Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470917855
Author: Bergman, Theodore L./
Publisher: John Wiley & Sons Inc
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Chapter 13, Problem 13.71P
A long, hemicylindrical (1-m radius) shaped furnace used to heat treat sheet metal products is comprised of three zones. The heating zone (1) is constructed from a ceramic plate of emissivity 0.85 and is operated at 1600 K by gas burners. The load zone (2) consists of sheet metal products, assumed to be black surfaces, that are to be maintained at 500 K. The refractory zone (3) is fabricated from insulating bricks having an emissivity of 0.6. Assume steady-state conditions, diffuse, gray surfaces, and negligible convection.
- What is (he heat rule per unit length of the furnace (normal to the page) that must be supplied by the gas burners for the prescribed conditions?
- What is the temperature of the insulating brick surface for the prescribed conditions?
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Students have asked these similar questions
A drying oven consists of a long semicircular duct of diameter D=1 m. Materials to be dried cover
the base of the oven while the wall is maintained at 1200 K. Length of the oven (into paper
direction) is 1 m. Water coated material is maintained at 325 K. Assume both the wall and the
material to be blackbodies.
(1) What is heat transfer rate?
(2) Given at temperature 325 K, water needs heat 2.378 × 106 J/kg in order to be dried (from
liquid water to steam). How much water can be dried per second based on the heat transfer rate
from (1)?
T₁ = 1200 K
T₂ = 325 K
— D = 1 m
D= m→
Question #9
A circular ceramic plate that can be modelled as a blackbody is being heated by an electrical
heater. The plate is 30cm in diameter and is situated in a surrounding ambient temperature
of 15°C where the natural convection heat transfer coefficient is 12W/m² K. The efficiency
of the electrical heater to transfer heat to the plate is 80%, the electric power is required
such that the heater needs to keep the surface temperature of the plate at 200°C.
Ambient 15°C Tsurr = 15°C
h = 12 W/m².K
Ceramic plate
-T₂ = 200°C
Welec
(A) Determine the heat emitted from the plate, as a blackbody.
(B) Determine the radiation incident on the plate from the surroundings.
(C) Determine the heat transfer from the plate to the surroundings.
(D) Determine the required electric power.
Keep in mind that both the bottom and top surfaces of the workpiece are exposed to radiation and convection. The workpiece is suspended in air in the furnace.
Chapter 13 Solutions
Fundamentals of Heat and Mass Transfer
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