The capillary tube is formed by a pliable copper tube of great length and reduced diameter in relation to the liquid line. Its function is to cause the pressure drop in the refrigerant fluid that comes from the condenser in the state of liquid undercooled under high pressure.
Capillary tubes have the advantage of being inexpensive, simple expansion elements that allow rapid equalization of high and low pressures, yet require precise charge of coolant and do not control the flow of fluid to the evaporator.
There are several diameters of capillary, their reference measurements being based on the internal diameter in inches. Ex: 030 (0.030 "), 031 (0.031"); 042 (0.042 "), 050 (0.050"), 071 (0.071 "). In case of replacement of the capillary, its dimensions (internal diameter and original length) must be respected.
