They are called hair tubes because of their very small diameter. Its location is between the filter output (driver) and the evaporator inlet, and its diameter and length are critical to the quality of the coolant created.

Hairpins are used as refrigerant flow controllers in refrigeration systems.

Refrigerator controllers have two tasks:

2. Allow the liquid refrigerant to flow from the liquid tube to the evaporator with the same intensity of liquid evaporation in the operator.

2. Differentiate the pressure between the high-pressure and low-pressure sides of the system, so that the refrigerant can be distilled under conditions that evaporate at low evaporator pressure at the same time at high pressure in the condenser. Of the several controllers, hairpins are used in low capacity refrigeration systems and automatic and thermostatic expansion valves in high capacity refrigeration systems.

The hairpin is the simplest device to control the refrigerant flow and involves a certain length of tube at a very low diameter between the condenser and the evaporator. Due to the high frictional resistance and low diameter as well as the suffocation phenomenon caused by the gradual evaporation of the refrigerant liquid in the tube due to the decrease in pressure to less than saturation pressure, the hair tube resists the condenser flow to the evaporator by controlling the passage of refrigerant flow, Keeping the pressure difference between the two as necessary, the resistance of the hair tube with the specified length and diameter is constant in the refrigerant flow, and the flow rate is proportional to the pressure difference on the sides of the tube, which is the difference between the evaporation and distillation pressure of the refrigerant system. And the flow capacity in the hair tube is equal to the pumping capacity.

If the design of the hair tubes is appropriate to the refrigeration capacity and applied correctly, it will work satisfactorily within an acceptable range of operating conditions.

Hair tubes differ from other types of refrigerant flow controllers in that they do not stop during the cycle of shutdown, as they occur during system shutdown, high side pressure and low pressure through the hair tube. Equals. For this reason, such systems usually do not use a liquid tank.

In addition to simple and inexpensive construction, hair tubes reduce the cost of refrigeration and production. Soldering is a certain length from the hair tube to the suction tube to create a heat exchanger between the two tubes, which results in the infrared cooling and steam superheating of the output of the operator.