Fundamentals of Heat and Mass Transfer
Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470917855
Author: Bergman, Theodore L./
Publisher: John Wiley & Sons Inc
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Chapter 8, Problem 8.98P

It is common practice (o recover waste heat from an oil-or gas-fired furnace by using the exhaust gases to preheatthe combustion air. A device commonly used for thispurpose consists of a concentric pipe arrangement forwhich the exhaust gases are passed through the innerpipe, while the cooler combustion air flows through anannular passage around the pipe.

Chapter 8, Problem 8.98P, It is common practice (o recover waste heat from an oil-or gas-fired furnace by using the exhaust

Consider conditions for which there b a uniformheattransferrateperunitlength, q ' 1 = 1.25 × 10 5 W/m , .from the exhaust gases to the pipe inner surface, while air flows through the annular passage at a rateof m a = 2.1 kg/s. The thin-walled inner pipe is ofdiameter D i = 2 m, while the outer pipe, which is well insulated from the surroundings, is of diameter D 0 = 2.05 m. The air properties may be taken to be c p = 1030 J/kg K , μ = 270 × 10 7 N s/m 2 , k = 0.041 W/m K , and Pr= 0.68.

(a) Ifairentersat T a , 1 = 300 K andL=7m, what isthe air outlet temperature T a , 2 ?

(b) If the airflow b fully developed throughout theannular region, what b the temperature of the innerpipe at the Inlet ( T s , i , 1 ) and owlet ( T s , i , 2 ) sections ofthe device? What b the outer surface temperature T s , 0 , 1 at the inlet?

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Chapter 8 Solutions

Fundamentals of Heat and Mass Transfer

Ch. 8 - Consider a circular tube of diameter D and length...Ch. 8 - Consider flow in a circular tube. Within the test...Ch. 8 - Consider a cylindrical nuclear fuel rod of length...Ch. 8 - Consider the laminar thermal boundary layer...Ch. 8 - In a particular application involving fluid flow...Ch. 8 - A flat-plate solar collector is used w heat...Ch. 8 - Atmospheric air enters the heated section of a...Ch. 8 - Fluid enters a tube with a flow rate of 0.015kg/s...Ch. 8 - Water at 300 K and a flow rate of 5kg/s enters a...Ch. 8 - Slug flow is an idealized tube flow condition for...Ch. 8 - Superimposing a control volume that is...Ch. 8 - An experimental nuclear core simulation apparatus...Ch. 8 - Water at 20°C and a flow rate of 0.1kg/s enters a...Ch. 8 - Engine oil is heated by flowing through a circular...Ch. 8 - Engine oil flows through a 25mm -diameter tube at...Ch. 8 - In the final stages of production, a...Ch. 8 - An oil preheater consists of a single tube of 10mm...Ch. 8 - Engine oil flows at a rate of 1kg/s through a 5mm...Ch. 8 - Air at p=1atm enters a thin-walled ( D=5-mm...Ch. 8 - To cool a summer home without using a vapor...Ch. 8 - Batch processes are often used in chemical and...Ch. 8 - The evaporator section of a heat pump is installed...Ch. 8 - Water flowing at 2kg/s through a 40mm diameter...Ch. 8 - Consider the conditions associated with the hot...Ch. 8 - A thick-walled, stainless steel (AISI 316) pipe of...Ch. 8 - An air heater for an industrial application...Ch. 8 - Consider fully developed conditions in a circular...Ch. 8 - Consider the encased pipe of Problem 4.29, but now...Ch. 8 - Water flows through a thick-wailed tube with an...Ch. 8 - Atmospheric air enters a 10m -long. 150mm...Ch. 8 - NaK (45%/55). which is an alloy of sodium and...Ch. 8 - The products of combustion from a burner are...Ch. 8 - Liquid mercury at 0.5kg/s is lo be heated from 300...Ch. 8 - The surface of a 50-mm-diameter. thin-walled tube...Ch. 8 - Consider a horizontal, thin-walled circular tube...Ch. 8 - Consider pressurized liquid water flowing at...Ch. 8 - Cooling water flows through the 25.4-mm -diameter...Ch. 8 - The air passage for cooling a gas turbine vane can...Ch. 8 - The core of a high-temperature, gas-cooled nuclear...Ch. 8 - Air at 200kPa enters a 2-m -long, thin-walled tube...Ch. 8 - Heated air required for a food-drying process is...Ch. 8 - Consider laminar flow of a fluid with Pr=4 that...Ch. 8 - A common procedure for cooling a high-performance...Ch. 8 - One way to cool chips mounted on the circuit...Ch. 8 - Refrigerant- 134a is being transported a 0.1 kg/s...Ch. 8 - Oil at 150°C flows slowly through a long,...Ch. 8 - Exhaust gases from a wire processing oven are...Ch. 8 - A hot fluid passes through a thin-walled tube of...Ch. 8 - Consider a thin-walled tube of 10mm diameter and...Ch. 8 - Water at a flow rate of m =0.215kg/s is cooled...Ch. 8 - To maintain pump power requirements per unit flow...Ch. 8 - Consider a thin-walled, metallic tube of length...Ch. 8 - A circular tube of diameter D=0.2mm and length...Ch. 8 - Repeat Problem 8.66 for a circular tube of...Ch. 8 - Heat is to be removed from a reaction vessel...Ch. 8 - A healing contractor must heat 0.2kg/s of water...Ch. 8 - A thin-walled tube with a diameter of 6 mm and...Ch. 8 - A 50mm -diameter, thin—walled metal pipe covered...Ch. 8 - A thin-walled, uninsulated 0.3m -diameter duct is...Ch. 8 - Pressurized water at Tm,i=200C is pumped at...Ch. 8 - Water at 290K and 0.2kg/s flows through a Teflon...Ch. 8 - The temperature of flue gases flowing through the...Ch. 8 - In a biomedical supplies manufacturing process, a...Ch. 8 - Consider the ground source heat pump of Problem...Ch. 8 - For a sharp-edged inlet and a combined entry...Ch. 8 - Fluid enters a thin-walled rube of 5-mni diameter...Ch. 8 - Air at 3104kg/s and 27C enters a rectangular duct...Ch. 8 - Air at 25C flows at 30106kg/s within 100mm -long...Ch. 8 - A cold plate is an active cooling device that is...Ch. 8 - The cold plate design of Problem 8.82 has not been...Ch. 8 - A device that recovers heat from high-temperature...Ch. 8 - Air at 1 atm and 285K enters a 2-m -long...Ch. 8 - A double-wall heat exchanger is used to transfer...Ch. 8 - Consider laminar, fully developed flow in a...Ch. 8 - You have been asked to perform a feasibility study...Ch. 8 - A coolant flows through a rectangular channel...Ch. 8 - An electronic circuit board dissipating 50W is...Ch. 8 - To slow down large prime movers like locomotives,...Ch. 8 - A printed circuit board (PCB) is cooled by...Ch. 8 - Water at m=0.02kg/s and Tm,i=20C enters an annular...Ch. 8 - tFor the conditions of Problem 8.93, how tong must...Ch. 8 - Referring 10 Figure 8.11, consider conditions in...Ch. 8 - Consider the air healer of Problem 8.38, but now...Ch. 8 - Consider a concentric tube annulus for which the...Ch. 8 - It is common practice (o recover waste heat from...Ch. 8 - A concentric lube arrangement, for which the inner...Ch. 8 - Consider sterilization of the pharmaceutical...Ch. 8 - An engineer proposes to insert a solid rod of...Ch. 8 - An electrical power transformer of diameter 230mm...Ch. 8 - A bayonet cooler is used to reduce the temperature...Ch. 8 - The mold used in an injection molding process...Ch. 8 - Prob. 8.107PCh. 8 - Prob. 8.108PCh. 8 - Consider the microchannel cooling arrangement...Ch. 8 - The onset of turbulence in a gas flowing within a...Ch. 8 - Due to its comparatively large thermal...Ch. 8 - A novel scheme for dissipating heat from the chips...Ch. 8 - An experiment is designed to study microscale...Ch. 8 - Determine the tube diameter that corresponds to a...Ch. 8 - An experiment is devised to measure liquid flow...Ch. 8 - In the processing of very long plastic tubes of...Ch. 8 - Air at 300K and a flow rate of 3kg/h passes upward...Ch. 8 - What is the convection mass transfer coefficient...Ch. 8 - Air flowing through a tube of 75mm diameter passes...Ch. 8 - Consider gas flow of mass density and rate m...Ch. 8 - Atmospheric air at 25C and 3104kg/s flows through...Ch. 8 - Air at 25C and 1atm is in fully developed flow at...Ch. 8 - A humidifier consists of a bundle of vertical...Ch. 8 - The final step of a manufacturing process in which...Ch. 8 - Dry air is inhaled at a rate of lo liter/win...Ch. 8 - A mass transfer Operation is preceded by laminar...

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