An experiment is designed to study microscale

Chapter 8, Problem 8.115

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An experiment is designed to study microscale forcedconvection. Water at Tm,i?300 K is to be heated in a straight, circular glass tube with a 50-?m innerdiameter and a wall thickness of 1 mm. Warm water atT??350 K, V?2 m/s is in cross flow over the exte-rior tube surface. The experiment is to be designed to cover the operating range 1?ReD?2000, whereReDis the Reynolds number associated with the inter-nal flow.(a) Determine the tube length Lthat meets a designrequirement that the tube be twice as long as thethermal entrance length associated with the high-est Reynolds number of interest. Evaluate waterproperties at 305 K.(b) Determine the water outlet temperature, Tm,o, thatis expected to be associated with ReD?2000.Evaluate the heating water (water in cross flowover the tube) properties at 330 K.(c) Calculate the pressure drop from the entrance tothe exit of the tube for ReD?2000.(d) Based on the calculated flow rate and pressuredrop in the tube, estimate the height of a columnof water (at 300 K) needed to supply the neces-sary pressure at the tube entrance and the timeneeded to collect 0.1 liter of water. Discuss how the outlet temperature of the water flowingfrom the tube, Tm,o, might be measured.