How to cool the high and low temperature shock box

High and low temperature impact box is used for electronic and electrical components, automation components, communication components, auto parts, metals, plastics and other industries, defense industry, aerospace, ordnance industry, electronic chip IC, semiconductor ceramics and polymer materials for physical changes, Testing the repeated resistance of its materials to high and low temperatures and chemical changes or physical damage caused by thermal expansion and contraction of the product can confirm the quality of the product. From precision IC to heavy mechanical components, no one does not need it. test tools.

The temperature conversion accuracy of the high and low temperature impact box is generally set to: 0.1℃/min, and the standard range of temperature conversion time is 3-5 minutes to complete. Here is how it realizes the temperature conversion so quickly?

The refrigeration cycle adopts the reverse Karo cycle, which consists of two isothermal processes and two adiabatic processes. The main processes are:

The refrigerant is adiabatically compressed to a higher pressure by the compressor, and the work consumed increases the temperature of the exhaust gas. After that, the refrigerant exchanges heat with the surrounding medium through the condenser isothermally and transfers the heat to the surrounding medium. After the refrigerant passes through the shutoff valve adiabatic expansion to perform work, at this time the temperature of the refrigerant decreases. After the refrigerant passes through the evaporator to absorb heat isothermally from the higher temperature object, the temperature of the cooled object is lowered. This cycle repeats itself to achieve the purpose of cooling down. The refrigeration system of this test chamber adopts a unit freon refrigeration system composed of a hermetic compressor. The design of the refrigeration system and the application of energy adjustment technology can not only ensure the normal operation of the refrigeration unit, but also effectively adjust the energy consumption and refrigeration capacity of the refrigeration system to keep the refrigeration system in a good operating state. Using balance temperature adjustment (BTC), even when the refrigeration system is continuously working, the control system controls the output of the heater through the PID automatic calculation output according to the set temperature point, and finally reaches a dynamic balance.

Generally speaking, the refrigeration methods of high and low temperature shock boxes are mechanical refrigeration and auxiliary liquid nitrogen refrigeration. Mechanical refrigeration adopts vapor compression refrigeration. This refrigeration method is one of the widely used and economical refrigeration methods in artificial refrigeration. Vapor compression refrigeration types include: single-stage refrigeration, multi-stage refrigeration and cascade refrigeration, which are mainly composed of compressor, condenser, throttling mechanism and evaporator. Since the low temperature of our test must reach -55℃, single-stage refrigeration is difficult to meet the requirements, so the refrigeration method of the comprehensive test box generally adopts cascade refrigeration.

The high and low temperature impact box refrigeration system consists of two parts, called the high temperature part and the low temperature part, each of which is a relatively independent refrigeration system. The evaporation of the refrigerant in the high-temperature part absorbs 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 chamber) to obtain cold energy. The high temperature part and the low temperature part are connected by an evaporative condenser, which is both the evaporator of the high temperature part and the condenser of the low temperature part. The high-temperature part of the test chamber uses medium-temperature refrigerant, and the low-temperature part uses low-temperature refrigerant, and the temperature in the chamber can reach -70°C.

The UV lamp aging test uses fluorescent UV lamps to simulate the destructive effects of sunlight on durable materials. This is different from the aforementioned xenon arc lamp. The fluorescent ultraviolet lamp is similar in electrical principle to ordinary cold-light fluorescent lamps for lighting, but can generate more ultraviolet light instead of visible light or infrared light.

For different exposure applications, there are different types of lamps with different spectra to choose from. The lamp can simulate sunlight well in the main short-wavelength ultraviolet spectral range. The spectral energy distribution (SPD) of the UVA lamp is very similar to the spectrum obtained at 360nm in the solar spectrum. UVB lamps are also commonly used lamps for accelerated artificial weathering tests. It destroys materials faster than UVA lamps, but its energy output with a wavelength shorter than 360 nm will cause deviations from actual test results for many materials.

Although the national standard stipulates and the currently prevailing domestic aging test method is xenon arc radiation, xenon arc radiation and ultraviolet light aging tests are both widely used test methods abroad. These two methods are based on completely different principles. The xenon lamp irradiates the test chamber to imitate the entire solar spectrum, including ultraviolet light, visible light and infrared light, and its purpose is to simulate sunlight. The ultraviolet aging test does not attempt to imitate the sun's rays, but only imitates the destructive effect of the sun's rays. It is based on the principle that durable materials that are exposed outdoors for a long time will have greater aging damage caused by shortwave ultraviolet light.

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High quality vacuum furnace

The vacuum furnace eliminates the oxidation and decarburization of the workpiece surface in the heating process, and can obtain a clean surface without deterioration layer. The heating chamber of the vacuum furnace is made of high-quality heat insulation materials with heat insulation walls and barriers, which can highly concentrate the electric heating energy in the heating chamber, with remarkable energy-saving effect. The following is a professional analysis of the functions of the vacuum furnace:

Vacuum quenching (tempering, annealing) is a treatment method to achieve the expected performance by heating and cooling the material or parts in vacuum according to the process specification.

Vacuum brazing is a welding process in which a group of weldments are heated to a temperature above the melting point of the filler metal but below the melting point of the base metal in vacuum, and a weld is formed by the wetting and flowing of the filler metal to the base metal (the brazing temperature varies with different materials).

Vacuum sintering is a method of heating metal powder products in vacuum to make adjacent metal powder grains form parts by adhesion and diffusion. Vacuum magnetization is mainly used for magnetization of metal materials.