A long 8-cm thick rectangular plate made of stainless steel at 304 (k= 12.9W/mk, ? = 7900 Kg/m3, C, = 477 J/kgK and a = 3.95 x 10-6 m²/s) comes out of an oven at a uniform temperature of 500°C. The plate is then allowed to cool slowly in a chamber at 150°C with an average convection heat transfer coefficient of h = 60 W/m²K. Determine the temperature at the center of the plate 120 min after the start of the cooling process.

A long 8-cm thick rectangular plate made of stainless steel at 304 (k= 12.9W/mk, ? = 7900 Kg/m3, C, = 477 J/kgK and a = 3.95 x 10-6 m²/s) comes out of an oven at a uniform temperature of 500°C. The plate is then allowed to cool slowly in a chamber at 150°C with an average convection heat transfer coefficient of h = 60 W/m²K. Determine the temperature at the center of the plate 120 min after the start of the cooling process.

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

Number 3A food product with 73% moisture content in a 7 cm diameter can wants to be frozen. The density of the product is 970 kg/m³, the thermal conductivity is 1.2W/(m K), and the initial freezing temperature is -2.5°C. After 11 hours in the freezing medium -40°C, the product temperature becomes -10°C. Estimate the convection heat transfer coefficient of the freezing medium. Assume the can as an infinite cylinder. h= answer in W/(m²K)
An ordinary egg can be approximated as a 5.5-cm-diameter sphere whose properties are roughly k=0.6 W/m.oC and a=0.14 x 10-6 m2/s. The egg is initially at a uniform temperature of 8 oC and is dropped into boiling water at 97 oC. Taking the convection heat transfer coefficient to be h=1400 W/m2.oC, determine how long it will take for the center of the egg to reach 70oC.
A pure copper cube 3 cm on each side is placed in a 15°C stream of water.If the initial temperature of the cube is initially at 215°C, how long does it take the cube to drop to 25°C? The convective heat transfer coefficient is 80W/m2∙K. Justify any assumptions.
Consider a house that is maintained at a constanttemperature of 22°C. One of the walls of the house has threesingle-pane glass windows that are 1.5 m high and 1.8 mlong. The glass (k = 0.78 W/m·K) is 0.5 cm thick, and theheat transfer coefficient on the inner surface of the glass is8 W/m2·K. Now winds at 35 km/h start to blow parallel to thesurface of this wall. If the air temperature outside is -2°C,determine the rate of heat loss through the windows of thiswall. Assume radiation heat transfer to be negligible. Evaluatethe air properties at a film temperature of 5°C and 1 atm.
A person puts a few apples into the freezer at 215°C tocool them quickly for guests who are about to arrive. Initially,the apples are at a uniform temperature of 20°C, and the heattransfer coefficient on the surfaces is 8 W/m2·K. Treating theapples as 9-cm-diameter spheres and taking their properties tobe r = 840 kg/m3, cp = 3.81 kJ/kg·K, k = 0.418 W/m·K, anda = 1.3 * 1027 m2/s, determine the center and surface temperaturesof the apples in 1 h. Also, determine the amount ofheat transfer from each apple. Solve this problem using analyticalone-term approximation method (not the Heisler charts).
A long 35-cm-diameter cylindrical shaft made of stainless steel 304 (k = 14.9 W/m·K, r = 7900 kg/m3, cp = 477 J/kg·K, and a 5 3.95 * 10-6 m2/s) comes out of an oven at a uniform temperature of 400°C. The shaft is then allowed to cool slowly in a chamber at 150°C with an average convection heat transfer coefficient of h = 60 W/m2·K. Determine the temperature at the center of the shaft 20 min after the start of the cooling process. Also, determine the heat transfer per unit length of the shaft during this time period. Solve this problem using analytical one-term approximation method (not the Heisler charts).
In a power plant, pipes transporting superheated vapor are very common. In a certain plant, superheated vapor is flowing at a rate of 0.3 kg/s inside a 5 cm diameter pipe of 10 m length. The air in the plant is maintained at 20oC while the surface temperature of the pipe is 100oC. If the temperature drop between the inlet and exit of the pipe is 30oC and the specific heat capacity of the vapor is 2190 kJ/kg.K, determine the convective heat transfer coefficient at the pipe surface. If necessary, how could this coefficient be increased?
Layers of 23-cm-thick meat slabs (k =0.47 W/m · °C) and α= 0.13x 10-6 m2/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/m2· °C. Assuming the size of the meat slabs to be largerelative 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. Answer: 22.1 h, -26.9 ℃
Q4: A spherical object that is made of a material with specific heat=383 J/kg K , and density = 8954 kg/m’. The diameter of the sphere is 5-cm and it is initially at a uniform temperature of 150¢C. It is suddenly exposed to an environment at 20-C having a heat-transfer coefficient h=28W/m? -
A concrete wall of 16.44 cm thickness (k = 1.37 W / mC,? = 7x10-7 m2 / s) having a uniform temperature of 54 C in the beginning was suddenly exposed to the air flow at 10C. The convection heat transfer coefficient of air is 10 W / m2C and after a certain time, find the time taken for the center temperature of the wall to be 30 C (minutes).
A person is found dead at 5PM in a room whose temperature is 20°C. Thetemperature of the body is measured to be 25°C when found, Modeling thebody as a 30-cm-diameter, 1.70-m-long cylinder and the heat transfer coefficient estimated to be 8 W/m2·K. and using the lumped system analysis as a rough approximation, estimate the time of death of the person.
A cylindrical body having 10 cm diameter and lenth of 30 cm passes through a heat treatment furnace which is 6 m in length. The body must reach a temperature of 800°C before it comes out of the furnace. The furnace gas is at 1250°C and body initial temperature is 90°C. How much time it will take to attain the required temperature ? Take h = 100 W/m² °C. Take K(steel) = 40 W/m°C and a (thermal diffusivity of steel) = 1.16 x 10-5 m²/s.