[Vol. 1] How indoor airflow affects human comfort is still not fully understood. Professor Takashi Kurabuchi (Picture 1) has been using SC/Tetra to conduct CFD (Computational Fluid Dynamics) simulations in order to investigate indoor airflow in buildings.
The research at the Kurabuchi Laboratory, in the Department of Architecture, Faculty of Engineering at the Tokyo University of Science, involves architecture and building engineering, architectural equipment, and CFD. CFD simulations are used to study ventilation effects and human comfort. Some examples include investigations on air-conditioning energy efficiency, quanification of human comfort, and bathroom heating. Kurabuchi Laboratory studies both residential living and commercial working environment using CFD and experimental results.
When Professor Kurabuchi first started with CFD, he used his own structured mesh code. However, this meant he was the only one who understood the contents of the code. As the code needed to be modified to solve particular fluid problems, his laboratory students found challenging to customize the code. This encouraged Professor Kurabuchi to consider using commercial codes.
Professor Kurabuchi undertook experiments to see how the heat transfer coefficient on a thermal manikin was altered by temperature changes. His experimental results were different from the temperature patterns identified in other engineering evaluations that used objects with simpler geometries. This was due to the increased physical details of the thermal manikin. Professor Kurabuchi accurately reproduced these details in CFD simulations and obtained results that were within the range of error of the experiments. Because of this, he found he could predict heat transfer (Fig 1). “The analysis accuracy was higher than I thought. It’s far more beneficial to use the CFD tool for investigating some phenomena that cannot be accurately represented in experiments. I think the analysis tool is becoming capable of helping us decide, for example, which (design idea) is better (based on the simulation results),” says Professor Kurabuchi.
Using CFD simulation and experiment results, Professor Kurabuchi progressed to solving engineering design problem. His challenge was to evaluate the differences in the indoor environment when using a wall heating unit compared to floor heating. He assumed the same level of warmth would be felt by human subjects in both cases. He also estimated the amount of energy required.
Fig 2 shows that for both cases, the average heat emission from the thermal manikin is equal, for floor heating and the wall heating unit. However, the room temperature is 3 °C higher when the wall heating unit is used. One of the reasons for this is that the wall is warmer when floor heating is used but the air is cooler. Another reason is that, although the wall heating unit supplies warm air, it feels cooler because of the presence of airflow. Circulating air that is colder than the human body surface temperature creates cooling effects. This is effective in a cooling mode, but not in a heating mode. Since there is no need to increase the air temperature with floor heating, secondary energy consumption can be kept low. Overall, Professor Kurabuchi found that radiative heating methods such as floor heating may be better than convective heating.
Fig 3 shows that values of the radiative heat transfer coefficient using floor heating compared to using a wall heating unit were equally independent of the type of body parts. However, the values of the convective heat transfer coefficient were different depending on the type of heating and type of body parts. The value of the combined heat transfer coefficient was 8 W/(m2•K) with the floor heating, and 10 W/(m2•K) with the wall heating unit. This means about 20 % of the heat is lost when the wall heating units used. In addition, floor heating does not produce a draft, which means that less heat escapes even when the temperature is relatively low. Because of the drafts produced by the wall heating unit, the difference between the human body surface temperature and the room temperature must be kept small. In terms of energy consumption, floor heating required 10 - 20 % less energy than the wall heating unit.
|Establishment of University||1881|
|Establishment of Department||1962|
|Type of University||Private|
This article is also available in pdf.
Using CFD (Computational Fluid Dynamics) to Improve Aerodynamic Performance of Helmets for Sports and Motorcycle Racing Games at the Olympics
Micro-climate Design that Fully Utilizes Wind and Sunlight Becomes Reality by Combining Conventional Solution Approaches with the Latest Computational Technology
CFD Assists in Hygrothermal Control for Preservation of Cultural Artifacts and Overall Energy Savings
Helping Local Companies Solve Thermal Issues with CFD Tools
Contact us from the inquiry form below for any inquiry regarding this article.