Layers of 23 cm-thick meat slabs ( k = 0.47 W/m*C and a=0.13*10 m/s) initially at a uniform temperature of 7 C are to be frozen by refrigerated air at -30 C flowing at a velocity of 1.4 m/s. the average heat transfer coefficient between the meat and the air is 20 W/m*C. Assuming the size of meat slabs to be large relative to their thickness, determine how long it will take for the center temperature of the slabs to drop to -18 C, Also, determine the surface temperature of the meat slab at that time

Layers of 23 cm-thick meat slabs ( k = 0.47 W/mC and a=0.1310 m/s) initially at a uniform temperature of 7 C are to be frozen by refrigerated air at -30 C flowing at a velocity of 1.4 m/s. the average heat transfer coefficient between the meat and the air is 20 W/m*C. Assuming the size of meat slabs to be large relative to their thickness, determine how long it will take for the center temperature of the slabs to drop to -18 C, Also, determine the surface temperature of the meat slab at that time

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter7: Forced Convection Inside Tubes And Ducts

Section: Chapter Questions

Problem 7.16P

See similar textbooks

Similar questions

1.60 Two electric resistance heaters with a 20 cm length and a 2 cm diameter are inserted into a well-insulated 40-L tank of water that is initially at 300 K. If each heater dissipates 500 W, what is the time required for bringing the water temperature in the tank to 340 K? State your assumption for your analysis.
4- Carbon steel balls 8 mm in diameter are annealed by heating them first to 900°C in a furnace and then allowing them to cool slowly to 100°C in ambient air at 35°C. If the average heat transfer coefficient is 75 W/m -°C, determine how long the annealing process will take. If 2500 balls are to be annealed per hour Given: Carbon steel [k = 54 W/m.°C, p = 7833 kg/m, and C,= 0.465 kJ/kg. °C. and a= 1.474x 10* m²/s] Air, 35°C Fumace Steel ball 100°C 900°C
Nuclear wastes are packed in a long, cylindrical container. The wastes steadily generate energy at auniform rate of 2.0 W/cm^3. If the container surface is cooled by convection of a water coolant at 30oC, determine the surface temperature of the container. The container diameter, d = 2 cm, and the heat transfer coefficient is 290 W/(m^2*K). Heat transfer by radiation from the surface is expected to be negligible.
A 65 kg beef carcass (k-0.47 w/mk and a-0.13 x10-6 m/s) initially at a uniform temperature of 37 "C is to be cooled by refrigerated air at -10 oC flowing at a velocity of 1.2 ms. The average heat transfer coefficient between the carcass and the air is 22 W/m²K. Treating the carcass as a cylinder of diameter 24 cm and the height 1.4 m and disregarding heat transfer from the base and top surfaces, Determine how long it will take for the centre temperature of the carcass to drop to 4 °C b. Also, determine if any part of the carcass will freeze during this process Hava- air -10 °C 12m/s Sider E Beef JTC
A pipe in a manufacturing plant is transporting superheated vapor at a mass flow rate of 0.3 kg/s. The pipe is 10 m long, has an inner diameter of 5 cm and pipe wall thickness of 6 mm. The pipe has a thermal conductivity of 17 W/m.K, and the inner pipe surface is at a uniform temperature of 120 °C. The temperature drop between the inlet and the exit of the pipe is 7 °C, and the constant pressure specific heat of vapor is 2190 J/kg.°C. If the air temperature in the manufacturing plant is 25°C, determine the heat transfer coefficient as a result if convection between the outer pipe surface and the surrounding air. T(r) = 120°C Superheated Air, 25°C r2 vapor r1 0.3 kg/s L = 10 m Tin-Tout = 7°C
In a dairy operation, milk at a flow rate of 0.25m3/hr and a cow-body temperature of 38.6°C must be chilled to a safe-to- store temperature of 13°C. Cold water at 2.2°C is available at a flow rate of 0.94m3/hr. The density and specific heat of milk are 1030 kg/m3 and 3860 J/kg.K, respectively. The density and specific heat of water is 1000 kg/m3 and 4187 J/kg.K. The chilling process is done by a double pipe counter-flow exchanger with an overall heat transfer coefficient U=1000 W/m2.K. The pipe of the heat exchanger has a 50-mm diameter with negligible thickness. Determine the pipe length L required. Select one: O a. 2.28 m O b. 4.28 m O c. 3.28 m O d. 1.28 m
water 4-26 Steel rods (p = 7832 kg/m³, c, = 434 J/kg-K, and k = 63.9 W/m-K) are heated in a furnace to 850°C and then quenched in a bath at 50°C for a period of 40 s as part of a hardening process. The convection heat transfer coefficient is 650 W/m²K. If the steel rods have diameter of 40 mm and length of 2 m, determine their average temperature when they are taken out of the water bath.
A hot dog can be considered to be a 12 cm long cylinder, whose diameter is 2 cm and whose properties are p = 980 kg/m3, cp = 3.9 kJ/kg · K, k =1.25 W/m · K, and a = 2 × 10–7 m2 /s. Consider a hot dog initially at 5 C which is dropped into boiling water at 100 C. The heat transfer coefficient at the surface of the hot dog is estimated to be 500 W/m2 · K and the hot dog can be considered to be cooked when its center temperature reaches 90 C.
Layers of 6-in-thick meat slabs (k = 0.26 Btu/h·ft·°F and a = 1.4 * 1026 ft2/s) initially at a uniform temperature of 50°F are cooled by refrigerated air at 23°F to a temperature of 36°F at their center in 12 h. Estimate the average heat transfer coefficient during this cooling process. Solve this problem using the Heisler charts.
steam exits the turbine of a steam power plant at 105 F and is to be condensed in a large condenser by cooling water flowing through copper pipes (k = 223 Btu/h-ft-F) of inner diameter 0.5 in. and outer diameter 0.7 in. at an average temperature of 70 F. The heat transfer of vaporization of water at 100F is 1037 Btu/lbm. The heat transfer coefficient are 1500 Btu/h-ft-F on the steam side and 35 Btu/h-ft-F on the water side. Determine the length of the tube required to condense steam at arate of 130 lbm/h.
K .1 Freshly harvested berries measuring 2 cm in diameter are chilled from 18°C to 7°C in a chiller at 2°C, with a surface heat transfer coefficient of 25 W/m2 K. They are then loaded in 250 kg batches into containers and held for 12 h in a cold store operating at 2°C prior to further processing. Each container weighs 50 kg. The cold store holds an average of 2.5 t of berries and measures 3 m high by 10 m  10 m. The walls and roof are insulated with 300 mm of polyurethane foam and the floor is constructed from 450 mm of concrete. The ambient air temperature in the factory averages 12°C and the soil temperature 9°C. An operator spends an average of 45 min per day moving the containers within the store and switches on four 100W lights when inside the store. Calculate the time required to cool the berries in the chiller and determine whether a 5-kW refrigeration unit using R-717 as refrigerant would be suitable for the cold store. The outside temperature is 20°C. Design the refrigeration…
In a ball bearing production facility, steel balls (k=50 W/m.K, c=0.460 kJ/kg.K, ρ=7865 kg/m3) that are each of 13,99 mm in diameter are annealed by first heating them to 870 oC and then slowly cooling in air to 125 oC. If the cooling air stream temperature is 60 oC, and it has a convective heat transfer coefficient of 35 W/m2.K), determine the time [s] required for the cooling.