| Radiant coil is a new type of energy saving heating/cooling terminal form.Its operating principle is to reduce(increase)the temperature of one or more radiation plates in the building through convective heat transfer of refrigerant(heat medium)in the coil.Radiant plates mainly meet the needs of indoor thermal environment in the form of radiation heat transfer.Because of its high thermal comfort,good energy saving effect,occupying less floor area and other advantages,the system has attracted the attention of the industry.Especially in the aspects of heating in winter,has been popularized in northern areas in China is a vast,but the cooling in the summer,because the system have a need to control radiation harden dew,water temperature too low,may arise as a result,the system cooling ability insufficient,this contradiction makes radiant coil are idle most of the time in the summer,causing a certain amount of waste of resources.To solve the problem of radiation cooling system in summer in north China idle resources waste problem,This paper is based on meteorological parameters in Beijing area,design a kind of radiant cooling system based on EAHE(Earth to Air Heat Exchanger)and building indoor test bench,EAHE system as a kind of fresh air cooling dehumidification equipment coupled with radiation cooling system is used,EAHE system and radiant cooling system Shared indoor cooling load,EAHE system bears all the indoor wet load.A total of 21 test conditions were designed by the control variable method.The characteristics of the system were studied from four aspects:fresh air volume(10～50 m~3/h),soil temperature(11～19℃),water supply flow(100～500 kg/h)and water supply temperature(10～18℃).The main research results are as following:(1)The temperature difference between supply and return water to the radiant cooling system increases with the decrease of water supply temperature and water supply flow respectively.The cooling capacity of the system and the cooling capacity of the radiation plate increase with the decrease of the water supply temperature and the increase of the water supply flow,respectively.The cooling capacity of the radiation plate is low when the radiation cooling system is running,the maximum cooling capacity of the radiation plate is only 196.8 W,the cooling capacity of the radiation plate per unit area is 24.6W/m~2,and the minimum cooling capacity of the radiation plate is only 129.7 W.The cooling capacity per unit area of the radiation plate is 16.2W/m~2.With the operation of the radiant cooling system,the temperature of the radiant plate continues to decrease.When the surface temperature of the radiant plate is lower than the indoor air dew point temperature,the condensation phenomenon between the radiant plate and the air at the bottom of the room will occur,and there is a risk of corrosion of the floor surface structure.(2)The cooling capacity of EAHE system increases with the decrease of soil temperature and the increase of fresh air volume,respectively,but the temperature decline rate gradually decreases with the increase of buried pipe length.Dehumidification capacity of EAHE system increases with the decrease of soil temperature and fresh air volume respectively.When the soil temperature is between11℃and 19℃,the cooling capacity ranges from 239.5 to 386.9 W,and the enthalpy humidity ratio ranges from 4190 to 4580.When the soil temperature is 15℃and the fresh air volume is 10～50 m~3/h,the cooling capacity of the system ranges from 109.7to 466.5 W and the enthalpy humidity ratio ranges from 4190 to 4520.With the operation of the system,the longitudinal air temperature difference and humidity difference of the room first increase and then decrease,and finally tend to be uniform.(3)The radiant cooling system based on the EAHE system uses the radiant cooling system and EAHE system in coupling.Through experiment calculation,the cooling capacity and enthalpy humidity ratio range provided by the system are obtained under the soil temperature range of 11～19℃,fresh air volume range of 10～50 m~3/h,water supply temperature range of 10～18℃,water supply flow range of 100～500 kg/h.The maximum cooling capacity of the system is 663 W,and the minimum is 293 W.The maximum enthalpy humidity ratio of the system is 10699,and the minimum enthalpy humidity ratio of the system is 5160.The system has a good cooling and dehumidification effect.As a fresh air cooling and dehumidification system,EAHE system will be opened after 15 minutes of operation of the radiation cooling system and run with the radiation cooling and air conditioning single system.The air temperature within 0.1 m of the room height will drop by 0.5℃within 2 minutes.When the room height is 0.2 m,the moisture content of the air decreases by 1.08 g/kg within two minutes,which effectively solves the contradiction of insufficient cooling capacity caused by the anti-condensation demand of the radiation cooling system.To sum up,This paper is based on meteorological parameters in Beijing area,EAHE system as the radiant cooling system of air cooling dehumidification equipment,effectively resolve the radiant cooling system due to prevent dewing needs enough cooling this contradiction,the research results expand the applicable conditions of radiation coils and provide a feasible path for heating/cooling requirements in high temperature and humidity areas in summer. |
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