Experimental Performance Evaluation of a Vapor Compression Refrigeration System Using CuO–SiO?–MnO? Nanoparticle-Enhanced R134a Refrigerant with Different Capillary Tube Diameters

Improving the energy efficiency of vapor compression refrigeration systems (VCRS) is essential due to rising energy demand and environmental concerns associated with conventional refrigerants. This experimental study investigates the performance enhancement of a VCRS using nanoparticle-enhanced R134a refrigerant and different capillary tube diameters. Copper oxide (CuO), silicon dioxide (SiO₂), and manganese dioxide (MnO₂) nanoparticles were dispersed individually and in hybrid combinations within 100 g of R134a to form nano-refrigerants. Experiments were conducted using two capillary tube diameters, 0.81 mm and 1.14 mm, under controlled ambient conditions ranging from 30°C to 31.6°C. Key performance parameters such as refrigerant temperatures at various system locations, suction and discharge pressures, compressor and evaporator power consumption, and coefficient of performance (COP) were evaluated at regular time intervals. The results indicate a noticeable improvement in thermal performance with the addition of nanoparticles. For the 0.81 mm capillary tube, the COP increased from 1.50 for pure R134a to 1.80 with CuO–SiO₂ nano-refrigerant. In the case of the 1.14 mm capillary tube, the hybrid CuO–SiO₂–MnO₂ nano-refrigerant achieved the highest COP of 2.04–2.21, representing a significant enhancement compared to the base refrigerant. The study demonstrates that the combined effect of optimized capillary tube diameter and hybrid nanoparticles improves heat transfer characteristics, reduces compressor power consumption, and enhances overall system efficiency. These findings highlight the potential of nanoparticle-based refrigerants as an effective approach for improving the performance of small-scale refrigeration applications.