冷库液体冷媒融霜的理论和实验研究
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摘要
冷库是发展冷藏业的基础设施,也是在低温条件下储藏货物的建筑群。随着国民经济的高速发展和人民生活水平的提高,对冷库的要求也越来越高。蒸发器结霜影响了冷库的性能,如何有效地融霜成了一个亟需解决的问题。本文针对冷库提出一种新的融霜方式——液体冷媒融霜。
针对冷库的制冷系统,分别对压缩机、冷凝器、热力膨胀阀、制冷蒸发器和融霜蒸发器五个部件建立数学模型,进而建立冷库液体冷媒融霜制冷系统的数学模型,然后用MATLAB编程求解,分析制冷系统融霜过程的性能变化规律。
设计实验方案,在原有实验装置的基础上,对实验台进行整改搭建。进行漏冷实验,拟合漏冷量关于室内外温差的三次幂多项式,以便计算不同室内外温差的漏冷量。通过实验确定液体冷媒融霜的时间为15分钟。
本文对不同工况下液体冷媒融霜对冷库性能影响进行了实验研究。实验结果表明:(1)冷库液体冷媒融霜过程中,库温波动约5℃;(2)液体冷媒融霜能达到很大的过冷度,在整个融霜过程中,融霜蒸发器充当了过冷器的作用,有利于制冷系统制冷量的提高。(3)液体冷媒融霜过程中蒸发器盘管表面温度最高不超过30℃,与热气融霜相比,对换热器翅片效率影响小。
本实验模拟的冷库条件与实际的冷库条件差距较大,因此,实验结果存在着一定的偏差;另外,由于系统采用手动切换,导致切换时间不够准确,不能达到工程上的要求,如何对其自控系统进行改造成为今后要解决的问题。
Cold frame is the basic establishment for developing cold-storage industry.It is also the building for storing goods under low temperature.With the rapid development of national economy and advance of people's standard of living,the require of cold frame is at a high pitch. Evaporator frosting can affect the capability of cold frame.How to defrost effectively is a serious problem.A new defrosting method,hot liquid defrosting,is introduced in this paper.
The refrigeration system has five main parts:compressor,condenser,expanding valve, refrigeration evaporator and defrosting evaporator.Their mathematic models are established respectively.Moreover,the mathematic model of hot liquid defrosting refrigeration system is established.It can be computed with MATLAB programme and the rule of capability variety of refrigeration system during defrosting is analysed.
The experiment plan is designed and the experiment set is rectified on the basis of former one.Experiment of cold leaking is carried out to fit a thrice power multinomial about temperature difference with leaking cold.The multinomial can be used to compute different leaking cold with different temperature difference.The time of defrosting which is ascertained by experiment is 15 minutes.
The research on hot liquid defrosting affecting the capability of cold frame is carried out under different work condition.The results are as follows:1.The temperature difference is about 5℃during hot liquid defrosting.2.Hot liquid defrosting can get large degrees of supercooling.It avails to enhance the refrigeration capacity during the process of defrosting.3.The temperature of evaporator is always below 30℃during the process of defrosting.Compared with hot gas defrosting,it is less effect on efficiency of fin of heat-exchanger.
The experimental result has some deviation because of the differences between stimulant cold frame condition and actual cold frame.Otherwise,the system switches manually.Switching time can't accord with the demand of engineering.How to improve auto-control system should be settled in the future.
针对冷库的制冷系统,分别对压缩机、冷凝器、热力膨胀阀、制冷蒸发器和融霜蒸发器五个部件建立数学模型,进而建立冷库液体冷媒融霜制冷系统的数学模型,然后用MATLAB编程求解,分析制冷系统融霜过程的性能变化规律。
设计实验方案,在原有实验装置的基础上,对实验台进行整改搭建。进行漏冷实验,拟合漏冷量关于室内外温差的三次幂多项式,以便计算不同室内外温差的漏冷量。通过实验确定液体冷媒融霜的时间为15分钟。
本文对不同工况下液体冷媒融霜对冷库性能影响进行了实验研究。实验结果表明:(1)冷库液体冷媒融霜过程中,库温波动约5℃;(2)液体冷媒融霜能达到很大的过冷度,在整个融霜过程中,融霜蒸发器充当了过冷器的作用,有利于制冷系统制冷量的提高。(3)液体冷媒融霜过程中蒸发器盘管表面温度最高不超过30℃,与热气融霜相比,对换热器翅片效率影响小。
本实验模拟的冷库条件与实际的冷库条件差距较大,因此,实验结果存在着一定的偏差;另外,由于系统采用手动切换,导致切换时间不够准确,不能达到工程上的要求,如何对其自控系统进行改造成为今后要解决的问题。
Cold frame is the basic establishment for developing cold-storage industry.It is also the building for storing goods under low temperature.With the rapid development of national economy and advance of people's standard of living,the require of cold frame is at a high pitch. Evaporator frosting can affect the capability of cold frame.How to defrost effectively is a serious problem.A new defrosting method,hot liquid defrosting,is introduced in this paper.
The refrigeration system has five main parts:compressor,condenser,expanding valve, refrigeration evaporator and defrosting evaporator.Their mathematic models are established respectively.Moreover,the mathematic model of hot liquid defrosting refrigeration system is established.It can be computed with MATLAB programme and the rule of capability variety of refrigeration system during defrosting is analysed.
The experiment plan is designed and the experiment set is rectified on the basis of former one.Experiment of cold leaking is carried out to fit a thrice power multinomial about temperature difference with leaking cold.The multinomial can be used to compute different leaking cold with different temperature difference.The time of defrosting which is ascertained by experiment is 15 minutes.
The research on hot liquid defrosting affecting the capability of cold frame is carried out under different work condition.The results are as follows:1.The temperature difference is about 5℃during hot liquid defrosting.2.Hot liquid defrosting can get large degrees of supercooling.It avails to enhance the refrigeration capacity during the process of defrosting.3.The temperature of evaporator is always below 30℃during the process of defrosting.Compared with hot gas defrosting,it is less effect on efficiency of fin of heat-exchanger.
The experimental result has some deviation because of the differences between stimulant cold frame condition and actual cold frame.Otherwise,the system switches manually.Switching time can't accord with the demand of engineering.How to improve auto-control system should be settled in the future.
引文
[1]康三江.浅议国内外冷库行业发展现状和趋势[J].保鲜与加工,2006,34(3):1-3.
[2]鲁默森,张静,王淑贞,等.现代化低成本果蔬冷库的建造和使用[J].落叶果树,2001(3):29-31.
[3]林峰.冷库集中式、分散式两种供冷方式的分析和比较[J].中国水产,2000(3):46-48.
[4]F.R.Amen.Study of frosting of heat pump evaporators[J].ASHRAE Transactions,1993,99(1):61-71.
[5]Kondepudi,D.L.O'Neal.Performance of finned tube heat exchanger under frosting conditions[J].International Journal of Refrigeration,1993,16(3):175-180.
[6]W.F.Stoecker.How frost formation on coils affects refrigeration systems[J].Refrigeration Engineer,1957:65.
[7]W.F.Stoecker.Frost formation on refrigeration coils[J].ASHRAE Transactions,1960:66.
[8]Hayashi.Study of frost formation based on a theoretical model of the frost layer[J].Heat Transfer,1997,6(3):68-76.
[9]Yonko,Sepsy.An investigation of the thermal conductivity of frost while forming on flat horizontal plate[J].ASHREA Transactions,1967,73
[10]D.L.O'neal.A parameter study of the factors governing the rate of frost accumulation on a domestic refrigerator-freezer finned-tube evaporator coils[J].International Journal of Refrigeration,1985,6:136-140.
[11]Chung.Frost formation and heat transfer on a cylinder surface in humid air flow[J].HPAC,1996,7.
[12]B.W.Jones,J.D.Parker.Frost formation with varying environmental parameters[J].Journal of Heat Transfer,1975,97:203-208.
[13]S.A.Shrif.An analytical model for hot gas defrosting of a cylindrical coil cooler,PartⅠ-model development[J].ASHREA Transactions,1998,27(2).
[14]M.M Padki,S.A.Sherif.A simple method for modeling the frost formation phenomenon in different geometries[J].ASHREAT ransactions,1989,22(1).
[15]周兴禧,周振宇.翅片管式蒸发器结霜问题的数值分析与试验研究[J].上海交通大学学报,1998,(7):28-31.
[16]李红兰.热泵蒸发器结霜过程的理论研究[J].低温与特气,2003(1):25-27.
[17]姚杨,姜益强,马最良.翅片管换热器结霜时霜密度和厚度的变化[J].工程热物理学报,2003,24(6):1039-1041.
[18]姚杨,姜益强,马最良,等.空气侧换热器结霜时传热和阻力特性研究[J].热能动力工程,2003,18(3):297-300.
[19]W.F.Stoecker,J.J.Lux,R.J.Kooy.Energy considerations in hot-gas defrosting of industrial refrigeration coils[J].ASHARE Transactions,1989(2):549-573.
[20]W.A.Miller.Laboratory examination and seasonal analysis of frosting and defrosting for an air-to-air heat pump[J].ASHARE Transactions,1987,93(1):1474-1489.
[21]S.A.Shrif.An analytical model for hot gas defrosting of a cylindrical coil cooler,PartⅡ-model results and conclusion[J].ASHREA Transactions,1998,27(2).
[22]K.I.Krakow,L.Yan,S.Lin,et al.A model of hot-gas defrosting of evaporators,Part Ⅰ:heat and mass transfer[J].ASHARE Transactions,1993,99(2):317-338.
[23]K.I.Krakow,L.Yan,S.Lin,et al.A model of hot-gas defrosting of evaporators,Part Ⅱ:experimental analysis[J].ASHARE Transactions,1993,99(2):317-338.
[24]N.Hoffenbecker,S.A.Klein.Hot gas defrost development and validation[J].International Journal of Refrigeration,2005:605-615.
[25]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,1999.
[26]黄虎,束鹏程,李志浩.风冷热泵冷热水机组结霜工况下运行特性的实验研究[J].流体机械,1998,26(12):43-47.
[27]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[J].建筑热能通风空调,2000,(1):38-40.
[28]史剑春.两种不同节流系统对融霜的影响[J].流体机械,1994,22(7):107-112.
[29]石文星,李先庭,邵双全.房间空调器热气旁通法除霜分析及实验研究[J].制冷学报,2000,(2):29-35.
[30]陈汝东,许东晟.制冷装置除霜方法的研究[J].同济大学学报,1998,26(5):566-569.
[31]庄友明.食品冷库除霜方法及其能耗分析[J].集美大学学报(自然科学版),2006,11(1):62-65.
[32]臧润清,方筝,李景丽,等.恒温恒湿机在结霜工况下运行的实验研究[J].低温工程, 2005,(3):60-64.
[33]连添达,臧润清.制冷装置设计[M].北京:中国经济出版社,1995.
[34]刘清江.冷库空气冷却器融霜节能的研究[J].制冷,2005,24(4):12-15.
[35]阚杰,郝亮,李涛,等.间接制冷系统中除霜、能耗及温室效应的比较[J].制冷与空调,2005,5(3):53-56.
[36]李宝华,宋海英.浅谈热气除霜的节能[J].大化科技,1999,(2):39-40.
[37]何志龙,黄东,袁秀玲.衡量结霜时间的指标—湿温比[J].流体机械,2000,(7):55-57.
[38]王文涛,姜锦英.结霜传感器[J].研究动态,2001,(10):19-21.
[39]郑钢,谷波,王志毅.对化霜控制问题的探讨[J].制冷与空调,2002,(6):15-19.
[40]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[J].流体机械,2003,(10):44-47.
[41]陈汝东,许东晟.空气热源热泵空调器最佳除霜点的控制[J].空调暖通技术,1996,(4):7-9.
[42]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[J].暖通空调,2001,(3):67-69.
[43]王铁军,刘向农.风源热泵模糊自修正除霜技术应用研究[J].制冷学报,2005,(1):29-32.
[44]吴业正,韩宝琦.制冷原理及设备[M].西安:西安交通大学出版社,2003.
[45]DR.A.E.Dahiri.A compressor simulation model with corrections for the level of suction gas superheat[J].ASHRAE Transactions,1981,87:771-782.
[46]K.A.Manske,D.T.Reindl,S.A.Klein.Evaporative condenser control in industrial refrigeration systems[J].International Journal of Refrigeration,2001,24:676-691.
[47]B.B.雅柯勃松.小型制冷机[M].北京:机械工业出版社,1982.
[48]F.C.Mcquiston.Finned tube heat exchangers:state of the art for the air side[J].ASHRAE Transactions,1981,87:1077-1085.
[49]杨世铭.传热学[M].北京:高等教育出版社,1995.
[50]J.P.Holman.Heat transfer[M].New York:McGraw-Hill Book Company,1986.
[51]彦启森.空气调节用制冷技术[M].北京:中国建筑工业出版社,第二版,1985.
[52]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]鲁默森,张静,王淑贞,等.现代化低成本果蔬冷库的建造和使用[J].落叶果树,2001(3):29-31.
[3]林峰.冷库集中式、分散式两种供冷方式的分析和比较[J].中国水产,2000(3):46-48.
[4]F.R.Amen.Study of frosting of heat pump evaporators[J].ASHRAE Transactions,1993,99(1):61-71.
[5]Kondepudi,D.L.O'Neal.Performance of finned tube heat exchanger under frosting conditions[J].International Journal of Refrigeration,1993,16(3):175-180.
[6]W.F.Stoecker.How frost formation on coils affects refrigeration systems[J].Refrigeration Engineer,1957:65.
[7]W.F.Stoecker.Frost formation on refrigeration coils[J].ASHRAE Transactions,1960:66.
[8]Hayashi.Study of frost formation based on a theoretical model of the frost layer[J].Heat Transfer,1997,6(3):68-76.
[9]Yonko,Sepsy.An investigation of the thermal conductivity of frost while forming on flat horizontal plate[J].ASHREA Transactions,1967,73
[10]D.L.O'neal.A parameter study of the factors governing the rate of frost accumulation on a domestic refrigerator-freezer finned-tube evaporator coils[J].International Journal of Refrigeration,1985,6:136-140.
[11]Chung.Frost formation and heat transfer on a cylinder surface in humid air flow[J].HPAC,1996,7.
[12]B.W.Jones,J.D.Parker.Frost formation with varying environmental parameters[J].Journal of Heat Transfer,1975,97:203-208.
[13]S.A.Shrif.An analytical model for hot gas defrosting of a cylindrical coil cooler,PartⅠ-model development[J].ASHREA Transactions,1998,27(2).
[14]M.M Padki,S.A.Sherif.A simple method for modeling the frost formation phenomenon in different geometries[J].ASHREAT ransactions,1989,22(1).
[15]周兴禧,周振宇.翅片管式蒸发器结霜问题的数值分析与试验研究[J].上海交通大学学报,1998,(7):28-31.
[16]李红兰.热泵蒸发器结霜过程的理论研究[J].低温与特气,2003(1):25-27.
[17]姚杨,姜益强,马最良.翅片管换热器结霜时霜密度和厚度的变化[J].工程热物理学报,2003,24(6):1039-1041.
[18]姚杨,姜益强,马最良,等.空气侧换热器结霜时传热和阻力特性研究[J].热能动力工程,2003,18(3):297-300.
[19]W.F.Stoecker,J.J.Lux,R.J.Kooy.Energy considerations in hot-gas defrosting of industrial refrigeration coils[J].ASHARE Transactions,1989(2):549-573.
[20]W.A.Miller.Laboratory examination and seasonal analysis of frosting and defrosting for an air-to-air heat pump[J].ASHARE Transactions,1987,93(1):1474-1489.
[21]S.A.Shrif.An analytical model for hot gas defrosting of a cylindrical coil cooler,PartⅡ-model results and conclusion[J].ASHREA Transactions,1998,27(2).
[22]K.I.Krakow,L.Yan,S.Lin,et al.A model of hot-gas defrosting of evaporators,Part Ⅰ:heat and mass transfer[J].ASHARE Transactions,1993,99(2):317-338.
[23]K.I.Krakow,L.Yan,S.Lin,et al.A model of hot-gas defrosting of evaporators,Part Ⅱ:experimental analysis[J].ASHARE Transactions,1993,99(2):317-338.
[24]N.Hoffenbecker,S.A.Klein.Hot gas defrost development and validation[J].International Journal of Refrigeration,2005:605-615.
[25]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,1999.
[26]黄虎,束鹏程,李志浩.风冷热泵冷热水机组结霜工况下运行特性的实验研究[J].流体机械,1998,26(12):43-47.
[27]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[J].建筑热能通风空调,2000,(1):38-40.
[28]史剑春.两种不同节流系统对融霜的影响[J].流体机械,1994,22(7):107-112.
[29]石文星,李先庭,邵双全.房间空调器热气旁通法除霜分析及实验研究[J].制冷学报,2000,(2):29-35.
[30]陈汝东,许东晟.制冷装置除霜方法的研究[J].同济大学学报,1998,26(5):566-569.
[31]庄友明.食品冷库除霜方法及其能耗分析[J].集美大学学报(自然科学版),2006,11(1):62-65.
[32]臧润清,方筝,李景丽,等.恒温恒湿机在结霜工况下运行的实验研究[J].低温工程, 2005,(3):60-64.
[33]连添达,臧润清.制冷装置设计[M].北京:中国经济出版社,1995.
[34]刘清江.冷库空气冷却器融霜节能的研究[J].制冷,2005,24(4):12-15.
[35]阚杰,郝亮,李涛,等.间接制冷系统中除霜、能耗及温室效应的比较[J].制冷与空调,2005,5(3):53-56.
[36]李宝华,宋海英.浅谈热气除霜的节能[J].大化科技,1999,(2):39-40.
[37]何志龙,黄东,袁秀玲.衡量结霜时间的指标—湿温比[J].流体机械,2000,(7):55-57.
[38]王文涛,姜锦英.结霜传感器[J].研究动态,2001,(10):19-21.
[39]郑钢,谷波,王志毅.对化霜控制问题的探讨[J].制冷与空调,2002,(6):15-19.
[40]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[J].流体机械,2003,(10):44-47.
[41]陈汝东,许东晟.空气热源热泵空调器最佳除霜点的控制[J].空调暖通技术,1996,(4):7-9.
[42]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[J].暖通空调,2001,(3):67-69.
[43]王铁军,刘向农.风源热泵模糊自修正除霜技术应用研究[J].制冷学报,2005,(1):29-32.
[44]吴业正,韩宝琦.制冷原理及设备[M].西安:西安交通大学出版社,2003.
[45]DR.A.E.Dahiri.A compressor simulation model with corrections for the level of suction gas superheat[J].ASHRAE Transactions,1981,87:771-782.
[46]K.A.Manske,D.T.Reindl,S.A.Klein.Evaporative condenser control in industrial refrigeration systems[J].International Journal of Refrigeration,2001,24:676-691.
[47]B.B.雅柯勃松.小型制冷机[M].北京:机械工业出版社,1982.
[48]F.C.Mcquiston.Finned tube heat exchangers:state of the art for the air side[J].ASHRAE Transactions,1981,87:1077-1085.
[49]杨世铭.传热学[M].北京:高等教育出版社,1995.
[50]J.P.Holman.Heat transfer[M].New York:McGraw-Hill Book Company,1986.
[51]彦启森.空气调节用制冷技术[M].北京:中国建筑工业出版社,第二版,1985.
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