Cooling Mode of Condenser in High and Low Temperature Test Chamber

High and low temperature test chamber is a common temperature test equipment in environmental test equipment, which is suitable for high temperature and low temperature reliability test of industrial products. The working principle of refrigeration in the high and low temperature test chamber is that the refrigerant flows out of the condenser under high pressure, passes through the throttling mechanism (capillary, thermal expansion valve, etc.), reduces its pressure, and then enters the evaporator. When the refrigeration medium enters the evaporator, it is a two-phase mixture (liquid and gas), which evaporates and absorbs heat under low temperature conditions in the evaporator. It then enters the condenser, where heat is released and condensed into a liquid. Xenon lamp aging test chamber uses xenon lamp with long arc as light source, which can provide corresponding environmental simulation and accelerated test for scientific research, product development and quality control. The vehicle environment simulation laboratory can simulate the test environment of engine cold start, vehicle high and low temperature, wind, frost, rain, snow, vehicle emission test, etc.

According to different refrigeration media, the cooling mode of the high and low temperature test chamber condenser can be divided into three types: air cooling, water cooling and liquid nitrogen refrigeration. Their medium is refrigerant, water and liquid nitrogen. Different media correspond to different evaporation temperatures, the same medium under different evaporation pressure, evaporation temperature is not the same.

The different cooling methods of the condenser in the high and low temperature test chamber make the components of the refrigeration different. The air cooling method consists of compressor, various refrigeration accessories, condenser, oil separator and so on. The water cooling method consists of: chiller, cooling tower, freezing pump and auxiliary equipment. Liquid nitrogen is composed of: liquid nitrogen tank, pressure transmitter, pressure gauge, flow meter, level meter, ultra-low temperature solenoid valve and so on.

No matter what kind of cooling method is used in the high and low temperature test chamber condenser, high reliability and safety are the most basic requirements. Instrument test equipment of Lab Companion can provide a variety of condenser cooling methods according to customer needs.

In addition to the high and low temperature test chamber, instrument of Lab Companion also produces all kinds of temperature and humidity test chamber, constant temperature and humidity test equipment, aging chamber (ultraviolet, xenon lamp, ozone aging chamber), thermal shock test chamber, high temperature aging machine and other equipment, all the equipment is produced according to national standards and industry specifications.

Display and Heating System of Temperature and Humidity Test Chamber

The display and control interface of temperature and humidity test chamber is intuitive and clear, and the light touch selection menu is simple and easy to use, and the performance is stable and reliable. Flexible program control, to bring users stable performance, flexible control, cost-effective products. The input channel and output channel can be expanded arbitrarily. It is a test equipment for aviation, automotive, home appliances, scientific research and other fields, used to test and determine the parameters and performance of electrical, electronic and other products and materials after temperature environment changes in high temperature, low temperature, alternating temperature and humidity degree or constant test.

Product features:

1, Use CNC cutting, laser opening, mass production test chamber.

2, Spray strictly use outdoor powder, powder is not recycled once use, strong adhesion without variegation.

3, The visual window frame is made of one-time opening mold, which has a strong industrial sense.

4, The instrument panel made of one-time mold is beautiful and generous. The label on the instrument panel uses PVC stickers and the back glue uses 3M glue.

5, The caster adopts the free adjustment height caster made by Qidong Baiyun Electronics original factory, non-market counterfeit products, high quality, beautiful and generous.

6, All the standard drawings of the refrigeration system are welded to ensure that the piping of each equipment is consistent, and the refrigeration performance has reached the appropriate state.

7, Wiring of all the standard drawings of the electrical system, thirteen inspection processes after the completion of wiring to ensure accurate wiring and no trouble.

8, The water system uses three cups to control the water level to ensure that the humidifier water supply is separated from the wet bulb water level. The temperature fluctuation caused by humidifier water is avoided.

Display:

1, The original brand temperature and humidity meter, 5.7-inch high-definition true color LCD touch screen.

2, Real-time monitoring (monitoring controller real-time data, signal point status, actual output status).

3, The controller can store the historical data within 600 days (when the temperature and humidity data are recorded at the same time at a recording interval of more than 1 minute in 24-hour operation), and can play back the uploaded historical data curve.

4, The exported files can be viewed on the computer or converted into EXCEL format by random gift software.

5, Instrument equipped with RS232/485 port.

6, With automatic calculation function, the temperature and humidity change conditions can be corrected immediately, so that the temperature and humidity control is more safe and stable.

Heating system:

1, The use of far infrared nickel alloy high-speed heating (2KW×2) electric heater;

2, High temperature independent system, does not affect low temperature test, high temperature test and alternating temperature and humidity;

3, Temperature and humidity control output power is calculated by microcomputer to achieve high precision and high efficiency.

Efficacy of Electronic Expansion Valve in High and Low Temperature Test Chamber

The electronic expansion valve of the high and low temperature test chamber adjusts the water supply rate of the air conditioning evaporator according to the preset program flow, which is called the electronic expansion valve because it belongs to the electronic adjustment mode. It integrates the development trend of refrigeration mechatronics, with the unparalleled characteristics of the expansion valve, and presents the standard for the intelligent system operation of the refrigeration system of the quotation of the high and low temperature test chamber. It is a kind of automatic control environmental protection and energy-saving components with great development prospects, and is the orientation of the development trend of the quotation of the high and low temperature test chamber in the future.

The main purpose of the electronic expansion valve and the hot air conditioning expansion valve is basically the same, and the structure is various, but in the characteristics, the two have great differences. From the perspective of control and maintenance, the electronic expansion valve is composed of three parts: control board, electric actuator and controller. Generally speaking, most of the electronic expansion valve only refers to the electric actuator, that is, the controllable drive equipment and the oil circuit board. In fact, only this part is unable to operate.

The key hardware configuration of the electronic expansion valve control board is designed by single chip microcomputer, such as the control board also needs to operate the DC frequency conversion of the refrigeration compressor and the centrifugal fan, and the method of multi-machine cascade is generally selected. The controller of the electronic expansion valve generally uses thermal resistance or thermal resistance. As a new type of hydraulic control system, electronic expansion valve has been early to improve the definition of throttle organization, which is the key step of the intelligent system of refrigeration system, is the key way and ensure that the refrigeration system is upgraded enough to truly maintain, is a representative of the mechanical and electrical engineering of refrigeration system, has been used in more and more industries. Because of the selection of electronic expansion valves, the awareness of a certain type of system submission to expansion valves existing in the whole process of the refrigeration unit design scheme has been enhanced, and the new pattern of air conditioning expansion valves for system improvement services has played a key role in the development trend of the refrigeration manufacturing industry.

The high and low temperature test chamber can complete the test process according to the pre-set curve, and can accurately control the temperature rate within the range of the heating rate capacity, and can control the heating and cooling rate according to the slope of the set curve.

Temperature control is a heating process, high and low temperature test chamber heating using independent heating, far infrared nickel-chromium alloy high-speed heating wire, P.I.D+S.R system co-channel coordinated temperature control, through microcomputer calculation of output power, to obtain high-precision, high-efficiency electricity benefits. In order to achieve rapid heating and high temperature, the method of increasing the number of heating wires and improving the temperature control performance of software is generally adopted. By using international brand compressors and circulating fans, the chamber has uniform temperature distribution, high efficiency for environment-friendly refrigerant, low energy consumption and saved energy. The use of energy regulation technology in the design of refrigeration system can not only ensure the normal operation of the unit, but also effectively adjust the energy consumption and cooling capacity, so that the refrigeration system is in a good running state.

High and Low Temperature Test Chamber Requirements Specified in the Standard

The test chamber requirements formulated according to relevant standards should meet the following two points:

1. The temperature and humidity in the high and low temperature test chamber are monitored by the sensor installed in the working space. For the test of the heat dissipation test sample, the installation position of the sensor is formulated in the GB/T2421-1999 standard.

2, The temperature and relative humidity of the working space are required to be constant within the nominal value and its specified tolerance range, and the influence of the test sample should also be considered during the test.

Heat dissipation test sample test:

The volume of the high and low temperature test chamber should be at least 5 times the total volume of the test sample, the distance between the test sample and the internal wall of the test chamber should be selected according to the provisions of GB/T2423.2-2001 Appendix A (standard appendix), the wind speed in the chamber should not exceed 1M/S, and the structure of the mounting frame or support frame of the test chamber sample should simulate the real conditions in use as much as possible. Or otherwise, the effect of the sample mounting rack on the exchange of heat and moisture between the test sample and the surrounding space should be reduced to a minimum, and the relevant specifications may also specify dedicated mounting racks.

Test severity level:

The severity grade of the test chamber consists of the test temperature, relative humidity and test time, and is specified by the relevant specifications. The combination of temperature and relative humidity can be selected from the following values:

a, 30℃±2℃ 93%±3%

b, 30℃±2℃ 85%±3%

c, 40℃±2℃ 93%±3%

d, 40℃±2℃ 85%±3%

During the test, the test chamber shall be at the temperature and humidity of the laboratory, and the test sample at the ambient temperature of the laboratory shall be placed in the normal position or other specified position in the laboratory in an unpacked, unenergized, "ready for use" state, under certain circumstances (e.g. The relevant specifications may allow the test sample to be directly sent into the test chamber under the treated test conditions, but the test sample must be prevented from producing condensation, the temperature in the test chamber should be adjusted to a predetermined severity level, the time should ensure that the test sample reaches temperature stability, the test time should be calculated from the specified conditions, if the relevant specifications require, the test sample can be energized or worked in the conditional test phase, and the relevant specifications should specify the working conditions and working time or cycle of the test sample during the test. At the end of the conditional test, the test sample should still be left in the test chamber and the chamber should be adjusted to the standard atmospheric conditions of the test. The relative humidity should be reduced first, and the time should not exceed 2 hours. The temperature change rate in the test chamber should not exceed 1℃/min on average within 5min, and the relative humidity during temperature regulation should not exceed 75%. After the conditional test, the test sample should enter the recovery procedure.

High and Low Temperature Test Standard for PC Plastic Material 

First, high temperature test

After being placed at 80±2°C for 4 hours and at normal temperature for 2 hours, the dimensions, insulation resistance, voltage resistance, key function, and loop resistance should meet normal requirements, and the appearance should not be deformed, warped, or degumming. Key bumps collapsing at high temperatures and reduced pressing force are not evaluated.

Second, low temperature test

After being placed at -30±2℃ for 4 hours and at normal temperature for 2 hours, the dimensions, insulation resistance, voltage resistance, key function, and loop resistance should meet normal requirements, and the appearance should not be deformed, warped, or degumming. 

Third, temperature cycling test

After being placed in 70±2℃ for 30 minutes, remove at room temperature for 5 minutes; then after being placed in -20±2℃ for 30 minutes, remove at room temperature for 5 minutes. After such 5 cycles, the dimensions, insulation resistance, voltage resistance, key function, and loop resistance should meet normal requirements, and the appearance should not be deformed, warped, or degumming. Key bumps collapsing at high temperatures and reduced pressing force are not evaluated.

Fourth, heat resistance

After being placed in an environment with a temperature of 40±2℃ and a relative humidity of 93±2%RH for 48 hours, the dimensions, insulation resistance, voltage resistance, key function, and loop resistance should meet normal requirements, and the appearance should not be deformed, warped, or degumming. Key bumps collapsing at high temperatures and reduced pressing force are not evaluated.

High Pressure Failure Caused by Water Cooling Unit of High and Low Temperature Test Chamber

1, High and low temperature test chamber refrigerant charging too much. Such a thing is usually produced after the overhaul, mainly manifested as the suction and exhaust pipe working pressure, balanced working pressure are high, refrigeration compressor operation current is also high.

Solution: Air should be released under the rated load according to the working pressure and balanced working pressure of the suction and exhaust pipe and its operating current until normal.

2, The water cooling temperature of the high and low temperature test chamber is too high, and the actual condensation effect is poor. The cooling water rated load of the refrigeration unit is 40~45'C, the temperature is high, and the heat pipe is not good at heat dissipation, which must cause high condensing pressure, and this phenomenon is therefore generated in the high temperature season.

Solution: The reason for the high temperature will be: the common faults of the closed cooling tower, such as the centrifugal fan is not turned on so that the water distributor does not turn, mainly manifested in the high temperature of the cooling circulating water and the rapid rise; The average external temperature is high, the waterway is short, and the water flow of the circulating system is small, so the cooling circulating water temperature is usually maintained at a high level, and the method of upgrading the storage pool can be treated.

3, The water cooling of the high and low temperature test chamber is not enough, and the water yield cannot reach the rated value. The specific performance is that the difference of water pressure in and out of the generator set is reduced (compared with the pressure difference at the beginning of the operation of the system software fund), and the temperature difference is increased.

Solution: The reason for the insufficient water output is that the system software has less water or gas. The solution is to install an automatic exhaust valve in the upper air of the pipeline to develop the exhaust pipe; The pipeline filter is blocked or used too thin, the water permeability working capacity is limited, should use a suitable filter device and clear the q filter screen every quarter; The centrifugal pump is small and does not match the system software.

4, High and low temperature test chamber cooler fouling or blocking. Condensate water is usually used in drinking water, at about 40°C is very easy to accumulate scale, and because the closed cooling tower is vertical, it is immediately exposed to the gas, dirt and dirty things are very easy to enter the cooling system, resulting in the cooler dirty blocked, the total heat transfer area is small, low efficiency, and also harm the water output. Its main performance is that the generator set inlet and outlet water pressure difference, the temperature difference increases, the temperature of the hand cooler is very high, and the copper pipe of the cooler exhaust air conditioning is hot.

Solution: Reverse cleaning of the generator set should be carried out every quarter, and chemical cleaning scale cleaning should be carried out if necessary.

How to Change the Refrigerant Oil of Thermal Shock Test Chamber?

Thermal shock test chamber is a necessary test equipment for metal, plastic, rubber, electronics and other material industries, used to test material structure or composite materials, in an instant under the continuous environment of extremely high temperature and extremely low temperature to endure the degree of chemical changes or physical damage caused by thermal expansion and contraction of the sample in the shortest time. Thermal shock test chamberr meets the test method: GB/T2423.1.2, GB/T10592-2008, GJB150.3 thermal shock test.

In thermal shock test chamber, if the compressor is semi-closed piston compressor in operation for 500 hours, it is necessary to observe the oil temperature and oil pressure changes of the frozen oil, and if the frozen oil is discolored, it must be replaced. After the initial operation of the compressor unit for 2000 hours, the cumulative operation of three years or the operation time of more than 10,000 to 12,000 hours should be maintained within a time limit and the chilled oil should be replaced.

The refrigerated oil replacement of the semi-closed piston compressor in thermal shock test chamber can be performed according to the following steps:

1, Close high pressure exhaust and low pressure suction stop valve of thermal shock test chamber, and then screw down the oil plug, the oil plug is generally in the bottom of the crankcase, and then put the frozen oil clean and clean the filter.

2, Use the low-pressure impact gas valve needle to blow nitrogen into the oil port and then use the pressure to discharge the residual oil in the body, install a clean filter and tighten the oil plug.

3. Connect the low pressure tube filled with fluorine gauge to the low pressure process valve needle with a vacuum pump to pump the crankcase into negative pressure, and then remove the other fluorine tube separately, put one end into the chilled oil, and put the other end on the valve needle of the low pressure suction of the oil pump. The chilled oil is sucked into the crankcase due to the negative pressure, and add it to the position slightly higher than the lower limit of the oil mirror line.

4. After injection, tighten the process column or remove the fluorine filling tube, and then connect the fluorine pressure gauge to vacuum the compressor.

5. After vacuuming, it is necessary to open the high and low pressure stop valve of the compressor to check whether the refrigerant has leaked.

6, Open thermal shock test chamber unit to check the lubrication of the compressor and the oil level of the oil mirror, the oil level can not be less than a quarter of the mirror.

The above is how to replace the refrigerant oil of the semi-closed piston compressor in thermal shock test chamber. Because the refrigerant oil has hygroscope, the replacement process needs to reduce the air entering the system and the oil storage container. If the cold aging oil is injected too much, there is the risk of liquid shock.

How to Control the Uniformity of Temperature and Humidity When the High and Low Temperature Test Chamber is Loaded?

High and low temperature test chamber "load" refers to the weight of our test product, or the product needs to be energized to test its heat is referred to the load. The "load" in the high and low temperature chamber is divided into non-heating load and heating load, and the test product that is not powered on or powered on is called non-heating load. This load has no effect on the temperature and humidity range of the constant temperature and humidity test chamber as a whole, but only affects the time of rising and cooling or rising and falling humidity. The test product that needs to be powered on and emits heat is a heating load, which has a relatively large impact on temperature and humidity, and the load that different temperature points or humidity points can withstand is not the same.

It is very important to select the appropriate test equipment when the product is undergoing temperature test.

1, The test range must be required to meet the product failure possibility test range, that is, whether it is a high temperature chamber or a low temperature chamber or a temperature and humidity test chamber or a thermal shock test chamber should be able to meet the extreme temperature conditions specified in the test requirements.

2, Ensure the volume of the test sample, it should not be greater than the working volume of the test equipment 1/5 of the principle standard to select the test equipment.

3, In order to ensure the uniformity of temperature in the test area, the convection mode of the test chamber is customized according to the heating power of the sample. The natural convection of hot air is used, which is especially suitable for drying powder, and most of the test equipment adopts the forced circulation of hot air. The difference in the temperature distribution of the equipment has a great impact on the test results. When a large sample is used, or the number of samples tested at the same time is large, the test results will vary greatly with the different locations, so the temperature uniformity of the equipment should be selected as best as possible. The uniformity performance of the high and low temperature alternating and humidity test chamber of the macro exhibition instrument can reach ≤0.5°C.

4, To prevent the sample heat absorption or heat release caused by heat radiation or heat load in the test area, the heating or refrigeration system device of the equipment has no effect on the temperature equalization and cooling rate of the sample during the test.

We can not be empty when using the high and low temperature test chamber, we will more or less place the test sample, and the user - generally after the test sample put into the heat is not too much concept, in order to avoid the temperature can not reach, can not fall down or rise and cool slowly this kind of situation, so we recommend that when purchasing equipment, to its heat requirements, or place the material, weight, size of the sample to tell the manufacturer, which will effectively help the test to make the test effect better.

Introduction and Comparison of Thermocouple Temperature Sensing Lines

Instructions:

The background principle of thermocouple is "seebeck effect", also known as the thermoelectric effect, the phenomenon is that when two different metal endpoints are connected to form a closed loop, and if there is a temperature difference between the two endpoints, then there will be current generated between the loops, and the higher temperature contact in the loop is called "hot junction". This point is usually placed at the temperature measurement; The lower end of the temperature is called "cold junction", that is, the output end of the thermocouple, whose output signal is: DC voltage is converted into a digital signal through the A/D converter and converted into the actual temperature value through the softwares algorithm. 

Various electric heating couples and their range of use(ASTM E 230 T/C):

type E	type J	type K
-100℃ to1000℃±0.5℃	0℃ to760℃±0.1℃	0℃ to1370℃±0.7℃
棕色(外皮颜色)+紫色-红色	棕色(外皮颜色)+白色-红色	棕色(外皮颜色)+黄色-红色

JIS,ANSI(ASTM) thermoelectric coupling appearance identification:

热电耦	JIS	ANSI(ASTM)
外皮	正端	负端	外皮	正端	负端
B type	灰	红	白	灰	灰	红
R,S type	棕	红	白	绿	棕	红
K,W,V type	青	红	白	黄	黄	红
E type	紫	红	白	紫	紫	红
J type	黄	红	白	棕	白	红
T type	茶	红	白	青	青	红

Note:

1.ASTM, ANSI: American standard

2.JIS: Japanese standard

Lighting Installation Position of High and Low Temperature Test Chamber

According to the different needs of users, the installation position of the lamp in the high and low temperature laboratory is different. The constant temperature and humidity test chamber tests the heat resistance, cold resistance, dry resistance and moisture resistance of various materials. Suitable for electronic, electrical, food, vehicle, metal, chemical, building materials and other industries of quality control. This series of products is suitable for aerospace products, information electronic instruments, materials, electrical, electronic products, various electronic components in high and low temperature or temperature and humidity environment, to test its various performance indicators.

The most common temperature test equipment in environmental test equipment, and similar related products are high and low temperature alternating test chamber, constant temperature and humidity test chamber, high and low temperature and humidity alternating test chamber and so on. It is suitable for high temperature and low temperature reliability test of industrial products. Walk-in high and low temperature test chamber, walk-in high and low temperature test chamber is used for thermal test of national defense industry, aerospace industry, automatic components, automotive parts, electronic and electrical parts, plastics, chemical, pharmaceutical industry and related products. It provides large parts, semi-finished products, and large temperature and humidity test environment space for finished products. It is suitable for the test equipment with large quantity and volume.

Some are installed on the interal chamber or door, and some are not installed. Where is the best place to install light bulbs?

In fact, the high and low temperature test chamber lighting has advantages and disadvantages no matter where it is installed.

If the lighting is installed in the broadcast room, you can clearly see the condition of the entire broadcast room and observe the product at any time.

The lamp is installed on the door, and when the user conducts the double 85 test or the high temperature and high humidity test, the humidity is not easy to invade the lamp, and the lamp is not easy to damage, which can greatly reduce the after-sales service fee. However, its observation field is very small, can only observe the near attractions, customers observe the product is not very convenient.

If the lamp is installed on the right side of the internal chamber, it is recommended to be completely sealed to prevent moisture intrusion to ensure the long-term stable operation of the lamp. If it is installed on a door, it is recommended that the viewing window be trapezoid, so that you can have a wider field of view.

Of course, some corporate customers choose not to install lighting when purchasing high and low temperature test chambers to reduce production costs and later management costs. However, customers can not observe products at any time when doing tests, and they can not meet the needs of different customers who want to observe products.