A piece of beef steak 7 cm thick will be frozen in the freezer room -40 ° C. the product has a moisture content of 73%, a density of 970 kg / m cubic, and a thermal conductivity (frozen) of 1.1 W / (mK). 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 transfer coefficient of 10 W / (m squared K)

A 10 cm-thick beef steak is being frozen in a -40°C room. The product has 73% moisture content, density of 970 kg/m³, and thermal conductivity (frozen) of 1.1 W/(m K). Estimate the freezing time using Plank’s equation. The product has an initial freezing temperature of  -1.75°C, and the movement of air in the freezing room provides a convective heat-transfer coefficient of 10 W/(m² K). a. tf =... h

A 300 mm thick wall (k= 1.5 W/mK, p = 2600 kg/m³, cp = 1000 J/kg⚫K) has a uniform original temperature of 900 °C. At the time t = 0, its both surfaces are suddenly exposed to air (T∞ = 25 °C, h = 30 W/m²K). (a) Calculate the Biot number of the wall. Does it have a uniform temperature? (b) After 3 hours, what is the temperature at the middle plane (@x = 0)? Symme try ½ L= 300 mm h = 30 W/m² K wall T∞ = 25°C h = 30 W/m² K To=25°C 9. Ah (T-To G=ept Hot air x p = 2600 kg/m³ k=1.5 W/m K 900c Hot air Tr= 96w arrume te Now.

A food product wants to be produced in a small round shape (pellet) by freezing it in a water blast freezer freezer. Air freezer operates at -25 ° C. The initial product temperature is 25 ° C. The pellet has a diameter of 0.5 cm, and a density of 980 kg / m3. The initial freezing temperature is -2.5 ° C. The latent heat of freezing of the product is 280 kJ / kg. The thermal conductivity of the frozen product is 1.9 W / (m ° C). The convective heat transfer coefficient is 50 W / (m? K). Calculate the freeze time.