A piece of beef steak 5 cm thick will be frozen in the freezer room -40 ° 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 10 W / (m² K). t f = hour.

13. Solve

2.12 A mass of 5 kg of water is contained in a piston-cylinder device at 125 kPa. Initially, 2 kg of the water is in the liquid phàse and the rest is in the vapor phase. Heat is now transferred to the water, and the piston, which is resting on a set of stops, starts moving when the pressure inside reaches 300 kPa. Heat transfer continues until the total volume increases by 20%. a) Determine the initial and final temperatures. b) Calculate the mass of liquid water when the piston first starts moving. c) Calculate the work done during this process. d) Show the process on a P-V diagram