制冷装置液体冷媒融霜系统的研究
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摘要
随着制冷、空调技术的发展,低温空调、低温低湿恒温恒湿装置应用逐步广泛,蒸发器结霜造成的恒温恒湿装置降温和除湿功能恶化以及除霜时的室内温、湿度波动成为低温低湿恒温恒湿系统一个亟待解决的问题。本文在前届研究生工作基础上对新型融霜方式-液体冷媒除霜进行了进一步理论计算和实验研究。
本文建立了蒸发器管内融霜模型,利用Visual Basic语言编写了计算程序,对不同融霜介质入口参数对管内融霜过程的影响进行理论计算,重点分析了液体冷媒融霜过程中,融霜介质入口温度和霜层初始厚度对融霜所需时间、能量消耗的影响,并同热气融霜过程进行了比较,发现由于热气融霜过程中的管内冷凝换热系数远大于单相流体的换热系数,在相同的霜层厚度和输入融霜介质温度相同的条件下,液体冷媒融霜的速度不如热气融霜快,但在不追求融霜速度的要求下,其优点是明显的。融霜介质的入口状态和温度、流量等一样,是影响融霜过程的重要因素。
搭建了低温低湿恒定系统实验台,以此为切入点对液体冷媒除霜进行了实验研究并验证了所建立模型的正确性。以空气侧压差为制冷和融霜的切换依据,实验结果证明,采用液体冷媒除霜系统,在运行周期内满足设计要求,并且融霜结束后换热器整体温度较低,同热气融霜相比,对换热器的破坏性影响较小。由于系统中的加热装置散热较慢,存在加热延迟和停止加热滞后的原因,因此被控室温度和相对湿度存在上下波动式逼近控制要求的现象,如对此进行改进,可提高系统的控制精度。
The depravation of cooling and dehumidification of constant temperature and humidity air-condition because of frosting of evaporator and the fluctuation of temperature and humidity when the evaporation defrosts are key problems as the wide use of low temperature air-condition and low temperature and humidity constant system. in this paper, one new method of defrosting hot liquid defrosting has been researched both in theory and experiment.
The inside defrosting model of evaporator was built, and the influence to defrosting process of different parameters of input defrosting medium has been studied by calculation with a Visual Basic computer program. The effect on time and consumed energy in defrosting process of input refrigerant temperature and initial frost thickness on the evaporator has been investigated, and the results display that although the defrosting rate of hot gas defrosting is more fast than hot liquid for the coefficient of heat transfer is far greater in two-phase flow than in single-phase flow, the advantage of hot liquid defrosting is obvious, So the phase of input defrosting mediums is important to the defrosting process as well as the temperature and flux.
The differential pressure of evaporator is taken as the judgment of switch in the hot liquid defrosting experiment. It has been proved by the practice that the model built is valid, then the result from it is right. In the whole operation period both of cooling and defrosting process the fluctuate of temperature and humidity in the room would meet the requirement well, and the destructive effect to evaporator is small than with hot gas. Because the rejection of heat of the heating rod before air outlet is too little, the temperature and humidity in the control house fluctuate near by the requirement, If this can be improved , the precision of the system will better.
本文建立了蒸发器管内融霜模型,利用Visual Basic语言编写了计算程序,对不同融霜介质入口参数对管内融霜过程的影响进行理论计算,重点分析了液体冷媒融霜过程中,融霜介质入口温度和霜层初始厚度对融霜所需时间、能量消耗的影响,并同热气融霜过程进行了比较,发现由于热气融霜过程中的管内冷凝换热系数远大于单相流体的换热系数,在相同的霜层厚度和输入融霜介质温度相同的条件下,液体冷媒融霜的速度不如热气融霜快,但在不追求融霜速度的要求下,其优点是明显的。融霜介质的入口状态和温度、流量等一样,是影响融霜过程的重要因素。
搭建了低温低湿恒定系统实验台,以此为切入点对液体冷媒除霜进行了实验研究并验证了所建立模型的正确性。以空气侧压差为制冷和融霜的切换依据,实验结果证明,采用液体冷媒除霜系统,在运行周期内满足设计要求,并且融霜结束后换热器整体温度较低,同热气融霜相比,对换热器的破坏性影响较小。由于系统中的加热装置散热较慢,存在加热延迟和停止加热滞后的原因,因此被控室温度和相对湿度存在上下波动式逼近控制要求的现象,如对此进行改进,可提高系统的控制精度。
The depravation of cooling and dehumidification of constant temperature and humidity air-condition because of frosting of evaporator and the fluctuation of temperature and humidity when the evaporation defrosts are key problems as the wide use of low temperature air-condition and low temperature and humidity constant system. in this paper, one new method of defrosting hot liquid defrosting has been researched both in theory and experiment.
The inside defrosting model of evaporator was built, and the influence to defrosting process of different parameters of input defrosting medium has been studied by calculation with a Visual Basic computer program. The effect on time and consumed energy in defrosting process of input refrigerant temperature and initial frost thickness on the evaporator has been investigated, and the results display that although the defrosting rate of hot gas defrosting is more fast than hot liquid for the coefficient of heat transfer is far greater in two-phase flow than in single-phase flow, the advantage of hot liquid defrosting is obvious, So the phase of input defrosting mediums is important to the defrosting process as well as the temperature and flux.
The differential pressure of evaporator is taken as the judgment of switch in the hot liquid defrosting experiment. It has been proved by the practice that the model built is valid, then the result from it is right. In the whole operation period both of cooling and defrosting process the fluctuate of temperature and humidity in the room would meet the requirement well, and the destructive effect to evaporator is small than with hot gas. Because the rejection of heat of the heating rod before air outlet is too little, the temperature and humidity in the control house fluctuate near by the requirement, If this can be improved , the precision of the system will better.
引文
[1]. H.Wang and S.Touber. Distributed and non-steady-state modeling of an air cooler. Int.J.Refrig,Vol.14.1991.3
[2]. P.J.O’ Neill. Modeling and optimization of a finned tube evaporator. ASHRAE Trans ,Vol.95, Part Ⅰ
[3]. 吴乃诚.低温低湿空调环境设计.石油化工设计,1997
[4]. 臧润清.方筝.李景丽.恒温恒湿机在结霜工况下运行的实验研究.低温工程,2005 (3)::60～64
[5]. 赵荣义.范存养.空气调节.中国建筑工业出版社,1994
[6]. Hayashi. Study of frost formmation based on a theoretical model of the frost layer.Heat trans fer , 1997,Vol. 6 N o.3
[7]. Yonko. Sepsy.An investgation of the thermal cinductivity of frost while forming on flat horizonal plate.ASHREA Transactio,1967, Vol.73
[8]. D.L.O'neal, Aparameter study of the factors governing the rate of frost accumulation on a domestic refrigerator-freezer finned-tubee vaporator coils
[9]. Chung. Frost Fromation And Heat Transfer on a cylinder surface in humid air flow ,HPAC, Vo1. 3 0
[10]. Jones, Parker., Frost formation with varying environmental parameters.1975, Joural of heat transfer, Vol. 97
[11]. S.A.Shrif, An analytical model for hot gas defrosting of a cylindrical coil cooler,P art I— model development, ASHREA Transactions, SF-98-27-2
[12]. M.M Padki, S.A.Sherif, A simple method for modeling the frost formation phenomenon in different geometries, ASHREAT ransactions,VA-89-22-1
[13]. W.F.Stoecker, J.J.Lux,R.J.Kooy, Energy Considerations In Hot-Gas Defrosting Of Industrial Refrigeration Coils , ASHARE Trans 89 (2) ,549～573
[14]. 周兴禧.周振宇等.翅片管式蒸发器结霜问题的数值分析与试验研究.上海交通大学学报, 1998 (7): 28～31
[15]. 李红兰.热泵蒸发器结霜过程的理论研究. 低温与特气, 2003 (4) :25～27
[16]. 姚杨等.空气源热泵冷热水机组空气侧换热器结霜规律,.哈尔滨工业大学学报, 2002 (10)
[17]. Kondepudi, O’Neal D L. Performance of finned tube heat exchanger under frosting conditions. International Journal of Refrigeration 1993,16(3)
[18]. S.A.Shrif, An analytical model for hot gas defrosting of a cylindrical coil cooler, PartⅡ- model results and conclusion . ASHREA Transactions, SF-98-27-2
[19]. K.I.Krakow, L.Yan, S.Lin,Dr.lng , A model of hot-gas defrosting of evaporators –partⅠ: heat and mass transfer, ASHARE Transaction 1993.99 (2): 317～338
[20]. K.I.Krakow, L.Yan, S.Lin,Dr.lng , A model of hot-gas defrosting of evaporators -partⅡ: experimental analysis, ASHARE Transaction 1993.99 (2): 317～338
[21]. N.Hoffenbecker,S.A.Klein. hot gas defrost development and validation, international journal of refrigeration ,2005,605～615
[22]. 黄虎.风冷热泵热水机组动态特性与结霜除霜过程的研究:[西安交通大学博士学位论文].西安;西安交通大学
[23]. 黄虎.束鹏程.李志浩.风冷热泵冷热水机组结霜工况下运行恶性的实验研究. 流体机械,1998,26 (12): 43～47
[24]. 黄虎.李志浩.束鹏程.提高风冷热泵冷热水机组结霜工况下性能的途径.建筑热能通风空调,2000,No1: 38～40
[25]. 史剑春.两种不同节流系统对融霜的影响.流体机械,1994,Vol.22,No.7,107～112
[26]. 石文星.李先庭.房间空调器热气旁通法除霜分析及实验研究.制冷学报,2000.2
[27]. 陈汝东.制冷装置除霜方法的研究.流体机械,2004.7
[28]. 赵育川.关于风冷机热器除霜节能的探讨.冷冻与制冰
[29]. 李宝华.宋海英.浅谈热气除霜的节能.大化科技, 1999(2):39～40
[30]. 郑祖义.热泵空调系统的设计与创新,华中理工大学出版社
[31]. 周立.风冷热泵机组温度使用范围力除霜技术.暖通空调,1995.58(5)
[32]. 姜益强.姚杨.马最良.空气源热泵结霜除霜损失系数的计算.暖通空调,2000.30(5)
[33]. 王剑锋.陈光明.空气热源热泵冬季结霜特性研究.制冷,1997,(1)
[34]. 张术学.钱江璐.空气冷却器融霜方式的改进措施.制冷与空调,2003,(8)
[35]. 何志龙.黄东.袁秀玲.衡量结霜时间的指标—湿温比.流体机械,2000,(7):55~57
[36]. 王文涛.姜锦英.结霜传感器.研究动态,2001,(10):19~21
[37]. 郑钢.谷波.王志毅.对化霜控制问题的探讨.制冷与空调,2002,(6):15~19
[38]. 符建坤.欧阳海生.刘凤珍.高湿地区风冷热泵蒸发器除霜控制研究.流体机械,2003, (10):44~47
[39]. 陈汝东.许东晟.空气热源热泵空调器最佳除霜点的控制.空调暖通技术,1996(4) :7～9
[40]. 陈汝东.许东晟.风冷热泵空调器除霜控制的研究.流体机械,1999,(2) :55～57
[41]. 黄虎.李志浩.束鹏程等.风冷热泵冷热水机组自调整模糊除霜控制研究.暖通空调,2001, (3):67~69
[42]. 王铁军.刘向农.风源热泵模糊自修正除霜技术应用研究. 制冷学报,2005(1) 29-32
[43]. 吴业正.制冷原理与设备.西安:西安交通大学出版社,1998
[44]. 查世彤.换热器表面结霜机理分析. 天津商学院学报, 1997 (4 )
[45]. 郝英立.初始成长阶段霜层特性实验研究.东南大学学报,2005(1),154～158
[46]. 丁国良.张春路.制冷空调装置方针与优化.北京:科学出版社,2001
[47]. 刘志强.汤广发.赵福云.风冷热泵除霜过程动态特性模拟和实验研究.制冷学报,2003,(3)
[48]. 徐尔贵.丁雷.Visual Basic 教程.北京:清华大学出版社,2003
[49]. 赵辉.结霜工况下恒温恒湿系统性能研究:[硕士学位论文]天津:天津商学院,2002
[2]. P.J.O’ Neill. Modeling and optimization of a finned tube evaporator. ASHRAE Trans ,Vol.95, Part Ⅰ
[3]. 吴乃诚.低温低湿空调环境设计.石油化工设计,1997
[4]. 臧润清.方筝.李景丽.恒温恒湿机在结霜工况下运行的实验研究.低温工程,2005 (3)::60～64
[5]. 赵荣义.范存养.空气调节.中国建筑工业出版社,1994
[6]. Hayashi. Study of frost formmation based on a theoretical model of the frost layer.Heat trans fer , 1997,Vol. 6 N o.3
[7]. Yonko. Sepsy.An investgation of the thermal cinductivity of frost while forming on flat horizonal plate.ASHREA Transactio,1967, Vol.73
[8]. D.L.O'neal, Aparameter study of the factors governing the rate of frost accumulation on a domestic refrigerator-freezer finned-tubee vaporator coils
[9]. Chung. Frost Fromation And Heat Transfer on a cylinder surface in humid air flow ,HPAC, Vo1. 3 0
[10]. Jones, Parker., Frost formation with varying environmental parameters.1975, Joural of heat transfer, Vol. 97
[11]. S.A.Shrif, An analytical model for hot gas defrosting of a cylindrical coil cooler,P art I— model development, ASHREA Transactions, SF-98-27-2
[12]. M.M Padki, S.A.Sherif, A simple method for modeling the frost formation phenomenon in different geometries, ASHREAT ransactions,VA-89-22-1
[13]. W.F.Stoecker, J.J.Lux,R.J.Kooy, Energy Considerations In Hot-Gas Defrosting Of Industrial Refrigeration Coils , ASHARE Trans 89 (2) ,549～573
[14]. 周兴禧.周振宇等.翅片管式蒸发器结霜问题的数值分析与试验研究.上海交通大学学报, 1998 (7): 28～31
[15]. 李红兰.热泵蒸发器结霜过程的理论研究. 低温与特气, 2003 (4) :25～27
[16]. 姚杨等.空气源热泵冷热水机组空气侧换热器结霜规律,.哈尔滨工业大学学报, 2002 (10)
[17]. Kondepudi, O’Neal D L. Performance of finned tube heat exchanger under frosting conditions. International Journal of Refrigeration 1993,16(3)
[18]. S.A.Shrif, An analytical model for hot gas defrosting of a cylindrical coil cooler, PartⅡ- model results and conclusion . ASHREA Transactions, SF-98-27-2
[19]. K.I.Krakow, L.Yan, S.Lin,Dr.lng , A model of hot-gas defrosting of evaporators –partⅠ: heat and mass transfer, ASHARE Transaction 1993.99 (2): 317～338
[20]. K.I.Krakow, L.Yan, S.Lin,Dr.lng , A model of hot-gas defrosting of evaporators -partⅡ: experimental analysis, ASHARE Transaction 1993.99 (2): 317～338
[21]. N.Hoffenbecker,S.A.Klein. hot gas defrost development and validation, international journal of refrigeration ,2005,605～615
[22]. 黄虎.风冷热泵热水机组动态特性与结霜除霜过程的研究:[西安交通大学博士学位论文].西安;西安交通大学
[23]. 黄虎.束鹏程.李志浩.风冷热泵冷热水机组结霜工况下运行恶性的实验研究. 流体机械,1998,26 (12): 43～47
[24]. 黄虎.李志浩.束鹏程.提高风冷热泵冷热水机组结霜工况下性能的途径.建筑热能通风空调,2000,No1: 38～40
[25]. 史剑春.两种不同节流系统对融霜的影响.流体机械,1994,Vol.22,No.7,107～112
[26]. 石文星.李先庭.房间空调器热气旁通法除霜分析及实验研究.制冷学报,2000.2
[27]. 陈汝东.制冷装置除霜方法的研究.流体机械,2004.7
[28]. 赵育川.关于风冷机热器除霜节能的探讨.冷冻与制冰
[29]. 李宝华.宋海英.浅谈热气除霜的节能.大化科技, 1999(2):39～40
[30]. 郑祖义.热泵空调系统的设计与创新,华中理工大学出版社
[31]. 周立.风冷热泵机组温度使用范围力除霜技术.暖通空调,1995.58(5)
[32]. 姜益强.姚杨.马最良.空气源热泵结霜除霜损失系数的计算.暖通空调,2000.30(5)
[33]. 王剑锋.陈光明.空气热源热泵冬季结霜特性研究.制冷,1997,(1)
[34]. 张术学.钱江璐.空气冷却器融霜方式的改进措施.制冷与空调,2003,(8)
[35]. 何志龙.黄东.袁秀玲.衡量结霜时间的指标—湿温比.流体机械,2000,(7):55~57
[36]. 王文涛.姜锦英.结霜传感器.研究动态,2001,(10):19~21
[37]. 郑钢.谷波.王志毅.对化霜控制问题的探讨.制冷与空调,2002,(6):15~19
[38]. 符建坤.欧阳海生.刘凤珍.高湿地区风冷热泵蒸发器除霜控制研究.流体机械,2003, (10):44~47
[39]. 陈汝东.许东晟.空气热源热泵空调器最佳除霜点的控制.空调暖通技术,1996(4) :7～9
[40]. 陈汝东.许东晟.风冷热泵空调器除霜控制的研究.流体机械,1999,(2) :55～57
[41]. 黄虎.李志浩.束鹏程等.风冷热泵冷热水机组自调整模糊除霜控制研究.暖通空调,2001, (3):67~69
[42]. 王铁军.刘向农.风源热泵模糊自修正除霜技术应用研究. 制冷学报,2005(1) 29-32
[43]. 吴业正.制冷原理与设备.西安:西安交通大学出版社,1998
[44]. 查世彤.换热器表面结霜机理分析. 天津商学院学报, 1997 (4 )
[45]. 郝英立.初始成长阶段霜层特性实验研究.东南大学学报,2005(1),154～158
[46]. 丁国良.张春路.制冷空调装置方针与优化.北京:科学出版社,2001
[47]. 刘志强.汤广发.赵福云.风冷热泵除霜过程动态特性模拟和实验研究.制冷学报,2003,(3)
[48]. 徐尔贵.丁雷.Visual Basic 教程.北京:清华大学出版社,2003
[49]. 赵辉.结霜工况下恒温恒湿系统性能研究:[硕士学位论文]天津:天津商学院,2002