In: Physics
A blood transfusion is being set up in an emergency room for an accident victim. Blood has a density of1060 kg/m3 and a viscosity of 4.0
Answer:
The idea here is to assume Poiseulle flow, so that the
relation between pressure differential ?p, flow rate Q, radius of
the circular cross section R, length of the needle L and viscosity
? is
Q = ? ?p R? / ( 8 ? L)
Solving for pressure differential this gives
?p = 8 ? L Q / (? R?).
But in the hydrostatic case ( valid here for slow flow) we
know
?p = ? g ?h
Therefore
?h = 8 ? L Q / (? g ? R?).
With the give data this calculates to
?h = 8* 4.0*10^-3 kg/(m s) * 0.030 m * 4.4*10^-8 m^3/s /(
1060kg/m^3 * 9.81m/s^2*3.1415*(25*10^-5 m)^4)
= 33cm
Extra points:
Requirements for setting up a Blood Transfusion
References: http://www.shb.scot.nhs.uk/board/policies/BloodTransfusionProcedures.pdf