Application Of Desiccant Cooling System With Heat Pipe In Nearly Zero Energy Buildings

Nearly zero energy buildings have been identified as the main strategy to solve the problem of excessive building energy consumption,as the redevelopment of energy-saving buildings,,which can assist the realization of the goal of "double carbon".Nearly zero energy buildings can significantly reduce the sensible heat load of buildings by using passive technology.But only relying on passive technology cannot adjust the latent heat load of buildings.Active dedicated outdoor air system is also needed to adjust the latent heat load of buildings.Desiccant cooling system can significantly reduce the latent heat load of buildings by using solar energy.Therefore,a desiccant cooling system with heat pipe is proposed,which combines the desiccant wheel,heat pipe and wet membrane humidifier to meet the thermal comfort requirements of nearly zero energy buildings in high humidity areas.Three modes of desiccant cooling system with heat pipe are proposed.The thermodynamic analysis under three modes which are thermodynamic process and exergy analysis,in order to obtain the desiccant cooling system with heat pipe mode which is most suitable for nearly zero energy buildings in hot summer and warm winter areas.The results show that under the condition of meeting the temperature and humidity requirements of nearly zero energy buildings,the exergy efficiency of mode I is up to 43.3%,which is the most suitable for nearly zero energy buildings.The experimental platform of desiccant cooling system with heat pipe is established.The main working parameters affecting the performance are studied through experiments.The experimental results show that when the process temperature increases,the efficiency decreases and the coefficient of thermal performance(TCOP)increases;when the moisture increases,the efficiency decreases and TCOP increases;when the process air volume increases,the efficiency and TCOP increase;when the regeneration temperature increases,the efficiency and TCOP decrease.The regeneration temperature has the most significant impact on the system performance.When the regeneration temperature increases from 60℃ to 110℃,the TCOP decreased from 1.30 to 0.52,η decreased from 0.76 to 0.18.The temperature,humidity and load changes of nearly zero energy buildings in hot summer and warm winter areas are simulated and studied by TRNbuild.The simulation results show that the nearly zero energy buildings relying on passive measures have significantly thermal insulation in hot summer and warm winter areas,but 33%and 24%of the nearly zero energy buildings are still overheated in summer and supercooled in winter respectively.In addition,the relative humidity in nearly zero energy buildings in hot summer and warm winter areas is high,and the annual relative humidity dissatisfaction rate is more than 60%.The performance of solar driven desiccant cooling system with heat pipe is studied through TRNSYS,and the feasibility of applying it to nearly zero energy buildings in hot summer and warm winter areas is analyzed.The simulation results show that the solar driven desiccant cooling system with heat pipe has significantly operation performance all year round,and the indoor temperature and humidity are maintained within the thermal comfort range of human for more than 90%of the year,which has a great indoor thermal comfort environment.In hot summer and warm winter areas,the use of solar thermal system,photovoltaic system and photovoltaic/thermal system can reduce the energy consumption of desiccant cooling system with heat pipe,but the performance of desiccant cooling system with heat pipe driven by photovoltaic/thermal system is the best.The highest TCOP of the desiccant cooling system with heat pipe driven by the photovoltaic/thermal system is 2.3,which is 2.29 times higher than the traditional desiccant cooling system,and the lowest annual average energy consumption is 54.98 kWh/m2,which is 35.32%lower than the traditional desiccant cooling system.