A micro-scale pressure drop model for microfibrous entrapped catalysts (MFEC) is constructed based on experimental scanning electron microscope (SEM) images using computational fluid dynamics (CFD). This model investigates the separate contributions of fibers, entrapped particles, particle shape factors and the compressibility of MFEC to the total pressure drop in a high air velocity condition. A theoretical calculation is conducted to determine the flow type within the MFEC. Top view and side view SEM images of MFEC are taken to reproduce their 3D geometric structure, which significantly improves the accuracy of the model compared with other simplified models. Volume loading of fibers and entrapped particles, as well as media compressibility, are found to be major contributors to pressure drop. In an effort to reduce pressure drop, two types of leading-edge/trailing-edge filter fairings are also studied. Triangle fairings added to the leading edge and trailing edge of MFEC decrease pressure drop, especially at higher face velocities.Keywords: pressure drop; computational fluid dynamics (CFD); scanning electron microscope (SEM); microfibrous entrapped catalysts (MFEC)

Weight- and volume-sensitive systems such as aircraft require restrictive ducting, which leads to high face velocities (10–40 m/s) in reactive structures. A head-to-head comparison was conducted experimentally among packed beds (estimated data), monoliths, and microfibrous entrapped catalysts (MFECs) during ozone decomposition to investigate the effects of system pressure on the effective reaction rate, gas–solid mass-transfer rate, and heterogeneous contacting efficiency (HCE, the ratio of the logarithmic ozone removal to the pressure drop across the reactor). For the same mass flow rate, higher-pressure systems (2–3 atm) operate at lower face velocities than atmospheric-pressure systems. These higher system pressures result in increased residence times and reaction rates; therefore, HCE is enhanced. In addition, the HCE for the MFEC was more than twice that of the packed bed or monolith at equivalent system pressures because of the higher gas–solid mass-transfer rates and reduced pressure drops of the MFEC.

We describe occupational allergy to castor bean in workers in a felt manufacturing plant. Twenty-six (37%) of the workers complained they were affected by the felt and were examined by us. Of these, 12 were considered to have occupational allergy. These 12 subjects had raised specific IgE levels to both felt and castor bean extracts. In addition, three subjects without occupational allergy had raised specific IgE. The presence of castor bean allergens in the felt was suggested by the correlation between the RAST scores to the felt and castor bean and confirmed by RAST inhibition experiments. The RAST results correlated well with the results of skin prick tests to felt and castor bean extracts. In addition it was found that atopy did not predispose the workers to castor bean allergy.

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