-70 degree high and low temperature test box refrigeration principle

-70 degree high and low temperature test box refrigeration principle

High and low temperature test chamber is a kind of simulated environmental test equipment integrating high temperature test, low temperature test and high and low temperature cycle test. The conventional temperature range is 0°C～+150°C -20°C～+150°C -40°C～+150 °C -70 °C ~ +150 °C, the most complex of which is -70 °C ~ +150 °C.

Why do you say that the most complicated is -70 °C ~ +150 °C this temperature range, first of all do not say high temperature 150 degrees, because the relatively high temperature is relatively easy to control the low temperature, popular point is that there is no technical content; mainly talk about low temperature, remove the cooling rate In this regard, a low temperature of 0°C to -40°C is normally satisfied by a single compressor, which is the so-called single-stage refrigeration. When a low temperature of -70°C is used, two compressors must be used at the same time to satisfy the requirement. Cascading refrigeration.

-70 degree high and low temperature test chambers mostly use cascade refrigeration, which is divided into high temperature part and low temperature part. High temperature part adopts R404A or R507A medium temperature refrigerant, while low temperature part uses R23A as low temperature refrigerant, high temperature part and low temperature part. Two completely independent refrigeration systems, but they are closely linked to each other.

As shown in the figure below, when the user sets the temperature of the high and low temperature chamber to -70 degrees, the controller will output a command to the contactor to start the compressor of the R404A system. The compressor discharges the high temperature and high pressure gas through the condenser and the dry filter. The equipment such as the sleeving and the yarn tube eventually enters the evaporative condenser, which is also known as the plate heat exchanger; it prepares for starting the R23 cooling and finally returns to the low-temperature part R404A compressor, and so on.

After a few minutes of normal operation of the R404 system, the compressor of the R23 system is started. The compressor discharges the high-temperature and high-pressure gas through the evaporative condenser, that is, the plate heat exchanger. The capillary throttling reduces the pressure to form a low-temperature and low-pressure liquid refrigerant, and finally enters the working chamber. Inside the evaporator installed in the box, the principle of circulation heat absorption and circulation motor continuously force the air flow in the studio to take away the heat from the studio to achieve the purpose of cooling.

The last point to focus on is the evaporative condenser, which acts as both an evaporator for the primary R404 system and a condenser for the secondary R23 system. It belongs to a comparative core in the refrigeration system of the -70 degree cryogenic chamber. Accessories.

-70 degree high and low temperature test box refrigeration schematic