【作者】 郑晓峰；

【导师】 臧润清；

【作者基本信息】 天津商业大学 ， 制冷及低温工程， 2008， 硕士

【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。更多还原

【Abstract】 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.更多还原