The throttling short pipe is installed between the condenser and the evaporator, and functions to throttle and depressurize the high pressure liquid refrigerant to ensure a pressure difference between the condenser and the evaporator, so that the liquid refrigerant in the evaporator The heat absorption can be evaporated at the required low pressure.
The high-pressure and medium-temperature liquid refrigerant from the condenser is filtered through the inlet filter and then enters a fixed small-diameter bronze tube, which is throttled and depressurized under the action of the copper tube to make it a low-temperature, low-pressure gas-liquid mixture. After exiting the filter, it enters the evaporator to meet the needs of evaporation.
In summary, the structural characteristics of the throttling short tube air conditioning refrigeration system can be summarized as follows: 1 The fixed throttle is adopted to avoid the fault of inaccurate opening control.
2 The gas-liquid separator is arranged on the low-pressure pipeline, and the liquid-storage dryer on the high-pressure liquid pipeline is eliminated. In addition to the same function as the liquid storage dryer, the liquid refrigerant can be prevented from entering the compressor.
3 Parallel flow condenser and stacked evaporator are adopted, which improves the heat exchange capacity by 10%~15% compared with the traditional heat exchange device.
1.2 Working principle The throttling short tube refrigeration system is a non-independent refrigeration system. The engine is driven by a belt and the electromagnetic clutch is used to control the operation of the compressor. When cooling is required, the electromagnetic clutch is closed and the refrigeration system starts to work: the compressor compresses the sucked low-temperature and low-pressure gaseous refrigerant into high-temperature, high-pressure gas and sends it to the condenser for heat dissipation to make it a medium-temperature, high-pressure liquid. Refrigerant; then throttling and depressurizing under the action of the throttling short tube, and atomizing into a gas-liquid mixture, entering the evaporator and performing endothermic evaporation; evaporating low-temperature, low-pressure gaseous refrigerant passing through the gas-liquid separator The water and impurities are filtered out, and some of the liquid refrigerant that has not evaporated can be completely converted into a gaseous state by the action of the gas-liquid separator; finally, all the evaporated refrigerant starts to be in the next cycle under the action of the compressor. Since the air around the evaporator is cooled, cold air is blown into the passenger compartment by the blower, thereby achieving the purpose of cooling.
Maintenance of 2 throttling short tube refrigeration system 2.1 Basic inspection Whether the throttling short tube refrigeration system works normally can be judged by the following methods.
2.1.1 Listen to the sound of the compressor suction when the refrigeration system is turned on (the clutchless variable displacement compressor can not use this method), whether there is abnormal noise at the compressor, so as to judge whether the compressor works normally.
2.1.2 Look 1) After the compressor is working, make the engine speed reach 1 500 r/min and continue to run for 2 to 3 minutes; the air-conditioning switch and blower switch are adjusted to the maximum. Observe the flow state of the refrigerant through the observation hole on the high-pressure liquid pipeline. The normal condition should be clear and transparent, and there are a small number of bubbles during acceleration and deceleration.
2) Look at the system pipe connection for oil stains. If there is oil, the system has a leak.
2.1.3 After touching the system for a period of time, feel the following temperatures by hand: 1 the inlet temperature of the condenser is 70-90 ° C, the outlet temperature is 50-60 ° C; 2 the outlet temperature of the evaporator is 1 ~ 5 ° C, There is a slight frosting.
2.1.4 After measuring the compressor operation, the engine speed is up to 1 500 r/min, and continuous operation for 2 to 3 minutes; the air-conditioning switch and the blower switch are adjusted to the maximum; when the ambient temperature is 30-35 ° C, the R134a system is measured. The pressure value obtained should be in accordance with the low pressure of 0.2 to 0.35 MPa and the high pressure of 1.5 to 2.0 MPa, otherwise it is abnormal (the system pressure will change with the change of the ambient temperature).
2.2 Maintenance operations 2.2.1 Recycling When it is confirmed that the refrigeration system needs maintenance, the refrigerant should be recovered first. The refrigerant in the system is generally extracted by the recovery machine, dried, filtered, and pressed into a dedicated recovery tank.
2.2.2 Leakage in the refrigeration system (abnormal leakage exceeds 150 g / year / vehicle), or after the system has been repaired, it is necessary to perform leak detection. The method is as follows (take the pressure leak detection method as an example): 1 connect the high pressure end of the pressure gauge group to the system, and connect the intermediate maintenance hose to the gas source; 2 open the high pressure manual valve and send the dried gas source into the system to Increase the pressure of the system; 3 When the pressure reaches 1.5~2.0 MPa, stop the pressure, close the high pressure end manual valve and gas source of the pressure gauge group; 4 Apply the soapy water film to each joint of the pipeline (the oil stain is mainly checked). Observe whether there is bubble generation. If there is air bubble, it indicates that there is leakage; at the same time, observe whether the pressure value is decreased; 5, after the end of the leak detection, the pressure in the system is released, and the manual valve opening degree is small to prevent the refrigeration oil from being discharged.
2.2.3 Evacuation The purpose of this step is to extract the air and moisture in the system to avoid affecting the cooling effect. The method is as follows: 1. Connect the high and low pressure ends of the pressure gauge group to the system, and connect the intermediate maintenance hose to the evacuator; 2 Open the high and low pressure manual valves, turn on the power of the pumping machine, and the system starts to take the air; 3 evacuate for 5 to 10 minutes, the system vacuum should reach 97.3 kPa, otherwise there is leakage; 4 the general displacement refrigeration system takes about 30 minutes. After the evacuation is finished, close the high and low pressure manual valves, and then close the evacuation machine to avoid air reverse flow; 5 after 5 to 10 minutes of static observation, observe the low pressure gauge, and the vacuum is not lost, then the next operation can be carried out.
2.2.4 Filling the refrigerating oil When the system is replaced with components or recycled, the system needs to be replenished with the refrigerating oil. The method is as follows: 1. Use the vacuum function of the system to inhale the refrigerating oil from the low pressure side during the evacuation process. .
2 Judging the amount of filling: When replacing the compressor, the old compressor and the refrigerating oil in the new compressor that need to be replaced are respectively poured into two measuring cups, and the new compressor refrigeration oil is used 50 times more than the old compressor. mL can be used; replace the condenser, need to add 30 ~ 40 mL;
To change the evaporator, you need to add 40 ~ 50 mL; replace the gas-liquid separator or connect the pipeline, you need to add 10 ~ 20 mL; if the recycling operation, it will be supplemented according to the amount recovered.
2.2.5 Refilling of the refrigerant 2.2.5.1 Filling from the high pressure side 1) The filling condition system is in vacuum and the compressor stops.
2) Connect the intermediate maintenance hose to the refrigerant tank, open the refrigerant tank opening valve, and loosen the joint of the intermediate maintenance hose head to empty. When there is white misty gas, the emptying ends. Tighten the connector.
3) Invert the refrigerant tank and slowly unscrew the high pressure manual valve to allow the refrigerant to enter the system in liquid form. The method can also be used to determine whether the throttling tube is blocked by observing the pressure of the low pressure gauge during the filling process. If the pressure of the low pressure gauge rises as the pressure of the high pressure gauge rises, the system is normal.
2.2.5.2 Filling from the low pressure side 1) Filling conditions: The compressor works.
2) The refrigerant tank installation and emptying process is the same as the high pressure side filling method.
3) Stand up the refrigerant tank and slowly unscrew the low pressure manual valve to allow the refrigerant to enter the system in a gaseous state.
2.3 Inspection 1) Inspection conditions: avoid direct sunlight; open the engine cover; open the front door; the air-conditioning switch and blower switch are adjusted to the maximum; the intake mode is in the outer cycle; the engine speed is 5 to 10 minutes at 1 500 r/min.
2) The pressure value is read by the pressure gauge group, which should meet the value of Figure 4, that is, the refrigeration system works normally.
3) Insert a thermometer at the air outlet, and the temperature of the air outlet is in accordance with the value in Figure 4, that is, the cooling effect is normal.
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