Figure 11-7.--Construction of an air-cooled condenser.
is obtained by closely spaced fins on the coils. The coil
As the piston moves upward (view B of fig. 11-6),
and fin arrangement is similar to that of an automobile
the pressure within the cylinder becomes greater than
the pressure in the suction line. The intake valve closes.
As the piston continues upward, the pressure within the
Maintenance of an air-cooled condenser used on a
cylinder continues to increase. When the pressure
mobile air-conditioner is relatively minor, consisting of
becomes greater than the pressure in the discharge line,
keeping the coil and fins free of dust and dirt. This
the exhaust valve opens. The compressed refrigerant
should be done with care so as not to bend or damage
vapors discharge into the high-pressure side of the
the coil and fins.
A reciprocating compressor is lubricated by
pressure from an oil pump or by splash as the
The purpose of the receiver (fig. 11-8) is to collect
the liquid refrigerant as it leaves the condenser. It serves
as a reservoir for the refrigerant and maintains a liquid
seal on the liquid line to the expansion valve.
The purpose of the condenser (fig. 11-7) in a
A receiver is designed to be large enough to hold
refrigeration system is to convert the hot refrigerant
the complete charge of refrigerant required for the unit
vapor from the compressor into a liquid state. The
to operate. It is equipped with shutoff valves on the inlet
condenser removes heat from the hot vapor, causing it
and outlet lines to permit maintenance personnel to
to condense at the pressure existing in the high-pressure
pump the unit down (entrap all refrigerant in the
side of the system. The condenser removes and
receiver) when work is being done on another
dissipates the latent heat from the compressed gas to the
component of the system. With the shutoff valves
surrounding air or water and transforms the refrigerant
closed, no loss of refrigerant occurs.
gas to a liquid.
Due to the location of the inlet and outlet to the
The design of the condenser is determined by the
receiver, the receiver prevents the entrance of gaseous
cooling medium (usually air or water). The condenser
refrigerant into the liquid line. In most receivers there is
may be made of coils of tubing with cooling fins on the
a safety device to prevent excessive pressure buildup in
outside, or coils of tubing (one tube inside another)
the system. Some receivers are equipped with liquid
with a coolant running through the inner tubing. The
type of condenser used usually depends on the size of
the unit. Air-cooled condensers are generally used on
small units, and water-cooled condensers are normally
used on large units. Air-cooled condensers are the type
you will work on.
The air-cooled condenser uses a flow of ambient
(surrounding) air across the coils of the condenser to
provide a cooling effect. Maximum condenser surface
Figure 11-8.--Refrigerant receiver.