PROBLEM 6.33
KNOWN: Freestream velocity and average convection heat transfer associated with uid
ow over a surface olprescribed characteristic length.
FIND: Values of WL , ReL, Pr, 3H for (a) air, (b) engine oil, (c) mercuiy, (d) water.
SCHEMATIC: Fl' : I
STATE UNIVERSITY OF NEW YORK AT BUFFALO
DEPARTMENT OF MECHANICAL & AEROSPACE ENGINEERING
MAE 336, Heat Transfer (16248)
Professor Joseph C. Mollendorf, PhD, FASME
February 18, 2013
8:00 8:50 am
* EXAM 1 *
Question sheets must be turnedin with answer shee
PROBLEM 12.123
KNOWN: Sky, ground, and ambient air temperatures. Grape of prescribed diameter and properties.
FIND: (a) General expression for rate of change of grape temperature, (b) Whether grapes will freeze
in quiescent air, (c) Whether grapes will fr
PROBLEM 13.27
KNOWN: Dimensions and temperature of a rectangular fin array radiating to deep space.
FIND: Expression for rate of radiation transfer per unit length from a unit section of the array.
SCHEMATIC:
ASSUMPTIONS: (1) Surfaces may be approximated
PROBLEM 13.48
KNOWN: Dimensions of attic. Emissivity of aluminum foil and of surfaces prior to application of
the foil .
FIND: (a) Reduction of radiation heat transfer from the hot roof to the attic floor if foil is installed on
the bottom of the roof, (b
PROBLEM 12.3
KNOWN: Thickness and temperature of aluminum plate. Irradiation. Convection conditions.
Absorptivity and emissivity.
FIND: Radiosity and net radiation heat flux at top plate surface, rate of change of plate temperature.
T = 30C
h = 40 W/m2K
S
PROBLEM 11.44
KNOWN: Pressure and initial flow rate of water vapor. Water inlet and outlet temperatures. Initial
and final overall heat transfer coefficients.
FIND: (a) Surface area for initial U and water flow rate, (b) Vapor flow rate for final U.
SCHEM
PROBLEM 11.27
KNOWN: Cooling milk from a dairy operation to a safetostore temperature, Th,o 13C, using
ground water in a counterflow concentric tube heat exchanger with a 50mm diameter inner pipe and
2
overall heat transfer coefficient of 1000 W/m K.
F
PROBLEM 5.25
KNOWN: Diameter and thermophysical properties of alumina particles. Convection conditions
associated with a twostep heating process.
FIND: (a) Timeinflight (tif) required for complete melting, (b) Validity of assuming negligible
radiation
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