Pump casting polycarbonate fig1 revolution from sorin

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Pump Casting PolycarbonateFig1. REVOLUTION from SORIN groupFlow rateThe blood flow is defined as amount of blood flowing at a given cross section at any time.The sufficient flow rate of blood must be maintained. In this product, the flow is generatefrom the rotation of the blades within the pumping chamber. It is important to minimise theheat generation while giving a sufficient flow rate therefore, the minimal RPM is desiredwithin the product.There are various ways to control the flow rate such as rotational speed and shape of theoutlet. The flow rate formula Q=VA can be used to determine the mechanics of the pump.V = velocity of the fluid, A= cross sectional area of the outletBy adjusting the shape, the flow rate can be controlled at desired performance.Page | 11
Pressure Using the Bernoulli’s equation, it is possible to find relationship between flow rate and pressure within the pump. lossEAhzggPzggP2222Fig2. Bernoulli’s equation. (Source: textbook)If the sum of the three heads are constant and the pump is at stationary position, it isassumable that the pressure head must be increased to follow decrease in the velocity head.Therefore, where the low velocity occurs there is a high pressure. Shear stressShear stress along the pump can cause hemolysis and puts the occupant’s life in the danger. Inhuman blood system the blood flow in laminar flow. Using the shear stress formula forlaminar flow below, it can be said that high velocity of the flow will increase the shear stress. There are some issue concerning with the shear stress because red blood cells transportingoxygen throughout the human body. Hemolysis occurs in the human body due to high shearstress and a winding flow path.Thrombus is the development in which a fibrous clot occurs in either a blood vessel or in achamber in the heart. Thrombus formation occurs in areas of high shear stress,biocompatibility and stagnation.PowerThe power supply for the blood pump can be affected by various factors such as RPM,efficiency and torque. In the designing state of the pump, those factors has to be closelyexamined so that the final product is practical for the desired application.T=Fd2T = Torque; d = diameter; F = ForceCalculation of FF=τAreaPage | 12
Calculation of ττ=μrwhµ = Fluid Viscosity; r = radius; w = rpm; h = lengthTorque produced byT=2πμw r44hT = Torque; µ = Fluid Viscosity; w = rpm; r = diameter; h = heightTherefore, Power is calculated byP=TwP = Power; T = Torque; w = rpmBatteries must be able to maintain a steady level for a long time to ensure that the heart doesnot fail. The fluctuation of power in a blood pump can result in generating fluctuation inpressure and increase in flow. This can damage to the red blood cells.