Memoria Investigaciones en Ingeniería, núm. 29 (2025). pp. 131-151

https://doi.org/10.36561/ING.29.9

ISSN 2301-1092 • ISSN (en línea) 2301-1106 – Universidad de Montevideo, Uruguay

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131

Optimizing Domestic Refrigerator Performance with Varied Lubricants for

R134a Refrigerant: Comparative Analysis

Optimización del rendimiento del refrigerador doméstico con lubricantes variados

para el refrigerante R134a: un análisis comparativo

Otimização do desempenho de refrigeradores domésticos com diferentes

lubrificantes para o refrigerante R134a: análise comparativa

Muhammad Ehtesham ul Haque

(*), Abdul Samad Khan

, Adeel Ahmed Khan

, Muhammad Anus Irshad

Recibido: 28/05/2025 Aceptado: 24/07/2025

Summary. - The efficiency and performance of domestic refrigerators don’t only depend on refrigerant but also on

lubricating oil used in the refrigerator compressor. The lubricant of the compressor is responsible for the absorption of

heat energy evolved during the compressor work. The primary objective of this study is to examine and compare the

effects of two distinct lubricating oils utilized with the refrigerant R134a on various performance metrics of the

domestic refrigerator compressor, including evaporator capacity, compressor power consumption, and the coefficient

of performance (COP) of the refrigerator. These performance parameters were compared for two different cases, viz.,

domestic refrigerator having R134a as a refrigerant with Mineral oil (MO) and Polyol ester oil (POE), and for two

different methods such as manually by using R134a ph chart and EES software. The tests were conducted on a 329-

liter refrigerating capacity double-door refrigerator. The effect of changing oil from MO to POE resulted in the

increment of evaporator capacity from 1.81 kW to 1.99 kW and COP from 4.9 to 5.7 while the compressor power

consumption reduced from 370 watts to 340 watts which concluded that POE oil is the better lubricant in the domestic

compressor as compared to MO.

Keywords: Lubricants, Polyol ester oil, Mineral oil, R-134a, EES, Domestic refrigerator.

Assistant Professor, Department of Mechanical Engineering, NED University of Engineering & Technology (Pakistan),

mailto:mehaque@neduet.edu.pk, ORCID iD: https://orcid.org/0000-0001-8751-348X

Lecturer, Department of Mechanical Engineering, NED University of Engineering & Technology (Pakistan),

abdulsamadkhan@neduet.edu.pk, ORCID iD: https://orcid.org/0009-0005-5449-635X

Assistant Professor, Department of Mechanical Engineering, NED University of Engineering & Technology (Pakistan),

adeelahmedk@neduet.edu.pk, ORCID iD: https://orcid.org/0009-0004-6790-8176

Lecturer, Department of Mechanical Engineering, NED University of Engineering & Technology (Pakistan),

mailto:muhammadanus@neduet.edu.pk, ORCID iD: https://orcid.org/0009-0006-8193-4287

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Resumen. - La eficiencia y el rendimiento de los refrigeradores domésticos no solo dependen del refrigerante, sino

también del aceite lubricante utilizado en el compresor. El lubricante del compresor es responsable de la absorción

de la energía térmica desarrollada durante el trabajo del compresor. El objetivo principal de este estudio es investigar

y comparar el efecto de dos aceites lubricantes diferentes utilizados con el refrigerante R134a en varios parámetros

de rendimiento del compresor del refrigerador doméstico, como la capacidad del evaporador, el consumo de energía

del compresor y, por último, pero no menos importante, el COP del sistema de refrigeración. Estos parámetros de

rendimiento se compararon para dos casos diferentes: un refrigerador doméstico con R134a como refrigerante, aceite

mineral (MO) y aceite de polioléster (POE), y para dos métodos diferentes, como el manual mediante el uso de una

tabla de pH del R134a y el software EES. Las pruebas se realizaron en un refrigerador de doble puerta con capacidad

de refrigeración de 329 litros. El efecto de cambiar el aceite de MO a POE resultó en el incremento de la capacidad

del evaporador de 1,81 kW a 1,99 kW y el COP de 4,9 a 5,7 mientras que el consumo de energía del compresor se

redujo de 370 vatios a 340 vatios, lo que concluyó que el aceite POE es el mejor lubricante en el compresor doméstico

en comparación con MO.

Palabras clave: Lubricantes, Aceite de polioléster, Aceite mineral, R-134a, EES, Refrigerador doméstico.

Resumo. - A eficiência e o desempenho de refrigeradores domésticos dependem não apenas do refrigerante, mas

também do óleo lubrificante utilizado no compressor. O lubrificante do compressor é responsável pela absorção da

energia térmica liberada durante o funcionamento do compressor. O principal objetivo deste estudo é examinar e

comparar os efeitos de dois óleos lubrificantes distintos, utilizados com o refrigerante R134a, em diversas métricas de

desempenho do compressor de um refrigerador doméstico, incluindo a capacidade do evaporador, o consumo de

energia do compressor e o coeficiente de desempenho (COP) do refrigerador. Esses parâmetros de desempenho foram

comparados em dois casos diferentes: um refrigerador doméstico com R134a como refrigerante, utilizando óleo

mineral (MO) e óleo de éster de poliol (POE), e por dois métodos distintos: manualmente, utilizando a tabela de pH

do R134a, e por meio do software EES. Os testes foram realizados em um refrigerador de duas portas com capacidade

de refrigeração de 329 litros. A mudança do óleo de MO para POE resultou no aumento da capacidade do evaporador

de 1,81 kW para 1,99 kW e do COP de 4,9 para 5,7, enquanto o consumo de energia do compressor reduziu de 370

watts para 340 watts, concluindo-se que o óleo POE é um lubrificante melhor para compressores domésticos em

comparação com o MO.

Palavras-chave: Lubrificantes, óleo éster de poliol, óleo mineral, R-134a, EES, refrigerador doméstico.

M. Ehtesham ul Haque, A. Samad Khan, A. Ahmed Khan, M. Anus Irshad

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1. Introduction. - There are many challenges facing energy conservation and environmental protection today, and how

energy is supplied and consumed, both practices require major changes (Allouhi et al., 2015). Energy conservation has

recently emerged as an important social issue. It involves efforts to reduce energy consumption by utilizing less energy-

intensive services and ensuring more efficient equipment management (Ollukkaran & Sreedharan, 2023). According

to the Montreal and Kyoto treaties, home refrigerators are the main source of emissions of the fluorine and chlorine

gases which are present in refrigerants. These emissions contribute significantly to the degradation of the ozone layer

and the acceleration of global warming. The release of chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs)

from these appliances leads to increased ultraviolet radiation reaching the Earth's surface. This not only harms

ecosystems and human health but also exacerbates climate change by trapping heat in the atmosphere. . Nowadays,

Ozone Depletion (OD) and Global Warming (GW) are increasing day by day (Khan, ul Haque, Khan, Obaidullah, &

Khan, 2024), and refrigerant compounds such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and

hydrofluorocarbons (HFCs) are responsible (Damola S. Adelekan et al., 2017). Previously, refrigeration systems

commonly used hydrochlorofluorocarbon (HCFC) refrigerants such as R12 (dichlorodifluoromethane) and R22

(chlorodifluoromethane). However, their use is now prohibited due to their ozone-depleting effects (Tada et al., 2016).

Researchers (D. S. Adelekan et al., 2021) examined the performance of an altered household refrigerator under varying

mass charges of R600a refrigerant, TiO2 nanoparticle concentrations, and ambient temperature conditions. The

refrigerator’s energy consumption at 0.2 g/L and 0.4 g/L concentrations of TiO2 nanolubricant was lowered by 0.13 to

14.09% in comparison to the baseline concentration (0 g/L). Utilizing 0.2 g/L of nanolubricant in the refrigerator, the

greatest coefficient of performance was reached with a 60g charge of R600a and at ambient temperature of 22°C.

A domestic refrigerator using R134a and LPG as the refrigerant was studied in 2018 with two different lubricants,

including POE, MO. It also investigated nano-oils comprising of TiO2, SiO2, and Al2O3, nanoparticles in combination

with MO. The results showed that compressor power consumption was 15.87% lower and the COP was 56.32% higher

than calculated for R134a/POE lubricant (Gill, Singh, Ohunakin, & Adelekan, 2018). In 2019, an experiment was

carried out to investigate the performance of a refrigeration system using an R134a/PAG oil mixture and

R134a/PAG/Al2O3 (R134a/nano-oil) mixture which shows that COP was increased by 6.5% after the addition of the

nanoparticles in the compressor (Nair, Parekh, & Tailor, 2020).

In 2019, an Energy analysis of a domestic refrigerator system with Artificial neural network (ANN) using different

concentration combinations of LPG/TiO2 – lubricant as a replacement for R134a was used and the findings revealed

that compressor power consumption and pressure ratio using LPG with nano-oil was 3.20–18.1 and 2.33–8.45%

respectively lower and the cooling capacity and COP was around 18.74–32.72 and 10.15–61.49% respectively higher

in comparison with R134a as a refrigerant (Gill, Singh, Ohunakin, & Adelekan, 2019). In 2019, hexagonal boron nitride

(h-BN) was used as a solid nanoparticle in POE with R134a as a refrigerant and the findings showed that using 3 vol%

of h-BN nanoparticle improved the energy saving by 60% in comparison with pure POE oil (Harichandran, Paulraj,

Maha Pon Raja, & Kalyana Raman, 2019). In 2021, the performance of a domestic refrigerator was investigated via

R134a with POE and R600a with nano-oil (MO with Al2O3) which resulted in an improvement of COP and compressor

discharge pressure by 37.2% and 8.9% respectively, and a reduction in power consumption and evaporator pressure by

28.7% and 24.7% respectively by using 0.1 wt.% of R600a with nano-oil (MO with Al2O3) as compared to the

conventional refrigeration system (Yogesh, Dinesh, & Sandeep, 2021). In 2022, authors investigated the performance

of the refrigeration cycle of a domestic refrigerator by adding ZrO2 nanoparticle of concentration 0.2 g/L in R134a

refrigerant and found out that by using nano-oil, the refrigeration capacity of the system was increased to 38.7%

(Baskaran, Manikandan, Tesfaye, Nagaprasad, & Krishnaraj, 2022).

An experimental comparison of a residential refrigerator's performance analysis using MO oil versus POE oil is needed

to determine which lubricant performs the best with R134a. The literature review indicates that there are no or very

little studies that compare the thermodynamic performance of home refrigerators using the same refrigerant but two

different lubricants, and a comparative analysis using EES. Chlorine in refrigerant compounds such as CFC and HCFC

is responsible for OD and GW. However, in this experimental research work, R-134a, which is an HFC compound, is

used. It is chlorine-free, making it environmentally feasible for the analysis. This study aims to perform the

M. Ehtesham ul Haque, A. Samad Khan, A. Ahmed Khan, M. Anus Irshad

Memoria Investigaciones en Ingeniería, núm. 29 (2025). pp. 131-151

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thermodynamic analysis experimentally of two different compressor lubricating oils to find the better lube oil which

can be used in a domestic refrigerator with the Refrigerant R134a, and comparative analysis was performed with the

EES Professional V10.4-3D software. The comparison was made based on performance parameters including COP,

compressor power consumption & evaporator cooling capacity.

2. Materials and Methods. -

2.1 Experimental setup. - The experiment conducted by utilization of an experimental setup consists of a double-door

domestic refrigerator with a gross capacity of 397 Litres. It includes a hermetic reciprocating type of compressor in

which HFC – R134a is used as a refrigerant with a charged mass of 190 grams, a dryer, a capillary tube, an air-cooled

condenser, and an evaporator. Table I represents the specification of the experimental setup.

Table I. Specification of the refrigerator.

Figure I shows the pressure gauges installed at the suction & discharge lines of the compressor while Figure II shows

temperature sensors at different locations within the refrigerator to record data in the data logger.

Figure I. Pressure gauge installed at compressor’s suction & discharge lines.

S/N

Refrigerator description

Units

Climate Class

Tropical

Protection Class

Storage Volume

329L

Freezer Volume

68L

Power rating

180W

Voltage/frequency rating

200-240V/50 Hz

Condenser type

Air cooled

Refrigerant type

R134a

Mass charge

190 g

Freezing Capacity

4kg/24 hr

Lamp rating

10 Watt

Overall size

620 x 600 x 1700 (mm)

Compressor type

Hermetic (HFC)

Number of doors

Double

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(a)

(b)

Figure II. Temperature sensors installed inside & outside of the refrigerator.

The overall experiment was performed by using two different lubricants that are MO and POE oil with the refrigerant

R134a for both oils. Table II represents the range of experimental setups while Table III & Table IV shows the

properties of the POE oil & MO.

Table II. Range of experimental conditions.

S/N

Parameter

Range of experiment

Refrigerant name

R – 134a

Refrigerant charge

190 g

Compressor Lubricant

POE

Lubricant charge

300 ml

Evaporator type

Air-cooled

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Table III. Characteristics of POE Oil.

Table IV. Characteristics of MO.

3. Performance analysis. -

3.1 Evaporator capacity. - The evaporative heat transfer rate through the refrigeration system was calculated

separately for the compressor, charged with MO and POE lubricants, respectively. The formula used for the

refrigeration effect is given by eq (1):

󰇗 󰇗 󰇛 󰇜 (1)

The refrigerant mass flow rate is calculated by eq (2):

󰇗  

󰇗

󰇛󰇜 (2)

In eq (1), h_4 & h_5 represents the enthalpies at evaporator inlet and commencement of superheating of the refrigerant.

In eq (2), h_1 & h_2 represents the enthalpies at compressor inlet and compressor outlet/condenser inlet while W _comp

indicates the compressor power consumption.

3.2 Compressor power consumption. - The data logger which was used to record experimental readings at different

locations inside and outside the refrigerator can also measure voltage and current consumed by the compressor during

the time interval when the refrigerator was in operation. The power consumed by the compressor can be calculated by

the eq (3):

  󰇛󰇜 (3)

S/N

Lubricating oil characteristics

Units

Oil Type

POE

Density at 15°C kg/L

0.980

Kinematic viscosity @ 40°C

32.0 cSt

Kinematic viscosity @ 100°C

5.8 cSt

Viscosity index

125

Flash Point

235 °C

Pour Point

– 48 °C

Cu Corrosion @ 100°C x 3 hrs

Water ppm

<100

S/N

Lubricating oil characteristics

Units

Oil Type

Density at 15°C kg/L

0.916

Kinematic viscosity @ 40°C

55 cSt

Kinematic viscosity @ 100°C

5.9 cSt

Viscosity index

Flash Point

179 °C

Pour Point

– 35 °C

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3.3 COP. - The actual COP values for the VCRS were evaluated using EES software by first charging the compressor

with MO, and the same procedure was repeated for POE lubricating oil. The COP values obtained were validated

against the COP values calculated using ASHRAE Ph Chart for HFC R – 134a (Handbook, 2017).

To determine the COP for the refrigerator, the temperature sensors were attached at different positions to the refrigerator

itself, and the temperature readings were recorded using a data logger. In contrast, the pressure at the suction and

discharge of the compressor was noted by operating the two pressure gauges after every five minutes. The temperature

and pressure readings were recorded for the entire day, but average values were used in the calculation. Figure III shows

the schematic diagram of the refrigerator with a data logger for data measurement.

Figure III. Schematic diagram of a refrigerator showing temperature sensors and data logger.

The COP of the domestic refrigerator is given by eq (4):

  󰇗



󰇗 (4)

3.4 Compressor & evaporator temperatures. - The compressor was charged with two different lubricants, MO, and

a synthetic lubricant, each time with the same amount of refrigerant, i.e., HFC R – 134a. To compute the effect on

refrigerator performance by using two different lubricating oils, the performance parameters such as compressor suction

& discharge pressures & temperatures and compressor dome temperatures were recorded during the time interval when

the refrigerator was in operation. In the first step, the compressor was charged with 190 grams of R134a and 300 ml of

MO. The compressor was charged again with the same amount of refrigerant for the second run, using 300 ml of POE.

Figure IV depicts the placement of the temperature sensors at the compressor dome.

The experimental setup consists of ten DS18B20 digital temperature sensors, each utilized to obtain internal freezer

compartment temperatures using the data logger alongside time, voltage, and current. Figure V depicts the placement

of temperature sensors. Temperature readings were taken twice for the bottom and right-side walls of the freezer

compartment while changing the compressor lubricant from MO to POE oil.

M. Ehtesham ul Haque, A. Samad Khan, A. Ahmed Khan, M. Anus Irshad

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Figure IV. Placement of temperature sensors at compressor dome

(a) (b)

Figure V. Placement of temperature sensors in the freezer compartment

4. Results and Discussion. - The investigation involved a double-door domestic refrigerator which used two different

lubricants, mineral oil (MO) and polyolester (POE) oil. HFC R-134a performance was evaluated using the ASHRAE

pressure-enthalpy (P-h) chart and Engineering Equation Solver (EES) software.

4.1 Calculation of COP by using P-h chart. - The refrigeration cycle was hand-drawn on the R134a Ph chart by using

the average values of temperature and pressure recorded during the experiments. The COP is then calculated and listed

in Table V for both lubricating oils. Figure VI depicts the calculated COP values while Figure VII & Figure VIII

represents the refrigeration cycle on the R134a Ph chart for MO & POE oil respectively.

Table V. COP values for MO & POE lubricants using R134a ph chart.

Figure VI. COP (MO vs POE oil).

S/N

Refrigerant

Lubricating oil

COP

HFC R134a

4.958

POE

5.795

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Figure VII. Refrigeration cycle on R134a Ph chart for MO

Figure VIII. Refrigeration cycle on R134a Ph chart for POE oil

R-134a and the majority of HFC refrigerants do not mix well with mineral oil. For this reason, the evaporator and pipes

retain oil as a result of this poor miscibility. These retained mineral oil acts as an insulator and hinders in the heat

transfer (Sundaresan, Judge, Chu, & Radermacher, 1996). On the other hand, POE oil and R-134a mix quite well. By

circulating with the refrigerant, it improves heat transfer and lessens oil logging in the evaporator. As a result of this

better miscibility of POE oil with R-134, more effective evaporation and condensation occur which improves the COP

value.

As compared to mineral oil, POE oil has superior lubricity under high pressure and high temperature condition which

is common in the R-134 compressor (Sundaresan, Pate, Doerr, & Ray, 1996).

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4.2 Compressor power consumption. - The power consumed by the compressor when it is charged with POE oil came

out to be less than it is consumed by the compressor using MO as a lubricant. The compressor voltage and current data

were obtained using the data logger. Table VI represents the average current & power consumed by the compressor

when using MO & POE oil. Figure IX depicts the compressor power consumption recorded by data logger; Figure X

shows the graph representing the current drawn by the compressor while Figure XI depicts the bar chart showing the

compressor average power consumption when both the oils were used.

Table VI. Average Current & Power consumed using MO & POE oil.

Figure IX. Compressor power consumption.

Figure X. Average current drawn (MO vs POE oil).

S/N

Refrigerant

Lubricating oil

Average Current

(Ampere)

Average Power

(Watts)

HFC R134a

1.535

370.91

POE

1.391

340.62

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Figure XI. Average power consumption (MO vs POE oil).

POE oils are outstanding lubricants in high-temperature, high-pressure environments, which are typical in HFC

systems. This characteristic results in reduced mechanical friction and weir losses in the compressor. A lower frictional

loss reduces the power requirement of the compressor and hence higher COP values are achieved.

4.3 Evaporator capacity. - By using eq (1) & eq (2), the mass flow rate and refrigeration effect of the refrigerant can

be calculated easily which is also shown in Table VII. Figure XII depicts the bar chart representing the evaporator

capacities when both the oils i.e., POE and MO were used in the experiment.

Table VII. Evaporator cooling capacity using MO & POE oil.

Figure XII. Evaporator cooling capacity (MO vs POE oil).

S/N

Refrigerant

Lubricating oil

Mass flowrate

(kg/s)

Evaporator capacity

(Kilowatts)

HFC R134a

0.0152

1.8171

POE

0.0156

1.9992

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4.4 Compressor & evaporator temperatures. - Table VIII represents the thermophysical properties of MO and POE

lubricants. The temperature and pressure were measured several times, and the average readings were used for

calculations. The DS18B20 temperature sensors used in this setup have a measurement range of -55°C to 125°C with

an accuracy of ±0.5 °C.

Table VIII. Thermophysical properties for MO and POE lubricants.

Table IX shows average experimental data using MO and POE lubricants. It is evident that POE has a lower compressor

temperature difference leading to lower compressor ratio which means compressor doesn’t have to work as hard to

compress the refrigerant. Less heat is generated during compression, leading to lower operating temperatures within

the compressor. Cooler operating temperatures help prevent overheating and thermal degradation of compressor

components, contributing to increased reliability and longevity.

Table IX. Experimental data using MO and POE lubricants.

Table X represents the average evaporator temperatures and compressor dome temperature using MO & POE

lubricating oils. Figure XIII, Figure XIV and Figure XV represent the graphs of evaporator right and bottom side walls

and compressor dome temperatures recorded by data logger when both the oils were used in the compressor for analysis.

Table X. Temperature data using MO & POE lubricating oils.

S/N

Lube oil

Viscosity at

40 ºC (cSt)

Viscosity at 100

ºC (cSt)

Flash point

(ºC)

Density at 15ºC

(kg/L)

5.9

179

0.916

POE

5.8

235

0.980

S/N

Lube oil

Pressure (bar)

Temperature (ºC)

Compressor

Suction

Compressor

discharge

Compressor

suction

Compressor

discharge

Condenser

outlet

1.2

31.06

83.98

POE

36.23

82.98

39.72

S/N

Lube oil

Temperature (ºC)

Evaporator Right

side wall

Evaporator Bottom

side floor

Compressor dome

1.165

-3.560

89.3

POE

-6.794

-6.140

98.9

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Figure XIII. Evaporator right side wall temperature.

Figure XIV. Evaporator bottom side wall temperature.

Figure XV. Compressor dome temperature.

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The COP of the refrigerator is greater when POE oil is used, as opposed to when mineral oil is used. Because POE oil

mixes better with R-134a, decreases heat exchanger oil film development, increases heat transfer, provides dependable

oil return, and lowers compressor mechanical losses.

5. Validation by EES Software. -

5.1 Mineral Oil. - The performance analysis results are compared and validated by EES software. Three parameters of

the present work, i.e., COP, refrigeration effect, and compressor power are validated with the EES software. Figure

XVI shows the validation results i.e., COP, compressor power & evaporator capacity of the refrigeration system when

using MO with R134a as a refrigerant. Figure XVII & Figure XVIII shows the ph & T-s plots for MO given by EES.

Figure XVI. Validation of MO by EES software.

Figure XVII. ph plot for MO by EES software.

Figure XVIII. T-s plot for MO by EES software.

M. Ehtesham ul Haque, A. Samad Khan, A. Ahmed Khan, M. Anus Irshad

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When compared with the values obtained from the ph chart in tables V, VI, and VII, it is evident that the EES software

values validate the values obtained from the ph chart.

5.2 POE Oil. – Figure XIX depicts the validation results i.e., COP, compressor power & evaporator capacity of the

refrigeration system when using POE oil with R134a as a refrigerant. Also, Figure XX & Figure XXI shows the ph &

T-s plots for POE oil given by EES.

Figure XIX. Validation of Mineral Oil by EES software.

Figure XX. ph plot for POE oil by EES software.

Figure XXI. T-s plot for POE oil by EES software.

M. Ehtesham ul Haque, A. Samad Khan, A. Ahmed Khan, M. Anus Irshad

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5.3 Comparison of the results. - The COP, compressor power consumption & refrigeration effect of the refrigeration

system with two different lubricating oils with the same refrigerant R134a using two different methods i.e., EES

software and R134a Ph chart are listed in Table XI.

Table XI. Comparison of the performance parameters.

The percentage errors between the two methods i.e by using the R-134a ph chart and EES software for COP, compressor

power and evaporator capacity are shown in Table XII.

Table XII. Percentage error.

Figure XXII, Figure XXIII, and Figure XXIV represent the 3D graphs showing COP, compressor power consumption,

and refrigeration effects when using both oils, i.e., POE and MO, and both methods, R-134a and EES software. This

allows for an easy comparison of values at a glance.

S/N

Compressor

Lube oil

COP

Compressor power (kW)

Evaporator capacity

(kW)

ph chart

EES

ph chart

EES

ph chart

EES

4.958

4.523

0.370

0.400

1.8171

1.812

POE

5.795

5.781

0.340

0.343

1.9992

1.983

S/N

Compressor Lube oil

Parameters

% Error

COP

9.6

Compressor Power

7.5

Evaporator Capacity

0.28

POE

COP

0.24

Compressor Power

0.87

Evaporator Capacity

0.81

M. Ehtesham ul Haque, A. Samad Khan, A. Ahmed Khan, M. Anus Irshad

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Figure XXII. COP (R134a ph chart vs EES).

Figure XXIII. Compressor Power consumption (R134a ph chart vs EES).

Figure XXIV. Refrigeration effect (R134a ph chart vs EES).

M. Ehtesham ul Haque, A. Samad Khan, A. Ahmed Khan, M. Anus Irshad

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6. Conclusion. - Based on the experimental investigation and performance analysis of the domestic refrigerator using

two different compressor lubricating oils i.e., Mineral Oil and POE oil, the following conclusions are noted keeping in

mind the comparative analysis of the lubricating oil performance parameters with the same refrigerant R134a:

a. COP (Coefficient of Performance) is used to measure the efficiency of vapor compression refrigeration systems.

The COP values were obtained manually using the ASHRAE Ph chart for R134a and validated by the EES program

while using two different compressor lubricants, i.e., MO and POE. The error associated with these two methods

is very less, as observed in Table XI. From Figure XXII, it is evident that the COP value obtained for MO is

significantly less when compared to the COP value for POE; this is because of increased refrigeration effect as

shown in Figure XXIV.

b. From Figure XI, it is evident that there is a considerable reduction in compressor power consumption while using

POE lubricant. Around 30 watts less power is consumed when the compressor is shifted from MO to POE which

is also depicted in Table XI. The difference in power consumed is due to enhanced lubricity. Changing the lubricant

has significantly reduced the current consumed by the compressor, which is evident from Figure X.

c. Since refrigerant R134a is miscible with POE oil used, there is an increase in refrigeration from 1.817 KJ/s to

1.999 KJ/s. Moreover, the mass flow rate calculated is approximately the same using two different lubricants.

Therefore, the increase in evaporator capacity indicated in Figure XII is due to an increase in the heat transfer rate

from the air to the refrigerant in the evaporator.

d. The lubricant’s thermophysical properties significantly impact refrigerator performance parameters. The properties

of both lubricants are listed in the Table IX depict that MO will be carried along with the refrigerant into the system

in more significant amounts, compared to POE, due to its decreased flash point and density. The oil inside the

evaporator and condenser significantly decreases the heat transfer rate by creating an insulating effect. In contrast,

POE oil has a high return rate to the compressor due to its miscibility with R134a. From Table IX, the increase in

compressor suction temperature when POE is used suggests that heat transfer through the evaporator has enhanced.

Hence, the refrigerant returned to the compressor has a high temperature. A similar effect can be observed for

condenser outlet temperature.

e. The lowest shell temperature, i.e., 111 ºC, is obtained for the compressor charged with R134a and MO mixture

indicated in Table X. In contrast, in Figure XV, the comparatively higher temperature curve shown in red is for

the compressor charged with POE. The increase in compressor dome temperature is due to more excellent heat

dissipation from the shell.

Experimental work and theoretical studies have been carried out in this research to investigate the performance of a

VCRS using two different classes of compressor lubricants, namely MO and POE oil. Lubricant effects on system

performance are easily measurable, as evidenced by the difference in performance parameters evaluated such as COP,

evaporator capacity & compressor power consumption. The miscible POE oil outperformed an immiscible MO with

R134a refrigerant. From Table XI, it could be concluded that the COP value obtained is higher for POE oil, implying

that the factor of miscibility has positive effects on system performance. System reliability should not be the only

priority when selecting a compressor lubricant but also enhanced system performance and efficiency.

M. Ehtesham ul Haque, A. Samad Khan, A. Ahmed Khan, M. Anus Irshad 
 
 
Memoria Investigaciones en Ingeniería, núm. 29 (2025). pp. 131-151 
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Author contribution:

1. Conception and design of the study

2. Data acquisition

3. Data analysis

4. Discussion of the results

5. Writing of the manuscript

6. Approval of the last version of the manuscript

MEuH has contributed to: 1, 2, 3 4, 5 and 6.

ASK has contributed to: 1, 2, 3 4, 5 and 6.

AAK has contributed to: 1, 2, 3 4, 5 and 6.

MAI has contributed to: 1, 2, 3 4, 5 and 6.

Acceptance Note: This article was approved by the journal editors Dr. Rafael Sotelo and Mag. Ing. Fernando A.

Hernández Gobertti.