In the present study, a new technique of utilizing nanofluid as a secondary fluid in a secondary loop of refrigeration system is examined. This secondary loop serves for providing cooling in specific applications such as walk-in coolers and freezers. The secondary loop is obtained across the evaporator section wherein the refrigerant R134a extracted heat from the nanofluid. The evaporator here is classified as shell and coil heat exchanger where nanofluid flowed in the shell side and refrigerant flowed in the coil. A compressor, expansion valve and water cooled condenser are the major integral parts of the system. Experiments were conducted for various volume concentrations of Al₂O₃ nanofluid (0-15%), mass flow rates (40-80 g/s) and nanofluid inlet temperatures (30-40 ˚C). The modified system exhibited superior performance when Al₂O₃ nanofluid was employed in the secondary loop as compared to base fluid (distilled water) while operating at the same mass flow rate and inlet temperature. A maximum COP of 6.5 was achieved for nanofluid inlet temperature 40 C at mass flow rate 80 g/s and volume concentration 15%. The enhancement in refrigeration effect and coefficient of performance is attributed to micro conduction effect due to the rise in thermal conductivity of nanofluid as compared to distilled water.

在本研究中，研究了一种在制冷系统的次级回路中利用纳米流体作为次级流体的新技术。该辅助回路用于在特定应用中提供冷却，例如步入式冷却器和冰柜。跨蒸发器部分获得次级回路，其中制冷剂R134a从纳米流体中吸收热量。此处的蒸发器归类为壳管式热交换器，其中纳米流体在壳侧流动，制冷剂在盘管中流动。压缩机，膨胀阀和水冷冷凝器是系统的主要组成部分。针对各种体积浓度的Al ₂ O ₃进行了实验纳流体（0-15％），质量流量（40-80 g / s）和纳流体入口温度（30-40˚C）。当在相同的质量流量和入口温度下运行时，与基础流体（蒸馏水）相比，在次级回路中使用Al ₂ O ₃纳米流体时，改进的系统表现出卓越的性能。在质量流量为80 g / s，体积浓度为15％的情况下，纳米流体入口温度为40 C时，最大COP为6.5。与蒸馏水相比，由于纳米流体的热导率增加，致冷效果和性能系数的提高归因于微导作用。