Fundamentals Of Thermal-fluid Sciences In Si Units
5th Edition
ISBN: 9789814720953
Author: Yunus Cengel, Robert Turner, John Cimbala
Publisher: McGraw-Hill Education
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Chapter 16, Problem 12P
To determine
The difference between forced convection and natural convection.
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Chapter 16 Solutions
Fundamentals Of Thermal-fluid Sciences In Si Units
Ch. 16 - Prob. 1PCh. 16 - Judging from its unit W/m·K, can we define thermal...Ch. 16 - Which is a better heat conductor, diamond or...Ch. 16 - How do the thermal conductivity of gases and...Ch. 16 - Why is the thermal conductivity of superinsulation...Ch. 16 - Why do we characterize the heat conduction ability...Ch. 16 - Consider an alloy of two metals whose thermal...Ch. 16 - What are the mechanisms of heat transfer? How are...Ch. 16 - Write down the expressions for the physical laws...Ch. 16 - How does heat conduction differ from convection?
Ch. 16 - Does any of the energy of the sun reach the earth...Ch. 16 - How does forced convection differ from natural...Ch. 16 - What is the physical mechanism of heat conduction...Ch. 16 - Consider heat transfer through a windowless wall...Ch. 16 - Consider heat loss through the two walls of a...Ch. 16 - Consider two houses that are identical, except...Ch. 16 - Consider two walls of a house that are identical...Ch. 16 - Define emissivity and absorptivity. What is...Ch. 16 - What is a blackbody? How do real bodies differ...Ch. 16 - A wood slab with a thickness of 0.05 m is...Ch. 16 - The inner and outer surfaces of a 4-m × 7-m brick...Ch. 16 - The inner and outer surfaces of a 0.5-cm thick 2-m...Ch. 16 - An aluminum pan whose thermal conductivity is 237...Ch. 16 - The north wall of an electrically heated home is...Ch. 16 - In a certain experiment, cylindrical samples of...Ch. 16 - One way of measuring the thermal conductivity of a...Ch. 16 - A concrete wall with a surface area of 20 m2 and a...Ch. 16 - A hollow spherical iron container with outer...Ch. 16 - The inner and outer glasses of a 4-ft × 4-ft...Ch. 16 - An engineer who is working on the heat transfer...Ch. 16 - Air at 20°C with a convection heat transfer...Ch. 16 - Four power transistors, each dissipating 12 W, are...Ch. 16 - In a power plant, pipes transporting superheated...Ch. 16 - An electric current of 5 A passing through a...Ch. 16 - Hot air at 80°C is blown over a 2-m × 4-m flat...Ch. 16 - A 5-cm-external-diameter, 10-m-long hot-water pipe...Ch. 16 - A transistor with a height of 0.4 cm and a...Ch. 16 - A 300-ft-long section of a steam pipe whose outer...Ch. 16 - The boiling temperature of nitrogen at atmospheric...Ch. 16 - Repeat Prob. 16–43 for liquid oxygen, which has a...Ch. 16 - A series of experiments were conducted by passing...Ch. 16 - A 2.1-m-long, 0.2-cm-diameter electrical wire...Ch. 16 - Using the conversion factors between W and Btu/h,...Ch. 16 - The outer surface of a spacecraft in space has an...Ch. 16 - Consider a person whose exposed surface area is...Ch. 16 - Consider a sealed 20-cm-high electronic box whose...Ch. 16 - Two surfaces, one highly polished and the other...Ch. 16 - A spherical interplanetary probe, with a diameter...Ch. 16 - An electronic package in the shape of a sphere...Ch. 16 - Can all three modes of heat transfer occur...Ch. 16 - Can a medium involve (a) conduction and...Ch. 16 - The deep human body temperature of a healthy...Ch. 16 - We often turn the fan on in summer to help us...Ch. 16 - Consider a 20 cm thick granite wall with a thermal...Ch. 16 - A solid plate, with a thickness of 15 cm and a...Ch. 16 - Air at 20°C with a convection heat transfer...Ch. 16 - An electronic package with a surface area of 1 m2...Ch. 16 - Consider steady heat transfer between two large...Ch. 16 - Consider a person standing in a room at 18°C....Ch. 16 - The inner and outer surfaces of a 25-cm-thick wall...Ch. 16 - A 2-in-diameter spherical ball whose surface is...Ch. 16 - An 800-W iron is left on the iron board with its...Ch. 16 - A 3-m-internal-diameter spherical tank made of...Ch. 16 - Solar radiation is incident on a 5 m2 solar...Ch. 16 - A flat-plate solar collector is used to heat water...Ch. 16 - The roof of a house consists of a 22-cm-thick...Ch. 16 - Consider a flat-plate solar collector placed...Ch. 16 - An AISI 304 stainless steel sheet is going through...Ch. 16 - Engine valves (cp = 440 J/kg·K and = 7840 kg/m3)...Ch. 16 - A cylindrical resistor element on a circuit board...Ch. 16 - The heat generated in the circuitry on the surface...Ch. 16 - A 0.3-cm-thick, 12-cm-high, and 18-cm-long circuit...Ch. 16 - A 40-cm-long, 800-W electric resistance heating...Ch. 16 - It is well known that wind makes the cold air feel...Ch. 16 - An engine block with a surface area measured to be...Ch. 16 - Consider an electrical wire submerged in liquid...Ch. 16 - A cylindrical fuel rod of 2 cm in diameter is...Ch. 16 - Consider a person standing in a room maintained at...Ch. 16 - Consider a 3-m × 3-m × 3-m cubical furnace whose...Ch. 16 - A soldering iron has a cylindrical tip of 2.5 mm...Ch. 16 - A thin metal plate is insulated on the back and...Ch. 16 - Consider a flat-plate solar collector placed on...Ch. 16 - An electric heater with the total surface area of...
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- A viscoelastic column is made of a material with a creep compliance of D(t)= 0.75+0.5log10t+0.18(log10t)^2 GPA^-1 for t in s. If a constant compressive stress of σ0 = –100 MPa is applied at t = 0, how long will it take (= t1/2) for the height of the column to decrease to ½ its original value? Note: You will obtain multiple answers for this problem! One makes sense physically and one does not.arrow_forwardA group of 23 power transistors, dissipating 2 W each, are to be cooled by attaching them to a black-anodized square aluminum plate and mounting the plate on the wall of a room at 30°C. The emissivity of the transistor and the plate surfaces is 0.9. Assuming the heat transfer from the back side of the plate to be negligible and the temperature of the surrounding surfaces to be the same as the air temperature of the room, determine the length of the square plate if the average surface temperature of the plate is not to exceed 50°C. Start the iteration process with an initial guess of the size of the plate as 43 cm. The properties of air at 1 atm and the film temperature of (Ts + T)/2 = (50 + 30)/2 = 40°C are k = 0.02662 W/m·°C, ν = 1.702 × 10–5 m2 /s, Pr = 0.7255, and β = 0.003195 K–1. Multiple Choice 0.473 m 0.284 m 0.513 m 0.671 marrow_forwardA 40-cm-diameter, 127-cm-high cylindrical hot water tank is located in the bathroom of a house maintained at 20°C. The surface temperature of the tank is measured to be 44°C and its emissivity is 0.4. Taking the surrounding surface temperature to be also 20°C, determine the rate of heat loss from all surfaces of the tank by natural convection and radiation. The properties of air at 32°C are k=0.02603 W/m-K, v=1.627 x 10-5 m²/s, Pr = 0.7276, and ẞ = 0.003279 K-1 The rate of heat loss from all surfaces of the tank by natural convection is The rate of heat loss from all surfaces of the tank by radiation is W. W.arrow_forward
- A 2.5-m-long thin vertical plate is subjected to uniform heat flux on one side, while the other side is exposed to cool air at 5°C. The plate surface has an emissivity of 0.73, and its midpoint temperature is 55°C. Determine the heat flux subjected on the plate surface. Uniform heat flux -Plate, € = 0.73 Cool air 5°C 7 TSUIT Given: The properties of water at Tf,c= 30°C. k=0.02588 W/m.K, v=1.608 x 10-5 m²/s Pr = 0.7282 The heat flux subjected on the plate surface is W/m²arrow_forwardHot water is flowing at an average velocity of 5.82 ft/s through a cast iron pipe (k=30 Btu/h-ft-°F) whose inner and outer diameters are 1.0 in and 1.2 in, respectively. The pipe passes through a 50-ft-long section of a basement whose temperature is 60°F. The emissivity of the outer surface of the pipe is 0.5, and the walls of the basement are also at about 60°F. If the inlet temperature of the water is 150°F and the heat transfer coefficient on the inner surface of the pipe is 30 Btu/h-ft².°F, determine the temperature drop of water as it passes through the basement. Evaluate air properties at a film temperature of 105°C and 1 atm pressure. The properties of air at 1 atm and the film temperature of (Ts+ T∞)/2 = (150+60)/2 = 105°F are k=0.01541 Btu/h-ft-°F. v=0.1838 × 10-3 ft2/s, Pr = 0.7253, and ẞ = 0.00177R-1arrow_forwardhand-written solutions only, please. correct answers upvoted!arrow_forward
- hand-written solutions only, please. correct answers upvoted!arrow_forward! Required information Consider a flat-plate solar collector placed horizontally on the flat roof of a house. The collector is 1.3 m wide and 2.8 m long, and the average temperature of the exposed surface of the collector is 42°C. The properties of air at 1 atm and the film temperature are k=0.02551 W/m-°C, v = 1.562 × 10-5 m²/s, Pr = 0.7286, and ẞ= 0.003356 K-1 Determine the rate of heat loss from the collector by natural convection during a calm day when the ambient air temperature is 8°C. The rate of heat loss from the collector by natural convection is W.arrow_forwardhand-written solutions only, please. correct answers upvoted!arrow_forward
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