Test Chamber

• Six Major Framework Structures and Operational Principles of Constant Temperature and Humidity Test Chambers

  Mar 13, 2025

  Refrigeration System The refrigeration system is one of the critical components of a comprehensive test chamber. Generally, refrigeration methods include mechanical refrigeration and auxiliary liquid nitrogen refrigeration. Mechanical refrigeration employs a vapor compression cycle, primarily consisting of a compressor, condenser, throttle mechanism, and evaporator. If the required low temperature reaches -55°C, single-stage refrigeration is insufficient. Therefore, Labcompanion's constant temperature and humidity chambers typically use a cascade refrigeration system. The refrigeration system is divided into two parts: the high-temperature section and the low-temperature section, each of which is a relatively independent refrigeration system. In the high-temperature section, the refrigerant evaporates and absorbs heat from the low-temperature section's refrigerant, causing it to vaporize. In the low-temperature section, the refrigerant evaporates and absorbs heat from the air inside the chamber to achieve cooling. The high-temperature and low-temperature sections are connected by an evaporative condenser, which serves as the condenser for the high-temperature section and the evaporator for the low-temperature section.   Heating System The heating system of the test chamber is relatively simple compared to the refrigeration system. It mainly consists of high-power resistance wires. Due to the high heating rate required by the test chamber, the heating system is designed with significant power, and heaters are also installed on the chamber's base plate.   Control System The control system is the core of the comprehensive test chamber, determining critical indicators such as heating rate and precision. Most modern test chambers use PID controllers, while a few employ a combination of PID and fuzzy control. Since the control system is primarily based on software, it generally operates without issues during use.   Humidity System The humidity system is divided into two subsystems: humidification and dehumidification. Humidification is typically achieved through steam injection, where low-pressure steam is directly introduced into the test space. This method offers strong humidification capacity, rapid response, and precise control, especially during cooling processes where forced humidification is necessary.   Dehumidification can be achieved through two methods: mechanical refrigeration and desiccant dehumidification. Mechanical refrigeration dehumidification works by cooling the air below its dew point, causing excess moisture to condense and thus reducing humidity. Desiccant dehumidification involves pumping air out of the chamber, injecting dry air, and recycling the moist air through a desiccant for drying before reintroducing it into the chamber. Most comprehensive test chambers use the former method, while the latter is reserved for specialized applications requiring dew points below 0°C, albeit at a higher cost.   Sensors Sensors primarily include temperature and humidity sensors. Platinum resistance thermometers and thermocouples are commonly used for temperature measurement. Humidity measurement methods include the dry-wet bulb thermometer and solid-state electronic sensors. Due to the lower accuracy of the dry-wet bulb method, solid-state sensors are increasingly replacing it in modern constant temperature and humidity chambers.   Air Circulation System The air circulation system typically consists of a centrifugal fan and a motor that drives it. This system ensures the continuous circulation of air within the test chamber, maintaining uniform temperature and humidity distribution.

  hot Tags : Constant Temperature and Humidity Chamber High-Precision Chamber Test Chamber Temperature Sensor Major Structures for Chamber Major Operation for Chamber

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• Uneven Temperature Distribution in High and Low Temperature Humid Test Chambers

  Mar 01, 2025

  The High and Low Temperature Humid Test Chambers is the main equipment in temperature and humidity environment testing, mainly used for evaluating the temperature and humidity tolerance of products, so as to ensure that our products can work and operate normally under any environmental conditions. However, if the temperature uniformity exceeds the allowable deviation range during environmental testing in the Chambers, the data obtained from the test is unreliable and cannot be used as the ultimate tolerance for high and low temperature testing of materials. So what are the reasons that can cause temperature uniformity to exceed the allowable deviation range?     1. The differences test objects in the High and Low Temperature Humid Test Chamber: If test samples that to a great extent affect the overall camber’s internal heat convection, it will inevitably affect the uniformity of internal sample’s temperature. For example, if LED lighting products are test, the products themselves emit light and heat, becoming a thermal load, which will has a significant impact on temperature uniformity.   2.  The volume of the tested object: If the volume of the test object is too large, or the placing position in the chamber is inappropriate, it will obstruct the air convection inside and also cause significant temperature uniformity deviation. For Placing the test product next to the air duct seriously affects the circulation of air, and of course, the uniformity of temperature will be greatly affected.     3. The internal structure design of the chamber: This aspect is mainly reflected in sheet metal design and processing, such as the design of air ducts, the placement of heating pipes, and the size of fan power. All of these will affect the temperature uniformity inside the camber.    4. Design of the camber’s inner wall: Due to the different structures about the inner wall of the test chamber, the temperature of the inner wall will also be uneven, which will affect the heat convection inside the working chamber and cause deviation in the internal temperature uniformity.     5. The six sides of the camber have uneven heat dissipation: Due to the different heat transfer coefficients on the front, back, left, right, top, and bottom surfaces of the camber’s wall, some sides have threading holes, others have testing holes, etc., which will cause local heat dissipation and transfer, resulting in uneven temperature distribution of the camber and uneven radiative convective heat transfer on the wall, final affecting temperature uniformity.     6. The leakproofness of camber’s door: The sealing of the camber and door is not strict, for example, the sealing strip is not customized and has seams between door and wall, the door will leaks the air, which is going to affects the temperature uniformity of the hole camber.     In summary, those may the culprit affected the temperature uniformity inside the test chamber, we suggest that you can investigate from these aspects one by one, which will surely solve your confusion and difficulties.  

  hot Tags : High and Low Temperature Humid Test Chambers Uneven Temperature Distribution in Camber safe of chamber Test Chamber

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