REFRIGERATOR REPORT

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

1.0Title

MEC 554-THERMALFLUIDS LAB THERMODYNAMICS II LAB

VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING

LECTURER: SITI HAJAR BINTI MOHD YUSOP

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

2.0Abstract The potential increase in COP is the greatest in applications where the heat sink and heat source temperatures are approximately equal and of relatively large magnitude. The minimum requirements to achieve these performance improvements are the selection of a mixture that yields the desired temperature change in both heat exchangers, a counter-flow heat exchanger that takes advantage of the temperature glide of the refrigerant and minimized degradation of the heat transfer process. The magnitude of the phase change temperature glide is related to the differences in the normal boiling points of the mixture constituents.

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

Table of Contents 1.0

Title................................................................................................................................. 1

2.0

Abstract .......................................................................................................................... 2

List of Symbols ........................................................................................................................... 4 List of figure ............................................................................................................................ 5 3.0

Inreoduction and Applications .................................................................................... 6

4.0

Objectives ...................................................................................................................... 7

5.0

Theory............................................................................................................................ 7

6.0

Experimental Procedures ...................................................................................... 11 6.1 Apparatus/Experimental Setup...................................................................... 11 6.2 Procedure .......................................................................................................... 13

7.0

Result ............................................................................................................................ 15 7.1 Data recorded .................................................................................................... 15

8.0

Discussion ..................................................................................................................... 18

9.0

Conclusion .................................................................................................................... 18

10.0 References .................................................................................................................... 19 11.0

Appendices .................................................................................................................. 20

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

List of Symbols A

Area over which force (F) acts (m2)

E

Elastic modulus (GPa)

F

Force (N)

( )

Initial dimension in direction i (mm)

T

Specimen thickness (m) Rate of chart displacement (mm/min) Rate of sample displacement (mm/min)

w

Specimen width (m) Displacement of chart (mm) Displacement of sample (mm) Strain =0

Predicted strain at zero stress Normal strain in direction i

E

Error in the predicted elastic modulus (GPa)

F

Error in the force (N) Change in dimension in direction i (mm)

t

Error in the specimen thickness (m)

w

Error in the width (m) =0

Error in the predicted strain at zero stress Error in the predicted intercept of stress-stain data (MPa) Error in the stress (MPa) Predicted intercept of stress-strain data (MPa) Engineering stress (MPa) Yield point (MPa) Ultimate strength (MPa)

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

List of figure Figure 1: Refrigerator ................................................................................................................. 6 Figure 2: Schematic diagram of refrigeration cycle ................................................................... 8 Figure 3: Computer controlled refrigeration and air conditioning unit [two condenser (water and air) and two evaporator] / THAR22C ................................................................................ 11 Figure 4: Schematic diagram of computer controlled refrigeration and air conditioning unit [two condenser (water and air) and two evaporator] ............................................................. 11 Figure 5: The location of valve (AVS3, AVS4, AVS5, AVS 6) ..................................................... 12 Figure 6: Computer system ...................................................................................................... 12

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

3.0

Inreoduction and Applications The age, the seasonal harvesting of snow and ice was a regular practice of most of the

ancient cultures: Chinese, Hebrews, Greeks, Romans, and Persians. Ice and snow were stored in caves or dugouts lined with straw or other insulating materials. The Persians stored ice in pits called yakhchals. Rationing of the ice allowed the preservation of foods over the warm periods. This practice worked well down through the centuries, with icehouses remaining in use into the twentieth century. In the 16th century the use of ice to refrigerate and thus preserve food goes back to prehistoric times. Through, the discovery of chemical refrigeration was one of the first steps toward artificial means of refrigeration. Sodium nitrate or potassium nitrate, when added to water, lowered the water temperature and created a sort of refrigeration bath for cooling substances. In Italy, such a solution was used to chill wine and cakes. During the first half of the 19th century, ice harvesting became big business in America. New Englander Frederic Tudor, who became known as the "Ice King", worked on developing better insulation products for the long distance shipment of ice, especially to the tropics. Refrigeration is used widely in various applications from industrial to domestic situations, mainly for the storage and transport of perishable foodstuffs and chemical substances. It has the prime function to remove heat from a low temperature region, and its can also be applied as a heat pump for supplying heat to region of high temperature. In this experiment we need to investigate the variation in Coefficient of Performance (

) of a

vapor compression refrigeration system. The experiment execute by using THAR22C Computer controlled refrigeration and air conditioning unit [two condensers (water and air) and two evaporators].

Figure 1: Refrigerator

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

4.0 Objectives The purpose of this experiment is to: 1. Investigate the variation in Coefficient of Performance (COPR) of a vapour compression refrigeration system at different coolong load.

5.0 Theory A refrigeration cycle works to lower and maintain the temperature of a controlled space by heat transfer from a low to a high temperature region.

High Temperature Reservoir, TH

QH E

W net

QL Low Temperature Reservoir, TL

Refrigeration duty is another term for the cooling effect of the refrigeration system, which is the rate of heat being removed from the low temperature region with specified evaporation and condensation temperatures. The unit for “duty” measurements is in Watts (for 1 ton of refrigeration = 3517 W)

The Vapor Compression Cycle

Ideal refrigeration systems follow the theoretical Reversed Carnot Cycle process. In practical refrigerators, compression and expansion of a gas and vapor mixture presents practical problems in the compressor and expander. Therefore, in practical refrigeration, compression usually takes place in the superheated field and a throttling process is substituted for the isentropic expansion.

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

Figure 2: Schematic diagram of refrigeration cycle

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

The cycle ; 1–2 2–3 3–4 4–1

Condensation of the high pressure vapor during which heat is transferred to the high temperature region. Adiabatic throttling of the condensed vapor from the condensing to the evaporating pressure. Evaporation of the low pressure liquid during which heat is absorbed from the low temperature source. Isentropic compression of the vapor, from the evaporating to the condensing pressures.

Energy Transfer Analysis  Compressor q4-1= h4 – h1 + w If compressor is adiabatic, q4-1 = 0 and w = h1 – h4 .

Power requirement, P = m (h1 – h4 ), where m is the flow rate of working fluid per unit time.  Condenser q1-2 = h2 – h1 + w .

w = 0, therefore q1-2 = h2 – h1 and rate of heat rejection Q1-2 = m ( h2 – h1 )  Expansion valve q2-3 = h3 – h2 + w w = 0 at the expansion valve, and the process is adiabatic Therefore h3 = h2

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

 Evaporator q3-4 = h4 – h3 + w w = 0, therefore q3-4 = h4 – h3 and rate of heat absorbed Q3-4 = m ( h4 – h3 ) Coefficient of Performance (COP) COP ref = q3-4 = h4 – h3 w h1 – h4

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

6.0 Experimental Procedures 6.1 Apparatus/Experimental Setup

Figure 3: Computer controlled refrigeration and air conditioning unit [two condenser (water and air) and two evaporator] / THAR22C

Figure 4: Schematic diagram of computer controlled refrigeration and air conditioning unit [two condenser (water and air) and two evaporator]

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

Figure 5: The location of valve (AVS3, AVS4, AVS5, AVS 6)

Figure 6: Computer system

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

6.2 Procedure 6a) Condenser-water and evaporator-water a. Water as a heat source is selected by opening valves AVS-4 and AVS-5 and then click “START”. b. The water flow rate at the condenser to 5 L/m and 3 L/m at the evaporator (evaporator load) are adjusted. c. The “COMPRESSOR” button is click. d. The data are start recorded when the system is stabilized by click “START SAVING”. e. The sampling rate at 120 second per sample is set. f. The data for six minutes (3 samples @ 360 second) are recorded by click “STOP SAVING”. g. The evaporator load is increased to 5 L/m and step (c) to step (f) are repeated.

6b) Condenser-water and evaporator-air a. Air as a heat source is selected by opening valves AVS-3 and AVS-5 and then click “START” b. The water flow rate at the condenser to 5 L/m and the air flow of the evaporator are adjusted until 50% of the maximal flow (evaporator load). c. The “COMPRESSOR” button is click. d. The data are start recorded when the system is stabilized by click “START SAVING” e. The sampling rate at 120 second per sample is set. f. The data for six minutes (3 samples @ 360 second) are recorded by click “STOP SAVING”. g. The evaporator load is increased to 100% and step (c) to step (f) are repeated.

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

6c) Condenser-air and evaporator-air a. Air as a heat source is selected by opening valves AVS-3 and AVS-6 and then click “START”. b. The air flow of the condenser is adjusted to maximum flow (100%) and 50% of the maximal flow at the evaporator (evaporator load). c. The “COMPRESSOR” button is click. d. The data are start recorded when the system is stabilized by click “START SAVING” e. The sampling rate at 120 second per sample is set. f. The data for six minutes (3 samples @ 360 second) are recorded by click “STOP SAVING”. g. The evaporator load is increased to 100% and step (c) to step (f) are repeated.

6d) Condenser-air and evaporator-water a. Water as a heat source is selected by opening valves AVS-4 and AVS-6 and then click “START”. b. The air flow of the condenser is adjusted to maximum flow (100%) and the water flow rate is adjusted at the evaporator to 3 L/m (evaporator load). c. The “COMPRESSOR” button is click. d. The data are start recorded when the system is stabilized by click “START SAVING” e. The sampling rate at 120 second per sample is set. f. The data for six minutes (3 samples @ 360 second) are recorded by click “STOP SAVING”. g. The evaporator load is increased to 5 L/m and step (c) to step (f) are repeated.

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

7.0

Result

7.1 Data recorded  Data had been recorded on the provided table of result.(separate sheet)

7.2 Sample calculation A. Experiment A  Refrigerant mass flow rate, mref (kg/s) mref = vref / v2 a) vref - change the unit for value SC-1(L/h): SC-1 = 27.64 L/h thus vref = 27.64 x (0.001/3600) = 7.68 x 10-6 m3/s b) v2 – taken from table A11 for saturated refrigerant 134-a(provided at appendices) At ST-2 = 39.62 oC Saturated vapour, vg (m3/kg)

Temperature(°C)

0.02017

38

v2

39.62

0.019952

40

=

v2 = 0.02017 m3/kg c) Therefore mref: mref = vref / v2 = (7.68 x 10-6 / 0.02017 ) = 3.808 x 10-4 kg/s

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

 Evaporator cooling load, Qevap(kW): a) The calculation of h3 – refer to table A11 for saturated refrigerant 134-a (provided at appendices): At ST-3 = 7.54 oC

hfg (kJ/kG)

Temperature(°C)

193.94

6

h3

7.54

192.35

8

=

h3 = 192.72 kJ/kg b) The calculation of h4 – refer to table A11 for saturated refrigerant 134a(provided at appendices): At ST-4 = 12.06 oC

hfg (kJ/kG)

Temperature(°C)

189.09

12

h4

12.06

187.42

14

=

h4 = 189.04 kJ/kg c) Therefore Qevap: Qevap = mref (h4-h3) = (3.808 x 10-4) (189.04 - 192.72) = -1.4 x 10-3 kW

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

 Coefficient of performance, COPref : At ST-1 = 462.811 W COPref = Qevap / (SW-1/1000) = -1.4 x 10-3 / (462.811/1000) = -3.02 x 10-3  Average coefficient of performance, COPref : Time (s)

COPref

120

-3.02 x 10-3

240

-3.90 x 10-3

360

-4.01 x 10-3

Thus average COPref = Σ COPref / 3 = -3.64 x 10-3 B. Experiment B 

The calculations for mref, Qevap, COPref and average COPref same as shown on Experiment A.

C. Experiment C 

The calculations for mref, Qevap, COPref and average COPref same as shown on Experiment A.

D. Experiment D 

The calculations for mref, Qevap, COPref and average COPref same as shown on Experiment A.

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

8.0

Discussion

This part of report is individually hand written. The result of each member is attched with this report.

9.0

Conclusion

This part of report is individually hand written. The result of each member is attched with this report.

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

10.0 References  Websites: 1) http://en.wikipedia.org/wiki/HVAC [Accessed 27/09/14] 2) http://home.howstuffworks.com/refrigerator.htm [Accessed 7/10/14] 3) http://www.mansfieldct.org/schools/mms/staff/hand/heatrefrig.htm[Accessed 7/10/14]

 Books: 4) Eastop & McConkey, Applied Thermodynamics for Engineering Technologists 5th Edition, Prentice Hall, 1993. 5) Yunus A. Cengel, Michael A. Boles,2006, Thermodynamics: An Engineering Approach 5th Edition, McGraw Hill. 6) Yunus A. Vengeland Micheal A. Boles, Thermodynamics An Engineering Approach,7th edition in SI units, 2011 , The McGraw-Hill Companies.

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A

11.0 Appendices

THERMODYNAMICS II VARIATION IN REFRIGERATION COEFFICIENT OF PERFORMANCE AT VARIOUS OPERATING CONDITIONS EMD5M5A