Building Energy & Environment Laboratory
Let the dream set sail

2018

Lai, D., Chen, C., Liu, W., Shi, Y., Chen, C.* (2018). An ordered probability model for predicting outdoor thermal comfort. Energy and Buildings, 168, 261-271.


Outdoor thermal comfort in urban spaces is gaining increasing research attention because it is associated with the quality of life in cities. This paper presents an ordered probability model for predicting the probability distribution of thermal sensation votes (TSVs) based on 1549 observations obtained from a large-scale field survey conducted at a park in Tianjin, China. With a given set of inputs, the developed model can predict the probability that people will feel cold, cool, slightly cool, neutral, slightly warm, warm, or hot. The predictive capability of the ordered probability model was systematically assessed by comparing it with the survey data and a traditional multivariate linear model. Both models had a similar accuracy in predicting single-value TSVs. However, the ordered probability model performed much better than the multivariate linear model in predicting the probability distribution of TSVs. A sensitivity analysis of the ordered probability model revealed that outdoor air temperature was the most important influencing factor. The impacts of global radiation, relative humidity, and activity level on predicted thermal sensation depended on the outdoor air temperature. The developed ordered probability model was used to predict suitable time periods for holding outdoor activities in Tianjin across a whole year. This new model is a more informative tool for predicting outdoor thermal comfort. 


Xia, T., Bian, Y., Zhang, L., Chen, C.* (2018). Relationship between pressure drop and face velocity for electrospun nanofiber filters. Energy and Buildings, 158, 987-999.


Nanofiber filters are typically fabricated using the electrospinning technique, which can reach high particle removal efficiency with relatively low air resistance because of the gas slip effect. They have a great potential for applications in the filtration units of heating, ventilation, and air-conditioning (HVAC) systems to reduce the fan energy consumption. This study systematically examined the relationship between pressure drop and face velocity for electrospun nanofiber filters. Experimental data of 122 nanofiber filters were collected from the literature to validate the theory regarding pressure drop for nanofiber filters proposed in previous studies. The linear regressions between pressure drop and face velocity showed that 89% of the tested nanofiber filters had an R2 value greater than 0.9. Therefore, the pressure drop can be confidently regarded as being proportional to the face velocity for nanofiber filters. This conclusion was further confirmed by additional experimental measurements conducted in this study. After confirming the theory, the air resistance coefficients of nanofiber filters were calculated and compared with that of commercial HVAC filters. The comparison showed that the air resistances of nanofiber filters with careful design could be lower than that of the commercial filters with similar particle removal efficiency. 


2016

Chen, C., Zhang, X., Groll, E., McKibben, A., Long, N., Dexter, M., Chen, Q. (2016). A method of assessing the energy cost saving from using an effective door closer. Energy and Buildings, 118, 329-338.


Door closers are widely used for doors in commercial buildings, not only for safety purposes but also for reducing the airflow through door openings. This study aimed to develop a method for quickly assessing, in the design phase, the heating and cooling energy cost saving from using an effective door closer. The method developed in this study consists of a stop angle model, airflow model, and energy cost calculation. This investigation also conducted experimental measurements in a full-scale test facility to validate the models. This study then used the proposed method to assess the heating and cooling energy cost saving from using an effective door closer in the cities of Minneapolis, Boston, San Francisco, and Phoenix. It was found that, under a greater indoor-outdoor pressure differential, using an effective door closer would save more energy cost. When using a closer with a larger size, the energy cost lost would decrease, but a large closing torque may significantly reduce ease of use and accessibility and potentially violate building codes related to the Americans with Disabilities Act (ADA). Furthermore, the energy cost saving from using an effective door closer in San Francisco would be lower than that in Minneapolis, Boston, and Phoenix.