Water flowing through a large number of long, circular, thin-walled tubes is heated by means of ho parallel plates above and below the tube array. The space between the plates is evacuated, and the plate and tube surfaces may be approximated as blackbodies. (a) Neglecting axial variations, determine the tube surface temperature, T s , if water flows through each tube at a mass rate of m ˙ = 0.20 kg/s and a mean temperature of T m = 300 K . (b) Compute and plot the surface temperature as a function of flow rate for 0.05 ≤ m ˙ ≤ 0.25 kg/s .
Water flowing through a large number of long, circular, thin-walled tubes is heated by means of ho parallel plates above and below the tube array. The space between the plates is evacuated, and the plate and tube surfaces may be approximated as blackbodies. (a) Neglecting axial variations, determine the tube surface temperature, T s , if water flows through each tube at a mass rate of m ˙ = 0.20 kg/s and a mean temperature of T m = 300 K . (b) Compute and plot the surface temperature as a function of flow rate for 0.05 ≤ m ˙ ≤ 0.25 kg/s .
Solution Summary: The author calculates the tube surface temperature if the water flows through each tube. The view factor by reciprocity theorem is calculated.
Water flowing through a large number of long, circular, thin-walled tubes is heated by means of ho parallel plates above and below the tube array. The space between the plates is evacuated, and the plate and tube surfaces may be approximated as blackbodies.
(a) Neglecting axial variations, determine the tube surface temperature, Ts, if water flows through each tube at a mass rate of
m
˙
=
0.20
kg/s
and a mean temperature of
T
m
=
300
K
. (b) Compute and plot the surface temperature as a function of flow rate for
0.05
≤
m
˙
≤
0.25
kg/s
.
Liquid nitrogen is stored in a spherical tank of 1-m diameter, where tank surface is maintained uniformly at 80 K. The spherical tank is enclosed by a 1.6-m diameter concentric sphere with uniform surface temperature of 273 K. Both spherical surfaces have an emissivity of 0.01, and the gap between the inner sphere and outer sphere is vacuumed. Determine the rate of vaporization for the liquid nitrogen.
This experiment is conducted to determine the emissivity of a certain material. A lone cylindrical
rod of diameter D1 = 0.01 m is coated with this new material and is placed in an
evacuated lone cylindrical enclosure of diameter D2 = 0.1 m
and emissivity E2 = 0.95, which is cooled externally and
maintained at a temperature of 200 K at all times. The rod is heated by passing electric current
through it. When steady Operating conditions are reached, it Is observed that the rod
Is dissipating electric power at a rate of 8 W per unit or its leneth and its surface temperature is 500 k, Based on
these measurements, determine the emissivity of the coatine on the rod
EX3
Two coaxial cylinders of diameters Di = 0.10 m and D: = 0.30 m and emissivities 1 =0.7 and 2 = 0.4
are maintained at uniforn temperatures of T1 = 750 K and T2 = 500 K. respectively. Now a coaxial
radiation shield of diameter D; = 0.20 m and emissivity 3 = 0.2 is placed between the two cylinders.
Determine the net rate of radiation heat transfer berween the two cylinders per unit length of the
cylinders and compare the result with that without the shield.
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