Free-Convection Heat Transfer on Multirow Bundles of Finned Tubes with Circular Fins

The use of free convection in various industries grows, which is due to the increase in heat loads, and also to the closer attention to energy efficiency. Thus, for air-cooled apparatuses at certain parameters of the outside air, there is a possibility to decouple fan drives and to operate the apparatuses in an energy-saving free-convection regime. Here, a distinctive feature of the free-convection regime are high values of heat-transfer coefficients to compensate for which the heat-transfer surface on the source side of the air is increased by finning the tubes. With the aim of raising the efficiency of heat-transfer processes, it is expedient to optimize the geometric parameters and arrangement of a bundle, the number of rows, and the location of the bundle in space.

The paper presents a review of experimental and numerical investigations into the heat transfer of multirow horizontal and inclined bundles of finned tubes in a free-convection regime. This paper is a continuation of [1] in which a review has been presented of experimental and numerical investigations into the free-convection heat transfer on air-cooled annular-finned tubes and single-row bundles thereof. Importantly, the character of the dependences of the heat transfer of single-row bundles on the transverse pitch of the tubes differs fundamentally from similar dependences for multirow staggered bundles because of the influence of upper rows.