Abstract：

Using a radial active air jet ejected from the slot surrounding a circular exhaust hood opening can increase the air speed generated by the hood as well as achieve a larger capacity to exhaust pollutants. Critical parameters of the Aaberg hood have been identified to ensure the positive effect of the active jet. This paper proposed a novel type of enhanced exhaust hood using the rectangular opening in place of the circular one in Aaberg hood to meet the needs of different shape and size of exhaust hood. To understand the performance of this kind of exhaust hood and to determine the critical velocity of the active air jet, the flow characteristics and the centerline velocity are investigated by changing the exhaust rate, hood size, jet angle, jet velocity and jet slot width via experimental and numerical methods. Results show that the critical jet velocity exists between two working modes of the novel exhaust hood, one is the ineffective mode with the short-circuit jet, and the other is jet-enhanced mode with the developed radial jet. The near-wall circulation along the hood opening perimeter is not attributed to the existence of the jet. The suggested equation which error is proven to be within 12.5% for the critical velocity presented in this paper is simple in structure, and will help to facilitate the choice of the energy-efficient exhaust hood design in residential and industrial buildings to save energy that would be wasted on increasing the exhaust rate.

Abstract：

Modern automation systems play an important role in improving building energy efficiency. However, some evidence shows that occupants are often dissatisfied with automation systems and may intervene, e.g., by manually adjusting automated shading or air conditioning. Therefore, the concept of occupant-centric buildings has been proposed by some scholars to solve the abovementioned problem. As the basis for realizing occupant-centric buildings, personalized occupant behavior should be identified dynamically. Thus, this study proposes a systematic procedure for establishing a personalized occupant behavior model with cost sensitivity analysis (POBM–CSA). The CSA can improve the identification performance of the model while considering the personalized preferences and attitudes of target occupants. By taking shading behavior identification as an example, the total cost and area under the cost curve were used to evaluate this consideration. The results showed that the POBM–random forest with cost-sensitive classification has the best cost sensitivity performance. By establishing a customer rule library, personalized behavior patterns with reduced misclassifications can be output by the POBM–CSA to improve the operation of occupant-centric buildings.

Abstract：

In this work, the use of waste dust filter of secondary aluminum industry (DFA) to obtain geopolymer foams has been studied. The waste was used as source of alumina and foaming agent. As precursor and principal reactive silica supplier rice husk ash was used. Precursors were chemically activated by means of a sodium hydroxide aqueous solution and a commercial sodium silicate solution. The influence of the DFA content or Si/Al molar ratio (4–7) were determined by keeping the Si/Na molar ratio of 0.7 M constant and the concentration of sodium hydroxide in the activating solution equal to 8.5 M. The geopolymer foams obtained were studied by X-ray Diffraction (XRD), adsorption/desorption of nitrogen, infrared spectroscopy (FTIR), and scanning electron microscope (SEM) techniques. The results indicated that geopolymer foams presented low values of bulk density (643–737 kg/m3) high values of apparent porosity (62–70%), low, but sufficient values of compressive strength (0.5–1.7 MPa) and good values of thermal conductivity (0.131–0.157 W/mK). Lower values of thermal conductivity were obtained for Si/Al = 4 and 5 M ratios, due to the highest apparent porosity and the highest total pore volume. These geopolymer foam materials have similar properties to other construction materials sector such as gypsum boards, foamed concrete, or insulating materials. In addition, its use in other applications of interest such as catalyst support or gas filtration materials could be investigated.