Input data

  1. Compressor capacity

  2. Evaporating temperature

  3. Condensing temperature

  4. Return gas temperature

Optimal capillary tube selection is highlighted in green on the output table.

CapSel Capillary Tube Selection Software Copyright © 2012/2019, Secop GmbH Germany

This software allows the user to calculate the measurements of a capillary tube throttling device for a refrigeration system using empirical formulas. The result is a start value for optimization. The start value will result in an acceptable operating system.

In certain cases, the best possible choice of capillary diameter and length might deviate remarkably from this calculated result.

The capillary sizing is based on the assumption that the capillary and suction line is connected to in min. 1 m to make internal heat exchange between liquid and suction gas.

The refrigerant used is chosen from a drop-down list. Input values should be representative values for the refrigeration system.

The input values are:

  • Compressor capacity
  • Evaporating temperature
  • Condensing temperature
  • Return gas temperature
  • No sub-cooling

The input data are limited per refrigerant according to experience and compressor application areas.

Data such as these could reflect data sheet performance data at ARI 540, EN 12900 or CECOMAF conditions, or others.

The list of capillary tube inner diameters typically includes available sizes from different countries. They will not all be available on one place. A length value for an available diameter size is to be chosen by the user, or estimated, if not listed.

The list of refrigerants and capillary tube diameters and the calculation formulas and limits could be adapted through updates, based on new experience.

Database update 3.0 (2022)
R290 Not modified since September 2017
R600a Updates in April 2018
R134a Not modified since September 2017
R1234yf New since November 2019
R404A Not modified since May 2006
R407C Not modified since September 2017
R452A New since November 2019
R507 Not modified since September 2017
R513A New since November 2019
R22 Not modified since September 2017
R170 New since May 2023


Secop accepts no responsibility for possible errors in the CapSel program.

Secop reserves the right to alter its products without notice.

All trademarks in this material are property of the respective companies.

Secop and the Secop logotype are trademarks of Secop GmbH. All rights reserved.

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Value out of range
Value out of range
Value out of range
Value out of range
Flow rate 0 (N2 at delta p )

Capillary Tube Recommendation

Optimal capillary tube selection is highlighted in green on the output table.

Length Diameter