July 26, 2022
With the development of modern society and economy, people have higher and higher requirements for air temperature and humidity in industrial production environments, and the application fields of constant temperature and humidity environment control equipment are also becoming more and more extensive. The following will introduce the principle and daily maintenance method of the constant temperature and humidity machine.
The principle of constant temperature and humidity machine
The constant temperature and humidity machine is composed of a refrigeration system, a heating system, a control system, a humidity system, an air supply circulation system, and a sensor system. The above systems belong to two major aspects: electrical and mechanical refrigeration. The working principle and working process of several main systems are described below.
1. Refrigeration system: The refrigeration system is one of the key parts of the constant temperature and humidity machine. Generally speaking, the refrigeration methods are mechanical refrigeration and auxiliary liquid nitrogen refrigeration. The mechanical refrigeration adopts vapor compression refrigeration, which is mainly composed of a compressor, a condenser, a throttling mechanism and an evaporator. If the low temperature of our test is to reach -55 ℃, single-stage refrigeration is difficult to meet the requirements, so the refrigeration method of constant temperature and humidity machine generally adopts cascade refrigeration. The refrigeration system of the constant temperature and humidity machine consists of two parts, called the high temperature part and the low temperature part, 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 evaporates; the evaporation of the refrigerant in the low temperature part absorbs heat from the object to be cooled (the air in the test machine) to obtain the cooling capacity. The high temperature part and the low temperature part are connected by an evaporative condenser, which is both the condenser of the high temperature part and the condenser of the low temperature part.
2. Heating system: The heating system is relatively simple compared to 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 provided on the bottom plate of the testing machine.
3. Control system: The control system is the core of the comprehensive test box, which determines the heating rate, precision and other important indicators of the test machine. Most of the controllers of the testing machine use PID control, and a small number of them use a combination of PID and fuzzy control. Because the control system basically belongs to the category of software, and this part generally does not have problems during use.
4. Humidity system: The temperature system is divided into two subsystems, humidification and dehumidification. The humidification method generally adopts the steam humidification method, that is, the low-pressure steam is directly injected into the test space for humidification. This humidification method has high humidification ability, high speed, and sensitive humidification control, and is easy to achieve forced humidification especially when cooling down.
Cleaning and maintenance of constant temperature and humidity machine
The first step is to clean the appearance of the constant temperature and humidity tester, just wash it with ordinary water, or use soapy water, remember not to use corrosive liquids. 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 constant temperature and humidity testing machine should be cleaned of internal impurities before operation, and the power distribution room should be cleaned at least once a year to avoid dust in the air being adsorbed on the surface of the machine or accessories such as condensers and evaporators. Dry the body after cleaning and keep it dry.
The front is the cleaning of the inside and outside of the machine. As the core components of the constant temperature and humidity testing machine: the condenser, copper tube, evaporator, compressor and other refrigeration systems should be cleaned regularly, and the dust should be removed in time. In particular, the condenser should be maintained on a monthly basis. Use a vacuum cleaner or a brush to remove the dust attached to the cooling mesh of the condenser or spray the dust with high-pressure air. This can avoid overpressure and overload of the equipment. It is necessary to check whether there is oil leakage in copper pipes, functional joints, and welding ports.
Circuit breakers and over-temperature protectors in the constant temperature and humidity testing machine should also be checked regularly. In order to ensure the safety protection of the test product and the operator of the machine. The water storage tank in the constant temperature and humidity testing machine should be replaced once a month, and only pure water can be used. The humidifying water pan should be cleaned once a month to ensure smooth water flow. Finally, you should also pay attention to changing the ball wet gauze as appropriate, and it is recommended to replace it every three months.
The principle of the constant temperature and humidity machine is introduced. We can know that the constant temperature and humidity machine mainly provides constant humidity and heat, complex high and low temperature alternating and other test environments and test conditions for electronic components, industrial materials, and finished products in the research and development, production and inspection links. Applicable to electronic appliances, communications, chemicals, hardware, rubber, toys and other industries.
