Combustor, heat transfer

Toor, J. S. and Boni, A. A., "A Model Combustor Heat Transfer Problem-Radiative Transfer Between Surfaces With Nongray Gases and Soot," Heat Transfer 1974, Vol. 1, Proc. of 5th International Heat Transfer Conference, Tokyo, Japan, 1974. 

Combustor Heat Transfer Technology Group School of Engineering Cranfield University, Cranfield Bedfordshire, MK43 OAL, UK... 

Bed-to-Surface Heat Transfer. Bed-to-surface heat-transfer coefficients in fluidized beds are high. In a fast-fluidized bed combustor containing mostly Group B limestone particles, the dense bed-to-boiling water heat-transfer coefficient is on the order of 250 W/(m -K). For an FCC catalyst cooler (Group A particles), this heat-transfer coefficient is around 600 W/(600 -K). 

High Temperature. The low coefficient of thermal expansion and high thermal conductivity of sihcon carbide bestow it with excellent thermal shock resistance. Combined with its outstanding corrosion resistance, it is used in heat-transfer components such as recuperator tubes, and furnace components such as thermocouple protection tubes, cmcibles, and burner components. Sihcon carbide is being used for prototype automotive gas turbine engine components such as transition ducts, combustor baffles, and pilot combustor support (145). It is also being used in the fabrication of rotors, vanes, vortex, and combustor. 

In the model equations, A represents the cross sectional area of reactor, a is the mole fraction of combustor fuel gas, C is the molar concentration of component gas, Cp the heat capacity of insulation and F is the molar flow rate of feed. The AH denotes the heat of reaction, L is the reactor length, P is the reactor pressure, R is the gas constant, T represents the temperature of gas, U is the overall heat transfer coefficient, v represents velocity of gas, W is the reactor width, and z denotes the reactor distance from the inlet. The Greek letters, e is the void fraction of catalyst bed, p the molar density of gas, and rj is the stoichiometric coefficient of reaction. The subscript, c, cat, r, b and a represent the combustor, catalyst, reformer, the insulation, and ambient, respectively. The obtained PDE model is solved using Finite Difference Method (FDM). 

Ackeskog et al. (1993) made the first heat transfer measurements in a scale model of a pressurized bubbling bed combustor. These results shed light on the influence of particle size, density and pressure levels on the fundamental mechanism of heat transfer, e.g., the increased importance of the gas convective component with increased pressure. 

Figure 45. Comparison of heat transfer coefficient measured in 20 MW bubbling bed combustor vs prediction from MIT cold test. (From Glicksman et al, 1987)...

Vedamuthy, V. N., and Sastri, V. M. K., An Analysis of the Conductive and Radiative Heat Transfer to Walls of Fluidized Combustors, Intern. J. Heat Mass Transf, 17(1) 1-9 (1074)... 

Circulating Beds These fluidized beds operate at higher velocities, and virtually all the solids are elutriated from the furnace. The majority of the elutriated sohds, still at combustion temperature, are captured by reverse-flow cyclone(s) and recirculated to the foot of the combustor. The foot of the combustor is a potentially very erosive region, as it contains large particles not elutriated from the bed, and they are being fluidized at high velocity. Consequently the lower reaches of the combustor do not contain heat-transfer tubes and the water walls are protected with refractory. Some combustors have... 

Current and future combustor applications require increased energy release with reduced chamber volume, increased equilibrium temperature, multiphase reacting flows with radiative heat transfer, and sometimes even with electric and magnetic fields. A thorough understanding of the basic physical and chemical... 

The goal of the present study is to provide the information needed for design of a practical underwater propulsion system utilizing powdered aluminum burned with steam. Experiments are being conducted in atmospheric pressure dump combustors using argon/oxygen mixtures and steam as oxidizers. Spectrometer measurements have been made to estimate combustion temperatures and radiant heat transfer rates, and samples of combustion products have been collected to determine the composition and particle size distribution of the products. 

In order to show the effect, TPG model has been used to re-simulate the 15 kW load step decrease with a 1% turbine efficiency increase. Figure 8.20 shows a slight increase in the amplitude of the rotational speed transient behavior. However, as with the NETL model, the frequency is not much affected. Therefore, it is likely that some of the amplitude error from the NETL model comes from performance map. It is also possible that some of the difference comes from a different heat transfer model for the NETL post-combustor, V 304. 

Greenberg. J. B. and Goldman, Y. (1989). Volatilization and burning of Pulverized coal with radiation heat transfer effects on a counter flow combustor. Combustion Sci. Tech., 64 1-17. 

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