Determine the total condensation rate and heat transfer rate for the process of Problem 10.46 when the
pipe is oriented at angles of = 0, 30, 45 and 60 from the horizontal.
KNOWN: Dimensions and surface temperature of tube exposed to steam.
KNOWN: Plate temperature and spectral absorptivity of coating.
FIND: (a) Solar irradiation, (b) Effect of solar irradiation on plate temperature, total absorptivity, and
ASSUMPTIONS: (1) Steady-state, (2) Opaque
KNOWN: Flat plate exposed to night sky and in ambient air at Tair = 15C with a relative humidity
of 70%. Radiation from the atmosphere or sky estimated as a fraction of the blackbody radiation
corresponding to the near-ground air temperatur
KNOWN: Opaque, spectrally-selective horizontal plate with electrical heater on backside is exposed
to convection, solar irradiation and sky irradiation.
FIND: Electrical power required to maintain plate at 60C.
ASSUMPTIONS: (1) P
KNOWN: Shed roof of weathered galvanized sheet metal exposed to solar insolation on a cool, clear
spring day with ambient air at - 10C and convection coefficient estimated by the empirical correlation
h = 10 T1/3 (W/m K with temperature u
KNOWN: Spectrally selective and gray surfaces in earth orbit are exposed to solar irradiation, GS, in
a direction 30 from the normal to the surfaces.
FIND: Equilibrium temperature of each plate.
Gs = 1368 W/m2
ASSUMPTIONS: (1) Pl
KNOWN: Spectral distribution of coating on satellite surface. Irradiation from earth and sun.
FIND: (a) Steady-state temperature of satellite on dark side of earth, (b) Steady-state temperature on
GS = 1368 W/m2
KNOWN: Radiative properties and operating conditions of a space radiator.
FIND: Equilibrium temperature of the radiator.
ASSUMPTIONS: (1) Steady-state conditions, (2) Negligible irradiation due to earth emission.
KNOWN: Inner and outer radii, spectral reflectivity, and thickness of an annular fin. Base temperature
and solar irradiation.
FIND: (a) Rate of heat dissipation if f = 1, (b) Differential equation governing radial temperature
KNOWN: Spherical satellite exposed to solar irradiation of 1368 m ; surface is to be coated with a
checker pattern of evaporated aluminum film, (fraction, F) and white zinc-oxide paint (1 - F).
FIND: The fraction F for the checker pattern
KNOWN: Transmissivity of cover plate and spectral absorptivity of absorber plate for a solar
FIND: Absorption rate for prescribed solar flux and preferred absorber plate coating.
ASSUMPTIONS: (1) Solar irradiation of a
KNOWN: Directional absorptivity of a plate exposed to solar radiation on one side.
FIND: (a) Ratio of normal absorptivity to hemispherical emissivity, (b) Equilibrium temperature of
plate at 0 and 75 orientation relative to suns rays.
KNOWN: Irradiation of satellite from earth and sun. Two emissivities associated with the
FIND: (a) Steady-state satellite temperature when satellite is on bright side of earth for E/s > 1
and E/s < 1, (b) Steady-state satellite t
KNOWN: Rectangular plate, with prescribed geometry and thermal properties, for use as a radiator in
a spacecraft application. Radiator exposed to solar radiation on upper surface, and to deep space on
FIND: Using a computer-b
KNOWN: Space capsule fired from earth orbit platform in direction of sun.
FIND: (a) Differential equation predicting capsule temperature as a function of time, (b) Position of
capsule relative to sun when it reaches its destruction temperat
KNOWN: Solar irradiation of coated aluminum. Spectral absorptivities above and below cutoff
wavelength. Cutoff wavelength under normal conditions.
FIND: (a) Equilibrium temperature for normal conditions with c = 0.15 m. (b) Value of c that
KNOWN: Effective sky temperature and convection heat transfer coefficient associated with a thin
layer of water.
FIND: Lowest air temperature for which the water will not freeze (without and with evaporation).
ASSUMPTIONS: (1) St
KNOWN: Glass sheet, used on greenhouse roof, is subjected to solar flux, GS, atmospheric emission,
Gatm, and interior surface emission, Gi, as well as to convection processes.
FIND: (a) Appropriate energy balance for a unit area of the glas
KNOWN: Dimensions, spectral absorptivity, and temperature of solar receiver. Solar irradiation and
FIND: (a) Rate of energy collection q and collector efficiency , (b) Effect of receiver temperature on q
KNOWN: Dimensions of ten thin-walled thermosyphons with boiling, insulated, and
condensing sections of known lengths. Working fluid is saturated water at 0.047 bars.
FIND: (a) Heating rate delivered by thermosyphons if nucleate boiling heat
KNOWN: Inner surface of a vertical thin-walled container of length L and diameter D experiences
condensation of a saturated vapor. Container wall maintained at a uniform surface temperature by
flowing cold water across its outer surface.
KNOWN: Dimensions and surface temperature of grooved horizontal tube exposed to steam at 0.2
FIND: Minimum condensation and heat transfer rates per unit length of the tube.
Steam, 0.2 bar
S = 2 mm
D2 = 50 mm
t = 2 mm
Ts = 34C
KNOWN: Horizontal tube, 50mm diameter, with surface temperature of 34C is exposed to steam at
FIND: Estimate the heat transfer and condensation rates per unit length of the tube.
ASSUMPTIONS: (1) Laminar film condensation
KNOWN: Array of condenser tubes exposed to saturated steam at 0.1 bar.
FIND: (a) Condensation rate per unit length of square array, (b) Options for increasing the condensation
ASSUMPTIONS: (1) Spatially uniform cylinder temp
KNOWN: Thin-walled concentric tube arrangement for heating deionized water by condensation of
FIND: Estimates for convection coefficients on both sides of the inner tube. Inner tube wall outlet
temperature. Whether condensation provid
KNOWN: Horizontal tube 1m long with surface temperature of 70C used to condense steam at 1
FIND: Diameter required for condensation rate of 125 kg/h.
ASSUMPTIONS: (1) Laminar film condensation, (2) Negligible non-condensibles
KNOWN: Saturated ethylene glycol vapor at 1 atm condensing on a sphere of 100 mm diameter
having surface temperature of 150C.
FIND: Condensation rate.
ASSUMPTIONS: (1) Laminar film condensation, (2) Negligible non-condensibles in
KNOWN: Saturated steam condensing on the inside of a horizontal pipe.
FIND: Heat transfer coefficient and the condensation rate per unit length of the pipe.
ASSUMPTIONS: (1) Film condensation with low vapor velocities.
KNOWN: Saturation temperature and inlet flow rate of refrigerant. Diameter, length, and
temperature of tube.
FIND: Rate of condensation and outlet flow rate.
D = 0.03 m
L = 0.8 m
ASSUMPTIONS: (1) Negligible concentration of n
KNOWN: Mass flow rate and quality of R-22 condensing in tube. Tube diameter. Wall and
saturation temperatures. Refrigerant properties.
FIND: Heat transfer coefficient, heat transfer rate, and condensation rate for (a) X = 0.5, (b) 0.2 < X <