Please answer the following Heat Transfer questions. I will up vote! Question 1) Hot air at 280°C flows through a 7 m l

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Please answer the following Heat Transfer questions. I will up
vote!
Question 1) Hot air at 280°C flows through a 7 m long
horizontal tube with a velocity of 0.9 m/s. The inside and outside
diameters of the tube are 5.9 cm and 6 cm. The outside heat
transfer coefficient is 12.5 W/m2 -°C and the ambient temperature
is 23°C. Neglecting wall thermal resistance, determine the rate of
heat transfer. Show a schematic diagram of the situation and axial
Temp variation diagram!
(1) Observations. (i) Hot air is cooled in a tube by losing heat
to an ambient fluid which is infinite in extent. (ii) The
temperature of the ambient fluid remains constant. (iii) The outlet
temperature of the hot fluid and the heat transfer rate are
unknown. Thus, this is a performance type heat exchanger problem.
(iv) The NTU method is suitable for solving this problem. (v) The
outside heat transfer coefficient is given but the inside
coefficient is unknown. (vi) The inside coefficient can be
determined from correlation equations for forced convection through
tubes.
Question 2) An air conditioning duct with a diameter of 30
cm passes horizontally through the attic of a house for a distance
of 5 m. The inlet air temperature is 8°C and the flow rate is 0.12
kg/s. The temperature in the attic during the summer is 42°C.
Determine the air outlet temperature and the rate of heat transfer
to the cold air. Neglect wall resistance.
(1) Observations. (i) This is a heat exchanger problem with
forced convection of cold air inside a horizontal duct and free
convection of air on the outside. (ii) Heat is added from the
ambient air to the cold air in the duct. (iii) Since the outlet
temperature of the cold fluid is unknown, it follows that this is a
performance type heat exchanger problem. Therefore, the NTU method
should be used to solve the problem. (iv) In the NTU method the
effectiveness gives one of the unknown outlet temperatures. (v) The
inside and outside heat transfer coefficients are unknown. They can
be determined from correlation equations. Show a schematic diagram
of the situation and axial Temp variation diagram!