Handbook of air conditioning and refrigeration / Shan K

11.22 CHAPTER ELEVEN
If a receiver is installed after the condenser, the liquid line between the condenser and receiver
should be sized so that liquid flows from the condenser to the receiver and gas flows in the opposite
direction. This section of liquid line is usually sized based on a liquid velocity of 100 fpm (0.5 m/s).
In the design and planning of the liquid line layout, the following factors must be considered:
● If a receiver is placed after the subcooling section of the condenser, subcooling will occur at the
outlet of the receiver only when a surge-type liquid receiver is used or if an additinal subcooling
setup is added after the receiver.
● Static pressure due to the liquid refrigerant column must be taken into account. At 105°F
(40.6°C), the density of liquid HCFC-22 is 70.3 lb/ft 3 (1125 kg/m 3 ). For each foot of liquid column,
the increase of static pressure is therefore �p s � 70.3/144 � 0.488 psi (3.4 kPa), or roughly
0.5 psi (3.5 kPa) for each foot of liquid column. At the top of a 10-ft (3-m) riser, the pressure is
about 10 � 0.5 � 5 psi (35 kPa) less than at the bottom of the riser.
Figure 11.12 is a Q rl-L eq chart for a liquid line with HCFC-22 at 40°F (4.4°C) suction temperature
and 105°F (40.6°C) condensing temperature with a pressure drop corresponding to a change of 1°F
(0.56°C) saturation temperature.
For suction temperature other than 40°F (4.4°C) and condensing temperature other than 105°F
(40.6°C), the corrected refrigeration load is calculated as
Q rl,c �
Qrl Fliq, s Fliq,c (11.4)
Correction factor Fliq,s takes into account the effect of enthalpy difference hlv-hen on m˙ r.
Correction
factor Fliq,c also takes into account the effect of enthalpy difference on m˙ r.
Its values are listed in
Table 11.1. When Tcon � 105°F (40.6°C), Fliq,c � 1, and Qrl,c � Qrl. FIGURE 11.12 Liquid line sizing Q rl--L eq chart for HCFC-22 at 40°F suction temperature and 105°F condensing
temperature (type L copper tube, outside diameter, 1°F change in saturated temperature).