A composite plane wall consists of a L, = 75 mm thick layer of insulation ( k; = 0.05 W/m-K) and a L, = 25 mm thick layer of siding (k; = 0.10 W/m-K). The inner temperature of the insulation is 20°C. The outer temperature of the siding is -10°C. Steady state conditions apply. Determine the temperature at the interface between the two layers, in °C, and the rate of heat transfer through the wall, in W per m? of surface area.

A composite plane wall consists of a L, = 75 mm thick layer of insulation ( k; = 0.05 W/m-K) and a L, = 25 mm thick layer of siding (k; = 0.10 W/m-K). The inner temperature of the insulation is 20°C. The outer temperature of the siding is -10°C. Steady state conditions apply. Determine the temperature at the interface between the two layers, in °C, and the rate of heat transfer through the wall, in W per m? of surface area.

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter1: Temperature And Heat

Section: Chapter Questions

Problem 95P: (a) What is the rate of heat conduction through the 3.00-cm-thick fur of a large animal having a I...

See similar textbooks

Similar questions

(a) The inside of a hollow cylinder is maintained at a temperature Ta, and the outside is at a lower temperature, Tb (Fig. P19.45). The wall of the cylinder has a thermal conductivity k. Ignoring end effects, show that the rate of energy conduction from the inner surface to the outer surface in the radial direction is dQdt=2Lk[TaTbln(b/a)] Suggestions: The temperature gradient is dT/dr. A radial energy current passes through a concentric cylinder of area 2rL. (b) The passenger section of a jet airliner is in the shape of a cylindrical tube with a length of 35.0 m and an inner radius of 2.50 m. Its walls are lined with an insulating material 6.00 cm in thickness and having a thermal conductivity of 4.00 105 cal/s cm C. A heater must maintain the interior temperature at 25.0C while the outside temperature is 35.0C. What power must be supplied to the heater? Figure P19.45
(a) What is the rate of heat conduction through the 3.00-cm-thick fur of a large animal having a I .40-m surface area? Assume that the animal's skin temperature is 32.0 , that the air temperature is 5.00 , and that has the same thermal conductivity as air. (b) What food intake will the animal need in one day to replace this heat transfer?
A steam pipe is covered with 1.50-cm thick insulating material of thermal conductivity of 0.200 cal/cm · °C · s. How much energy is lost every second when the steam is at 250°C and the surrounding air is at 20.0°C? The pipe has a circumference of 800 cm and a length of 64.0 m. Neglect losses through the ends of the pipe. ?MW
A walrus transfers energy by conduction through its blubber at the rate of 150 W when immersed in −1.00ºC water. The walrus’s internal core temperature is 37.0ºC , and it has a surface area of 2.00 m2 . What is the average thickness of its blubber, which has the conductivity of fatty tissues without blood?
A metal plate 4.00 mm thick has a temperature difference of 32.0°C between 6. A metal plate 4.00 mm thick has a temperature difference of 32.0°C between its faces. It transmits 200 kcal/h through an area of 5.00 cm. Calculate the its faces. It transmits 200 kcal/h through an area of 5.00 cm. Calculate the thermal conductivity of this metal in W/m K.
A steam pipe is covered with 1.25 cm thick insulating material of thermal conductivity 0.200 W / m. ° C. How much energy is lost every second when the steam is at 200 ° C and the surrounding air is at 20 ° C? The pipe has a circumference of 950 cm and a length of 68 m. Neglect losses through the ends of the pipe.
A carpenter builds an exterior house wall with a layerof wood 3.0 cm thick on the outside and a layer of Styrofoam insulation2.2 cm thick on the inside wall surface. The wood hask = 0.080 W/m . K, and the Styrofoam has k = 0.027 W /m . K. Theinterior surface temperature is 19.0°C, and the exterior surface temperatureis -10.0°C. (a) What is the temperature at the plane wherethe wood meets the Styrofoam? (b) What is the rate of heat flow persquare meter through this wall?
Hot oil is to be cooled by water in a one-shell-pass and eight-tube-passes heat exchanger. The tubes are thin-walled and are made of copper with an internal diameter of 1.4 cm. The length of each tube pass in the heat exchanger is 5 m, and the overall heat transfer coefficient is 310 W/m2?K. Water flows through the tubes at a rate of 0.2 kg/s, and the oil through the shell at a rate of 0.3 kg/s. The water and the oil enter at temperatures of 20°C and 150°C, respectively. Determine the rate of heat transfer in the heat exchanger and the outlet temperatures of the water and the oil.
In an electrically heated home, the temperature of the ground in contact with a concrete basement wall is 10.3 oC. The temperature at the inside surface of the wall is 18.1 oC. The wall is 0.14 m thick and has an area of 6.5 m2. Assume that one kilowatt hour of electrical energy costs $0.10. How many hours are required for one dollar's worth of energy to be conducted through the wall?
The thermal conductivities of human tissues vary greatly. Fat and skin have conductivities of about 0.20 W/m . K and 0.020 W/m . K, respectively, while other tissues inside the body have conductivities of about 0.50 W/m . K. Assume that between the core region of the body and the skin surface lies a skin layer of 1.0 mm, fat layer of 0.50 cm, and 3.2 cm of other tissues. (a) Find the R-factor for each of these layers, and the equivalent R-factor for all layers taken together, retaining two digits. (b) Find the rate of energy loss when the core temperature is 37°C and the exterior temperature is 0°C. Assume that both a protective layer of clothing and an insulating layer of unmoving air are absent, and a body area of 2.0 m2.
A large steam pipe is covered with a 4.80 cm thick insulating material with a thermal conductivity of 0.17 W/(m°C). How much energy is lost every second when the temperature of the steam inside the pipe is at 265 °C and the temperature outside of the pipe is 13.0 °C? The pipe has a diameter of 3.70 m and a length of 185 m. Neglect losses through the ends of the pipe. 3863.3 J
A steam pipe is covered with 1.50-cm-thick insulating material of thermal conductivity 0.200 cal/cm . °C . s. How much energy is lost every second when the steam is at 200.°C and the surrounding air is at 20.0°C? The pipe has a circumference of 800. cm and a length of 50.0 m. Neglect losses through the ends of the pipe.