Heliyon (Aug 2022)
Energy and exergy simulation analysis and comparative study of solar ejector cooling system using TRNSYS for two climates of Iran
Abstract
This paper addresses hourly simulation of 3.5 kW Solar Ejector Cooling System (SECS) using R600a and R290 hydrocarbon refrigerants for application in two office buildings in semi-arid and hot-humid climates of Iran. During the period of the study, thermodynamics energy and exergy of the cooling systems when charged with the two refrigerants are fully assessed by simulation at the two study sites. The simulation studies of the entire cooling system indicate that the most irreversible process and hence the prime exergy destruction is related to the solar collector system followed by the ejector component in the cooling cycle. The ejector is a constant-area mixing (CAM) type which is mathematically modeled in Engineering Equation Solver (EES) software. Generator of the cooling cycle is modeled in EES using ε−NTU method and a simulation program is developed on TRNSYS-EES co-simulator for dynamic study of the cooling cycle. For comparison of efficiency of the two refrigerants, working conditions are set to be the same. The systems are equipped with auxiliary heaters to provide constant inlet temperature of 85C∘ for the generator when solar radiation is partially in phase with the building sites. The hourly and monthly simulation of both SECS in June, July, August and September 2019 demonstrate that R290 is more efficient for increasing the overall COP(=0.2844) of the system than R600a (COP=0.2797) of the building office in the semi-arid region where the generator receives most of its thermal energy from solar radiation in July 17, 2019. Although, the same refrigerant is also more efficient than R600a in the hot-humid region system in the same day, but the system compensates shortage of its necessary solar thermal energy mostly from the auxiliary heater.
