https://orcid.org/0000-0002-9347-7267
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ABSTRACT
The most common refrigeration system is the vapor compression refrigeration (VCR) system for a household refrigerator. The challenges for researchers are to minimize the power consumption of the compressor to improve the performance of the refrigeration system. This study aimed to assess and compare the energy and exergy analysis of VCR systems using multi-walled carbon nanotubes (MWCNT) and graphene nanosheets (GN) based hybrid nano-lubricants. The mass concentrations of each nanoparticle 0.3 g/L, 0.5 g/L, 0.7 g/L, and 0.9 g/L are mixed with 250 ml of polyolester oil (POE) separately and charged with 200 g of R134a refrigerant. Furthermore, the MWCNT and GN nanoparticles are mixed in a 50:50 proportion to prepare the same concentration of hybrid nanoparticles. The properties of refrigerants are obtained with the help of REFPROP 9.1 software. The pull-down time, compressor power, pressure ratio, exergy loss, relative irreversibility (RI), and second law efficiency (SLE) are variables that have been examined. The mass concentration of 0.7 g/L of hybrid nano-lubricants (GN-MWCNT/POE) is found to be optimal. It is noted that the pull-down time, power consumption, and pressure ratio of the refrigerator are lowered by 9.01%, 16.09%, and 5.68% respectively when compared to the pure refrigerant, whereas the actual COP and SLE improved by 11.29% and 8.22% at 0.7 g/L hybrid nano-lubricants. In addition, exergy loss and relative irreversibility are decreased for hybrid nano-lubricants.
Nomenclatures
| RI | = | relative irreversibility |
| nm | = | nanometer |
| MWCNT | = | multi-walled carbon nanotubes |
| q | = | refrigeration effect (kJ kg−1) |
| h | = | specific enthalpy (kJ kg−1) |
| v | = | specific volume (m3 kg−1) |
| Cp | = | specific heat (kJ kg−1 K−1) |
| k | = | Thermal Conductivity (W m−1 K−1) |
| VCR | = | vapor compression refrigeration |
| m | = | mass (kg) |
| p | = | pressure (bar) |
| T | = | temperature (°C) |
| SLE | = | second law efficiency |
| COP | = | coefficient of performance |
| Win | = | compressor power (kW) |
| conc. | = | concentration |
| HTC | = | heat transfer coefficient |
| HP | = | high-pressure |
| ID | = | inner diameter |
| LP | = | low pressure |
| OD | = | outer diameter |
| kW-h | = | kilowatt hour |
| POE | = | polyolester |
| MO | = | mineral oil |
| LPG | = | liquefied petroleum gas |
| TR | = | tons of refrigeration |
| Greek symbols | = | |
| ղII | = | second law efficiency |
| φ | = | GN/MWCNT mass concentration, (g/L) |
| Subscript | = | |
| 1 | = | compressor entry |
| 3 | = | condenser exit |
| suc | = | Suction side |
| cond | = | condenser |
| in | = | inlet |
| Evap | = | evaporator |
| comp | = | compressor |
| avg | = | average |
| 2 | = | compressor exit |
| 4 | = | evaporator exit |
| dis | = | discharge side |
| cap | = | capillary tube |
| ext | = | exit |
| l | = | lubricant |
| r | = | refrigerant |
| agg | = | aggregate |
Acknowledgements
The author appreciates the support given by Maulana Azad National Institute of Technology, Bhopal, Madhya Pradesh (M.P.)
Disclosure statement
The authors affirm that they do not possess any financial conflicts of interest that could be perceived as having influenced the research findings and outcomes presented in this manuscript.
Additional information
Notes on contributors
Md Jamil Akhtar
Md Jamil Akhtar is a Ph.D scholar in mechanical engineering department at MANIT, Bhopal (INDIA). He works in the area of thermal engineering and refrigeration and air-conditioning.
S.P.S. Rajput
S.P.S. Rajput is a professor in mechanical engineering department at MANIT, Bhopal (INDIA). He works in the area of thermal engineering, refrigeration and air-conditioning, energy conversion cycles and human thermal comfort.