8.55 A laminar flow meter for measuring air flow is constructed of small diameter (0.2 cm) tubes that are 20 cm long. For an upper limit on the Reynolds number needed to maintain laminar flow of 1800, determine the number of tubes needed for an air flow rate of 0.04 m3/s. Determine the overall pressure drop accounting for the entrance and exit losses of the tubes. Show that the pressure drop is essentially linear with flow rate.