A piece of beef steak 5 cm thick will be frozen in the freezer room -30 ° C. This product has a moisture content of 73%, a density of 970 kg / m³, and a thermal conductivity (frozen) of 1.1 W / (m K). Estimate the freezing time. using the Plank equation. This product has an initial freezing temperature of -1.75 ° C, and the movement of air in the freezing room gives a convective heat transfer coefficient of 15 W / (m² K). t f = hour

(a) What is the heat loss per unit length of the pipe?(b) The pipe material is switched to PTFE (k = 0.38 W/(m⋅K)). To maintain the same heat loss as theprevious question, if all other parameters are to remain the same as before, what is the required thicknessof the pipe wall in centimeters?

Insulating material is used to reduce heat loss from the heating furnace walls to the room. The surface temperature of the insulating material is 100 ° C and the other surfaces 25 ° C. Allowable heat loss up to 160 W / m2 from the wall. If the thermal conductivity of the insulation material is 0.05 W / (m ° C), calculate the required thickness of insulation. insulation thickness = Answer cm

The wall of a cold storage consists of three layers-an outer layer of ordinary bricks, 25 cm thick, a middle layer of cork, 10 cm thick, and an inner layer of cement, 6 cm thick. The thermal conductivities of the materials are-brick: 0.7, cork: 0.043, and cement: 0.72 W/m °C. The temperature of the outer surface of the wall is 30°C, and that of the inner is.-15°C. Calculate (a) the steady state rate of heat gain per unit area of the wall, (b) the temperatures at the interfaces of the composite wall, and (c) the percentages of the total heat transfer resistance offered by the individual layers. What additional thickness of cork should be provided to make the rate of heat transfer 30% less than the present value?

a piece of beef steak 7 cm thick will be frozen in the freezer room -40 degrees Celsius This product has a moisture content of 73% density 970 kg / m³ and a thermal conductivity of 1.1 W / (m K) frozen using the plank equation. This product has an initial freezing temperature of -1.75 degrees Celsius and the movement of air in the raw chamber gives a convection heat transfer coefficient of 10 W / (m² K). tf =

A piece of beef steak 7 cm thick will be frozen in the freezer room -30 ° C. This product has a moisture content of 73%, a density of 970 kg / m³, and a thermal conductivity (frozen) of 1.1 W / (m K). Estimate the freezing time. using the Plank equation. This product has an initial freezing temperature of -1.75 ° C, and the movement of air in the freezing room gives a convective heat transfer coefficient of 15 W / (m² K). t f = ... hour.

A 4mx5m wall consists of 3 glass windows of 1.5mx1.0m dimensions. The wall has thickness of 0.125 m and a thermal conductivity of 0.5 W/mK, while the glass windows are 6 mm thick with a thermal conductivity of 1.24 W/mK. The values of Internal and external surface conductance for the wall (including glass) are 8.3 W/m K and 34.4 W/m²K, respectively. The internal and external temperatures are 21°C and -30°C, respectively. Calculate the total heat transfer rate through the wall. What percentage of this heat transfer is through the windows?