辐射供冷—置换通风室内热环境及动态响应特性研究
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摘要
随着经济的发展和人们生活水平的提高,空调得到越来越广的应用,且人们对空调室内环境的舒适性、室内空气品质以及能耗问题也越来越关注。辐射供冷与置换通风结合的复合空调是一种经济、节能、舒适性好的空调系统形式,而逐渐得到研究和应用。
本文首先分析总结复合空调的热、湿环境控制指标,在利用已有实验结果验证CFD数值仿真结果的基础上,讨论了网格划分密集程度对模拟结果的影响;然后对室内冷顶板的传热过程建立了数学模型,分析了各结构参数对冷顶板供冷能力以及表面温度均匀性的影响,进一步通过数值仿真结果显示了顶板表面温度分布均匀性对室内热环境的影响。
由于供冷参数的不同组合会导致置换通风与辐射冷板复合空调室内热湿环境及系统运行费用的不同,因此本文接着利用正交法设计了5因素5水平实验方案,模拟分析了各供冷参数与热舒适性指标PMV的相关性,通过级差法和方差分析法得出了送风温度、速度及相对湿度、冷板表面温度及冷板与天花板面积比等参数对室内热舒适影响作用强弱的先后顺序和最佳组合供冷参数;然后,就对舒适性影响最显著的因素—送风速度的变化所引起的室内热环境的变化过程进行了动态模拟,分析了室内工作区和非工作区温、湿度随时间的变化规律,表明室内热湿状况再次达到稳态所需的响应时间长,但是,冷顶板表面出现结露的可能性也很小。故对置换通风-辐射供冷复合空调系统不建议采用变风量调节的方案。这一结论可为复合空调系统设计参数的确定以及运行调节方案的制定提供指导。
最后在最佳组合工况的基础上,以西安地区的室外气象条件以及两种常用墙体的结构和物理特性为准,通过调节辐射冷顶板的供冷面积对办公室从上午8:00到下午18:00的室内环境进行了模拟,得出了不同时刻的优化控制方案。分析了不同外墙结构类型和辐射冷顶板开启模式对室内PMV均匀性以及外墙内表面温度分布的影响。
Along with the development of economy and the enhancement of people's living standard, energy consumption of air-conditioning systems increases unceasingly. Though air-conditioning system has already been used very widely, more and more attention is paid to indoor thermal comfort and indoor quality it can produce and its energy consumption problems.Hybrid system of radiant cooling and displacement ventilation becomes adopted gradually in practical project and arouses wide research interest for it can provide better thermal environment more energy efficiently.
Firstly, comfort indoor indexes were summarized. CFD simulation results based on indoor zero-equation turbulence model were validated using experimental data. Then, the effect of the number of grids on simulation result was investigated. And then a steady state mathematic model of a chilled panel was established and the effect of the structural parameters on surface temperatue distribution and cooling capacity of chilled panel was analyzed. The influence of panel temperature evenness on indoor thermal environment simulation result was also discussed. It is found that it has little infulence on thermal comfort in occupied zone.
Choosing proper combined cooling parameters is an important step in designing hybrid air-conditioning systems of chilled ceiling panel and displacement ventilation. Different combination may bring about different indoor thermal comfort as well as different operational cost. A set of optimal combined cooling parameters were proposed by conducting 5 factors, 5 levels simulation experiments arranged by.orthogonal test design method. Under the optimal condition, the PMV value reaches zero with 5% PPD and ventilation efficiency obtain relatively high value. The individual influence of such cooling parameters as supply air flow rate, temperature and relative humidity of DV, the surface temperature of CP and the area ratio of CP to the ceiling on PMV value were studied by analysis range method and analysis of variance method. Results indicate that hybrid air-conditioning pattern can achieve the best indoor thermal environment in one among all simulation experiments. And the dynamic responses of room air to the change in supply air flow rate, which has the strongest influence on PMV, were simulated. It is analyzed how the air average temeperature and relative humidity in the occupied zone and non-occupied zone change along with time after the change in supply air flow rate was exerted. It reveals it will take about 20 minutes for the indoor air temperature to approach another steady value. And the air layer temperature just below the celing panel was higher than that of occupied zone. The dew point of the air layer is higher than the surface temperature of the chilled ceiling panel. It indicates that the possiblity of dew occur on the chilled ceiling panel is very less.
Finally, the boundary condition of the external wall was specified using hourly outdoor air temperature in a typical day of Xian and using thermal properties of two types of wall structure normally used. When the optimal combination of supply air temperature, flowrate and surface temperature of the chilled panel was adopted, the best area ratio of the chilled ceiling panel to that of the ceiling was selected through simulations. The best values of the hourly area ratio of chilled panel were determined for a typical office from 8:00 A.M. to 6:00 P.M. With these cooling parameters, PMV values of the occupied zone can remain within the accepted range, -0.5 to o.5. The influence of the external wall structure and the area ratio of the chilled ceiling panel on internal surface temperature of the exterior wall and indoor PMV values were also analyzed.
本文首先分析总结复合空调的热、湿环境控制指标,在利用已有实验结果验证CFD数值仿真结果的基础上,讨论了网格划分密集程度对模拟结果的影响;然后对室内冷顶板的传热过程建立了数学模型,分析了各结构参数对冷顶板供冷能力以及表面温度均匀性的影响,进一步通过数值仿真结果显示了顶板表面温度分布均匀性对室内热环境的影响。
由于供冷参数的不同组合会导致置换通风与辐射冷板复合空调室内热湿环境及系统运行费用的不同,因此本文接着利用正交法设计了5因素5水平实验方案,模拟分析了各供冷参数与热舒适性指标PMV的相关性,通过级差法和方差分析法得出了送风温度、速度及相对湿度、冷板表面温度及冷板与天花板面积比等参数对室内热舒适影响作用强弱的先后顺序和最佳组合供冷参数;然后,就对舒适性影响最显著的因素—送风速度的变化所引起的室内热环境的变化过程进行了动态模拟,分析了室内工作区和非工作区温、湿度随时间的变化规律,表明室内热湿状况再次达到稳态所需的响应时间长,但是,冷顶板表面出现结露的可能性也很小。故对置换通风-辐射供冷复合空调系统不建议采用变风量调节的方案。这一结论可为复合空调系统设计参数的确定以及运行调节方案的制定提供指导。
最后在最佳组合工况的基础上,以西安地区的室外气象条件以及两种常用墙体的结构和物理特性为准,通过调节辐射冷顶板的供冷面积对办公室从上午8:00到下午18:00的室内环境进行了模拟,得出了不同时刻的优化控制方案。分析了不同外墙结构类型和辐射冷顶板开启模式对室内PMV均匀性以及外墙内表面温度分布的影响。
Along with the development of economy and the enhancement of people's living standard, energy consumption of air-conditioning systems increases unceasingly. Though air-conditioning system has already been used very widely, more and more attention is paid to indoor thermal comfort and indoor quality it can produce and its energy consumption problems.Hybrid system of radiant cooling and displacement ventilation becomes adopted gradually in practical project and arouses wide research interest for it can provide better thermal environment more energy efficiently.
Firstly, comfort indoor indexes were summarized. CFD simulation results based on indoor zero-equation turbulence model were validated using experimental data. Then, the effect of the number of grids on simulation result was investigated. And then a steady state mathematic model of a chilled panel was established and the effect of the structural parameters on surface temperatue distribution and cooling capacity of chilled panel was analyzed. The influence of panel temperature evenness on indoor thermal environment simulation result was also discussed. It is found that it has little infulence on thermal comfort in occupied zone.
Choosing proper combined cooling parameters is an important step in designing hybrid air-conditioning systems of chilled ceiling panel and displacement ventilation. Different combination may bring about different indoor thermal comfort as well as different operational cost. A set of optimal combined cooling parameters were proposed by conducting 5 factors, 5 levels simulation experiments arranged by.orthogonal test design method. Under the optimal condition, the PMV value reaches zero with 5% PPD and ventilation efficiency obtain relatively high value. The individual influence of such cooling parameters as supply air flow rate, temperature and relative humidity of DV, the surface temperature of CP and the area ratio of CP to the ceiling on PMV value were studied by analysis range method and analysis of variance method. Results indicate that hybrid air-conditioning pattern can achieve the best indoor thermal environment in one among all simulation experiments. And the dynamic responses of room air to the change in supply air flow rate, which has the strongest influence on PMV, were simulated. It is analyzed how the air average temeperature and relative humidity in the occupied zone and non-occupied zone change along with time after the change in supply air flow rate was exerted. It reveals it will take about 20 minutes for the indoor air temperature to approach another steady value. And the air layer temperature just below the celing panel was higher than that of occupied zone. The dew point of the air layer is higher than the surface temperature of the chilled ceiling panel. It indicates that the possiblity of dew occur on the chilled ceiling panel is very less.
Finally, the boundary condition of the external wall was specified using hourly outdoor air temperature in a typical day of Xian and using thermal properties of two types of wall structure normally used. When the optimal combination of supply air temperature, flowrate and surface temperature of the chilled panel was adopted, the best area ratio of the chilled ceiling panel to that of the ceiling was selected through simulations. The best values of the hourly area ratio of chilled panel were determined for a typical office from 8:00 A.M. to 6:00 P.M. With these cooling parameters, PMV values of the occupied zone can remain within the accepted range, -0.5 to o.5. The influence of the external wall structure and the area ratio of the chilled ceiling panel on internal surface temperature of the exterior wall and indoor PMV values were also analyzed.
引文
[1]Brodrick James.Energy Consumption Characteristics of Commercial Building HVAC Systems Volume Ⅲ:Energy Savings Potential.New York:Department of Energy,2002:19-155.
[2]Brunk M F.Cooling Ceiling-An Opportunity to Reduce Energy Costs by Way of Radiant Cooling.ASHRAE Transactions,1993,VOL102.
[3]Prapapong Vangtook.An experimental investigation of application of radiant cooling I n hot humid climate.Energy and Buildings,2006,38:273-285.
[4]J.Niu.Energy saving possibilities with cooled-ceiling systems.Energy and Buildings,1995,23:147-158.
[5]Jae-Weon Jeong.Simplified cooling capacity estimation modelfor top insulated metal ceiling radiant cooling panels.Applied Thermal Engineering,2004,24:2055-2072.
[6]Koichi Kitagawa,Noriko Komoda,etc.Effect of Humidity and Small Air Movement on Thermal Comfort under a Radiant Cooling Ceiling by Subjective Experiment.Energy and Buildings,1999,30:185-193.
[7]XiaXiong,QingYanChen,Leon R Glickman.A critical renew of displaeement Ventilation.ASHRAE Traps,1998.
[8]Ashrae guideline.displacement ventilation design guideline.1999.
[9]Kim Taeycon,Kato Shinsuke.Murakami Suzo.Indoorcooling/ heating load analysis based on coupled simulation of convection.radiation and HVAC control [J].Building and Environment,2001,36(7):901-908.
[10]H.Xing,etc.A Study of the Air Quality in the Breathing Zone in a Room with Displacement Ventilation.Building and Environment,2001,36.809-820.
[11]S.G.Hodder.Thermal comfort in chilled ceiling and displacement ventilation environments:vertical radiant temperature asymmetry effects.Energy and Buildings,1998,27:167-173.
[12]Doosam Song,Dr.Eng,etc.Study on Cross-ventilation with Radiation--al Panel Cooling for Hot and Humid Regions.ASHRAE Transactions,2002:1281-1276.
[13]D.L.Loveday.Displacement ventilation environments with chilled ceilings:thermal comfort design within the context of the BS EN ISO7730 versus adaptive debate.Energy and Buildings,2002,34:573-579.
[14]彭鹏.冷却项板的测试标准及相应的实验研究.建筑热能通风空调, 2004,23(2):87-91.
[15]孙丽颖,马最良.冷却吊顶供水方式对系统运行能耗的影响.暖通空调,2003,31(1):107-109.
[16]马仁民.论下部通风空调节能及其适用条件.暖通空调,1983,13(3):5-9.
[17]李强民.置换通风原理设计及应用.暖通空调,2000,30(5):41-46.
[18]庄森,刘传聚.舒适、节能的冷却吊顶空调系统.能源研究与信息,1998.1(4)。
[19]那艳玲,涂光备.冷却顶板对置换通风系统的影响:CFD研究.暖通空调,2005,35(1):11-14.
[20]周鹏,李强民.置换通风与冷却顶板.暖通空调,1998,28(5):1-5.
[21]H.E.Feustel,C.Stetiu.Hydronic Radiation Cooling-Preliminary Assesment.Energy and Buildings,1995,22:193-205.
[22]Corina Stetiu.Energy and Peak Power Savings Potential of Radiant Cooling Systems in US Commercial Buildings.Energy and Buildings,1999,30:127-138
[23]Jeong Jae-Weon,Mumma SA.Ceiling radiant cooling panel capacity enhanced by mixed convection in mechanically ventilated spaces.Applied Thermal Engineering,2003,23:2293-306.
[24]Kilkis BI,Sager S,Uludag M.A simplified model for radiant heating and cooling panels.Simulation Practice and Theory,1994,2(2):61-76.
[25]Fanger,P.O.,A.K.Melikov,etc.Turbulence and draft.ASHRAE J,1989(4)
[26]王福军著.计算流体动力学分析—CFD软件原理与应用.清华大学出版社,2004.
[27]Fanger,P.O.,B.M.Ipsen,etc.Comfort Limits for Asymmeetric Thermal Radiation.Energy and Buidings,1985,8(3):225-236.
[28]Qingyan Chen,Weiran Xu.A zero-equation turbulent model for indoor airflow simulation.Energy and Buildings,1998,28(2):137-144.
[29]陶文铨著.数值传热学(第二版).西安交通大学出版社,2001.
[30]《采暖通风与空调设计规范》,GBJ19-87.
[31]Jelena Srebric,Qingyan Chen.An Example of Verifyication Validation and Reporting of Indoor Environment CFD Analyses.ASHARE Trans,2002,108(2):185-194.
[32]Qingyan Chen.Computational Fluid Dynamics for HAVC:Successes and Failures,ASHARETrans,1997,103(1):178-187.
[33]J.T.Tuomaala,Carey J.Simonson,Kalevi.Validation of Coupled Airflow and Heat Transfer Routines in a Building Simulation tool.ASHARFTrans,2002,108(1):435
[34]袁锋.顶板辐射.置换通风复合空调室内热环境研究:[硕士学位论文].西安建筑科技大学,2007.
[35]王子介.低温辐射供暖与辐射供冷.机械工业出版社,2004,6.
[36]路延魁.空气调节设计手册.中国建筑工业出版社,2004,12.
[37]《国民用建筑工程设计技术措施暖通空调·动力》.中国建筑标准设计研究院.
[38]《采暖通风与空气调节设计规范》(GB50019—2003)
[39]朱能,刘珊.置换通风与冷却项板热舒适性研究.制冷学报,2000,4:64-70.
[40]乔小壮,一种新型空调方式—“辐射板+自然通风“的初步研究:[硕士学位论文]湖南大学,2003.
[41]邓峥.置换通风/冷却吊顶系统的性能研究及应用分析:[硕士学位论文]同济大学,2005.
[42]布文峰.冷却顶板空调系统的研究应用:[硕士学位论文].北京工业大学,2001.
[43]王海英.下送风空调房间气流组织设计方法的研究:[硕士学位论文].北京工业大学,2000.
[44]张行周,王浚.置换通风与冷却顶板相结合的空调系统.流体机械,2002,30(1):54-56.
[45]郑国忠,荆有印.置换通风的研究与应用现状.节能,2005,4:16-19.
[46]王庆莉,龙惟定.地板送风与置换通风的差异.建筑热能通风空调,2004.23(5):-13.
[2]Brunk M F.Cooling Ceiling-An Opportunity to Reduce Energy Costs by Way of Radiant Cooling.ASHRAE Transactions,1993,VOL102.
[3]Prapapong Vangtook.An experimental investigation of application of radiant cooling I n hot humid climate.Energy and Buildings,2006,38:273-285.
[4]J.Niu.Energy saving possibilities with cooled-ceiling systems.Energy and Buildings,1995,23:147-158.
[5]Jae-Weon Jeong.Simplified cooling capacity estimation modelfor top insulated metal ceiling radiant cooling panels.Applied Thermal Engineering,2004,24:2055-2072.
[6]Koichi Kitagawa,Noriko Komoda,etc.Effect of Humidity and Small Air Movement on Thermal Comfort under a Radiant Cooling Ceiling by Subjective Experiment.Energy and Buildings,1999,30:185-193.
[7]XiaXiong,QingYanChen,Leon R Glickman.A critical renew of displaeement Ventilation.ASHRAE Traps,1998.
[8]Ashrae guideline.displacement ventilation design guideline.1999.
[9]Kim Taeycon,Kato Shinsuke.Murakami Suzo.Indoorcooling/ heating load analysis based on coupled simulation of convection.radiation and HVAC control [J].Building and Environment,2001,36(7):901-908.
[10]H.Xing,etc.A Study of the Air Quality in the Breathing Zone in a Room with Displacement Ventilation.Building and Environment,2001,36.809-820.
[11]S.G.Hodder.Thermal comfort in chilled ceiling and displacement ventilation environments:vertical radiant temperature asymmetry effects.Energy and Buildings,1998,27:167-173.
[12]Doosam Song,Dr.Eng,etc.Study on Cross-ventilation with Radiation--al Panel Cooling for Hot and Humid Regions.ASHRAE Transactions,2002:1281-1276.
[13]D.L.Loveday.Displacement ventilation environments with chilled ceilings:thermal comfort design within the context of the BS EN ISO7730 versus adaptive debate.Energy and Buildings,2002,34:573-579.
[14]彭鹏.冷却项板的测试标准及相应的实验研究.建筑热能通风空调, 2004,23(2):87-91.
[15]孙丽颖,马最良.冷却吊顶供水方式对系统运行能耗的影响.暖通空调,2003,31(1):107-109.
[16]马仁民.论下部通风空调节能及其适用条件.暖通空调,1983,13(3):5-9.
[17]李强民.置换通风原理设计及应用.暖通空调,2000,30(5):41-46.
[18]庄森,刘传聚.舒适、节能的冷却吊顶空调系统.能源研究与信息,1998.1(4)。
[19]那艳玲,涂光备.冷却顶板对置换通风系统的影响:CFD研究.暖通空调,2005,35(1):11-14.
[20]周鹏,李强民.置换通风与冷却顶板.暖通空调,1998,28(5):1-5.
[21]H.E.Feustel,C.Stetiu.Hydronic Radiation Cooling-Preliminary Assesment.Energy and Buildings,1995,22:193-205.
[22]Corina Stetiu.Energy and Peak Power Savings Potential of Radiant Cooling Systems in US Commercial Buildings.Energy and Buildings,1999,30:127-138
[23]Jeong Jae-Weon,Mumma SA.Ceiling radiant cooling panel capacity enhanced by mixed convection in mechanically ventilated spaces.Applied Thermal Engineering,2003,23:2293-306.
[24]Kilkis BI,Sager S,Uludag M.A simplified model for radiant heating and cooling panels.Simulation Practice and Theory,1994,2(2):61-76.
[25]Fanger,P.O.,A.K.Melikov,etc.Turbulence and draft.ASHRAE J,1989(4)
[26]王福军著.计算流体动力学分析—CFD软件原理与应用.清华大学出版社,2004.
[27]Fanger,P.O.,B.M.Ipsen,etc.Comfort Limits for Asymmeetric Thermal Radiation.Energy and Buidings,1985,8(3):225-236.
[28]Qingyan Chen,Weiran Xu.A zero-equation turbulent model for indoor airflow simulation.Energy and Buildings,1998,28(2):137-144.
[29]陶文铨著.数值传热学(第二版).西安交通大学出版社,2001.
[30]《采暖通风与空调设计规范》,GBJ19-87.
[31]Jelena Srebric,Qingyan Chen.An Example of Verifyication Validation and Reporting of Indoor Environment CFD Analyses.ASHARE Trans,2002,108(2):185-194.
[32]Qingyan Chen.Computational Fluid Dynamics for HAVC:Successes and Failures,ASHARETrans,1997,103(1):178-187.
[33]J.T.Tuomaala,Carey J.Simonson,Kalevi.Validation of Coupled Airflow and Heat Transfer Routines in a Building Simulation tool.ASHARFTrans,2002,108(1):435
[34]袁锋.顶板辐射.置换通风复合空调室内热环境研究:[硕士学位论文].西安建筑科技大学,2007.
[35]王子介.低温辐射供暖与辐射供冷.机械工业出版社,2004,6.
[36]路延魁.空气调节设计手册.中国建筑工业出版社,2004,12.
[37]《国民用建筑工程设计技术措施暖通空调·动力》.中国建筑标准设计研究院.
[38]《采暖通风与空气调节设计规范》(GB50019—2003)
[39]朱能,刘珊.置换通风与冷却项板热舒适性研究.制冷学报,2000,4:64-70.
[40]乔小壮,一种新型空调方式—“辐射板+自然通风“的初步研究:[硕士学位论文]湖南大学,2003.
[41]邓峥.置换通风/冷却吊顶系统的性能研究及应用分析:[硕士学位论文]同济大学,2005.
[42]布文峰.冷却顶板空调系统的研究应用:[硕士学位论文].北京工业大学,2001.
[43]王海英.下送风空调房间气流组织设计方法的研究:[硕士学位论文].北京工业大学,2000.
[44]张行周,王浚.置换通风与冷却顶板相结合的空调系统.流体机械,2002,30(1):54-56.
[45]郑国忠,荆有印.置换通风的研究与应用现状.节能,2005,4:16-19.
[46]王庆莉,龙惟定.地板送风与置换通风的差异.建筑热能通风空调,2004.23(5):-13.