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Waseda University
Using CFD to Predict and Evaluate Human Body Thermal Comfort

One basic application of Computation Fluid Dynamics (CFD) is to simulate air flow in building spaces. The outputs from CFD can be used to ensure that air flow rate, velocities, and patterns meet environmental standards for human comfort. Taking a step further, CFD has recently been used to predict and evaluate thermal comfort using thermo-regulation models of the human body.

Shin-ichi Tanabe
Professor, Department of Architecture
FASHRAE, Ph.D.
Waseda University

  In these simulations, the air flow in the environment is still calculated as before, but the human body, as a separate thermal system, is coupled to the air flow calculation. This enables calculation of the actual human body temperatures in response to the air flow and environmental thermal conditions, providing a much greater understanding about human comfort. Software Cradle SC/Tetra contains a fully-coupled human body thermo-regulation model. It is used to simulate office environments, car interiors, and air pollution. Shin-ichi Tanabe, Professor, Department of Architecture in the School of Creative Science and Engineering at Waseda University, developed the thermo-regulation model in SC/Tetra. It is called the JOS (Joint System) thermo-regulation model.

  The Department of Architecture at Waseda University, the oldest private college in Japan, consists of six curriculum majors: architectural history, architectural planning, urban planning, environmental engineering, building production, and architectural structure. Prof. Tanabe works within environmental engineering, and his interests focus on evaluating human comfort and health in residential spaces. His research is directed at providing a better environment for both people and the earth by studying heat flow around human bodies in houses, cars, train stations and other public places. Today architects must consider how to achieve a safe and comfortable environment while minimizing energy consumption. To perform his studies, Prof. Tanabe uses SC/Tetra and JOS.
 

A Wide Variety of Studies


  One of the most recent research applications of SC/Tetra and JOS is the simulation of the spread of airborne droplets from coughing. This is a critical research when studying the spread of virus infections such as the flu. As droplets are released by coughing, the liquid in the droplets quickly evaporate, and the nuclei of the droplets waft through the air. The nuclei waft, on average, for approximately 2m (6.5 ft) although their actual range depends on the air flow within the environment. Tuberculosis is an example of disease that spreads through the air. The concentration of the nuclei of tuberculosis, for example, can be considered a pollutant. Prof. Tanabe has used SC/Tetra to study the behavior of airborne droplets and pollutants and to design techniques for dispersing them so they are less harmful. He has used a "coughing manikin" to generate experimental data.


















Figure 1. Development of a model for air flow of coughing with a modeled oral cavity
 

  Prof. Tanabe has also conducted research on a method for sterilizing air by spraying gaseous chlorine dioxide into the air. Chlorine dioxide is effective for neutralizing the flu, anthrax, norovirus, and fungi. However, while chlorine dioxide can be sprayed into the air, its effectiveness decays over time. It must be sprayed continuously to maintain sufficient concentration. With this understanding, Prof. Tanabe and his industry partners have studied methods for injecting a sufficient supply of chlorine dioxide into air by conducting simulations using SC/Tetra.


  Another application of SC/Tetra and JOS has been for studying occupant comfort in vehicle interiors. This work has been done in collaboration with auto manufacturers. Recently, electric car interior comfort simulations have received a significant amount of attention because the electric car interior cannot be warmed by residual heat from the engine as it can with a combustion powered vehicle. This requires more efficient heating and air conditioning. Experiments are being conducted to assess other means of providing thermal comfort to vehicle occupants such as heated and cooled seats. The results of interior comfort studies can have even more impact on those who spend long periods of time in a vehicle such as truck drivers.

Combining the Thermoregulation Model and CFD


  Prior to 2007, Prof. Tanabe's research has been largely experimental, studying both actual people and a dummy of the human body called a "thermal manikin". The "thermal manikin" could simulate the human body skin temperature. However, experimental testing does not offer the flexibility and insight that virtual simulation can, so one day Prof. Tanabe suggested integrating his JOS human body thermo-regulation model into CFD. After the suggestion, Software Cradle responded by making the JOS model available within SC/Tetra. Prof. Tanabe said "The JOS model was made available in SC/Tetra, and the heat fluxes through the skin for each body part could now be calculated in the simulation." This was exactly what Prof. Tanabe wanted. He went on to say "The people at Software Cradle put in a lot of really hard work into the code". Because of the complex geometry of the human body, SC/Tetra was chosen because it uses an unstructured mesh. The JOS model was first made available in SC/Tetra in 2007.

Figure 2. Evaluation of thermal environments in vehicles
Skin temperature with wind and solar radiation.
Simulated using SC/Tetra version 7

CFD versus Experimental Tests

  Prof. Tanabe cited some big advantages for using CFD to acquire insight compared to experiments. There is a large cost associated with hiring examinees for experimental tests. There is also a lot of variation in the results due to the wide range of individual characteristics of the examinees. The large variations require testing large samples, which means hiring more examinees. Additional complexities involve legal considerations. Some of the tests can be for products or systems that are industry secrets. The manufacturers want to expose their new concepts to as few people as possible. Lastly, some experiments require permission from an ethics committee, which can take several months.

  In contrast, CFD opens up the windows of opportunity with very few constraints. Test parameters can be changed. A large number of test conditions can be simulated. The JOS model in SC/Tetra permits users to change gender, age, body size and other characteristics of the human body to assess impact on a wide population. Even the impact on the elderly can be assessed, which would normally not be included in experimental testing because of certain risks.

*All product and service names mentioned are registered trademarks or trademarks of their respective companies.
*Contents and specifications of products are as of January 31, 2013 and subject to change without notice. We shall not be held liable for any errors in figures and pictures, or any typographical errors.

Institute Details


Department of Architecture, Waseda University
Shin-ichi Tanabe Laboratory

Shin-ichi Tanabe
Professor (Doctor of Engineering),
Department of Architecture, Waseda University
Main Research
Architectural Environmental Engineering
History
1999

Launch of Laboratory 

(First established in 1989 at Ochanomizu University)

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