【作者】 丁静萍；

【导师】 杨昭；

【作者基本信息】 天津大学 ， 制冷及低温工程， 2008， 硕士

【摘要】 本文旨在研究恒温恒湿系统除霜控制方法,寻找到最优的除霜开始时刻和除霜结束时刻,使得除霜时库内温度保持在不影响果蔬品质的范围内,同时除霜间隔最大。以此为目的,本文研究了本实验台结霜时库内温度、湿度和风机转速对结霜的不同影响,分析了不同工况下参数的不同变化规律。在结霜达到不同的厚度时开始除霜,同时结合不同的停除霜加热器的时刻,分析了这些不同的开始除霜和结束除霜时刻对库内温升的影响。根据结霜和除霜实验的分析结果,提出了以稳定运行时间、翅片温度、穿过蒸发器的空气压差、库内温度与蒸发温度的差值、库内温度与蒸发温度差值的变化率作为除霜开始时刻的控制参数,以压差和翅片温度作为除霜结束阶段主要参数的除霜控制方法,并确定了各参数的设定值。同时,本文结合本实验台变频的特点,提出了“低频除霜”的除霜控制方法,并比较了在结霜厚度达到相同值后开始“停机除霜”和“低频除霜”的区别,分析了两者的优劣。最后本文设计完成了“停机除霜”与“低频除霜”控制方法的程序流程,根据除霜流程编制了除霜控制程序,最后对本文的除霜控制方法的特点进行了总结。更多还原

【Abstract】 In order to maintain the temperature under the confine of fruits and vegetables storage when defrosting, and at the same time defrost as least as possible in a period of time, the optimum beginning time and end time of defrost of this cold storage system must be found.For this purpose, the impact on parameters of air temperature, humidity and fan speed when frost is analyzed. And the influences on the rise of temperature inside the cold storage of different beginning time and end time of defrost are also studied. Based on the analysis of the frost and defrost experiment results, the time that the system stable operate, the fin temperature, the pressure margin of the air through the evaporator, the margin of bank temperature and evaporation temperature, the rate of the margin change of bank temperature and evaporation temperature are taken as the control parameters of the defrost beginning time, and the pressure margin of the air through the evaporator and the fin temperature are taken as the main control parameters of the defrost end time. The values of the parameters are also confirmed.On account of the characteristics of frequency-conversion of this system,“low-frequency defrosting”is proposed this paper. And the pros and cons of“low-frequency defrosting”and“shutdown defrosting”are analysised. The defrost interface and the defrost control process are completed finally.更多还原