Thermal Stabilization as a Key to Sustainable Operation of Combustion Engines and Power Plants—Part 2: Thermal Stabilization of IES Due to Advanced Intake Air Cooling and Heat Recovery Assessed by Appropriate Criteria

The sustainable performance of combustion engines in integrated energy systems (IESs) at a safe thermal level and with high fuel effectiveness is possible if intake air is cooled and the released heat is fully utilized by a heat recovery chiller (HRCh). Herein, the temperature of return hot water, used as a coolant, at the engine inlet is not to be higher than 70 °C to ensure safe, thermally stabilized engine performance. This cannot be ensured by only an absorption lithium-bromide chiller (LBCh) as the most efficient HRCh, which has a COP of about 0.7 and provides a return hot-water temperature of about 75 °C against the required 70 °C, which reduces the engine lifetime by about 10%. To ensure the thermally stabilized performance of the engine in conventional IESs, the residual heat left from the LBCh is ejected into the atmosphere by an emergency radiator with a heat loss of about 25% as the “cost” for safe engine performance. The concept of IES thermal stabilization in terms of both aspects—intake air cooling and the full utilization of the released heat by a combined LBCh boosted by an ejector chiller (ECh), easily implemented into an existing IES—was developed. The appropriate new unified criterion indicators for estimating the rate of thermal stabilization (RS) were adopted to ensure sustainable performance and increased the lifetime of the engine by about 10%, providing an innovative heat recovery intake air cooling system and boosting the conventional IES as a prosperous trend. Thus, for the first time in the practices of IES design and operation, the aggregated effect on engine thermal stabilization, followed by maximizing its efficiency, has been gained due to intake air cooling and full utilization of the heat released as mutually affecting aspects.