HYDRODYNIC BOUNDARY LAYER, Velocity distribution, Boundary layer Thickness, Local and Average skin friction coefficient, Local and average shear stress, Drag force, Nussult number, Displacement thickness, Momentum thickness, Energy Thickness, Thermal boundary layer and its related terms HYDRODYNIC BOUNDARY LAYER (0 ≤ y ≤ δ and 0≤ u ≤ U∞) Flow over a flat plate (Forced […]
VALUES OF THERMAL CONDUCTIVITY ‘K’ AND THERMAL DIFFUSIVITY ‘α’ and VALUES OF EMISSIVITY, Є FOR VARIOUS MATERIALS, CONDUCTORS AND INSULATORS, HEAT TRANSFER GOVERNING EQUATIONS TABLE: VALUES OF THERMAL CONDUCTIVITY ‘K’ AND THERMAL DIFFUSIVITY ‘α’ FOR VARIOUS MATERIALS CASE 1: VALUES OF α < k (Mostly α is 33 % of k for metals and 40 […]
SYMBOLS IN HEAT TRANSFER —-3 q. =Q. Rate of heat transfer Used in Conduction, convection and radiation Watt (W) q’ =Q’ Rate of heat transfer per meter Used cylindrical/ pipe /wire heat exchangers Watt / meter (W/m) q”=Q” rate of heat transfer per m2 = HEAT FLUX Used in conduction, convection and radiation W […]
SYMBOLS IN HEAT TRANSFER —-2 G Incident radiation flux used in radiocity (J) and radiation exchange between two bodies, J = ЄEb + ρ G= (emitted + reflected) flux W/m2 h hi ho film coefficient Or convective HT Coefficient […]
SYMBOLS IN HEAT TRANSFER SYMBOL QUANTITY APPLICATION UNITS A Area (normal to the direction of heat transfer) Used in finding rate of heat transfer m2 Ac Cross sectional area (normal to the direction of heat transfer) Used in conduction through plane walls and fins m2 As Surface area (normal to the direction […]
Assumptions used in Heat Transfer (a) Assumptions used in 1-dimensional Steady State heat conduction Homogeneous and isotropic fin material (Constant material properties) Higher temperature and lower temperatures remain constant. No internal heat generation One-dimensional conduction Uniform cross-sectional area Negligible contact thermal resistance Negligible radiation (b) Assumptions used in Steady State heat Convection One-dimensional convection Homogeneous […]
Dimensional Analysis–Part 3 PROCEDURE FOR BUKINGHAM’S π METHOD Let total variables be ( X1, X2, X3, …, Xn ) = n , say n=6 Write X1 = F ( X2, X3, …, Xn) Now write it in the equation form containing n variables as F1 ( X1, X2, X3, …, Xn) = 0 Let m be the total fundamental dimensions for the n variables, say m= 4=M,L,T, θ Then number of dimensionless group in this case will […]
Multiple Choice Questions (mcq) on Heat Transfer—Overall heat transfer coefficient, heat flux and temperature variation Overall heat transfer coefficient is associated with (a) Conduction (b) Convection (c) Radiation (d) None (Ans: d) Overall heat transfer coefficient is associated with (a) Conduction and radiation (b) Convection and radiation (c) Radiation, convection and conduction (d) None (Ans: […]
Multiple Choice Questions (mcq) on Heat Transfer —-Conduction Thermal conductivity of metals with addition of alloying elements (a) Increases (b) Decreases (c) Remains constant (d) None (Ans: b) Thermal conductivity of metals with increase of hardness (a) Increases (b) Decreases (c) Remains constant (d) None (Ans: b) Thermal conductivity of a material with dampness (a) Increases […]
Multiple Choice Questions (mcq) on Heat Transfer —Conduction Poisson’ equation in heat transfer deals with (a) Steady state of heat transfer (b) Unsteady state of heat transfer (c) Steady as well as unsteady states of heat transfer (d) None (Ans: a) Laplace equation in heat transfer deals with (a) Steady state of heat transfer (b) Unsteady […]