<p>In the present paper, the numerical analyses of the heat charge and dischargeprocesses of the latent heat energy storage (LHTES) system designed for therecovery of the exhaust waste heat energy of the SI engine presented. In theLHTES system as phase change material (PCM), the charge and discharge abilityof paraffin wax commercially identified with code RT27 were analyzeddepending on time. Two closed-loop fluid circulation system consisting of twoheat exchangers (HESs) was designed, someone connected to the exhaust path ofSI engine for waste heat recovery, and the other used for the charging anddischarging of waste heat energy in the PCM. To transfer the waste heat from thehot exhaust gases to the PC, cold water was used as the heat carrier fluid. In thenumerical analysis, the exhaust gas temperature and flow rate values of a singlecylinder, air-cooled having a stroke volume of 476.5 cm3 SI engine operated withgasoline at 1600 rpm engine speed and 1/2 throttle position were used. As a result,at designed LHTES system and numerical analysis performed for RT27 paraffinwax under boundary conditions, the process of heat charge (melting) completedat 8000.sec with 93% liquid-fraction, while the process of heat discharge(solidification) completed at 55000.sec with 15% liquid-fraction.<br></p>