A fluid is heated from 25 to 75°C as it moves at 0.2 m/s through a straight thin-walled stainless steel tube of 12.7-mm diameter. A uniform heat flux is maintained by an electric resistance heater wrapped around the outer surface of the tube. If the tube is 10 m long, what is the required heat flux? If fluid enters the tube with a fully developed velocity profile and a uniform temperature profile, Using the attached charts, what is the surface temperature at the tube exit and at a distance of 0.5 m from the entrance? Fluid properties may be approximated as p =1000 kg/m³, cp = 4000 J/kg K, μ =2 × 10-³ kg/s.m. k = 0.8 W/mK, and Pr = 10. 20 10 8. Thermal entry length Combined entry length (P=0.7) Constant surface heat flux 100 40 Combined entry length [2] O Pr= 0.7 Pr=2 A Pr = 5 Equation 8.58 Nup 4 2 Constant surface temperature Entrance Fully developed region region 4.36 10 3.66 ° Equation 8.57 4 or numerator of 8.58 Fully Entrance developed region region 3.66 1 1 0.001 0.01 0.1 0.5 1 0.001 0.01 0.1 1 0.005 0.05 0.05 x/D x/D = RepPr = Gzp -= Gzp RepPr (a) Results obtained from entry length solutions for laminar flow in a circular tube with constant surface temperature: (a) Local Nusselt numbers. (b) Average Nusselt numbers.