*4.1. Performance Evaluation*

Table 6 presents the exhaust gas temperature and heat recovered power for various engine loads and hot water flow rate. The exhaust gas temperature and the heat recovered power are changed due to the frequent change of ICE load to satisfy the demands during the actual operation. The exhaust gas temperature and heat recovered power are increasing with increase in the hot water demand and corresponding increase in engine load. To satisfy the increasing demand of hot water, it is required to increase the hot water flow rate. This means higher exhaust heat is needed to satisfy the increasing demand therefore, the engine load has increased to produce the exhaust gas with higher temperature. The higher portion of heat could be recovered by increase in the exhaust gas temperature due to increase in the heat transfer capacity. As can be seen that when the engine is running at 25% corresponding EGH of ICE is enough to produce the hot water demand of 6 m3/h. The hot water demand changes with time at the resort which results into change in the heat recovered efficiency and the exhaust gas-out temperature. The calculated heat recovered efficiency and exhaust gas temperature corresponding to various hot water demand are shown in the Table 7. The waste recovery power and efficiency are lower at the lower hot water flow rate demand due to higher exhaust gas temperature (higher exhaust waste heat). This means larger portion of exhaust heat is wasted as the demand is not high. However, with increase in the hot water flow rate demand, the exhaust gas temperature reduces which shows significant increase in the heat recovery power and efficiency. As can be observed that the hot water demand is in range 2–6 m3/h, corresponding to the heat recovered power is lowered by 25% and the exhaust gas-out temperature is still rather high *teg* > 390 ◦C, it means that there are still large amounts of excess heat that has not been fully used in exhaust gas of ICE. If the flow rate demand of hot water increases to *Vhw* = 25 m3/h in the future, the exhaust gas-out temperature is *teg* = 140 ◦C still higher than the dew point temperature of the exhaust gas *tdp* = 130 ◦C. Therefore, the condensation cannot occur in the exhaust gas system, the safety of operation is ensuring. The higher demand of hot water could be satisfied at the higher ICE load. The hot water flow rates of 26 m3/h could be achieved at the ICE load of 80% and that could be further increased to 29 m3/h at the ICE full load. The heat recovery power and efficiency of 155 kW and 23%, respectively are achieved for the proposed system at the regular hot water flow rate demand of 6 m3/h. At the maximum hot water flow rate demand of 25 m3/h, the highest heat recovery power of 645 kW and highest heat recovery efficiency of 97% could be achieved.


**Table 6.** Temperature and heat power of exhaust gas, flow rate of produced hot water change on ICE load.


25 645 97 140

**Table 7.** The heat recovery efficiency and the exhaust gas-out temperature change on the hot water demand. **Table 7.** The heat recovery efficiency and the exhaust gas-out temperature change on the hot water demand.
