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 effi ciency. 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 coeffi cients to compensate for which the heat-transfer surface on the source side of the air is increased by fi nning the tubes. With the aim of raising the effi ciency 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 fi nned 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-fi nned 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 diff ers fundamentally from similar dependences for multirow staggered bundles because of the infl uence of upper rows
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 effi ciency. 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 coeffi cients to compensate for which the heat-transfer surface on the source side of the air is increased by fi nning the tubes. With the aim of raising the effi ciency 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 fi nned 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-fi nned 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 diff ers fundamentally from similar dependences for multirow staggered bundles because of the infl uence of upper rows
Author:  E. S. Danil′chika, G. S. Marshalova, A. B. Sukhotskii
Keywords:  air-cooled apparatuses, free convection, bimetal fi nned tube, heat-exchange multirow bundle, Nusselt number, Grashof number, Rayleigh number
Page:  801