Convection heat transfer in a shell-and-tube heat exchanger using sheet fins for effective utilization of energy

Convection heat transfer in a shell-and-tube heat exchanger using sheet fins is numerically investigated. Heat and mass transfers in the heat exchanger are modeled under steady state to estimate the heat transfer rate and the pressure drop for various geometries of the heat exchanger. Based on the numerical results, the Nusselt number and pressure drop are formulated for practical applications. For convenience, similar expressions to those of conventional shell-and-tube heat exchangers, that is, the functions of dimensionless numbers such as the Reynolds number, are derived. In these equations, the geometry of the heat exchanger, fin efficiency, and contact thermal resistance are included as major factors. On formulating the equation for the overall heat transfer rate, it is found that the heat transfer coefficient for the heat exchanger with a fin does not correspond to the combination of the heat transfer coefficient of bare tube surface and the fin. This is because the heat exchange area is substantially limited especially at the narrow space between the tube and the fin. A correction factor for the substantial heat transfer area is therefore introduced. These formulated equations are helpful for installing sheet fins in manufactured heat exchangers. Using the formulated equations, effective conditions to enhance heat transfer rate by the fin are established, taking into account the increase in pressure drop.

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