Background
When the heart cannot fully contract, less oxygen-rich blood is delivered to organs and tissues in the body, which can lead to organ failure and eventually death. A left ventricular assist device (LVAD) supports the heart by increasing blood flow from the left ventricle to the aorta. A novel LVAD is being developed that consists of an inflatable balloon, which is placed in the left ventricle via a small insertion in the groin. The balloon is actuated at high frequencies by making use of a diaphragm pump, which is placed next to the patient’s bed and is connected to the balloon with a catheter filled with helium. The diaphragm pump can inflate the balloon by compressing the helium and deflate the balloon with expansion of the helium. Actuating the diaphragm at high frequencies generates heat in the pressure chambers of the pump due to friction. However, the maximum temperature of parts of the system that can come into contact with a patient or medical personal, cannot exceed 41◦C according to medical regulation. Therefore, the aim of this project is to create a concept design for cooling the helium gas flow used to inflate and deflate an intraventricular balloon at high frequencies for a novel left ventricle assist device.

Method
First, an overview of existing cooling techniques is created. Eight of the 24 cooling techniques explored met the list of requirements. These eight techniques are assessed against the list of weighted criteria using the Harris profile method. A concept design is created for the three best scoring techniques: thermoelectric cooling, vortex cooling, and forced convection using air for which the forced convection concept design appears to be most feasible. The final cooling concept features two air fans blowing air through a heat sink incorporated in the aluminium base structure around the pressure chambers. To verify the concept, a (simplified) simulation model is created in Ansys Fluent.

Results
The simulation model is used to simulate air flow through the channels and heat conduction in the base structure around the pressure chambers. The optimal fan velocity is determined by analysing the pressure drop and the temperature behaviour of the system. Furthermore, the model is 3D printed in plastic to validate the simulation model by performing velocity and pressure tests. Since the test results match the simulation results, the simulation model is considered validated.

Conclusion
In conclusion, after assessing different cooling techniques, a concept based on forced convection is developed in detail. The design is verified with a simulation model, and the simulation results are validated with a 3D printed plastic model. Although the concept design allows for room for optimization, it has proven to be a feasible solution for cooling the pressure chambers, and thus the helium gas, in the diaphragm pump of the novel LVAD.