Aradiator may be treated as a block body with a true surface area of 6m2 and an envelope area of 4m2. it has a surface temperature of 40°c and is situated in a dark room at 20°c. the surface heat transfer coefficient is 4w/m²k. calculate the radiated heat transfer and the convected heat transfer rate. calculate the radiated surface heat transfer coefficient and obtain the same answer using it.

At steady state, air at 200 kpa, 325 k, and mass flow rate of 0.5 kg/s enters an insulated duct having differing inlet and exit cross-sectional areas. the inlet cross-sectional area is 6 cm2. at the duct exit, the pressure of the air is 100 kpa and the velocity is 250 m/s. neglecting potential energy effects and modeling air as an 1.008 kj/kg k, determine ideal gas with constant cp = (a) the velocity of the air at the inlet, in m/s. (b) the temperature of the air at the exit, in k. (c) the exit cross-sectional area, in cm2