PROBLEM 3.43
KNOWN: Steady-state temperature distribution of convex shape for material with k = ko(1 +
T) where is a constant and the mid-point temperature is To higher than expected for a
linear temperature distribution.
FIND: Relationship to evaluate in
PROBLEM 3.29
KNOWN: Temperatures and convection coefficients associated with fluids at inner and outer
surfaces of a composite wall. Contact resistance, dimensions, and thermal conductivities
associated with wall materials.
FIND: (a) Rate of heat transfer
PROBLEM 3.37
KNOWN: Volume fraction of air in stone mix concrete, forming a lightweight aggregate concrete.
FIND: Values of the lightweight aggregates thermal conductivity, density and specific heat.
SCHEMATIC:
Stone mix concrete
Air bubble
ASSUMPTIONS: (
PROBLEM 3.53
KNOWN: Electric current and resistance of wire. Wire diameter and emissivity. Thickness,
emissivity and thermal conductivity of coating. Temperature of ambient air and surroundings.
Expression for heat transfer coefficient at surface of the w
PROBLEM 3.54
KNOWN: Diameter of electrical wire. Thickness and thermal conductivity of rubberized sheath.
Contact resistance between sheath and wire. Convection coefficient and ambient air temperature.
Maximum allowable sheath temperature.
FIND: Maximum a
PROBLEM 3.46
KNOWN: Temperature and volume of hot water heater. Nature of heater insulating material. Ambient
air temperature and convection coefficient. Unit cost of electric power.
FIND: Heater dimensions and insulation thickness for which annual cost o
PROBLEM 3.49
KNOWN: Inner and outer radii of a tube wall which is heated electrically at its outer surface. Inner and
outer wall temperatures. Temperature of fluid adjoining outer wall.
FIND: Effect of wall thermal conductivity, thermal contact resistance
PROBLEM 3.44
KNOWN: Construction and dimensions of a device to measure the temperature of a surface.
Ambient and sensing temperatures, and thermal resistance between the sensing element and the
pivot point.
FIND: (a) Thermal resistance between the surface
PROBLEM 3.47
KNOWN: Dimensions of components of a pipe-in-pipe device. Thermal conductivity of materials,
inner and outer heat transfer coefficients, outer fluid temperature.
FIND: (a) Maximum crude oil temperature to not exceed allowable service temperat
PROBLEM 3.23
KNOWN: Dimensions and temperature of a canister containing a solid oxide fuel cell.
Surroundings and ambient temperature.
FIND: (a) Required insulation thickness to keep the equivalent blackbody temperature below 305
K, (b) Canister surface t
PROBLEM 3.32
KNOWN: Operating conditions, measured temperatures and heat input, and theoretical thermal
conductivity of a carbon nanotube.
FIND: (a) Thermal contact resistance between the carbon nanotube and the heating and sensing
islands, (b) Fraction o
PROBLEM 3.30
KNOWN: Outer and inner surface convection conditions associated with zirconia-coated, Inconel
turbine blade. Thicknesses, thermal conductivities, and interfacial resistance of the blade materials.
Maximum allowable temperature of Inconel.
FIN
PROBLEM 3.26
KNOWN: Materials and dimensions of a composite wall separating a combustion gas from a
liquid coolant.
FIND: (a) Heat loss per unit area, and (b) Temperature distribution.
SCHEMATIC:
ASSUMPTIONS: (1) One-dimensional heat transfer, (2) Steady-
PROBLEM 3.9
KNOWN: Design and operating conditions of a heat flux gage.
FIND: (a) Convection coefficient for water flow (T s = 27C) and error associated with neglecting
conduction in the insulation, (b) Convection coefficient for air flow (T s = 125C) and
PROBLEM 3.27
KNOWN: Operating conditions for a board mounted chip.
FIND: (a) Equivalent thermal circuit, (b) Chip temperature, (c) Maximum allowable heat dissipation for
dielectric liquid (ho = 1000 W/m2K) and air (ho = 100 W/m2K). Effect of changes in ci
PROBLEM 3.20
KNOWN: Window surface area and thickness, inside and outside heat transfer coefficients, outside
and passenger compartment temperatures.
FIND: Heat loss through the windows for high and low inside heat transfer coefficients.
SCHEMATIC:
T,o =
PROBLEM 3.24
KNOWN: Representative dimensions and thermal conductivities for the layers of fire-fighters
protective clothing, a turnout coat.
FIND: (a) Thermal circuit representing the turnout coat; tabulate thermal resistances of the layers
and processes
PROBLEM 3.22
KNOWN: Total floor space and vertical distance between floors for a square, flat roof building.
FIND: (a) Expression for width of building which minimizes heat loss, (b) Width and number of floors
which minimize heat loss for a prescribed flo
PROBLEM 3.13
KNOWN: Composite wall of a house with prescribed convection processes at inner and
outer surfaces.
FIND: (a) Expression for thermal resistance of house wall, R tot ; (b) Total heat loss, q(W); (c)
Effect on heat loss due to increase in outsid
PROBLEM 3.17
KNOWN: Thickness and thermal conductivity of oven wall insulation. Exterior air temperature and
convection heat transfer coefficient. Interior air temperature and convection heat transfer coefficients
under free and forced convection conditio
PROBLEM 3.10
KNOWN: 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, (b) Outer surface
temperature for different convection cond
PROBLEM 3.11
KNOWN: Temperature of the heating island and sensing island, as well as the surrounding silicon
nitride wafer temperature of Example 3.4.
FIND: The thermal conductivity of the carbon nanotube, k cn , for the conditions of the problem
statemen
PROBLEM 3.14
KNOWN: Composite wall of a house with prescribed convection processes at inner and
outer surfaces.
FIND: Daily heat loss for prescribed diurnal variation in ambient air temperature.
SCHEMATIC:
ASSUMPTIONS: (1) One-dimensional, steady-state co
PROBLEM 3.12
KNOWN: Dimensions of a thermopane window. Room and ambient air conditions.
FIND: (a) Heat loss through window, (b) Effect of variation in outside convection coefficient for
double and triple pane construction.
SCHEMATIC (Double Pane):
ASSUMPT
PROBLEM 3.4
KNOWN: Desired inner surface temperature of rear window with prescribed inside and outside air
conditions.
FIND: (a) Heater power per unit area required to maintain the desired temperature, and (b) Compute and
plot the electrical power require
PROBLEM 3.2
KNOWN: Thickness of basement wall. Inner and outer wall temperatures. Thermal conductivity of
aerated concrete.
FIND: Thickness of polystyrene insulation needed to reduce heat flux through the stone mix concrete
wall to that of the aerated con
PROBLEM 3.1
KNOWN: One-dimensional, plane wall separating hot and cold fluids at T ,1 and T ,2 ,
respectively.
FIND: Temperature distribution, T(x), and heat flux, q , in terms of T ,1 , T ,2 , h1 , h 2 , k
x
and L.
SCHEMATIC:
ASSUMPTIONS: (1) One-dimensi