*Article* **Energy Saving and Economic Evaluations of Exhaust Waste Heat Recovery Hot Water Supply System for Resort**

**Nghia-Huu Nguyen 1,†, Dong-Yeon Lee 2,†, Kunal Sandip Garud <sup>3</sup> and Moo-Yeon Lee 3,\***


**Abstract:** The objective of this study is to investigate the energy savings and economics of the hot water supply system for the luxury resort. The hot water was generated using the waste heat from the exhaust gas heat (EGH) of internal combustion engine (ICE) installed at the luxury resort. The capacity and characteristics of waste heat source, flow demand and supply system of hot water were surveyed, and data is collected from the real system. The new heat exchanger system which utilizes the EGH to produce the hot water is designed considering the dew point temperature and the back pressure of exhaust gas system. The results show that the proposed system could supply hot water at a temperature of 55 ◦C corresponding to the present resort demand of 6 m3/h using EGH of ICE at 20% load. The proposed system could achieve the saving of 400 L/day in diesel oil (DO) fuel consumption and the payback time of new system could be evaluated as 9 months. The proposed system could produce hot water of 14 m3/h at 25% of engine load and 29 m3/h at full engine load which are sufficient to satisfy the regular and maximum hot water demand of resort. The presented results show the capability of the proposed system to satisfy the current hot water demand of resort and suggest the larger potential to save energy by recovering EGH of ICE. The novelty of the present work involves detailed methodology to design heat exchangers and evaluate system economics for hot water supply system based on EGH of ICE.

**Keywords:** economic; energy saving; hot water; heat exchanger; internal combustion engine; waste heat
