The effect of friction factor on the unsteady state mixed convective-radiative heat transfer in an inclined cylindrical annulus is investigated from continuity, momentum and energy equations. The outer cylinder is kep...The effect of friction factor on the unsteady state mixed convective-radiative heat transfer in an inclined cylindrical annulus is investigated from continuity, momentum and energy equations. The outer cylinder is kept at a constant temperature while the inner cylinder is heated with constant heat flux. The governing equations are normalized and solved using the vorticity-stream function and the BFC （body fitted coordinates） methods. The two heat transfer mechanisms of convection and radiation are treated independently and simultaneously. A computer program （Fortran 90） was built to calculate Nusselt number （Nu） and friction factorffor unsteady state condition for fluid Prandtl number fixed at （Pr = 0.7） （for air as working fluid） with radius ratio （/~ = 2.6）, Rayleigh number （0 〈 Ra 〈 103）, Reynolds number （50 〈 Re 〈 2,000）, conduction-radiation parameter （0 〈 N 〈 10）, optical thickness （0 〈 l＂ 〈 10） and different annulus inclination with horizontal plane （0~ _〈 d 〈 90~） for concentric cylindrical annulus. For the range of parameters considered, results show that radiation enhance heat transfer. It is also indicated in the results that as 3 increasefwill be decrease and also when Re increasefwill be decrease for any value of Ra causing increase in heat transfer. The maximum value off can be recognized at ~ = 90~ and the minimum value at 6 = 0~ for low Re. There is an optimum value of annulus inclination that gives maximum value of Nu, this maximum value appears at 90~ of annulus inclination comparison of the result with the previous work shows a good agreement.展开更多
The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat transfer theorem. A correction for the heat calculation method for pressurized furnace is made...The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat transfer theorem. A correction for the heat calculation method for pressurized furnace is made on the basis of the normal pressure case. The correction takes the effect of pressurizing into account. The results show that the correction is reasonable and the method is applicable to combustion and heat transfer of the marine supercharged boiler.展开更多
文摘The effect of friction factor on the unsteady state mixed convective-radiative heat transfer in an inclined cylindrical annulus is investigated from continuity, momentum and energy equations. The outer cylinder is kept at a constant temperature while the inner cylinder is heated with constant heat flux. The governing equations are normalized and solved using the vorticity-stream function and the BFC （body fitted coordinates） methods. The two heat transfer mechanisms of convection and radiation are treated independently and simultaneously. A computer program （Fortran 90） was built to calculate Nusselt number （Nu） and friction factorffor unsteady state condition for fluid Prandtl number fixed at （Pr = 0.7） （for air as working fluid） with radius ratio （/~ = 2.6）, Rayleigh number （0 〈 Ra 〈 103）, Reynolds number （50 〈 Re 〈 2,000）, conduction-radiation parameter （0 〈 N 〈 10）, optical thickness （0 〈 l＂ 〈 10） and different annulus inclination with horizontal plane （0~ _〈 d 〈 90~） for concentric cylindrical annulus. For the range of parameters considered, results show that radiation enhance heat transfer. It is also indicated in the results that as 3 increasefwill be decrease and also when Re increasefwill be decrease for any value of Ra causing increase in heat transfer. The maximum value off can be recognized at ~ = 90~ and the minimum value at 6 = 0~ for low Re. There is an optimum value of annulus inclination that gives maximum value of Nu, this maximum value appears at 90~ of annulus inclination comparison of the result with the previous work shows a good agreement.
文摘The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat transfer theorem. A correction for the heat calculation method for pressurized furnace is made on the basis of the normal pressure case. The correction takes the effect of pressurizing into account. The results show that the correction is reasonable and the method is applicable to combustion and heat transfer of the marine supercharged boiler.
