Dongguan Haotian Testing Equipment Co., Ltd
yuhongmei0812@163.com
13712072775
Building 2, Yihai Science and Technology Park, No. 25 Yuanxia Road, Changping Town, Dongguan City, Guangdong Province
Its working principle can be understood asHumidity ChamberOn the basis of this, a powerful system has been integrated“vacuum system”And solved the complex technical challenges brought by the collaborative work of the three parties.
The following is a detailed breakdown of its core working principle:
Compared to ordinary temperature and humidity chambers, it has an additional set of critical systems:
Pressure system (core addition)Used to create and maintain low-pressure environments.
vacuum pumpCore component, used to extract air from the box and reduce air pressure.
pressure sensorReal time monitoring of air pressure inside the box.
Sealed enclosureA high-strength, high sealing studio specially designed to withstand huge internal and external pressure differences.
intake valveAfter the experiment is completed, smoothly inject air into the box to restore normal pressure.
refrigeration systemNot only should it achieve low temperature, but it should also work efficiently under low pressure.
heating systemTo achieve high temperature, it is usually integrated into the interlayer or air duct of the box.
Humidification systemRealizing humidification under normal and low pressure (technical difficulty).
dehumidification systemUsually served by the refrigeration system.
control systemA more complex multivariable collaborative controller.
Vacuum pumping process：
Close the door of the test chamber (with high-strength sealing strip).
Control system startupvacuum pumpContinuously extract the air from the studio.
pressure sensorReal time feedback of air pressure value. When the set low air pressure value (such as 1 kPa, equivalent to an altitude of 31000 meters) is reached, the control system will adjust the power of the vacuum pump or maintain pressure stability through intermittent start stop.
Process of restoring normal pressure：
After the experiment is completed, the control system will turn off the vacuum pump and slowly open itintake valve.
After filtering, the external air is smoothly injected into the working chamber to restore the pressure to normal atmospheric pressure, avoiding any impact on the sample.
Basic PrinciplesSimilar to a regular test chamber:heaterHeating,refrigeration systemCooling down.
Special challenges and solutions：
Enhance air circulationUsing more powerful fans to forcefully stir the thin air and maximize heat transfer efficiency.
Using liquid nitrogen (LN2) coolingFor equipment with rapid cooling requirements, liquid nitrogen is often directly injected for cooling, and its cooling capacity does not depend on air density, and it is still efficient at low pressure.
Slow heatingThe heater power needs to be greater.
Cooling down is more difficultThe heat exchange efficiency of the evaporator decreases.
Thin air makes heat transfer difficultUnder low air pressure, the number of air molecules decreases sharply, and the heat transfer efficiency relying on air convection and conduction is greatly reduced. This will lead to:
Solution：
This is one of the most technically challenging parts of the device.
challenge：
Under low pressure, the boiling point of water will decrease. For example, at a pressure of 10 kPa, water will boil at approximately 45 ° C. This means that traditional boiler type steam humidification (which requires heating water to 100 ° C) cannot function properly at low pressure.
The definition of relative humidity (RH) is related to the saturated water vapor content at temperature and pressure. As the air pressure changes, the saturated water vapor content also changes, making the calculation and measurement models more complex.
Solution：
High pressure atomization/ultrasonic humidificationBoil water into tiny mist at the micrometer level and spray it directly into the air, without relying on water boiling.
Saturated gas humidification methodFirstly, humidify a small stream of air at atmospheric pressure until it reaches saturation, and then precisely inject this saturated moist air into the low-pressure main test chamber.
Special humidifierAdopting humidification technology that can adapt to low-pressure environments, such as:
Complex calculations and calibrationThe control system is equipped with an algorithm that automatically adjusts the humidity setting and sensor readings based on the current temperature and pressure.
The essence of this device lies in its control system's seamless coordination of air pressure, temperature, and humidity systems. As a typical example“High altitude environmental simulation”Test as an example:
Initial stateThe box is at room temperature, normal pressure, and constant humidity.
Stage 1: Creating a low-pressure environment
vacuum systemStart up and reduce the air pressure inside the box to the target value (such as simulating an altitude of 5000 meters).
At this moment,temperature systemMay be in standby mode or maintaining the current temperature state.
Stage 2: Temperature and humidity cycling under low pressure
Low temperature and low pressureControl system startuprefrigeration systemReduce the temperature to -40 ° C in a low-pressure environment. Due to the thin air, the cooling power and time need to be accurately calculated.
High temperature, high humidity, and low pressureStart the control system firstheating systemRaise the temperature to+60 ° C under low pressure. Then, activate the specialHumidification systemRaise the humidity to 95% RH. This process requires very precise control to prevent water from condensing or boiling on low-temperature surfaces.
Stage 3: Recovery
Test completed, first stop humidifying and heating/cooling.
Then, slowly open itintake valveRestore the air pressure to normal pressure smoothly.
Finally, open the door and take out the sample.