Consider laminar flow of a fluid with P r = 4 that undergoes a combined entrance process within a constant surface temperature tube of length L < x f d , t , with a flow rate of ii An engineer suggests that the total heat transfer rate can be improved if the tube is divided into N shorter tubes, each of length L N = L / N with a flow rate of m/N . Determine an expression for the ratio of the heat transfer coefficient averaged over the N tubes, each experiencing a combined entrance process, to the heat transfer coefficient averaged over the single tube, h ¯ D , N / h ¯ D , 1 .
Consider laminar flow of a fluid with P r = 4 that undergoes a combined entrance process within a constant surface temperature tube of length L < x f d , t , with a flow rate of ii An engineer suggests that the total heat transfer rate can be improved if the tube is divided into N shorter tubes, each of length L N = L / N with a flow rate of m/N . Determine an expression for the ratio of the heat transfer coefficient averaged over the N tubes, each experiencing a combined entrance process, to the heat transfer coefficient averaged over the single tube, h ¯ D , N / h ¯ D , 1 .
Consider laminar flow of a fluid with
P
r
=
4
that undergoes a combined entrance process within a constant surface temperature tube of length
L
<
x
f
d
,
t
, with a flow rate of ii An engineer suggests that the total heat transfer rate can be improved if the tube is divided into N shorter tubes, each of length
L
N
=
L
/
N
with a flow rate of m/N. Determine an expression for the ratio of the heat transfer coefficient averaged over the N tubes, each experiencing a combined entrance process, to the heat transfer coefficient averaged over the single tube,
h
¯
D
,
N
/
h
¯
D
,
1
.
Heat transfer problem
Water flows through a thin-walled cylindrical tube of diameter 1 cm, maintained at a uniform temperature, ?s = 360 K. The inlet and outlet temperature of water was found to be ?i= 280 K and ?o = 355 K, respectively. (a) What is the log mean temperature difference in this case? (b) If the mass flow rate is 0.005 kg/s, what is the total rate of heat transfer from the tube to the water? (c) What is the Reynolds number corresponding to the given flow conditions? (d) Assuming fully developed flow in the entire tube, what should be the length of the tube to allow the abovementioned operating conditions ?
Hot fluid "C 2562 J/kg.k, Pr 51.3, u-5.22E-3 Pa.s, k0.260 Wm.K" flows af 0.8
kg/min inside a 3-mm diameter, thin walled tube. The tube is coiled and submerged in
a water bath maintained at 23 C. The fluid experiences a temperature drop of 63°C and
leaves the tube at 35 C. What is the required lengih of the tube "m Neglect heat
transfer enhancement associated with the coiling. Assume ftlly developed flow, If turbulent
flow use Dittus Boelter equation: Nn 0.023 Re
Pr
Engine oil flows at a rate of 0.95 kg/s through a tube of 119 mm inside diameter and is heated from 293 to 327 K by condensing steam at 373 K. For the described case answer the following:i. Identify the type of flow and explain briefly about the flow with suitable assumptions & sketches.ii. Determine the inside heat transfer coefficient and rate of heat transfer per meter length of pipe for the identified flow pattern.
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