Improvement Of Performance of Refrigeration System Using Hydrocarbon Refrigerant Mixed with Cryogenically Treated Sic Nanopowder

Senthilkumar D

Published on: 2024-08-25

Abstract

This paper deals with the development of performance of domestic vapour compression refrigeration system using the hydrocarbon refrigerant R600a and R290, hydrocarbon refrigerant (R600a and R290) with SiC nano powder and hydrocarbon refrigerant (R600a and R290) with cryogenically treated SiC nano powder. Generally, hydrocarbon refrigerant is used as working fluid in domestic refrigeration. The Coefficient of performance, freezing capacity is increased by dispersing the SiC nanopowder in hydrocarbon refrigerant. Moreover, the cryogenic treatment was also done on SiC nano powder to improve the performance of the system. Cryogenic treatment is a cold treatment done on SiC nano powder at -196° C for 24 hours. Due to this treatment, the further improvement on COP and freezing capacity were observed. The power consumption of refrigeration system was also reduced when compared with conventional refrigeration system. In this work the performance of the refrigerator using nano refrigerant is to be analysed.

Keywords

Cryogenically; Nanopowder; curaua; Hydrocarbon

Introduction

Presently, the thinning of ozone layer in the atmosphere is a major environmental issue happening in the universe. It affects living beings introducing diseases. Global warming is also an environmental concern, which focus our attention to address the issue. Refrigerator is one of the essential system used in every house-holds. The chlorine atoms present in the refrigerant is one of the reason for ozone depletion. Therefore, chloro fluoro carbon (CFC), hydro fluoro carbon (HFC) should be phased out according to Montreal protocol and Kigali amendment as stated by A. Peyyala et.al. The hydrocarbon refrigerant mixtures are having zero ozone depletion potential (ODP) and Global warming potential (GWP ) is 5. According to Agrawal, Patil, Nanda, (2017) [1], it is found that the zeotropic blend R290/R600a hydrocarbon refrigerant gives better COP with respect to the COP of R134 a and also this R290/R600a refrigerant consumes lesser power compared to hydro fluoro carbon refrigerant R134a system.

The demand for the electrical energy is increasing enormously. Seventeen percent of electricity is used for refrigeration world-wide, 45% of electricity out of 17% is used in the houses [2]. The cost of the electricity is also increasing day by day. Scientist and Researchers are trying to increase the performance of the refrigeration system and also to lower the power consumption. The vapour compression refrigeration systems are used in hospitals, hotels, complexes, cold rooms, refrigerated trucks, rails, cars, food industries, oil refineries, chemical processing plants and industrial plants, etc. Domestic Refrigerators are mostly manufacturing using the principle of vapour compression refrigeration system. Four components are mainly used in this type of system namely compressor, condenser, evaporator and expansion valve. The working fluid or refrigerant having low boiling point is used to cool the body at around 0 – 4°C. The working fluid plays a major role on refrigerating effect. Now-a-days, for improving the COP of refrigerator, nanopowder is mixed in the refrigerant. Lal Kundan and Kuljeet Singh, 2021 [3] have studied the COP of a refrigerator with the refrigerant R134a and with the nano refrigerant R134a + Al₂O₃ nano powder. The increase in COP of refrigerator is varied from 7.2% to 16.34% when nano refrigerant is used as working fluid. Nano refrigerant is the refrigerant dispersed with nano powder. Generally, nano powders are dispersed in a fluid called nano fluid, which enhances the heat transfer due to increase in thermal conductivity. Researchers found that the nano powders are used to improve COP of the refrigeration systems. A scientific literature stated that the thermal conductivity of Al₂O₃ /R141 nano refrigerant increases when the volume fractions are increased [4]. The increase in thermal conductivity which leads to increase in COP of the refrigeration system. The nano refrigerant has potential to increase thermo physical properties and enhance heat transfer rate of working fluid. Nano refrigerants improves the refrigeration effect of the refrigerant system. thermal conductivity of water is increased by dispersing SiC nanopowder in water. Brownian motion of the nanoparticles is responsible for the improvement in thermal conductivity as stated by Senthilkumar.D, Chaiwat Jumpholkul and Somchai Wongwises [5].

Cryogenic treatment of nano powder is also made influence over the refrigerating effect. Cryogenic treatment is one of the method adopted to cool the material which below – 196° C. This material will alter the microstructure which helps to enhance the thermal conductivity of the material. Therefore, the further enhancement in COP was being happened. So the treatment of nano powder used in the refrigerant can influence the performance of the refrigeration system to get better COP.

The aim of the present research work is to investigate the influence of SiC nano powder with the hydrocarbon refrigerant (R600a and R290) in vapour compression refrigeration system. The COP, freezing capacity and power consumption are found out and compared with conventional refrigeration (R600a and R290) system. Also, the cryogenic treatment is done on SiC nanopowder and the results were compared with conventional and nano refrigerant. The cryogenically treated SiC nanopowder with hydrocarbon refrigerant will give better COP, freezing capacity and power consumption.

Experimental Investigations

The research methodology of the present research work is as shown in the figure 1. The commercially available hydrocarbon mixture of the refrigerant (R600a and R290) container is shown in the figure 2.

Figure 1: Research Methodology.

Refrigerant

The ozone depletion for Hydorcarbon refrigerant is zero and the global warming potential is less than 5. The properties of refrigerants R600a, R290 and the mixture (R600a&R290) is tabulated in Table 1. The refrigerant mixture is commercially available and it is stored in a container as shown in figure 2.

Figure 2: R600a & R290 refrigerant container.

Table 1: Comparison with other refrigerants.

Description	R600a	R290	Mix(R600a&R290)
Net boiling point (?)	-11.7	-42.1	32.47
Molecular weight(g/mol)	58.12	44.1	50.147
Critical temperature (?)	134.7	96.7	116.7
Critical pressure (MPa)	3.64	4.25	4.128
Liquid density(kg/m³)	225.49	220.47	219.5

The procured SiC nano powder is as shown in figure 3. The nano refrigerants are prepared by mixing the SiC nano powder in the refrigerant mixture R600a&R290. Both SiC nano powder and the refrigerant mixture was stored in a tin. First, the empty tin as connected to the vacuum compressor. After vacuum process was over, One side was connected to the charging cable and the other side is connected to HCR full tin. SiC nano powder added in the charging line. The full tin valve was opened. The nano powder is flown with the HCR mixture and stored in tin. Next, Sonication process was done on the prepared nano refrigerants using the device ultrasonic sonicator. The dispersion of nano powder takes place during the sonication process. The weight fractions of 0.1%, 0.2% and 0.3% of both conventional silicon carbide nano powder and cryogenically treated silicon carbide nano powder are mixed separately in each container. The nanoparticles remain in circulation with the refrigerant.

Figure 3: SiC nanopowder.

Test Procedure

The experiments were carried out in a 170 litres capacity domestic refrigerator. The refrigeration system is vacuumed first and then the nitrogen gas is filled in the system to check whether any leak was occurred. Then the nitrogen gas purged from the system. After charging the hydrocarbon mixture, two kilogram of water is kept inside the freezer. The system was started. The cooling rate of water is measured using thermometer at one-hour intervals and the temperature of the freezer tank is also observed for the regular intervals. Then the pressure and temperatures of suction and discharge lines are noted down. The current and voltage required to run the compressor is also noted down. The readings are observed for R600a & R290 refrigerant and also for SiC and Cryogenic SiC nanoparticles refrigerants for each weight ratio of 0.1%, 0.2%, 0.3%. The pressure gauges p1 and p2 were installed in the suction and discharge line of the compressor. The range of pressure gauges p1 and p2 are 0-300 psi and 0-500 psi. The temperature sensors t1, t2, t3, t4, tw were fixed at suction line, discharge line, condenser, freezer and also in the water respectively. The temperature and pressures are noted at the various points of vapour compression refrigeration cycle. The position of the temperature and pressure sensors are shown in figure 4. The voltmeter (0-500V) and ammeter (0-5A) are also used to find the voltage and current of the compressor, from which the power consumption of the refrigerator was determined. The experimental set up is as shown in the figure 5.

Figure 4: Temperature sensors and pressure gauges’ positons.

Figure 5: Experimental setup.

The coefficient of performance (COP) is calculated for the three types of refrigerants using the equation (1).

COP=R.E/P.I (1)

where,

E=Refrigeration effect

P.I =Power Input of compressor

R.E=mcp?T/t (2)

where,

m = mass of the water in “kg”

cp = coefficient of pressure of water

?T = temperature difference of water in “?c”

t = Time in “sec”

The power input is calculated using equation (3)

P.I=V*I/1000 (3)

where,

V=voltage in “v”

I=current in “A”

Substituting equation (2) and (3) in (1) we get:

[mcp?T/t]/ [V*I/1000]

Results and Discussion

The comparative analysis of the three types of refrigerants on the performance of the domestic refrigerator are discussed as follows,

The COP vs. Time is plotted and shown in figure 6. The COP of the refrigerant R600 & R290/SiC and R600a & R290/cryo SiC is higher when compared with the standard R600a & R290 refrigerant. Brownian motion is the irregular movement of the nano particles. The Brownian motion of the nano particles is responsible for the increase in thermal conductivity as stated by Senthilkumar.D, Chaiwat Jumpholkul and Somchai Wongwises [5]. Hence the nano powder mixed with the refrigerant increases the performance of the refrigerant system as stated by Senthilkumar ,2019 [6].

The COP of nano refrigerant R600a & R290/SiC is increased by 11.60% when compared to the conventional refrigerant (R600a & R290) and the average COP of the nano refrigerant R600a & R290/Cryo SiC is increased by 14.84% with respect to the conventional R600a & R290 as shown in the figure 7.

Figure 6: COP vs Time.

Figure 7: Coefficient Of Performance of various refrigerants.

Figure 8 shows the amount of power consumed by each weight ratio of nano refrigerants and the results shows that the power consumption of the refrigerator is decreased by 7.16% with nano refrigerant R600a & R290/SiC when compared to the conventional R600a & R290 and decreased by 8.97% when used with nano refrigerant R600a & R290/Cryo SiC when compared to the standard R600a & R290 refrigerant [7,8].

Figure 9 shows the freezing temperature of each weight ratio of the nano refrigerant when it is compared to the conventional R600a & R290 refrigerant. It shows that the freezing temperature of the refrigerator is increased by 8.33% for nano refrigerant R600a & R290/SiC with respect to conventional R600a & R290 refrigerant and increased by 10.64% for R600a & R290/Cryo SiC when compared to the conventional R600a & R290 refrigerant.

Figure 8: Power consumption.

Figure 9: Freezing Temperature Vs Time.

Figure 10 and 11 shows the suction and discharge pressures of each weight ratios of nano refrigerants in comparison to the conventional R600a & R290 refrigerant. It shows the decrease in the suction and discharge pressures when the nano refrigerants are used.

Figure 10: Suction pressure.

Figure 11: Discharge pressure.

Conclusion

This research work is invesitigated to compare the nano refrigerants R600a & R290/SiC and R600a & R290/Cryo SiC with respect to the conventional R600a & R290 refrigerant based on the experiments conducted in the domestic refrigerator.

The COP of the nano refrigerants R600a & R290/Sic and R600a & R290/cryo SiC had been increased when compared to the standard R600a & R290 refrigerant. The highest COP of 1.439 is obtained for R600a & R290/cryo SiC nano refrigerant.
The power consumption of the refrigerator is reduced when nano refrigerants are used and the least amount of energy consumed by the refrigerator is 0.073 W when R600a & R290/cryo SiC refrigerant is used.
The results proved that the influence of nanoparticles in the refrigeration system have shown the improvement.
It is also concluded that the use of nano refrigerants is not only efficient and eco-friendly but also cost effective, thus the experiment shows us that the nano refrigerants have a good scope in future applications.

Data Availability Statement:

The data that support the findings of this study are available from the corresponding author, Senthilkumar D], upon reasonable request.

Journal of Physics and Chemistry Research

Improvement Of Performance of Refrigeration System Using Hydrocarbon Refrigerant Mixed with Cryogenically Treated Sic Nanopowder

Abstract

Keywords

Introduction

Results and Discussion

Conclusion

References