Yuanwei Lu

Synergistic Effect of Nanophotocatalysis and Nonthermal Plasma on the Removal of Indoor HCHO

Photocatalysis is an effective method of air purification at the condition of a higher pollutant concentration. However, its wide application in indoor air cleaning is limited due to the low level of indoor air contaminants. Immobilizing the nanosized TiO2 particles on the surface of activated carbon filter (TiO2/AC film) could increase the photocatalytic reaction rate as a local high pollutant concentration can be formed on the surface of TiO2 by the adsorption of AC. However, the pollutant removal still decreased quickly with the increase in flow velocity, which results in a decrease in air treatment capacity. In order to improve the air treatment capacity by the photocatalytic oxidation (PCO) method, this paper used formaldehyde (HCHO) as a contaminant to study the effect of combination of PCO with nonthermal plasma technology (NTP) on the removal of HCHO. The experimental results show that HCHO removal is more effective with line-to-plate electrode discharge reactor; the HCHO removal and the reaction rate can be enhanced and the amount of air that needs to be cleaned can be improved. Meanwhile, the results show that there is the synergistic effect on the indoor air purification by the combination of PCO with NTP.

The Manufacture and Performance Test of a Mini-Type Single Screw Compressor

With the development of very large scale integration, the chip heat dissipation is a problem that needs to be solved urgently. Vapor compression refrigeration system is a valid method to cool the electric chip. However, a particular challenge is to make a small and efficient gas compressor. In this paper, a mini-type single screw compressor was manufactured in Beijing University of Technology and a corresponding performance test system was set up. Experimental results show that the heat created by the single screw compressor is higher, which led to an extreme high exhaust temperature. An effective solution is to introduce the low temperature refrigerant from the condenser to the compressor directly to cool down the compressor. Based on this procedure, the compressor performance was measured experimentally. It was found that the condensing temperature, compressor rotation speed and refrigerant charge can affect the compressor performance noticeably and every affective factor has an optimal value. According to the optimal results, the compressor refrigerating capacity of 2.03 kW and system coefficient of performance (COP) of 2.24 was achieved at the evaporating temperature of 5 °C and condensing temperature of 32 °C. Those results can be a baseline for the further performance enhancement of the single screw compressor and can be a valid method for the cooling of large scale integration.© 2012 ASME

The Study of Photocatalytic Degradation of Formaldehyde Under the Action of Mass Transfer

Photocatalysis is an emerging and promising technology for indoor air purification, which has the higher reaction rate at the higher pollutant concentration and vice versa, and the toxic intermediate products were produced meantime. However, the concentration of indoor pollutant is usually very low. So how to improve the photocatalytic reaction rates in indoor contaminant levels in building and to eliminate the intermediate toxic products are the keys of commercialization of this technology. This paper immobilized the TiO2 on the active carbon and analyzed the effect of mass transfer due to the absorption of AC on the photocatalytic reaction rate. The experimental results shown that the photocatalytic reaction rate was improved for the local concentration of contaminants on the surface photocatalyst TiO2 was enhanced by adsorbent activated carbon. With the increase of air stream velocity, the photocatalytic reaction switched from mass transfer control process to photocatalytic reaction control process. The switch point was advanced for the absorption of AC comparing with TiO2 immobilized on the surface of glass. The indoor formaldehyde with low level concentration can be decomposed to the range of indoor air quality standards by the TiO2 /AC filter.Copyright