The effect of horizontal elements and building orientation on PM_(2.5)concentration in classrooms

This study aimed to evaluate the effect of horizontal elements and building orientation on indoor particulate matter with a diameter of less than 2.5 mm(PM_(2.5))concentration and airflow.We added horizontal elements to the envelope of a standard Thai school building using computational fluid dynamics for testing the dispersion and concentration of PM_(2.5)in classrooms under the PM_(2.5)crisis condition in Chiang Mai Province.The results showed that the building orientation and the addition of horizontal elements to the front wall of the school building had different effects on the concentration of PM_(2.5)and airflow within the classroom in eight directions.Classrooms in standard school buildings facing NE and SW directions had the highest indoor PM_(2.5)concentrations,and those facing NW and SW had the least compared to all directions.Adding horizontal elements on the front wall of the standard school building was found to reduce the PM_(2.5)concentration in the classrooms of the building facing the N,NE,E,and SE directions.Increasing the horizontal element width from 1 m to 2 m reduced the PM_(2.5)concentration in classrooms of the N-and SE-facing buildings but had little effect in the classrooms of the NE-and E-facing buildings.This study will provide insight into the optimization of air quality in school buildings,informing the decision-making for adding horizontal elements and controlling their widths.

Mathematical Modelling for Assessing Integrity of Power Systems Grounding Devices

This paper presents the development of a new technique to monitor the operating conditions of a grounding device of high voltage apparatus and systems without any diggings and forced outages. The model is based on the evaluation of the magnetic field distribution along the current-carrying horizontal element when it has been deteriorated or broken. A mathematical model which can be used to analyze and evaluate the integrity of the grounding device has been developed. Computer simulation studies were conducted to validate the effectiveness of the proposed model.

Study on the Rotor Design Method for a Small Propeller-Type Wind Turbine

Small propeller-type wind turbines have a low Reynolds number,limiting the number of usable airfoil materials.Thus,their design method is not sufBciently established,and their performance is often low.The ultimate goal of this research is to establish high-performance design guidelines and design methods for small propeller-type wind turbines.To that end,we designed two rotors:Rotor A,based on the rotor optimum design method from the blade element momentum theory,and Rotor B,in which the chord length of the tip is extended and the chord length distribution is linearized.We examined performance characteristics and flow fields of the two rotors through wind tunnel experiments and numerical analysis.Our results revealed that the maximum output tip speed ratio of Rotor B shifted lower than that of Rotor A,but the maximum output coefficient increased by approximately 38.7%.Rotors A and B experienced a large-scale separation on the hub side,which extended to the mean in Rotor A.This difference in separation had an impact on the significant decrease in Rotor A's output compared to the design value and the increase in Rotor B's output compared to Rotor A.