Performance Analysis of Custom-Designed Heat Exchanger and Latent Heat Thermal Energy Storage System for Diesel Engine Exhaust Waste Recovery System

Abstract

The current study presents an experimental analysis of a custom-designed heat exchanger (CDHX), for recovering the waste heat energy of the exhaust gas from a stationary diesel engine. It has triangular external finned tubular construction with its shell flue side fitted with segmental baffles sloped at 20°, to effectively extract heat to raise the tube side circulating thermal oil temperature for sensible heat rise. This, in closed loop, transfers the heat to non-moving, sealed and filled thermal storage system with phase change material (PCM) as the latent heat energy. From the third closed loop circulating water from the thermal storage, it indirectly supplies the heat for steady and peak state process consumptions. Balmerol prototherm medium heat transfer oil and water circulations are used as the respective heat extraction liquid media during the charging and discharging process, with PCM at varied levels of molten conditions. The temperature rise behavior of the heat transfer fluid in the CDHX under different load conditions of the engine is studied. The thermal performance analysis of the CDHX has been evaluated using effectiveness and heat extraction rates. The behavior of PCM temperature in the latent heat thermal energy storage (LHTES) tank during charging and discharging process is studied. The evaluation of the performance of the LHTES system has been analyzed by estimating the charging rate with increased melted liquid and latent heat energy stored during the charging process and discharging rate of PCM during solidification process. It is found that nearly 53–60% of stored material latent heat energy is recovered from the PCM in the LHTES tank. It is used by closed loop hot water circulation during discharging process for steady-state drying of food products to reduce the gap between demand and supply of energy. The maximum heat extraction rate of the CDHX integrated with LHTES tank is 3.9 kW, and the charging rate in the LHTES tank is 1.550 kW at full-load condition of the engine. At the flow rate of water of 6 lpm, the maximum heat discharge rate of PCM in the LHTES tank is 0.710 kW and it decreases to 0.58 and 0.47 kW for reduced 4 and 2 lpm flows, respectively. The water temperature that rises nearly 72 °C during discharging process of LHTES tank for 70-min duration achieved at the flow rate of 6 lpm.