Solution to Thermal Shock Test chamber Refrigeration System Blocking
Thermal shock test chamber is generally composed of compressor, air conditioning evaporator, cooler and pipe system software. Refrigeration system blockage generally has two kinds of dirty blockage and ice blockage, and oil blockage is relatively rare.
1. Dirty and blocked
When the compressor of thermal shock test chamber is damaged, and there is waste in the refrigeration system, this waste is very easy to block in the capillary or filter device, which is called dirty plugging. Dirty blockage is because there is residue in the refrigeration system (oxygenated skin, copper chips, welding through), when it is circulated with the refrigerant system, it causes blockage at the capillary or filter device.
Dirty blockage removal method: remove the capillary tube, filter device, cooler, air conditioning evaporator with gas cutting, disassemble the carbon molecular sieve in the capillary tube and filter device, clean the cooler and air conditioning evaporator, carry out dry, vacuum packaging, welding, and fill with refrigerant.
2. Ice jam
Ice blockage is caused by water entering the refrigeration system of thermal shock test chamber. Due to its own with a certain amount of moisture, coupled with the maintenance or refrigerant in the whole process of taking time processing regulations are not tight, so that water and gas into the system software. Under the ultra-high pressure effect of the compressor, the refrigerant is changed from a liquid to a vapor state, so that the water is passed into the narrow and long capillary tubes with the refrigerant circulation system. When the moisture content of each kilogram of refrigerant exceeds 20mg, the filter device is saturated with water, and the water can not be filtered out. When the temperature of the capillary inlet and outlet is 0 ° C, the water is converted from the refrigerant and becomes ice, resulting in ice blocking.
Dirty blocking and ice blocking are divided into full and half blocked, the common fault condition is that the air conditioning evaporator is not frosting or frosting is not full, the temperature behind the cooler is high, and the hand drying filter or capillary entrance feels that the temperature is basically the same as the indoor temperature, sometimes less than the indoor temperature, and a lot of steam is sprayed out of the cutting process pipe. After the ice jam occurs, the friction resistance of the compressor exhaust pipe increases, resulting in the compressor overtemperature, the overload protector is working, and the compressor stops running. After about 25 minutes, a part of the ice jam melts, the compressor temperature decreases, the contact point of the temperature controller and the overload protector is closed, and the compressor starts the refrigerator. Therefore, the ice blockage has regularity, and the air conditioning evaporator can see regular frosting and defrosting conditions.
Construction and System Software of Two-zone Thermal Shock Test Chamber
Construction of Two-zone Thermal Shock Test Chamber:
1, Construction mode of environmental test chamber:
Environmental test chamber is composed of a high temperature test chamber located at the upper end, a low temperature test chamber located below, a freezer cabinet located at the back and a home appliance control chamber (system software) located on the right. In this way, the shell occupies a small area, compact structure, beautiful appearance design, the freezer unit is placed in a separate generator chamber body, in order to reduce the vibration and noise of the freezer unit operation on the environmental test chamber harm, in addition to the installation and maintenance of the generator set, the household appliance operation panel is placed on the right panel of the environmental test chamber to facilitate the operation of the actual operation;
2, Shell surface raw materials: cold-rolled plate, surface electrostatic powder spraying solution;
3, The shell cavity raw materials: imported stainless steel plate (SUS304);
4, Thermal insulation material: heat resistant hard plastic polyamine ester foam + foam glass plate;
5, The door: single door, equipped with double silicone rubber sealing and sealing rubber strip heating equipment, under the self-limiting temperature heating zone, to avoid the experiment essence and frost;
6, Test rack: move up and down left and right sliding type stainless steel plate test rack. The pneumatic double-effect cylinder shows a stable and symmetrical driving force. The positioning device of the test rack uses an electromagnetic field triggered limit switch;
7, Cable wire installation hole: the upper end of the test rack and the top of the high temperature test chamber is provided with a telescopic cable threading tube.
Air conditioning system software of two-zone thermal shock test chamber:
1, Gas control method: forced circulation system natural ventilation, balanced temperature control method (BTC). The method refers to the refrigeration unit in the continuous operation of the condition, the automatic control system according to the temperature point set according to the PID automatic and operational output results to manipulate the electric heater's heart output, the ultimate UI will exceed this stable balance.
2, Gas circulation system equipment: embedded central air conditioning room, air supply mode channel and stainless steel plate short-axis exhaust fan, the application of refrigeration unit and kinetic energy adjustment system software, according to the exhaust fan to carry out a reasonable heat exchanger, more than the purpose of maintaining temperature change. According to the improved air flow of the gas, the total gas flow and the working capacity of the heat exchanger with the electric heater and the surface cooler are improved.
3, Evaporative cooling method: fin type air heat exchanger.
4. Gas heating method: select nickel-chromium wire electric heater.
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.
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.
Thermal Cycling Test(TC) & Thermal Shock Test(TS)
Thermal Cycling Test(TC):
In the life cycle of the product, it may face various environmental conditions, which makes the product appear in the vulnerable part, resulting in product damage or failure, and then affect the reliability of the product.
A series of high and low temperature cycling tests are done on the temperature change at the temperature variation rate of 5~15 degrees per minute, which is not a real simulation of the actual situation. Its purpose is to apply stress to the test piece, accelerate the aging factor of the test piece, so that the test piece may cause damage to the system equipment and components under environmental factors, in order to determine whether the test piece is correctly designed or manufactured.
Common ones are:
Electrical function of the product
The lubricant deteriorates and loses lubrication
Loss of mechanical strength, resulting in cracks and cracks
The deterioration of the material causes chemical action
Scope of application:
Module/system product environment simulation test
Module/System Product Strife test
PCB/PCBA/ Solder Joint Accelerated Stress Test (ALT/AST)...
Thermal Shock Test(TS):
In the life cycle of the product, it may face various environmental conditions, which makes the product appear in the vulnerable part, resulting in product damage or failure, and then affect the reliability of the product.
High and low temperature shock tests under extremely harsh conditions on rapid temperature changes at a temperature variability of 40 degrees per minute are not truly simulated. Its purpose is to apply severe stress to the test piece to accelerate the aging factor of the test piece, so that the test piece may cause potential damage to the system equipment and components under environmental factors, in order to determine whether the test piece is correctly designed or manufactured.
Common ones are:
Electrical function of the product
The product structure is damaged or the strength is reduced
Tin cracking of components
The deterioration of the material causes chemical action
Seal damage
Machine specifications:
Temperature range: -60 ° C to +150 ° C
Recovery time: < 5 minutes
Inside dimension: 370*350*330mm (D×W×H)
Scope of application:
PCB reliability acceleration test
Accelerated life test of vehicle electric module
LED parts accelerated test...
Effects of temperature changes on products:
The coating layer of components falls off, the potting materials and sealing compounds crack, even the sealing shell cracks, and the filling materials leak, which causes the electrical performance of components to decline.
Products composed of different materials, when the temperature changes, the product is not evenly heated, resulting in product deformation, sealing products cracking, glass or glassware and optics broken;
The large temperature difference makes the surface of the product condense or frost at low temperature, evaporates or melts at high temperature, and the result of such repeated action leads to and accelerates the corrosion of the product.
Environmental effects of temperature change:
Broken glass and optical equipment.
The movable part is stuck or loose.
Structure creates separation.
Electrical changes.
Electrical or mechanical failure due to rapid condensation or freezing.
Fracture in a granular or striated manner.
Different shrinkage or expansion characteristics of different materials.
The component is deformed or broken.
Cracks in surface coatings.
Air leak in the containment compartment.
Reliability Test for Light-emitting Diodes for Communication
Communication light-emitting diode failure determination:
Provide a fixed current to compare the optical output power, and determine failure if the error is greater than 10%
Mechanical stability test:
Impact test: 5tims/axis, 1500G, 0.5ms
Vibration test: 20G, 20 ~ 2000Hz, 4min/cycle, 4cycle/axis
Liquid thermal shock test: 100℃(15sec)←→0℃(5sec)/5cycle
Solder heat resistance: 260℃/10 seconds /1 time
Solder adhesion: 250℃/5 seconds
Durability test:
Accelerated aging test: 85℃/ power (maximum rated power)/5000 hours, 10000 hours
High temperature storage: maximum rated storage temperature /2000 hours
Low temperature storage test: maximum rated storage temperature /2000 hours
Temperature cycle test: -40℃(30min)←85℃(30min), RAMP: 10/min, 500cycle
Moisture resistance test: 40℃/95%/56 days, 85℃/85%/2000 hours, sealing time
Communication diode element screening test:
Temperature screening test: 85℃/ power (maximum rated power)/96 hours screening failure determination: Compare the optical output power with the fixed current, and determine failure if the error is larger than 10%
Communication diode module screening test:
Step 1: Temperature cycle screening: -40℃(30min)←→85℃(30min), RAMP: 10/min, 20cycle, no power supply
Step 2: Temperature screening test: 85℃/ power (maximum rated power)/96 hours
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