heat and mass transfer exam ii - iowa state university and mass transfer exam ii chapter 8: internal...
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Heat and Mass Transfer Exam II
Chapter 5: Transient Conduction Summary of transient heat transfer results for constant surface temperature 푇
Heat and Mass Transfer Exam II
Summary of transient heat transfer results for constant surface heat flux 푞
Heat and Mass Transfer Exam II
Chapter 6: Introduction to Convection Dimensionless Parameters for heat and mass transfer. 퐿 refers to the geometry of the system
Number Definition Number Definition
Biot 퐵푖 ℎ퐿푘
Nussult 푁푢 ℎ퐿푘
Mass Biot 퐵푖 ℎ 퐿퐷
Peclet 푃푒 푉퐿훼
Friction Coefficient 퐶
휏휌 푉 2⁄
Prandtl 푃푟 휈훼
Fourier 퐹표 훼푡퐿
Reynolds 푅푒 휌푉퐿휇
Mass Fourier 퐹표
퐷 푡퐿
Schmidt 푆푐 휈퐷
Grashof 퐺푟 푔훽(푇 − 푇 )퐿휈
Sherwood 푆ℎ ℎ 퐿퐷
Boundary Layer equations and their y-direction boundary conditions
Evaporative Cooling: energy consumed by a combination of heat and mass transfer and occurs when a gas flows
over a liquid and is dependent on the flux of the species
푞 = 푛 ℎ ℎ(푇 − 푇 ) = ℎ ℎ (휌∗(푇 ) − 휌 , )
Reynolds Analogy: relates velocity, thermal, and concentration boundary layers, restricted by the accuracy of the boundary layer which is depended on 푃푟and 푆푐 ≈ 1 and Δ푃 ≈ 0, 푺풕 = Stanton number
퐶2
= 푆푡 = 푆푡 푆푡 =푁푢푅푒푃푟
푆푡 =푆ℎ
푅푒푆푐
Heat and Mass Transfer Exam II
Chapter 7: External Flow Summary of convection heat transfer correlations for external flow
Heat and Mass Transfer Exam II
Chapter 8: Internal Flow Summary of convection heat transfer correlations for internal flow
Chapter 9: Free Convection Fluid motion is due to buoyancy forces within the fluid – buoyancy occurs due to a density gradient Methodology for convection calculation
1. Identify flow geometry/geometries for the system 2. Specify the appropriate reference temperature to evaluate fluid properties 3. For mass transfer, fluid properties refer to species 퐵 for binary mixtures 4. Calculate 푅푒 number 5. Decide whether a local or surface average coefficient is required 6. Select appropriate correlation(s) for the system