Explanation Given information: Length of the cylindrical tip is 20 mm=0 .02m . Diameter of the cylindrical tip is 2.5 mm=0 .0025m . The temperature of cylindrical tip is 400 ° C=400+273=673K . The temperature of the surrounding air is 20 ° C=273+20=293K . The emissivity of cylindrical tip is =0 .8 . Convective heat transfer coefficient is 25W/m 2 .K Calculations: Surface area of cylindrical tip is = 2 π rh+ π r 2 . where, r = radius of cylindrical tip . h= lenth of cylindrical tip . 2 π rh+ π r 2 = ( 2 π × 0.00125 × 0.02 ) + ( π × 0.00125 2 ) = 0.00016 m 2 Rate of heat transfer by convection ( Q ) = hA s Δ T Where, ( Δ T ) = Temperature difference=(673-293)K=380K ( A s ) = Surface area of engine = 0.00016 m 2 ( h ) = Heat transfer coefficient=25W/m 2 .K ⇒ Q = hA s Δ T Putting the values in the equation, we get, ⇒ Q = 25 × 0

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ISBN: 9780073398198

Author: CENGEL

Publisher: RENT MCG

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Chapter 1, Problem 134P

To determine

The power required to maintain tip of soldering iron at 400°C .

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Chapter 1, Problem 133P

Chapter 1, Problem 135P

Chapter 1 Solutions

HEAT+MASS TRANSFER:FUND.+APPL.

Ch. 1 - How does the science of heat transfer differ from...Ch. 1 - What is the driving force for (a) heat transfer,...Ch. 1 - How do rating problems in heat transfer differ...Ch. 1 - What is the difference between the analytical and...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 - Prob. 9CP Ch. 1 - Prob. 10CP

Ch. 1 - Prob. 11CP Ch. 1 - An ideal gas is heated from 50C to 80C (a) at...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 - A 60-gallon water heated is initially filled with...Ch. 1 - Prob. 19P Ch. 1 - Prob. 20P 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 - A 5-m6-m8-m room is to be heated by an electrical...Ch. 1 - Prob. 28P Ch. 1 - Air enters the duct of an air-conditioning system...Ch. 1 - Prob. 30P Ch. 1 - Define thermal conductivity, and explain its...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 - 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? How do real bodies differ...Ch. 1 - A wood slab with a thickness 0.05 m is subjected...Ch. 1 - Prob. 49P Ch. 1 - Prob. 50EP Ch. 1 - The inner and outer surfaces of a 0.5-cm thick...Ch. 1 - Prob. 52P Ch. 1 - Prob. 53P Ch. 1 - The north wall of an electrically heated home is...Ch. 1 - Prob. 55P Ch. 1 - Prob. 56P Ch. 1 - Prob. 57P Ch. 1 - A concreate wall a surface area of 20 m2 and a...Ch. 1 - Prob. 59P Ch. 1 - Prob. 60P Ch. 1 - Prob. 61P Ch. 1 - Prob. 62EP Ch. 1 - Air at 20C with a convection heat transfer...Ch. 1 - Prob. 64P Ch. 1 - Prob. 65P Ch. 1 - Prob. 66P Ch. 1 - Prob. 67P Ch. 1 - Prob. 68P Ch. 1 - Prob. 69P Ch. 1 - Prob. 70P Ch. 1 - Prob. 71P Ch. 1 - Prob. 72EP Ch. 1 - Prob. 73P Ch. 1 - Prob. 74P Ch. 1 - Prob. 75P Ch. 1 - Prob. 76P Ch. 1 - Using the conversion factors between W and Btu/h,...Ch. 1 - The outer surface of a spacecraft in space has an...Ch. 1 - Consider a person whose expose surface are is 1.7...Ch. 1 - Prob. 80P Ch. 1 - Two surfaces, one highly polished and the other...Ch. 1 - A spherical interplanetary probe with a diameter...Ch. 1 - Prob. 83P Ch. 1 - Can all three modes of heat transfer occur...Ch. 1 - Can a medium involve (a) conduction and...Ch. 1 - The deep human body temperature of a healthy...Ch. 1 - We often turn the fan on in summer to help us...Ch. 1 - Prob. 88P Ch. 1 - Prob. 89P Ch. 1 - Prob. 90P Ch. 1 - An electronic package with a surface area of 1 m2...Ch. 1 - Consider steady heat transfer between two large...Ch. 1 - Prob. 93P Ch. 1 - Prob. 94P Ch. 1 - A 2-in-diameter spherical ball whose surface is...Ch. 1 - Prob. 96P Ch. 1 - Prob. 97P Ch. 1 - A 3-m-internal-diameter spherical tank made of...Ch. 1 - Prob. 99P Ch. 1 - Solar radiation is incident on a 5-m2 solar...Ch. 1 - Prob. 101P Ch. 1 - Prob. 102P Ch. 1 - Prob. 103EP Ch. 1 - An AISI 304 stainless steel sheet is going through...Ch. 1 - Prob. 105P Ch. 1 - Prob. 106P Ch. 1 - Prob. 107P Ch. 1 - Prob. 108CP Ch. 1 - Prob. 109P Ch. 1 - Prob. 110P Ch. 1 - Prob. 111P Ch. 1 - Prob. 112P Ch. 1 - Prob. 113CP Ch. 1 - Why is the metabolic rate of women, in general,...Ch. 1 - What is asymmetric thermal radiation How does it...Ch. 1 - How do (a) draft and (b) cold floor surfaces cause...Ch. 1 - Prob. 117CP Ch. 1 - Why is it necessary to ventilate buildings? What...Ch. 1 - Consider a house in Atlanta, Georgia, that is...Ch. 1 - Prob. 120P 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. 123P Ch. 1 - Prob. 124P 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. 129P Ch. 1 - Prob. 130P Ch. 1 - Prob. 131P Ch. 1 - Consider a person standing in a room maintained at...Ch. 1 - Prob. 133P Ch. 1 - Prob. 134P Ch. 1 - Prob. 135P Ch. 1 - Prob. 136P Ch. 1 - Prob. 137P Ch. 1 - Prob. 138P Ch. 1 - Prob. 139P Ch. 1 - Prob. 140P Ch. 1 - Prob. 141P Ch. 1 - Prob. 142P Ch. 1 - A 2-kW electric resistance heater submerged in...Ch. 1 - Prob. 144P Ch. 1 - A cold bottled drink (m=2.5kg,cp=4200J/kg.K) at...Ch. 1 - Prob. 146P Ch. 1 - Air enters a 12-m-long, 7-cm-diameter pipe at 50oC...Ch. 1 - Prob. 148P 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. 151P Ch. 1 - A 40-cm-long, 0.4-cm-diameter electric resistance...Ch. 1 - Prob. 153P Ch. 1 - Prob. 154P 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. 157P Ch. 1 - Prob. 158P 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 - 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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