Air Cooled Constant Temperature And Humidity Air Conditioner

Temperature and humidity control in air conditioning system is composed of refrigeration system, heating system, control system, humidity system, air circulation system, and sensor system. The above systems are divided into two 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. Mechanical refrigeration adopts vapor compression refrigeration, which are mainly composed of compressors, condensers, throttling mechanisms and evaporators. If the temperature of our test is as low as -55°C, single-stage refrigeration is difficult to meet the requirements, so the refrigeration method of constant temperature and humidity machines 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 from the refrigerant in the low-temperature part and vaporizes; 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 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: Compared with the refrigeration system, the heating system is relatively simple. It is mainly composed of high-power resistance wires. Due to the high heating rate required by the test, the power of the heating system is relatively large, and a heater is also installed 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 heating rate, precision and other important indicators of the testing machine. At present, most of the controllers of testing machines use PID control, and a small part of them use the 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, fast speed, and sensitive humidification control, especially when the temperature is lowered, it is easy to realize forced humidification.

There are two ways of dehumidification: mechanical refrigeration dehumidification and dry dehumidification. The dehumidification principle of mechanical refrigeration dehumidification is to cool the air below the dew point temperature, so that the water vapor greater than the saturated moisture content is condensed and precipitated, thus reducing the humidity. The dehumidification of the dryer is to use the air pump to extract the air in the test chamber, inject the dry air, and at the same time send the humid air into the recyclable dryer for drying, and then send it into the test chamber after drying, so that the cycle is repeated for dehumidification . At present, most comprehensive test chambers adopt the former dehumidification method and the latter dehumidification method, which can make the dew point temperature below 0°C. It is suitable for occasions with special requirements, but the cost is more expensive.

5. Sensor System: The sensors are mainly temperature and humidity sensors. Platinum electric groups and thermocouples are widely used in temperature sensors. There are two methods of measuring humidity: wet and dry bulb thermometer method and solid-state electronic sensor direct measurement method. Due to the low measurement accuracy of the dry-wet bulb method, the current constant temperature and humidity chambers are gradually replacing the dry-wet bulb with solid-state sensors to measure humidity.

6. Air Circulation System: The air circulation system generally has a centrifugal fan and an electric drive to drive it.Mechanism composition. It provides circulation of air within the testing machine.

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