Ventilation aging test chamber, also known as air thermal aging test chamber, is a special environmental test equipment that simulates the impact of high temperature conditions on material properties in the atmospheric environment. Its core function is to keep the air in the box fresh through forced ventilation, providing a high-temperature environment containing a constant concentration of oxygen for the specimen, so as to accelerate the hot oxygen aging process of the material. The test chamber evaluates the aging resistance characteristics of materials by assessing and judging the physical properties of materials after aging in air under simulated high temperature and atmospheric pressure, and comparing the test results with the performance of unaged specimens. This equipment is widely used in scientific research units, industrial and mining enterprises, and laboratories of colleges and universities, especially for thermal aging tests of polymer materials and their products such as electrical insulation materials, rubber, plastics, etc.
Core working principle
The working principle of the ventilated aging chamber is based on the thermooxygen aging mechanism, that is, in a high-temperature environment, the material undergoes an oxidative reaction with oxygen in the air, resulting in molecular chain breakage or cross-linking, resulting in gradual deterioration of material properties. The equipment adopts the balanced temperature control method to achieve precise temperature control, and its working process mainly includes the following key links:
Inside the cabinet, a highly efficient hot air circulation system consists of a fan that can operate continuously at high temperatures and a specially designed air duct. The fan drives the air flow, allowing the heat generated by the heating element to be quickly and evenly distributed inside the studio, ensuring consistent temperature at all points. The test chamber is equipped with an independent ventilation system, which realizes the quantitative exchange of internal air and external fresh air through the opening and closing control of the air inlet and exhaust port. This process not only replenishes the oxygen required for material aging, but also discharges volatile by-products that may be generated during the aging process out of the chamber to maintain the stability of the test environment. The control system adopts the PID automatic calculation function, monitors the temperature change in the box in real time through the temperature sensor, and automatically adjusts the output power of the heater according to the difference between the set value and the measured value, and finally makes the temperature in the box reach and stabilize at the set target value, forming a dynamic thermal equilibrium state.
Key measurement methods and parameters
The performance verification of ventilated aging test chamber involves the measurement of a number of key parameters, among which air exchange is one of the core indicators. According to relevant standards (e.g. JB/T7444-94), the air change is usually tested using the standard energy meter method:
1. Power Consumption Measurement in Sealed State:First, seal all ventilation holes, door cracks and gaps around the blower, and control the temperature of the studio at 80±2°C above the ambient temperature. After the temperature stabilizes for 2 hours, the electrical energy consumed by the test chamber within 30 minutes is measured and converted to the average power P₁.
2. Power consumption measurement in the open state:Remove all seals, open vents and vents, and measure the energy consumed in 30 minutes again under the same temperature conditions, converted to average power P₂.
3. Air Change Calculation:According to the power difference, chamber volume, ambient air density and temperature difference of the two measurements, the air exchange volume is calculated as follows:
N = 3590 × (P₁ - P₂) / (V × d × ΔT)
Where:
N - air exchange, times/hour;
P₁ – the average electrical power consumed during sealing, W;
P₂ – the average electrical power consumed when turned on, W;
ΔT - the difference between the arithmetic mean of the temperature inside the box and the ambient temperature, °C;
V – studio volume, L;
d – air density at ambient temperature, g/L.
In addition to air exchange, other key measurement parameters include temperature fluctuations (typically ≤± 0.5°C), temperature uniformity (typically ≤± 2°C), and temperature rise rates. These parameters together constitute a comprehensive index system for evaluating equipment performance.
Main influencing factors
The accuracy and reproducibility of ventilation aging test results are restricted by many factors, and the following aspects should be focused on when operating and interpreting the results:
1. Air Change and Airflow Pattern:The size of the air exchange directly determines the oxygen replenishment rate and the discharge efficiency of aging products in the box. Excessive air exchange may lead to increased heat loss and increased temperature fluctuations. If the air exchange volume is too small, the oxygen supply may be insufficient, and the aging process in the atmospheric environment cannot be realistically simulated. There are significant differences in the heat transfer and gas exchange effects of forced convection and natural convection on the surface heat transfer and gas exchange of the specimens. The standard stipulates that forced convection air change is usually divided into two adjustable ranges: up to 100 times/hour and 100 to 200 times/hour; the natural convection type is up to 50 times/hour.
2. Uniformity in Temperature Distribution:Temperature uniformity in the working room is a prerequisite for ensuring that specimens in different positions are subjected to the same thermal stress. Air duct design, fan performance, and sample placement will all affect the temperature field distribution. The sample volume should not exceed the appropriate proportion of the effective volume of the working room during the test, and sufficient gaps should be left between the samples to avoid mutual occlusion and affect the airflow circulation.
3. Specimen status and installation method:Many ventilated aging chambers are equipped with a low-speed rotating specimen turntable, which is usually adjustable from 1 to 10 rpm. The rotation of the turntable allows the specimen to constantly change the direction relative to the air flow during the test, which helps to reduce the test error caused by the small uneven temperature field. The shape, thickness, and hanging or placement of the specimen also affect its heat exchange efficiency with hot air.
4. Environmental Conditions:The ambient temperature, humidity, and atmospheric pressure around the test chamber can affect the heating efficiency and ventilation of the equipment. The standard requires an ambient temperature of 5 to 40°C, relative humidity less than 85% R.H, and atmospheric pressure in the range of 86 to 106 Kpa. The fluctuation of ambient temperature will directly affect the measurement accuracy of ΔT, which in turn will affect the calculation of air change.
Typical application areas
The application of ventilated aging chambers has penetrated into several industrial fields where the thermal aging properties of materials need to be evaluated:
Electrical Insulation:Electrical insulation components such as wires and cables, insulation sleeves, and motor windings are in a high temperature state due to current thermal effects during long-term operation. The ventilated aging test is used to evaluate the service life and insulation performance retention ability of these materials in high-temperature environments, and meets the requirements of GB/T 3512, IEC540 and other standards.
Rubber and polymer materials:Polymer products such as rubber seals, conveyor belts, tires, and plastic pipes will gradually harden, crack or lose their elasticity due to the action of heat and oxygen in actual use. By accelerating the aging test, the life of the material under conventional use conditions can be predicted, providing a basis for material formulation improvement and product quality control.
Electronic Components & Plasticized Products:Electronic components, circuit board coatings, connector housings, and other products may experience performance drift or structural changes when stored or operated in high-temperature environments. Aging tests are used to assess its adaptability in simulated use environments.
Wire and cable industry:When wire products are heated, the insulation layer and covering material will undergo varying degrees of aging. This test chamber is specially designed with an air exchange adjustment device, which can simulate the aging environment of the wire under the actual power generation and heat generation to evaluate its safety and durability.
Scientific research and quality supervision:The scientific research unit uses the equipment to study the heat resistance characteristics of new materials; The quality supervision and inspection department is used to conduct sampling and certification tests on the aging resistance of various products on the market.
Selection points to consider
When selecting suitable ventilation aging test equipment for laboratories or quality inspection departments, it is necessary to make comprehensive judgments based on technical needs, standards and specifications, and practical application scenarios:
1. Tested standards met:Clarifying the test standards that the product needs to meet is the primary basis for selection. Common standards include GB/T 3512 (Accelerated Aging and Heat Resistance Test for Vulcanized Rubber or Thermoplastic Rubber), JB/T 7444 (Air Thermal Aging Test Chamber), UL 1581 (Wire and Cable Reference Standard), and IEC 60216 (Heat Resistance of Electrical Insulation Materials). Different standards have differences in temperature range, air exchange requirements, specimen rack form, etc., and the capacity of the equipment needs to cover these requirements.
2. Temperature Range and Control Accuracy:The maximum operating temperature required is determined depending on the type of material being tested, with common temperatures ranging from +10°C to 200°C, 250°C, or 300°C at room temperature. At the same time, the temperature fluctuation (≤±0.5°C) and uniformity (≤±2°C) of the equipment are paid attention to, which directly affect the reliability of the test results.
3. Range and method of air exchange adjustment:The aging test of different materials has specific requirements for air exchange. When selecting, it should be confirmed whether the air change volume of the equipment is adjustable and whether the adjustment range covers the required value (e.g. 1 to 100 times/hour or wider). At the same time, pay attention to whether the ventilation control method is manually adjusted or automatically controlled by the instrument.
4. Workshop size and specimen rack form:The effective volume of the device needs to match the size and number of samples being tested. Also consider the form of the specimen rack: the turntable type sample rack helps to improve temperature uniformity, suitable for hanging or placing multiple small samples; Shelf-style sample racks are suitable for large or irregular samples. Whether the turntable speed is adjustable is also a functional point that needs to be paid attention to.
5. Ease of operation and safety protection:Observation windows and lighting facilitate real-time monitoring of the test process; Programmable controllers enable the automatic operation of complex test programs. Complete safety protection measures are crucial, including over-temperature protection, motor overload protection, phase reverse phase protection, leakage protection and other functions to ensure the safety and reliability of the test process.
6. Confirmation of Prohibited Test Items:Before selection and use, it must be clear that the test chamber cannot be used to test flammable, explosive and volatile flammable and explosive substances, including all kinds of explosives, spontaneous combustibles, peroxides, and flammable liquids and gases. Violation of this regulation may lead to serious safety accidents.