Experimental study on the performance of compressed air refrigerating dryer
The pre-cooler of the performance of the compressed air refrigerating dryer often adopts a sleeve tube structure, and the compressed air flows in the tube, and the ambient air is blown through the fin tube through the axial flow fan to cool the high-pressure high-temperature air in the tube, thereby achieving utilization. The small energy reduces the temperature of the compressed air and reduces the load of the evaporator. The cold air regenerator uses the low temperature air cooled by the evaporator to exchange heat with the pre-cooled hot air, and the other is the compression after pre-cooling. The air temperature is further reduced, thereby reducing the thermal load of the refrigeration system; the other is to make the temperature of the compressed air outlet dried by the cold dryer to be raised to meet the requirements of the use of the evaporator heat transfer tube often adopts two structural forms, One is a piece of copper tube, the other is a light copper tube, both of which are in the form of a multi-baffle plate, and the refrigerant is in the S-shaped flow outside the compressed air.
The experiment mainly tests the parameters such as the compressed air inlet and outlet temperature, pressure dew point and evaporation pressure of the precooler and air regenerator. The experimental results are shown in Table 1. Table 1 The results of the test results of the dryer are converted to the compressor gas under standard conditions. Volume evaporator form light copper tube sleeve tube light copper tube sleeve tube ambient air temperature (°C) ambient air relative humidity RH (%) cold dryer inlet compressed air temperature (°C) pre-cooler outlet compressed air temperature ( °C) Air regenerator outlet compressed air temperature (°C) Cooling machine outlet air pressure (MPa) Cooling machine outlet air pressure dew point (°c) Refrigerant medium (R22) Evaporation pressure (MPa) according to national standards Generally, the compressed air quality grade (GB/T13277-91), the content of water vapor in compressed air is expressed by the pressure dew point. When the compressed air reaches the minimum quality level of 6, the pressure dew point is 10, then the components of the cold dryer are The performance index and cost of the dryer have a great influence. It can be seen from the experimental results that the purpose of the precooler is to reduce the temperature of the compressed air with less energy, and the temperature of the compressed air at the inlet of the dryer is small. 45C, when the air flow rate is 2.43m3/min, and the ambient temperature is about 28.5C, the compressed air is reduced by 7~9C. When the air flow rate is 5.93m3/min and the ambient temperature is about 33C, the compressed air can be reduced by 5C. On the other hand, the pre-cooler arrangement increases the flow resistance of the compressed air, and also increases the cost of the dryer. From the energy point of view, the pre-cooler must use a separate axial fan, and the motor input power must be 100~ The effect of using the pre-cooler is not ideal = therefore, the pre-cooler may not be used when the temperature of the compressed air at the inlet of the dryer is less than 45C.
/min, the regenerator can reduce the temperature of the compressed air after pre-cooling by 9~11C, and at a larger flow rate of V=5.93m3/min, the compressed air temperature can be reduced by about 8C.
The air regenerator not only raises the temperature of the air coming out of the evaporator, but also fully utilizes the cooling capacity, and does not cause the water vapor in the ambient air to condense and precipitate water droplets on the pipeline because the temperature of the wall surface of the connecting pipe is too low. The compressed air outlet temperature of the lyophilizer is recovered to meet the requirements of the application. From the experimental results, the compressed air passing through the air regenerator after pre-cooling has fallen below the ambient temperature due to the regenerator. The shell-and-tube heat exchanger structure, the low-temperature compressed air cooled by the evaporator is returned to the tube of the heat exchanger, and the pre-cooled compressed air is returned to the outside of the heat exchanger tube, and the counter-flow heat exchange is adopted, so the regenerator is dealt with More than half of the low temperature end of the barrel is covered with insulation material, instead of only the low temperature end part, the insulation method is used to evaporate the temperature and pressure. The dew point evaporator is the key evaporator in the cold dryer to ensure the pressure dew point. There must be sufficient heat transfer area and comparison. High heat transfer coefficient The pressure dew point is affected by factors such as the evaporation temperature of the evaporator and the higher the evaporation temperature, although the cooling capacity can be increased, but the pressure dew point is also Since in actual application, the user may use different amounts of gas at different times, when the amount of gas used decreases, the heat load of the evaporator through the dryer will decrease, and the minimum temperature of the compressed air passing through the dryer should be Limitation to ensure that the evaporator does not knot K. Considering the requirements of pressure dew point and heat transfer temperature difference, the evaporation temperature should be controlled. The evaporation temperature Ts is taken at the design flow rate, 6C is appropriate, and the minimum flow rate of compressed air should be guaranteed. Evaporation temperature Ts>-The automatic drainer discharges the water deposited in the evaporator out of the evaporator in time. It should be installed at the lowest point of the evaporator. In order to facilitate the flow of condensate, the evaporator should be inclined at a small angle to the drainer. However, the airflow velocity at the outlet of the evaporator compressed air is as high as 8 m/s, and the tiny water droplets entrained in the air flow to the regenerator along with the compressed air. In the regenerator, the compressed air absorbs heat with the low temperature, and the temperature rises. The tiny water droplets are re-vaporized into water vapor, which makes the pressure dew point cold. 2 Conclusion When the compressed air temperature at the inlet of the dryer is lower than 45C, Set the pre-cooler air regenerator to the low temperature end of the half cylinder position (including the low temperature end cover) should be packaged with insulation material. The evaporation temperature of the cold dryer should be controlled. The evaporation temperature can be 6C at the design flow rate; to ensure the cold dryer Safe operation, the minimum flow through the dryer should ensure that the evaporation temperature is higher than -1C. The water dryer should be equipped with a gas water separator.
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