Determination of Refrigerator COP

Determination of the Coefficient of Performance of

Coca-Cola Refrigerated Showcase

Model CCC-300RCX

Nila Mae Apares

Rowida Asgali

Paul Cabuguason

Cris Matthew Geli

Jhonnielyn Joy Fidel

Jermaine Lamboso

University of St. La Salle

CHAPTER 1

INTRODUCTION

Background of the Study

In the Philippines, a carinderia is the common term for an eating establishment that

serves native food whose clients usually consist of the Filipino masses (Baga-Reyes, 2008).

Aside from local Filipino food, almost every carinderia serves soft drinks which are considered

as the most popular beverage in the country today. In fact, an average of 151 8-ounce servings of

soft drinks is consumed by an average Filipino in a year, which is greater than the global average

of 77 servings (Santiago, 2012). Soft drinks are always served cold, and it is for this reason that

soft drinks manufacturers offer a refrigerator to go with the purchase of soft drinks by

carinderias, restaurants, and other establishments (Coca-Cola, 2015). Coca-Cola is the leading

brand of soft drinks present in the country today (Santiago, 2012), and this paper aims to

determine the performance of the refrigerators that the Coca-Cola Company provides to its client

carinderias and eateries. A carinderia is first and foremost a business venture, thus it is worthy

to note the performance of its assets, like its refrigerator, in order to evaluate this asset‟s

profitability and value to the business (Neely, 2002).

Objectives of the Study

The primary objective of this study is to determine the coefficient of performance of

Coca-Cola refrigerated showcase model CCC-300RCX. Specifically, it aims to:

1.) Determine the heat removed (Qc) from the refrigerator interior by measuring the

change in temperature (ΔT) of 80 cups of water with known mass and specific heat

values at a certain time interval.

2.) Determine the power consumption (W) for the same time interval using a wattmeter.

3.) Calculate the coefficient of performance by dividing the heat removed by the power

consumed (Qc/W).

Significance of the Study

This study may be significant to the following:

Eating establishments. Knowing the performance rating of the business‟s assets will

help the owners and investors in making decisions suited for the best interests of the business

especially in terms of profitability.

Soft drinks manufacturers. The soft drinks industry will have an idea which brand of

refrigerators they may entrust their product to, in order to assure that the quality of the product

does not degrade and at the same time ensure the economic practicability and the environmental

effects brought by the use of a certain type and model of refrigerator.

Refrigerator manufacturers. Knowing the efficiency of current models of refrigerators

in the market, manufacturers will have a basis for the production of the next generation of

refrigerators which can perform better and more efficient than its predecessors.

Students and teachers. Equipped with the knowledge on how to determine the

efficiency of the refrigerator, students will be able to understand the concepts that they have

learned in the classroom and apply it in real world situations. At the same time, it will be easy for

the teachers to instill the lessons in the student‟s mind if the students have experienced it

personally.

Scope and Limitations of the Study

The study is to be performed using three Coca-Cola refrigerators from three eating

establishments namely Cay‟s Place, Tyrone‟s, and Josh‟s Diner. Water inside a Styrofoam cup is

the substance used in the study as it is cheap and its specific heat can be easily determined by

calorimetry. Alcohol thermometers from the University of St. La Salle College Science

Laboratories are also used in the study. The wattmeter used is of the brand Ever, Model

DDS1607 static single phase two wire watt-hour meter, purchased from HKL Electrical Supply,

Bacolod City.

CHAPTER 2

REVIEW OF RELATED LITERATURE

Concept of Refrigeration

Refrigeration is defined as „the process of removal of heat from an enclosed space, or

from a substance, and rejecting it elsewhere for the primary purpose of lowering the temperature

of the enclosed space or substance and maintaining it at that lower temperature‟ (New World,

2015). Meanwhile, a refrigerator is any kind of enclosure whose interior temperature is kept

substantially lower than the surrounding environment (Hau, 2010). The term "refrigerator" was

coined by a Maryland engineer, Thomas Moore, in 1800 (Moore, 1803).

In a refrigerator, heat is virtually pumped from a lower temperature to a higher

temperature. According to the Second Law of Thermodynamics, this process can only be

performed with the aid of some external work. It is thus obvious that the supply of power is

regularly required to drive a refrigerator. The substance which works in a pump to extract heat

from a cold body and to deliver it to a hot body is known as the refrigerant (Chandra, 2010).

There are two general types of refrigeration systems mainly used. These are vapor-

compression refrigeration and absorption refrigeration. A vapor-compression system consists of

four components: a compressor, a condenser, an expansion valve (also called a throttle valve),

Figure 1. Heat flow in a refrigerator (Google Images, 2015)

and an evaporator, while absorption refrigeration consists of four main parts, namely the boiler

or generator, condenser, evaporator and the absorber (Hau, 2010). The Coca-Cola refrigerator

employed in the study is of the compression type. Figure 2 shows the typical vapor-compression

cycle.

Coefficient of Performance

The performance of a refrigerator is usually expressed in terms of its coefficient of

performance. It is defined as:

Coefficient of Performance (C P cW

where Qc is the heat removed from the inside of the refrigerator, and W is the power supplied to

the refrigerator (Boles, 2013).

The coefficient of performance (COP) is basically the ratio of the refrigeration effect to

energy input. The COP of a refrigerator decreases with decreasing refrigeration temperature and

(Equation 1)

Figure 2. Typical vapor-compression cycle (New World, 2015)

it can be greater than unity. That is, the amount of heat removed from the refrigerated space can

be greater than the amount of work input (Chandra, 2010).

An average commercial refrigerator with a small compressor size and operating under 5

hp (about 4kW) has a typical COP in the range of 1.1-2.9 (Apogee, 2015).

Heat removed from a refrigerator

The heat removed from the enclosed space in a refrigerator can be regarded as the heat

removed from the substance stored in it. For cooling without phase change, this can be treated as

the sensible heat removed from the substance as evidenced by its temperature change (Chandra,

2010). Thus, the heat removed from a refrigerator can be defined as:

c mC T

where Qc is the heat removed from the refrigerated space, m is the mass of the substance that is

cooled, and ΔT is the temperature change of the substance.

The study uses liquid water inside a Styrofoam cup as the substance to be cooled inside

the refrigerated space. The specific heat capacity of water has the value of 4.186 kJ/kg-K

(University of Southern California, 2015). The heat absorbed of the Styrofoam cup may be

neglected for the very nature of the substance as an insulator, whose specific heat is greatly less

than that of water and is actually almost comparable to air. Styrofoam is 0.27 cal/g-K and air is

0.24 cal/g-K (McCord, 2015).

Power consumption of a refrigerator

As mentioned earlier, power is needed to drive refrigeration. Electrical power supplied to

an appliance may be measured with the use of a watt-hour meter. Also called an electricity

(Equation 2)

meter, a watt-hour meter is an instrument which measures electrical energy consumed in watt-

hours of any given circuit in accumulated or average readings. This measuring device is usually

installed in residences and commercial establishments to determine the power consumption for

an elapsed period of time (Brittanica, 2015).

Coca-Cola Refrigerator Model CCC-300RCX

The table below summarizes the characteristics of Coca-Cola Refrigerator Model CCC-

300RCX as shown on a sticker inside the refrigerator.

Table A. Information about Coca-Cola Refrigerated Showcase Model CCC-300RCX

Coca-Cola Refrigerated Showcase Model CCC-300RCX

Rated Voltage 220-240 V

Rated Frequency 60 Hz

Phase Single

Weight 93.7 kg

Refrigerant R-134a

Amount 320 g

Running Current and Wattage 2.55 A, 525 W

Manufactured by Sanden Intercool Made in Thailand

CHAPTER 3

METHODOLOGY

Experimentation is done using three Coca-Cola refrigerators, Model CCC-300RCX, from

Josh‟s Diner at Barangay Alijis, Cay‟s Place at Barangay Singcang, and Tyrone‟s at Stingers‟

Foodcourt of the University of St. La Salle.

These are the steps on how the experiment is conducted:

1.) Empty the refrigerator.

2.) Take the initial temperature of the water and cup system.

3.) Connect the wattmeter to the refrigerator.

4.) Place 80 pieces of cups filled with a known volume of water inside the refrigerator. Place

thermometers in the water such that the thermometers do not touch the cup.

5.) Take the temperature of the water every 10 minutes until it reaches an hour.

6.) Take the power consumed based on the wattmeter reading.

The coefficient of erformance or COP can be derived to show that the working equation is

as follows:

C P

( gcup

) ( cups) ( . kJkg

( T

( gkg

( kJkWh

) ( W (Equation

Starting from

C P cW (Equation

but Qc = mCΔT (Equation 2)

where m - the mass of water

C - heat capacity of water as 4.186 kJ/kg

ΔT - temperature difference between the initial temperature of the cup and

the temperature reached after an hour of refrigeration

The unit for QC is kJ while W is expressed in kWh. Since C P has no unit, W should

be converted to kJ by using the conversion factor: 1kWh= 3600kJ. The equation is therefore be:

C P (mass of water per cup n kg) (number of cups) (specific heat of water ( T

( gkg

( kJkWh

) ( W (Equation

The Coca-Cola refrigerated showcase model CCC-300RCX has four levels. Each level

can hold 20 cups of water. Thus, the refrigerator is occupied by 80 cups completely filled with

water of volume 230 mL in each cup. The density of water at the ambient temperature of 25°C is

0.997044 g/mL (Handbook of Chemistry and Physics, 1972) which can be easily approximated

as 1 g/mL to simplify calculations; thus, the mass of the water in each cup is 230g. The final

working equation is thus:

C P ( gcup

) ( cups) ( . Jkg

( T

( gkg

( kJkWh

) ( W (Equation

CHAPTER 4

RESULTS AND DISCUSSION

This chapter tabulates and discusses the results obtained from the experiments. A

working equation has already been derived in the previous chapter which has the form:

C P

( gcup

) ( cups) ( . kJkg

( T

( gkg

( kJkWh

) ( W (Equation

A sample calculation for Trial , “Cay‟s Place” Sample is shown below.

C P ( gcup

) ( cups) ( . kJkg K

( K

( gkg

( kJkWh

) ( . kWh

C P .

Tables 1 up to 3 tabulate experimental data for the three sample refrigerators. Table 4

shows the average values for each refrigerator.

Table 1. Recorded data from “Cay‟s Place” refrigerator

Trial

Tinitial

(oC)

TFinal (oC)

T(oC)

W

(kWh) COP

0 min 10

min

20

min

30

min

40

min

50

min

60

min

1 30 27 25 23 21 19 18 12 0.19 1.35

2 30 27 26 24 22 20 19 11 0.20 1.18

3 30 26 25 23 22 20 18 12 0.18 1.43

Table 2. Recorded data from “Tyrone‟s” Refrigerator

Trial

Tinitial

(oC)

TFinal (oC)

T(oC)

W

(kWh) COP

0 min 10

min

20

min

30

min

40

min

50

min 60 min

1 28 24 23 21 19 18 16.5 11.5 0.15 1.64

2 28 23 22 20 18 17 15 13 0.17 1.64

3 28 24 22 20 19 18 16 12 0.20 1.28

Table 3. Recorded data from “Josh‟s Diner” Refrigerator

Trial

Tinitial

(oC)

TFinal (oC)

T(oC)

W

(kWh) COP

0 min 10

min

20

min

30

min

40

min

50

min

60

min

1 28 25 22 20 18 16 14 14 0.18 1.66

2 28 24 23 21 19 17 15 13 0.20 1.39

3 28 25 23 22 19 17 14 14 0.18 1.66

Table 4. Average COP from the three refrigerators

Sample Refrigerator COPave

Cay‟s 1.32

Josh‟s 1.52

Tyrone‟s 1.57

Average 1.47

CHAPTER 5

Summary, Conclusions, and Recommendations

The objective of this study is to determine the coefficient of performance (COP) of a

Coca-Cola refrigerator Model CCC-300RCX by taking the temperature drops of a cooled cup of

water at a period of 1 hour to determine the heat removed (Qc) and by using a watt-hour meter to

determine the power consumption (W) at this time interval. A total of 3 trials each are performed

for each of the 3 refrigerators, yielding 9 values of COP. This is then averaged to obtain a final

single value.

The study has succeeded in determining the coefficient of performance, the ratio of Qc

and W, of a Coca-Cola refrigerator Model CCC-300RCX with an obtained average value of

1.47. This shows that the heat removed from the interior of the refrigerator is 1.47 times the

supplied electrical power at a period of time. This is within the range of the typical value of a

small commercial refrigerator type with a compressor operating less than 4 kW of 1.1-2.9

(Apogee, 2015).

Further studies may be conducted in the future that employs an alternative method to the

one used in the study. An investigation of the refrigerant properties through the cycle may be a

starting point for another study to determine the coefficient of performance (COP). Furthermore,

the validity of using the coefficient of performance (COP) as the basis for the performance of

refrigerators may also be delved into. Other types of bases are available such as the energy

efficiency ratio (EER), seasonal energy efficiency ratio (SEER), tons of refrigeration, and etc.

may also be a starting point for further studies and experimentation.

References

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APPENDIX

Information about the refrigerator Watt-hour meter used in the experiment

Sample experimental set-up for the three trials