Analytical investigation of energy performance in secondary loops of refrigeration systems using different nanomaterial additives

The energy performance in a secondary loop of refrigerating systems using nanomaterials additives was investigated analytically. In order to predict the performance of these systems, an analytical model was developed. A combination of the Effectiveness Number of Transfer Units method and traditional heat transfer and fluid dynamics correlations was used to develop this model. The Performance Evaluation Criterion (PEC: the ratio between the heat transfer rate and the pumping power required) was used to evaluate the benefit of using nanofluids instead of pure fluids. The model was validated using the data found in the literature. The model was developed for a tubular heat exchanger with different Reynolds numbers (laminar and turbulent regimes) and for different types of nanoparticles (Al2O3, Ag, Au, TiO, TiO2, Fe, Co, Cu, CuO, diamond and graphite) with different volume fractions. The results showed that the heat transfer rate significantly increased with the increase of nanoparticle concentration. But the pumping power also increased with the increase of nanoparticle concentration for laminar and turbulent flow regimes. PEC value results have shown that the energy performance was dependent on the type of nanoparticles: some of them (Al2O3, TiO, TiO2, diamond and graphite) were less efficient than the pure fluid while the others (Ag, Cu, Au, Co, CuO, and Fe) were more efficient.