A patient is to be given a blood transfusion. The blood is to flow through a tube from a raised bottle to a needle inserted in the vein . The inside diameter of the 4.8 cm long needle is 0.48 mm, and the required flow rate is 4.9 cm/3 of blood per minute.

Question

How high should the bottle be placed above the needle? Use pblood = 1.05x10^3 and nblood = 4.0x10E-3 Pa*s. Assume the blood pressure is 18 torr above atmospheric pressure.

Answer 1

I don't understand what nblood is supposed to represent. The units are pressure, but what you need for this problem is a viscosity.

The main flow constriction, where the pressure drop occurs, is the needle. There is a law
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that relates laminar viscous fluid flow in narrow passages to pressure drop and viscosity. That is what you seem to need for this problem.