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NIST Standard Reference Database 49

CYCLE_D: NIST Vapor Compression Cycle Design Program: Version 5.0

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CYCLE_Dsimulates vapor compression refrigeration cycles that use single-compound refrigerants or refrigerant blends. The model can simulate a basic subcritical or transcritical refrigeration cycle, both with or without a liquid-line/suction-line heat exchanger. In addition, the model can simulate a subcritical two-stage economizer cycle, a subcritical three-stage economizer cycle, and a subcritical two-stage compression cycle with intercooling.

CYCLE_Dincludes 62 single-compound refrigerants and 66 predefined blends. Single-compound fluids can be combined to form blends of up to five components. Computationally, the program is fully compatible with the NIST Reference Fluid Thermodynamic and Transport Properties Program - REFPROP, Version 9.0.


The basic subcritical or transcritical system simulated by CYCLE_D consists of a compressor, a discharge line, a condenser for the subcritical cycle (a gas cooler for the transcritical cycle), an expansion device, an evaporator, a compressor suction line, and an optional liquid-line/suction-line heat exchanger. The other subcritical cycles may contain a second compressor, and one or two economizers or an intercooler (but do not include the liquid-line/suction-line heat exchanger).

The user of the program has to specify the refrigerant and provide input data for the above hardware components, except the expansion device, which is modeled as being isenthalpic. The user can also specify the power requirements of the indoor fan, outdoor fan, and control unit of the system.

Please click here to view the PDF version of Users' Guide.

System Requirements: Personal computer capable of running MS-WindowsTM 98, 2000, NT, and XP operating systems; hard disk with 8.0 MB available space. The screen resolution should be set to 800 x 600 or higher to view images in their entirety.

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Standard Reference Data Program
National Institute of Standards and Technology 100 Bureau Dr., Stop 8550
(301) 975-2200 (VOICE) / (301) 975-4553 (FAX) / Contact Us


The scientific contact for the database is:

Piotr A. Domanski
National Institute of Standards and Technology 100 Bureau Drive, Stop 8631
Gaithersburg, MD 20899-8631
301 975 5877

Keywords: air conditioning; alternative refrigerant; ammonia; chemical engineering; vapor compression cycle; compressor; cooling equipment; equation of state; mechanical engineering; refrigerants; refrigeration.