Subcool Condenser Line Sizing

Hey guys!

I am new to the forums! This is my first post but i have always kept my eyes on the topics here. Plenty of helpful info around. I am a design engineer for a ref/chiller company with a degree in mechanical engineering. This is my first job after college, so my ref knowledge level compared to most of you here is unmatched.

My question to you guys is in regards to pipe sizing. I am currently designing a unit with 50 ton cooling capacity. I am running a single compressor with two V-shape condensers (2 coils per V) tied together by a manifold. There is also another condenser coil specifically for subcooling. The condenser outlets are tied together with another (lower) header which is piped to a receiver below. Here is where things get muggy for me. After the receiver, the piping routes to the inlet of the subcool condenser and out of the outlet to the filter driers, exp, etc. When calculating my liquid line length, do i consider the subcool line from the receiver outlet to subcool condenser inlet as part of it?



For reference, this is what i have so far. In the calculations below, i considered the lines from receiver to subcooled condenser to be a part of the liquid line:

Superheated Vapor
Discharge to Condenser Inlet
2-1/8”
• Actual Length: 81’
• Velocity: 2083 ft/min
• Pressure Drop.: 3.3 psi/3 psi maximum
• Temperature Drop.: 0.9 F/ 1F maximum

Line Components:
.52’ (Pipe) + 3.9’ (90 Elbow LR) + 2’ (Pipe) + 3.9’ (90 Elbow LR) + 3.36’ (Pipe) + 3.9’ (90 Elbow LR) + 4.04’ (Pipe) + 12’ (2.625 Tee) + 10’ (Header) + 4*7’ (1.375 Tee) + 4*2.3 (1.375 90 Elbow LR) = 80.82 ft.

Saturated Mixture
Condenser Outlet to Receiver Inlet
2-1/8”
• Actual Length: 90.46’
• Velocity: 157 ft/min
• Pressure Drop.: 0.4 psi
• Temperature Drop.: 0.1 F

Line Components:
0.6’ (Pipe) + 3.9’ (90 Elbow LR) + 0.66’ (Pipe) + 3.9’ (90 Elbow LR) + 2.2’ (Pipe) + 12’ (2.625 Tee) + 10’ (Header) + 4*7’ (1.375 Tee) + 4*2.3 (1.375 90 Elbow LR) + 20’ (Valve) = 90.46 ft.




Saturated Liquid
Receiver Outlet to Subcooled Condenser to Meter Device
1-5/8”
• Actual Length: 253’
• Velocity: 273 ft/min
• Pressure Drop.: 3.2 psi/ 3 psi maximum
• Temperature Drop.: 1.2 F/ 1F maximum



Line Components:
0.7’ (Pipe) + 2.8’*11 (90 Elbows LR) + 17’*2(Ball Valves) + 6’ (Pipe) + 2.5’ (Pipe) + 1.6’ (Pipe) + 8’*2 (Tee) + 1.3’ (Pipe) + 1.25’ (Pipe) + 35’ (Filter Drier) + 17’*2 (Ball Valves) + 35’ (Solenoid Valve) + 2’ (Sight Glass) + 1’ (Pipe) = 201.15 ft.

Suction Line
Evaporator Outlet to Compressor Inlet
3-1/8”
• Actual Length: 39.55 ft
• Velocity: 3018 ft/min
• Pressure Drop.: 0.7 psi / 2.6psi maximum
• Temp. Drop.: 0.6 F/ 2F maximum

Line Components:
0.6’ (Pipe) + 5’ (90 Elbow LR) + 1.75’ (Pipe) + 5’ (90 Elbow LR) + 2.9’ (Pipe) + 5’ (90 Elbow LR) + 2.1’ (Pipe) + 0.3’ (Pipe) + 5’ (90 Elbow LR) + 1.3’ (Pipe) + 5’ (90 Elbow LR) + 0.6 (Pipe) + 5’ (90 Elbow LR) = 90.15’ = 39.55 ft.