Explanation Given: The exposed surface area 2 m 2 . The surface temperature of the absorber is 35 ° C . The heat transfer coefficient is 5 W / m 2 ⋅ K . The emissivity of plate is 0.9 . The absorptivity of plate is 0.9 . The incident heat on plate is 500 W / m 2 . The surrounding temperature is 0 ° C . The ambient temperature is 25 ° C . The water flow rate is 5 g / sec . The specific heat of water is 4.2 kJ / kg ⋅ K . Concept used: Write the expression for newton's law of cooling. Q c o n v = h A ( T s − T ∞ ) ....... (1) Here, Q c o n v is the convective heat loss, h is the heat transfer coefficient, T s is the upper temperature of plate, T ∞ is the temperature of air and A is the area. Write the expression for absorbed power. Q a b s = α A Q i n c ...... (2) Here, Q a b s is the absorptive heat, Q i n c is incident heat, and α is the absorptivity. Write the expression for generated power. Q r a d = σ ε A ( T s 4 − T s u r r 4 ) ...... (3) Here, Q r a d is the radiation heat loss, σ is the Stephen Boltzmann's constant, ε is the emissivity, T s is the surface temperature, and T s u r r is the surrounding temperature. Write the expression for net heat absorbed by solar heat collector. Q n e t = Q a b s − Q c o n v − Q r a d ...... (4) Here Q n e t is total amount of heat loss. Write the expression for heat addition for water. Q n e t = m ˙ c p a ( Δ T ) Now write the expression for the temperature rise of water. Δ T = Q n e t m ˙ C p a ...... (5) Here, Q n e t is net heat, m ˙ rate of air flows, Δ T is the change in temperature, and c p a specific heat of water. Calculation: Convert ° C into Kelvin. 35 ° C = 273 + 35 ( 0 ° C 273 K ) = 308 K Convert ° C into Kelvin. 25 ° C = 273 + 25 ( 0 ° C 273 K ) = 298 K Convert ° C into Kelvin. 0 ° C = 273 + 0 ( 0 ° C 273 K ) = 273 K Substitute 5 W / m 2 ⋅ K for h , 35 ° C for T s , 25 ° C for T ∞ and 2 m 2 for A in equation (1)

Heat and Mass Transfer: Fundamentals and Applications

5th Edition

ISBN: 9780073398181

Author: Yunus A. Cengel Dr., Afshin J. Ghajar

Publisher: McGraw-Hill Education

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Chapter 1, Problem 106P

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The rise in temperature of water.

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Chapter 1 Solutions

Heat and Mass Transfer: Fundamentals and Applications

Ch. 1 - How does the science of heat transfer differ from...Ch. 1 - What is the driving force for (a) heat transfer,...Ch. 1 - Prob. 3CP Ch. 1 - How do rating problems in heat transfer differ...Ch. 1 - What is the difference between the analytical and...Ch. 1 - Prob. 6CP Ch. 1 - What is the importance of modeling in engineering?...Ch. 1 - When modeling an engineering process, how is the...Ch. 1 - On a hot summer day, a student turns his fan on...Ch. 1 - Consider two identical rooms, one with a...

Ch. 1 - An ideal gas is heated from 50C to 80C (a) at...Ch. 1 - Prob. 12CP Ch. 1 - What is heat flux? How is it related to the heat...Ch. 1 - What are the mechanisms of energy transfer to a...Ch. 1 - A logic chip used in a computer dissipates 3 W of...Ch. 1 - Consider a 150-W incandescent lamp. The filament...Ch. 1 - A 15-cm-diameter aluminum ball is to be heated...Ch. 1 - Prob. 18P Ch. 1 - Prob. 19P Ch. 1 - A 60-gallon water heated is initially filled with...Ch. 1 - Prob. 21P Ch. 1 - Prob. 22P Ch. 1 - Prob. 23P Ch. 1 - Prob. 24P Ch. 1 - Prob. 25P Ch. 1 - Prob. 26P Ch. 1 - Prob. 27P Ch. 1 - Prob. 28P Ch. 1 - A 5-m6-m8-m room is to be heated by an electrical...Ch. 1 - Prob. 30P Ch. 1 - Prob. 31P Ch. 1 - Air enters the duct of an air-conditioning system...Ch. 1 - Define thermal conductivity, and explain its...Ch. 1 - Prob. 34CP Ch. 1 - Which is a better heat conductor, diamond or...Ch. 1 - How do the thermal conductivity of gases and...Ch. 1 - Why is the thermal conductivity of superinsulation...Ch. 1 - Why do we characterize the heat conduction ability...Ch. 1 - Prob. 39CP Ch. 1 - What are the mechanisms of heat transfer? How are...Ch. 1 - Write down the expression for the physical laws...Ch. 1 - How does heat conduction differ from convection?Ch. 1 - Does any of the energy of the sun reach the earth...Ch. 1 - How does forced convection differ from natural...Ch. 1 - What is the physical mechanism of heat conduction...Ch. 1 - Consider heat transfer a windowless wall of house...Ch. 1 - Consider heat loss through two walls of house on a...Ch. 1 - Consider two houses that are identical except that...Ch. 1 - Consider two walls of a house that are identical...Ch. 1 - Define emissivity and absorptivity. What is...Ch. 1 - What is a blackbody? 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What...Ch. 1 - Consider a house in Atlanta, Georgia, that is...Ch. 1 - Prob. 124P Ch. 1 - Prob. 125P Ch. 1 - Prob. 126P Ch. 1 - A 4m5m6m and room is to be heated by one ton (1000...Ch. 1 - Engine valves (cp=440J/kg.Kandp=7840kg/m3) are to...Ch. 1 - Prob. 129P Ch. 1 - Prob. 130P Ch. 1 - A 0.3 -cm-thick, 12-cm-high, and 18-cm-long...Ch. 1 - A 40-cm-long, 800-W electric resistance heating...Ch. 1 - It is well known that wind makes the cold air feel...Ch. 1 - An engine block with a surface area measured to be...Ch. 1 - Prob. 135P Ch. 1 - Prob. 136P Ch. 1 - Prob. 137P Ch. 1 - Consider a person standing in a room maintained at...Ch. 1 - Prob. 139P Ch. 1 - Prob. 140P Ch. 1 - Prob. 141P Ch. 1 - Prob. 142P Ch. 1 - Prob. 143P Ch. 1 - Prob. 144P Ch. 1 - Prob. 145P Ch. 1 - Prob. 146P Ch. 1 - A 2-kW electric resistance heater submerged in...Ch. 1 - Prob. 148P Ch. 1 - A cold bottled drink (m=2.5kg,cp=4200J/kg.K) at...Ch. 1 - Prob. 150P Ch. 1 - Air enters a 12-m-long, 7-cm-diameter pipe at 50oC...Ch. 1 - Prob. 152P Ch. 1 - Steady heat conduction occurs through a...Ch. 1 - Heat is lost through a brick wall (k=0.72W/m.K),...Ch. 1 - Prob. 155P Ch. 1 - A 40-cm-long, 0.4-cm-diameter electric resistance...Ch. 1 - Prob. 157P Ch. 1 - Over 90 percent of the energy dissipated by an...Ch. 1 - On a still, cleat night, the sky appears to be a...Ch. 1 - Prob. 160P Ch. 1 - Prob. 161P Ch. 1 - A persons head can be approximated as a...Ch. 1 - A person standing in a room loses heat to the air...Ch. 1 - Prob. 164P Ch. 1 - Write an essay on how microwave ovens work, and...Ch. 1 - Using information form the utility bill for the...Ch. 1 - It is well know that at the same outdoor air...

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