Introduction To The Working Principle Of Constant Temperature And Humidity Test Chamber
With the development of modern society and economy, people have higher and higher requirements for air temperature and humidity in industrial production environment, and the application field of constant temperature and humidity environmental control equipment is more and more extensive. Let's introduce the principle and daily maintenance method of constant temperature and humidity machine.
1、 Principle of constant temperature and humidity machine
The constant temperature and humidity machine is composed of refrigeration system, heating system, control system, humidity system, air supply and circulation system and sensor system. The above systems belong to electrical and mechanical refrigeration. The following describes the working principle and working process of several main systems.
1. Refrigeration system: refrigeration system is one of the key parts of constant temperature and humidity machine. Generally speaking, the refrigeration methods are mechanical refrigeration and auxiliary liquid nitrogen refrigeration. Mechanical refrigeration adopts steam compression refrigeration, which is mainly composed of compressor, condenser, throttling mechanism and evaporator. If the low temperature of our test is to reach - 55 ℃, single-stage refrigeration is difficult to meet the requirements, so the refrigeration mode of constant temperature and humidity machine generally adopts cascade refrigeration. The refrigeration system of constant temperature and humidity machine consists of two parts, which are called high temperature part and low temperature part respectively. Each part is a relatively independent refrigeration system. The evaporation of the refrigerant in the high-temperature part absorbs the heat of the refrigerant from the low-temperature part and vaporizes; The evaporation of low-temperature refrigerant absorbs heat from the cooled object (air in the testing machine) to obtain cooling capacity. The high-temperature part and the low-temperature part are connected by an evaporative condenser, which is not only the condenser of the high-temperature part, but also the condenser of the low-temperature part.
2. Heating system: the heating system is relatively simple compared with the refrigeration system. It is mainly composed of high-power resistance wires. Due to the large heating rate required by the test, the power of the heating system is relatively large, and a heater is also set on the bottom plate of the testing machine.
3. Control system: the control system is the core of the comprehensive test chamber, which determines the temperature rise rate, accuracy and other important indexes of the test machine. Most of the controllers of the testing machine adopt PID control, and a few adopt the control mode of the combination of PID and fuzzy control. Since the control system basically belongs to the category of software, and this part will not have problems in the process of use.
4. Humidity system: the temperature system is divided into two subsystems: humidification and dehumidification. Steam humidification method is generally adopted, that is, low-pressure steam is directly injected into the test space for humidification. This humidification method has the advantages of humidification ability, fast speed and sensitive humidification control. It is easy to realize forced humidification especially when cooling.
2、 Cleaning and maintenance of constant temperature and humidity machine
The first step is to clean the appearance of the constant temperature and humidity testing machine. Just wash it with ordinary water or use soapy water. Remember not to use corrosive liquid. And the ground around and at the bottom of the box should also be kept clean. The outside of the box must be cleaned more than once a year to minimize dust.
The second step is to clean the interior of the constant temperature and humidity testing machine studio. The internal impurities of the constant temperature and humidity testing machine shall be removed before operation, and the power distribution room shall be cleaned at least once a year to prevent the dust in the air from adsorbing on the machine surface or condenser, evaporator and other accessories. After cleaning, the machine body shall be dried and kept dry.
The front is the cleaning of the inside and outside of the body. As the core components of the constant temperature and humidity testing machine: condenser, copper pipe, evaporator, compressor and other refrigeration systems, we should pay more attention to regular cleaning, and dust should be removed in time. In particular, the condenser shall be maintained on schedule every month. Use a vacuum cleaner or brush to absorb and brush the dust attached to the condenser cooling net or spray the dust with high-pressure air This can avoid overpressure, overload and other phenomena of the equipment. Check whether there is oil leakage at the copper pipe, functional joints and welding joints, and deal with it immediately.
The circuit breaker and overtemperature protector in the constant temperature and humidity tester shall also be checked regularly. To ensure the safety protection of the test object and operator of the machine. The water storage tank in the constant temperature and humidity testing machine shall be replaced once a month, and only purified water can be used. The humidifying water tray shall be cleaned once a month to ensure smooth water flow. Finally, we should also pay attention to the replacement of wet gauze as appropriate. It is recommended to replace it once every three months.
Introduction to the principle of constant temperature and humidity machine. We can know that the constant temperature and humidity machine mainly provides constant damp heat, complex high and low temperature alternation and other test environment and test conditions for the tests of electronic parts, industrial materials and finished products in R & D, production and inspection. It is suitable for electronic and electrical appliances, communication, chemical industry, hardware, rubber, toys and other industries.
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