Modern engines in general waste plenty of heat to the exhaust gas and coolant. Considering that daily driving consists of frequent cold start, idling, and part load driving within short driving distances, the potentials to recover heat from high enthalpy exhaust gas are limited. In recovering heat from low enthalpy exhaust gas, a low thermal inertia exhaust heat recovery unit (EHRU) with no heat transfer fins is proposed to be integrated to the simplified split cooling circuit used in the earlier studies. This lightweight, compact and simple EHRU concept made of machined steel plate is targeted for naturally aspirated engines that are still being widely used worldwide. Cooler coolant feed from the bottom of the cylinder block’s water jacket rear end provided large temperature difference between the coolant and exhaust gas. In evaluating its effectiveness in speeding up the recovered heat availability for reuse, a 1.3 l passenger car equipped with strategically placed multiple thermocouples and flow meters was tested using NEDC test. From the experiments and classical analysis, the recovered thermal energy was available in just 25 s after cold start. The study also provided a new direction on the design of EHRU and its integration into an engine.

现代发动机通常会将大量热量浪费在废气和冷却液中。考虑到日常驾驶包括频繁的冷启动、怠速和短距离内的部分负载驾驶，从高焓废气中回收热量的潜力是有限的。在从低焓废气中回收热量时，建议将没有传热翅片的低热惯性废气热回收单元 (EHRU) 集成到早期研究中使用的简化分体式冷却回路中。这种由机加工钢板制成的轻巧、紧凑和简单的 EHRU 概念适用于仍在世界范围内广泛使用的自然吸气发动机。冷却器冷却液从气缸体水套后端的底部进料，使冷却液和废气之间存在较大的温差。在评估其在加快回收热量以供再利用方面的有效性时，使用 NEDC 测试测试了一辆 1.3 升的客车，该客车配备了战略性放置的多个热电偶和流量计。从实验和经典分析来看，在冷启动后仅 25 秒内即可获得回收的热能。该研究还为 EHRU 的设计及其与发动机的集成提供了新的方向。