Session: K20-03 Computational Methods

Paper Number: 107153

107153 - Variable Properties via Excel: Numerical and Computational Heat Transfer Methods 

Numerous thermal analysis software such as ANSYS, COMSOL-Heat Transfer Module, PATRAN Thermal, STAR_CCM+, as well as numerous other sophisticated software, with varying levels of complexity are available in the market.  These complex software require extensive investment in training, in addition to continuous use to be fully mastered by the user.  Microsoft Excel is installed on most engineers’ personal computers.  Usually, engineers are competent in using Microsoft Excel as a spreadsheet to speed up calculations, and are skilled in creating charts with Microsoft Excel, but very few engineers can use Microsoft Excel for Numerical Simulations and modeling.  Microsoft Excel is inexpensive compared to any of the numerous commercial sophisticated thermal analysis software available in the market., e.g. the price of Excel is less that 8 % the price of Matlab.  Small companies, startup companies, and consulting engineers do not have the financial resources to acquire these expensive software, nor sending engineers for the essential required training.  Consequently, Microsoft Excel can be attractive for basic simulations and modeling.

The author published an article in which three Heat Transfer Numerical rectangular cross section cases using Microsoft Excel are discussed in detail [1].  The rectangular cross section cases are easy to address since Excel elements are square.  In engineering practice, many circular cross sections are encountered such as cylinders, pipes, rods, etc.  Consequently, the author published anther article [2] in which four Numerical Heat Transfer practical cases for circular cross sections using Microsoft Excel were introduced, discussed, and compared with Patran Thermal analysis.  Unfortunately, both articles addressed only constant properties.

All properties, whether thermal conductivity of a solid, or viscosity of a fluid vary with the temperature.  Dependence of proprieties of a fluid on temperature means that the heat transfer coefficient varies with temperature.  In this article heat transfer coefficients based on temperature dependent properties are derived for both internal and external flows, based on different correlations.  Not considering the variations of properties with temperature leads to inaccurate results.  Considering the variation of properties with temperature makes the derivation of the equations more complicated, but the extra effort gives more accurate results.

In this article several numerical computational cases with temperature dependent properties are introduced.  Some of the cases are for rectangular cross sections, while others are for circular cross sections.  Each case of the circular cross sections is solved with two different Excel methods one using cartesian coordinate system and the second using cylindrical coordinate system.  Some of the boundary conditions used are isothermal, heat flux, convection dependent on temperature.  The results from the variable properties are compared with analysis from constant properties cases.  The details of the simulations for each case and results are discussed in this article.

[1] Abdelmessih, Amanie N. “Inexpensive Numerical Methods for Heat Transfer Computation.” Proceedings of the 2017 ASME Summer Heat Transfer Conference, HT2017-4938, Bellevue, WA, July 9-14, 2017.

[2] Abdelmessih, Amanie N. “Numerical Methods for Heat Transfer Computations of Curved Surfaces Using Excel Techniques,” Proceedings of the 2022 ASME International Mechanical Engineering Congress & Exposition Conference, IMECE2022-95316, Columbus, OH, October 30-November 4, 2022. 

Presenting Author: Amanie Abdelmessih California Baptist University