COMPILATION OF DATA ON CONVECTIVE HEAT TRANSFER OF ANNULAR FINNED TUBE BUNDLES WITH AN EXHAUST SHAFT

Air-cooled heat exchangers in various industries enjoy an increasingly wider use thanks to their environmental friendliness and absence of the need for cooling water. Air-cooled heat exchangers from annular fi nned tubes are widely used in chemical, petrochemical, oil-refi ning, gas, and food industries, and also at automobile compressed natural gas fi lling stations (NGV gas stations), in heat power engineering, electric power engineering, refrigeration technology, and at nuclear power plants. The thermal capacity of air-cooled heat exchangers is largely determined by the characteristics of the motion of a fl ow of cooling air through them that can be organized with consumption of electric power by means of a ventilator or in an energy-saving regime 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 heat transfer intensity compared to forced convection is the main drawback of the free-convection regime which is usually compensated by an increase in a heat-emitting area, namely, by fi nning the heat transfer surface. By equipping air-cooled heat exchangers with additional devices making it possible to intensify free convection, the thermal performance of heat exchangers can be improved signifi cantly. The paper provides an overview of experimental and numerical investigations of free-convection heat transfer in annular fi nned tube bundles with an exhaust shaft installed above them.
Air-cooled heat exchangers in various industries enjoy an increasingly wider use thanks to their environmental friendliness and absence of the need for cooling water. Air-cooled heat exchangers from annular fi nned tubes are widely used in chemical, petrochemical, oil-refi ning, gas, and food industries, and also at automobile compressed natural gas fi lling stations (NGV gas stations), in heat power engineering, electric power engineering, refrigeration technology, and at nuclear power plants. The thermal capacity of air-cooled heat exchangers is largely determined by the characteristics of the motion of a fl ow of cooling air through them that can be organized with consumption of electric power by means of a ventilator or in an energy-saving regime 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 heat transfer intensity compared to forced convection is the main drawback of the free-convection regime which is usually compensated by an increase in a heat-emitting area, namely, by fi nning the heat transfer surface. By equipping air-cooled heat exchangers with additional devices making it possible to intensify free convection, the thermal performance of heat exchangers can be improved signifi cantly. The paper provides an overview of experimental and numerical investigations of free-convection heat transfer in annular fi nned tube bundles with an exhaust shaft installed above them.
Author:  A. B. Sukhotskii, G. S. Marshalova and E. S. Danil′chik
Keywords:  bimetallic annular fi nned tube, heat transfer bundle, Nusselt number, Grashof number, Rayleigh number, exhaust shaft, mixed convection
Page:  525