Question

**1.** An oven chimney is
made of brick with a heat transmission coefficient 1.1 W/mK 10 cm
thick. Since the shaft exterior radiation beam coefficient is 0.8
and the flue gas temperature is 350°C, the external ambient
temperature is 25°C and the outer ambient heat transport
coefficient is 20 W/m^{2}K;

a) Calculate the shaft exterior temperature.

b) In order to reduce the risk of burn injury that may occur in the body, the shaft is asked to be below 55°Cve of the external surface temperature of the chimney. Accordingly, what should be the minimum thickness of the chimney?

**2.** Initially, the
aluminum sphere with a diameter of 15 cm with a temperature of
200°C was left to cool in the airflow at a temperature of 6 m/s. By
making the necessary acceptances, calculate the amount of time the
aluminum sphere will fall to a temperature of 50°C.

The relevant correlation for forced transport on the sphere;

Nu_{D} = 2 + (0.4
Re_{D} ^{0.5}+ 0.06 Re_{D} ^{2/3})
Pr ^{0.6} (μo/μy)^{1/4}

**3.** The temperature of
parallel plates of two infinity lengths is 575oC and 25oC, and the
radiation scalpel coefficient is 0.85 and 0.75 respectively. To
reduce the heat radiation between these two sheets by 5 times, find
the radiation scalpel coefficient (per) of the radiation shield to
be placed.

**4.** Two separate fins
are mounted on a plate with a base temperature of 100°C and a size
of 1m x 1m. The ambient temperature is 20°C and the heat transport
coefficient is 35 W/m^{2} K. The diameter of the second
wing, which is fixed to the same surface, is 4 mm and the heat
transmission coefficient is 90 W/mK and to give the environment the
same amount of heat in both wings; length of the second wing;

a) According to the acceptance of the tip isolated fin,

b) According to the acceptance that
there is a heat transport of 35W/m ^{2} K at the end of the
fins,

c) What should be according to the acceptance that there is a constant temperature of 80°C at the end of the fins?

**5.** We aim to hold
graduation meetings with your families in the A21 classroom where
we process the Pre-Pandemia Heat Transfer course. About 100 people
attended the ceremony in the classroom measuring 15m x 20m x 10 m
and the internal ambient temperature is 20°C due to the working air
conditioning device. Let's face it, the air conditioning device
malfunctions and each person in the living room gives an average
temperature of 350 kJ per hour. Find the classroom temperature at
the end of 30 minutes, acknowledging that the living room walls did
not receive heat or pass and that the air conditioning was not
working for 30 minutes.

**6.** Where you are now,
you want to have tea while solving questions. The water, which is
found in a thin steel teapot with a diameter of 12 cm, is boiling.
The heat transport coefficient between the teapot base and the
boiling water is 10 kW/m^{2}K. Since the heat flow ingrair
is 40 kW/m^{2;}

a) Find the surface temperature of the teapot base.

b) Find the heat given to the water for 30 minutes and the amount of water evaporated.

Answer #1

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...

(Heating Transfer)
- A wall with a heat transmission coefficient of 2 W /
mK; thickness, width and height values are all 1 m (wall
thickness 1 m and heat transfer area 1 mx 1 m = 1 m ^ 2) In the
continuous regime, the relevant wall with inner surface temperature
of 2000 K and outer surface temperature of 1000 K , unit Calculate
the heat passing in time.
(Admissions: one dimensional heat conduction and
constant heat conduction coefficient...

The wall of an industrial furnace is constructed from a fireclay
brick layer which is covered with another layer of ordinary brick.
The outer surface wall temperature has a steady-state temperature
of 110 °C when the ambient air has a temperature of 20°C. Heat is
lost from the outer surface wall via convection and radiation. The
internal furnace wall has a surface temperature of 500 DegreeC.
Convection heat transfer coefficient between outer wall and air:
5 W/m2K
Stefan-Boltzmann constant σ:...

800 W/m3 of heat is generated within a 10 cm diameter nickel-
steel sphere for which k = 10 W/m·K. The environment is at
20◦C and there is a natural convection heat transfer coefficient of
10 W/m2K around the outside of the sphere. What is its center
temperature at the steady state? [21.37◦C.]

4.1A membrane made of 0.1 mm thick soft rubber separates pure O2
at 1 atm and 25oC from air at 1.2 atm pressure. Determine the mass
flow rate of O2 through the membrane per unit area and the
direction of flow.
Molar flow rate of oxygen is given by: ???? = ???????? / ???
(????1 ? ????2 )
where S is solubility of oxygen in rubber.
The mass diffusivity of oxygen in rubber at 298 K is DAB = 2.1...

ADVERTISEMENT

Get Answers For Free

Most questions answered within 1 hours.

ADVERTISEMENT

asked 3 minutes ago

asked 11 minutes ago

asked 11 minutes ago

asked 12 minutes ago

asked 20 minutes ago

asked 20 minutes ago

asked 31 minutes ago

asked 34 minutes ago

asked 35 minutes ago

asked 40 minutes ago

asked 43 minutes ago

asked 51 minutes ago