MECH 3040
Quiz Number 4
Name:_
Oct. 31, 2007
Liquid water at 17C, 0.05 kg/s enters a thin walled, 1.0 cm diameter pipe of circular cross
section. There is 57C air flowing over the outside of the pipe. The convective heat transfer
coefficient on the inside
PROBLEM 11.63
KNOYN: Concentric tube heat exchanger with prescribed conditions.
FIND: (a) Maximrnn possible heat transfer. (1:) Effectiveness. (c) Whether heat exchanger should be
run in PP or CF to size or weight; determine ratio of required areas for th
PROBLEEI 4.22
KVOETN: Long constantan u-ire butt-welded to a large copper block forming a thermocouple junction
on the surface of the block.
FIND: (a) The measurement error (TJ - To) for the thermocouple for prescribed conditions, and {b}
Compute and plot
PROBLESI 4.55.
KVO'WN: Flue of square cross section with prescribed geometry, thermal conductivity and inner and
outer surface convective cond1t1ons.
FIND: (a) Heat loss per unit length, [1 , by convection to the air, Effect of grid spacing and
convection
PROBLEM 11.2
IGOWN: Type-302 stainless tube with prescribed inner and outer diameters used in a cross-ow heat
exchanger. Prescribed fouling factors and internal water o'ar conditions.
FIND: (3) Overall coefcient based upon the outer stuface, L}, with air
PROBLEM 5.55
KNOWN: Initial temperature, density, specific heat and diameter of cylindrical rod. Convection
coefficient and temperature of air ow. Time for centerline to reach a prescribed temperamre.
Dependence of convection coefficient on flow velocity.
PROBLEM 3.] l2
KNOWN: Rod (1). k. 2[.} inserted into a perfectly inxulating u'all. expoaing onehallotitx length to
an airstream IT. ht. _\n electromagnetic eld induees a uniform volumetric energy generation in
the itnbedded portion.
FIND: ta} Derive an ex
PROBLEM 2.26
KKOWN: Steady-state conduction with uniform internal energy generation in a plane wall:
temperature distribution has quadratic form. Surface at x20 is prescribed and boundary at x I L is
insulated.
FIND: (a) Calculate the intemal energy gene
PROBLEM 3J5
HNHWN: Dimma'iuna and Itlaliul'iulh iinUEIME'd MIN :1 un.~mpn:-:l¢ Wu]! [2 5m - h in]; E" Hindu uh
I 5111 lugilj.
FIND: Wail rm-11m! maintnucc.
SC" EMA'I'IC:
Hardwood siding (A)
Insufaan N +omgm = L
Grass may; Hardwood (3}
pa I fac
PROBLEM 3.?
EIGHTH: A layer of fatty tissue with fixed inside temperature can experience different
outside convection conditions.
FIND: (a) Ratio of heat loss for different convection conditions. (h) Outer surface
temperature for different convection cond
PROBLEM 13.91
KKOVN: Opaque. diffuse-gray plate with 31 = 0.8 is at T1 = 400 K at a particular instant. The
bottom surface of the plate is subjected to radiative exchange with a furnace. The top surface is
subjected to ambient air and large surroundings.
FRUBLEEI 11.51
ICE0113i: Sliell-and-tub: I-Dierwitlt one shell and DEE tube pass.
PM: (a) 0L1 erutlet temperature for prescribed conditions, EEeet of Fouln'ig and water flout-"rate an
oil outlet tempers-hire.
ELI-[E1 LiTIC:
MT 2100 eeppertu Des.
L
PRDBLEM 11.62
KNDWF: Inlet and nude: temperatures and flow rates for a shell-and-tube hes: exchanger 1with
a single shell and 100' tubes making two passes. Tube inner and outer diameters and1engtla. Heat
Irmtsfer coefcient for ethylenefeol n'a1e1 mixture
Name: _
August 22, 2007
MECH 3040 - Pre-Requisite Exam
Fall 2007
PUT YOUR NAME ON EVERY PAGE! The pages may be separated for grading.
There are four problems. Each problem (page) counts equally.
Closed book, closed notes. Notice the two reference pages at
Or, heat transfer from chip to base of fins equals heat transfer from base of fins to air:
qc =
TC Tb
= q fins + q unfinned surface = ( Nf hA fin surface + hA unfinned ) ( Tb T )
R t,c + R t,b
Solve for Tb.
Tb =
Tc + T ( Nf hA fin surface + hA unfinned )
PROBLEM 4.45
KNOWN: Steady-state temperatures (K) at three nodes of a long rectangular bar.
FIND: (a) Temperatures at remaining nodes and (b) heat transfer per unit length from the bar using
nodal temperatures; compare with result calculated using knowled
PROBLEM 5.5
KNOWN: Diameter and initial temperature of steel balls cooling in air.
FIND: Time required to cool to a prescribed temperature.
SCHEMATIC:
D: 0.0121» Steel, 7E=H50K
. mallow/WK
19:750ch [#15
5,55% T T T czékag-K
h=20W/m2-K - '
ASSUMPTIONS: (1)