ENERGY AND EXERGY ANALYSIS OF DOUBLE PIPE MINI-TUBE HEAT EXCHANGER

Global population growth and the resulting rapid depletion of energy resources make attaining sustainability of energy resources difficult. By reducing size, weight, and costs, more effective and sustainable systems can be developed, and resource consumption reduced. Mini-channel heat exchangers ensure higher heat transfer than macrochannel heat exchangers because of the volume and surface effect factor. Furthermore, the performance of heat exchangers can be increased by suspending nanosized particles in the base heat transfer fluids. In this study, a concentric mini-tube heat exchanger was designed and manufactured, and energy-exergy analyses were made. Multi-walled carbon nanotube (MWCNT)-water nanofluid prepared at various volume concentrations (0.1%, 0.2%, 0.3%) and used as a working fluid. The heat transfer performance of the concentric mini-tube heat exchanger was evaluated using the effectiveness coefficient-number of transition units (epsilon-NTU) method. The relationship between epsilon, NTU, Reynolds number, and dimensionless exergy is investigated. Effectiveness (epsilon), NTU, and dimensionless exergy (e) values were calculated in the range of five different Reynolds values (5000-25,000) for water and nanofluids prepared at three different volumetric concentrations. The use of nanofluids as a working fluid was found to increase the epsilon and NTU values while decreasing the dimensionless exergy value.