The effect of swirl on the heat transfer downstream of sudden axi-symmetric expansions in a circular duct
type: CreativeWork
description: The performance of an industrial furnace or boiler is dictated by three interrelated processes, namely: combustion, furnace aerodynamics, and heat transfer. Thus, the flow behaviour of the gases in a furnace chamber can have a significant influence on the combustion and heat transfer processes and hence the performance of the furnace. The rate of combustion depends on the rate of mixing between the fuel, air and combustion products and this can be enhanced either by increasing the jet momentum or by imparting a swirling motion to the burner fluids. Thus, the application of swirl is very common and there is also some evidence that it can lead to an increase in heat transfer to the load and walls of the enclosure. In most furnace applications radiation accounts for 90 - 95 % of the total heat transfer and convection is relatively small. However, there are applications where flame temperatures and emissivities are relatively low and convection becomes significant and accounts for up to approximately 50 % of the overall heat transfer. At the present time designers of industrial furnaces or boilers are often restricted to using a single value for the convective heat transfer based on empirical data for fully-developed duct flow since there is a lack of more reliable data on convective heat transfer. This PhD project aims to provide convective heat transfer data which can be applied in industrial furnace or boiler applications. The flow regimes developed by a burner firing into a furnace chamber are similar to those encountered downstream of a sudden expansion in a duct. The literature survey highlighted the lack of information on the effects of swirl on convective heat transfer in this geometry so that this topic is the main subject of the present thesis. Swirl was imparted with the aid of tangential inlets and the effect of the changes in the degree of swirl (including the zero swirl case), inlet to outlet duct diameter ratios, and inlet Reynolds numbers on the convecti…
abstract: The performance of an industrial furnace or boiler is dictated by three interrelated processes, namely: combustion, furnace aerodynamics, and heat transfer. Thus, the flow behaviour of the gases in a furnace chamber can have a significant influence on the combustion and heat transfer processes and hence the performance of the furnace. The rate of combustion depends on the rate of mixing between the fuel, air and combustion products and this can be enhanced either by increasing the jet momentum or by imparting a swirling motion to the burner fluids. Thus, the application of swirl is very common and there is also some evidence that it can lead to an increase in heat transfer to the load and walls of the enclosure. In most furnace applications radiation accounts for 90 - 95 % of the total heat transfer and convection is relatively small. However, there are applications where flame temperatures and emissivities are relatively low and convection becomes significant and accounts for up to approximately 50 % of the overall heat transfer. At the present time designers of industrial furnaces or boilers are often restricted to using a single value for the convective heat transfer based on empirical data for fully-developed duct flow since there is a lack of more reliable data on convective heat transfer. This PhD project aims to provide convective heat transfer data which can be applied in industrial furnace or boiler applications. The flow regimes developed by a burner firing into a furnace chamber are similar to those encountered downstream of a sudden expansion in a duct. The literature survey highlighted the lack of information on the effects of swirl on convective heat transfer in this geometry so that this topic is the main subject of the present thesis. Swirl was imparted with the aid of tangential inlets and the effect of the changes in the degree of swirl (including the zero swirl case), inlet to outlet duct diameter ratios, and inlet Reynolds numbers on the convecti…
author: Bertelmann, Andrea
language: eng
date published: 1997
date modified: 2026-07-24T04:39:25Z
provider: University of South Wales
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of South Wales