Study On Heat Transfer Characteristics Of Radiant Heating And Cooling And The Application In Tall Space Air Conditioning

Radiant air conditioning system,featured as energy saving,environmental protecting,healthy and comfortable air conditioning system,has become an active and flouring research topic.Compared with traditional air conditioning system,the radiant air conditioning system possesses unique superiority in high comfort performance,energy conservation,high energy efficiency,low cost of initial installation,et al.The heat transfer characteristics of the radiant panel were studied by numerical simulation and experiment,where the experimental results are in good agreement with the simulation results.The numerical results have a good agreement with the experimental data.The results show that supply water temperature,water supply flow velocity and surface emissivity have a great influence on the heat transfer performance of the radiant plane.Water supply flow velocity and surface emissivity could boost the heat transfer within certain range.Experimental results indicate that cooling capacity of the radiant plane increased by 22 W/m~2when cool supply water temperature is decreased from 24°C to 15°C in summer cooling conditions,while heating capacity of the radiant plane increased by 83 W/m~2 when heat supply water temperature is increased from 28°C to 42°C under winter heating conditions.Numerical simulation results illustrate that cooling capacity of the radiant plane increased by35 W/m~2 when cool supply water temperature is decreased from 25°C to 16°C under summer cooling conditions,while heating capacity of the radiant plane increased by 48 W/m~2when heat supply water temperature is increased from 32°C to 40°C under winter heating conditions.Experimental results indicate that cooling capacity of the radiant plane increased by 66 W/m~2 when cool supply water flow velocity is increased from 0.1 m/s to 1.0 m/s in summer cooling conditions,while heating capacity of the radiant plane increased by 65 W/m~2when heat supply water flow velocity is increased from 0.1 m/s to 1.0 m/s under winter heating conditions.Numerical simulation results illustrate that cooling capacity of the radiant plane increased by 56 W/m~2 when cool supply water flow velocity is increased from 0.1 m/s to 0.9 m/s in summer cooling conditions,while heating capacity of the radiant plane increases by 70 W/m~2 when heat supply water flow velocity is increased from 0.1 m/s to 0.9 m/s under winter heating conditions.Numerical simulation results show that matte copper radiant plane unit area cooling capacity of 57 W/m~2,the rough processing of a small alumina plane radiant panel unit area cooling capacity of 66 W/m~2,the rolling steel radiant plane unit area cooling capacity of 77 W/m~2,the white spray paint surface radiant plane unit area cooling capacity of83 W/m~2,and the bright black spray paint surface radiant plane unit area cooling capacity of85 W/m~2 in summer cooling conditions,while the matt copper radiant plane unit area heating capacity of 102 W/m~2,the rough processing of a small alumina plane radiant panel unit area heating capacity of 115 w/m~2,the rolling steel radiant plane unit area heating capacity of 133W/m~2,the white spray paint surface radiant plane unit area heating capacity of 143 W/m~2,and the bright black spray paint surface radiant plane unit area heating capacity of 144 W/m~2under winter heating conditions.The numerical results of the surface temperature distribution on the radiant plane indicates that the surface emissivity,water supply flow velocity and water supply temperature of the radiant plane have a significant effect on the uniformity of the surface temperature distribution.The uniformity of the surface temperature distribution is easily affected by water supply temperature,while less influenced by water supply flow velocity and surface emissivity.The heat transfer coefficient of the radiant plane is obtained by fitting the experimental data of heat transfer amount of the radiant plane and the characteristic temperature difference.When using the radiant air conditioning system in summer,the total heat transfer coefficient of the radiant panel is 6.77 W/(m~2·K),the radiant heat transfer coefficient is 5.41 W/(m~2·K),and the convective heat transfer coefficient is 4.17 W/(m~2·K),respectively.When using the radiant air conditioning system in winter,the total heat transfer coefficient of the radiant plane is 8.94 W/(m~2·K),the radiant heat transfer coefficient is 6.13 W/(m~2·K),and the convective heat transfer coefficient is 3.79 W/(m~2·K).Finally,numerical simulation was conducted to study the indoor temperature distribution of the high space when the radiant plane which is located on the roof,floor and wall,respectively.Numerical results illustrate that uniform distributed of the indoor temperature when the radiant plane is placed on the wall.