Application Research Of Floor Radiant Composite Air Conditioning System In Hot Summer And Cold Winter Regions

Radiant floor air conditioning systems are known for their energy efficiency and comfort.However,when a conventional intermittently operating radiant floor air conditioning system is subjected to sudden increases in heat and moisture loads,condensation,thermal comfort degradation,slow thermal response,inadequate cooling capacity with difficulties multi-zone temperature control may occur.A floor radiant composite air conditioning system was established with an air source heat pump,floor coils of high thermal mass,fan coils,and an outdoor air dehumidifier.According to the specific thermal zone,the thermal comfort,air quality,cooling or heating capacity and energy consumption of the composite system were tested and analyzed under different operation modes in summer,winter and transition season.The annual operating characteristics were analyzed by using OpenStudio software,and the main conclusions were as follows.(1)Flexible matching between different ends of the composite system can meet the indoor thermal comfort requirements in different seasons all year round.In summer,floor cooling,fan coil and outdoor air dehumidifier were operated jointly.Indoor air temperature and relative humidity were maintained at 25.6℃ and 56.6%respectively.The vertical temperature difference was 0.75℃.PMV and PPD were-0.26 and 6.98%.In winter,floor heating and outdoor air were combined to operate,and indoor air temperature and relative humidity were maintained at 23.3℃ and 26.3%.The vertical temperature difference was only 0.17℃.PMV and PPD were 0.13 and 7.15%.In the transition season,the outdoor air dehumidifier was used for dehumidification,and the floor coil was used for auxiliary cooling or heating.The average temperature and relative humidity of indoor air can be maintained at 26.7℃ and 54.5%.(2)The precooling direct-expansion outdoor air dehumidifier combined with the fan coils was superior to conventional dedicated outdoor air system(DOAS),which can improve the response of floor radiation system and solve the problem of slow response of floor radiation system while realizing household control.In summer,the indoor temperature and humidity can meet the requirements after the floor radiation system started operating for 30 minutes.In winter,after one hour,the system was started,the indoor air temperature and humidity reach the set value.(3)The mixing valve based on PID control can control the floor surface temperature according to the air dew point temperature of the near floor surface,thus it prevents condensation and improves the cooling capacity of the floor.In summer,floor cooling,fan coil and outdoor air dehumidifier were operated jointly.The mixing water temperature was kept at 20.3℃,the average floor surface temperature was 23.56℃,and the average floor surface heat flux was 31.30 W/m~2.The composite system is suitable for residential or office with non-centralized air conditioning systems to handle transient heat and moisture load variations,and to meet the requirements of intermittent use.