The refrigeration system is an important part of the constant temperature and Humidity Chamber. Generally speaking, the refrigeration method of the constant temperature and humidity box is mechanical refrigeration and liquid nitrogen auxiliary refrigeration. Mechanical refrigeration uses vapor compression refrigeration. It is mainly composed of compressor, condenser, throttling mechanism and evaporator.
The main operating system of the constant temperature and humidity chamber is the low-temperature refrigeration system, and the assembly of the compressor in the entire cooling system is very important.
Since the low temperature we tested needs to reach -40°C, single-stage refrigeration is difficult to meet the requirements, so the cabinet refrigeration method tested is generally cascade refrigeration. The refrigeration system of the constant temperature and humidity chamber is divided into two parts, the high temperature part and the low temperature part, which is a relatively independent refrigeration system.
The evaporation of the refrigerant in the high temperature zone absorbs the heat of the refrigerant in the low temperature zone and evaporates, and the evaporation of the refrigerant in the low temperature zone absorbs heat from the object to be cooled (air in the test room) to obtain coldness. An evaporative condenser is used between the high temperature section and the low temperature section, and can be used as a condenser for the high temperature section and the low temperature section.
1. Distinguish the quality of the constant temperature and Humidity Chamber through comprehensive performance and stability
When the ordinary compressor starts, the noise of the stability test box manufacturer's products is extremely low (less than or equal to 60dB). If the compressor noise exceeds 80dB and is louder than the compressor of other equipment, if it is not used, it will definitely fail.
If the low-temperature refrigeration is very slow when the constant temperature and Humidity Chamber is running, and if the compressor body is very hot when the compressor body is touched by hand, it is easy to cause problems. The machine needs to be shut down immediately and the supplier needs to be notified for repair and inspection of accessories.
2. Distinguish the difference between a new compressor and a second-hand compressor in a constant temperature and humidity room
In order to reduce costs, some unscrupulous businesses buy or recycle some second-hand compressors and sell them to customers at high prices. While this reduces costs, the refrigeration systems and compressors used in future equipment have a very high potential for failure and shortened service life.
Usually the appearance of the new compressor is brighter, the color is bright, the label is clear, and the welding port of the copper pipe is directly welded at one time, and there is no trace of the old welding. If it is a second-hand compressor, the color of the shell generally looks very dull, and the welded joints of the copper pipes have traces of repeated grinding or overlapping welding many times.
The refrigeration system of the temperature and Humidity Chamber complements the compressor. The minimum evaporating temperature of a single-stage vapor compression refrigerator mainly depends on its condensing pressure and compression ratio. For any refrigerant, the lower the evaporation temperature, the lower the evaporation pressure. When the evaporation temperature is too low, some commonly used refrigerants have reached the freezing temperature, and the flow and circulation of the refrigerant cannot be realized. The evaporation pressure decreases, the refrigerant volume increases, and the refrigerant mass flow rate decreases. At this time, in order to obtain the required cooling capacity, it is necessary to increase the suction capacity, thereby making the compressor larger.
