PROBLEM 13.137
KNOWN: Configuration of grain dryer. Emissivities of grain bed and heater surface. Temperature
of grain.
FIND: (a)Temperature of heater required for specified drying rate, (b) Convection mass transfer
coefficient required to sustain evapora

PROBLEM 13.131
KNOWN: Pressure, temperature and composition of flue gas in a long duct of prescribed diameter.
FIND: Net radiative flux to the duct surface.
SCHEMATIC:
ASSUMPTIONS: (1) Steady-state conditions, (2) Duct surface behaves as a blackbody, (3)

PROBLEM 13.132
KNOWN: Gas mixture of prescribed temperature, pressure and composition between large parallel
plates of prescribed separation.
FIND: Net radiation flux to the plates.
SCHEMATIC:
ASSUMPTIONS: (1) Steady-state conditions, (2) Furnace wall beh

PROBLEM 13.129
KNOWN: Conditions associated with a spherical furnace cavity.
FIND: Cooling rate needed to maintain furnace wall at a prescribed temperature.
SCHEMATIC:
ASSUMPTIONS: (1) Steady-state, (2) Blackbody behavior for furnace wall, (3) N2 is non-r

PROBLEM 13.130
KNOWN: Diameter and gas pressure, temperature and composition associated with a gas turbine
combustion chamber.
FIND: Net radiative heat flux between the gas and the chamber surface.
SCHEMATIC:
ASSUMPTIONS: (1) Steady-state conditions, (2)

PROBLEM 13.118
KNOWN: Disk heated by an electric furnace on its lower surface and exposed to an environment on
its upper surface.
FIND: (a) Net heat transfer to (or from) the disk qnet,d when Td = 400 K and (b) Compute and plot
qnet,d as a function of dis

PROBLEM 13.127
KNOWN: Temperature and emissivity of ceramic plate which is separated from a glass plate of
equivalent height and width by an air space. Temperature of air and surroundings on opposite side of
glass. Spectral radiative properties of glass.

PROBLEM 13.128
KNOWN: Spectral distribution of the absorption coefficient of pure solid silicon.
FIND: (a) The total absorption coefficient for pure solid silicon subject to irradiation from a source at
the melting point temperature of silicon. (b) Estima

PROBLEM 13.125
KNOWN: Temperature, power dissipation and emissivity of a cylindrical heat source. Surface
emissivities of a parabolic reflector. Temperature of air and surroundings.
FIND: (a) Radiation circuit, (b) Net radiation transfer from the heater,

PROBLEM 13.124
KNOWN: Diameter and emissivity of rod heater. Diameter and position of reflector. Width,
emissivity, temperature and position of coated panel. Temperature of air and large surroundings.
FIND: (a) Equivalent thermal circuit, (b) System of eq

PROBLEM 13.123
KNOWN: Dimensions, emissivity and upper temperature limit of coated panel. Arrangement and
power dissipation of a radiant heater. Temperature of surroundings.
FIND: (a) Minimum panel-heater separation, neglecting convection, (b) Minimum pan

PROBLEM 13.122
KNOWN: Diameters, temperatures, and emissivities of concentric spheres.
FIND: Rate at which nitrogen is vented from the inner sphere. Effect of radiative properties on
evaporation rate.
SCHEMATIC:
ASSUMPTIONS: Diffuse-gray surfaces.
5
PROPE

PROBLEM 13.120
KNOWN: Diameter and surface temperature of a fire tube. Gas low rate and temperature.
Emissivity of tube and partition.
FIND: (a) Heat transfer per unit tube length, q, without the partition, (b) Partition temperature, Tp,
and heat rate wit

PROBLEM 13.121
KNOWN: Dimensions of horizontal air space separating plates of known temperature.
Emissivity of end plates and interleaving aluminum sheets.
FIND: (a) Neglecting conduction or convection in the air , determine the heat flux through the
syst

PROBLEM 13.119
KNOWN: Radiation shield facing hot wall at Tw = 400 K is backed by an insulating material of
known thermal conductivity and thickness which is exposed to ambient air and surroundings at 300 K.
FIND: (a) Heat loss per unit area from the hot

PROBLEM 13.117
KNOWN: Dimensions and inclination angle of a flat-plate solar collector. Absorber and cover plate
temperatures and emissivities.
FIND: (a) Rate of heat transfer by free convection and radiation, (b) Effect of the absorber plate
temperature

PROBLEM 13.116
KNOWN: Diameters of heated tube and radiation shield. Tube surface temperature and temperature
of ambient air and surroundings.
FIND: Temperature of radiation shield and heat loss per unit length of tube.
SCHEMATIC:
ASSUMPTIONS: (1) Opaque,

PROBLEM 13.115
KNOWN: Diameters and temperatures of a heated tube and a radiation shield.
FIND: (a) Total heat loss per unit length of tube, (b) Effect of shield diameter on heat rate.
SCHEMATIC:
ASSUMPTIONS: (1) Opaque, diffuse-gray surfaces, (2) Negligi

PROBLEM 13.114
KNOWN: Absorber and cover plate temperatures and spectral absorptivities for a flat plate solar
collector. Collector orientation and solar flux.
FIND: (a) Rate of solar radiation absorption per unit area, (b) Heat loss per unit area.
SCHEMA

PROBLEM 13.113
KNOWN: Dimensions and emissivity of double pane window. Thickness of air gap. Temperatures
of room and ambient air and the related surroundings.
FIND: (a) Temperatures of glass panes and rate of heat transfer through window, (b) Heat rate i

PROBLEM 13.109
KNOWN: Ceiling temperature of furnace. Thickness, thermal conductivity, and/or emissivities of
alternative thermal insulation systems. Convection coefficient at outer surface and temperature of
surroundings.
FIND: (a) Mathematical model for

PROBLEM 13.112
KNOWN: Temperatures and emissivity of window panes and critical Rayleigh number for onset of
convection in air space.
FIND: (a) The conduction heat flux across the air gap for the optimal spacing, (b) The total heat flux
for uncoated panes,

PROBLEM 13.110
KNOWN: Dimensions of a composite insulation consisting of honeycomb core sandwiched between
solid slabs.
FIND: Total thermal resistance.
SCHEMATIC: Because of the repetitive nature of the honeycomb core, the cell sidewalls will be
adiabatic

PROBLEM 13.111
KNOWN: Dimensions and surface conditions of a cylindrical thermos bottle filled with hot coffee
and lying horizontally.
FIND: Heat loss.
SCHEMATIC:
ASSUMPTIONS: (1) Steady-state conditions, (2) Negligible heat loss from ends (long infinite

PROBLEM 13.108
KNOWN: Two large parallel plates, temperature of each plate. Bare plate and paint
emissivities, thickness of paint layers.
FIND: (a) Radiation heat flux across the gap for 1 = 2 = s = 0.85, (b) Radiation heat flux
across the gap for 1 = 2 =

PROBLEM 13.104
KNOWN: Long uniform rod with volumetric energy generation positioned coaxially within a larger circular tube
maintained at 500C.
FIND: (a) Center T1(0) and surface T1s temperatures of the rod for evacuated space, (b) T1(0) and T1s for
airsp

PROBLEM 13.102
KNOWN: Electrical conductors in the form of parallel plates having one edge mounted to a ceramic
insulated base. Plates exposed to large, isothermal surroundings, Tsur. Operating temperature is T1 =
500 K.
FIND: (a) Electrical power dissipa

PROBLEM 13.105
KNOWN: Side wall and gas temperatures for adjoining semi-cylindrical ducts. Gas flow convection
coefficients.
FIND: (a) Temperature of intervening wall, (b) Verification of gas temperature on one side.
SCHEMATIC:
ASSUMPTIONS: (1) All duct s

PROBLEM 13.103
KNOWN: Surface temperature and spectral radiative properties. Temperature of ambient air. Solar
irradiation or temperature of shield.
FIND: (a) Convection heat transfer coefficient when surface is exposed to solar radiation, (b)
Temperature

PROBLEM 13.97
KNOWN: Ice rink with prescribed ice, rink air, wall, ceiling and outdoor air conditions.
FIND: (a) Temperature of the ceiling, Tc, having an emissivity of 0.05 (highly reflective panels) or
0.94 (painted panels); determine whether condensati