In general, heat exchanger design assumes that fluid flow through the bundle of tubes will be evenly distributed. Experience has shown that this is not always true and the consequences of maldistribution in terms of poor performance and increased fouling are often severe.
Poor distribution can mean areas of low velocity and stagnation within the tube bundle leading to areas of ineffective heat transfer and increased risk of tubeside fouling. Numerical simulation is a valuable tool for quantifying the effects of surface velocity distribution on heat exchanger performance. It is observed that the use of constant values for the thermal and transport properties of the heat transport medium results in prediction of inaccurate heat transfer coefficients. Also for prediction of heat transfer in a situation of fluid-to- solid heat transfer, as it occurs in the case in a heat exchanger, arbitrary boundary conditions such as constant wall temperature, constant heat flux, etc., are not applicable. In this situation, it is essential to model the equipment considering conjugate heat transfer.

The performance of heat exchangers can be assessed with CFD. This is particularly important for situations where the exchanger configurations are different enough so that empirically based correlations are inapplicable. Mech-well provides numerical simulations over a variety of models of heat exchangers.