Question 31. Newton-Rikhman law is given by

Question 32. The convection coefficients for boiling and condensation lie in the range

Question 33. Forced air flows over a convection heat exchanger in a room heater, resulting in a convective heat transfer coefficient 1.136 k W/m² K. The surface temperature of heat exchanger may be considered constant at 65 degree Celsius, and the air is at 20 degree Celsius. Determine the heat exchanger surface area required for 8.8 k W of heating

Question 34. The value of film coefficient is dependent upon
(i) Boundary layer configuration
(ii) Geometry and orientation of the surface
(iii) Surface conditions

Question 35. A region of fluid motion near a plate in which temperature gradient exist is

Question 36. Thermo-physical properties of the fluid are represented by
(i) Density
(ii) Viscosity
(iii) Specific heat
(iv) Thermal conductivity
Identify the correct option

Question 37. Air at 20 degree Celsius flows over a flat surface maintained at 80 degree Celsius. The local heat flow at a point was measured as 1250 W/m² .Take thermal conductivity of air as 0.028 W/m K, calculate the temperature at a distance 0.5 mm from the surface

Question 38. A motor cycle cylinder consists of ten fins, each 150 mm outside diameter and 75 mm inside diameter. The average fin temperature is 500 degree Celsius and the surrounding air is at 20 degree Celsius temperature. Make calculations for the rate of heat dissipation from the cylinder fins by convection when motor cycle is stationary and convective coefficient is 6 W/m² K

Question 39. For laminar flow over a flat plate, the average value of Nusselt number is prescribed by the relation
Nu = 0.664 (Re)^0.5 (Pr)^0.33
Which of the following is then a false statement?

Question 40. The convective heat transfer coefficient in laminar flow over a flat plate