Ventilation is of primary importance for the creation of healthy and comfortable indoor environments and it has a significant impact on the building energy heating and cooling demand. The aim of this study is to assess the application of time-periodic supply velocities to enhance mixing in mixing ventilation cases to reduce heating and cooling energy demands. This paper presents computational fluid dynamics (CFD) simulations of a generic mixing ventilation case, in which the time-averaged velocities and pollutant concentrations from a reference case with constant supply velocities were compared with those obtained from a case with time-periodic supply velocities (sine function). The unsteady Reynolds-averaged Navier-Stokes (URANS) CFD simulations indicate that the use of time-periodic supply velocities can reduce high pollutant concentrations in stagnant regions, reduces the overall time-averaged pollutant concentrations and increases contaminant removal effectiveness with about 20%. The influence of the period of the sine function was assessed and the results showed that for the periods tested, the differences are negligible. Finally, the URANS approach was compared with the large eddy simulations (LES) approach, indicating that URANS leads to very similar results (NMSE < 3.2%) as LES and can thus be regarded as a suitable approach for this study.
University staff and students typically spend most of their time indoors. This paper evaluates the thermal environment of an air-conditioned scientific laboratory in a tertiary educational institution in Malaysia using Computational Fluid Dynamics (CFD). This computational technique has been used in analysing the indoor environments and has been found to be useful in aiding facilities management. A pilot survey was conducted to collect the required information such as indoor parameters and boundary conditions for the setting up of a CFD model of the laboratory. The model was then simulated based on the data obtained from field observations. Results indicate that the laboratory users sitting at different rows and work desks would experience different thermal sensations. The mean air temperature was below the recommended comfort zone specified in the local energy standard, but the air velocities were generally within the acceptable range. Based on the calculated predicted mean vote (PMV) and predicted percentage dissatisfied (PPD) indices, most of the users would be thermally uncomfortable, and a warmer environment was preferred. Recommendations were made to regulate the inlet air temperature of the laboratory to improve thermal comfort of laboratory users and for energy saving purposes.
In Vietnam, the operating room (OR) is used with max productivity. So, how to maintain comfort environment level, which is one of the assignments in designing and installing the operating room. In this study, the OR model is designed based on ASHRAE 170 – 2013 standard [1], and dimensions are referred to as “Comparison of Operating Room Ventilation System in the Protection of the Surgical Site” [2]. ANSYS CFX is used for calculating and simulating velocity and temperature of surveyed air points inside the room by many cases. A face temperature between 20,3 and 20,6 °C and a velocity of around 0,15 to 0,18 m/s is provided from the same laminar diffuser array. From the results, the OR comfort level is reviewed through the ADPI index.
Mixing ventilation driven by two oppositely located supply jets with a time-periodic supply velocity: A numerical analysis using computational fluid dynamics