Capillary tube usually refers to a slender copper tube with an inner diameter between 0.4 and 2.0 millimeters. As a simple throttling mechanism in refrigeration systems, it is widely used in small refrigeration equipment due to its low cost and flexible selection advantages. Next, we will explore the influence of capillary length on refrigeration system parameters and introduce how to eliminate the phenomenon of capillary "ice blockage".

The influence of capillary length on refrigeration system parameters. The length of capillary has a direct impact on the performance of refrigeration systems. Firstly, at the same refrigerant charge, a shorter capillary tube will result in a larger refrigerant flow rate, which will cause a decrease in the suction and discharge temperatures of the compressor. At the same time, as the flow rate increases, the suction pressure will also rise accordingly; However, when the filling amount is fixed, the shorter the capillary tube, the lower the exhaust pressure.

In terms of condenser, when the refrigerant charge remains constant, shortening the capillary tube can reduce the condensation temperature and pressure; On the contrary, if the capillary length is fixed, increasing the filling amount will increase the condensation temperature and pressure. The evaporator also follows a similar pattern: at a fixed filling amount, shortening the capillary tube will increase the evaporation temperature and pressure; When the capillary length is fixed, an increase in the filling amount will also cause an increase in evaporation temperature and pressure.

Regarding subcooling and superheat, the longer the capillary length, the higher the subcooling and superheat; When the capillary length is constant, increasing the filling amount will lead to an increase in subcooling, but a decrease in superheat.

In addition, the length of the capillary also affects the refrigeration efficiency (EER) of the entire system. Under the same charging conditions, although extending the capillary length can reduce power consumption, it sacrifices cooling capacity and EER value; However, once the charging amount reaches a critical point, the cooling capacity and EER may be improved due to the increase in heat transfer temperature difference.

In order to ensure the stable operation of the refrigeration system, the design points of the capillary system should pay attention to the following: the high-pressure side generally does not use a liquid reservoir, unless specific requirements such as heat pump systems or shutdown evacuation systems require it. The suction pipeline should be equipped with a gas-liquid separator to prevent liquid from flowing back to the compressor and causing damage. The high-pressure part of the system must have sufficient capacity to accommodate all refrigerant charges to prevent damage to other components in the event of capillary blockage. Considering the potential increase in condensation pressure under high load conditions, it is necessary to appropriately expand the condenser area. The pipeline between the condenser outlet and the capillary inlet should not retain refrigerant liquid to avoid unnecessary heat loss or delay in system equilibrium. Install a filter at the capillary inlet to prevent impurities from entering and ensure that the refrigerant has appropriate subcooling, thereby reducing gas flash and optimizing the refrigeration effect. When encountering the problem of "ice blockage" in capillaries, the first step is to confirm the existence of the problem through the above methods. Once it is determined to be an ice blockage, the refrigerant in the system needs to be discharged and vacuum dried. Simultaneously clean key components such as evaporator and condenser, and consider replacing new dry filters or cleaning existing filters.

If the problem is found to be caused by high water content in the refrigerant, a dry filter can be added at the outlet of the refrigerant cylinder to ensure that excess water can be absorbed during refilling.

Reasonable design of capillary length and its related configuration is crucial for ensuring the efficient and reliable operation of refrigeration systems. At the same time, timely and effective handling of common faults such as "ice blockage" is also the key to maintaining the normal operation of refrigeration equipment