Estimation of Heat Transfer Coefficient Estimation of heat transfer coefficient is basically computation of temperature profile. A general theoretical and experimental study to understand how the stagnant layer is developed. The global geometry of the solid wall and flow conditions will decide the structure of stagnant layer. Basic Geometry : Internal Flow or External Flow.
Methods to evaluate convection heat transfer Empirical (experimental) analysis –Use experimental measurements in a controlled lab setting to correlate heat and/or mass transfer in terms of the appropriate non- dimensional parameters Theoretical or Analytical approach –Solving of the boundary layer equations for a particular geometry. –Example: Solve for Use evaluate the local Nusselt number, Nu x Compute local convection coefficient, h x Use these (integrate) to determine the average convection coefficient over the entire surface –Exact solutions possible for simple cases. –Approximate solutions also possible using an integral method
Experimental test setup insulation L Measure current (hence heat transfer) with various fluids and test conditions for Fluid properties are typically evaluated at the mean film temperature
Suggested Initial Data Inner Pipe diameter : 2’’ to 3’’ Outer Pipe diameter: 3” to 4” Convective heat transfer coefficient of hot oil, h oil = 2250 W/m 2 K. Convective heat transfer coefficient of cooling water, h water = 1200 W/m 2 K. Thermal conductivity of metals: Copper = 398 W/m.K Mild Steel = 60.5 W/m.K Stainless Steel = 15.1W/m.K