physics laboratory experimental analysis hvac - thermal

7/30/2019 Physics Laboratory Experimental Analysis HVAC - Thermal

1/16

1

Physics Laboratory Assignment

Christopher Earnshaw

Student ID: 11713233

Experiment Title: Thermal Storage

Project Report Title: Consultative Report: Exploration & Optimal Selection Of Materials To Be Utilised

For Commercial HVAC Systems.

The report will be itemised under the following headings;

Introduction Page 2

Method & Hypothesis Page 3

Bill of Materials Required & Project Techniques Page 6

Statistical Logging & Analysis Page 10

Conclusion & Recommendation Page 15

References Page 16


2/16

2

Introduction

In this assignment we have been tasked with performing two separate experiments that will be able to

provide the necessary evidence for the selection of a particular material, on the basis of the preeminent

thermally conductive and thermally isolative properties, for the use in a HVAC (Heating, Ventilation and

Conditioning) system. In this assignment for the purposes of having a professional and marketableoutcome/theme, the main experiment will be referred to as The Project, and the assignment will be

referred to as The Report from here onward.

The importance of being able to utilise less energy to power and heat buildings has become more

relevant in recent years, due to spiking energy costs associated with increased spending on electrical

infrastructure and a shortage in natural resources, along with other factors leading to higher energy

costs for the consumer. Builders and project managers must now become more innovative in their

approach to find ways to reduce load, increase efficiency, and utilise renewable fuel resources in

facilities of all types [National Institute of Building Sciences, 2012,]

Through our ability to make selection of the appropriate material for the HVAC system based on

conclusions drawn from the Project, the customer can therefore optimise an appropriate system that

will draw less electrical/gas energy used to generate hot water to be used throughout the buildings

HVAC system.

The Project brief that was handed to the team was as follows;

A small building is to be heated during the daytime using thermal energy stored in materials buried

underground. In the proposed system, the heat storage material will be held within thin walled copper

pipes of 65mm in diameter. The material is heated using off-peak electricity during the night, from an

ambient underground temperature of 15 degrees Celsius to 95 degrees Celsius. In the morning heat isremoved by water passing through a sheath surrounding the heated material. The heated water then

passes through heat exchange pipes in the building to warm the rooms.

There are two basic requirements of any material to be in the system:

- It should absorb a large amount of heat when the temperature is raised from 15 degrees Celsius to 95

degrees Celsius. During the course of a day it will lose this heat and eventually cool to 15 degrees

Celsius.

- It should lose its extra heat slowly during the day to keep rooms comfortably warm over a long period

of time.

The materials themselves to be selected and will be put under investigation are; Water, Sand & Coarse

Gravel. The material of the piping will be standard copper piping (65mm diameter) and will be in the

form of a calorimeter.

We have been given a number of different objectives, possible observations and predictable experiences

to be proven in order to predict which material is best suited for the project. Through Scientific


3/16

3

investigation we will be able to demonstrate the following through this report, in addition to the outline

above;

- Investigation of the various concepts involved in and associated with thermal properties of the

selected materials under review.

- Make a hypothesis to prove certain outcomes, or dissuade the theory based on lack of physical

evidence.

- Tests and trials to demonstrate the heat content of the materials and the frequency of the heat

transfer.

- Determine how much thermal capacity of energy can actually be stored in a material when the

temperature is raised.

- Calculate an engineering decision based on the observations and analysis of the statistical results and

details of the project, to provide a conclusively objective view of the argument.

- Make suggestion to provide the reader with alternatives and other possible improvements to the

original concept.

- Make conclusions drawn from the actual experiments conducted to validate the methodology.

Method & Hypothesis

In the Project research & development stage, we outlined the necessary methodology based on the

given instructions from the Experiment coordinator. Such items that needed to be taken into

consideration were as follows;

- Determining of the Specific Heat Temperature of each material

- How much of each different material, will be required to hold a nominal estimate of 60 Mega joules of

thermal energy when the temperature has been raised from e.g. 15 degrees Celsius (room temperature)

to 95 degrees Celsius.

- What length of piping will need to be sought to contain each of the materials under investigation.

- Determine the rate of which heat will be transferred from each of the storage materials to the water

sheath under the building, when the heat storage material is above 85 degrees Celsius and the

surrounding water is at 20 degrees Celsius.

We then need to develop a hypothesis to make a suggestion or concept with disregard to any

assumptions of truths to meet the items considered above, it is through this that of the three materials


4/16

4

under investigation, the one that would be the most logical choice, of the three, would be water, based

on the fact that it has such a high specific heat capacity (4186 joules per Kg-1

/Kelvin-1

), Constant pressure

molar heat capacity (joules per mol-1/Kelvin-1) and Volumetric heat capacity (joules per cm-3/Kelvin-1),

which is only surpassed by Ammonia on a materials scale. So by conducting the experiment we hope to

prove these raw facts correct.

Through the practical demonstration of each material, we will also be looking to see if not repeatedly

notice some of the following based on the outlines above;

- Determining an accurate rate that is required to raise the temperature of 1 kg of each material by 1

degree Celsius. Which is the specific heat temperature of each material (water & copper are already

given as follows; water at 4190joules per Kg-1

/Kelvin-1

, copper at 390joules per Kg-1

/Kelvin-1

) Based on

background research into Specific Heat temperatures, The Project team made the prediction that Sand

and Gravel would not be as high as water due to the fact that they are not only solids loosely packed

together (taking longer and requiring more energy to heat) compared to water, but some of the base

materials that make up Sand and Gravel (Silica and Quartz) have greatly lower thermal properties than

that of Water.

- The actual heat lost by the addition of hot water, will be dissipated heat transferred and gained by the

copper piping and material. (System reaches equilibrium) Which The Project team predicted would be

more suited to water just by itself.

- Repetition of the experiment to the tune of three times to notice any deviations or uncertainties in the

results, as well as to provide a clear view into the accuracy of each prediction.

- Separately, based on the mass from each of the samples and their specific heat capacity we will be able

to determine how much of the piping will be required to achieve the required linear density (in Kg) permeter (unable to hypothesise with incomplete equations or data)

In addition to these points, some of the points outlined in the introduction should also be validated/

flawed as well. We need to now describe each of the experiments mathematically and explain the

variables/predictions behind each of the experiments

First Experiment

In order to mathematically break down what we are looking at for the first experiment and to explain

how each of the processes will work in terms of mathematics, the following Isochoric process equation

for specific heat derivation must be employed;

Q = mCvT

With (Q) being our heat energy this was already given as 60Mega Joules (60 x 106Joules)

(m) Being our mass of each material involved (Average) and is weighed at the start of each test

(calorimeter is first weighed, then the material added, re weighed, then the mass of the calorimeter


5/16

5

deducted, then re weighed with the water in and the mass of the calorimeter deducted) This should give

us our masses for each item.

(Cv) Being our Specific heat capacity at a constant volume of either sand or gravel, this is what we are

looking to attain, water and copper already given above. This means that we only need to conduct six

attempts of this experiment; three for gravel, three for sand, then take the averages for each.

(T) Being our Change in Temperature (Tinital - Tequilibrium) for Water, then reversed for copper and

material, (Tequilibrium - Tinital) Initial, being the room temperature (without hot water added) and

Equilibrium temperature (the temperature, that the 100degrees Celsius water is added to then balances

out, but before cooling). (Under instruction, Change in temperature for Copper will be regarded as the

change in Temperature for the material)

With the specific items of this equation being outlined we need to establish a new formula, this is

because we rearrange the formula to be able to determine (Cv) (cancel out (Q) for now as it is irrelevant

for this part of the experiment), and get;

*Footnote* - H2O meaning water, Cu meaning Copper

We need (Cv) to be able to substitute this back into the original formula, to then be able to answer the

question of how much material will be required to store 60Mega Joules of thermal energy when the

temperature is raised by 80 degrees Celsius.

We will go into the length of the copper pipe to be able to hold 60 Mega joules, in the Statistical logging

& Analysis section, as this cannot be hypothesised without the complete equation from above.

Second Experiment

In this experiment we will be dealing with the dissipation of heat through the material and into the

surrounding sheath containing water. We need to explore 3 different pieces of information for this

experiment;

- The average rate of increase in the temperature of the water per second

- The average heat power in kilo watts transferred to the water.

- The average power transfer into the water per meter of copper container

Mathematically we can use the same formula to achieve outcomes for each three points, we need to

measure the energy transferred in terms of power so we can use the power formula, then expand for

(Q);


6/16

6

With (Q) being defined already we need to change the variables for this experiment, (m) will be 100ml of

water or 100gramms, (C) being the specific heat of each material, (T) being the change in temperature

of the water within the sheath surrounding the copper calorimeter.

(t) Being time which we will work out per second, so for purposes of calculation we will be using 300.

During the actual experiment we will be also focusing on the following;

Determine the rate of which heat will be transferred from each of the storage materials to the water

sheath under the building, when the heat storage material is above 85 degrees Celsius and the

surrounding water is at 20 degrees Celsius.

So we will record the temperature over 5 minutes in order to see the rate at which we measure

temperature vs. time (this should allow for enough time for the materials to equalise).

Using the power divided by length formula. We can use the result from the first equation, to answer the

third point, of how much energy is transferred into the water per meter;

(P) being the power calculated from the first equation, (L) being the length of the calorimeter

(0.074metres)

From this the project team made the prediction again that water would be the more optimal choice forthis experiment due to the claims that it has such a high Specific Heat capacity. So through the process

of experimentation we will be looking to validate this claim.

Later on in the Report, the equations above will be used in the Statistical Logging & Analysis to work out

the exact figures.

Bill of Materials Required & Project Techniques

First Experiment

For this experiment the following will be used;

- Copper Calorimeter (65mm in diameter, 74mm in height)

- Roughly 350-370 grams of Sand and Gravel per test so multiply by three for each material


7/16

7

- Thermal insulated cup holder (Styrofoam)

- Measuring beaker

- Thermometer (thermocouple plugged into a computer to record data)

- Hot water, around 200mls (a lot less than this will be actually used)

- Brass tongs

- Weighing Scales

- Gloves

- Pencil and paper for data recording

- PPE (gloves and glasses)

- Stirrer

-Paper towels

For the experiment itself, it needs to be set up as follows;

1. Set up computer, Thermometer, Thermal insulated cup holder etc. Weigh the coppercalorimeter, and record the result.

2. Place the gravel or sand into the calorimeter, leaving roughly 5mm from the top, then weigh thecombined weight, check the temperature of the gravel or sand and record the results. Measure

the temperature of the hot water and record the results.

3. Using the provided PPE carefully fill the calorimeter with hot water until full and then weigh therecorded result.

4. Placing the full calorimeter carefully into the thermal insulated cup holder, Use the stirrer to mixthe material with the water, and then place the thermometer into the mixture.

5. Wait for roughly 2-3 minutes for the temperature to stabilise or reach equilibrium (this can beobserved on the computer) Record the temperature.

6. Using the paper towels etc., remove and clean the calorimeter of the material, making sure thatthe calorimeter is completely clean and has cooled, if required interchange the calorimeter to

one that is at room temperature.

7. Repeat the process again from step 2 until you have three sets of results for each material.


8/16

8

The diagram below illustrates the correct set up of the experiment.

Second Experiment

For this experiment the following will be used;

- Copper Calorimeter (65mm in diameter, 74mm in height)

- Roughly 350-370 grams of Sand and Gravel per test (this needs to be heated to 90-100 degrees Celsius)

- Thermal insulation

- Measuring beaker

- Thermometer (thermocouple plugged into a computer to record data)

- Water at room temperature, 100mls for outer sheath, and Hot water, roughly 200mls for the copper

calorimeter.

- Perspex Cup

- Brass tongs

- Weighing Scales

- Gloves

- Pencil and paper for data recording


9/16

9

- PPE (gloves and glasses)

- Paper towels

For the experiment itself, it needs to be set up as follows;

1. Set up computer, Thermometer, Thermal insulation around the Perspex cup. Set up thecomputer recording device to 5 minutes. Weigh the copper calorimeter, and record the result.

2. Pour the room temperature water into the Perspex cup and measure the temperature, recordthe results.

3. Place the hot gravel, hot sand and the hot water into the calorimeter (this was pre-done for theexperiment, and was collected from an oven which was at around 100 degrees Celsius), then

weigh the combined weight, and record the results.

4. Using the provided PPE carefully lift the calorimeter into the Perspex cup.5. Place the thermometer into the water ensuring that the thermometer never touches the sides

of the hot calorimeter.

6. Depress the record button on the recording program to start.7. Once 300 seconds have elapsed, stop and save the results to the computer, remove the

calorimeter and clean the Perspex cup making sure that the cup is completely clean and has

cooled back to room temperature.

8. Repeat the process again from step 2 until you have three sets of results for each material.The diagram below illustrates the correct set up of the experiment.


10/16

10

Statistical Logging & Analysis

In this section the data gained from both project experiments will be tabulated and graphed to show

their results. We will also explore the analysis of the experiment, through the use of the mathematical

formulas prescribed in the previous sections.

First Experiment

From this experiment, we had collected the following raw data from both measurements and recordings

from the various tests, presented below;

Test No. Gravel Mass

(grams)

Gravel Initial

Temp

Hot Water Initial

Temp

Gravel Equilibrium

Temp

1 360.33 22.3 87 47.5

2 360.22 23 88 52.2

3 360.16 24.4 88.1 53.2Average 360.24 23.33 87.7 50.97

Test No. Sand Mass

(grams)

Sand Initial Temp Hot Water Initial

Temp

Sand Equilibrium

Temp

1 312.38 24.7 85.9 49.1

2 312.17 25.3 87.9 48.4

3 312.16 23.9 88.1 47.5

Average 312.23 24.63 87.3 48.33

The averages for the tables were achieved by adding up all of the values for a particular column then

dividing by the number of tests. E.g.

= 312.23g

From this experiment, we can see that the different materials have similar Equilibrium temperatures, as

in an average of around 4-5 degree difference between them. From conducting the experiment, we

noticed that the materials initial temperature played a great part in the final result as demonstrated by

the material at Equilibrium. There were no issues with running the experiment, however we must point

out that an explanation for the fluctuating initial temperatures could be to do with the fact that, as the

other teams took material from the larger storage container, the material toward the center became

exposed; this would be thermally warmer than the material at the top and sides.

Another Factor that would have had an effect on the uncertainty factor of the results would have been

the minor fluctuation of the initial water temperature, due to the fact that there were a number of

other teams taking hot water as well from the storage tank, depleting the level of hot water available.


11/16

11

These minor issues did not have a great effect on the temperature of the overall result but, must be

established as a possibility for errors, overall the experiment was successful.

Analysis of First Experiment

Here we will use the formulas prescribed in the previous sections to mathematically answer the

questions outlined from the project brief.

First we need to calculate (T), for Gravel;

(Tinital - Tequilibrium) for water is (87.7 50.97) = (36.73)

(Tequilibrium - Tinital) for copper & gravel is (50.97 23.33) = (27.64)

Then using the rearranged formula;


Using the information from the experiment listed in the table above, and correcting for standard unit

measurements, we will now be able to substitute our values into the formula to generate two

equations, for each material.

Joules per Kg-1/Kelvin-1

Then to repeat the calculations for Sand;

(Tinital - Tequilibrium) for water is (87.3 48.33) = (38.97)

(Tequilibrium - Tinital) for copper & sand is (48.33 24.63) = (23.7)

Then substituting the experiment values into the formula below;


Joules per Kg-1/Kelvin-1


12/16

12

To answer the question of how much material in kg would be required to store 60Mega Joules of

thermal energy, when the temperature is raised from room temperature to 90 degrees Celsius; this

equates to;

= 41,465kgs

= 28,651.79kgs

From this we need to then calculate the actual linear density of the calorimeter, to indicate how much

sand or gravel in kg/square meter will be required every meter.

4.84 Kilos per every 1 meter

4.216 Kilos per every 1 meter

Analysis of Second Experiment

With this experiment we did not encounter any significant problems whist conducting the test, however

as the reader will probably notice from the graphs below the water graph seems to have two moderate

increases in the temperature hump looking, and to provide an explanation as to why there was amoderate increase before the temperature reached equilibrium, like the other materials; Is that as the

thermal energy got transferred from the calorimeter to the surrounding water, the water at room

temperature in the surround, took time to mix correctly with the thermal transmitted energy, due to the

massive heat transfer, and essentially being unable to mix immediately.

For the second experiment we need to use the equation from the previous section for each of the

materials, in order to answer the questions put to us, by using the (C) value obtained from the previous

experiments, we can obtain (Q) by itself to result in the following;

In this case the overall time is 300 seconds as the experiment was conducted over 5 minutes (5 x 60

seconds)


13/16

13

Watts Per Second

Watts Per Second

Watts Per Second

To give an indication of the representation of the experiments conducted. Graphs below show the

actual temperature increase/decrease. Please disregard the time on the graph after 300 seconds, there

was a discrepancy with the time allowed, and hence was recorded up to 600.

0

10

20

30

40

1

4

4

8

7

13

0

17

3

21

6

25

9

30

2

34

5

38

8

43

1

47

4

51

7

56

0

Temp

erature(DegCelsius)

Time (Seconds)

Gravel

Temperature

0

10

20

30

40

144

87

130

173

216

259

302

345

388

431

474

517

560

Temperature

(DegCelsius)

Time (Seconds)

Sand

Temperature


14/16

14

To Answer the Second Question put to us, we need to compute the average heat power (in Kilowatts)transferred to the water. First we will need to calculate the change in temperature per second (degrees

Celsius/second) to do this we will need the following equation;

Degrees Celsius/Second



From this we can then go onto answering the average heat power (in Kilowatts) that then gets

transferred to the surrounding water, to do this we need to use the following equations, adjusting for SI

units;

Watts or Kilo Watts

Watts or Kilo Watts

Watts or Kilo Watts

0

10

20

30

40

50

144

87

130

173

216

259

302

345

388

431

474

517

560

Temperature(Deg

Celsius)

Time (Seconds)

Water

Temperature


15/16

15

To answer the third Question we can use the equation mentioned in the previous section;

So to calculate for each material;

Kw/Meter

Kw/Meter

Kw/Meter

Conclusion & Recommendation

To conclude, the project has set out to prove which material would be a more viable option for the

HVAC system. Through experimentation we have provided factual evidence as to the more optimal

choice for selection of a material to be used to in a system that has specified parameters from the

customer. The Project Hypothesis has been proven as well through experimentation, that water is the

best choice for the system. The project experiment has answered all of the questions put forward to the

project group and has been additional proof of the better choice for the system. By the use of

experiment we have also demonstrated that out of the two unknown materials, the sand could actually

hold more thermal energy as predicted due to its increased density and more surface area(s).

The project Author therefore recommends that by the use of water, the HVAC system will be roughly

three to four times more efficient with heat dissipation and thermally transmitted power, than any of

the other two materials, as proven through mathematical application.

With the success and validation of the hypothesis I would like to draw attention to the factors that we

could improve on next time we did a similar experiment. Firstly, with the materials in the first

experiment, we could address the issue we had with the storage and the temperature, possibly

spreading it out into a thinner mass to make the temperature closer to room temperature. Secondly to

make more tests available, as in, increase the number of tests from three to five. It must be said we did

fairly well regarding accuracy of the data collection, but by increasing the number of tests we can be

more certain, especially seen as the gravel and sand results were fairly close to each other. Thirdly we

would like to recommend that as the experiment was only limited to three materials, the customer

should explore utilising other materials/chemicals, to expand the possibility of materials that would be a

better options than water.


16/16

16

To conclude, the experiment for the project has proven a great amount of insight into the thermal

properties of the selected materials, whilst also reinforcing the knowledge gained through the lectures

and further studies. Through further research into the various strategies and methods employed in

HVAC Systems, we can see that this trend of searching out more viable options for highly efficient and

sustainable HVAC systems in the future is well founded, and through this research and experiment, we

can see that this acquired knowledge would help a career in the future in that field.

Whilst this was an individual report, I would like to mention that the other group members of the

project team were; Ben Bebbington and Mark Minchenko.

References

National Institute of Building Sciences, Data Needs for Achieving High Performance Buildings, 2012, USA

DASCEM Holdings Pty Limited - Performance Standards of HVAC Equipment for the Australian Building

Codes Board, 2003, Australia

Fundamentals of Physics, Halliday and Resnick, Jearl Walker, 9th Edition, Wiley 2011

http://www.airah.org.au/iMIS15_Prod/AIRAH/ - 25/04/2013 7:30pm

physics laboratory experimental analysis hvac - thermal

Documents