FREE CONVECTION HEAT TRANSFER ON ANNULAR-FINNED TUBES AND BUNDLES THEREOF

The use of air-cooled heat exchangers in various industries has increasingly become wide-spread due to their environmental friendliness and the absence of the need for cooling water. Air-cooled heat exchangers made of annular-fi nned tubes are widely used in chemical, petrochemical, oil-refi ning, gas, and food industries, and also at automobile CNG fi lling stations, in heat power and electric power engineering, refrigeration technology, and at nuclear power plants. The heat power of air-cooled heat exchangers is largely determined by the characteristics of the motion of the fl ow of cooling air through it, which can be organized with consumption of electric power by means of a ventilator or in an energy-saving regime, i.e., by free convection. Unfortunately, the region of ambient air temperatures, at which it is possible to use air-cooled heat exchangers under the conditions of free convection, is limited. Low intensity of heat transfer compared to forced convection is the main disadvantage of a free convective regime, which is usually compensated by an increase in the heat-transfer area, namely, by fi nning the heat-transfer area. In the case of equipping air-cooled heat exchangers with additional devices that make it possible to intensify free convection the heating capacity of a heat exchanger can be signifi cantly increased. The paper presents a review of experimental and numerical investigations of free convection heat transfer on air-cooled annular-fi nned tubes and bundles thereof
The use of air-cooled heat exchangers in various industries has increasingly become wide-spread due to their environmental friendliness and the absence of the need for cooling water. Air-cooled heat exchangers made of annular-fi nned tubes are widely used in chemical, petrochemical, oil-refi ning, gas, and food industries, and also at automobile CNG fi lling stations, in heat power and electric power engineering, refrigeration technology, and at nuclear power plants. The heat power of air-cooled heat exchangers is largely determined by the characteristics of the motion of the fl ow of cooling air through it, which can be organized with consumption of electric power by means of a ventilator or in an energy-saving regime, i.e., by free convection. Unfortunately, the region of ambient air temperatures, at which it is possible to use air-cooled heat exchangers under the conditions of free convection, is limited. Low intensity of heat transfer compared to forced convection is the main disadvantage of a free convective regime, which is usually compensated by an increase in the heat-transfer area, namely, by fi nning the heat-transfer area. In the case of equipping air-cooled heat exchangers with additional devices that make it possible to intensify free convection the heating capacity of a heat exchanger can be signifi cantly increased. The paper presents a review of experimental and numerical investigations of free convection heat transfer on air-cooled annular-fi nned tubes and bundles thereof
Author:  G. S. Marshalova, A. B. Sukhotskii, V. B. Kuntysh
Keywords:  free convection, bimetal annular-fi nned tube, heat-transfer bundle, Nusselt number, Grashof number, Rayleigh number, air-cooled device
Page:  1089