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National Research Institute for Cultural Properties, Tokyo
CFD Assists in Hygrothermal Control for Preservation of
Cultural Artifacts and Overall Energy Savings

The National Research Institute for Cultural Properties, Tokyo introduced CFD (Computational Fluid Dynamics) analyses in 2005, for understanding temperature and humidity conditions surrounding cultural artifacts and assets and improving environmental managements. Thermal fluid analyses have now become crucial for the design and management of energy-efficient preservation environments.

Fig 5: Overview of temple interior space.
Click to enlarge.
The orange wall area shows the space allocated as votive tablet painting hall. The area surrounded by the light green and purple walls is the main hall.
1: Wind inlet, 2: Wind outlet (a gap inserted at the top)
X to the East, Y to the North, uphill outside the East and North ends.

 

Fig 6: Analysis results of temple interior space.
​Click to enlarge.
Representing the situation where wind inlet, outlet, and the window located at 3 are all open.

Simulation of Cultural Artifacts and Assets Owned by Temples

In Japan, many cultural artifacts and assets are owned by local temples. This can make preservation difficult. An example is a temple located by a coast, which Dr. Inuzuka also researched. The temple owned wooden votive tablet paintings subject to humidity levels exceeding 90% in some seasons.

   

A hall dedicated to displaying the tablet paintings is built around the main hall. This hall is often kept shut. Air-conditioning was not available because of difficulties providing power to the hall and the humidity could be very high. To lower humidity, Dr. Inuzuka used scSTREAM to evaluate ways to improve ventilation.

   

Dr. Inuzuka investigated the wind direction and air velocity around the hall. He suggested installing vent holes around the hall which would permit air to enter and leave the hall (Fig 5). Calculations were made assuming that the wind blew due east at 0.5m/s. Dr. Inuzuka simulated the airflow inside the hall, when using a (1)air inlet, (2)air outlet, and (3)slit gap. From the results (Fig 6), Dr. Inuzuka confirmed the ventilation efffects created by the slit gap and a vent hole for the air outlet.

 

Another example of applying scSTREAM was for the design of a repository in Tokyo. Dr. Inuzuka wanted to know whether the air could be designed to flow across the entire space by effectively locating the air-conditioner and shelves. He used the results to plan the layout, and conducted experiments to confirm the results. He measured the air velocity at various locations and confirmed that the airflow behaved as predicted.

Using Different Analysis Tools for Different Purposes

In addition to using scSTREAM, Dr. Inuzuka also uses NETS, a heat and air transfer system simulation program developed by Shimizu Corporation. NETS accounts for walls and other components and calculates the temperature and humidity of the internal space as a function of outside weather conditions. This is used to evaluate how the internal environment changes throughout the year. NETS makes it possible to quickly identify seasonal effects. On the other hand, it is not easy to calculate spatial distribution by using NETS.

 

Dr. Inuzuka uses scSTREAM to calculate spatial distributions for temperature and humidity. Of the several thermal/fluid software he considered, one of the primary reasons Dr. Inuzuka chose scSTREAM was because of its reliable technical support.

 

Going forward, Dr. Inuzuka is eager to pursue more accurate humidity calculations. “Understanding the humidity conditions surrounding cultural artifacts and assets is far more important than temperature. When we were working on the showcase for the Mie Prefectural Museum, we asked Cradle to conduct the analyses because modeling the humidity conditioner was difficult. We hope to be able to represent the mechanism of moisture absorption and desorption in future,” says Dr. Inuzuka. He points out that materials such as paper, soil, wood, and stones could also act as humidity conditioners. Dr. Inuzuka suggests that the scope of CFD analyses can be further expanded if he can precisely predict the degree of moisture absorption and desorption of cultural assets such as a stone or wooden statue.

 

Challenging Analyses of Semi Outdoor Environment

Another topic Dr. Inuzuka is interested in studying is simulation of a semi outdoor environment that surrounds cultural artifacts and assets. Dr. Inuzuka is currently working on a decorated ancient Japanese tomb in Fukuoka, Japan. Tombs are abundant in Fukuoka and Kumamoto prefectures. They can be directly exposed to the outdoors, buried in the ground, or preserved inside a preservation facility. Dr. Inuzuka hopes to simulate the environment for the tombs inside preservation facilities.

 

Another challenge is to preserve cultural artifacts and assets from being damaged by natural hazards. A significant number of important cultural artifacts and assets were ravaged by the earthquake and tsunami disaster in 2011. Though some of them were rescued, a problem arose as to where these dirt covered assets should be stored. Some were temporarily transferred to closed schools and later moved to better maintained environments but others were left untouched. Some were delivered to specialized facilities and stored in repositories with double layer walls. Dr. Inuzuka says that simulation will make it easier to identify the ideal storage environments.

 

Dr. Inuzuka explains that researchers in this field around the world are currently evaluating the way air-conditioning should be used and other means for maintaining preservation environments. Although air-conditioner capabilities have largely improved, cost correlates with the amount of energy used. Switching to simpler forms of air-conditioning could consume less energy and lower costs. The challenge is to ensure that the integrity of the cultural artifacts and assets is maintained. Dr. Inuzuka suggests that this issue can be resolved by performing assessments using CFD tools. He expects simulation will a play significant role in the future.

​​*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, 2015 and subject to change without notice. We shall not be held liable for any errors in figures and pictures, or any typographical errors in this brochure.

Institute Details




 

National Research Institute for Cultural Properties, Tokyo
Founded 1930
Activity Research and preservation of cultural properties
Representative Nobuo Kamei, Director General
Head Office Chiyoda-ku, Tokyo, Japan
URL http://www.tobunken.go.jp/index_e.html

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