# Environmental Conditions — Kimura convection model not working

Last Updated:

Tuesday, September 5, 2017

### Software/Versions Affected:

- WINDOW›6

In the Environmental Conditions Library Convection section, one of the "Model" options is "Kimura". This model calculates the Convection Coefficient based on "Inside Air Velocity" and "Air Direction". The program correctly calculates the convection coefficient based on this model, but when that Environmental Condition is then used in the Glazing System Library, the program uses a convection coefficient based on an air velocity of 0. A work around for this bug is to calculate the convection coefficient using the Kimura model, and then input that coefficient into the Fixed Convection Coefficient model, which does work properly.

Documentation for the Kimura model can be found in the following references:

- Kimura, K., 1977.
*Scientific Basis for Air Conditioning*, Chapter 3, "Radiative and Convective Heat Transfer", pp. 93-94, Equations 3.41 to 3.44, Applied Science Publishers, London. - Ito, N., K. Kimura, and J. Oka, 1972. "A field experimental study on the convective heat transfer coefficient on exterior surface of a building",
*ASHRAE Transactions*, Vol. 78, Part 1. - S. Shakerin (1987). "Wind-Related Heat Transfer Coefficient for Flat-Plate Solar Collectors".
*Journal of Solar Energy Engineering*, May 1987; 109; pp. 108-110.