Refrigerant Line Size Calculator

Inputs

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Nominal or design evaporator capacity used to estimate refrigerant mass flow.
Btu/h
Cooling effect per unit refrigerant mass. Enter this from cycle/property data; the default is only a comfort-cooling example.
Btu/lb
Actual internal diameter of the selected suction/vapor line. Use tube data, not nominal OD.
in
Actual internal diameter of the selected liquid line. Use tube data, not nominal OD.
in
Straight length plus equivalent length for elbows, traps, fittings and valves in the refrigerant line.
ft
Positive when liquid must lift upward. The calculator adds liquid static head only for positive lift.
ft
Vapor density at suction line temperature/pressure. This is user-entered property data, not a built-in refrigerant table.
lb/ft³
Liquid density at the checked liquid-line condition.
lb/ft³
Dynamic viscosity in micro-Pascal-seconds for the suction vapor condition.
uPa*s
Dynamic viscosity in micro-Pascal-seconds for the liquid condition.
uPa*s
Absolute roughness used in the Darcy friction factor. Clean drawn copper is very smooth; fittings are handled through equivalent length.
in
Entered minimum suction velocity for oil return screening.
ft/s
Entered upper suction velocity target for noise and pressure-drop screening.
ft/s
Entered upper liquid-line velocity target.
ft/s
Maximum acceptable suction friction pressure drop for this line screen.
psi
Maximum acceptable liquid line drop, including friction plus positive vertical lift head.
psi

Results

Default result
Edit inputs
Refrigerant mass flow(m_dot)
8.723lb/min

Mass flow is capacity divided by entered net refrigeration effect.

Also computed

Suction velocity(v_s)Pass19.66ft/s

inside entered suction velocity window

Liquid velocity(v_l)Pass4.113ft/s

inside entered liquid velocity target

Suction pressure drop(dp_s)Pass1.042psi

34.7% of entered pressure budget

Total liquid drop(dp_l,total)Caution4.749psi

95.0% of entered pressure budget; little margin

Liquid friction drop(dp_l,fr)4.749psi

Liquid lift head(dp_lift)0psi

Positive vertical lift only; negative lift is not credited.

Friction drop vs Equivalent lengthFriction drop scales with equivalent length for the selected line IDs and mass flow. Liquid lift head is listed separately in the results.Friction drop vs Equivalent length02468020406080Equivalent length (ft)Friction drop (psi)
Friction drop scales with equivalent length for the selected line IDs and mass flow. Liquid lift head is listed separately in the results.
Method notes 3 notes
  • Formula: refrigerant mass flow = cooling capacity / entered net refrigeration effect.
  • Velocity uses v = m_dot/(rho*A). Pressure drop uses Darcy-Weisbach with user-entered density, viscosity, tube roughness and total equivalent length.
  • Final refrigerant line sizing must follow the exact equipment manufacturer long-line guide, oil-return requirements, traps, capacity derates, refrigerant classification, local code and qualified HVAC design practice.

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