Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Impact of Air and Refrigerant Maldistributions On the Performance of Finned-Tube Evaporators With R-22 and R-407C



J Lee, Piotr A. Domanski


The report presents basic features of the evaporator model, EVAP5M, and simulation results for an evaporator operating with R-22 and R-407C at non-uniform air and refrigerant distributions. EVAP5M was developed under this project to provide a tool for simulating a finned-tube air-to refrigerant evaporator operating with single-component refrigerants and refrigerant mixtures. The tube-by-tube modeling approach allowed for one-dimensional non-uniformity in the air velocity profile and arbitrary maldistribution on the refrigerant side. The model uses the Carnahan-Starling-DeSantis equation of state for calculating refrigerant thermodynamic properties. Simulations were performed for three evaporator slabs with different refrigerant circuitry designs. For the maldistributions studied, maldistributed air caused much more significant capacity degradation than maldistributed refrigerant. In some cases capacity decreased to as low as 57 percent of the value obtained for uniform velocity profile. Simulation results showed that R-22 and R-407C have similar susceptibility to capacity degradation. Relative change of capacity varied depending on the evaporator design and maldistribution studied.


air conditioning, evaporator, heat transfer, modeling, refrigeration, refrigerant mixtures


Lee, J. and Domanski, P. (1997), Impact of Air and Refrigerant Maldistributions On the Performance of Finned-Tube Evaporators With R-22 and R-407C, OTHER, National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed May 25, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created June 30, 1997, Updated October 12, 2021