Question

Water at an average temperature of 107°C and an average velocity of 3.5 m/s flows through a 5-m-long stainless steel tube (k = 14.2 W/m · °C) in a boiler. The inner and outer diameters of the tube are Di =1.0 cm and Do = 1.4 cm, respectively. If the convection heat transfer coefficient at the outer surface of the tube where boiling is taking place is ho= 8400 W/m2 · °C, determine the overall heat transfer coefficient Ui of this boiler based on the inner surface area of the tube. Take υ=0,268 x 10-6 m2/s, k=0,682 W/m.K, Pr=1,58 for water at 107 ºC. Neglect fouling resistance at the inner and outer part of the tube. a) 3500 W/m^2.C b) 5887 kW/m^2.C c) 5887 W/m^2.C d) 3501 kW/m^2.C e) 5887 kW

          Water at an average temperature of 107°C and an average velocity of 3.5 m/s flows through a 5-m-long stainless steel tube (k = 14.2 W/m · °C) in a boiler. The inner and outer diameters of the tube are Di =1.0 cm and Do = 1.4 cm, respectively. If the convection heat transfer coefficient at the outer surface of the tube where boiling is taking place is ho= 8400 W/m2 · °C, determine the overall heat transfer coefficient Ui of this boiler based on the inner surface area of the tube. Take υ=0,268 x 10-6 m2/s, k=0,682 W/m.K, Pr=1,58 for water at 107 ºC. Neglect fouling resistance at the inner and outer part of the tube.

a) 3500 W/m^2.C
b) 5887 kW/m^2.C
c) 5887 W/m^2.C
d) 3501 kW/m^2.C
e) 5887 kW

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University Physics with Modern Physics

Hugh D. Young 14th Edition

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Solved by Expert Nicholas Mogoi

01/08/2024

Step 1

The thermal resistance of the tube wall can be calculated using the formula: R_wall = ln(Do/Di) / (2πkL) where ln is the natural logarithm, Do is the outer diameter of the tube, Di is the inner diameter of the tube, k is the thermal conductivity of the tube Show more…

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Water at an average temperature of 107°C and an average velocity of 3.5 m/s flows through a 5-m-long stainless steel tube (k = 14.2 W/m · °C) in a boiler. The inner and outer diameters of the tube are Di =1.0 cm and Do = 1.4 cm, respectively. If the convection heat transfer coefficient at the outer surface of the tube where boiling is taking place is ho= 8400 W/m2 · °C, determine the overall heat transfer coefficient Ui of this boiler based on the inner surface area of the tube. Take υ=0,268 x 10-6 m2/s, k=0,682 W/m.K, Pr=1,58 for water at 107 ºC. Neglect fouling resistance at the inner and outer part of the tube. a) 3500 W/m^2.C b) 5887 kW/m^2.C c) 5887 W/m^2.C d) 3501 kW/m^2.C e) 5887 kW

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Transcript

00:01 Okay, so t average we are having at 107 degrees celsius.

00:07 Ferral velocity we are having at 3 .5 meters per second.

00:12 We are having a length of 5 meters.

00:18 K is 14 .2.

00:22 Then diameter inner is 1 .0 centimeters.

00:27 Outer diameter is 1 .4 centimeters.

00:31 Coefficient for that is 800.

00:42 We need to find the transfer coefficient ui for that boiler.

00:57 Now remember that the temperature should be in kelvin.

01:02 So make this 380 k.

01:07 Everything else is sorted out.

01:14 Now we need to find the flow through the tube.

01:18 Because we need to first find the reynolds number for that.

01:22 And remember we also need to include viscosity.

01:26 As 1 .23 into 10 to minus 5 in density.

01:32 For that we are looking at thermophysical property tables of saturated water.

01:39 0 .748 kilogram cubic meter.

01:46 These are properties at 380 k.

01:49 So if we go ahead and calculate the reynolds number.

01:51 We are going to have the density multiplied by velocity...

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