Compactness in Shell And Tube Heat Exchangers

In this article, we would like to clarify a term used in the classification of heat exchangers.

In simple terms, compactness is the classification of heat exchangers according to the ratio of heat transfer surface to heat transfer volume. For this classification, exchangers are also defined as a size called β surface area density.

β = Heat Transmission Surface (m2) / Heat Exchanger Volume (m3)

According to the above-mentioned formula, heat exchangers with β > 700 m2/m3 can be defined as compact heat exchangers, and those with β ≤ 700 m2/m3 can be defined as non-compact heat exchangers. For shell and tube heat exchangers, the compactness can be defined as the heat exchange surface A, the volume V, the total heat transfer coefficient K, the logarithmic temperature difference ∆tm, the magnitude β and the heat transfer rate Q as follows.



To give more detailed technical information, it is possible to establish an approximate correlation between the geometric size and compactness of shell and tube heat exchangers as shown in the figure below.

In shell and tube heat exchangers;

To interpret compactness in terms of fluid phases in exchangers, generally, heat convection coefficients in gaseous fluids are smaller than in liquid fluids. For this reason, in heat exchangers with gas on one side and liquid on the other, the surface area of the gas phase side should be increased. Increasing the surface area increases compactness as stated in the formula above. The addition of blades to the outer surfaces of the pipe as shown in the example below will increase the heat exchanger compactness.