Convection Heat Transfer In Furnace

The convection section is located above the radiant section where it is cooler to recover additional heat.

Convection heat transfer in furnace.

Fuel combustion and heat transfer in a furnace heat is needed in a furnace for heating of the furnace charge material to be heated in the furnace and sometimes for the chemical reactions. The gas path for the turbotreater vacuum furnace with the added option of convection heating. The area is filled with tubes or pipes which carry process steam and which absorb heat via convection heat transfer from the hot gases passing through the area on their way out of the stack. Solids are heated by direct contact but fluids are usually heated indirectly being carried inside pipes within the furnace.

The configuration of furnaces is such that two radi ant zones have one common convection section for heat recovery. The three sources of heat energy are i combustion of fuels ii electric energy and iii chemical energy available through the exothermic reactions. Heat transfer takes place by convection here and the tubes are finned to increase heat transfer. The rest of the radiation is partly absorbed by glass interior absorptance depending on glass thickness which slightly decreases the thickness wise temperature gradient and thermal shock in glass at initial stages of the heating.

Heat from the burning in the furnace is recov ered to preheat feed bfw preheat dilution steam super heating and high pressure steam superheating. Unlike radiant heating gas does not discriminate against part geometry. Convection heating uses gas in most cases nitrogen or argon at a higher temperature than the furnace chamber as well as a fan to circulate heat to all parts in the load. Although often discussed as a distinct method of heat transfer convective heat transfer involves the combined processes of unknown conduction and advection.

Furnaces employing combustion produce a hot gas which transfers heat to the material by radiation and convection. Convection contact heat transfer as well as about 46 of the radiation in a tempering furnace affect glass surfaces from which heat is conducted deeper into the glass. Convection is usually the dominant form of heat transfer in liquids and gases. Heat transfer is only one process in the furnace for which an exact solution cannot be obtained unless four groups of equations corresponding to the four processes are solved simultaneously.

The first three tube rows in the bottom of the convection section and at the top of the radiant section is an area of bare tubes without fins and are known as the shield section shock tubes so named because they are still exposed to plenty of radiation from the firebox and they also. Alternatively a regenerative heat exchangermay be used to transfer heat from the combustion gases.