The length and diameter of the capillary tube is chosen to match
the flow capacity of the tube to the pumping capacity of the
compressor. These seamless tubes are made of copper and act as a
throttling valve to meter the amount of refrigerant entering the
evaporator. There is only one set of conditions at which a
capillary tube will operate at maximum efficiency. The inside
diameter of capillary tubes is as small as 0.02 in. (50 mm).
Dealing with such small diameters can lead to blockage if large
particles reach the tube. If the tube does become blocked, then
the evaporator becomes starved. The suction pressure drops, less
refrigerating effect takes place, and the compressor is forced
to work harder, resulting in increased head pressures with
accompanying increases in temperature. The cause of capillary
tube blockage is the accumulation of particles large enough to
significantly block refrigerant flow. In refrigeration systems,
an insoluble chemical or particles may be introduced during the
system assembly pr