Performance investigation of diesel generator set based waste heat harnessing system for space heating application

Abstract

Abstract Diesel generator (DG) sets employed in decentralized power generation systems generally exhibit an electrical efficiency in the range of 30%–38%, while a considerable portion of input energy is lost as waste heat through exhaust gases and engine cooling circuits. Recovery of this thermal energy can support applications such as space heating and domestic hot water production, particularly in isolated or remote regions. The present investigation focuses on the recovery of exhaust heat from a 62.5 kVA diesel generator and its integration into a micro combined heat and power (MCHP) configuration. In addition, the practical feasibility of implementing such a small‐scale CHP system under real operating conditions was examined. A low‐fin 1–2 shell‐and‐tube heat exchanger was adopted as the waste heat recovery device because of its mechanical durability and established industrial applicability. The thermal design and performance of the heat exchanger were validated using Aspentech simulation software, and a peak effectiveness of 0.69 was achieved. To evaluate the influence of working fluid properties on heat recovery performance, three heat transfer fluids (HTFs) were considered: pure water, water–propylene glycol 40% (vol.), and water–propylene glycol 50% (vol.). Experimental observations revealed that effective electrical efficiency, thermal recovery efficiency, CHP efficiency, and heat exchanger effectiveness improved with increasing generator load, whereas the heat‐to‐power ratio (HPR) showed a declining trend. The highest heat exchanger effectiveness was recorded within the 75%–90% loading range of the DG set. Among the tested HTFs, pure water demonstrated superior thermal performance, producing a maximum CHP efficiency of 46% with an electrical efficiency of 31% at rated operating conditions. Additionally, the quantity of heat recovered per unit power output was greatest when water was used as the working fluid.