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Fluido – Design of a heater for blood and fluid using CFD simulation

Goal: The Surgical Company has introduced the Fluido ®. With this medical device, blood and fluids can be heated in a controlled way. It is used in hospitals during operations when patients require a blood transfusion. The Fluido ® can be a life saver when the blood is added at body temperature instead of room temperature, or even lower, especially when the patient requires a large quantity of blood.

Demcon Advanced Mechatronics BV and Indes have developed and optimised a new heating principle and temperature control. The device contains a disposable with a liquid which is heated up to body temperature with Infrared Radiation (IR) before it can be injected in the patient’s blood circulatory system. The liquid may consists of a saline, but also of a blood like substance with 60 volume percent red blood cells, refered to as blood plasma.

More information can be found at www.fluido.nl.

Approach: During the development of the blood heater it appeared that the flow pattern in the disposable is critical during the heating process. In previous experiments is was found that due to ‘dead’ zones and recirculation regions in the disposable, some red blood cells became too ‘hot’, leading to a risk of degradation of these blood cells.

In this study the geometry and the flow pattern of the disposable have been optimised, in order to remove these recirculation and dead zones and to improve mixing of the fluid. A main focus in this study is the reduction of the ‘dead’ zones in a single flow turn in the disposable.

The flow was optimised using CFD-calculations with the use of ANSYS CFX. We started with the comparison of CFD-results with experiments to obtain the correct settings for the CFD-calculations. Subsequent calculations were performed on geometries that were defined based on advancing insight.

Results: Different geometries have been investigated. First the flow turn has been optimised such that the recirculation region disappeared. Subsequently, vanes have been added in the flow turn to improve mixing between cold and hot regions. As a criterium for the performance, the flow and temperature variance on the outlet area of the disposable have been used. In the final design, the flow and temperature variance have significantly been reduced. This is considered a major improvement.

The final geometry was tested experimentally. This product performed very well and eventually led to a successful market introduction. The Surgical Company obtained a patent on the final geometry, which ensures protection of their Fluido®. The Surgical Company is now given the opportunity to earn back their investments and make profit. Recently, the Fluido® was granted CE-mark, which means that the fluido can be sold worldwide. Also, the Fluido® is CF (Cardiac Floating), which is the strictest electrical safety degree. As a result the Fluido® can be applied everywhere, on all catheters and central lines (artery and veins), and even directly into the heart.

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