaster-Carr.com. However, alternative sources will be looked into. Hopefully the materials will

all be available locally to avoid shipping costs and also decrease the overall wait time from ordering

to possession.

Overall, the project could cost as little as $10,000 or in a worst-case scenario, which is mostly made

up by the generator, it could be as much as $15,000. Usually, a project will fall between the best and

worst case scenarios and in this case that would be around $12,500.



MECH 4015 Team #19



Bibliography

Bergman, Theodore and Adrienne S Lavine. (2011) Fundamentals of Heat and Mass Transfer . 7th

Edition: John Wiley and Sons.

Briggs and Stratton. (2013) Generators. Retrieved from

http://www.briggsandstratton.com/us/en/generators.

Caterpillar. (2007). Olympian LP & Natural Gas Generating Set. Specification Sheet. Retrieved from:

http://www.olympianpower.com/olympian-gas-gensets/60hz/global.

Cutler-Hammer. (2013) Residential Standby Generators: CHGEN10000I. Data sheet from:

www.EastoElectrical.com

Engineering Toolbox. (2013) Retrieved from http://www.engineeringtoolbox.com/.

Environmental Protection Agency. (2013) Efficiency Benefits. Retrieved from

http://www.epa.gov/chp/basic/efficiency.html.

Green Power Labs Inc. (2009) Solar Suitability Assessment of Dalhousie University. Retrieved from

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_Assessment.pdf.

Honda Equipment. (2013) Engines. Retrieved from

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ICF, Energy and Environmental Analysis. (2008). Technology Characterization: Microturbines.

Washington, DC: EPA Combined Heat and Power Partnership Program.

Injection Welding and Fab Inc. Dustin Metz , personal communication: November 26 2013.

Jayakumar, J.S. (2012). Helically Coiled Heat Exchangers, Heat Exchangers – Basic Design

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Machine Design. (2013) Retrieved from http://machinedesign.com/motorsdrives/selecting-dc-

brush-and-brushless-motors.



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Mcmaster-Carr. (2013) Retrieved from http://www.mcmaster.com/.

Paparone, M. (2009) Micro-CHP comes to North America – devices include gas-fired generators from

Honda. Cogeneration and On Site Power Production, Volume 10, Issue 3. Retrieved

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Patil, R.K., Shende, B.W., & Ghosh, P.K. (1982) Designing and Helical Coil Heat Exchanger. Retrieved

from: http://www.gandipsbio.com/Articles/Papers/3_Helical_Coil_Heat%20Exgr_1982.pdf.

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industrial-energy-efficiency.

Pulkrabek, W.W. (2004) Engineering Fundamentals of the Internal Combustion Engine. Upper Saddle

River, NJ. Pearson Prentice Hall.

Stewart Components. (2007). Advanced Cooling System Basics. Retrieved from:

http://www.stewartcomponents.com/tech_tips/Tech_Tips_6.htm

Subramanian, Shankar R. Shell and Tube Heat Exchangers. No Date.

Sun Power Corp. (2013) X-Series Solar Panels. Retrieved fromhttp://us.sunpowercorp.com/homes/products-services/solar-panels/x-series/.

Thulukkanam K. (2013). Heat Exchanger Design Handbook . 2nd Edition. Boca Raton, FL. Taylor

Francis Group

Ugursal, I, Knight, D. (2005) Residential Cogeneration Systems: A review of the Current

Technologies. Department of Natural Resources Canada.



MECH 4015 Team #19



Bibliography – CAD Drawings

Briggs & Stratton 10HP Engine, Diego Montero, 28 Sep 15:29 , https://grabcad.com/library/briggs-

and-stratton-10hp-engine-for-baja-sae

2 hp Electric Motor, Doug Minnear, 15 Apr 23:31, https://grabcad.com/library/2-hp-motor

Radiator, Rohit Mitra, 23 Aug 18:52, https://grabcad.com/library/motorcycle-radiator

Radiator Fan, shawn cooke, 10 Jan 21:48, https://grabcad.com/library/oil-cooler-fan

Arduino Uno, Vlad, 21 Jan 03:45 , https://grabcad.com/library/arduino-uno-simple

Arduino Box Enclosure, Jared, 07 May 03:42, https://grabcad.com/library/arduino-simple-box-

enclosure

Bosch 12V Battery, SG, 17 Oct 06:54, https://grabcad.com/library/electric-vehicle-parts-bosch-

battery-12v

Solar Panel, Zeljko Fabijanic, 03 Jan 08:23, https://grabcad.com/library/solar-panel--3

Electrical Box, Mech Amine, 27 Apr 00:55, https://grabcad.com/library/armoire-electrique-electric-

cabinet

Brazed Plate Heat Exchanger, Sergey_96, 06 Nov 17:33 , https://grabcad.com/library/b3-052-20-1



MECH 4015 Team #19



Appendix A Potential Loading Scenarios

Loads Factors

Scenario Electrical Thermal Season Supplementary

Input

House

Occupancy

Resulting

Generator Status

1 Peak Peak Winter None Max On2 Peak Partial Spring/Fall None Max On

Partial Max On

3 Peak None Summer None Max On

Partial Max On

4 Partial Peak Winter None Partial On

Partial Max On

5 Partial Partial Spring/Fall None Partial On

Partial Max Off

6 Partial None Summer None Partial On

Partial Max Off 7 None Partial Spring/Fall Full Partial Off

Full Max On

8 None None Summer Full Partial Off

Full Max Off



MECH 4015 Team #19



Appendix B Honda GX 160cc Power Curve



MECH 4015 Team #19



Appendix C Theoretical Engine Exhaust Characteristics



MECH 4015 Team #19



Appendix D Shell and Coil Heat Exchanger Design

Tc,i 283 K Water 305.5 K E.G. 352.5 K

Tc,o 328 K ρ 994.4 kg/m3 ρ 1024.5 kg/m3

Th,i 355 K cp 4069.2 J/kg K cp 3416.3 J/kg KTh,o 350 K µ 7.37E-04 Ns/m2 µ 9.08E-04 Ns/m2

ΔTc 45 K ν 7.41E-07 m2/s ν 8.86E-07 m2/s

ΔTh 5 K k 0.62283 W/m K k 0.46451 W/m K

ΔTlm 44.0 K Pr 4.8175 Pr 6.678

(Assuming 50% solution)

Do 9.59E-02 m Coil D 0.08 m Manu. & Name:

Di 6.41E-02 m Pitch 2.39E-02 m Qh 0.00075 m3/s Qc 7.21E-05 m3/s

Dh 0.02 m Di 1.38E-02 m mh 0.768375 kg/s mc 0.071677 kg/s

A 2.00E-03 m2 Do 1.59E-02 m Th,i 355 K Tc,i 283 K

t 2.10E-03 m Th,o 350 K Tc,o 328 K

Ai 1.50E-04 m2 ΔTh 5 K ΔTc 45 K

L one coil 0.501893 m E.C. Ht 13125 WA one coil 2.51E-02 m2

m 0.768375 kg/s m 0.071677 kg/s

Q 0.00075 m3/s Q 7E-05 m3/s

u 3.75E-01 m/s u 4.68E-01 m/s

ReD 6.73E+03 ReD 8.71E+03

TURBULENT FLOW TURBULENT FLOW

NuD* 6.10E+01 NuD 61.19115

h 1.78E+03 W/m2 K h 2.76E+03 W/m2 K

L 2.62E-01 m f 0.032714

f 0.034883 L 5.51E+00 m

Δp

32.97569 Pa Δp

1.42E+03 Pa

U 1083.049 W/m2 K

A 0.275351 m2

coils 1.10E+01

q 13125

Th,o 350

mc 0.071677 kg/s

mh 0.768375 kg/s u 3.75E-01 m/s u 4.68E-01 m/s

q 13125.06 W ReD 6.73E+03 ReD 8.71E+03

Ch 2625 W/K NuD 6.10E+01 NuD 61.19139

Cc 291.668 W/K h 1.78E+03 W/m2 K h 2.76E+03 W/m2 K

Cmin 291.668 W/Kqmax 21000.1 W L 2.67E-01 m L 5.63E+00 m

Ɛ 0.625 f 0.034883 f 0.032714

Cr 0.111112 Δp 33.65257 Δp 1.45E+03

NTU 1.043447

U 1083.05 W/m2 K

A 0.281003 m2

coils 1.12E+01

q 13394.43

Th,o 349. 8974

Shell Side

Log Mean Temp Diff Method

Fluid Temperatures

Generator Information

Caterpillar Olympian 15 kW

Cold Fluid Hot Fluid

Shell Side Tube Side (1/2" copper tube)

Tube SideShell Side

NTU Method (variable water flow rate)

Tube Side



MECH 4015 Team #19


Appendix E CFD Model of Coolant through Shell and Coil Heat Exchanger

fall design report team19

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