Moisture Attenuation by Means of Small Synthetic Jets

This work reports the results of experimental investigations carried out on a submerged synthetic jet obtained through the use of a headset speaker piloted with an appropriate sinusoidal signal at a frequency of 380 Hz. The purpose of making such a device is to obtain a manufacture that can improve human comfort, in cases where there is prolonged contact of parts of the human body with fabric and/or padding such as, for example, in the case of professional drivers or in the case of patients immobilized in bed for long periods and who may develop sores from decubitus. The study begins with the construction of a device that, exploiting the well-known transport properties of impacting jets, was able to improve local ventilation and the removal of excess moisture, due to the natural transpiration of human skin in people forced to assume the same position for prolonged periods such as professional drivers; bedridden patients; etc. It is essentially imposed upon subjects to have portions of their own bodies in contact with materials and coverings that obstruct typical skin transpiration conditions. The structure of the synthetic jets was studied in advance of the experimental activity, which subsequently involved building a sponge mat with 80 separate jets. Semi-empirical tests were conducted on this sponge mat to see how well distilled water could remove moisture from a cloth.

The experimental investigations were first carried out using the PIV technique, and, subsequently, the synthetic jet was visualized using the Background-Oriented Schlieren (BOS) technique which allowed to test the presence of the jets, installed directly on the mattress, in a relatively simple and fast way, requiring a very simplified set-up. The first series of empirical tests were carried out to verify the ability to remove moisture from a fabric, previously soaked in distilled water, exposed to the action of the synthetic jets made. The results of these latest tests, although encouraging, require further analyzes to be carried out quantitative information, like the moisture evaporation rate, under controlled environmental humidity and temperature.