Research On The Application Of Household Air Source Heat Pump Dual-end System In Residential Buildings In Southern Shaanxi

According to the regional classification of China’s thermal zones,the southern Shaanxi region is mostly categorized as a"hot summer and cold winter"zone with no centralized heating.However,the cold and damp winters lead to low indoor temperatures,which affect normal living conditions.At the same time,with the improvement of people’s living standards,the demand for summer cooling in the region has become increasingly strong,and the need for year-round air conditioning has become an urgent issue.Therefore,this paper proposes the application of a"floor heating+fan coil"dual-end system using air source heat pumps as a heating and cooling source,utilizing floor radiant heating in winter and fan coil cooling in summer.This system can provide energy-efficient and comfortable heating in winter while avoiding the disadvantage of dew condensation caused by floor radiant cooling in the summer,and it cools down faster.To solve the indoor comfort problem in non-centralized heating areas such as rural and suburban areas in this region,clean heating and cooling can be provided through the year-round use of air source heat pumps,which can serve as a theoretical basis and reference for practical engineering design.This paper investigates the application of an air source heat pump dual-end system in a standalone villa located in the suburbs of Luonan County,Shangluo City.The building’s walls are constructed with EPS(expanded polystyrene)modules with excellent thermal insulation performance(with a heat transfer coefficient of 0.3 W/(m2·K)measured by the heat flow meter method).Through the analysis of the wall surface temperature,it is proved that EPS material has good thermal insulation performance when used for building walls.By measuring the system during a 110-day heating period and a2-day cooling period,the characteristic parameters and operating energy consumption data of the air source heat pump floor heating and fan coil cooling were obtained to understand the operating law of the air source heat pump dual-end system.The results show that during the summer,the average indoor air temperature at a set temperature of26℃meets the requirements of Grade I thermal comfort,while at a set temperature of24℃,the average indoor air temperature is 22.9℃,which is below the range required for Grade I thermal comfort(24℃to 26℃),making the room too cold.In winter,with a set indoor temperature of 20℃,the indoor temperature can remain at 16.5℃to 20℃for a long time after the unit is automatically shut off at night,meeting the indoor design temperature requirement of Grade II comfort.The control of the unit’s supply and return water temperatures is good,and COP_h can be maintained at above 2.7,indicating good overall heating performance.A simulation model was established using Airpak software for the building and the double-end heat pump system.After validation,the simulation performance of the model was found to be able to replace the actual system operation with an error of less than 3%.The simulation analysis and comparison results of the indoor temperature field,velocity field,and PMV-PPD were conducted for eight scenarios,including four floor temperature scenarios in winter and four supply air temperature scenarios in summer.The results show that as the floor temperature increases,thermal comfort gradually improves,and a floor temperature of 25℃is sufficient to achieve level I thermal comfort in the room.As the supply air temperature of the fan coil unit increases,the thermal sensation changes from cold to hot,and the highest supply air temperature that can meet level I thermal comfort is 22℃.To sum up,the air source heat pump double-terminal system can meet the requirements of class I indoor thermal comfort in southern Shaanxi with reasonable operation parameters.