PROBLEM 3.158
KNOWN: Dimensions and base temperature of an annular, aluminum fin of rectangular profile.
Ambient air conditions.
FIND: (a) Fin heat loss, (b) Heat loss per unit length of tube with 200
PROBLEM 3.116
KNOWN: Thermal conductivity, diameter and length of a wire which is annealed by passing an
electrical current through the wire.
FIND: (a) Steady-state temperature distribution along wire
PROBLEM 5.116
KNOWN: A 0.12 m thick wall, with thermal diffusivity 1.5 10-6 m2/s, initially at a uniform
temperature of 85C, has one face suddenly lowered to 20C while the other face is perfectly insu
PROBLEM 5.92
KNOWN: Thick oak wall, initially at a uniform temperature of 25C, is suddenly exposed to combustion
products at 800C with a convection coefficient of 20 W/m2K.
FIND: (a) Time of exposure
PURDUE UNIVERSITY
School of Mechanical Engineering
ME 315
HEAT AND MASS TRANSFER
FALL 2014
Lecture:
Division 1: MWF 9:30 am, Rm ME 2061
Professor Amy Marconnet (Rm ME 2151, Tel. 49-5212, email: amarco
PROBLEM 5.1
KNOWN: Electrical heater attached to backside of plate while front surface is exposed to
convection process (T,h); initially plate is at a uniform temperature of the ambient air and
sudden
PROBLEM 5.133
KNOWN: Tantalum rod initially at a uniform temperature, 300K, is suddenly subjected to a
current flow of 80A; surroundings (vacuum enclosure) and electrodes maintained at 300K.
FIND: (a)
PROBLEM 5.142
KNOWN: Conditions associated with heat generation in a rectangular fuel element with surface
cooling. See Example 5.11.
FIND: (a) The temperature distribution 1.5 s after the change in t
PROBLEM 5.143
KNOWN: Thick slab of copper as treated in Example 5.12, initially at a uniform temperature, is
suddenly exposed to large surroundings at 1000C (instead of a net radiant flux).
FIND: (a)
PROBLEM 5.140
KNOWN: Flue of square cross-section, initially at a uniform temperature is suddenly exposed to hot
flue gases. See Problem 4.92.
FIND: Temperature distribution in the wall 5, 10, 50 and
PPROBLEM 5.144
KNOWN: Electric heater sandwiched between two thick plates whose surfaces experience
convection. Case 2 corresponds to steady-state operation with a loss of coolant on the x = -L surfac
PROBLEM 5.146
KNOWN: A process mixture at 200C flows at a rate of 207 kg/min onto a 1-m wide conveyor belt
traveling with a velocity of 36 m/min. The underside of the belt is cooled by a water spray.
PROBLEM 5.148
KNOWN: Cubic-shaped furnace, with prescribed operating temperature and convection heat transfer
on the exterior surfaces.
FIND: Time required for the furnace to cool to a safe working te
PROBLEM 5.147
KNOWN: Stainless steel cylinder, 80-mm diameter by 60-mm length, initially at 600 K, suddenly
2
quenched in an oil bath at 300 K with h = 500 W/m K. Use the ready-to-solve model in the E
PROBLEM 5.145
KNOWN: Reaction and composite clutch plates, initially at a uniform temperature, T i = 40C, are
subjected to the frictional-heat flux shown in the engagement energy curve, q vs. t .
f
FI
PROBLEM 5S.3
KNOWN: Inlet and outlet temperatures of steel rods heat treated by passage through an oven.
FIND: Rod speed, V.
SCHEMATIC:
ASSUMPTIONS: (1) One-dimensional radial conduction (axial conduc
PROBLEM 5.141
KNOWN: Electrical heating elements embedded in a ceramic plate as described in Problem
4.86; initially plate is at a uniform temperature and suddenly heaters are energized.
FIND: Time re
PROBLEM 5.139
KNOWN: Initial temperature distribution in two bars that are to be soldered together; interface
contact resistance.
FIND: (a) Explicit FDE for T4,2 in terms of Fo and Bi x/k R ; stabilit
PROBLEM 5.132
KNOWN: Insulated rod of prescribed length and diameter, with one end in a fixture at 200C, reaches a
uniform temperature. Suddenly the insulating sleeve is removed and the rod is subject
PROBLEM 5.127
KNOWN: One-dimensional convective heating and cooling of a plane slab with Bi1 = 10 (for Heating
Phase 1, beginning at Fo = 0 and ending at Fo = Fo1 = 0.1), Bi2 = 1 (for Cooling Phase 2,
PROBLEM 5.129
KNOWN: Plane wall of thickness 2L, initially at a uniform temperature, is suddenly subjected to
convection heat transfer.
FIND: The mid-plane, T(0,t), and surface, T(L,t), temperatures a
PROBLEM 5.131
2
KNOWN: Plastic film on metal strip initially at 25C is heated by a laser (85,000 W/m for
ton = 10 s), to cure adhesive; convection conditions for ambient air at 25C with coefficient
2
PROBLEM 5.134
KNOWN: Support rod spanning a channel whose walls are maintained at Tb = 300 K. Suddenly the rod
is exposed to cross flow of hot gases with T = 600 K and h = 75 W/m2K. After the rod reac
PROBLEM 5.135
KNOWN: Thin metallic foil of thickness, w, whose edges are thermally coupled to a sink at temperature,
Tsink, initially at a uniform temperature Ti = Tsink, is suddenly exposed on the to
PROBLEM 5.136
KNOWN: Stack or book of steel plates (sp) and circuit boards (b) subjected to a prescribed
platen heating schedule Tp(t). See Problem 5.46 for other details of the book.
FIND: (a) Using
PROBLEM 5.130
KNOWN: Dimensions and properties of a steel-reinforced concrete pillar. Initial, ambient and
surroundings temperatures. Values of convection heat transfer coefficient and contact resista
PROBLEM 5.138
KNOWN: An electrical cable experiencing uniform volumetric generation; the lower half is well
insulated while the upper half experiences convection.
FIND: (a) Explicit, finite-difference
PROBLEM 5.137
KNOWN: Thin, circular-disc subjected to induction heating causing a uniform heat
generation in a prescribed region; upper surface exposed to convection process.
FIND: (a) Transient finit
PROBLEM 5S.1
KNOWN: Configuration, initial temperature and charging conditions of a thermal energy storage
unit.
FIND: Time required to achieve 75% of maximum possible energy storage and corresponding
PROBLEM 3.161
KNOWN: Dimensions and materials of a finned (annular) cylinder wall. Combustion gas and ambient
air conditions. Contact resistance.
FIND: (a) Heat rate per unit length and surface and in
ME315 PROJECT
CRITICAL THICKNESS OF
INSULATION
1
OBJECTIVE & IMPORTANCE
The purpose of this project is to determine the critical
insulation thickness by using the conduction and
convection resistance,
Project Work Plan
Objective: The purpose of this experiment is to determine the critical insulation thickness by measuring
the conduction inside an insulation layer at different thicknesses.
Analysis
1 Consider unsteady heat conduction m a two-dimensional domain given below The domain is
meshed wnh a square mesh VII'h Ax = Ay = 1 01 At iinie 1 = 0,1he boundary conditions given
below are applied su