An experiment is designed to study microscale forced convection. Water at Tm,i = 300 K is to be heated in a straight, circular glass tube with a 50-µ,m inner diameter and a wall thickness of 1 mm. Warm water at Too = 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, where ReD is the Reynolds number associated with the inter- nal flow.
(a) Determine the tube length L that meets a design requirement that the tube be twice as long as the thermal entrance length associated with the high- est Reynolds number of interest. Evaluate water properties at 305 K.
(b) Determine the water outlet temperature, Tm,o, that is expected to be associated with ReD = 2000. Evaluate the heating water (water in cross flow over the tube) properties at 330 K.
(c) Calculate the pressure drop from the entrance to the exit of the tube for ReD = 2000.
(d) Based on the calculated flow rate and pressure drop in the tube, estimate the height of a column of water (at 300 K) needed to supply the neces- sary pressure at the tube entrance and the time needed to collect 0.1 liter of water. Discuss how the outlet temperature of the water flowing from the tube, Tm,o, might be measured.