Question: A 4-m-long tube is subjected to uniform wall heat flux. The tube has an inside diameter of 0.0149 m and a flow rate of 7.8 × 10-5 m3/s. The liquid flowing inside the tube is ethylene glycol-distilled water mixture with a mass fraction of 0.5. Determine the apparent (developing) friction factor at the location x/D = 20 if the inlet configuration of the tube is:
(a) re-entrant and
(b) square-edged. At this location, the local Grashof number is Gr = 28,090 and the properties of the mixture of distilled water and ethylene glycol are: Pr = 20.9, v = 2.33 × 10-6 m2 /s, and µb/µs = 1.25.