Some companies equip their refrigeration systems with a wide array of components, ensuring that every part mentioned in textbooks is included. However, is it truly necessary to install all these components? Does installing all of them always bring benefits? Let's analyze this matter and share some insights with fellow enthusiasts. Whether these insights are correct or not is open to interpretation.

 

Oil Separator

 

An oil separator allows most of the compressor lubricating oil carried out from the compressor discharge port to return. A small portion of the oil must circulate through the system before it can return with the refrigerant to the compressor suction port. If the system's oil return is not smooth, oil can gradually accumulate in the system, leading to reduced heat exchange efficiency and compressor oil starvation. Conversely, for refrigerants like R404a, which have limited solubility in oil, an oil separator can increase the saturation of oil in the refrigerant. For large systems, where the piping is generally wider and oil return is more efficient, and the oil volume is larger, an oil separator is quite suitable. However, for small systems, the key to oil return lies in the smoothness of the oil path, making the oil separator less effective.

 

Liquid Accumulator

 

A liquid accumulator prevents uncondensed refrigerant from entering or minimally entering the circulation system, thereby improving heat exchange efficiency. However, it also leads to increased refrigerant charge and lower condensation pressure. For small systems with limited circulation flow, the goal of liquid accumulation can often be achieved through improved piping processes.

 

Evaporator Pressure Regulating Valve

 

An evaporator pressure regulating valve is typically used in dehumidification systems to control the evaporation temperature and prevent frost formation on the evaporator. However, in single-stage circulation systems, using an evaporator pressure regulating valve requires the installation of a refrigeration return solenoid valve, complicating the piping structure and hindering system fluidity. Currently, most test chambers do not include an evaporator pressure regulating valve.

 

 

Heat Exchanger

 

A heat exchanger offers three benefits: it can subcool the condensed refrigerant, reducing premature vaporization in the piping; it can fully vaporize the return refrigerant, reducing the risk of liquid slugging; and it can enhance system efficiency. However, the inclusion of a heat exchanger complicates the system's piping. If the piping is not arranged with careful craftsmanship, it can increase pipe losses, making it less suitable for companies producing in small batches.

 

Check Valve

 

In systems used for multiple circulation branches, a check valve is installed at the return port of inactive branches to prevent refrigerant from flowing back and accumulating in the inactive space. If the accumulation is in gaseous form, it does not affect system operation; the main concern is preventing liquid accumulation. Therefore, not all branches require a check valve.

 

Suction Accumulator

 

For refrigeration systems in environmental testing equipment with variable operating conditions, a suction accumulator is an effective means to avoid liquid slugging and can also help regulate refrigeration capacity. However, a suction accumulator also interrupts the system's oil return, necessitating the installation of an oil separator. For units with Tecumseh fully enclosed compressors, the suction port has an adequate buffer space that provides some vaporization, allowing the omission of a suction accumulator. For units with limited installation space, a hot bypass can be set up to vaporize excess return liquid.

 

Cooling Capacity PID Control

 

Cooling capacity PID control is notably effective in operational energy savings. Moreover, in thermal balance mode, where temperature field indicators are relatively poor around room temperature (approximately 20°C), systems with cooling capacity PID control can achieve ideal indicators. It also performs well in constant temperature and humidity control, making it a leading technology in refrigeration systems for environmental testing products. Cooling capacity PID control comes in two types: time proportion and opening proportion. Time proportion controls the on-off ratio of the refrigeration solenoid valve within a time cycle, while opening proportion controls the conduction amount of the electronic expansion valve.

However, in time proportion control, the lifespan of the solenoid valve is a bottleneck. Currently, the best solenoid valves on the market have an estimated lifespan of only 3-5 years, so it's necessary to calculate whether the maintenance costs are lower than the energy savings. In opening proportion control, electronic expansion valves are currently expensive and not easily available on the market. Being a dynamic balance, they also face lifespan issues.

To achieve the desired test conditions in a constant temperature and humidity test chamber, it is inevitable to perform humidification and dehumidification operations. This article analyzes the various methods commonly used in Labcompanion constant temperature and humidity test chambers, highlighting their respective advantages, disadvantages, and recommended conditions for use.

Humidity can be expressed in many ways. For test equipment, relative humidity is the most commonly used concept. Relative humidity is defined as the ratio of the partial pressure of water vapor in the air to the saturation vapor pressure of water at the same temperature, expressed as a percentage.

From the properties of water vapor saturation pressure, it is known that the saturation pressure of water vapor is solely a function of temperature and is independent of the air pressure in which the water vapor exists. Through extensive experimentation and data organization, the relationship between water vapor saturation pressure and temperature has been established. Among these, the Goff-Gratch equation is widely adopted in engineering and metrology and is currently used by meteorological departments to compile humidity reference tables.

Humidification Process

 

Humidification essentially involves increasing the partial pressure of water vapor. The earliest method of humidification was to spray water onto the chamber walls, controlling the water temperature to regulate the surface saturation pressure. The water on the chamber walls forms a large surface area, through which water vapor diffuses into the chamber, increasing the relative humidity inside. This method emerged in the 1950s.

 

At that time, humidity control was primarily achieved using mercury contact conductivity meters for simple on-off regulation. However, this method was poorly suited for controlling the temperature of large, lag-prone water tanks, resulting in long transition processes that could not meet the demands of alternating humidity tests requiring rapid humidification. More importantly, spraying water onto the chamber walls inevitably led to water droplets falling on the test samples, causing varying degrees of contamination. Additionally, this method posed certain requirements for drainage within the chamber.

 

This method was soon replaced by steam humidification and shallow water pan humidification. However, it still has some advantages. Although the control transition process is lengthy, the humidity fluctuations are minimal once the system stabilizes, making it suitable for constant humidity tests. Furthermore, during the humidification process, the water vapor does not overheat, thus avoiding the addition of extra heat to the system. Additionally, when the spray water temperature is controlled to be lower than the required test temperature, the spray water can act as a dehumidifier.

 

Development of Humidification Methods

 

With the evolution of humidity testing from constant humidity to alternating humidity, there arose a need for faster humidification response capabilities. Spray humidification could no longer meet these demands, leading to the widespread adoption and development of steam humidification and shallow water pan humidification methods.

 

Steam Humidification

 

Steam humidification involves injecting steam directly into the test chamber. This method offers rapid response times and precise control over humidity levels, making it ideal for alternating humidity tests. However, it requires a reliable steam source and can introduce additional heat into the system, which may need to be compensated for in temperature-sensitive tests.

 

Shallow Water Pan Humidification

 

Shallow water pan humidification uses a heated water pan to evaporate water into the chamber. This method provides a stable and consistent humidity level and is relatively simple to implement. However, it may have slower response times compared to steam humidification and requires regular maintenance to prevent scaling and contamination.

 

Dehumidification Process

 

Dehumidification is the process of reducing the partial pressure of water vapor in the chamber. This can be achieved through cooling, adsorption, or condensation methods. Cooling dehumidification involves lowering the temperature of the chamber to condense water vapor, which is then removed. Adsorption dehumidification uses desiccants to absorb moisture from the air, while condensation dehumidification relies on cooling coils to condense and remove water vapor.

 

Conclusion

 

In summary, the choice of humidification and dehumidification methods in constant temperature and humidity test chambers depends on the specific requirements of the tests being conducted. While older methods like spray humidification have their advantages, modern techniques such as steam humidification and shallow water pan humidification offer greater control and faster response times, making them more suitable for advanced testing needs. Understanding the principles and trade-offs of each method is crucial for optimizing test chamber performance and ensuring accurate and reliable results.

Rechargeable battery, which can be re-active by charging after be used. They are widely used in the fields of environmentally friendly vehicles, power storage, and Dynamic field.

Environmental testing of rechargeable battery is an important means of evaluating their performance under different environmental conditions.

Ⅰ.  Testing Purpose

The environmental testing of rechargeable battery aims to simulate various conditions that may be encountered in actual usage environments to evaluate the reliability and performance of the battery. Through testing, it is possible to understand the conditions of working battery under different temperature, humidity, vibration, impact and other conditions, providing scientific basis for the research and development, production and use of battery.

Ⅱ.  Testing content

A. Temperature testing

a. High temperature test: Rich a high temperature environment to observe its temperature stability and the risk of thermal runaway.

b. Low temperature testing: Testing the discharge performance, capacity degradation, and low-temperature starting ability of the battery under low temperature conditions.

c. Temperature cycling test: Simulate the temperature changes that the battery may experience in actual use, evaluate its thermal durability and cycle life.

B. Humidity test: Evaluate the battery’s performance, sealing, and corrosion resistance in a humid environments.

C. Vibration testing: Through simulate the battery in the vibration environment that may encounter during transportation, installation, and use, evaluate its structural integrity, electrical connection reliability, and performance stability.

D. Impact testing: Through simulating the battery in unexpected situations such as drops and collisions, and evaluate their impact resistance.

E. External short circuit test: Test the performance of the battery under external short circuit conditions, including risks of thermal runaway and explosion and so on.

Ⅲ. Test standards and specifications

The environmental testing of rechargeable battery should follow relevant testing standards and specifications to ensure the accuracy and comparability of test results. Common testing standards include:

IEC 62133/ IEC 61960、UN 38.3、UL 1642/UL 2580、GB/T 31467、JIS C 8714

Ⅳ. Test equipment

Environmental testing on rechargeable battery requires the professional testing equipment and methods. Common testing equipment includes：

High and low temperature test chamber: Used to simulate different temperature environments.

Humidity test chamber: used to evaluate the performance of battery in humid environments.

Vibration test bench: Simulate vibration environment to evaluate the structural integrity and performance stability of battery.

Impact testing machine: used to simulate impacts in unexpected situations such as drops and collisions.

Ⅴ. Test results and evaluation

After completing the test, it is necessary to analyze and evaluate the test results. Based on test data and standard requirements, determine whether the performance of the battery meets the requirements under different environmental conditions. For undesirable battery, further analysis and corresponding improvement measures should be taken.

In summary, environmental testing of rechargeable battery is an important means to ensure their stable and reliable performance in practical use. Professional testing instruments can provide more professional, safe, scientific and effective experimental results for rechargeable battery testing, greatly reducing the cost of testing and bringing convenience to companies.

Click to check related products.

 

https://www.lab-companion.com/thermal-shock-test-chamber

https://www.lab-companion.com/temperature-and-humidity-chamber

https://www.lab-companion.com/rapid-temperature-cycling-test-chamber

 

 

The High-Low Temperature and Low Pressure Test Chamber is an experimental instrument for simulating the storage, operation, and transportation reliability on high-altitude, plateau areas climates in the national defense industry, aerospace industry automation components, automotive components, electronic and electrical components, plastics, chemical industry, food industry, pharmaceutical industry, and related products under the single or simultaneous action of high/low temperature and low pressure. It can also conduct electrical performance parameters on test specimens when powered on at the same time.

The High-Low Temperature and Low Pressure Test Chamber can perform high temperature, low temperature, altitude (not higher than 30000 meters or 45000 meters above sea level), high/low temperature cycle tests, and temperature altitude comprehensive tests on products (whole machine), components, and materials. During high and low temperature tests, this chamber can be used for testing heat dissipation samples and non heat dissipation samples. For the heat dissipation sample, its heat dissipation power cannot exceed the cooling capacity of the chamber, as the cooling capacity is a dynamic value that varies with temperature points.

Main materials of our equipment:

Adopting a bipolar rotary vane vacuum pump with high ultimate vacuum degree - ensuring efficient and stable operation of the equipment throughout its entire working range;

High strength and high reliability structural design - ensuring the high reliability of the equipment;

The inside chamber material is SUS304 stainless steel - with strong corrosion resistance, cold and hot fatigue function, long service life;

High density polyurethane foam insulation material - ensuring minimal heat loss;

Surface spraying treatment - ensuring the long-lasting anti-corrosion function and appearance life of the equipment;

High strength heat-resistant silicone rubber sealing strip - ensures high sealing performance of equipment doors;

Multiple optional functions (such as test holes, recorders, water purification systems, etc.) - ensuring users have multiple functions and testing needs;

Large area electric anti frost observation window and concealed lighting - providing good observation effect;

Environmentally friendly refrigerants - ensure that equipment better meets your environmental protection requirements;

*Customizable size/usage indicators/various optional features according to your requirements.

Main functions of our equipment:

Temperature control: It can achieve temperature constant control and program control;

The full process data recorder (optional function) can achieve full process recording and traceability of the experimental process;

Each motor is equipped with overcurrent (overheating) protection/heater short-circuit protection to ensure high reliability of air flow and heating during equipment operation;

USB interface and Ethernet communication function enable the device's communication and software expansion functions to meet various customer needs;

Adopting the internationally popular cooling control mode, the compressor cooling power can be automatically adjusted from 0% to 100%, reducing energy consumption by 30% compared to the traditional heating balance temperature control mode;

The key components of refrigeration and electrical control are all made of internationally renowned brand products, which improves and ensures the overall quality of the equipment.

The Solar Simulation Irradiation Test Chamber, also known as the "sunlight radiation protection test device," is categorized into three types based on test standards and methods: air-cooled xenon lamp (LP/SN-500), water-cooled xenon lamp (LP/SN-500), and benchtop xenon lamp (TXE). The differences among them lie in test temperature, humidity, accuracy, duration, etc. It is an indispensable testing instrument in the series of aging test chambers.

 

The test chamber utilizes an artificial light source combined with G7 OUTDOOR filters to adjust the system's light source, simulating the radiation found in natural sunlight, thereby meeting the requirements for solar simulators as stipulated in IEC 61646. This system light source is employed to conduct light aging tests on solar cell modules in accordance with IEC 61646 standards. During the testing, the temperature on the back of the modules must be maintained at a constant level between 50±10°C. The chamber is equipped with automatic temperature monitoring capabilities and a radiometer to control the light irradiance, ensuring it remains stable at the specified intensity, while also controlling the duration of the test.

 

Within the solar simulation irradiation test chamber, the period of ultraviolet (UV) light cycling typically shows that photochemical reactions are not sensitive to temperature. However, the rate of any subsequent reactions is highly dependent on the temperature level. These reaction rates increase as the temperature rises. Therefore, it is crucial to control the temperature during UV exposure. Additionally, it is essential to ensure that the temperature used in accelerated aging tests matches the highest temperature that materials would experience when directly exposed to sunlight. In the solar simulation irradiation test chamber, the UV exposure temperature can be set at any point between 50°C and 80°C, depending on the irradiance and ambient temperature. The UV exposure temperature is regulated by a sensitive temperature controller and a blower system, which ensures excellent temperature uniformity within the test chamber.

 

This sophisticated control over temperature and irradiance not only enhances the accuracy and reliability of the aging tests but also ensures that the results are consistent with real-world conditions, through this Solar Simulation Irradiation Test Chamber, which can provide valuable data for the development and improvement of solar cell technologies.

This product is designed for the fluorescent ultraviolet (UV) lamp method in laboratory light source exposure testing of various materials. It is primarily used to evaluate the changes in materials when exposed to outdoor conditions, as well as for durability testing of new material formulations and products.

 

This UV Aging Test Chamber utilizes fluorescent UV lamps that optimally simulate the UV spectrum of sunlight. Combined with temperature and humidity control devices, it replicates the effects of sunlight (UV spectrum), high temperature, high humidity, condensation, and dark cycles, which cause material damage such as discoloration, loss of brightness, reduced strength, cracking, peeling, chalking, and oxidation. Additionally, the synergistic effect of UV light and moisture weakens or nullifies the material's resistance to light or moisture, making it widely applicable for assessing the weather resistance of materials. This test chamber offers the best simulation of sunlight's UV spectrum, low maintenance and operational costs, ease of use, and high automation with programmable controllers for automatic test cycle operation. It also features excellent lamp stability and high reproducibility of test results.

 

The humidity system consists of a water tank and a humidification system. Through the mechanism of moisture condensation, the exposed surface of the sample is wetted, simulating rain, high humidity, and condensation, which, in conjunction with UV light and dark cycles, creates an optimal testing environment. The chamber is equipped with safety protection systems, including water shortage prevention, dry burn protection, over-temperature protection, short-circuit protection, and overload protection, located on the electrical control panel and inside the electrical control cabinet. Upon entering an alarm state, the equipment automatically cuts off the power to the working system, halts operation, and emits an audible alert to ensure the safety of both the equipment and the operator.

Introduction:
To ensure the quality of pharmaceutical products, stability testing must be conducted to estimate their shelf life and storage conditions. Stability testing primarily investigates the impact of environmental factors such as temperature, humidity, and light on the quality of pharmaceuticals over time. By studying the degradation curve of the product, the effective shelf life can be determined, ensuring the efficacy and safety of the drug during its use.

 

 

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Storage Conditions for Pharmaceuticals

General Storage Conditions

Test Type	Storage Conditions(Note 2)
Long-term Testing	25°C ± 2°C / 60% ± 5% RH or 30°C ± 2°C / 65% ± 5% RH
Accelerated Testing	40°C ± 2°C / 75% ± 5% RH
Intermediate Testing (Note 1)	30°C ± 2°C / 65% ± 5% RH

 

Note 1: If the long-term testing condition is already set at 30°C ± 2°C / 65% ± 5% RH, intermediate testing is not required. However, if the long-term condition is 25°C ± 2°C / 60% ± 5% RH and significant changes are observed during accelerated testing, intermediate testing should be added. The evaluation should be based on the criteria for "significant changes."

Note 2: For impermeable containers such as glass ampoules, humidity conditions may be exempt unless otherwise specified. However, all test items specified in the stability testing protocol must still be performed for intermediate testing. Accelerated testing data must cover at least six months, while intermediate and long-term stability testing must cover a minimum of twelve months.

 

 

 

 

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Storage in Refrigerators

Test Type	Storage Conditions
Long-term Testing	5°C ± 3°C
Accelerated Testing	25°C ± 2°C / 60% ± 5% RH

Storage in Freezers

Test Type	Storage Conditions
Long-term Testing	-20°C ± 5°C
Accelerated Testing	5°C ± 3°C

 

 

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Stability Testing for Formulations in Semi-Permeable Containers

For formulations containing water or solvents that may experience solvent loss, stability testing should be conducted under low relative humidity (RH) conditions when stored in semi-permeable containers. Long-term or intermediate testing should be performed for 12 months, and accelerated testing for 6 months, to demonstrate that the product can withstand low RH environments.

Test Type	Storage Conditions
Long-term Testing	25°C ± 2°C / 40% ± 5% RH or 30°C ± 2°C / 35% ± 5% RH
Accelerated Testing	40°C ± 2°C / ≤25% RH
Intermediate Testing (Note 1)	30°C ± 2°C / 35% ± 5% RH

 

Note 1: If the long-term testing condition is set at 30°C ± 2°C / 35% ± 5% RH, intermediate testing is not required.

Calculation of Water Loss Rate at 40°C

The following table provides the water loss rate ratio at 40°C under different relative humidity conditions:

Substitute RH (A)	Reference RH (R)	Water Loss Rate Ratio ([1-R]/[1-A])
60% RH	25% RH	1.9
60% RH	40% RH	1.5
65% RH	35% RH	1.9
75% RH	25% RH	3.0

Explanation: For aqueous pharmaceuticals stored in semi-permeable containers, the water loss rate at 25% RH is three times that at 75% RH.

 

 

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This document provides a comprehensive framework for conducting stability testing under various storage conditions to ensure the quality, efficacy, and safety of pharmaceutical products throughout their shelf life.

 

These experiments can be achieved through our high and low temperature humid heat test chamber, more customized requirements please contact us.

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Walk-in Temperature Test Chamber is a large laboratory that admit operator to walk in it, primarily used for environmental testing. It is commonly used for testing large parts, semi-finished products, and finished products to simulate real-world environmental temperatures, and is widely used in industries such as electrical engineering, electrical appliances, instruments, electronics, security, communication, sensors, automation, industrial control, precision machinery, etc. The Walk-in Temperature Test Chamber is equipped with a φ 50mm test hole with a plug on the side of the box. The plug material is low foaming silicone rubber, which can withstand high and low temperatures and has insulation effect. The heater adopts a porcelain frame nickel chromium wire electric heater, which has low thermal inertia and long service life. The instrument outputs a controllable pulse duty cycle PID signal, which is controlled by a solid-state relay to make the control smoother and more reliable.

Performance and characteristics of Walk-in Temperature Test Chamber:

1.It has an extremely wide temperature and humidity control range, which can meet various needs for users. By adopting a unique balanced temperature and humidity control method, a safe and precise temperature and humidity environment can be achieved. It has stable and balanced heating and humidification performance, can achieve high-precision temperature and humidity control.

2.Equipped with intelligent temperature regulators, temperature and humidity are displayed using LED digital display. The high and low temperature damp heat test chamber can be optionally equipped with a temperature and humidity recorder.

3. Automatic selection of refrigeration circuit, the automatic control device has the performance of automatically selecting and operating to the refrigeration circuit according to set value of temperature, realizing direct start of the refrigeration machine and direct cooling under high temperature conditions.

4. The inner door is equipped with a large observation window, which facilitates the observation of the test samples’ experimental status.

5. Equipped with advanced safety and protection devices - residual current circuit breaker, over temperature protector, phase loss protector, and water cut-off protector.

We can customer High and low temperature test chambers, low temperature test chambers, constant temperature and humidity test chambers, high and low temperature damp heat test chambers, high and low temperature alternating damp heat test chambers, salt spray corrosion test chambers. above test chambers can be customized according to your requirements.

Therefore, Walk-in Temperature Test Chamber is suitable for enterprises with high demand on environmental testing and operational space.

In many outdoor environments, materials can be exposed to humidity for up to 12 hours a day. Research shows that the main factor causing this outdoor humidity is dew, rather than rainwater. The Accelerated Aging Test chamber simulates the outdoor humid erosion through its unique condensation function. During the condensation cycle of the test, the water in the reservoir at the bottom   of the test chamber is heated to generate hot steam, which fills the entire test chamber. The hot steam maintains the relative humidity in the test chamber at 100% and keeps a relatively high temperature. The sample is fixed on the side wall of the test chamber, so that the test surface of the sample is exposed to the ambient air inside the test chamber. The outer side of the sample is exposed to the natural environment, which has a cooling effect, resulting in a temperature difference between the inner and outer surfaces of the sample. This temperature difference leads to the continuous generation of condensed liquid water on the test surface of the sample throughout the condensation cycle.

 

Since the exposure time to humidity during outdoor exposure can be as long as more than ten hours a day, a typical condensation cycle generally lasts for several hours. The Accelerated Aging Tester provides two methods for simulating humidity. The most widely used method is the condensation method, which is the best way to simulate outdoor humid erosion. All Accelerated Aging Tester models can run the condensation cycle. Because some application conditions also require the use of water spray to achieve the actual effect, some models can run both the condensation cycle and the water spray cycle.

For certain applications, water spray can better simulate the final usage environmental conditions. Water spray is very effective in simulating the thermal shock or mechanical erosion caused by sudden temperature changes and the scouring of rainwater. Under certain actual application conditions, for example, in the sunlight, when the accumulated heat dissipates rapidly due to a sudden shower, the temperature of the material will change sharply, resulting in thermal shock, which is a test for many materials. The water spray of the chamber can simulate thermal shock and/or stress corrosion. The spray system has 12 nozzles, with 6 nozzles on each side of the test chamber. The spray system can run for a few minutes and then be turned off. This short period of water spraying can quickly cool the sample, creating the conditions for thermal shock. 

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.