Optimization Of Collector Structure And Cogeneration Of Heat And Power For Direct Expansion Solar Heat Pump System

China is facing serious energy and environmental problems.Our electricity supply,domestic hot water,and winter heating in northern regions were all major contributors to energy consumption and carbon emissions.In the face of the "dual carbon goal" test,the efficient,indepth and comprehensive development and utilization of my country’s abundant solar energy resources had important practical significance for the sustainable development of energy.From the perspective of improving the comprehensive utilization rate of solar energy,this paper focused on the research in the direct expansion solar auxiliary heating system,and combined the finite element method and the response surface optimization method to optimize the structure of the flow channel of roll-bond collector.The simulation model of cogeneration of direct expansion solar auxiliary heating system was constructed using the modeling technology.The specific work content were as follows:(1)Aiming at the problem of unreasonable distribution of runners of roll-bond collectors in the direct expansion solar auxiliary heating system,a "Y"-shaped runner structure was proposed.Based on the heat transfer model of the collector,a conjugate heat transfer finite element simulation analysis was carried out on the flow channel element in ANSYS software,and the flow and heat transfer characteristics inside the "Y"-shaped flow channel element were studied.(2)The four factors of subunit width,subunit length,runner parting angle and runner width of the "Y"-shaped runner unit were selected as control variables,with thermal efficiency and pressure drop coefficient as the response levels,based on Box-Behnken Based on the principle,a four-factor,two-level response surface test was designed to determine the primary and secondary relationship of each factor’s impact on the response.Using Design Expert software,the model was optimized with two objectives,and the optimal structure control scheme of "Y"shaped flow channel unit was obtained,and the optimal scheme was verified by experiments.(3)Based on the optimization of the flow channel structure of the collector,combined with Photovoltaic/Thermal(PV/T),the cogeneration of the direct expansion solar auxiliary heating system was studied,and the system was established by TRNSYS software.The instantaneous simulation model of cogeneration,and the simulation results of the system in typical weather days were obtained.(4)An experimental platform for cogeneration of direct expansion solar auxiliary heating system was built,and a one-week experimental test was carried out in the heating season in severe cold areas,which verified the accuracy of the TRNSYS instantaneous simulation model.And the performance of the actual operation of the system was analyzed with the electrical efficiency,thermal efficiency,comprehensive efficiency and system comprehensive COP(energy efficiency ratio)as evaluation indicators.This study provided a reference for improving the performance of the direct expansion solar auxiliary heating system and the application of photovoltaic photothermal integration,which had certain practical significance.