| Air carrying energy radiant air-conditioning system is a new form of radiant airconditioning that can meet the requirements of both summer cooling and winter heating.In recent years,researches have mostly centered on ceiling-mounted applications,but there are still insufficient researches on terminal structure optimization,energy-carrying air energy utilization,and indoor environment control.With the development and promotion of prefabricated building,prefabricated wallboard is widely used as decoration integrated wall because of its high manufacturing efficiency and decoration integration.In order to realize the complementary advantages of radiation and convection,improve indoor comfort and optimize indoor air energy distribution,this paper proposes an airconditioning system based on prefabricated wallboard.Through theoretical analysis,mathematical model prediction and numerical simulation,the structural parameters of the composite terminal of prefabricated air carrying energy air-conditioning system are studied and determined,and the effects of different terminal forms are compared.The influence rules of different operating parameters on the heat transfer performance,indoor comfort and energy saving of the optimal terminal are analyzed,and the recommended range is given.Firstly,according to the working mechanism of the prefabricated air carrying energy air-conditioning system,the heat transfer process of the prefabricated composite terminal was analyzed theoretically.It is clear that the main factors affecting the heat transfer performance of the composite terminal are the thermal parameters of the indoor radiant panel,the form of the indoor air supply outlet and the operating parameters of the composite terminal.And then based on the theoretical relationship of heat balance,the Matlab heat transfer solution model is constructed.Secondly,the composite terminal indoor radiant panel material and its heat transfer performance were studied to explore the feasibility of the prefabricated air carrying energy air-conditioning system.Matlab is used to predict the effect of emissivity and thermal conductivity,which are the key thermal parameters affecting the heat transfer performance of composite terminal indoor radiant panel.The results show that the increase of emissivity has a significant effect on the radiation heat transfer of the radiant panel,while the influence range of thermal conductivity is relatively limited.When the thermal conductivity is greater than 1W /(m·K),the composition of the composite terminal heat transfer tends to remain unchanged.Combined with the current situation of market application,four kinds of wall panels on the market,including aluminum magnesium alloy integrated wallboard,cellulose fiber cement board,bamboo fiber integrated wallboard and stone plastic integrated wallboard,are selected for Fluent simulation and comparison.The results show that the cellulose fiber cement board with thermal conductivity of 1.11W/(m·K)and emissivity of 0.96 is the recommended material for the composite terminal indoor radiant panel of the prefabricated air carrying energy air-conditioning system.The room temperature can be reduced from 30 ℃ to 27 ℃within 5 minutes,and it can reach steady state within 30 minutes.Thirdly,the indoor air supply outlet form of composite terminal was studied to optimize the application effect of the prefabricated air carrying energy air-conditioning system.It is found that single and double side slit type composite terminals with different installation modes can create the supply air flow pattern of displacement ventilation and provide comfortable indoor environment in summer.When the air supply outlet velocity of the slit type indoor air outlet in summer is between 0.1m/s～0.35m/s,it can effectively avoid the risk of draft sensation and meet the air supply accessibility requirements of rooms with a span of 6m.Furthermore,the orifice type composite terminal is proposed to explore the diversity of indoor air supply outlet forms.Through the orthogonal experiment,it is determined that the geometric parameters of the structure can give the best consideration to the indoor environment comfort and its own resistance characteristics when the orifice panel opening rate is 0.5%,the aperture is 9mm,the orifice panel height is 1.4m,and the thickness of the inner hollow cavity at the composite terminal is 50 mm.The outflow temperature and velocity of the structure decays quickly.The non-uniformity coefficient of temperature field is 0.011,the velocity is between0.1m/s and 0.2m/s It can create an environment with uniform temperature distribution and no air flow dead zone.Then,the application effects of slit type composite terminal,orifice type composite terminal and traditional mixed ventilation terminal were compared in winter and summer to analyze the advantages of the prefabricated air carrying energy air-conditioning system.The results show that in summer,the prefabricated composite terminal can create a more comfortable and uniform indoor environment,and has a stronger ability to bear the human load under the combined effect of radiation and convection.The average temperature of human body surface under the effect of slit type composite terminal and orifice type composite terminal is 1.53 ℃ and 1.15 ℃ lower than that under the effect of traditional mixed ventilation terminal,respectively.The average indoor radiation temperature is1.49 ℃ and 0.89 ℃ lower than that under the effect of traditional mixed ventilation terminal,respectively.In the aspect of energy saving,the energy utilization coefficients of traditional mixed ventilation terminal,slit type composite terminal and orifice type composite terminal are 1.03,1.18 and 1.14 respectively.The prefabricated composite terminal can better distribute and utilize the air carrying energy.In winter,the indoor average radiation temperature of the prefabricated composite terminal is about 0.6 ℃higher than that of the mixed ventilation terminal,and its PMV index is more comfortable.In the aspect of energy saving,the energy utilization coefficients of traditional mixed ventilation terminal,slit type composite terminal and orifice type composite terminal are0.90,0.91 and 1.04 respectively,which indicates that orifice type composite terminal is the one that can realize the reasonable distribution and utilization of air carrying energy in winter.Therefore,the orifice type composite terminal is the optimal terminal form to realize the integrated application of winter and summer.Finally,the operating conditions of 25 groups of different supply air speeds and temperatures in winter and summer were simulated to determine the recommended range of operating parameters for the optimal terminal of the prefabricated air carrying energy air-conditioning system in winter and summer.Considering the comfort evaluation index and energy utilization coefficient,the recommended operation parameters range of orifice type composite terminal in winter and summer were divided.Furthermore,TOPSIS method was used to determine the optimal operation parameters in winter and summer.In summer,the optimal operation parameters are composite terminal outlet air temperature of 17 ℃ and composite terminal indoor air supply orifice speed of 3.5m/s;in winter,the optimal operation parameters are composite terminal outlet air temperature of 30 ℃ and composite terminal indoor air supply orifice speed of 2.5m/s.Based on this,the reference design range of operation parameters can be provided for similar application scenarios with different requirements. |
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