Question

A spherical tank, 1.5 m in diameter, is maintained at a
temperature of 120 ◦C and exposed to a convection environment with
heat transfer coefficient, *h*=15 W*/*m^{2}
◦C and *T*_{∞} =20 ◦C. For the same surface
temperature of the tank, it is desired to insulate the tank in
order to decrease the heat loss by 45 percent, determine the
thickness of insulation layer (k=0.2 W/m ◦C ) and the outer surface
temperature.

Answer #1

A flat wall is exposed to an environmental temperature of 38
degrees C. The wall is covered with a layer of insulation 2.5 cm
thick whose thermal conductivity is 1.8 W/(m.K), and the
temperature of the wall on the inside of the insulation is 320
degrees C. The wall loses heat to the environment by convection.
Compute the value of the convection heat transfer coefficient that
must be maintained on the outer surface of the insulation to ensure
that the...

2.1Consider a solid cylindrical rod of length 0.15 m and
diameter 0.05 m. The top and bottom surfaces of the rod are
maintained at constant temperatures of 20oC and 95oC, respectively,
while the side surface is perfectly insulated. 2.1.1 Draw a diagram
to represent the situation described above. (3) 2.1.2 Determine the
rate of heat transfer through the rod if it is made of copper, k =
380 W/m? oC. (4) 2.1.3 Determine the rate of heat transfer through
the...

In a steel spherical reactor with a heat transmission
coefficient (10 + X) W / mK, water is boiled at 350 oC. The inner
diameter of the tank is 80 cm and the wall thickness is (5+ (X /
2)) cm. This tank is insulated with (X) cm thick concrete (k = 2.5
W / mK).
Outdoor heat transfer coefficient (10+ (X)) W / m2K, indoor heat
transfer coefficient is 500 W / m2K. Calculate both surface
temperatures of the...

A 1 m outer diameter spherical tank made of AISI 304 steel with
10 cm wall
thickness contains solid iced water at 0°C. Air at 25°C flows
outside the tank with a
velocity of 1 m/s. Determine the rate of heat transfer to the tank
and the mass rate (
m_dot) at which ice melts. Ignore convection effects of the melting
ice.
The latent heat of fusion of water at 0°C is 333.7 kJ/kg.
Thanks!

Steam at an average temperature of ?∞= 400°C flows through a
steel pipe. The inner and outer radii of the pipe are r1 = 4 cm and
r2 = 4.5 cm, respectively, and the outer surface of the pipe is
insulated with a layer of 50 mm thick-calcium silicate of thermal
conductivity of k = 0.5 W/m.K, and is maintained at 350 °C. If the
convection heat transfer coefficient on the inner surface of the
pipe is h = 65...

A spherical object (50 cm diameter, c=0.46 kJ/kg*C, k = 42
W/m*C, density = 7800 kg/m3 ) is initially at a uniform temperature
of 450 C. It is suddenly placed in a constant temperature
environment of 100 C. The convection transfer coefficient is 500
W/m2*C. How long would it take for temperature in the center of the
sphere to cool down to 150 C? Note: Bi for a sphere is
(hD)/(6k).Suggestion: First calculate Biot number, then determine
if T is...

Water flows through a pipe at an average temperature of
T =50°C. The inner and outer radii of the pipe are
r1 = 6 cm and r2 = 6.5 cm,
respectively. The outer surface of the pipe is wrapped with a thin
electric heater that consumes 300 W per m length of the pipe. The
exposed surface of the heater is heavily insulated so that the
entire heat generated in the heater is transferred to the pipe.
Heat is transferred...

A fin of rectangular profile has a thermal conductivity of 14
W/m C, thickness of 2.0 mm, and length of 23 mm. The base of the
fin is maintained at a temperature of 220 o C while the fin is
exposed to a convection environment at 23 o C with h=25 W/m2 o C.
Calculate heat lost per meter of fin depth for the three tip
conditions. (a) Convection, (b) Adiabatic, and (c) T (x=L) = 23 o
C.

a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is
exposed to cooling airflow at 27 0C resulting in the convective
coefficient, h = 114 W/ m2 K. The relevant properties of mild steel
are given as follows: Density , /7850 2 mkg Specific heat K kgJc
p / 475 and thermal diffusivity hr m /043.0 2 Determine: (i)
Time required to cool the sphere (lumped parameter system) from 540
0C to 950C. [7...

a. Discuss why car inside temperature is high when you park the
car outside in a sunny day even under the shade and the relation
with glass transmissivity (Greenhouse effect). [5 marks]
b. A double walled spherical tank is used to store iced water at
O'C. The tank internal diameter is 2 m and wall thickness is 0.5
cm. The inner and outer walls are separated with the 2 cm thick
space. The air between the two walls of the...

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