Abstract
This article presents an improved Filtering Facepiece Respirator (FFR) designed to increase the comfort of wearers during low-moderate work. The improved FFR aims to lower the deadspace temperature and CO2 level by an active ventilation fan. The reversing modeling is used to build the 3D geometric model of this FFR; the Computational Fluid Dynamics (CFD) simulation is then introduced to investigate the flow field. Based on the simulation result, the ventilation fan of the improved FFR can fit the flow field well when placed in the proper blowing orientation; streamlines from this fan show a cup-shape distribution and are perfectly matched to the shape of the FFR and human face when the fan blowing inward. In the deadspace of the improved FFR, the CO2 volume fraction is controlled by the optimized flow field. In addition, an experimental prototype of the improved FFR has been tested to validate the simulation. A wireless temperature sensor is used to detect the temperature variation inside the prototype FFR, deadspace temperature is lowered by 2 K compared to the normal FFR without a fan. An infrared camera (IRC) method is used to elucidate the temperature distribution on the prototype FFR's outside surface and the wearer's face, surface temperature is lowered notably. Both inside and outside temperature results from the simulation are in agreement with experimental results. Therefore, adding an inward-blowing fan on the outer surface of an N95 FFR is a feasible approach to reducing the deadspace CO2 concentration and improve temperature comfort.
Highlights
Filtering Facepiece Respirators (FFR) are commonly used to protect users from inhaling contaminant particles
[10] The essence of this idea is to replace the breathing pressure-driven valve with a battery-driven fan so that the deadspace ventilation can be ensured at any respiratory rate. Research on this issue is limited; a published Computational Fluid Dynamics (CFD) study used a model with a simplified axial fan placed across the filter facepiece, and results show that the deadspace CO2 level is lowered
This study presents a design of FFR ventilation fan to lower the FFR deadspace CO2 level and temperature; CFD simulation and experiment validation was introduced to test this design
Summary
Filtering Facepiece Respirators (FFR) are commonly used to protect users from inhaling contaminant particles. In order to dissipate the heat and CO2 from the deadspace of N95 FFRs, a kind of one-way valve called an exhalation valve (EV) is added. [10] The essence of this idea is to replace the breathing pressure-driven valve with a battery-driven fan so that the deadspace ventilation can be ensured at any respiratory rate. Research on this issue is limited; a published CFD study used a model with a simplified axial fan placed across the filter facepiece, and results show that the deadspace CO2 level is lowered. Research on this issue is limited; a published CFD study used a model with a simplified axial fan placed across the filter facepiece, and results show that the deadspace CO2 level is lowered. [10] placing the fan across the filter facepiece destroys the initial structure of an N95 FFR and may introduce new problems, such as the decrease of filter efficiency and the increase of cost
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