Question

A 12 meter long and 12 mm inner diameter smooth pipe is used to heat a liquid in an industrial process. The liquid enters the pipe at a temperature of 25o C and a mean velocity of 0.80 m/s. A uniform heat flux is maintained by an electric resistance heater wrapped around the outer surface of the pipe so that the fluid exits at 75o C. The fluid average properties are ? = 1000 kg/m3 , Cp = 4000 J/kg·K, µ = 2x10?3 kg/m·s, and k = 0.48 W/m·K. Calculate: (a) The required surface heat flux produced by the heater; (b) The surface temperature at the exit; (c) The pressure drop through the pipe and the power required to overcome the flow resistance.

Answer #1

(a) Fluid at a mass flow rate of 0.352 kg/s flows through a tube
with a diameter of 15 mm and a length of 25 m. The inner surface of
the tube is heated with a uniform heat flux of 1000 W/m2.
Measurements shown that the inlet temperature of the fluid is 30
˚C. Assume the outer surface of the tube is perfectly insulated.
Consider the thermophysical properties of the fluid are as follows:
density ρ = 1000 kg/m3, specific...

A concentric tube heat exchanger is comprised of a stainless
steel (ks = 40 W/mK) inner pipe, NPS 2- nominal schedule
40 size (corresponding to an inner diameter of 52.5 mm and an outer
diameter of 60.3 mm), and an outer stainless steel pipe of NPS
3-nominal schedule 40 (ID = 77.9 mm, OD = 88.9 mm). The heat
exchanger has an effective length of 35 m.
The inner pipe fluid is ammonia (?a = 0.3 · 10?6
m2/s, cpa...

A concentric tube heat exchanger is comprised of a stainless
steel (ks = 40 W/mK) inner pipe, NPS 2- nominal schedule
40 size (corresponding to an inner diameter of 52.5 mm and an outer
diameter of 60.3 mm), and an outer stainless steel pipe of NPS
3-nominal schedule 40 (ID = 77.9 mm, OD = 88.9 mm). The heat
exchanger has an effective length of 35 m.
The inner pipe fluid is ammonia (va = 0.3 ·
10-6m2/s, cpa =...

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