A new ground source heat pump system combined with radiant heating/cooling is proposed, and the principles and the advantages of the system are analyzed. A demonstration of the system is applied to a rebuilt building...A new ground source heat pump system combined with radiant heating/cooling is proposed, and the principles and the advantages of the system are analyzed. A demonstration of the system is applied to a rebuilt building： Xijindu exhibition hall, which is located in Zhenjiang city in China. Numerical studies on the thermal comfort and energy consumption of the system are carded out by using TRNSYS software. The results indicate that the system with the radiant floor method or the radiant ceiling method shows good thermal comfort without mechanical ventilation in winter. However, the system with either of the methods should add mechanical ventilation to ensure good comfort in summer. At the same level of thermal comfort, it can also be found that the annual energy consumption of the radiant ceiling system is less than that of the radiant floor system.展开更多
The radiant systems consume less energy and provide better thermal comfort as compared to the conventional system,but the main drawback of radiant technology is inability to cater the latent load and condensation.This...The radiant systems consume less energy and provide better thermal comfort as compared to the conventional system,but the main drawback of radiant technology is inability to cater the latent load and condensation.This problem has engaged researchers to push their emphasis on Personalized Conditioning System(PCS).It forms a micro-climate region near the occupant.This study is aimed at PCS combined with a radiant conditioning system,which evaluates the performance of the PCS and compares it with different radiant cooling systems.A radiant cubicle was used to investigate the performance of the PCS for both heating&cooling modes.For heating mode,the Standard Effective Temperature(SET)was calculated with the help of thermal comfort surveys which were in a range of 23.4℃ to 27.3℃.For cooling mode,four different cases compared the performance of the system which are:Conventional Air Conditioning System(CACS),Radiant Cooled Ceiling System(RCCS),Personalized Radiant Conditioning System(PRCS),and both PRCS-RCCS coupled.It was observed that PRCS alone reaches the thermal comfort criteria with low energy consumption.The energy-saving of RCCS-PRCS was achieved 38%when compared with CACS.It can be concluded that PRCS is a new step in the field of thermal comfort.展开更多
The hybrid system with radiant cooling and dedicated outdoor air not only possesses high energy efficiency, but also creates a healthy and comfortable indoor environment. Indoor air quality will be improved by the ded...The hybrid system with radiant cooling and dedicated outdoor air not only possesses high energy efficiency, but also creates a healthy and comfortable indoor environment. Indoor air quality will be improved by the dedicated outdoor air system(DOAS) and indoor thermal comfort can be enhanced by the radiant cooling system(RCS). The optimal air-supply mode of the hybrid system and the corresponding design approach were investigated. A full-scale experimental chamber with various air outlets and the ceiling radiant cooling panels(CRCP) was designed and established. The performances of different air-supply modes along with CRCPs were analyzed by multi-index evaluations. Preliminary investigations were also conducted on the humidity stratification and the control effect of different airflow modes to prevent condensation on CRCP. The overhead supply air is recommended as the best combination mode for the hybrid system after comprehensive comparison of the experiment results. The optimal proportion of CRCP accounting for the total cooling capacities in accord with specific cooling loads is found, which may provide valuable reference for the design and operation of the hybrid system.展开更多
A building model with radiant cooling system was established and the cooling load, indoor temperature, surface temperature of the wails and other parameters in non-cooling and radiant cooling room were calculated by T...A building model with radiant cooling system was established and the cooling load, indoor temperature, surface temperature of the wails and other parameters in non-cooling and radiant cooling room were calculated by TRNSYS. The comparative analysis of the characteristics of attenuation and delay proves that the operation of radiant cooling system increases the degree of temperature attenuation of the room and reduces the inner surface temperature of the wall significantly, but has little effect on the attenuation coefficient and delay time of wall heat transfer. The simulation results also show that the inner surface temperature of the walls in the radiant cooling room is much lower than that in non-cooling room in the day with the maximum cooling load, which reduces the indoor operation temperature largely, and improves the thermal comfort. Finally, according to the analysis of indoor temperature of the rooms with different operation schedules of cooling system, it can be derived that the indoor mean temperature changes with the working time of radiant cooling system, and the operation schedule can be adjusted in practice according to the actual indoor temperature to achieve the integration of energy efficiency and thermal comfort.展开更多
Temperature precision control is one of the most critical issues in metrology laboratories,and this issue has become increasingly stringent in modern society.Radiant air conditioning system,which minimizes vibration t...Temperature precision control is one of the most critical issues in metrology laboratories,and this issue has become increasingly stringent in modern society.Radiant air conditioning system,which minimizes vibration through radiant heat transfer instead of conventional convection,has gained attention but is more sensitive to temperature fluctuations from the cooling source.Considering that phase change materials(PCMs)have the advantage of suppressing water temperature fluctuations,comparative simulations are carried out to analyze the suppressing effectiveness by adding two typical PCMs(paraffin and dimethyl sulfoxide)in water tanks and radiant panels separately.Results indicate that adding paraffin to water tanks has a better effect than dimethyl sulfoxide while it is inverse for radiant panels.Then,the adding volume ratios(paraffin for the water tank is 0.2;dimethyl sulfoxide for radiant panels is 0.1)are provided,when surface temperature fluctuations of radiant panels are suppressed within±0.1 K.Finally,the relationship between the latent heat/thermal conductivity of PCM versus suppressing effect is investigated to provide a reference for the design of radiant air conditioning systems in metrology laboratories.展开更多
The radiant cooling system generally operates with the dedicated outdoor air system （DOAS）. Air supply modes and the corresponding setting parameters of the hybrid system may substantially influence the indoor therm...The radiant cooling system generally operates with the dedicated outdoor air system （DOAS）. Air supply modes and the corresponding setting parameters of the hybrid system may substantially influence the indoor thermal comfort. With target indexes of air diffusion performance index （ADPI） and predicted mean vote （PMV）, the Taguchi method was used to choose the optimal air supply mode and to analyze the significance of different factors on the thermal comfort. The results are expected for conducting the future design and regulation of the hybrid system. Computation fluid dynamics （CFD） simulation as well as verified experiments was performed during the research. Based on the ADPI studies, it is found that the air supply mode of ceiling delivery with ceiling exhaust is an optimized option to apply in DOAS of the hybrid system. Variance analysis results show that influence fact of air supply temperature is the most dominant one to impact the indoor thermal comfort index of PMV.展开更多
A radiant floor cooling system(RFCS)is a high-comfort and low energy consumption system suitable for residential buildings.Radiant floor systems usually work with fresh air,and their operating performance is affected ...A radiant floor cooling system(RFCS)is a high-comfort and low energy consumption system suitable for residential buildings.Radiant floor systems usually work with fresh air,and their operating performance is affected by climatic conditions.Indoor and outdoor environmental disturbances and the system’s control strategy affect the indoor thermal comfort and energy efficiency of the system.Firstly,a multi-story residential building model was established in this study.Transient system simulation program was used to study the operation dynamics of three control strategies of the RFCS based on the calibrated model.Then,the performance of the control strategies in five climate zones in China were compared using multi-criteria decision-making in combination.The results show that control strategy has a negligible effect on condensation risk,but the thermal comfort and economic performance differ for different control strategies.The adaptability of different control strategies varies in different climate zones based on the consideration of multiple factors.The performance of the direct-ground cooling source system is better in Hot summer and warm winter zone.The variable air volume control strategy scores higher in Serve cold and Temperate zones,and the hours exceeding thermal comfort account for less than 3%of the total simulation period.Therefore,it is suggested to choose the RFCS control strategy for residential buildings according to the climate zone characteristics,to increase the energy savings.Our results provide a reliable reference for implementing RFCSs in residential buildings.展开更多
Covering the radiant cooling surface with infrared-transparent membrane effectively improves the condensation resistance and cooling capacity of radiant cooling.However,the air layer structure formed by the infrared-t...Covering the radiant cooling surface with infrared-transparent membrane effectively improves the condensation resistance and cooling capacity of radiant cooling.However,the air layer structure formed by the infrared-transparent and double-layer hollow membranes is easy to destroy,resulting in condensation problems.Inspired by the hollow structure of natural bamboo,an infrared-transparent bubble wrap assisted radiant cooling panel(BWRCP)aiming at improving the strength and cooling capacity was proposed by using the infrared-transparent bubble wrap consisting of infrared-transparent membrane and air-filled pores to layer the radiant cooling panel.Both experimental investigation and numerical calculation of the cooling capacity of the infrared-transparent bubble wrap assisted radiant cooling system were carried out.Experimental results showed that the cooling capacity of BWRCP at condensation-free condition was 93.54 W/m^(2),which was 33%higher than traditional radiant cooling without covering infrared-transparent bubble wrap.Numerical results showed that the air-contact surface temperature of the infrared-transparent bubble wrap was higher than the dew point temperature.It provides condensation-free operation in the thermal environment of 26℃and 45%–80%RH.Therefore,compared with traditional radiant cooling,BWRCP significantly improves the cooling capacity at condensation-free condition.It demonstrated a novel structure design and operation guidance for the high-performance radiant cooling technology.展开更多
To solve the problem of condensation at the radiant cooling terminal,a novel radiant cooling terminal(NRCT)based on the moisture buffering effect is proposed.The NRCT combines traditional radiant cooling terminals wit...To solve the problem of condensation at the radiant cooling terminal,a novel radiant cooling terminal(NRCT)based on the moisture buffering effect is proposed.The NRCT combines traditional radiant cooling terminals with solid humidity conditioning materials(HCM).On this basis,a coupled anti-condensation regulation strategy between the NRCT and the fresh air system was constructed,which utilizes the moisture buffering effect of the HCM to extend the condensation time,and reserves sufficient time for active intervention of personnel and feedback adjustment of the fresh air system.Then,the indoor air parameters are restored to normal design values as a result of the fresh air system.Meanwhile,the HCM releases the adsorbed water vapor,thereby enabling the completion of the desorption process.Using numerical simulation methods to study each step of the anti-condensation regulation strategy,the results indicate that the NRCT can effectively prevent condensation,and it can ensure that condensation does not occur within 20 min after the window is opened,even under extreme weather conditions.Moreover,the anti-condensation effect improves with the thickness increase of the HCM.However,when ensuring the prevention of condensation while expecting the best moisture adsorption effect,there is an optimal value for the thickness of the HCM.Increasing the fresh air supply volume can enable the HCM to complete the desorption process more quickly.In the final steady-state operation process,the HCM can continue to release moisture,achieving sustainable utilization of the HCM.In actual operation,the operational duration of the fresh air system during the moisture desorption process can be regulated by tracking the relative humidity of the outlet to ensure that the HCM completes the adsorption and desorption cycle.This anti-condensation regulation strategy can provide effective guarantee for the non-condensing operation of radiant cooling terminals.展开更多
Pre-dehumidification time(τ_(pre))and pre-dehumidification energy consumption(E_(pre))play important roles in preventing the condensation of moisture on the floors of rooms that use a radiant floor cooling(RFC)system...Pre-dehumidification time(τ_(pre))and pre-dehumidification energy consumption(E_(pre))play important roles in preventing the condensation of moisture on the floors of rooms that use a radiant floor cooling(RFC)system.However,there are few theoretical or experimental studies that focus on these two important quantities.In this study,an artificial neural network(ANN)was used to predict condensation risk for the integration of RFC systems with mixed ventilation(MV),stratum ventilation(SV),and displacement ventilation(DV)systems.A genetic algorithm-back-propagation(GA-BP)neural network model was established to predict τ_(pre) and E_(pre).Both training data and validation data were obtained from tests in a computational fluid dynamics(CFD)simulation.The results show that the established GA-BP model can predict τ_(pre) and E_(pre) well.The coefficient of determination(R^(2))of τ_(pre) and of E_(pre) were,respectively,0.973 and 0.956.For an RFC system integrated with an MV,SV,or DV system,the lowest values of τ_(pre) and E_(pre) were with the DV system,23.1 s and 0.237 kWh,respectively,for a 67.5 m^(3) room.Therefore,the best pre-dehumidification effect was with integration of the DV and RFC systems.This study showed that an ANN-based method can be used for predictive control for condensation prevention in RFC systems.It also provides a novel and effective method by which to assess the pre-dehumidification control of radiant floor surfaces.展开更多
Decoupled radiant cooling units(DRCUs)are capable of increasing the cooling capacity without increasing condensation risks even using a much lower cooling temperature than conventional radiant cooling units(CRCUs).How...Decoupled radiant cooling units(DRCUs)are capable of increasing the cooling capacity without increasing condensation risks even using a much lower cooling temperature than conventional radiant cooling units(CRCUs).However,it is unclear whether DRCUs using low radiant cooling temperature will increase the cooling load of the conditioned indoor spaces.In this study,the cooling load characteristics of a thermal chamber conditioned by a DRCU was investigated through developing a steady-state analysis model suitable for both DRCUs and CRCUs.The total/radiative heat flux,as well as the heat exchange with a thermal manikin and walls were analysed under different surface temperatures of DRCUs.The effect of the emissivity of the thermal chamber’external wall on the cooling load was also investigated.Results indicated that the cooling load under the DRCU was slightly smaller than that under the CRCU when the same operative environment was created.Decreasing the infrared emissivity of the exterior wall’s inner surface could lead to a significant decrease in the cooling load for both the DRCU and CRCU.By decreasing the wall emissivity from 0.9 to 0.1,the total cooling load of the DRCU can be decreased by 8.4%and the heat gain of the exterior wall decreased by 21.6%.This study serves as a reference for developing the analysis model and understanding the load characteristics when DRCUs are used to create the thermal environment for indoor spaces.展开更多
Mean radiant temperature(MRT)is an indispensable physical parameter of indoor thermal environments.Especially in indoor environments controlled by radiant systems,MRT plays an important role in thermal comfort.In orde...Mean radiant temperature(MRT)is an indispensable physical parameter of indoor thermal environments.Especially in indoor environments controlled by radiant systems,MRT plays an important role in thermal comfort.In order to determine MRT of indoor environments controlled by radiant cooling systems quickly and inexpensively,a numerical program is developed in this study.Based on the finite element method(FEM),view factors and radiant temperature fields are numerically calculated.The singular solution problem generated by FEM is corrected using the Monte Carlo method.The numerical program is validated against the results of an experiment performed in a radiant cooling laboratory and the reported data from previous studies.Then radiant temperature fields of different shaped surfaces in a radiant cooling indoor environment are predicted,and thermal comfort level is preliminarily evaluated.展开更多
Hydronic heating and cooling systems are considered the most efficient, greenest technology known to man for the efficient distribution of warmth and cooling;in other words, the ideal human comfort experience. For peo...Hydronic heating and cooling systems are considered the most efficient, greenest technology known to man for the efficient distribution of warmth and cooling;in other words, the ideal human comfort experience. For people who may not know what hydronics are, here’s the definition: Hydronics: A means of transferring the energy required for heating and cooling buildings utilizing water as the primary medium in an effort to maintain good human comfort and conserve energy resources. And while we are in definition mode, allow me to introduce a couple of other terms that are critically important. Comfort: My definition of comfort is being in a state of wellbeing, or not being aware of your surroundings. In this state, you are not hot, nor are you cold. Your sinuses are not too dry, nor is it too humid, and there is not a lot of noise in the background associated with the delivery of comfort. In short, if you have to think about your physical condition, you are probably not comfortable. Simply stated, if you are truly comfortable, you will not be thinking about it. Mean Radiant Temperature: Mean radiant temperature, or MRT for short, is one of those things that cannot (normally) be seen by the bare human eye, but is the primary dictator of excellent human comfort. By definition, MRT is the temperature of those solid items surrounding your body. When the MRT is high, human comfort is achieved with a lower air temperature. When the air temperature is high, good human comfort is achieved with a lower MRT. MRT can be seen using an infrared camera, but most people do not have access to this wonderful technology. Before I go into my dissertation, I want to quickly dispel a myth. People have been taught over the years that “heat rises.” This statement in and of itself is incorrect. Hot fluids rise. Hot air or hot water rise because of their differences in buoyancy compared to cooler surrounding fluids. Radiant energy travels in all directions, through the path of least resistance, including in a downward direction. The best explanation for comparison purposes is to think of being outside on a cool winter day when the sun is shining brightly and you are standing next to a dark colored wall. Your body can sense the radiant energy surrounding your body, and your body feels warmer than it really is due to this exposure to a higher MRT. Another prime example is sitting next to a campfire on a clear starlit night. Even though the ambient air temperature is low, your body can feel the radiation coming from the fire, and it feels warm and comforting on the side that is facing the fire. Your backside that is not facing the fire feels much cooler than the side that is facing the fire, so we rotate in an effort to even out this radiant exposure. If radiant energy only traveled upward, as in “heat rises,” we would have to stand on top of the sun in order to realize any comfort due to radiant energy. As was already proved in our previous statement about MRT, such is not the case. Controlling heat loss from our bodies by manipulating the MRT will guarantee that most people will be comfortable under all conditions. As can be seen from the above graphic, radiational losses account for nearly half of the human body’s heat loss.展开更多
Compared with traditional convection air conditioning,the radiant cooling(RC)system has higher energy-saving potential and better comfort.At present,the particle swarm optimization(PSO)algorithm is one of the most adv...Compared with traditional convection air conditioning,the radiant cooling(RC)system has higher energy-saving potential and better comfort.At present,the particle swarm optimization(PSO)algorithm is one of the most advanced methods to optimize the design of indoor radiant terminals.However,this method requires to discretize the design domain in advance.If the geometric division is rough,the accuracy of the optimized results will be too low.To improve the accuracy of the calculation results,the geometric division needs to be refined,but it will greatly increase the calculation load.For each new geometric model,users need to determine a reasonable geometric division every time,which is very time consuming.To solve that problem,this investigation proposed a parameterized level set method(PLSM)to inversely design the area,shape,and locations of the radiant terminal.It not only does not need to discretize the design domain in advance,but also can realize the continuous topological change of the radiant terminal region.The results show that the PLSM can realize the continuous topological transformation of geometric shapes,and the final result of the average absolute value of PMV(∣PMV∣avg)around the occupants achieved 0.066.To enhance the practical application of the optimized results,K-means cluster analysis is used to regularize the shape of the radiation terminal region.The corresponding average∣PMV∣around the occupants is 0.102,which is also within an acceptable range.All in all,PLSM can be used to inversely design the RC systems,which provides an effective design method for realizing accurate control of the indoor environment using the RC systems.展开更多
The recent significant rise in space cooling energy demand due to the massive use of air-conditioning systems has adversely changed buildings’energy use patterns globally.The updated energy technology perspectives hi...The recent significant rise in space cooling energy demand due to the massive use of air-conditioning systems has adversely changed buildings’energy use patterns globally.The updated energy technology perspectives highlight the need for innovative cooling systems to address this growing cooling demand.Phase change material embedded radiant chilled ceiling(PCM-RCC)has lately acquired popularity as they offer more efficient space cooling together with further demand-side flexibility.Recent advancements in PCM-RCC applications have increased the necessity for reliable simulation models to assist professionals in identifying improved designs and operating settings.In this study,a transient simulation model of PCM-RCC has been developed and validated using measured data in a full-scale test cabin equipped with newly developed PCM ceiling panels.This model,developed in the TRNSYS simulation studio,includes Type 399 that uses the Crank-Nicolson algorithm coupled with the enthalpy function to solve transient heat transfer in PCM ceiling panels.The developed model is validated in both free-running and active operation modes,and its quality is then evaluated using several validation metrics.The results obtained in multiple operating scenarios confirm that the model simulates the transient behaviour of the PCM-RCC system with an accuracy within±10%.Aided by this validated model,which offers the user detailed flexibilities in the system design and its associated operating schemas,PCM-RCC’s potentials regarding peak load shifting,energy savings,and enhanced thermal comfort can be investigated more reliably.展开更多
With the increasing size of the waiting hall,the large-area use of transparent envelope materials makes the interior surface temperature of the envelope too high,which puts forward higher requirements for the control ...With the increasing size of the waiting hall,the large-area use of transparent envelope materials makes the interior surface temperature of the envelope too high,which puts forward higher requirements for the control of environment and thermal comfort indoors.In this paper,the characteristics of indoor temperature distribution,relative humidity distribution and thermal comfort under the all air system(AAs)and the radiant floor cooling and wall cooling combined with air supply system(RC/ASs)were investigated in the large spaces.The computational fluid dynamics(CFD)method was used,and the performance of the CFD model was validated by comparing the measured results with CFD simulation results in the AAs.The numerical results clearly showed that the temperature and relative humidity indoors could satisfy the design requirement both in the AAs and RC/ASs.The indoor air distribution in most areas under the RC/ASs was more uniform based on the indoor heat and humidity requirements under the cooling load of measured day.In the AAs,the total cooling capacity of air conditioning unit was the highest when indoor thermal comfort was the best,that meant that to achieve the best working condition,the air-conditioning system need high energy consumption.Meanwhile,the RC/ASs addressed the problem that the temperature around the seated passengers in the waiting area was relatively high in the AAs.This paper will provide reference for the air conditioning system design in the similar large spaces in the future.展开更多
INTRODUCTION The recently completed Easton Collection Center in Flagstaff,Arizona,is the latest addition to The Museum of Northern Arizona(MNA).The Museum of Northern Arizona is a private institution founded in 1928 w...INTRODUCTION The recently completed Easton Collection Center in Flagstaff,Arizona,is the latest addition to The Museum of Northern Arizona(MNA).The Museum of Northern Arizona is a private institution founded in 1928 with the mission to inspire a sense of love and responsibility for the beauty and diversity of the Colorado Plateau through collecting,studying,interpreting,and preserving the region’s natural and cultural heritage.The new Easton Collection Center facility consists of just over 17,000 square feet of floor area.It was designed to house a significant portion of MNA’s extensive and valuable cultural and natural science collections,providing appropriate indoor environmental conditions in a sustainable way and upon completion of construction was certified LEED Platinum by the United States Green Building Council.展开更多
基金The National Natural Science Foundation of China(No. 51036001 )the Natural Science Foundation of Jiangsu Province(No. BK2010043)
文摘A new ground source heat pump system combined with radiant heating/cooling is proposed, and the principles and the advantages of the system are analyzed. A demonstration of the system is applied to a rebuilt building： Xijindu exhibition hall, which is located in Zhenjiang city in China. Numerical studies on the thermal comfort and energy consumption of the system are carded out by using TRNSYS software. The results indicate that the system with the radiant floor method or the radiant ceiling method shows good thermal comfort without mechanical ventilation in winter. However, the system with either of the methods should add mechanical ventilation to ensure good comfort in summer. At the same level of thermal comfort, it can also be found that the annual energy consumption of the radiant ceiling system is less than that of the radiant floor system.
文摘The radiant systems consume less energy and provide better thermal comfort as compared to the conventional system,but the main drawback of radiant technology is inability to cater the latent load and condensation.This problem has engaged researchers to push their emphasis on Personalized Conditioning System(PCS).It forms a micro-climate region near the occupant.This study is aimed at PCS combined with a radiant conditioning system,which evaluates the performance of the PCS and compares it with different radiant cooling systems.A radiant cubicle was used to investigate the performance of the PCS for both heating&cooling modes.For heating mode,the Standard Effective Temperature(SET)was calculated with the help of thermal comfort surveys which were in a range of 23.4℃ to 27.3℃.For cooling mode,four different cases compared the performance of the system which are:Conventional Air Conditioning System(CACS),Radiant Cooled Ceiling System(RCCS),Personalized Radiant Conditioning System(PRCS),and both PRCS-RCCS coupled.It was observed that PRCS alone reaches the thermal comfort criteria with low energy consumption.The energy-saving of RCCS-PRCS was achieved 38%when compared with CACS.It can be concluded that PRCS is a new step in the field of thermal comfort.
基金Project(51178298)supported by the National Natural Science Foundation of China
文摘The hybrid system with radiant cooling and dedicated outdoor air not only possesses high energy efficiency, but also creates a healthy and comfortable indoor environment. Indoor air quality will be improved by the dedicated outdoor air system(DOAS) and indoor thermal comfort can be enhanced by the radiant cooling system(RCS). The optimal air-supply mode of the hybrid system and the corresponding design approach were investigated. A full-scale experimental chamber with various air outlets and the ceiling radiant cooling panels(CRCP) was designed and established. The performances of different air-supply modes along with CRCPs were analyzed by multi-index evaluations. Preliminary investigations were also conducted on the humidity stratification and the control effect of different airflow modes to prevent condensation on CRCP. The overhead supply air is recommended as the best combination mode for the hybrid system after comprehensive comparison of the experiment results. The optimal proportion of CRCP accounting for the total cooling capacities in accord with specific cooling loads is found, which may provide valuable reference for the design and operation of the hybrid system.
基金Project(2010DFA72740) supported by the International Science & Technology Cooperation Program of China
文摘A building model with radiant cooling system was established and the cooling load, indoor temperature, surface temperature of the wails and other parameters in non-cooling and radiant cooling room were calculated by TRNSYS. The comparative analysis of the characteristics of attenuation and delay proves that the operation of radiant cooling system increases the degree of temperature attenuation of the room and reduces the inner surface temperature of the wall significantly, but has little effect on the attenuation coefficient and delay time of wall heat transfer. The simulation results also show that the inner surface temperature of the walls in the radiant cooling room is much lower than that in non-cooling room in the day with the maximum cooling load, which reduces the indoor operation temperature largely, and improves the thermal comfort. Finally, according to the analysis of indoor temperature of the rooms with different operation schedules of cooling system, it can be derived that the indoor mean temperature changes with the working time of radiant cooling system, and the operation schedule can be adjusted in practice according to the actual indoor temperature to achieve the integration of energy efficiency and thermal comfort.
基金support from the Key Projects in the National Science&Technology Program(Grant No.2022YFE0210200)Open Foundation of CAS Key Laboratory of Cryogenics,TIPC(Grant No.CRYO202213)Natural Science Foundation of Liaoning Province(Grant No.2023-MSBA-099).
文摘Temperature precision control is one of the most critical issues in metrology laboratories,and this issue has become increasingly stringent in modern society.Radiant air conditioning system,which minimizes vibration through radiant heat transfer instead of conventional convection,has gained attention but is more sensitive to temperature fluctuations from the cooling source.Considering that phase change materials(PCMs)have the advantage of suppressing water temperature fluctuations,comparative simulations are carried out to analyze the suppressing effectiveness by adding two typical PCMs(paraffin and dimethyl sulfoxide)in water tanks and radiant panels separately.Results indicate that adding paraffin to water tanks has a better effect than dimethyl sulfoxide while it is inverse for radiant panels.Then,the adding volume ratios(paraffin for the water tank is 0.2;dimethyl sulfoxide for radiant panels is 0.1)are provided,when surface temperature fluctuations of radiant panels are suppressed within±0.1 K.Finally,the relationship between the latent heat/thermal conductivity of PCM versus suppressing effect is investigated to provide a reference for the design of radiant air conditioning systems in metrology laboratories.
文摘The radiant cooling system generally operates with the dedicated outdoor air system （DOAS）. Air supply modes and the corresponding setting parameters of the hybrid system may substantially influence the indoor thermal comfort. With target indexes of air diffusion performance index （ADPI） and predicted mean vote （PMV）, the Taguchi method was used to choose the optimal air supply mode and to analyze the significance of different factors on the thermal comfort. The results are expected for conducting the future design and regulation of the hybrid system. Computation fluid dynamics （CFD） simulation as well as verified experiments was performed during the research. Based on the ADPI studies, it is found that the air supply mode of ceiling delivery with ceiling exhaust is an optimized option to apply in DOAS of the hybrid system. Variance analysis results show that influence fact of air supply temperature is the most dominant one to impact the indoor thermal comfort index of PMV.
基金This work was funded by the Natural Science Foundation of Shandong Province(ZR2021ME199,ZR2021ME237)the Support Plan for Outstanding Youth Innovation Team in Colleges and Universities of Shandong Province(2019KJG005).This work was also supported by the Plan of Introduction and Cultivation for Young Innovative Talents in Colleges and Universities of Shandong Province,and Funding for Domestic Visiting Scholars at Shandong Jianzhu University.
文摘A radiant floor cooling system(RFCS)is a high-comfort and low energy consumption system suitable for residential buildings.Radiant floor systems usually work with fresh air,and their operating performance is affected by climatic conditions.Indoor and outdoor environmental disturbances and the system’s control strategy affect the indoor thermal comfort and energy efficiency of the system.Firstly,a multi-story residential building model was established in this study.Transient system simulation program was used to study the operation dynamics of three control strategies of the RFCS based on the calibrated model.Then,the performance of the control strategies in five climate zones in China were compared using multi-criteria decision-making in combination.The results show that control strategy has a negligible effect on condensation risk,but the thermal comfort and economic performance differ for different control strategies.The adaptability of different control strategies varies in different climate zones based on the consideration of multiple factors.The performance of the direct-ground cooling source system is better in Hot summer and warm winter zone.The variable air volume control strategy scores higher in Serve cold and Temperate zones,and the hours exceeding thermal comfort account for less than 3%of the total simulation period.Therefore,it is suggested to choose the RFCS control strategy for residential buildings according to the climate zone characteristics,to increase the energy savings.Our results provide a reliable reference for implementing RFCSs in residential buildings.
基金sponsored by the National Natural Science Foundation of China(No.5231101074)and(No.52378092).
文摘Covering the radiant cooling surface with infrared-transparent membrane effectively improves the condensation resistance and cooling capacity of radiant cooling.However,the air layer structure formed by the infrared-transparent and double-layer hollow membranes is easy to destroy,resulting in condensation problems.Inspired by the hollow structure of natural bamboo,an infrared-transparent bubble wrap assisted radiant cooling panel(BWRCP)aiming at improving the strength and cooling capacity was proposed by using the infrared-transparent bubble wrap consisting of infrared-transparent membrane and air-filled pores to layer the radiant cooling panel.Both experimental investigation and numerical calculation of the cooling capacity of the infrared-transparent bubble wrap assisted radiant cooling system were carried out.Experimental results showed that the cooling capacity of BWRCP at condensation-free condition was 93.54 W/m^(2),which was 33%higher than traditional radiant cooling without covering infrared-transparent bubble wrap.Numerical results showed that the air-contact surface temperature of the infrared-transparent bubble wrap was higher than the dew point temperature.It provides condensation-free operation in the thermal environment of 26℃and 45%–80%RH.Therefore,compared with traditional radiant cooling,BWRCP significantly improves the cooling capacity at condensation-free condition.It demonstrated a novel structure design and operation guidance for the high-performance radiant cooling technology.
基金supported by the National Natural Science Foundation of China[No.52276179]the Natural Science Foundation of Jiangsu Province[No.BK20231425]。
文摘To solve the problem of condensation at the radiant cooling terminal,a novel radiant cooling terminal(NRCT)based on the moisture buffering effect is proposed.The NRCT combines traditional radiant cooling terminals with solid humidity conditioning materials(HCM).On this basis,a coupled anti-condensation regulation strategy between the NRCT and the fresh air system was constructed,which utilizes the moisture buffering effect of the HCM to extend the condensation time,and reserves sufficient time for active intervention of personnel and feedback adjustment of the fresh air system.Then,the indoor air parameters are restored to normal design values as a result of the fresh air system.Meanwhile,the HCM releases the adsorbed water vapor,thereby enabling the completion of the desorption process.Using numerical simulation methods to study each step of the anti-condensation regulation strategy,the results indicate that the NRCT can effectively prevent condensation,and it can ensure that condensation does not occur within 20 min after the window is opened,even under extreme weather conditions.Moreover,the anti-condensation effect improves with the thickness increase of the HCM.However,when ensuring the prevention of condensation while expecting the best moisture adsorption effect,there is an optimal value for the thickness of the HCM.Increasing the fresh air supply volume can enable the HCM to complete the desorption process more quickly.In the final steady-state operation process,the HCM can continue to release moisture,achieving sustainable utilization of the HCM.In actual operation,the operational duration of the fresh air system during the moisture desorption process can be regulated by tracking the relative humidity of the outlet to ensure that the HCM completes the adsorption and desorption cycle.This anti-condensation regulation strategy can provide effective guarantee for the non-condensing operation of radiant cooling terminals.
基金funded by the Natural Science Foundation of Shan-dong Province(ZR2021ME199,ZR2020ME211)the Support Plan for Outstanding Youth Innovation Team in Colleges and Universities of Shandong Province(2019KJG005)supported by the Plan of Introduction and Cultivation for Young Innovative Talents in Colleges and Universities of Shandong Province.
文摘Pre-dehumidification time(τ_(pre))and pre-dehumidification energy consumption(E_(pre))play important roles in preventing the condensation of moisture on the floors of rooms that use a radiant floor cooling(RFC)system.However,there are few theoretical or experimental studies that focus on these two important quantities.In this study,an artificial neural network(ANN)was used to predict condensation risk for the integration of RFC systems with mixed ventilation(MV),stratum ventilation(SV),and displacement ventilation(DV)systems.A genetic algorithm-back-propagation(GA-BP)neural network model was established to predict τ_(pre) and E_(pre).Both training data and validation data were obtained from tests in a computational fluid dynamics(CFD)simulation.The results show that the established GA-BP model can predict τ_(pre) and E_(pre) well.The coefficient of determination(R^(2))of τ_(pre) and of E_(pre) were,respectively,0.973 and 0.956.For an RFC system integrated with an MV,SV,or DV system,the lowest values of τ_(pre) and E_(pre) were with the DV system,23.1 s and 0.237 kWh,respectively,for a 67.5 m^(3) room.Therefore,the best pre-dehumidification effect was with integration of the DV and RFC systems.This study showed that an ANN-based method can be used for predictive control for condensation prevention in RFC systems.It also provides a novel and effective method by which to assess the pre-dehumidification control of radiant floor surfaces.
基金The study was supported by grants from the Research Grants Council of the Hong Kong Special Administrative Region,China(No.11212919)the National Natural Science Foundation of China(No.52078144).
文摘Decoupled radiant cooling units(DRCUs)are capable of increasing the cooling capacity without increasing condensation risks even using a much lower cooling temperature than conventional radiant cooling units(CRCUs).However,it is unclear whether DRCUs using low radiant cooling temperature will increase the cooling load of the conditioned indoor spaces.In this study,the cooling load characteristics of a thermal chamber conditioned by a DRCU was investigated through developing a steady-state analysis model suitable for both DRCUs and CRCUs.The total/radiative heat flux,as well as the heat exchange with a thermal manikin and walls were analysed under different surface temperatures of DRCUs.The effect of the emissivity of the thermal chamber’external wall on the cooling load was also investigated.Results indicated that the cooling load under the DRCU was slightly smaller than that under the CRCU when the same operative environment was created.Decreasing the infrared emissivity of the exterior wall’s inner surface could lead to a significant decrease in the cooling load for both the DRCU and CRCU.By decreasing the wall emissivity from 0.9 to 0.1,the total cooling load of the DRCU can be decreased by 8.4%and the heat gain of the exterior wall decreased by 21.6%.This study serves as a reference for developing the analysis model and understanding the load characteristics when DRCUs are used to create the thermal environment for indoor spaces.
基金supported by the National Natural Science Foundation of China(No.51878255)China Scholarship Council(No.202106130042)。
文摘Mean radiant temperature(MRT)is an indispensable physical parameter of indoor thermal environments.Especially in indoor environments controlled by radiant systems,MRT plays an important role in thermal comfort.In order to determine MRT of indoor environments controlled by radiant cooling systems quickly and inexpensively,a numerical program is developed in this study.Based on the finite element method(FEM),view factors and radiant temperature fields are numerically calculated.The singular solution problem generated by FEM is corrected using the Monte Carlo method.The numerical program is validated against the results of an experiment performed in a radiant cooling laboratory and the reported data from previous studies.Then radiant temperature fields of different shaped surfaces in a radiant cooling indoor environment are predicted,and thermal comfort level is preliminarily evaluated.
文摘Hydronic heating and cooling systems are considered the most efficient, greenest technology known to man for the efficient distribution of warmth and cooling;in other words, the ideal human comfort experience. For people who may not know what hydronics are, here’s the definition: Hydronics: A means of transferring the energy required for heating and cooling buildings utilizing water as the primary medium in an effort to maintain good human comfort and conserve energy resources. And while we are in definition mode, allow me to introduce a couple of other terms that are critically important. Comfort: My definition of comfort is being in a state of wellbeing, or not being aware of your surroundings. In this state, you are not hot, nor are you cold. Your sinuses are not too dry, nor is it too humid, and there is not a lot of noise in the background associated with the delivery of comfort. In short, if you have to think about your physical condition, you are probably not comfortable. Simply stated, if you are truly comfortable, you will not be thinking about it. Mean Radiant Temperature: Mean radiant temperature, or MRT for short, is one of those things that cannot (normally) be seen by the bare human eye, but is the primary dictator of excellent human comfort. By definition, MRT is the temperature of those solid items surrounding your body. When the MRT is high, human comfort is achieved with a lower air temperature. When the air temperature is high, good human comfort is achieved with a lower MRT. MRT can be seen using an infrared camera, but most people do not have access to this wonderful technology. Before I go into my dissertation, I want to quickly dispel a myth. People have been taught over the years that “heat rises.” This statement in and of itself is incorrect. Hot fluids rise. Hot air or hot water rise because of their differences in buoyancy compared to cooler surrounding fluids. Radiant energy travels in all directions, through the path of least resistance, including in a downward direction. The best explanation for comparison purposes is to think of being outside on a cool winter day when the sun is shining brightly and you are standing next to a dark colored wall. Your body can sense the radiant energy surrounding your body, and your body feels warmer than it really is due to this exposure to a higher MRT. Another prime example is sitting next to a campfire on a clear starlit night. Even though the ambient air temperature is low, your body can feel the radiation coming from the fire, and it feels warm and comforting on the side that is facing the fire. Your backside that is not facing the fire feels much cooler than the side that is facing the fire, so we rotate in an effort to even out this radiant exposure. If radiant energy only traveled upward, as in “heat rises,” we would have to stand on top of the sun in order to realize any comfort due to radiant energy. As was already proved in our previous statement about MRT, such is not the case. Controlling heat loss from our bodies by manipulating the MRT will guarantee that most people will be comfortable under all conditions. As can be seen from the above graphic, radiational losses account for nearly half of the human body’s heat loss.
基金supported by the National Natural Science Foundation of China(NSFC)through Grant No.52208098by the China Postdoctoral Science Foundation through Grant No.2022M710689by Jiangsu Planned Projects for Postdoctoral Research Funds through Grant No.2021K069A.
文摘Compared with traditional convection air conditioning,the radiant cooling(RC)system has higher energy-saving potential and better comfort.At present,the particle swarm optimization(PSO)algorithm is one of the most advanced methods to optimize the design of indoor radiant terminals.However,this method requires to discretize the design domain in advance.If the geometric division is rough,the accuracy of the optimized results will be too low.To improve the accuracy of the calculation results,the geometric division needs to be refined,but it will greatly increase the calculation load.For each new geometric model,users need to determine a reasonable geometric division every time,which is very time consuming.To solve that problem,this investigation proposed a parameterized level set method(PLSM)to inversely design the area,shape,and locations of the radiant terminal.It not only does not need to discretize the design domain in advance,but also can realize the continuous topological change of the radiant terminal region.The results show that the PLSM can realize the continuous topological transformation of geometric shapes,and the final result of the average absolute value of PMV(∣PMV∣avg)around the occupants achieved 0.066.To enhance the practical application of the optimized results,K-means cluster analysis is used to regularize the shape of the radiation terminal region.The corresponding average∣PMV∣around the occupants is 0.102,which is also within an acceptable range.All in all,PLSM can be used to inversely design the RC systems,which provides an effective design method for realizing accurate control of the indoor environment using the RC systems.
文摘The recent significant rise in space cooling energy demand due to the massive use of air-conditioning systems has adversely changed buildings’energy use patterns globally.The updated energy technology perspectives highlight the need for innovative cooling systems to address this growing cooling demand.Phase change material embedded radiant chilled ceiling(PCM-RCC)has lately acquired popularity as they offer more efficient space cooling together with further demand-side flexibility.Recent advancements in PCM-RCC applications have increased the necessity for reliable simulation models to assist professionals in identifying improved designs and operating settings.In this study,a transient simulation model of PCM-RCC has been developed and validated using measured data in a full-scale test cabin equipped with newly developed PCM ceiling panels.This model,developed in the TRNSYS simulation studio,includes Type 399 that uses the Crank-Nicolson algorithm coupled with the enthalpy function to solve transient heat transfer in PCM ceiling panels.The developed model is validated in both free-running and active operation modes,and its quality is then evaluated using several validation metrics.The results obtained in multiple operating scenarios confirm that the model simulates the transient behaviour of the PCM-RCC system with an accuracy within±10%.Aided by this validated model,which offers the user detailed flexibilities in the system design and its associated operating schemas,PCM-RCC’s potentials regarding peak load shifting,energy savings,and enhanced thermal comfort can be investigated more reliably.
基金This work was support by the National Key R&D Program of China(No.2016YFC0700200).
文摘With the increasing size of the waiting hall,the large-area use of transparent envelope materials makes the interior surface temperature of the envelope too high,which puts forward higher requirements for the control of environment and thermal comfort indoors.In this paper,the characteristics of indoor temperature distribution,relative humidity distribution and thermal comfort under the all air system(AAs)and the radiant floor cooling and wall cooling combined with air supply system(RC/ASs)were investigated in the large spaces.The computational fluid dynamics(CFD)method was used,and the performance of the CFD model was validated by comparing the measured results with CFD simulation results in the AAs.The numerical results clearly showed that the temperature and relative humidity indoors could satisfy the design requirement both in the AAs and RC/ASs.The indoor air distribution in most areas under the RC/ASs was more uniform based on the indoor heat and humidity requirements under the cooling load of measured day.In the AAs,the total cooling capacity of air conditioning unit was the highest when indoor thermal comfort was the best,that meant that to achieve the best working condition,the air-conditioning system need high energy consumption.Meanwhile,the RC/ASs addressed the problem that the temperature around the seated passengers in the waiting area was relatively high in the AAs.This paper will provide reference for the air conditioning system design in the similar large spaces in the future.
文摘INTRODUCTION The recently completed Easton Collection Center in Flagstaff,Arizona,is the latest addition to The Museum of Northern Arizona(MNA).The Museum of Northern Arizona is a private institution founded in 1928 with the mission to inspire a sense of love and responsibility for the beauty and diversity of the Colorado Plateau through collecting,studying,interpreting,and preserving the region’s natural and cultural heritage.The new Easton Collection Center facility consists of just over 17,000 square feet of floor area.It was designed to house a significant portion of MNA’s extensive and valuable cultural and natural science collections,providing appropriate indoor environmental conditions in a sustainable way and upon completion of construction was certified LEED Platinum by the United States Green Building Council.
