Problem 12-1 - Example 12-1 A copper tube is soldered to...

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Example 12-1 A copper tube is soldered to the back of a solar collector, which is maintained at a uniform temperature of 75°C by incident sunlight. Water enters the tube at 25°C with a mass flow rate of 0.011 kg/s. Find the length of tube needed so that the exit temperature is 55°C. Solution: To find the heat transfer coefficient, first find the Reynolds number Re D ρ µ = V x mA = ± where x A is cross-sectional area Re x Dm A = ±
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o 25 55 40 C 22 ie mean TT T + + == = 4 kg viscosity(water, 40, 100) 6.53 10 ms TP µ = = × () 2 -4 kg 0.012 m 0.011 s Re 1787 kg 0.012 6.53×10 π m 2 ⎛⎞ ⎜⎟ ⎝⎠ Pr Prandtl(water, 40, 100) 4.33 = = Because Re < 2100, flow is laminar. We assume the tube is long enough so that the flow is fully developed. For laminar flow with constant wall temperature
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Problem 12-1 - Example 12-1 A copper tube is soldered to...

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