The production line of a special biscuit at 30 ̊C and 1 atm has a 0.8 X 0.8 (m) square plate. One side of the plate is maintained at a temperature of 100 ̊C, while the other side is insulated.   Determine the rate of heat transfer from the plate by natural convection if the plate (i) Is horizontal with the hot surface facing down; (ii) Is horizontal with the hot surface facing up;  Data: The properties of air at the film temperature are: thermal conductivity, k= 0.0279 W/m.k); kinematic viscosity= 1.815 x 10-5 m2/s; Pr = 0.709

1. (a)   Consider a room with a 1.8-m-high and 2.0-m-wide double-pane window consisting of two 4-mm-thick layers of glass separated by a 10-mm-wide stagnant air space. The convection heat transfer coefficients on the inner and outer surfaces of the window are 12 W/m2 K and 25 W/m2 K, respectively, while the average thermal conductivity of glass is 0.78 W/m K; and the air, 0.026 W/m K.   If the room is maintained at 22 oC, the outside temperature is -4 oC and heat transfer due to radiation can be neglected, determine:                 (i) Draw the sketch and thermal resistance network;                                                (ii) the total thermal resistance;                (iii) the steady rate of heat transfer through this double-pane window;                                                                              (iv) the temperature of the inner surface of the window.…

2. Juice in cans 150 mm long and 60 mm in diameter is initially at 27°C and is to be cooled by placement in a refrigerator compartment at 4°C. In the interest of maximizing the cooling rate, should the cans be laid horizontally or vertically in the compartment?