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Chickens with an average mass of 1.7 kg
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Heat and Mass Transfer: Fundamentals and Applications
- Example: 0.5 kg of water per minute is heated from 20° to 40°C when passed through a tube of 2.5 cm diameter steel pipe. The pipe surface temperature is maintained at 110°C by condensing steam on its surface. Find out the length of the pipe required. The properties of water at mean temperature of 70°C are given below: p = 978 kg/m² k= 0.575 W/m. K Cp = 4200 J/kg. K v = 0.415 x 10-6 m²/secarrow_forward4-38 Carbon steel balls (p = 7833 kg/m2, k = 54 W/m K, c = 0.465 kJ/kg°C, and a 1.474 - 10-6 m2/s) 8 mm in diameter are annealed by heating them first to 900°C in a furnace and then page 300 allowing them to cool slowly to 100°C in ambient air at 35°C. If the average heat transfer coefficient is 75 W/m2-K, determine how long the annealing process will take. If 2500 balls are to be annealed per hour, determine the total rate of heat transfer from the balls to the ambient air. FIGURE P4-38 Air, 35°C Furnace Steel ball 100C 900°Carrow_forwardDuring a picnic on a hot summer day, the only available drinks were those at the ambient temperature of 90°F. In an effort to cool a 12-fluid-oz drink in a can, which is 5 in high and has a diameter of 2.5 in, a person grabs the can and starts shaking it in the iced water of the chest at 32°F. The temperature of the drink can be assumed to be uniform at all times, and the heat transfer coefficient between the iced water and the aluminum can is 30 Btu/h·ft2·°F. Using the properties of water for the drink, estimate how long it will take for the canned drink to cool to 40°F.arrow_forward
- The boiling temp of nitrogen at 1 atm is -196°C. If the temperature of liquid nitrogen in a tank open to the atmosphere at sea level will remain constant until it is depleted, then any heat transfer to the tank will result in the evaporation of some liquid nitrogen, which has a heat of vaporization of 198 kJ/kg and a density of 810 kg/m³ at 1 atm. Consider a 3.5-m-diameter spherical tank that is initially filled with liquid nitrogen at 1 atm and -196°C. The tank is exposed to ambient air at 16°C, with a convection heat transfer coefficient of 32 W/m2- °C. The temperature of the thin-shelled spherical tank is observed to be N2 vapor almost the same as the temperature of the nitrogen inside. Determine the rate of evaporation of the liquid nitrogen in the tank (in kg/s) as a result of I atm Liquid N3 -196°C heat transfer from the ambient air if the tank is (a) not insulated, (b) insulated with 6-cm thick fiberglass insulation (k=0.035 W/m-°C) and (c) insulated with 2-cm thick…arrow_forwardIn a manufacturing facility, 2-in-diameter brassballs (k = 64.1 Btu/h·ft·°F, r = 532 lbm/ft3, and cp =0.092 Btu/lbm·°F) initially at 250°F are quenched in a waterbath at 120°F for a period of 2 min at a rate of 120 ballsper minute. If the convection heat transfer coefficient is42 Btu/h·ft2·°F, determine (a) the temperature of the balls afterquenching and (b) the rate at which heat needs to be removedfrom the water in order to keep its temperature constant at120°F.arrow_forward10 kg of frozen chicken at an initial temperature of -20°C is to be thawed and raised to a temperature of 10°C before cooking. The freezing point of the meat is -1.7°C and the specific heats above and below the freezing point are 3.1 kJ/kg-K and 1.6 kJ/kg-K, respectively. The heat of fusion (the amount of heat needed per unit mass to thaw chicken at the freezing point) is 233 kJ/kg. Find the total amount of heat that must be transferred to complete this the process.arrow_forward
- The boiling temperature of oxygen at atmospheric pressure at sea level (1 atm) is -183ºC. Therefore, oxygen is used in low temperature scientific studies since the temperature of liquid oxygen in a tank open to the atmosphere remains constant at -183ºC until the liquid oxygen in the tank is depleted. Any heat transfer to the tank results in the evaporation of some liquid oxygen, which has a heat of vaporization of 213 kJ/kg and a density of 1140 kg/m3at 1 atm. Consider a 4 m diameter spherical tank initially filled with liquid oxygen at 1 atm and -183ºC. The tank is exosed to 20ºC ambient ait with a heat transfer coefficient of 25 W/m2. ºC. The temperature of the thin-shelled spherical tank is observed to be almost the same as the temperature of the oxygen inside. Disregarding any radiation heat exchange, determine the rate of evaporation of the liquid oxygen in the tank as a result of the heat transfer from the ambient airarrow_forwardA fabricated food, in the form of small spherical pellets, is to be frozen in an air-blast freezer. The air-blast freezer is operating with air at -30°C. The initial product temperature is 25°C. The pellets have a diameter of 1.2 cm, and the density of the product is 980 kg/m³ . The initial freezing temperature is -2.5°C. The latent heat of fusion for this 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/(m² °C). Calculate the freezing time (h)arrow_forwardA fabricated food, in the form of small spherical pellets, is to be frozen in an air-blast freezer. The air-blast freezer is operating with air at -30°C. The initial product temperature is 25°C. The pellets have a diameter of 1.2 cm, and the density of the product is 980 kg/m3 . The initial freezing temperature is -2.5°C. The latent heat of fusion for this 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/(m2°C). Calculate the freezing time.arrow_forward
- Oranges of 2.5-in-diameter (k= 0.26 Btu/h·ft·°F) and α= 1.4 10-6 ft2/s) initially at a uniform temperature of 78°F are to be cooled by refrigerated air at 25°F flowing at a velocity of 1 ft/s. The average heat transfer coefficient between the oranges and the air is experimentally determined to be 4.6 Btu/h·ft2·°F. Determine how long itwill take for the center temperature of the oranges to drop to 40°F. Use Heisler chart. Answer: 55.5 minarrow_forwardIn a production facility, 3-cm-thick large brass plates (k =110 W/m·K, ρ= 8530kg/m3, Cp = 380 J/kg·K, and α= 33.9 x10-6 m2/s) that are initially at a uniform temperature of 25°C are heated by passing them through an oven maintained at 700°C. The plates remain in the oven for a period of 10 min. Taking the convection heat transfer coefficient to be h = 80 W/m2·K, determine the surface temperature ofthe plates when they come out of the oven. Solve this problem using analytical oneterm approximation method (not the Heisler charts). Can this problem be solved using lumped system analysis? Justify your answer. Answer: 445 ℃arrow_forwardA 10 cm diameter aluminum ball is to be heated from 94°C to an average temperature of 140°C in 30 minutes. Taking the average density and specific heat of aluminum in this temperature range to be 2,700 kg/m3 and Cp = 0.91 kJ/kg-K, respectively, determine the ff: (Round off your final answers to two (2) decimal places.) (a) the total amount of heat transferred to the ball in kJ = (b) the average heat transfer rate to the aluminum ball in W = (c) the average heat flux in W/m2 =arrow_forward
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