Heat Dissipation Method of Thermal Shock Test Chamber Refrigeration Unit
Generally speaking, thermal shock test chamber is divided into two refrigeration methods: air-cooled and water-cooled. The accuracy of the test results not only depends on the excellent process quality of the equipment itself, but also is closely related to the cooling efficiency of the refrigeration unit. So what factors affect the heat dissipation efficiency?
In short, the air-cooled type has the greatest impact on its heat dissipation efficiency or environmental factors. For water-cooled refrigeration units, the key factor is the water tower configured as a fixed equipment, the following is the method of improving the heat dissipation efficiency of different cooling methods.
Firstly, air-cooled thermal shock test chamber：
Reason: Because the heat dissipation of the air-cooled refrigeration unit mainly relies on the electronic fan to dissipate a large amount of heat through the fin. If the environment is very dusty, the equipment is affected by the wind, a lot of dust will adhere to the fan and fins. Although less dust does not have any effect on the air-cooled refrigeration unit, when the dust on the fins continues to increase, it will directly affect the heat dissipation effect of the air-cooled refrigeration unit, resulting in poor heat dissipation effect and the corresponding cooling capacity.
1, The user should provide a relatively clean use environment for the air-cooled refrigeration unit (smooth ventilation is the best), and try to stay away from the harm of all kinds of dust. This will extend the frequency of inefficient operation of air-cooled refrigeration units because there is more dust in the environment, and give the unit equipment a safe and stable operation environment.
2, Keep the equipment clean and tidy, and clean the fins regularly. Can be washed with wind and tap water, if the environment is harsh, the dust impurities on the fins are more oil, then rinse with tap water first, and then spray on cleaning dust, after 10 minutes or so, and then repeatedly rinse with tap water. After using the air-cooled refrigeration unit for a period of time, it is necessary to carry out a comprehensive cleaning for the environment and the machinery and equipment.
Secondly, water-cooled thermal shock test chamber：
Reason: Since most of the water tower is installed outside, it needs to withstand strong light radiation, higher temperature, and fast water evaporation, which is easy to cause insufficient water flow in the cooling water circulation, and finally cause poor cooling effect and even high pressure alarm.
1, Timely water supply.
2, Check whether the water supply valve is abnormal.
3, Check the running status of the water tower, if abnormal, it needs to be adjusted to normal state in time.
4, Clean the pipeline filter.
5, Keep the water source clean.
The main policy to improve the heat dissipation efficiency of the air-cooled thermal shock test chamber is to place the chiller outdoors, avoid direct sunlight as far as possible, and make a protective shed for the equipment if conditions exist. If it must be placed indoors, it is better to put it next to the window to maintain good ventilation, or install an air pipe to draw hot air to the outside.
The Role of High and Low Temperature Test Chamber for Electronic Component Testing
High and low temperature test chamber is used for electronic and electrical components, automation parts, communication components, automotive parts, metal, chemical materials, plastics and other industries, national defense industry, aerospace, military, BGA, PCB substrate wrench, electronic chip IC, semiconductor ceramic magnetic and polymer material physical changes. Testing the performance of its material to withstand high and low temperatures and the chemical changes or physical damage of the product in thermal expansion and contraction can confirm the quality of the product, from precision ics to heavy machinery components, will be an essential test chamber for product testing in various fields.
What can the high and low temperature test chamber do for electronic components? Electronic components are the foundation of the whole machine and may cause time - or stress-related failures during use due to their inherent defects or improper control of the manufacturing process. To ensure the reliability of the entire batch of components and meet the requirements of the entire system, you need to exclude the components that may have initial faults under operating conditions.
1. High temperature storage
The failure of electronic components is mostly caused by various physical and chemical changes in the body and surface, which are closely related to temperature. After the temperature rises, the chemical reaction speed is greatly accelerated, accelerating the failure process. The defective components can be exposed in time and eliminated.
High temperature screening is widely used in semiconductor devices, which can effectively eliminate failure mechanisms such as surface contamination, poor bonding and oxide layer defects. Generally stored at the highest junction temperature for 24 to 168 hours. High temperature screening is simple, inexpensive and can be carried out on many parts. After high temperature storage, the parameter performance of components can be stabilized and the parameter drift in use can be reduced.
2. Power test
In the screening, under the combined action of thermoelectric stress, many potential defects of the body and surface of the component can be well exposed, which is an important project of reliability screening. Various electronic components are usually refined for a few hours to 168 hours under rated power conditions. Some products, such as integrated circuits, can not arbitrarily change the conditions, but can use high temperature working mode to increase the working junction temperature to achieve a high stress state. Power refining requires special test equipment, high and low temperature test chamber, high cost, screening time should not be too long. Civilian products are usually a few hours, military high-reliability products can choose 100,168 hours, and aviation-grade components can choose 240 hours or longer.
3. Temperature cycle
Electronic products will encounter different ambient temperature conditions during use. Under the stress of thermal expansion and contraction, components with poor thermal matching performance are easy to fail. Temperature cycle screening utilizes the thermal expansion and contraction stress between extreme high temperature and extreme low temperature to effectively eliminate products with thermal performance defects. The commonly used component screening conditions are -55~125℃, 5~10 cycles.
Power refining requires special test equipment, high cost, screening time should not be too long. Civilian products are usually a few hours, military high-reliability products can choose 100,168 hours, and aviation-grade components can choose 240 hours or longer.
4. The necessity of screening components
The inherent reliability of electronic components depends on the reliability design of the product. In the manufacturing process of the product, due to human factors or fluctuations in raw materials, process conditions, and equipment conditions, the final product can not all achieve the expected inherent reliability. In every batch of finished products, there are always some products with some potential defects and weaknesses, which are characterized by early failure under certain stress conditions. The average life of early failed parts is much shorter than normal products.
Whether electronic equipment can work reliably depends on whether electronic components can work reliably. If the early failure parts are installed together with the whole machine equipment, the failure rate of the early failure of the whole machine equipment will be greatly increased, and its reliability will not meet the requirements, and it will also pay a huge price to repair.
Therefore, whether it is a military product or a civilian product, screening is an important means to ensure reliability. High and low temperature test chamber is the best choice for the environmental reliability test of electronic components.
Setting and Maintenance of Constant Temperature and Humidity Test Chamber
Constant temperature and humidity test chamber is a relatively precise test equipment. In order to ensure the smooth completion of each test process, the power supply of the connected equipment must be stable at around 380V to ensure that the compressor will not be damaged. In addition, you must ensure the personal safety of the personnel who receive the power, so please understand the specific operation methods before wiring.
Constant temperature and humidity test chamber adjust or replace the connected power supply. After checking that the voltage of the power supply to be connected is correct, connect the neutral terminal to the neutral terminal in the distribution chamber. Ensure that the neutral line is connected, otherwise it may cause the equipment of the constant temperature and humidity test chamber to fail to work normally or burn electrical components.
After confirming that the neutral wire is connected, connect the 3 ∮ wire to the three terminals under the main switch of the distribution chamber in the constant temperature and humidity test chamber, and tighten the screws. We need to connect the ground wire, which is connected in the same way as other power cables, and directly to the ground terminal of the distribution chamber. In the process of connecting each power cord, everyone must ensure that the different colors of the power cord can be correctly identified to avoid connection errors and normal testing.
Maintenance of constant temperature and humidity test chamber:
1, Clean the water circulation system: clean the water filter, replace the filter, check the operation of the pump, including the operation of the water flow switch, adjust the water circulation flow and test operation.
2, Check all electrical wiring and electrical components to ensure reliable operation and good contact.
3, Replace the fresh air filter.
4, Refrigeration system cleaning: replace the refrigeration oil, clean the oil filter.
5, Check the vulnerable parts of the refrigeration system: check the sealing condition of the compressor and connecting parts, and replace all filters.
6, Refrigeration system leakage inspection: check all the connecting parts of the refrigeration system and the connecting parts of the valve plate are leaked and tightened.
7, According to the working conditions to supplement refrigerant: check whether the need to supplement the system refrigerant to ensure effective cooling capacity.
8, Comprehensive system operation: check whether the operating components are in good condition.
Influence of Capillary Length of High and Low Temperature Test Chamber on Parameters of Refrigeration System
1. Influence on suction and exhaust temperature and pressure
With the same charge amount, the shorter the capillary, the larger the refrigerant flow rate, so the suction temperature and exhaust temperature will decrease; Similarly, when the capillary is constant, the larger the charge amount is, the larger the refrigerant flow rate is, and the suction temperature and exhaust temperature also decrease.
However, with the increase of flow, the inspiratory pressure also rises. For the exhaust pressure, the shorter the capillary is, the smaller the filling amount is. When the capillary length is constant, the higher the charge amount is, the higher it is.
2. Influence on condensing temperature and pressure
When the refrigerant charge is constant, the shorter the capillary tube is, the condensation temperature and pressure decrease.
When the capillary length is constant, the higher the charge amount, the higher the condensing temperature and pressure.
3. Influence on evaporation temperature and pressure
The shorter the capillary, the greater the evaporation temperature and pressure.
When the capillary length is constant, the higher the charge amount, the higher the evaporation temperature and pressure.
4. the influence of supercooling and superheat
When the refrigerant charge is constant, the longer the capillary is, the higher the supercooling degree and the superheat degree are.
When the capillary length is constant, the higher the charge amount, the greater the supercooling degree and the smaller the superheat degree.
5. Influence on cooling capacity, power consumption and performance coefficient EER
When the refrigerant charge is constant, the longer the capillary length, the smaller the power consumption, but the cooling capacity is also smaller, the EER is smaller.
When the charge amount increases to a certain extent, because of the influence of heat exchange temperature difference, the cooling capacity increases, and the EER also increases.
6. Design points of capillary system
(1) On the high pressure side, the reservoir is generally not used, in fact, whether the reservoir is used does not depend on what kind of throttling device, but depends on whether the operation of the entire system is needed, such as heat pump system, shutdown pump system.
(2) In the suction tube, it is best to use a gas-liquid separator.
Because when the capillary system is shut down, the high and low pressure side will balance and the evaporator will accumulate refrigerant liquid, the gas-liquid separator can prevent liquid shock and refrigerant migration.
(3) The high pressure side can accommodate all the refrigerant charged, which is to prevent the capillary blockage when the damage to the high pressure piping system and compressor.
(4) In the high load condition of the evaporator, because the capillary system can be fed back to the condenser side, the condenser should take into account whether the condensing pressure will be too high under this condition, so it is necessary to increase the condensing heat transfer area.
(5) The pipe between the condenser outlet and the capillary inlet should not accumulate refrigerant liquid.
One is that when the compressor is shut down, this part of the refrigerant liquid will evaporate because of the pressure drop, flow into the evaporator and condense, thus bringing some heat to the refrigeration space, which may have an impact on the closed space of the refrigerator, for the air conditioning, this part of the heat can be ignored;
Another is that this will delay the time of the balance of the high and low voltage side, which may cause problems when the low torque compressor starts again, which can generally be solved by increasing the delay in the control (in fact, this is also good for reducing the impact of the starting current on other electrical appliances or the grid).
(6) The capillary inlet must be filtered to prevent clogging, especially the HFC refrigerant used now, which is required to add a dryer in design.
(7) Before the refrigerant enters the capillary, it is best to have a certain degree of undercooling, which can be added to the evaporator by adding a section of undercooling tube, or generating heat exchange with the suction tube, so that the gas flash in the capillary is minimal, thereby increasing the cooling capacity and ensuring the refrigerant flow.
However, it should be noted that at low temperature conditions, the undercooling may be too large because there is a little return liquid in the suction tube, which increases the capillary flow rate, and in turn increases the undercooling degree, which may eventually cause the return liquid.
Maintenance Method of High and Low Temperature Test Chamber
There are three common types of high and low temperature test chamber controllers: software failure, system failure and hardware failure.
1, Software failure:
Software failure mainly refers to the controller failure of the high and low temperature test chamber, including the internal parameters, the control point IS control and output signal of the solenoid valve on and off.
2, System failure:
System failure refers to the initial design problems of the refrigeration system, including the leakage of refrigerant caused by high and low temperature test chamber does not cool down, and refrigerant leakage is often due to transport and high and low temperature test chamber operation jitter or refrigeration copper pipe welding process is not fine and other reasons caused.
3, Hardware failure:
Hardware failure may lead to non-cooling hardware compressor, solenoid valve and other refrigeration components.
Then the user can listen and touch to roughly understand what is the hardware high and low temperature test chamber damage, if it is a compressor failure, the compressor sound will be abnormal or do not work does not start or the compressor itself temperature is much higher than usual temperature, and the solenoid valve failure and other refrigeration components failure users are not too good to master.
In addition, the damage of the controller and the damage of the electronic parts of the control refrigeration system may also cause the phenomenon of non-cooling and non-cooling of the high and low temperature test chamber.
Scientific principle of heating and cooling of high and low temperature test chamber:
The high and low temperature test chamber has the functions of heating, cooling, humidification and dehumidification, and can detect the product's high temperature resistance, low temperature resistance and humidity resistance. How is the temperature in the high and low temperature test chamber controlled?
The heating device is the key link to control whether the high and low temperature test chamber is heated up. The controller outputs voltage to the relay when it gets the heating instruction. The high and low temperature test chamber is about 3-12 volts of direct current added to the solid state relay. The AC end of the high and low temperature test chamber is equivalent to a wire connection, and the contactor is also drawn at the same time. Heat up the constant temperature and humidity test chamber.
Cooling is an important part of the high and low temperature test chamber, which directly affects the determination of a high and low temperature and performance, including compressor, condenser, throttling device, evaporator four major components, compressor is the heart of the refrigeration system, it inhales low temperature and low pressure gas, into high temperature and high pressure gas, through condensation into a liquid to release heat, through the fan to take away heat, Therefore, the test chamber is the reason of hot air, and then become low pressure liquid through throttling, and then become low temperature and low pressure gas through the evaporator back to the compressor, the refrigerant in the evaporator to absorb the heat of the high and low temperature chamber to complete the gasification process and absorb heat, to achieve the purpose of refrigeration, to complete the high and low temperature test chamber cooling process.
High and low temperature chamber temperature and cooling rate test procedure:
In the adjustable range of the temperature of the test chamber, the lowest nominal temperature was selected as the lowest cooling temperature, and the highest nominal temperature was selected as the highest heating temperature.
Open the cold source, so that the test chamber from room temperature to the lowest cooling temperature, stable for at least 3 hours, rise to the highest heating temperature, stable for at least 3 hours and then to the lowest cooling temperature, during the heating and cooling, record once a minute, until the end of the test process.
The principle of high and low temperature test chamber heating and cooling is so, the realization of its function is completed by the setting of the control system, understanding the principle of heating and cooling, in the use of high and low temperature test chamber must be more handy.
Definition and Use of Temperature Cycling Test Chamber
Temperature cycling test chamber is a kind of laboratory equipment widely used in various industries, its main function is to cycle the product within a certain temperature range to simulate the operation of the product in different temperature environments. The equipment is an important tool to realize product reliability testing, quality control and product performance evaluation.
The temperature cycling test chamber is widely used and can be used for testing in various fields, such as aerospace, automotive, electronics, electric power, medical and other fields. In the aerospace sector, temperature cycle test chambers are used to test the performance of aircraft components at extreme temperatures to ensure their reliability in extreme environments. In the automotive field, the temperature cycle test chamber is used to test the performance of automotive components under different temperature and humidity conditions to ensure that the car can operate normally in a variety of environments. In the field of electronics and power, temperature cycling test chambers are used to test the performance and reliability of electronic equipment under different temperature conditions to ensure that the equipment can operate stably for a long time. In the medical field, temperature cycling test chambers are used to test the performance and reliability of medical equipment under different temperature and humidity conditions to ensure the normal operation of the equipment.
The working principle of the temperature cycling test chamber is to carry out the cycling test by controlling the temperature and humidity in the chamber. The device has a variety of temperature control modes, such as constant temperature control, programmed temperature control, programmed temperature control, etc., which can be selected according to needs. During the test process, the temperature cycling test chamber will place the product in different temperature environments for testing to simulate the use of the product in different environments. After the test is completed, users can improve and upgrade the product according to the test results to improve the reliability and performance of the product.
In short, the temperature cycling test chamber is a laboratory equipment widely used in various industries, and its main function is to cycle the product within a certain temperature range to simulate the operation of the product in different temperature environments. The equipment can be used for testing in various fields, such as aerospace, automotive, electronics, power, medical and other fields, and is an important tool to achieve product reliability testing, quality control and product performance evaluation.
Working Principle and Classification of Vacuum Pump in Vacuum Drying Oven
1, The working pressure of the vacuum pump should meet the limit vacuum and working pressure requirements of the vacuum equipment, and the best value of the vacuum degree of the selected vacuum pump is 133pa=-0.1 mpa. Usually, the vacuum degree of the selected pump is half to an order of magnitude higher than the vacuum degree of the vacuum equipment.
2, Correctly select the working point of the vacuum pump. Each pump has a certain operating pressure range.
3, The vacuum pump under its working pressure, should be able to discharge all the gas generated in the process of vacuum equipment.
4, Correctly combine the vacuum pump. Because the vacuum pump has selective pumping, sometimes a pump can not meet the pumping requirements, and several pumps need to be combined to complement each other to meet the pumping requirements, such as titanium sublimation pump has a high pumping speed for hydrogen, but can not pump helium, and the three-pole sputtering ion pump, (or bipolar asymmetric cathode sputtering ion pump) has a certain pumping speed for argon, the combination of the two, It will make the vacuum device get a better vacuum degree. In addition, some vacuum pumps can not work at atmospheric pressure, need pre-vacuum; Some vacuum pump outlet pressure is lower than atmospheric pressure, the need for the front pump, so it is necessary to combine the pump to use.
5, Vacuum equipment for oil pollution requirements. If the equipment is strictly required to be oil-free, a variety of non-oil pumps should be selected, such as: water ring pumps, molecular sieve adsorption pumps, sputtering ion pumps, cryogenic pumps, etc. If the requirements are not strict, you can choose to have a oil pump, plus some anti-oil pollution measures, such as cooling trap, baffle, oil trap, etc., can also meet the clean vacuum requirements, our company's vacuum drying oven selection is rotary vane oil pump, its main characteristics: large force, fast speed, high efficiency.
6, Understand the composition of the gas being pumped, whether the gas contains condensable steam, whether there is particulate dust, whether there is corrosion, etc. When selecting a vacuum pump, you need to know the gas composition, select the appropriate pump for the gas being pumped. If the gas contains steam, particles, and corrosive gases, it should be considered to install auxiliary equipment on the pump inlet line, such as condenser, dust collector, or liquid water filter.
7, What is the impact of the oil steam discharged from the vacuum pump on the environment? If the environment is not allowed to have pollution, you can choose an oil-free vacuum pump, or exhaust the oil steam to the outside.
8, Whether the vibration generated by the vacuum pump during operation has an impact on the process and the environment. If the process does not allow, should choose non-vibration pump or take anti-vibration measures.
9, The price of vacuum pump, operation and maintenance costs.
The Measuring Principle of Hygrometer in High and Low Temperature Test Chamber
Temperature and humidity is the percentage of the amount of water vapor (vapor pressure) contained in a gas (usually air) and the amount of saturated water vapor (saturated vapor pressure) in the same case as the air, expressed in RH%. Humidity long ago had a close relationship with life, but it was difficult to quantify it. The expression of humidity is humidity, relative humidity, dew point, ratio of moisture to dry gas (weight or volume), and so on.
Humidity measurement method hygrograph humidity measurement from the principle of the division of twenty or thirty. But humidity measurement is always one of the difficult problems in the world measurement field. A seemingly simple quantity value, in depth, involves quite complex physico-chemical theoretical analysis and calculation, beginners may ignore many factors that must be paid attention to in humidity measurement, thus affecting the reasonable use of sensors.
Common humidity measurement methods are: dew point method, wet and dry bulb method and electronic sensor method, dynamic method (double pressure method, double temperature method, shunt method), static method (saturated salt method, sulfuric acid method)
1, Dew point method hygrograph: is to measure the temperature when the wet air reaches saturation, is a direct result of thermodynamics, high accuracy, wide measurement range. Precision dew point instrument for measurement can reach ±0.2°C or even higher accuracy. However, the cold mirror dew-point meter with modern optoelectric principle is expensive and often used with standard humidity generators.
2, Wet and dry bulb hygrometer: this is a wet measurement method invented in the 18th century. It has a long history and is widely used. Wet and dry bulb method is an indirect method, which converts the humidity value from the wet and dry bulb equation, and this equation is conditional: that is, the wind speed near the wet bulb must reach more than 2.5m/s. The common wet and dry bulb thermometer simplifies this condition, so its accuracy is only 5~7%RH, and the wet and dry bulb does not belong to the static method, do not simply think that improving the measurement accuracy of the two thermometers is equal to improving the measurement accuracy of the hygrometer.
3, Electronic humidity sensor method hygrometer: electronic humidity sensor products and humidity measurement belong to the industry that rose in the 1990s in recent years, at home and abroad in the field of humidity sensor research and development has made great progress. Humidity sensors are developing rapidly from simple humidity sensors to integrated, intelligent, multi-parameter detection, creating favorable conditions for the development of a new generation of humidity measurement and control systems, and also raising humidity measurement technology to a new level.
4, Double pressure method, double temperature hygrometer: is based on the thermodynamic P, V, T balance principle, the balance time is longer, shunt method is based on the precise mixing of moisture and dry air. Due to the use of modern measurement and control means, these devices can be quite precise, but because of the complex equipment, expensive, time-consuming operation, mainly used as standard measurement, its measurement accuracy can reach ±2%RH or more.
5, Static method of saturated salt hygrometer: is a common method in humidity measurement, simple and easy. However, the saturated salt method has strict requirements for the balance of liquid and gas two phases, and high requirements for the stability of ambient temperature. It requires a long time to balance, and low humidity points require even longer. Especially when the humidity difference between the indoor and the bottle is large, it needs to be balanced for 6 to 8 hours each time it is opened.
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.
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 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.
Composition of Electrical Components of High and Low Temperature Test Chamber
The main parts of high and low temperature test chamber are refrigeration units, condensers, evaporators, and controllers. The main parts play a key role, so everyone pays special attention to its main parts raw materials. However, most of them ignore its auxiliary parts at this time, or feel that the role of auxiliary parts is not worth noting. Few people want to count the specific parts, so it is not clear what specific electronic components are fully used in the constant temperature and humidity test chamber.
1, Refrigeration unit:
Used to control the operation of refrigeration unit, to carry out refrigeration cycle, and there are single-phase and three-phase.
2, Fan motor:
Used to control the fan circulation steam body, heat exchanger heat conduction, and there are indoor and outdoor.
3, Electric heater equipment:
Used for heating indoor air quality quality, tubular, flocculent points.
4, Timer:
Used for automatic control system timing boot.
5, DC contactor:
Used for refrigeration unit motor breaking and connection.
6, Leakage protector power switch:
It can not only connect or disconnect the main circuit like other switches, with the effect of leakage current detection and discrimination, when the main control circuit caused by power outage or cable sheath damage, leakage protection switch power supply main switch can be connected or disconnected switch components according to the identification results. It can be combined with isolation switch and heat relay to form a full-function low-voltage switching electronic device.
7, Overtemperature protection equipment:
Its role can not be ignored, when the controller temperature is not sensitive, the implementation of the E double maintenance of the box overtemperature, when the alarm is caused, the maintenance standby, the alarm will be different with the test temperature, relative change, you can further have the role of overtemperature maintenance. The basic concept is that when the total current flow of the broken wire exceeds the limit value, the temperature of the broken wire rises and the broken wire is broken. When the heat value caused by the broken wire does not exceed its short circuit capacity, the balance between the heat value and the released heat value is guaranteed, the temperature of the broken wire cannot reach the melting temperature, it is not easy to break.
Like this kind of small electronic components, in the high and low temperature test chamber looks innocuous, but for the structure of a test chamber is also very useful, without these components, a test chamber is not used, in short, the details determine the success of failure, fine without size, in the grasp of the test chamber at the same time, more should be from its key links to grasp.
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