Heat Pump Design Model

Heat Pump Design Model logo.

Research tool for use in the steady-state simulation and design analysis of air-to-air heat pumps and air conditioners. The program can be used with most of the newer HFC refrigerants as well as with HCFCs and CFCs. The standard vapor-compression cycle is modeled with empirical representations for compressor performance and first-principle region-by-region modeling of the heat exchangers.

An online Web version is available that can be used with default configurations or with user-specified component and operating parameters for analyzing the performance of single-speed, air-to-air equipment. User configurations can be saved for later use. Parametric analyses can be made and performance trends plotted online.

See sample pages. Keep in mind these are only sample pages so the links and buttons will not work.


heat pump, air conditioner, air-to-air heat pump, equipment simulation



Expertise Required

Moderate-to-high level of technical understanding of vapor-compression heat pumps to use effectively.


Over 350 recipients of PC-DOS version, over 14,000 online runs of Web version.


Public and private research/consulting organizations, research and development engineers of air-conditioning and heat pump equipment companies, university engineering faculty and graduate students.


Compressor performance map, heat exchanger and (optionally) flow control design information, defaults are provided to run sample case for design capacity cooling condition, HTML-forms-based input that can be locally saved for later reuse.


Summary cycle diagrams of operating conditions, component sizing and performance, and charge requirements (Web version); online x-y, contour, and 3-D surface plots and spreadsheet importable data sets of parametric results; user-selectable levels of text output.

Computer Platform

Web version runs on any platform (PC, Mac, Unix) supporting current Internet browsers (Java capability not required), PC-DOS version requiring math coprocessor also available.

Programming Language

HTML Forms/Tables, Perl Script, FORTRAN


Predicts EER, capacity, air- and refrigerant-side conditions for cooling or heating operation with first-principles heat exchanger modeling; handles a variety of refrigerants; will size flow control devices given heat exchanger (HX) design exit conditions; useful in studying the general performance trends when varying HX design parameters (with or without a fixed design capacity) and operating conditions (with or without a fixed refrigerant charge and flow control); moderate accuracy with fast execution; user-tuneable; two-variable parametrics capability.


Assumes simplified HX circuitry (equal parallel circuits in crossflow), cannot model HX flow splits and confluences, requires compressor map for desired refrigerant, uses fixed airflows (airflow does not vary as air-side pressure drop changes), better in predicting performance trends than absolutes unless model is tuned for particular design, requires use of predicted rather than nameplate refrigerant charge for off-design calculations, can progressively overestimate performance at higher levels of HX exit superheat or subcooling in multiple row coils.



Oak Ridge National Laboratory


Buildings Technology Center
P.O. Box 2008, Mailstop 6070
Oak Ridge, Tennessee 37831-6070
United States


(865) 574-2016


(865) 574-9338






Web version directly accessible, PC-DOS version with similar capabilities available by correspondence at no cost to users with suitable applications. Documentation reports and application papers are available online as well as more discussion of recent Web version improvements and related models. Other information is available on the Buildings Technology Center and Heating and Cooling Equipment web sites.