CFD simulation

Building ventilation demand increased during the “new normal” following the Covid-19 pandemic. Rather than completely renovating existing HVAC equipment, it is more practical and cost-effective to maximize their existing ventilation performance. This study focuses on slot line diffusers, which are widely used for handling perimeter heat loads. Its long throw distance and wide coverage effectively block cold drafts and heat flow from the exterior window glass.

In recent years, especially, the climate change (CC) and urban heat island (UHI) effects are becoming serious problems, affecting people’s life and health, especially in hot summer. For large cities such as Tokyo or Osaka in Japan, the UHI effect is particularly intense. It is known that about 40% of urban anthropogenic heat comes from buildings in large cities. To reduce the anthropogenic heat from buildings is an important countermeasure to this problem.  

There has been an increase in diseases caused by airborne infections such as influenza A/H1N1 or SARS in the recent years. Airborne infection isolation rooms are commonly used to limit the spread of airborne infections. The challenge today is that there is only a limited number of airborne infection isolation rooms in each hospital (class P4). The rooms are expensive to build and airflow control to avoid contamination is often complicated.

The effects of vent configuration and span number on the microclimate in multi-span greenhouses were investigated. A three-dimensional (3-D) computational fluid dynamics (CFD) model was constructed based on an 11-span plastic greenhouse cultivated with 0.2 m-high lettuces. The model was verified with the temperature profile measured in the greenhouse. Then, it was used to explore the effects of vent configuration and span number on greenhouse climate. Simulations show that different vent configurations result in very different microclimate fields.

The knowledge of the local loss coefficients is important for the accurate calculation of ventilation duct pressure loss. In practice, the pressure loss of ventilation duct is very often forecasted, what causes the wrong design of the ventilating fan. A large number of local loss coefficients exist, but the published data are different. The local loss coefficient can be estimated experimentally by the measurement on the real model, or with using of numerical simulation.

The objective of this study is to investigate the possible transmission mechanism of inter-flat air cross-contamination under the condition of singlesided natural ventilation. In high-rise residential building with flush windows on the same side, the air pollutants can diffuse from lower flat to adjacent upper flat in the vertical direction related to the interflat air flow through open windows caused by the temperature difference between the indoor air and the air outside of the windows.

This study assesses the extent of the cooling effects of waterways on the thermal environment of urban districts of Osaka by measurement and simulation. The thermal environments of districts with and without waterways were measured in summer. The effects of the change of configuration of the district near waterway were calculated using computer fluid dynamics simulation. Results show the following. 1) Measured daily mean air temperatures were 0.5–0.8 K lower and SET* was 1.4–2.9 K lower in the district with the waterway than those in the district without waterways in peak summer.

Variable Refrigerant Volume(VRV) air-conditioning system is more liable to meet thermal environment problem than other systems such as split-type air-or window-type air-conditioner because its capacity of outdoor unit is much higher. When used in high-rise building, hot air dissipated by the outdoor units will induce buoyant airflow and increase the working temperature of units at high floor when these heat can not be dispersed in time. High working temperature could not only degrade the total efficiency, but also cause stoppage of the system.

According to the cold climate in winter, a new novel ventilation system was put forward based on the analysis of the heat distribution at the subway station in Harbin. There was no special heating system in winter for subway station with such a ventilation system. In this paper, three dimensional model of the subway station was built, a mathematical model of the novel ventilation system was developed based on the k-ε standard turbulence model, and computational fluid dynamics (CFD) simulations for the ventilation system were performed to clarify the conditions of the temperature fields.

The materials that are used in outdoor spaces are of prime importance as they modulate the air temperature of the lowest layers of the urban canopy layer, they are central to the energy balance of the surface and they form the energy exchanges that affect the comfort conditions of city people. Paved surfaces contribute to sunlight’s heating of the air near the surface. Their ability to absorb, store and emit radiant energy has a substantial affect on urban microclimate.