Refrigeration system pressure and temperature detection

PubDate:2017-10-18Author:Jinlun CompanySources:Mingdi Heat PumpViews:752

1Pressure concept of refrigeration system

The refrigeration system can be divided into high and low pressure parts during operation. The high pressure section is from the exhaust port of the compressor to the front of the throttle valve. This section is called high pressure. The suction port pressure of the compressor is called the suction pressure, and the suction pressure is close to the evaporation pressure. The difference between the two is the flow resistance of the pipeline. Pressure loss is generally limited to below 0.018 MPa.

For convenience, both the evaporation pressure and the condensing pressure of the refrigeration system are detected at the suction and exhaust ports of the compressor. That is, it is usually called the suction and exhaust pressure of the compressor. The purpose of detecting the suction and exhaust pressure of the refrigeration system is to obtain the evaporation temperature and the condensation temperature of the refrigeration system, thereby obtaining the operating state of the refrigeration system.

2Temperature concept in refrigeration systems

The temperature in the refrigeration system involves a wide range of surfaces, such as evaporation temperature te, suction temperature ts, condensation temperature, exhaust temperature, and the like. Determining the operating conditions of the refrigeration system is the evaporation temperature te and the condensation temperature tc.

Evaporation temperature te: refers to the temperature at which the liquid refrigerant is boiled and vaporized in the evaporator.

Example: te of air conditioning unit. 5 to 7 degrees as the evaporation temperature of the air conditioning unit, that is to say, the design of the air conditioning unit te is between 5 and 7 degrees. When the air conditioning unit after the maintenance is in debugging, if the te is less than 5 to 7 degrees, the response should be The expansion valve performs high speed and detects the suction pressure of the compressor. The purpose is to understand the evaporating temperature of the unit during operation, and te can not be directly detected, only by detecting the corresponding evaporating pressure to obtain its evaporating temperature (by referring to the refrigerant thermodynamic property table).

The condensing temperature tc is a temperature at which the superheated vapor of the refrigerant condenses into a liquid after being exothermic in the condenser.

The condensing temperature cannot be directly detected, but only by detecting the corresponding condensing pressure, and then by referring to the refrigerant thermodynamic property table. The condensing temperature is high and the condensing pressure is relatively increased, and they correspond to each other. The condensing temperature is extremely high, the unit load is heavy, the motor is overloaded, and the operation is unfavorable. The cooling capacity is correspondingly reduced, and the power consumption is increased, and should be avoided as much as possible.

Exhaust gas temperature td: refers to the temperature of the compressor exhaust port (including the temperature of the exhaust port nozzle).

The temperature of the exhaust gas must be measured by a temperature measuring device. Generally, the small machine is not set up. The temporary measurement can be detected by a semiconductor thermometer, but the error is large. The exhaust temperature is affected by the suction temperature and the condensing temperature. The suction temperature or the condensing temperature increases, and the exhaust temperature rises accordingly. Therefore, the intake temperature and the condensing temperature must be controlled to stabilize the exhaust temperature.

The suction temperature ts: refers to the gas temperature of the compressor suction connection pipe.

The temperature measurement device is required to detect the inspiratory temperature. Generally, the small unit does not have a temperature measuring device. Generally, it is estimated by hand touch during maintenance and debugging. The inspiratory temperature of the air conditioning unit generally requires control of ts=15 degrees. Exceeding this value has a certain effect on the cooling effect.