FUND.OF HEAT+MASS TRANSFER(LL) >CUSTOM<
FUND.OF HEAT+MASS TRANSFER(LL) >CUSTOM<
5th Edition
ISBN: 9781260163124
Author: CENGEL
Publisher: MCG CUSTOM
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Chapter 1, Problem 89P
To determine

The case for which energy required will be greater.

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7.Consider a person standing in a room maintained at 20°C at all times. The inner surfaces of the walls, floors, and ceiling of the house are observed to be at an average temperature of 12°C in winter and 23°C in summer. Determine the rates of radiation heat transfer between this person and the surrounding surfaces in both summer and winter if the exposed surface area, emissivity, and the average outer surface temperature of the person are 1.6 m2, 0.95, and 32°C, respectively.
2. (a)   Consider a 25-cm-diameter spherical ball at 700 K suspended in air and assume the emissivity of the ball to be ε=0.95.                     Calculate:       (i) the total emissive power in kW/m2;                                                (ii) the total amount of radiation emitted by the ball in 3 minutes.                     (b)   The inner and outer surfaces of a 25-cm-thick wall are at 27 oC and 45 oC, respectively. The outer surface of the wall exchanges heat by radiation with surrounding surfaces at 40 oC, and convection with ambient air at 42 oC with convection heat transfer coefficient of 9.0 W/m2 K. Solar radiation incident on the surface is at a rate of 150 W/m2. If the emissivity and the solar absorptivity of the outer surface are 0.75 and 0.85, respectively:                 (i) write the expression of the energy balance at the outer surface;…
4: Consider a person standing in a room maintained at 20°C at all times. The inner surfaces of the walls, floors, and ceiling of the house are observed to be at an average temperature of 12°C in winter and 23°C in summer. Determine the rates of radiation heat transfer between this person and the surrounding surfaces in both summer and winter if the exposed surface area, emissivity, and the average outer surface temperature of the person are 1.6 m2, 0.95, and 32°C, respectively.

Chapter 1 Solutions

FUND.OF HEAT+MASS TRANSFER(LL) >CUSTOM<

Ch. 1 - An ideal gas is heated from 50C to 80C (a) at...Ch. 1 - Prob. 12CPCh. 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. 18PCh. 1 - Prob. 19PCh. 1 - A 60-gallon water heated is initially filled with...Ch. 1 - Prob. 21PCh. 1 - Prob. 22PCh. 1 - Prob. 23PCh. 1 - Prob. 24PCh. 1 - Prob. 25PCh. 1 - Prob. 26PCh. 1 - Prob. 27PCh. 1 - Prob. 28PCh. 1 - A 5-m6-m8-m room is to be heated by an electrical...Ch. 1 - Prob. 30PCh. 1 - Prob. 31PCh. 1 - Air enters the duct of an air-conditioning system...Ch. 1 - Define thermal conductivity, and explain its...Ch. 1 - Prob. 34CPCh. 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. 39CPCh. 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. 53PCh. 1 - The inner and outer surfaces of a 0.5-cm thick...Ch. 1 - Prob. 55PCh. 1 - Prob. 56PCh. 1 - The north wall of an electrically heated home is...Ch. 1 - Prob. 58PCh. 1 - Prob. 59PCh. 1 - Prob. 60PCh. 1 - A concreate wall a surface area of 20 m2 and a...Ch. 1 - Prob. 62PCh. 1 - Prob. 63PCh. 1 - Prob. 64EPCh. 1 - Prob. 65EPCh. 1 - Air at 20C with a convection heat transfer...Ch. 1 - Prob. 67PCh. 1 - Prob. 68PCh. 1 - Prob. 69PCh. 1 - Prob. 70PCh. 1 - Prob. 71PCh. 1 - Prob. 72PCh. 1 - Prob. 73PCh. 1 - Prob. 74PCh. 1 - Prob. 75PCh. 1 - Prob. 76EPCh. 1 - Prob. 77EPCh. 1 - Prob. 78PCh. 1 - Prob. 79PCh. 1 - Prob. 80PCh. 1 - Prob. 81PCh. 1 - Prob. 82PCh. 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. 86PCh. 1 - Two surfaces, one highly polished and the other...Ch. 1 - A spherical interplanetary probe with a diameter...Ch. 1 - Prob. 89PCh. 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. 94PCh. 1 - Prob. 95PCh. 1 - Prob. 96PCh. 1 - An electronic package with a surface area of 1 m2...Ch. 1 - Consider steady heat transfer between two large...Ch. 1 - Prob. 99PCh. 1 - Prob. 100PCh. 1 - A 2-in-diameter spherical ball whose surface is...Ch. 1 - Prob. 102PCh. 1 - A 3-m-internal-diameter spherical tank made of...Ch. 1 - Prob. 104PCh. 1 - Solar radiation is incident on a 5-m2 solar...Ch. 1 - Prob. 106PCh. 1 - Prob. 107PCh. 1 - Prob. 108PCh. 1 - Prob. 109EPCh. 1 - An AISI 304 stainless steel sheet is going through...Ch. 1 - Prob. 111PCh. 1 - Prob. 112CPCh. 1 - Prob. 113PCh. 1 - Prob. 114PCh. 1 - Prob. 115PCh. 1 - Prob. 116PCh. 1 - Prob. 117PCh. 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. 121CPCh. 1 - Why is it necessary to ventilate buildings? What...Ch. 1 - Consider a house in Atlanta, Georgia, that is...Ch. 1 - Prob. 124PCh. 1 - Prob. 125PCh. 1 - Prob. 126PCh. 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. 129PCh. 1 - Prob. 130PCh. 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. 135PCh. 1 - Prob. 136PCh. 1 - Prob. 137PCh. 1 - Consider a person standing in a room maintained at...Ch. 1 - Prob. 139PCh. 1 - Prob. 140PCh. 1 - Prob. 141PCh. 1 - Prob. 142PCh. 1 - Prob. 143PCh. 1 - Prob. 144PCh. 1 - Prob. 145PCh. 1 - Prob. 146PCh. 1 - A 2-kW electric resistance heater submerged in...Ch. 1 - Prob. 148PCh. 1 - A cold bottled drink (m=2.5kg,cp=4200J/kg.K) at...Ch. 1 - Prob. 150PCh. 1 - Air enters a 12-m-long, 7-cm-diameter pipe at 50oC...Ch. 1 - Prob. 152PCh. 1 - Steady heat conduction occurs through a...Ch. 1 - Heat is lost through a brick wall (k=0.72W/m.K),...Ch. 1 - Prob. 155PCh. 1 - A 40-cm-long, 0.4-cm-diameter electric resistance...Ch. 1 - Prob. 157PCh. 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. 160PCh. 1 - Prob. 161PCh. 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. 164PCh. 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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    Calculate the total heat gain of a restaurant at its peak occupancy load at about 1PM. When hundred dinners and 15 employees are present, Given: Heat gain through wall and roof: 2500Kj/hr; Heat gain through glass areas:500Kj; Number of florescent tube lights:60; Rating of each tube light:40W; Rating of toasters inside space:2650W; Sensible heat gain per dinner:250Kj/hr; Latent heat gain per dinner: 260Kj/hr Sensible heat per employee:305Kj/hr Latent heat per employee:545Kj/hr Inside design conditions:25 oC DB, 19 oC WB Outside design conditions: 40 oC DB, 27 oCWB Ventilation requirement: 0.4cmm/person
    Two parallel discs pf 1m diameter are situated 2m part in surroundings at a temparature 20 C. The inner side of one disc has an emissivity of 0.5 and is manintained at 500 C by electric resistance heating and the outer side of the disc is well insulated. The other disc is  Two parallel discs of 1m diameter are situated 2m apart in surroundings at a temperature of 20 oC. The inner side of one disc has an emissivity of 0.5 and is maintained at 500 oC by electric resistance heating and the outer side of the disc is well insulated. The other disc is open to radiation on both sides and reaches an equilibrium temperature. Calculate this equilibrium temperature and the heat flow rate from the first disc, assuming heat transfer is entirely by radiation.
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