Explanation Given information: The average temperature of the hot water is 85 ° C , the length of the pipe is 4 m , the outer diameter of the pipe is 3 cm , the medium temperature is 32 ° C , the thermal conductivity of the concrete wall is 0.75 W/m ⋅ K , the heat transfer coefficient is 12 W/m 2 ⋅ K , the height of the concrete wall is 4 m , the length of the concrete wall is 8 m and the thickness of the concrete wall is 15 cm . Write the expression for the shape factor. F = 2 π l ln ( 4 t π d ) ....... (I) Here, the shape factor is F , the length of the pipe is l , the thickness of the wall is t and the diameter of the pipe is d . Write the expression for the rate of heat loss from the hot water. Q = 8 F k ( T h − T ∞ ) ....... (II) Here, the shape factor is F , the thermal conductivity of the concrete wall is k , the temperature of the hot water is T h and the temperature of the medium is T ∞ . Write the expression for the surface area of the wall. A = 2 × H × L ....... (III) Here, the surface areaof the wall is A , the height of the concrete wall is H and the length of the concrete wall is L Write the expression for the rate of heat transfer due to convection from outside of the concrete wall to medium. Q = h A ( T s − T ∞ ) T s = T ∞ + Q h A ....... (IV) Here, the rate of heat transfer is Q , the medium temperature is T ∞ , the heat transfer coefficient is h , the surface temperature of the wall is T s and the surface area of the wall is A . Calculation: Substitute 4 m for l , 15 cm for t and 3 cm for d in Equation (I). F = 2 π ( 4 m ) ln ( 4 ( 15 cm ) π ( 3 cm ) ) = 2 π ( 4 m ) ln ( 4 ( 15 cm ( 1 m 100 cm ) ) π ( 3 cm ( 1 m 100 cm ) ) ) = 13

5th Edition

ISBN: 9781307573060

Author: CENGEL

Publisher: MCG/CREATE

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Question

Chapter 3, Problem 148P

To determine

The rate of heat loss from the hot water and the surface temperature of the wall.

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Chapter 3, Problem 147P

Chapter 3, Problem 149P

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Chapter 3 Solutions

HEAT+MASS TRANSFER-SI ED. EBOOK >I<

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