solar thermal storage using phase change materials

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Acknowledgements

We would like to thank the following people who gave their time, assistance andconsideration during this training period.

Firstly, we are extremely grateful to our supervisor Dr. Kenneth Ip who has provided support,advice and constructive comments throughout.

We would also like to thank Mr. Jonathan Gates for his help and the continuous supply ofinformation during all this period.

Finally, thanks are also due to Dr. Andrew Miller for his kindness and the good times spent inRouen, and to Ms Michele Terrier who made possible this exchange with the University ofBrighton.

Page

Acknowledgements 1

Content 2

Abstract 4

1. Introduction 5

2. Solar Heating 71. Solar energy 72. Solar collectors 83. Energy transfer 15

3. Phase Change Materials 161. Energy storage: an introduction 162. Organic compounds 203. Inorganic compounds 214. Eutectics 22

4. System design 23

1. Description of the system 232. System dimension and layout 25

1. Schematic of the Laboratory 252. Layout of the model 263. Isolation box 28
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.

1. Components for the system 302. Components for the measurement 34

4. PCM and solar panel selection 371. PCM selection 372. Solar panel selection 39

Page

5. Heat transfer process 401. Heat transfer for a pipe 40

1. Heat loss along a pipe 402. Cylinder in a cross flow 42

2. Radial heat transfer 433. Heat transfer during the phase change 464. Equation for the solar panel 47

6. Experimental set-up 48

1. Parameters to be measured 482. Measurement procedure 503. Break down of costs for the system 514. Be careful about 52

7. Conclusion 54

Appendix 55

Glossary 67

References 68Bibliography 69

Abstract

The aim of this project was to determine the experimental set-up for the measurement

of thermal storage system using phase change materials.

The report covers solar panels and phase change materials and the operating principles

behind them.

A solar thermal storage system using phase change material is proposed and background

heat transfer equations and total cost established.

A method of experimental measurement is proposed in order to measure the performance

of the proposed system.


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.

During our second year in thermal engineering at the IUT (University Institute of Technology)situated in Rouen, Normandy, are required to enter into a period of training. The duration ofthis period is ten weeks, and is usually done in a company or industry. However we chose todo this period in a university in England, in order to improve our English and apply the theorylearnt at the IUT. The institute that we chose was the University of Brighton, which is situated

in the south of England, in East-Sussex.

This university, was last year declared "University of the year" by the Sunday Times.

The University of Brighton offers courses in the following areas:

engineeringscience and mathematicsbuilt environmentcomputing and informationbusiness and management

teacher educationhealthsocial scienceart and design

The University has four different sites:

MoulsecoombGrand ParadeFalmer

Eastbourne

The department that we carried out our period of training in was the School of theEnvironment situated in the Cockcroft building, at the Moulsecoomb site under Dr. KennethIps supervision and in collaboration with Jonathan Gates, a MPhil/PhD student.

The aim of our studies was to propose an experimental set-up for the measurement ofthermal performance of a solar thermal storage system.

An effective solar thermal storage system must form an integral part of a solar heating systemfor without this maximum utilisation of solar energy is not possible. Thermal storage can alsoaddress the problem in trying to match supply to demand were maximum solar availabilityoccurs during the day, but maximum demand occurs at times when there is a little if any solaravailability.

This project forms part of a current research to develop and analyse the performance of sucha system for use in domestic buildings.

The report is organised into chapters which correspond with the objectives of the project.

The first part of the report covers solar energy, the different ways to store energy, and PhaseChange Materials (PCMs).

The second part covers system design including description of the system, identification ofcomponents, PCM selection, all of which should allow a model of the system to be built.


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The third part details the heat transfer equations, for each part of the system.

The final part of the report details the experimental set-up, which describes the parameters tobe measured, the measurement procedure and the cost of the system.

Keywords: PCM, solar panel, latent heat storage, heat transfer energy, latent energy.

II. Solar Heating

2.1. Solar Energy

At the 1992 conference on climate change, the United Nations Inter-governmental panel

concluded that a 60% reduction in the use of fossil fuel would have to be made in order to

freeze the level of CO2 emissions by the year 2005 [1]. This has a tremendous implication onthe way in which fuel is currently being used, placing greater emphasis on the use ofalternative, renewable energy sources. This will have a large impact on the way buildings areoperated as currently they account for over 50% of fuel consumption, with heating andlighting residential buildings responsible for 60% of emissions [1].

Solar power has enormous potential for use in residential buildings for approximately 30000times as much solar energy reaches the earth than is actually needed to meet humandemand [2]. It is also a clean source of energy in that it does not produce any CO 2 and it is

totally renewable.

However there are several major problems with harvesting solar energy; its availability isunpredictable, intermittent and is often subject to interruptions due to changes in weather.Due to this and the fact that for approximately for half of the 8760 hours per year any locationis in darkness [3], a form of thermal storage is required to match supply with demand.

2.2. Solar collectors

A solar collector is made up of the following elements:

An opaque body which absorbs the solar radiation by getting overheated,

A thermal heat transfer fluid,

Thermal insulation (back and sides)

A transparent cover (fore face exhibited to the radiation)

A heat exchanger called absorber plate

In each collection device, the principle that is usually used is to expose a dark surface to

solar radiation so that the radiation is absorbed then, a part of the radiation absorbed in this


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way s transm tte to a u : a r or water y means o a eat exc anger.

Concerning this heat exchanger, all solar energy systems using indirect water heating requireone or more exchangers; heat exchangers influence the effectiveness with which collectedenergy is made available in domestic water.

They also separate and protect the potable water supply from contamination when non-potable heat transfer fluids are used.

Like transport fluid selection, absorber plate selection considers thermal performance, costeffectiveness, reliability and safety, and the following characteristics:

Heat exchange effectiveness

Pressure drop, operating power, and flow rate

Physical design, design pressure, configuration, size, materials, and location in the system

Cost and availability

Thermal compatibility with system design parameters such as operating temperatures, flow

rate, and fluid thermal properties.

Actually, there are two main different sorts of collectors:

Flat-plate and evacuated-tube collectors.

Flat-plate collectors

A flat-plate collector is the most important type of solar collector since it does not

require a lot of maintenance and is really simple to design. Moreover, the flat-plate collector

can be used for applications where temperatures are set between 40 C and 100 C. Whichmake it suitable for space heating applications.

A schematic diagram of a liquid flat-plate collector is shown in Fig.1.

A flat-plate collector consists of an absorber plate on which the radiation of the sun falls after

having come through one transparent cover made of plastic or glass either single or double-glazed.

The absorbed radiation is transferred to a liquid via the absorber plate and it is this energygain which is the most useful.


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The remaining part of the radiation absorbed in the plate is lost by convection to thesurroundings, and by conduction through the back and edges.

The transparent cover helps in reducing the losses by convection and a selective coating canreduce the amount of lost to the surroundings.

The liquid most commonly used is water, although oil can be used.

Evacuated-tube collectors

The evacuated-tube collector is the other form of solar collector

These are typically more efficient at higher temperatures than flat-plate collectors. In anevacuated-tube collector, sunlight enters through the outer glass tube and strikes the

absorber, where the energy is converted to heat. The heat is transferred to the liquid flowingthrough the absorber. The collector consists of rows of parallel transparent glass tubes, eachof which contains an absorber covered with a selective coating. The absorber typically is oftin-tube design, although cylindrical absorbers also are used.

Evacuated-tube collectors are generally more efficient on an all year round basis as they canstill operate under cloudy conditions, however they are considerably more expensive thanflat-plate collectors -around 80%- and if the vacuum seal fails then they become inefficient.

A solar selective coating absorbs the solar radiation and converts it into thermal energy that istransported from inside the inner tube to an application.

Flat-plate collectors for heating air

However, there is also another sort of collector, whose construction is rather similar to the oneof a liquid flat-plate; this is the conventional flat-plate collector for heating air. The only

difference in its construction concerns the passages through which the air flows.A schematic diagram of such one collector is shown below in Fig.3.


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,to store, it needs to use either a rock-bed or water for storage which again takes up space.

A thermal application: water heating

Of all the solar thermal applications, solar hot water heating is the most popular and may be

the most economically viable.

A diagram of a simple natural circulation system is shown in Fig.4.

The two main elements of this system are the liquid flat-plate collector and the storage tankthat is located above the level of the collector.

When the water in the collector is heated by solar energy, it flows automatically to the top ofthe water tank and it is replaced there by cold water from the bottom of the tank. Hot water

for use is withdrawn from the top of the tank, and cold water enters automatically at thebottom.

The main disadvantage with a thermosiphon system is that the storage vessel needs to belocated higher than the collector which means the collector may have to be sighted on theground or on a porchroof.

Finally, in Fig.5 is shown a pumped system because this is one as this, that we will use.


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When designing a solar heating system, it is important to consider the local climaticconditions. The most important climate variable(s) is (are) the solar irradiation (and the localambient temperature).

The plane where we will install our panel is inclined around 30 (what is the typical inclinationfor solar collector in the United Kingdom).

The solar irradiation on such an inclined plane varies about 950 kWh/m2 per year in the North

of the UK (Scotland) to about 1250 kWh/m2 per year in the South West (see Fig.6).

Fig.6 Variations in annual mean values of solar irradiation on a 30 inclined plane in the UK

(kWh/m2)

(Source European Solar Radiation Atlas-1984)

Concerning the design of active solar system for the UK, there is also an important point, it isthe fact that the monthly solar irradiation varies between the summer and the winter months.

For an installation in Brighton, the seasonal variations for a surface in the South of Englandare shown below in Fig.7


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Fig.7 Monthly distribution of annual solar irradiation received at 30 South in the South of England

(Source European Solar Radiation Atlas-1984)

2.3. Energy transfer

The energy collected by the solar collector is transferred to the heat transfer medium via theabsorber plate. This heat is transferred to a storage tank or vessel.

This transfer occurs either by free circulation or by forced circulation

Transfer by water free circulation.

In these installations, the transfer of energy is based on the difference in density between hotand cold water.

Water entering at bottom of the collector is heated by the sun which reduces its density andcauses it to expand it to rise to the storage tank which must be situated at least 60 cm abovethe collector.

Due to thermal stratification, hot water remains at the bottom of the tank, from which the solar

collector is fed.

Transfer by forced circulation.

In addiction to the elements used in the previous system, this system uses a circulation pumpdriven by a temperature regulation.

The role of the circulation pump is to enable a faster transfer of the heat absorbed by theheat transfer fluid from the solar collector.

The utilisation of this pump also enables the system to be shut down if the water in collectoris not hotter than that inside the tank.


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The role of the regulating thermostat is to compare the two temperatures (at the solar panelexit and in the storage tank) and to drive the pump solely when the first temperature is higher

than the second one (usually 5-10 C). In practice, the regulators available on the marketenable the user to independently set the temperature difference.

III. Phase Change Materials

3.1. Energy storage: an introduction

Energy storage is a fundamental requirement of all solar energy systems.

Storage can either be thermal or chemical.

Thermal storage can either take the form of sensible heat storage where energy is stored byraising the temperature of a storage medium, for instance water or rock, or latent heat storagewhere energy is stored by altering the physical state of the storage medium, which can besolid-solid, liquid-gas or solid-liquid. The most common form of sensible heat storage indwellings is the incorporation of thermal mass in a buildings structure to act as a heat store.

However there are several disadvantages with sensible heat storage; it is often difficult tojudge the correct thermal mass required for space heating requirements and energy cannotbe stored or released at a constant temperature. This method of storage is also inefficient as

it takes less energy to raise the temperature of a material than it requires to change a solid orcrystalline structure into a liquid.

Consequently to store the same amount of energy, significantly larger quantities of storagemedium are required for sensible heat stores in comparison to latent heat stores. This isillustrated by the fact that the sensible heat capacity of concrete is approximately 1.0 kJ/kg[4], compared with calcium chlorine, which during phase transition, can store or release 190kJ/kg [5]. Due to the large volume of material required, sensible heat storage is not suitablefor retrofit applications and does not conform to the current trend for lightweight structures.

Furthermore, these systems take up a lot of space and have weight penalties which can havemajor cost implications in commercial property.

The use of latent heat storage is ideally suited where space is at a premium, such asrefurbishments as larger amounts of energy can be stored per unit volume in comparisonwith sensible heat storage, which results in large space savings.

Another major advantage with latent heat storage is that heat is stored under isothermalconditions, which means they can deliver or store energy at a constant temperature. The use

of latent heat storage is especially suited to the storage of solar energy where it can result inhigh solar collection efficiency, which can mean that solar collector area can be reduced by

30% [5].


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So as to explain what a Phase Change Material is, we must show the example of water, themost simple and used of them.

Alternatively, water in a liquid state cooled to the point of crystallisation (0 C) will dischargeheat.

This process is similar at the other phase (100 C) with boiling resulting in heat storage andcondensing resulting in heat discharge.

Latent heat storage and discharge for water at 100 C is termed latent heat of vaporisation

and heat storage and discharge at 0 C is termed latent heat of fusion, this is that latent heatwhich will only be considered during our study.

The principle of latent heat storage using phase change materials (PCMs) can beincorporated into a thermal storage system suitable for use in dwellings, where roof-mountedsolar panels are used to collect the available solar energy during the day, which is thenstored in the PCM for later use.

The water phase changes are shown in the schematic diagram in Fig.6

Fig.6 Water Phase changes

By comparing the values of steel, copper, water and a typical PCM compound called sodium


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su p ate; we can see t at stee an copper ex t t e owest eat o us on or suc gmelting points.

Material Melting point ( C) Latent heat (kJ/kg)

Density (kg/m3)

Steel 1400 247 7800

Copper 1086 206 8900

Ice 0 335 917

Sodium sulphate 32 252 1495

Characteristics of steel, copper, ice and sodium sulphate

(Source IHVE Guide. Unit and miscellaneous data)

By measuring density values we can also see that larger volumes of space are required.

Although ice has the optimum set of readings, the melting temperature is far too low to beuseful as a means of heat storage.

It is clear that the PCM exhibits the optimum qualities, it provides a minimal amount of volumefor its heat of fusion as well as having a low melting point.

Thats why PCM can be used as heat storage.

Now, we have to identify the required PCM to integrate in our proposed heating system.

This chapter reviews the characteristics of suitable PCMs for use in buildings and themethods of storage and control.

There are several types of PCMs but the three most common groups of PCMs are organiccompounds, inorganic compounds and eutectics.

3.2. Organic compounds


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in relation to the amount of carbon atoms it possesses. Pure paraffins contain 14-40 C-atoms,whereas paraffin waxes contain 8-15 C-atoms [6]. Organic PCMs offer several advantages inthat they possess a wide range of melting points, are non toxic, non corrosive, nonhygroscopic, chemically stable, compatible with most building materials, have a high latentheat per unit weight, melt congruently and most importantly exhibit negligible supercoolingwhich has plagued some inorganic compounds [5].

Some disadvantages of organic PCMs are; high cost which has led some researchers toinvestigate technical grade organic [7], low density, and low thermal conductivity incomparison to inorganic compounds, although this can be addressed by the addition of afiller with a high thermal conductivity or the use of aluminium honeycombs or matrixes [8].

They are also subject to substantial changes in volume upon melting, which can result in thematerial detaching from the sides of its container when it freezes, which can affect the heattransfer process. Flammability is often sighted as a potential disadvantage with organicPCMs, however some authors argue that their low vapour pressure presents little risk of fire,and they exhibit unstable characteristics notably large volume changes during liquefaction

and solidification and low thermal conductivity.

Name Melting point ( C) Heat of fusion

(kJ/kg)

Octadecane 28 244

Eicosane 36.7 247

Paraffin 116 45-48 210

Paraffin 6403 62-64 189

Organic Phase Change Materials

(Source- CIBS Guide C3 Heat transfer(1976))

3.3. Inorganic Compounds

These mainly consist of chemicals such as hydroxides or oxides, which have been diluted inan acid solution and are termed as salt hydrates or molten salt. The advantages that salthydrates offer are; low cost in comparison to organic PCMs, they have a high latent heat perunit mass and volume, they possess a high thermal conductivity compared to organic

compounds and offer a wide range of melting points from 7-117 C [9]. However, they canalso suffer from loss of water when subjected to long-term thermal cycling due to vapourpressure, although the use of airtight containerisation can prevent this.

Problems with corrosion have also been experienced with salt hydrates. The major drawbackwith salt h drates is that the can de rade over time due to a rocess known as


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decomposition. This is where the PCM melts incongruently and produces two separate parts,an aqueous phase and a solid phase, which possesses different densities, consequently thedenser solid phase settles at the bottom of the container and this process is irreversible.

Many salt hydrates exhibit this weakness. Attempts at addressing this problem have centredon using thickening agents with varying degrees of success. However Merks observed thatwhilst Glaubers salt thickened with attapulgite clay withstood thermal cycling better than anun-thickened, solution its thermal storage capacity still declined over time [5].

However, the problem with this sort of compounds occurs from repeated phase changecycles during solidification, the salt hydrates melt incongruently. This result is in a compoundof a lower hydrate of the same salt [3]. That is to say that the original compound is no longerthe same and a lower heat of fusion results.


(kJ/kg)

Sodium sulphate decahydrate 32.4 252

Calcium chloride hexahydrate 27-29.7 170

Zinc nitrate hexahydrate 36 147

Inorganic Phase Change Materials

3.4. Eutectics

A eutectic PCM is a combination of two or more compounds of either organic, inorganic orboth which may have a more interesting melting point to their individual and separatecompounds. They behave themselves as salt hydrates.

The main problem with these compounds is the cost, actually some two or three times greaterthan organic or inorganic.


(kJ/kg)

Palmatic acid (organic) 63 187

Mystiric acid (inorganic) 54 187

Stearic acid (organic/inorganic) 70 203

Eutectics Phase Change Materials


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(Source- CIBS Guide C3 Heat transfer(1976))

Phase transition temperature

It is essential that the output of heating system is not less than the overall temperaturerequired to melt the PCM permitting the desired heat transfer to take place. Thosecompounds with the lowest congruent melting points are therefore more desirable.

IV. System design

4.1. Description of the system

This project proposes to realise a model of a heating system. The heat in this system isobtained by a solar panel and the storage of this heat will be done in phase change material,sandwiched inside two pipes, surrounding a water pipe.

In the end, the model will be install in a laboratory, inside the university. The laboratory is for

the moment used for another field of studies. Before all we had to make the measurement ofthe size of the laboratory, in order to propose a schematic drawing of a possible model.

The pictures below show the laboratory, in its current condition.


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Above, picture of the laboratory, one of the entrances.

Above, picture of the laboratory, other view.

The photo below, is a photo of the roof, where the solar panel will be installed.


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4.2.System dimension and layout

4.2.1. Laboratorys schema

For this part we have taken the measures of the room size and made a schema of helaboratory; in order to after make the drawings of the implantation of the model inside thelaboratorys room.

4.2.2. Layout of the model


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4.2.3. Isolation box

Monitoring the temperature of the internal space is vital in the case of space heating. In ourcase, the model we propose will be install in a room inside a laboratory of the university. Thisroom has big dimension, and those dimensions could have an influence on the parameterswe would like to measure. Indeed, if the size of the room is too big it can happen that thetemperature is not uniform and then it exists a temperature gradient inside the room.Furthermore, we can not measure easily the airflow, which flows cross the PCM pipes. So tomeasure the real impact of the PCM, and the heat exchanged, we need to have a less bigroom around the PCM pipes.

In order to do that, we propose to build a sort of box around the system. This box will beinsulated, so as to have a room isolate from the rest of the laboratorys room.

We propose to install this insulated box like in the schema below.


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We propose also, a simply way to build this box, but this is just a guide to do it.

First built a frame in wood, to have the skeleton of the room. After that, put plasterboards atthe outside surface of the wood frame, screwed on the post of the frame.

Then, put insulation behind the plaster boards, inside and between the frame

Posts. Finally put the rest of the plasterboards inside the room, screwed on the posts of theframe. You have a room, insulate, to protect your system from the outside, and thelaboratorys room.

4.3. Identification of components

4.3.1.Components for the system

Choice of the pipes

For the most important part of the system, we can use a copper pipe for the water flow. Butfor the size of the pipes we must take care about the implantation of the system, indeed itcould be installed under the floor, so the pipes could pass through some joists. The size ofthe pipes in this case is regulated, the maximal diameter for the holes made inside the joistsis 0.25 times the width of the joist.

[appendix A.1]

For the Phase Change Material we need nine meters of plastic pipes. We take a nominaldiameter of 36mm (UPVC Class E), to have a mean internal diameter of 32mm. As the pipesof PCM will be the bigger ones, a diameter of 36 mm leads to have a joist with a minimumwidth of 150 mm. Which is not too big and could be correct for a lots of situations. [appendixB.1]

We take fifty meters of copper pipes, with a nominal diameter of 15mm, That is to say a meaninternal diameter of 14mm.

For the pipes around the Phase Change Material we need to take plastic pipes, because of

the corrosion of the copper by the Phase Change Material chosen. Actually, the PCM in ourcase is Salt Hydrate, which are efficient but corrosive to the plastic. The length of plasticpipes we need is nine meters, with a nominal diameter of 15mm, to have a mean internaldiameter of 11mm for this part. [appendix B.1]


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Choice of the valves

To isolate the system, if it need, we can use valves.

The valves we chose are Gate valves and have

a diameter of 15mm. [appendix B.1]

Choice of the insulation

Pipes or ducts need not to be insulated if they contribute to the useful heat requirement of aroom or space. In this project, the aim is to give to the PCM the largest possible quantities oheat, so we need to insulate the pipes to avoid the heat loss by the water, while it circulatesinside the pipes.

We insulate the water pipes, with an insulation of 15mm for the diameter and 25mm for thethickness.

[appendix B.1]

Choice of the pump

We need a pump to make the water circulate, with a flow of one meter per second up to fivemeters per second. However we are limited for the choice, indeed we do not need a heavypump if we consider the size of the water pipe, but the problem there is that the water needs

to go up to 12 m easily. So we need to take a pump with a big head capacity.

The choice of pump was made after consulting manufacturer catalogues.

[appendix B.2]


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Applications

Water circulation in commercial heating and air conditioning systems.

Options

Single or twin head.

Temperature range:

Pressure rating:

Pump connections: -10 to +130C

6 Bar

1.25"BSP to 80mm

Choice of the fan

We need to known the size of the isolation room in the laboratory to make the choice of thefans. By calculation, we found eighty cubic meters. We take a fan, which can deliver a volumeof air, equal to two hundred cubic meters per hour with a velocity, which can change. Weplace the fan as the schema below shows it.

The choice of fan was made after consulting manufacturer catalogues.

[appendix B.3]


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Fan CC-CCI

The CCI fans are acoustically insulated by a double internal wall made up of a double sheet

perforated metal structure full of 50 mm of mineral wool; by the way, they are one of thequietest fans in the market.

The four main characteristics of those fans are:

Their optimal curve, in spite of a minimal electric consumption;Their really low noise level, particularly for the CCI;Their compact size;Theyre easy installation and utilisation, then maintenance, thanks to the assembly of thetank, the doors and the power driven turbine group.

The CC-CCI are compliant.

4.3.2 Components for the measurement

Choice of the thermocouples

We need thermocouples to make the measurement of the temperature, at different places. Therange of temperature we have is 20C (just in case) up to 100C. So we can take athermocouple type T which have a range of 250C to 395C.

The choice of thermocouples was made after consulting manufacturer catalogues.

[appendix B.4]

Choice of the data logger


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We need a device to store and make the acquisition of the data obtained by the measures, adata logger is the more useful device to make this acquisition.

We have chosen the following data logger, because it is expendable, and it offers a lot odifferent input.

See appendix B.5

Expandable Data Logger

HHP34970A

Up to 120 analogue inputScan rates up to 250 channels/sMeasures 11 different signal types6 1/2 digit readings (22 bits) with up to 0.005% accuracy (for 1 volt range)Can hold up to three expansion

modules internally

Scaling and alarms available on

each channel

Stand-alone configurationNon-volatile memory for 50,000

readings and five instrument

configurations

Digital I/O, analogue output, and relay

outputs available

Intuitive front panel

Task-oriented self guiding menusBattery-backed real-time clock for

pacing scans and timestamping

readings

Software included for analysis and display of readingsGPIB and RS-232 interfaceThree year warranty

Universal input channels

In all, the HP 34970A can measure and convert 11 different types of input signals which

eliminates the need for expensive external signal conditioning.These signal types are:

temperature with thermocouples, RTDs, and thermistors B, E, J, K, N, R, S, T


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DC and AC voltage 100mV, 1V, 10V, 100V, 300V

2 and 4 wire resistance 10W to 100MW in 7 decades

frequency and period 5Hz, 10Hz, 40Hz, 300kHz

DC and AC current 10mA, 100mA, 1A

COMMON SPECIFICATIONS

DC CHARACTERISTICS

Offset voltage `


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requency z- z .

DC current 100mA 0.050 + 0.005

(34901A only)

True RMS AC current 1A 0.10 + 0.04

(34901A only)

Thermocouple Type k 1C

Amplicon Liveline Ltd.

Centenary Industrial Estate

Hollingdean Road

Brighton BN2 4AW

United Kingdom.Tel: - 01273 570220 & Fax: - 01273 570215

Choice of the water flowmeter

We need a water flowmeter, in order to have the value of the water flow inside the waterpipes. The value of the water flow is used in the equations to have the amount of the heatexchanged inside the water pipes. So we take a flowmeter which can be fixed on a pipe o

13mm for the diameter.

The choice of water flowmeter was made after consulting manufacturer catalogues.

[appendix B.6]

Choice of the air flowmeter

We need an air flowmeter, to measure the airflow passing cross the PCM pipes. Indeed tocalculate the heat took from the PCM, we need the temperature at inlet and outlet of theinsulated room, and the airflow.

The choice of air flowmeter was made after consulting manufacturers catalogues.

[appendix B.7]

4.4. PCM and solar panel selection


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4.4.1 PCM selection

Latent heat of fusion per unit of volume

of selected phase change materials

Organic compounds:

a. Paraffin 6403b. Octadecane

Eutectics:

c. Myristic acidd. Palmitic acid

e. Stearic acid

Inorganic compounds:

f. Calcium chloride hexahydrateg. Sodium sulphate decahydrateh. Zinc nitrate decahydrate

Density

High density is important because more heat can be stored in a given volume.

However, density increase is often accompanied by a decrease in heat of fusion since thesubstance becomes self-insulated.


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Safety

The material must not be dangerous, flammable or toxic, and must be disposable.

PCMPhase

TransitionTemperature

Heatof

fusionDensity Toxicity Flammability Cost Scores

Calciumchloride

3 3 7 3 3 3 53 /17

Sodiumsulphate

3 3 7 7 3 3 43 /27

Zinc nitrate 3 7 7 3 3 3 43 /27

Octadecane 3 3 3 7 7 3 43 /27

Eisocane 7 3 3 7 7 3 33 /37

Paraffin

1167 3 3 7 7 3 33 /37

Paraffin

6403 7 7 3 3 3 7 33 /37

Myristicacid

7 7 3 3 7 7 23 /47

Palmaticacid

7 7 3 7 7 7 13 /57

Stearic acid 7 7 3 7 7 7 13 /57

By reading this table and seeing the chart, it appears that the best Phase Change Material tochoose is the Calcium chloride hexahydrate.

Actually, it is a good compromise between a low Phase transition temperature and such animportant latent heat of fusion, moreover, there is absolutely no danger in using this PCM andit is one of the cheapest.

4.4.2 Solar panel selection

A Flat-plate collector was selected for the following reasons:


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They are considerably cheaper than evacuated tube collectors.If a flat-plate collector with a selective coating is used then these can have efficienciesapproaching that of evacuated tube collectors (manufacturerFilsol Ltd(Oxide ofChromium, Iron and Nickel)).They are most suited to temperatures up to 100 C so which is well within the parametersneeded for space heating.

V. Heat transfer process

We have to take into consideration for the heat transfer, that the transfers are not the same foreach situation. That is why this chapter is divided into different parts describing the differentsituations we have in this project.

5.1. Heat transfer for a pipe

The first part describes the heat transfer for a pipe in two situations, firstly the heat loss alongthe pipe when the water circulates inside the tube.

And then the situation, when a fan is blowing air on the pipe, for recovering the heattransmitted by the pipe. In our case, the heat is recovered from the PCM.

5.1.1. Heat loss along the length of a pipe

Assumptions:

Steady-state conditions exist.Radiation exchange between the pipe and the room is between a small surface in a muchlarger room.

The heat loss from the pipe is by convection to the room air and by radiation exchange with


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t e wa s.

Hence,

The heat loss per unit of pipe length is then,

The convection coefficient may be obtained thanks to:

where,

with,

See appendix C, table C.1 for the values ofn, a, b to obtain Pr and Gr.

5.1.2. Cylinder in a cross flow

When the pipes are under the airflow blown by the fan, the air after the pipe is warmer thanthe air just outside of the fan.

So during the passage under the pipe, there is a transfer of heat between the pipe and the air.

The equation describing the heat loss is the same form as before:

So per unit of length,

The only difference is for the convection coefficient, because the Nusselt number is expressedin another form which dependant on the blown air.


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Where U is the air velocity.

We have a different expression for the Nusselt number as the case may be.

See appendix B, table B.2 for the values of C and m.

Where all properties are evaluated at T , except Prs, which is evaluated at Ts.

If Pr10, n= 0.37; if Pr> 10, n= 0.36.

See appendix C, table C.3 for the values of C and m.

5.2. Radial heat transfer

The pipe, considered in the following equations, is formed by two concentric pipes. Waterflows through the smaller inner pipe and the outer pipe contains a Phase Change Material.(See figure below)

For the equations we consider a little part of the pipe, so we have:

Where

i, o, s subscripts for inlet, outlet, surface


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Tm is the mean temperature of the fluid

Assumptions:

The flow is fully developed

Incompressible flow

We have,

Hence,

Now for the radial heat transfer we take a "slice" of a pipe and then a little part of this slice, :Temperature of the inside surface

The governing radial heat transfer equations for a unit section along the length of a concentricpipe containing phase change material are then:

with

: mass flow rate of fluid [kg.s-1]

m : mass [kg]

5.3. Heat transfer during the phase change


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The storage mechanism for all solid-liquid PCM is the same. Once the melting temperature oa PCM is reached it changes phase from crystallisation to fusion. This is called the chargeperiod, as during this stage considerable quantities of latent heat are stored. The PCM willcontinue to store heat all the time it is at or above its melting point, or until its saturationpoint is reached. When the temperature falls below the melting point of the material it willbegin to discharge the stored latent heat, which it needs to do in order to crystallise andchange phase from liquid to solid.

When phase change occurs the latent heat effect is significantly greater than the sensible heat,hence the radial temperature distribution within each thin layer of the phase change materialis assumed to be uniform.

This temperature uniformity is further maintained by subdividing the phase change materialinto thinner layers.

At phase change temperature Tphc, the heat energy is used for the phase change process.

If Qlhtmax > Qlht >0

Tpcm = Tphc

Where,

Qlht : latent heat content of the phase change material [J. kg-1]

Qlhtmax : maximum latent heat capacity of the phase change material [J. kg-1

]

Tpcm: temperature of the phase change material [K]

Wpcm : rate of heat flow to the phase change material [W.kg-1]

5.4. Equation for the solar panel

For the solar panel it is assumed that there are no heat losses through the back and the sidesof the anel and the air tem erature at the front of the solar anel is inclusive of the sk


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temperature and the sky velocity.

The basic equation for the quantity of energy released from the solar panel (to the waterpassing through) is calculated using the following formula:

Q=F. [I.(t.a)-U.(Ti-Ta)]

Where Q is the quantity of energy released from the collector per meter squared of area.

The constants of the equations are:

F represents the collector heat removal factor and is a ratio of the heat actually delivered

by the collector to the heat that would be delivered if the absorber were at the sametemperature of the water exiting the panel.

I is the total solar irradiance [W.m-2], which are identified for the country, by the CIBSEguide.t.a is the product of transmittance and absorptance. It is a ratio representing the netirradiance absorbed through the plate whilst receiving solar energy.U represents the upward heat loss coefficient and is the steady state heat loss of the

collector [W.m-2.K-1].

Ta is the atmospheric air temperature

The variable of the equation is:

Ti the temperature of the water entering the collector. This value varies because of the initialtemperature of the water when the heating system is first activated and its heat loss to thePCM pipe once the collector is working.

VI. Experimental set-up

6.1. Parameters to be measured

Normally, so as to calculate the heat loss along the length of the pipe (equation (1)), we needthree temperatures:

Ts


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TTsurf

But, due to the fact that the pipes will be enough isolated (thickness=25mm) in order toreduce at the maximum the heat loss by the pipes, it is only necessary to measure thetemperature at the exit of the solar panel and at the entrance of the PCM so as to determinethe loss of energy in the pipe by using the equation (14).

What we also need so as to calculate the quantity of energy is the water flow rate, thats whywe have to use a flowmeter which we will install just after the pump.

Concerning the cylinder in a cross flow, to use the equation describing the heat loss (8) weneed two thermocouples in order to measure the temperature of the pipe surface (Ts) and the

temperature of the ambient air (T ).

But there is also a parameter which is necessary to know, it is about the air velocity called U .Actually, we must know this velocity so as to calculate the Reynolds number (10) in order tofind the convection coefficient (3).

Given that a box will be installed around the PCM pipes, it is now possible to measure theglobal energy got back by air, so as to do that, we need two temperature acquisitions: one atthe exit of the fan, and another one at the exit of the box.

We can consider thanks to the size of the box and to the blown air velocity that there will notbe any temperature gradient.

For the radial heat transfer equations, several points must be taken into consideration moreparticularly the mean temperatures of the fluid at the inlet and outlet of the pipe (14) for thequantity of heat.

In view of the fact that it is relatively hard to determine mean temperatures, we will use twothermocouples (one for the inlet and the other one for the outlet) situated at the middle of thepipe, corresponding to the ray of the pipe, what gives such a good rough estimate whiletemperature at the middle of the tube and temperature of the inside pipe must be really close.

Concerning the radial heat transfer in the strict sense of the word, four temperatures areuseful, it is about the temperature of the inner (16) and outer plastic pipe (18), thetemperature inside the PCM (17), and the temperature of the outside surface (19).

About the solar panel equation (21), the only variable is the temperature of the water enteringthe collector, therefore the only thing we will have to carry out is to note down themeasurement done by a thermocouple situated inside the pipe just before the solar panel.

For an additional calculation, we can use the equation concerning the quantity of heat (14), in

order to determine the quantity of heat absorbed by the water passing through the solarcollector, for that we can input another thermocouple at the exit of the solar panel so as tohave a the two necessary temperatures for the calculation; the water flow rate remaining thesame as the one measured before.

We propose in order to see the temperature evolution inside the PCM, to take severalmeasurements on the same pipe.

These measurements consist in the acquisitions of water temperature and the temperature ofthe PCM at different depths.


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This representation is proposed in the figure below.

6.2 Measurement procedure

All the equations written below are simpler than the ones given in the fifth chapter which aretoo theoretical for such an application. We do not need these complicated equations so as to

obtain a quiet good approximation of the real heat exchanges.

1. Heat loss per unit of copper pipe

The aim of this measurement is to characterize for a given duct the heat loss per unitlength of copper pipes (Q/L) with a determined water flow rate.

It is necessary for this calculation to know three different temperatures: the temperature

at the outlet of the solar panel and the temperature at the first PCM pipe inlet

For the calculation we need the following equation:

2. Heat recovered by the water circulating inside the solar panel

The aim of the measurement is to estimate quantitatively and for a given water flow rate, theheat recovered by the water circulating inside the solar collector.

It is necessary for this calculation to know the two following temperatures: the temperature at

theinlet and the outlet of the solar panel.

The existing relation between these two temperatures in order to determine the heatrecovered is:

1. Heat gained by the air

The aim of this experimental study is to determine the heat gained by the air passing cross thePCM pipes through the insulation "box".


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value of the air flow.

For the calculation we need the following equation:

f, pcm, a, fo, bo: subscript for fluid, phase change material, air, fan outlet, box outlet

spi, spo, : subscripts for solar panel inlet and outlet.

6.3 Break down of costs for the system

Product Size Unit Quantity Priceper

unit

Total

Copper pipes,50m

Diam. 15mm 3m 17 3.27 55.59

Plastic pipes,9m

Diam. 15mm 2m 5 2.69 13.45

Plastic pipes,9m

Diam. 32mm 2m 5 2.99 14.95

Insulation,50m

Diam. 15mm 1m 50 1.98 99

Valves Diam.15mm 1valve

6 2.85 17.1

Plaster board 2400*1200*95mm 1board

40 4.99 199.6

Insulation 7000*370*200mm 1 roll 22 11.99 263.78

Thermocouples Length 150mm 1item 10 12 120

Data logger 1item

1 899 899

Waterflowmeter

Diam.15mm 1item

1 271.6 271.6

Anemometer 1item 1

Fan CCI 1

item

1

Pump 1item

1 263 263

Solar panel 2.6m2 1 1 298 298


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item

TOTAL 2515.07

In this table are the materials we need to build the system and the prices we obtained aftercontacting the specialised companies.

You can see below the final total which gives a quite good approximation of the final cost ofthis system.

6.4 Be careful about

Concerning the solar panel.

So as to have a maximum efficiency of the solar panel, this one must be situated in a placewithout any trees, in order that the solar radiation should be absorbed by the flat-platecollector and not by the leafs.

Another important point concerning the solar panel is the freeze protection, solar heatingsystems that use liquids as the heat transfer fluid need protection from freezing in any areawhere temperatures fall below 42F (6C), because of the wind that can cause water in pipesto freeze before the air temperature reaches 32F (0C).

There are two basic methods for protecting the collector and piping from damage due to

freezing temperatures: using an antifreeze solution as the heat transfer liquid; or draining thecollector and piping, either manually or automatically, when the collector temperature fallsbelow a certain level. Since the main purpose for insulating the collector and piping is to

reduce heat loss and increase performance, heavy insulation may not keep the collector loopfrom freezing in very cold weather.

There are several cases of antifreeze protection, as much as there are solar heating systems,thats why we will only explain our case.

The only heat transfer fluid used in our system is water, what make our system be the mostvulnerable to freeze damage. "Draindown" or "drainback" systems typically use a controller todrain the collector loop automatically. Sensors on the collector and storage tank tell thecontroller when to shut off the circulation pump, to drain the collector loop, and when to start

the pump again. Improper placement or the use of low-quality sensors can lead to their failureto detect freezing conditions. The controller may not drain the system, and expensive freezedamage may occur. We also have to be sure that the sensors are installed according to themanufacturer's recommendations, and check the controller at least once a year to be sure thatit is operating correctly. To ensure that the collector loop drains completely, there should alsobe a means to prevent a vacuum from forming inside the collector loop as the liquid drainsout. Normally an air vent is installed at the highest point in the collector loop. It is goodpractice to insulate air vents so that they do not freeze up and to make sure they remainunobstructed by anything that could block the air flow into the system when the drain cycle isactive.

Collectors and piping must slope properly to allow the water to drain completely. Allcollectors and piping should have a minimum slope of 0.25 inches per foot (2.1 cm per meter).


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.

There are two major problems with the phase change materials, phase segregation andsupercooling.

The phase change behaviour of salt hydrate PCMs is more complex than that of organic

compounds because hydration/dehydration occurs, rather than simple melting/freezing. Salthydrates exhibit three general types of phase-change behaviour : congruent, incongruent andsemi-congruent melting. The desirable behaviour is congruent melting which occurs when thesolid phase composition is the same as the liquid phase composition. Semi-congruwentmelting occurs when a material has two or more hydrate forms with differing solidcompositions and melting points. Incongruent melting materials yield two distinct phase uponmelting: a saturated solution and a precipitate of insoluble unhydrous salt.[10]

The problem of segregation occurs after a certain amount of cycle done by the phase changematerial, in that case the hydration/dehydration process does not appear identical to themelting/freezing process. The material can be transformed into other hydrate form(s) before

either complete melting or freezing occurs, resulting in a temporary loss in thermal storagecapacity.

Several PCMs exhibit supercooling that is on attempting to freeze the material, thetemperature drops well below the melting point before freezing initiates. Once the freezingprocess begins, the temperature rises to the melting point and remains until the material isentirely frozen. If supercooling is excessive it can prevent the withdrawal of heat from thePCM.[11]

To minimize supercooling, two approaches to nucleation have been tried: the addition of achemical nucleating agent to the PCM and the use of a cold finger. Nucleating agents aresubstances upon which the PCM crystal will deposit with little or no supercooling. The use ocold finger is a surface within the storage container is maintained at a cooler temperature thanthe maximum supercooling temperature needed to promote nucleation.[10]

Finally, in order to avoid a "water hammer" in the system, we can install a protection valve forthe water flowmeter and a by-pass for the pump.

Thus, before starting the pump, it is necessary to check that the valve is turned off and that theby-pass is open.

VII. Conclusion

This training period seemed to be for us a chance to apply our knowledge and skills; but in

fact, it was more than a single application, we have learnt lots of things and improved ourskills.

We discovered another way to organise our work, to take some decisions and to solveproblems with the facilities available to us.


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Furthermore, we were fortunate to discover another field of study, which has aroused ourinterest, this being solar energy, and the storage of this energy inside of phase changematerials.

Communication was one of the most important skills that we developed during this period,both written and verbal.

This stay in England has brought to us a lot, especially the ability to work as a team with

people we have never previously met.

Finally, our work was important to us but also to the team.

With all the objectives set being met, our study will allow Dr. Kenneth Ips team to follow theirproject, and build the model we designed. In order to carry out tests on the storage capacity ofphase change materials.

In addition we discovered the English way of life and way of working, which was reallyimportant to us due to our wish to continue our studies and to work in England.

Appendix B

B.1 Choice of the components for the construction of the system

All the devices on this appendix have been found in the building furniture shop, named B&Q,in Brighton. The following prices wee find in this shop.

Copper pipes

Size: 15mm 3m

Price: 3.27

Plastic pipes

Speedfit class S, for water

Size: 15mm 2m

Price: 2.69

Size: 32mm 2m

Price: 2.99

Insulation for pipes

Size: 15mm 25mm 1m

Price: 1.98

Insulation for wall

Miraflex fiber, R=4.6


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ze: mm mm mm

Price: 11.99

Plasterboards

Size: 2400mm 1200mm 95mm

Price: 4.99

Gate valves

Size: 15mm

Price: 2.85

Lewes RoadPavillion Retail Park

BrightonEast Sussex

BN2 3QA

Tel: 01273 679926

Fax: 01273 689098

B.2 Choice of the pump

Applications


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and air conditioning systems.

Options

Single or twin head.

Temperature range:

Pressure rating:

Pump connections: -10 to +130C

6 Bar

1.25"BSP to 80mm

Contact Information

For all enquiries originating from the UK the following contacts should be used.

Telephone: 01283 523000

FAX: 01283 523099

Wilo Salmson Pumps Limited

Centrum 100

Burton-on-Trent

Staffordshire

England

DE14 2WJ

B.3 Choice of the fan

Dimensions in mm

CC125CCI125 CC160 CCI160 CC200CCI200

Diameter


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(mm)

A 260 360 300 400 325 425

B 130 180 150 200 162 212

Technical characteristics

Engine220/230V

Power Intensity Velocity Temperaturemaxi of air

Weight Velocity noiselevel

- 50 Hz (watt) (Amp) (tr/min) (C) (kg) Regulator at 1m(dB(A))

CC125 75 0,39 2500 50 5,5 R 200 39

CCI125 75 0,39 2500 50 13,0 R 200 35

CC160 98 0,48 2130 60 7,0 R 200 41

CCI160 98 0,48 2130 60 16,0 R 300 38

CC200 191 0,91 2330 60 9,0 R 300 49

CCI200 191 0,91 2330 60 19,0 R 300 45

CODUME

General Information:[email protected] :[email protected] :[email protected]

[email protected] site :http://www.condume.com

B.4 Choice of the thermocouples

The OMEGA low noise thermocouple probes and connectors maintain an electricalconnection from the sheath of the probe, through the connectors, all the way to your
http://www.condume.com/mailto:[email protected]:[email protected]:[email protected]:[email protected]


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. ,against electrical noise. The external strap maintains the electrical connection of the groundwire, and also strengthens the mechanical connection between the two connectors. Thefemale connector features a handy write-on area, for easy identification.

Junction Types

Grounded Exposed Ungrounded

Thermocouple T, Alloy COPPER-CONSTANTAN, 304 SS Sheath

SheathDiam.

Modelnumber

Price Modelnumber

Price

150mmLength

G/E U 300mmLength

G/E U

1.0mm HGTMQSS-M100(*)-150

19 20 HGTMQSS-M100(*)-300

19 21

2.0mm HGTMQSS-

M150(*)-150

17 18 HGTMQSS-

M150(*)-300

17 18


17 18 HGTMQSS-M300(*)-300

17 18

*Specify junction type: E (Exposed), G (Grounded), or U (Ungrounded).

Omega Engineering Ltd.

One Omega Drive

River Bend Technology Centre

North Bank

Irlam, Manchester M44 5EX

Telephone:161-777-6611

FAX:161-777-6622

Free Phone:0800-488-488

e-mail:[email protected]

Internet site: http://www.omega.co.uk/uk/index.html

B.4 Choice of the thermocouples
http://www.omega.co.uk/uk/index.htmlmailto:[email protected]


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The OMEGA low noise thermocouple probes and connectors maintain an electrical

connection from the sheath of the probe, through the connectors, all the way to yourinstrumentation. This system assures high accuracy measurements, providing protectionagainst electrical noise. The external strap maintains the electrical connection of the groundwire, and also strengthens the mechanical connection between the two connectors. Thefemale connector features a handy write-on area, for easy identification.

Junction Types

Grounded Exposed Ungrounded

Thermocouple T, Alloy COPPER-CONSTANTAN, 304 SS Sheath

SheathDiam.

Modelnumber

Price Modelnumber

Price

150mmLength

G/E U 300mmLength

G/E U


19 20 HGTMQSS-M100(*)-300

19 21


17 18 HGTMQSS-M150(*)-300

17 18


17 18 HGTMQSS-M300(*)-300

17 18

*Specify junction type: E (Exposed), G (Grounded), or U (Ungrounded).

Omega Engineering Ltd.

One Omega Drive

River Bend Technology Centre

North Bank

Irlam, Manchester M44 5EX

Telephone: 161-777-6611

FAX: 161-777-6622

Free Phone: 0800-488-488
mailto:[email protected]:[email protected]


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e-mail: [email protected]

Internet site: http://www.omega.co.uk/uk/index.html

B.5 Choice of the data logger

In order to have an easier reading of the measurement done by the thermocouples, it is betterto use a laptop, which also enables to have a really good data acquisition.

B.6 Choice of the water flowmeter.

Steel Turbines - Liquid applications

Type TB

Threaded male BSPP

Pmax: 300 bar

Pressure Loss Liquid (0.8 s.g.): 300mbar at Qmax

Temperature: -20 to + 120 degrees C

Internals: Stainless Steel

Body: Stainless Steel

Rotor: Stainless Steel

Liquid Turbines

Size Flowrate Linearity Length

(inches) (metric) (Litres/min) LTB

1/2" 13mm 2 to 20 +/- 0.5% 70mm
http://www.omega.co.uk/uk/index.htmlmailto:[email protected]


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5/8" 16mm 5 to 50 +/- 0.5% 70mm

3/4" 19mm 14 - 140 +/- 0.5% 82mm

1" 25mm 27 - 270 +/- 0.5% 88mm

1 1/2" 38mm 55 - 550 +/- 0.5% 114mm

2" 51mm 114 - 1140 +/- 0.5% 133mm

3" 76mm 227 - 2270 +/- 0.5% ---4" 102mm 454 - 4540 +/- 0.5% ---

6" 152mm 908 - 9080 +/- 0.5% ---

8" 203mm 1820 -18200

+/- 0.5% ---

Westcroft Estate,

Rhodes,

Middleton,

Manchester,

M24 4GJ

Tel: + 44 (0) 161 643 3681

Fax: + 44 (0) 161 655 3785

Internet site: http://www.emoltd.co.uk

B.7 Choice of the air flowmeter

WAA151 Anemometer

- Optoelectronic sensor
http://www.emoltd.co.uk/


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- Low intertia and starting threshold

- Excellent linearity up to 75 m/s

- Shaft heating

The WAA151 is a low-threshold precision cup wheel anemometer with excellent linearity overthe entire operating range, up to 75 m/s. The output frequency is directly proportional to wind

speed.A heating element in the shaft tunnel keeps bearings above the freezing level in cold climates.

The instrument is typically mounted at the southern end of Vaisala's standard WAC151 CrossArm.

Measuring range 0.4 ... 75 m/sAccuracy 0.17 m/s (standard deviation)Starting threshold < 0.5 m/sDistance constant 2.0 m

Operating power supply 9.5 ... 15.5 VDC, 20 mA typicalOperating temperature -50 ... +55C (with shaft heating)Weight 560 g

VAISALA Ltd, Birmingham Operations.

Vaisala House

349 Bristol Road

Birmingham B5 7SW

UNITED KINGDOM

Phone (nat.): (0121) 683 1200

Telefax: (0121) 683 1299

Managing Director: Jonathan Lister e-mail:[email protected]

Sales&Marketing: Andy McDonald e-mail: [email protected]

Brooke Pearson e-mail:[email protected]

Internet site: http://www.vaisala.com

Appendix C

Table C. 1
http://www.vaisala.com/mailto:[email protected]:[email protected]:[email protected]


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Thermophysical properties of air at Atmospheric Pressure.

T r Cp m.106n.106 k.103a.106 Pr

(K) (kg/m3) (kJ/kg.K) (N.s/m2) (m2/s) (W/m.K) (m2/s)

Air

100 3.5562 1.032 71.1 2.00 9.34 2.54 0.786

150 2.3364 1.012 103.4 4.426 13.8 5.84 0.758

200 1.758 1.007 132.5 7.590 18.1 10.3 0.737

250 1.3947 1.006 159.6 11.44 22.3 15.9 0.720

300 1.1614 1.007 184.6 15.89 26.3 22.5 0.707

350 0.9950 1.009 209.2 20.92 30.0 29.9 0.700

400 0.8711 1.014 230.1 26.41 33.8 38.3 0.690

450 0.7740 1.021 250.7 32.39 37.3 47.2 0.686

500 0.6964 1.030 270.1 38.79 40.7 56.7 0.684

550 0.6329 1.040 288.4 45.57 43.9 66.7 0.683

600 0.5804 1.051 305.8 52.69 46.9 76.9 0.685

650 0.5356 1.063 322.5 60.21 49.7 87.3 0.690

700 0.4975 1.075 338.8 68.10 52.4 98.0 0.695

750 0.4643 1.087 354.6 76.37 54.9 109 0.702

800 0.4354 1.099 369.8 84.93 57.3 120 0.709

850 0.4097 1.110 84.3 93.80 59.6 131 0.716

900 0.3868 1.121 398.1 102.9 62.0 143 0.720

950 0.3666 1.131 411.3 112.2 64.3 155 0.723

1000 0.3182 1.141 424.4 121.9 66.7 168 0.726

1100 0.3166 1.159 449.0 141.8 71.5 195 0.728

1200 0.2902 1.175 473 162.9 76.3 224 0.728

1300 0.2679 1.189 496 185.1 82 238 0.719

1400 0.2488 1.207 530 213 91 303 0.7031500 0.2322 1.230 557 240 100 350 0.685

1600 0.2177 1.248 584 268 106 390 0.688


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1700 0.2049 1.267 611 298 113 435 0.685

1800 0.1935 1.286 637 329 120 482 0.683

1900 0.1833 1.307 663 362 128 534 0.677

2000 0.1741 1.337 689 396 137 589 0.672

2100 0.1685 1.372 715 431 147 646 0.667

Table C.2

Constants of equation (11) for the circular cylinder in cross flow.

RedCm

0.4 4 0.989 0.330

4 40 0.911 0.385

40 4000 0.683 0.466

4000 40,000 0.193 0.618

40,000 400,000 0.027 0.805

Table C.3

Constants of equation (12) for the circular cylinder in cross flow.

Red C m

1 40 0.75 0.4

40 1000 0.51 0.5

103 2.105 0.26 0.6

2.105 106 0.076 0.7

Glossary

absorptionThe light energy that is captured by a surface.

insolationA measure of the amount of solar radiation striking a surface. Maximuminsolation on the Earth's surface occurs when the sun is directly overhead, and is about 1000
http://freespace.virgin.net/TEMP/FrontPageTempDir/studentbackground.html#anchor761105http://freespace.virgin.net/TEMP/FrontPageTempDir/studentbackground.html#anchor771230


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wa s per square me er.

insulation Material used to slow the transfer of heat. Used to make buildings more energyefficient. Do not confuse with "insolation" above!

joule (J) One joule is the amount of work required to exert a force of one Newton through adistance of one meter.

kilowatt hour (kWh) Unit used to describe the power produced by an energy source; one

kWh equals 1000 watts sustained for one hour.phase change materialMaterial used for the storage of energy

power The rate of doing work or the amount of work done in a given time. The unit of poweris the watt (W).

reflectionThe light energy that bounces off of a surface.

renewable energyEnergy that can be efficiently replenished or obtained from wasteproducts. Examples include solar energy, geothermal energy, wind power, and tidal power.

solar panel Instrument used to absorb the solar radiationsolar radiation Energy as visible light and other forms of electromagnetic radiationoriginating from our Sun.

watt (W) Unit of power. Equal to one joule of work per second (J/s).

References

http://www.eren.doe.gov/solarbuildings/techdescr.html

1.Association of Conservation of Energy.Association of Conservation of Energy Briefing

Notes. Association of Conservation of Energy, 1994(13): p. 1.

2.Weider, S.,An Introduction To Solar Energy For Scientists and Engineers. 1982, New York:John Wiley & Sons.

3. Unknown, Applications Handbook. 1991.

4.CIBSE. Guide A3 Thermal Properties of Building Structures. 1986, London: The CharteredInstitution of Building Services Engineers.

5.Lane, G.A.,Solar Heat Storage: Latent Heat Materials Volume I: Backgroundand ScientificPrinciples. Vol. I. 1983, Florida: CRC Press, Inc.

6.Abhat, A.,Low temperature latent heat thermal energy storage: Heat storage materials.Solar Energy, 1983. 30(4): p. 313-332.

7.Ghoneim, A.A. and S.A. Klein, The effect of phase change material propertieson theperformance of solar air based heating systems. Solar Energy, 1989. 42: p. 441-447.

8.Hoogendoorn, C.J. and G.C.J. Bart,Performance and modelling of latent heat stores. Solarenergy, 1992. 48: p. 53-58.

9.Lane, G.A.,Solar Heat Storage: Latent Heat Materials Volume II: technology. 1983,

Florida: CRC Press Inc.

10.Eissenberg and al., whats in store for phase change thermal storage materials for activeand passive solar applications. 1980. P. 12-16.

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