PLEASE ANSWER ALL OF THIS QUESTION ASAP!!! HEAT CONDUCTION ON PLANE WALLS15. A composite slab is made from three layers of 15 cm, 10 cm and 12 cmthickness. The first layer is of material with thermal conductivity 1.45 W/m-K for 60% of the area and the rest is of material with conductivity of 2.5W/m-K. The second layer is made of material with conductivity of 12.5 W/m-K for 50% area and of material with conductivity 18.5 W/m-K is used for theother 50% of the area. The third layer is of single material of thermalconductivity 0.76 W/m- K. The slab is exposed on one side to warm air at26°C and to cold air at -20°C on the other side. The convection heat transfercoefficients are 15 and 20 W/m²-K on the inside and outside surfaces,respectively. Determine the heat transfer per unit area.

Givenlayer 1t1=15cm =0.15mk1=1.45W/mK with A1=60%k2=2.5W/mK with A2=100-60=40%layer 2t2=10cm…

HEAT CONDUCTION ON PLANE WALLS 15. A composite slab is made from three layers of 15 cm, 10 cm and 12 c thickness. The first layer is of material with thermal conductivity 1.45 W/n K for 60% of the area and the rest is of material with conductivity of 2. W/m-K. The second layer is made of material with conductivity of 12.5 W/m

HEAT CONDUCTION ON PLANE WALLS 15. A composite slab is made from three layers of 15 cm, 10 cm and 12 c thickness. The first layer is of material with thermal conductivity 1.45 W/n K for 60% of the area and the rest is of material with conductivity of 2. W/m-K. The second layer is made of material with conductivity of 12.5 W/m

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.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.64P: The interior wall of a large, commercial walk-in type meat freezer is covered under normal operating...

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1.37 Mild steel nails were driven through a solid wood wall consisting of two layers, each 2.5-cm thick, for reinforcement. If the total cross-sectional area of the nails is 0.5% of the wall area, determine the unit thermal conductance of the composite wall and the percent of the total heat flow that passes through the nails when the temperature difference across the wall is 25°C. Neglect contact resistance between the wood layers.
3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on one side is and on the other side is . If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it takes for the copper plate to reach a temperature of 82°C.
A steam pipe 200 mm in diameter passes through a large basement room. The temperature of the pipe wall is 500C, while that of the ambient air in the room is 20C. Determine the heat transfer rate by convection and radiation per unit length of steam pipe if the emissivity of the pipe surface is 0.8 and the natural convection heat transfer coefficient has been determined to be 10 W/m2K.
A high-speed computer is located in a temperature-controlled room at 26C. When the machine is operating, its internal heat generation rate is estimated to be 800 W. The external surface temperature of the computer is to be maintained below 85C. The heat transfer coefficient for the surface of the computer is estimated to be 10W/m2K. What surface area would be necessary to assure safe operation of this machine? Comment on ways to reduce this area.
An electronic device that internally generates 600 mW of heat has a maximum permissible operating temperature of 70C. It is to be cooled in 25C air by attaching aluminum fins with a total surface area of 12cm2. The convection heat transfer coefficient between the fins and the air is 20W/m2K. Estimate the operating temperature when the fins are attached in such a way that (a) there is a contact resistance of approximately 50 K/W between the surface of the device and the fin array and (b) there is no contact resistance (in this case, the construction of the device is more expensive). Comment on the design options.
2.9 In a large chemical factory, hot gases at 2273 K are cooled by a liquid at 373 K with gas-side and liquid-side convection heat transfer coefficients of 50 and , respectively. The wall that separates the gas and liquid streams is composed of a 2-cm thick oxide layer on the gas side and a 4-cm thick slab of stainless steel on the liquid side. There is a contact resistance between the oxide layer and the steel of . Determine the rate of heat loss from hot gases through the composite wall to the liquid.
1.19 A cryogenic fluid is stored in a 0.3-m-diameter spherical container is still air. If the convection heat transfer coefficient between the outer surface of the container and the air is 6.8 , the temperature of the air is 27°C, and the temperature of the surface of the sphere is –183°C, determine the rate of heat transfer by convection.
3.17 A 1.4-kg aluminum household iron has a 500-W heating element. The surface area is . The ambient temperature is 21°C, and the surface heat transfer coefficient is . How long after the iron is plugged in does its temperature reach 104°C?
2.29 In a cylindrical fuel rod of a nuclear reactor, heat is generated internally according to the equation where = local rate of heat generation per unit volume at r = outside radius = rate of heat generation per unit volume at the centerline Calculate the temperature drop from the centerline to the surface for a 2.5-cm-diameter rod having a thermal conductivity of if the rate of heat removal from its surface is 1.6 .
One end of a 0.3-m-long steel rod is connected to a wall at 204C. The other end is connected to a wall that is maintained at 93C. Air is blown across the rod so that a heat transfer coefficient of 17W/m2 K is maintained over the entire surface. If the diameter of the rod is 5 cm and the temperature of the air is 38C, what is the net rate of heat loss to the air?