Fundamentals of Heat and Mass Transfer
7th Edition
ISBN: 9780470501979
Author: Frank P. Incropera, David P. DeWitt, Theodore L. Bergman, Adrienne S. Lavine
Publisher: Wiley, John & Sons, Incorporated
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Chapter 7, Problem 7.83P
To determine
Maximum allowable thickness of the helium layer.
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Air at 25°C flows at 50 × 10-6 kg/s within 100-mm-long channels used to cool a high thermal conductivity metal mold. Assume the
flow is hydrodynamically and thermally fully developed.
Air, Tmi = 25°C
Mold, T=50°C-
Case A
Case B
(a) Determine the rate of heat transferred, in W, to the air for a circular channel (D =
(case A).
10 mm) when the mold temperature is 50°C
(b) Consider air flowing under the same conditions as in case A, except now the channel is segmented into six smaller triangular
sections. The flow area of case A is equal to the total flow area of case B. Determine the rate of heat transferred, in W, to the air for the
segmented channel.
(c) Determine the pressure drops for cases A and B, both in Pa.
Merrill et al. (1965) in a series of classic experiments studied the flow of blood in capillary tubes of various diameters. The blood had a hematocrit of 39.3 and the temperature was 20°C. They measured the pressure drop as a function of the flow rate for five tube diameters ranging from 288 to 850 μm. When they expressed the measured pressure drops in terms of the wall shear stress, and the volumetric flow rates in terms of the reduced average velocity, all of the data for the various tube sizes formed, within the experimental accuracy, a single line as predicted by the Rabinowitsch equation expressed in terms of reduced average velocity. From their results they provide the following values of the Casson parameters at 20°C: τy = 0.0289 dynes cm−2 and s = 0.229 (dynes s cm−2)1/2. Using these values for τy and s, show that the equation below for reduced average velocity provides an excellent fit to their data summarized in the following table.
(Wall shear stress) τw , dynes cm-2…
A chromatographer fed up with waiting 36
minutes to accomplish a separation requiring
8000 plates, packs a new column to reduce
separation time. She slashed the particle
diameter by a factor of 3. She adjusted the
flow rate to work at the same reduced
velocity as before ( the h versus v curves for
the two columns are the same) and chooses a
column length to get the same number of
plates.
Comparing the new column to the old, by
what factor will the following parameters
change:
a) plate height
b) column length
c) flow velocity
d) pressure drop
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What is the new separation time?
Chapter 7 Solutions
Fundamentals of Heat and Mass Transfer
Ch. 7 - Consider the following fluids at a film...Ch. 7 - Engine oil at 100C and a velocity of 0.1 m/s flows...Ch. 7 - Consider steady, parallel flow of atmospheric air...Ch. 7 - Consider a liquid metal (Pr1), with free stream...Ch. 7 - Consider the velocity boundary layer profile for...Ch. 7 - Consider a steady, turbulent boundary layer on and...Ch. 7 - Consider flow over a flat plate for which it is...Ch. 7 - A flat plate of width 1 m is maintained at a...Ch. 7 - An electric air heater consists of a horizontal...Ch. 7 - Consider atmospheric air at 25C and a velocity of...
Ch. 7 - Repeat Problem 7.11 for the case when the boundary...Ch. 7 - Consider water at 27°C in parallel flow over an...Ch. 7 - Explain under what conditions the total rate of...Ch. 7 - In fuel cell stacks, it is desirable to operate...Ch. 7 - The roof of a refrigerated truck compartment is of...Ch. 7 - The top surface of a heated compartment consists...Ch. 7 - Calculate the value of the average heat transfer...Ch. 7 - The proposed design for an anemometer to determine...Ch. 7 - Steel (AISI 1010) plates of thickness =6mm and...Ch. 7 - Consider a rectangular fin that is used to cool a...Ch. 7 - The Weather Channel reports that it is a hot,...Ch. 7 - In the production of sheet metals or plastics, it...Ch. 7 - An array of electronic chips is mounted within a...Ch. 7 - A steel strip emerges from the hot roll section of...Ch. 7 - In Problem 7.23. an anemometer design was...Ch. 7 - One hundred electrical components, each...Ch. 7 - The boundary layer associated with parallel flow...Ch. 7 - Forced air at 250C and 10 m/s is used to cool...Ch. 7 - Air at atmospheric pressure and a temperature of...Ch. 7 - Consider a thin, 50mm50mm fuel cell similar to...Ch. 7 - The cover plate of a flat-plate solar collector is...Ch. 7 - An array of 10 silicon chips, each of length...Ch. 7 - A square (10mm10mm) silicon chip is insulated on...Ch. 7 - A circular pipe of 25-mm outside diameter is...Ch. 7 - An L=1-m- long vertical copper tube of inner...Ch. 7 - A long, cylindrical, electrical heating element of...Ch. 7 - Consider the conditions of Problem 7.49, but now...Ch. 7 - Pin fins are to be specified for use in an...Ch. 7 - Prob. 7.52PCh. 7 - Prob. 7.53PCh. 7 - Hot water at 500C is routed from one building in...Ch. 7 - In a manufacturing process, long aluminum rods of...Ch. 7 - Prob. 7.58PCh. 7 - To determine air velocity changes, it is proposed...Ch. 7 - Determine the convection heat loss from both the...Ch. 7 - Prob. 7.63PCh. 7 - Prob. 7.64PCh. 7 - Prob. 7.67PCh. 7 - A thermocouple is inserted into a hot air duct to...Ch. 7 - Consider a sphere with a diameter of 20 mm and a...Ch. 7 - Prob. 7.76PCh. 7 - A spherical, underwater instrument pod used to...Ch. 7 - Worldwide. over a billion solder balls must be...Ch. 7 - Prob. 7.80PCh. 7 - Prob. 7.81PCh. 7 - Consider the plasma spray coating process of...Ch. 7 - Prob. 7.83PCh. 7 - Tissue engineering involves the development of...Ch. 7 - Consider temperature measurement in a gas stream...Ch. 7 - Prob. 7.89PCh. 7 - A preheater involves the use of condensing steam...Ch. 7 - Prob. 7.91PCh. 7 - A tube bank uses an aligned arrangement of...Ch. 7 - A tube bank uses an aligned arrangement of...Ch. 7 - Repeat Problem 7.94, but with NL=7,NT=10, and...Ch. 7 - Heating and cooling with miniature impinging jets...Ch. 7 - A circular transistor of 10-mm diameter is cooled...Ch. 7 - A long rectangular plate of AISI 304 stainless...Ch. 7 - A cryogenic probe is used to treat cancerous skin...Ch. 7 - Prob. 7.103PCh. 7 - Prob. 7.104PCh. 7 - Prob. 7.105PCh. 7 - Consider the packed bed of aluminum spheres...Ch. 7 - Prob. 7.108PCh. 7 - Prob. 7.109PCh. 7 - Prob. 7.111PCh. 7 - Packed beds of spherical panicles can be sintered...Ch. 7 - Prob. 7.114PCh. 7 - Prob. 7.116PCh. 7 - Prob. 7.117PCh. 7 - Prob. 7.118PCh. 7 - Prob. 7.119PCh. 7 - Prob. 7.120PCh. 7 - Dry air at 35°C and a velocity of 20 m/s flows...Ch. 7 - Prob. 7.123PCh. 7 - Benzene, a known carcinogen, has been spilled on...Ch. 7 - Prob. 7.125PCh. 7 - Prob. 7.126PCh. 7 - Condenser cooling water for a power plant is...Ch. 7 - Prob. 7.128PCh. 7 - In a paper-drying process, the paper moves on a...Ch. 7 - Prob. 7.131PCh. 7 - Prob. 7.132PCh. 7 - Prob. 7.133PCh. 7 - Prob. 7.134PCh. 7 - Prob. 7.136PCh. 7 - It has been suggested that heat transfer from a...Ch. 7 - Prob. 7.138PCh. 7 - Cylindrical dry-bulb and wet-bulb thermometers are...Ch. 7 - The thermal pollution problem is associated with...Ch. 7 - Cranberries are harvested by flooding the bogs in...Ch. 7 - A spherical drop of water, 0.5 mm in diameter, is...Ch. 7 - Prob. 7.143PCh. 7 - Prob. 7.144PCh. 7 - Prob. 7.145PCh. 7 - Prob. 7.146PCh. 7 - Prob. 7.147PCh. 7 - Consider an air-conditioning system composed of a...Ch. 7 - Prob. 7.149P
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