A large plane wall, with a thickness L and a thermal conductivity k, has its left surface ( x = 0 ) exposed. to a uniform heat flux q 0 . On the right surface ( x = L ) , convection and radiation heat transfer occur in a surrounding temperature of T ∞ . The emissivity and the convection heat transfer coefficient on the right surface are ε and h respectively. Express the boundary conditions and the differential equation of this heat problem during steady operation.
A large plane wall, with a thickness L and a thermal conductivity k, has its left surface ( x = 0 ) exposed. to a uniform heat flux q 0 . On the right surface ( x = L ) , convection and radiation heat transfer occur in a surrounding temperature of T ∞ . The emissivity and the convection heat transfer coefficient on the right surface are ε and h respectively. Express the boundary conditions and the differential equation of this heat problem during steady operation.
Solution Summary: The author explains the boundary condition and differential equation of heat conduction during steady operation.
A large plane wall, with a thickness L and a thermal conductivity k, has its left surface
(
x
=
0
)
exposed. to a uniform heat flux
q
0
. On the right surface
(
x
=
L
)
, convection and radiation heat transfer occur in a surrounding temperature of
T
∞
. The emissivity and the convection heat transfer coefficient on the right surface are
ε
and h respectively. Express the boundary conditions and the differential equation of this heat problem during steady operation.
Q2: (15 Marks)
A water-LiBr vapor absorption system incorporates a heat exchanger as shown in
the figure. The temperatures of the evaporator, the absorber, the condenser, and the
generator are 10°C, 25°C, 40°C, and 100°C respectively. The strong liquid leaving
the pump is heated to 50°C in the heat exchanger. The refrigerant flow rate through
the condenser is 0.12 kg/s. Calculate (i) the heat rejected in the absorber, and (ii) the
COP of the cycle.
Yo 8
XE-V
lo
9
Pc
7
condenser
5
Qgen
PG
100
Qabs
Pe
evaporator
PRV
6
PA
10
3
generator
heat exchanger
2
pump
185
absorber
Q5:(?
Design the duct system of the figure below by using the balanced pressure method.
The velocity in the duct attached to the AHU must not exceed 5m/s. The pressure
loss for each diffuser is equal to 10Pa.
100CFM
100CFM
100CFM
☑
☑
40m
AHU
-16m-
8m-
-12m-
57m
250CFM
40m
-14m-
26m
36m
☑
250CFM
A mass of ideal gas in a closed piston-cylinder system expands from 427 °C and 16 bar following the process law, pv1.36 = Constant (p times v to the power of 1.36 equals to a constant). For the gas, initial : final
pressure ratio is 4:1 and the initial gas volume is 0.14 m³. The specific heat of the gas at constant pressure, Cp = 0.987 kJ/kg-K and the specific gas constant, R = 0.267 kJ/kg.K.
Determine the change in total internal energy in the gas during the expansion. Enter your numerical answer in the answer box below in KILO JOULES (not in Joules) but do not enter the units. (There is no
expected number of decimal points or significant figures).
Chapter 2 Solutions
Heat and Mass Transfer: Fundamentals and Applications
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