Study On The Influence Of Window-Wall Ratio On Energy Consumption And Thermal Comfort Of A Convection-Radiation Combined Cooling And Heating System In Hot-Summer And Cold-Winter Area

Glass curtain walls and large window-wall ratio are becoming more and more popular among architectural designers and users because they allow more natural lighting and have great architectural appearance characteristics.However,the glass curtain wall or large window-wall ratio directly affects the interior thermal environment,energy consumption of the air conditioning system,and indoor thermal comfort.This paper focuses on the influence of large window-wall ratio on energy consumption and indoor thermal comfort of an air source heat pump dual supply system.A convection-radiation combined cooling and heating system will be built in office buildings located in hot summer and cold winter areas.The study changed the window-wall ratio to conduct an experimental investigation of the indoor and outdoor heat and humidity environments,the interior surface temperature of the envelope structure,the vertical temperature at various penetration depths（the distance from the window to the room）,the indoor overall and local thermal comfort,and the energy consumption of the system.The main work is as follows:（1）Set up different window-wall ratios,cooling and heating forms of the test bench and design the testing system.A convection-radiation combined cooling and heating system will be built,which using the fan coil as the convection terminal and the dry floor radiation as the radiation terminal.The testing room will have measurement points for interior air temperature and humidity,envelope structure inner surface temperature,and indoor vertical temperature.Based on an equivalent thermal resistance method is proposed to design the equivalent window-wall ratio,and the thickness of aluminum foil insulation cotton is calculated.The window-wall ratio parameters（40%～80%）will be selected based on the office building design code（JGJT67-2019）.The terminal form and operation strategy of air conditioning in winter and summer will also be determined and selected.（2）Effects of different window-wall ratios,heating forms on indoor thermal comfort and energy consumption of air conditioning systems.Floor radiation and fan coil system were used for heating comparison experiment,the increase of the window-wall ratio leads to an increase in the indoor temperature fluctuation.However,the indoor temperature fluctuation is relatively small in the floor radiation heating system.The indoor overall predicted mean vote（PMV）value under the different heating system remains within the range of level I comfort requirements（-0.5～+0.5）with the increase in the window-wall ratio.During the experimental test,under the condition of the fan coil system and a window-wall ratio of 80%,the PMV value of the penetration depth of 0.60m is-1.98 at 4:00,which does not satisfy the thermal comfort requirements.Under the same heating forms,the heating energy consumption increases with an increase of the window-wall ratio.Under the floor radiation system,the energy consumption of the window-wall ratio of 80%increased by 17.21%compared with the window-wall ratio of 50%.Under the fan coil system,the energy consumption of the window-wall ratio of 80%increased by 75.49%compared with the window-wall ratio of 40%.The average hourly heating performance coefficient of the floor radiant heating system is higher,making it more efficient.Therefore,the floor radiant system is recommended for use in winter,and the window-wall ratio should be reduced as much as possible to meet the building’s needs.（3）Effects of different window-wall ratios,cooling forms on indoor thermal comfort and energy consumption of air conditioning systems.Convection-radiation and fan coil system were used for cooling comparison experiment,the increase in the window-wall ratio leads to an increase in the indoor temperature fluctuation.However,the indoor temperature fluctuation is relatively small in the convection-radiation cooling system.The indoor overall PMV value under different cooling system remains within the range of level II comfort requirements（-1.0～+1.0）with the increase in the window-wall ratio.During the experimental test,under the condition of the fan coil system and window-wall ratio of 80%,the PMV value of the penetration depth of 0.60m is 1.26 at 17:30,which does not satisfy the thermal comfort requirements.The energy consumption of the fan coil cooling system increased with an increase in the window-wall ratio,and the energy consumption of the window-wall ratio of80%increased by 7.11%compared with the window-wall ratio of 40%.However,under the convection-radiation system,cooling energy consumption decreased with the increasing of the window-wall ratio due to the larger surface of the non-transparent envelope structure with smaller window-wall ratio,which requires more energy to store cold,and the daily average radiation amount is larger.The energy consumption of the window-wall ratio of 80%decreased by 29.26%compared with the window-wall ratio of 40%under the convection-radiation cooling system.In the case of solar radiation exposure,the indoor thermal comfort is poor under fan coil system,because the fan coil system is inefficient for dealing with radiation load by convection.The average hourly cooling performance coefficient of the convection-radiation cooling system was higher,and provided better thermal comfort in case of solar radiation exposure.Therefore,the convection-radiation cooling system is recommended for use in summer,and the window-wall ratio should be reduced as much as possible to meet the building’s needs.（4）Analysis of solar irradiation effect based on direct solar area.Considering the effect of solar irradiation,it is found that the mean radiation temperature outside the irradiated zone increase only slightly,while the mean radiation temperature inside the irradiated zone increases more.The predicted mean vote outside the indoor radiation zone when solar irradiation is considered（PMV）_irr increased by only 0.01～0.12 compared with that when solar irradiation is not considered（PMV）_ur.However,the（PMV）_irrin the radiation area increased by 0.56～0.87 compared with（PMV）_ur,causing discomfort under the convection-radiation system and severe discomfort occurs under the fan coil system.Thus,the convection-radiation cooling system showed better radiation heat treatment ability.