Forschungszentrum für Kältetechnik und Wärmepumpen GmbH
Forschungszentrum für Kältetechnik und Wärmepumpen GmbH

RefCycle (KMKreis) is an FKW developed program to calculate refrigeration cycles of different configurations.
RefCycle (K
MKreis) can be run in different languages like German, English, Spanish, French and Dutch

Cycle Calculation Program RefCycle(KMKreis 7.2)

Cycle Calculation Program RefCycle (KMKreis 7.2) for Windows

The program KMKreis allows to calculate p-v-t data as well as different refrigeration cycle performance data for an extended number of refrigerants. Until now more than 60, nearly all available refrigerants, pure ones as well as blends, are implemented. The list of refrigerants implemented in the former version of the program, KMKreis 6.2 has been updated and expanded.

The essential innovation since KMKreis 7 concerns the calculation of the refrigerant properties. The refrigerant data is not loger (as until KMKreis version 6.2) calculated with equations of state especially adjusted to the particular refrigerant by FKW. KMKreis since version 7 now uses the REFPROP.dll of the National Institute of Standards and Technology (NIST).

In the current version KMKreis 7.2, the program has been extended with the function to calculate pipe data.

KMKreis allows fast and simple calculation of all relevant thermodynamic characteristics of refrigeration cycles. An extended number of different, often used basic types of refrigeration cycles are therefor implemented into the program:

  • single-stage compression,
  • single-stage compression with internal heat exchange,
  • two-stage compression with interstage pressure bottle,
  • two-stage compression with interstage injection,
  • two-stage compression with interstage pressure cooling,
  • two-stage compression with a cascade,
  • two-stage compression cycle with flash-gas interstage suction, and
  • a single-stage heat pump cycle.

Separately, the single stage trancritical CO2 cycle can be calculated.


The variables of state for all process points, the volumetric capacity and, on given desired system refrigeration capacity or geometric volumetric displacement of the compressor with regard to its volumetric efficiency, the capacities and power requirements as well as the mass flow(s) are calculated.
Each calculation can be executed simultaneously for different parameters, so that fast comparisons are possible.
In addition the influence of pressure losses can be considered.
The calculated processes are shown in a lg p,h-diagram. In this diagram the dew and bubble curves of the choosen refrigerant and the calculated refrigeration cycle are shown.

Additionally, the program allows for each refrigeration cycles the calculation of pipe data for a first Line Sizing of the suction gas line, the liquid line and the discharge gas line and the choise of pipe dimensions from different selection series of copper and steel pipes standards.

Furthermore KMKreis allows to calculate variables of state (t, p, v, h, s) as well as transport properties (Thermal Conductivity, Viscosity, Thermal Diffusivity) in vapour pressure tables for the VLE region (pressure or temperature variable) as well as in tables for the superheated region (pressure variable, temperature as the fixed parameter or vice versa) for all implemented refrigerants. The program incorporates also the possibility of a fast calculation of variables of state and transport properties for single points.

Further features of KMKreis:

  • Languages: the program can be run in German, English, French, Dutch and Spanish (except the help file)
  • Possibility to save user definied (start) parameters of the different calculation windows
  • Calculations can be made in SI-Units as well as in british (imperial) units, with the possibility to switch between the units within the program for easy comparison
  • Calculations can be printed, copied to clipboard and copied to table calculation programs (like MS Excel)

Copyright and Disclaimer

KMKreis is a product of the:

Forschungszentrum für Kältetechnik und Wärmepumpen GmbH (FKW)
Weidendamm 14

D-30167 Hannover


Tel.: ++49(0)511/167475-0




FKW provides with KMKreis a Refrigeration- Cycle- Calculation Program, that uses the fluid data of the National Institute of Standards and Technology (NIST) by use of the 'refprop.dll', distributed with the graphical user interface REFPROP provided by NIST. It must be made a hint here to the user help distributed with REFPROP, as far as the use of the REFPROP data is concerned. It is assumed, that the user knows these notes of application, or uses them for reference, if problems with the use of the 'refprop.dll' may occur.


The information provided herein is believed to be accurate, but is not warranted nor is it intended to be used without independent verification. So the user assumes sole responsibility for any results obtained in reliance on this information. Statements or suggestions concerning possible use of the fluids are made without representation or warranty that any such use is free of patent infringement, and are not recommendations to infringe any patent. The user should not assume that all safety measures are indicated, or that other measures may not be required.


Date of the program and the given information: 2014, april.


Please refer to the Copyright and Disclaimer of REFPROP.

The Copyright and Disclaimer of REFPROP version 9.1 is cited here:

REFPROP is a product of the

National Institute of Standards and Technology (NIST)


Developed and maintained by

Applied Chemicals and Materials Division

Boulder, CO 80305, USA


Distributed by

Standard Reference Data

Gaithersburg, MD 20899, USA



Standard Reference Databases are copyrighted by the U.S. Secretary of Commerce on behalf of the United States of America. All rights reserved. No part of the database may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without prior permission.



The National Institute of Standards and Technology (NIST) uses its best efforts to deliver a high-quality copy of the database and to verify that the data contained therein have been selected on the basis of sound scientific judgement. However, NIST makes no warranties to that effect, and NIST shall not be liable for any damage that may result from errors or omissions in the database.

Forschungszentrum für Kältetechnik und Wärmepumpen GmbH


Weidendamm 14

D 30167 Hannover

Tel.: +49(511)-167 475-0


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