Abstract
In the present paper, the numerical analyses of the heat charge and discharge processes of the latent heat energy storage (LHTES) system designed for the recovery of the exhaust waste heat energy of the SI engine presented. In the LHTES system as phase change material (PCM), the charge and discharge ability of paraffin wax commercially identified with code RT27 were analyzed depending on time. Two closed-loop fluid circulation system consisting of two heat exchangers (HESs) was designed, someone connected to the exhaust path of SI engine for waste heat recovery, and the other used for the charging and discharging of waste heat energy in the PCM. To transfer the waste heat from the hot exhaust gases to the PC, cold water was used as the heat carrier fluid. In the numerical analysis, the exhaust gas temperature and flow rate values of a single-cylinder, air-cooled having a stroke volume of 476.5 cm3 SI engine operated with gasoline 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 paraffin wax under boundary conditions, the process of heat charge (melting) completed at 8000.sec with 93% liquid-fraction, while the process of heat discharge (solidification) completed at 55000.sec with 15% liquid-fraction.
Highlights
Even in today's engine technologies, approximately 3040% of the fuel energy in vehicles with internal combustion engines (ICEs) is thrown into the atmosphere as waste heat energy [1,2,3]
Unburned hydrocarbons (UHC), carbon monoxide (CO), nitrogen oxides (NOx) and particulate matter (PM) emissions emitted into the atmosphere from internal combustion engines pose health exposures [4,5,6]
The latent heat thermal energy storage (LHTES) systems using phase change material (PCM) as storage media for exhaust waste heat recovery are widely used by many researchers [9,10] due to its large energy storage capacity [11] and almost constant operating temperature [12] in a narrow temperature interval [13]
Summary
Even in today's engine technologies, approximately 3040% of the fuel energy in vehicles with internal combustion engines (ICEs) is thrown into the atmosphere as waste heat energy [1,2,3]. The low thermal conductivity of most PCMs limits the performance of LHTES systems, leading to a much longer charging or Gurbuz and Ates / International Journal of Automotive Science and Technology 4 (4): 314-327, 2020 discharging process [18] Another disadvantage of the solid-liquid phase change process is the mechanical stability of the PCM and the volume change that occurs during the melting process [19]. Additional experimentally and computationally studies are required on the appropriate PCM selection, HEX design, operating conditions and general structure of the LHTES system in terms of optimization of parameters such as charge/discharge time, phase change capability and thermal conductivity. Timedependent data and contour images of heat flux, mean temperature, liquid-fraction were obtained and interpreted
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