(b) Write an expression defining the friction factor f using the hydraulic dia

(b) Write an expression defining the friction factor f using the hydraulic diameter Dh as the characteristic length. What is the hydraulic diameter for the parallel-plate channel?
(c) The friction factor is estimated from the expression f= C/ReDs where C depends upon the flow cross section as shown in Table 8.1. What is the coefficient C for the parallel-plate channel?
(d) Air flow in a parallel-plate channel with a separation of 5 mm and a length of 200 mm experiences a pressure drop of ?p = 3.75 N/m2. Calculate the mean velocity and the Reynolds number for air at atmospheric pressure and 300 K. Is the assumption of fully developed flow reasonable for this application? If not what is the effect on the estimate for um?