Consider a surface of area A at which the convection and radiation heat transfer coefficients are hconv and hrad, respectively. Explain how you would determine (a) the single equivalent heat transfer coefficient and (b) the equivalent thermal resistance. Assume the medium and the surrounding surfaces are at the same temperature.

Consider a surface of area A at which the convection and radiation heat transfer coefficients are hconv and hrad, respectively. Explain how you would determine (a) the single equivalent heat transfer coefficient and (b) the equivalent thermal resistance. Assume the medium and the surrounding surfaces are at the same temperature.

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) 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?
Thermography is a technique for measuring radiant heat and detecting variations in surface temperatures that may be medically, environmentally, or militarily meaningful.(a) What is the percent increase in the rate of heat transfer by radiation from a given area at a temperature of 34.0C compared with that at 33.0C, such as on a person’s skin? (b) What is the percent increase in the rate of heat transfer by radiation from a given area at a temperature of 34.0C compared with that at 20.0C, such as for warm and cool automobile hoods?
Q3: Consider a spherical container of inner radius r1, outer radius r2, and thermal conductivity k. Express the boundary condition on the inner surface of the container for steady one dimensional conduction for the following cases: (a) specified temperature of 50°C, (b) specified heat flux of 30 w/m? toward the center, (c) convection to a medium at T with a heat transfer coefficient of h.
(a) Cherry-red embers in a fireplace are at 850C and have an exposed area of 0.200 m2 and an emissivity of 0.980. The surrounding room has a temperature of 18.0C. If 50% of the radiant energy enters the room, what is the net rate of radiant heat transfer in kilowatts? (b) Does your answer support the contention that most of the heat transfer into a room by a fireplace comes from infrared radiation?
Bob has a spherical tank with a 1 m internal diameter made of 6 cm thick stainless steel sitting in his garden workshop, which is used to hold clean water for the pond. The thermal conductivity coefficient and emissivity of the stainless steel are k = 20 W m-1° C-1 and ɛ = 1.0, respectively. Derive the following equation for the steady-state rate of heat transfer via conduction across a hollow spherical vessel where r; and r. are the inner and outer radius of the sphere, respectively, and k is the conductivity coefficient of the steel. 4tkr¡ro Qcond (TH – TL) (ro – ri)
What is the rate of heat transfer by radiation, with an unclothed person standing in a dark room whose ambient temperature is 22.0ºC . The person has a normal skin temperature of 33.0ºC and a surface area of 1.50 m2 . The emissivity of skin is 0.97 in the infrared, where the radiation takes place.
Consider a person standing in a room at 18°C. Determine the total rate of heat transfer from this person if the exposed surface area and the skin temperature of the person are 1.7 m2 and 32°C, respectively, and the convection heat transfer coefficient is 5 W/m2·K. Take the emissivity of the skin and the clothes to be 0.9, and assume the temperature of the inner surfaces of the room to be the same as the air temperature.
Hot air at 80°C is blown over a 2m x 4m flat surface at 30°C. If the average convection heat transfer coefficient is 55 W/m2-K, determine the rate of heat transfer from the air to the plate, in kW.
A flat-plate solar collector is used to heat water by having water flow through tubes attached at the back of the thin solar absorber plate. The absorber plate has a surface area of 2 m2 with emissivity and absorptivity of 0.9. The surface temperature of the absorber is 35°C, and solar radiation is incident on the absorber at 500 W/m2 with a surrounding temperature of 0°C. Convection heat transfer coefficient at the absorber surface is 5 W/m2∙K, while the ambient temperature is 25°C. Net heat rate absorbed by the solar collector heats the water from an inlet temperature (Tin) to an outlet temperature (Tout). If the water flow rate is 5 g/s with a specific heat of 4.2 kJ/kg∙K, determine the temperature rise of the water.
Geologists measure conductive heat flow out of the earth by drilling holes (a few hundred meters deep) and measuring the temperature as a function of depth. Suppose that in a certain location the temperature increases by 20°C per kilometer of depth and the thermal conductivity of the rock is 2.5 W/m·K. What is the rate of heat conduction per square meter in this location? Assuming that this value is typical of other locations over all of earth's surface, at approximately what rate is the earth losing heat via conduction? (The radius of the earth is 6400 km.)
The thermal conductivity of a sheet of rigid, extruded insulation is reported to be k = 0.029 W/mK. The measured temperature difference across a 20-mm-thick sheet of the material is T₁ T₂ = 10°C. - (a) What is the heat flux through a 2 m x 2 m sheet of the insulation? (b) What is the rate of heat transfer through the sheet of insulation?
Consider an opaque plate that is well insulated on the edges and it is heated at the bottom with an electric heater. The plate has an emissivity of 0.67, and is situated in an ambient surrounding temperature of 7°C where the natural convection heat transfer coefficient is 7 W/m2?K. To maintain a surface temperature of 80°C, the electric heater supplies 1000 W/m2 of uniform heat flux to the plate. Determine the radiosity of the plate under these conditions.