Installation
Liquid Sub Cooling
The degree of liquid sub cooling required to prevent ashing of liquid refrigerant can be calculated by the following
method.
Given the following as an example:
• Refrigerant R410A
• Condensing temperature (54.4°C) equivalent
condensing pressure at 54.4°C = 34 Bar
• Liquid lift 20m
• Piping friction loss 0.21 bar
• Losses through valves and ttings 0.5 Bar
Pressure Loss due to Liquid Lift
Note:- At normal liquid temperatures
the static pressure loss due to
elevation at the top of a liquid lift
0.115 bar/m.
= H x spl
Where
H = Height (m)
spl = Static pressure loss
= 20 x 0.115 = 2.3 bar
Total Pressure Loss in Liquid Line
TPL Liquid = PFL + Valves
Where
PFL = Pipe friction loss (0.21Bar)
Valves = Losses through Valves and ttings
= 0.21 +0.5 + 2.3
Total pressure loss in liquid line = 3.01 Bar
Nett Pressure at Expansion Valve
= Condensing pressure - Total pressure loss in liquid line
Saturation temperature at the nett pressure
at expansion valve (30.99 bar) = 52°C
(from refrigerant tables)
Sub Cooling Required
=Condensing temperature - Saturation temperature
= 34 - 3.01 = 30.99 bar
Subcooling = Condensing temperature — Saturation temperature (Nett pressure at expansion valve)
= 54.4 - 52 = 2.4 °C
Therefore liquid sub cooling required to prevent
liquid ashing = 2.4 °C
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