The capillary tube is one of the most commonly used throttling devices in refrigeration and air conditioning systems. The capillary tube is a copper tube with a very small internal diameter. It is of very long length and it is coiled to several turns so that it would occupy less space.
The capillary tube is an extremely simple device, and its use permits considerable simplification and cost reduction of the small hermetic refrigerating system. Using a capillary will: 1. Allow the use of a low cost, hermetic-type compressor and condensing unit, which has been specifically designed for capillary tube application. 2.
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One of the most commonly used throttling devices for the refrigeration and air conditioning systems is the capillary tube. The capillary tube is made up of copper and it has very small diameter ranging from 0.5 to 2.28 mm (0.020 to 0.09 inches). Capillary tube used as the throttling device in the domestic refrigerators, deep freezers, water coolers and air conditioners. When the refrigerant passes through the capillary tube there is drop in its pressure.
Capillary Tube Refrigeration – Working Principle, Construction & Applications. Capillary tube is used as an expansion valve in small capacity hermetically sealed refrigeration units such as domestic refrigerators, water coolers, room air conditioners and freezers. Capillary tube is a tube of small internal diameter and of varying length, which depends upon the application.
How the capillary tube length effects the performance of the refrigeration system. Capillaries generally refer to slender copper tubes with an internal diameter of 0.4 ~ 2.0 mm. As the throttling mechanism of the water chiller system, the capillary tube is the simplest. It is widely used in small cooling system because of its low price and flexible selection.
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Capillary tube use may extend to larger singlecompressor/single-evaporator systems, such as unitary air conditioners up to 35 kW capacity. The capillary tube is a piece of drawn copper tube with a small inner diameter. When used for controlling refrigerant flow, it connects the outlet of the condenser to the inlet of the evaporator. The term “capillary tube” is actually a misnomer because the inner bore, though narrow, is much too large to allow capillary action.
Capillary tube metering devices are found mainly in domestic and small commercial applications that experience somewhat constant heat loads on their evaporators. These systems also have small refrigerant flow rates and usually employ fully hermetic compressors.
Let us now follow the refrigerant as it flows thru the cap tube. Notice that the R12 enters the cap tube at 96° which is 16° sub cooled below it’s condensing temperature of 112° on the top scale, and at a pressure of 140 lbs. Also notice that for the first 8 ft. the refrigerant acts like water.