Energy-saving operation strategy of air conditioning system in tea brick fermentation room under different outdoor meteorological parameters

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In the process of tea brick production, the major energy consumption lies in the air-conditioning system of the tea fermentation chamber. Under the condition of satisfying the fermentation process, the energy-saving operation of the air-conditioning system is an effective method to reduce the energy consumption and to improve the economic benefit of the tea brick. However, due to lack of quantitative calculation of the indoor heat and moisture load during the fermentation process, the air conditioning system of the tea brick fermentation chamber is mainly based on the CAS (circulating air system) or the ORCS (One return air conditioning system). Consequently, in this study, the heat and moisture transfer model of the tea brick was built based on the heat and moisture coupling transfer theory for porous media. The COMSOL Multiphysics was implemented to solve the heat and moisture exchange rate between tea bricks and the fermentation environment. Based on the rate and the heat transfer of the envelope structure, the heat and moisture load of the fermentation chamber was calculated under different meteorological parameters. According to the indoor heat and moisture load and outdoor weather parameters, the energy consumption and exergy loss of the two air conditioning systems were analyzed during the fermentation cycle. The results show that the ORCS energy efficiency is 30.8%–55.8% greater than that of the CAS, and the irreversible exergy loss is also reduced by 19.6%–57.0% when the residual heat Q inside the fermentation chamber is less than zero. On the other hand, when the residual heat Q is greater than zero, the CAS energy efficiency is 16.1%–22.3% greater than that of the ORCS, and the exergy loss is reduced by 37.8%–43.3%. According to the energy and exergy analyses of the two air-conditioning systems, an energy-saving operation strategies of air conditioning system for brick fermentation were determined in different tea brick production areas.