Fast, approximate analyses of heat transfer and fluid flow using Finite Element Analysis

abstract

en

Proper design of heat transfer equipment used in process and power industries can lead to improved energy efficiency. It can also prevent various operating problems, thus resulting in fewer service shutdowns and longer equipment service life. The most common operating problems encountered in the mentioned field are the increased local fouling rates due to uneven flow distribution and mechanical failures of the tubes in the bundle stemming from non-uniform thermal loading (which can, again, be a direct consequence of the flow distribution being largely non-uniform). Because of the significant computational demand and complexity of Computational Fluid Dynamics (CFD) models, however, the currently prevailing approach is to design equipment under the assumption of uniform fluid flow and temperature distributions in the bundle. Only in rare cases, the resulting apparatus is analyzed in more detail to verify that the previously made assumptions have been appropriate. In the presentation, therefore, a fast flow distribution and heat transfer model is discussed. The model is based on Finite Element Analysis (FEA) and utilizes a simplified mesh. This makes it suitable for approximate analyses of large, yet – construction-wise – relatively simple process and power equipment such as heat recovery hot water boilers. Computational times observed in case of typical industrial equipment tend to be of the order of minutes. Consequently, the model can be used to quickly get the estimates of velocity and temperature fields in the tube and the shell sides of the analyzed heat transfer apparatus or to rapidly and easily evaluate large sets of possible design options and discard the unsuitable ones. The capabilities of the model are demonstrated through the analysis of a heat recovery heat exchanger in an existing medium-size combined heat and power (CHP) plant. The outlook in terms of further development of the model is also discussed together with possible avenues leading to improvements in computational efficiency of the respective computer implementation.

Proper design of heat transfer equipment used in process and power industries can lead to improved energy efficiency. It can also prevent various operating problems, thus resulting in fewer service shutdowns and longer equipment service life. The most common operating problems encountered in the mentioned field are the increased local fouling rates due to uneven flow distribution and mechanical failures of the tubes in the bundle stemming from non-uniform thermal loading (which can, again, be a direct consequence of the flow distribution being largely non-uniform). Because of the significant computational demand and complexity of Computational Fluid Dynamics (CFD) models, however, the currently prevailing approach is to design equipment under the assumption of uniform fluid flow and temperature distributions in the bundle. Only in rare cases, the resulting apparatus is analyzed in more detail to verify that the previously made assumptions have been appropriate. In the presentation, therefore, a fast flow distribution and heat transfer model is discussed. The model is based on Finite Element Analysis (FEA) and utilizes a simplified mesh. This makes it suitable for approximate analyses of large, yet – construction-wise – relatively simple process and power equipment such as heat recovery hot water boilers. Computational times observed in case of typical industrial equipment tend to be of the order of minutes. Consequently, the model can be used to quickly get the estimates of velocity and temperature fields in the tube and the shell sides of the analyzed heat transfer apparatus or to rapidly and easily evaluate large sets of possible design options and discard the unsuitable ones. The capabilities of the model are demonstrated through the analysis of a heat recovery heat exchanger in an existing medium-size combined heat and power (CHP) plant. The outlook in terms of further development of the model is also discussed together with possible avenues leading to improvements in computational efficiency of the respective computer implementation.

Finite Element Analysis; fluid flow; heat transfer; process and power industry equipment

26.08.2020

2653-8911

7

1

5–5

1