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.
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.
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