【作者】 姚秀；

【导师】 臧润清；

【作者基本信息】 天津商业大学 ， 制冷及低温工程， 2007， 硕士

【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。更多还原

【Abstract】 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.更多还原