Irreversibility Reduction in Vapour Compression Refrigeration Systems Using Al2O3 Nano Material Mixed in R718 as Secondary Fluid

Abstract

The several methods are available in the literature for improving first law efficiency in terms of coefficient of performance. The second law efficiency is helped for finding the irreversibilities the systems. The uses of nano refrigerants in the vapour compression refrigeration play a very important role for reducing irreversibility in the system and improving its thermodynamic performances. This paper describes thermal modelling of vapour compression refrigeration system using energy - exergy analysis. In this system, the utility of ecofriendly twelve refrigerants in primary circuit is highlighted and Al2O3-Water based nanofluids in secondary circuit. This model takes care the nanoparticles mixed in the fluids as input conditions in the secondary evaporator circuit as geometric characteristics of the system such as size of nanoparticles and the compressor speed to predict the secondary fluids output temperatures, the operating pressures, the compressor power consumption and the system overall energy performance. Such design analysis is conveniently useful to compare the thermal performance of different nano-particles of Al2O3 based nano-fluid as a secondary fluid in a vapour compression refrigeration system. The influence of input variables on the irreversibilities in terms of exergy destruction ratio of the system is presented. Such a model can also be used to design various components viz. evaporator, compressor, condenser and throttle valve for vapour compression refrigeration systems for any desired cooling capacity. This model takes care of use of nanofluids as a secondary fluid in vapour compression refrigeration systems and simulate the non linear equations of the system. The use of R407c as ecofriendly refrigerants is quite adequate while first law performance improvement is around 13.491% by using nano particles. The % improvement in first law efficiency is found to be 11.04% by using nano particles as compared to without nano particles. While by using R134a 12.60% improvement. Similarly It was also observed that second law performance improvement is ranging between 15% to 39.13%. The better second law efficiency is 39.13% improvement due to, by using R1234yf as compared to 16.52% improvement by using R1234ze in the primary evaporator circuit. The reduction in the irreversibility in terms of exergy destruction ratio in the system and maximum exergy destruction ratio around 25.294% was observed by using R152a and exergy destruction ratio is 22.79% by using R290 hydrocarbon and 23.403% by using R407c as ecofriendly refrigerant. The Reduction in EDR is 20.09% by using R404a, and 21.37% by using R134a. The R1234ze and R1234yf have slightly less reduction in EDR as compared by using R134a.