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Lion Corporation
Quickly Drying Wet Laundry indoors by Hanging Clothes in an Arch on Square Hangers: Effective Ventilation for Drying Wet Clothes Indoors (Published on Lidea)

[Vol.1] Using many different media, the Lion Corporation delivers useful tips and advice about how to effectively use everyday household and health care products for better living. scSTREAM is used for fluid analyses to improve the reliability and quality of the information communicated. Using scSTREAM capabilities to animate the results has made their recommendations more convincing.

Managing a Website to Provide Tips for Better Living

The Lion Corporation manufactures and sells toothpastes, toothbrushes, hair and skin care products, pharmaceutical products, cooking related products, and other household related products. Established in 1891, they celebrated their 125th anniversary in 2016. The Lion Corporation develops a wide range of products used for everyday living, which are incredibly popular among consumers in Japan.

The effectiveness of household products can be maximized when appropriate amounts are used in the most efficient ways. One example is washing clothes. Dirt will not be removed effectively if the proportion of laundry detergent, amount of clothes, and water are not appropriate. In addition to conventional sales methods, the Lion Corporation also provides customers with ways to use their products more efficiently, as well as advice on everyday household tasks. Lidea ( launched in 2014, to offer useful articles designed to help solve customer everyday home-related problems and suggest improvements.

Picture 1: Mr. Yoshifumi Yamagata (D.Eng)
Lion Corporation
Washing Specialist (Meister)
Textiles Evaluation Specialist

Lidea publishes articles written by 5 specialists (known as Meisters), which are categorized into cleaning, oral care, health care, and washing topics. Research is conducted at the company's living comfort laboratory and the findings are used to update the articles. Each specialist offers advice based on their expertise. Dr. Yoshifumi Yamagata, Washing and Textiles Evaluation Specialist from Lion Corporation, (Picture 1) is one of them.

Picture 2: Top HYGIA, a small, super-concentrated anti-microbial liquid laundry detergent

Most Effective Drying Layout of Laundry Validated by Research Data

A recent article on Lidea suggests the most effective way to hang wet laundry indoors is in an arch using square hangers. When the weather is not suited to hanging wet laundry outside, clothes are often dried indoors. When drying clothes indoors, a discomforting odor can be generated from insufficiently dried clothes. The odor is caused by bacteria growing in dirt that was not removed from the fabric during washing. As a solution, the Lion Corporation developed several small super-concentrated laundry detergents. This includes a bactericidal laundry detergent called Heyaboshi (Hang-to-Dry Indoors) TOP, which is designed to eliminate existing bacteria. A second product is an antibacterial washing powder Top HYGIA, which is designed to prevent bacteria from growing in the fabric. Top HYGIA was chosen as the Nikkei hit product rankings bestselling product of the year in 2012.

Even if the detergent is antibacterial or bactericidal, Dr. Yamagata stresses the need “to use the detergent properly and to dry the laundry sufficiently to maximize these effects.” Test*1 results show that the wet smell is generated when wet laundry is not completely dried for five hours after being washed. This means that wet laundry must be dried within five hours. Although evaluations have been undertaken to validate the most effective layout for drying wet laundry, Dr. Yamagata reveals that the data was not yet fully conclusive. They conducted tests to determine the effectiveness of three drying layouts using square hangers. They were: 1) arch layout, 2) in-turn layout, and 3) V-shape layout. The arch layout hangs wet laundry in an arch pattern, with long laundry hung at both ends and short laundry in the middle. The in-turn layout alternates long and short laundry. The V-shape layout hangs short laundry at both ends and long laundry in the middle. The tests were undertaken indoors at 25°C and 65% relative humidity. The time required to dry the wet laundry using the arch layout was 4 hours. It took 4.5 hours to dry the laundry using the V-shape layout. Drying time was even longer for the in-turn layout. This suggested that hanging laundry using an arch layout is the most effective among the tested layouts*2.

Figure 1: Velocity distribution when wet laundry is hanged in an arch.
Transient analyses were performed using linear low-Reynolds number model.
Click to enlarge.


Figure 2: Analysis results of arch layout (left), V-shape layout (center), and in-turn layout (right).
Click to enlarge.

Unexpected Findings from Simulation Results

Test results suggested that hanging wet laundry in an arch is the most effective among the tested drying layouts, but the explanation for why was unknown. Dr. Yamagata assumed the drying process involved updraft caused by stack effects. A block of air with a temperature higher than the surroundings rises upward due to its lower density. This is the same mechanism used when air in a chimney rises. Updraft from the collected vapor is created below the wet laundry when the wet laundry is hung in an arch. The updraft moves upward due to the lower density, which helps dry the wet laundry faster.


Dr. Yamagata had been searching to find an alternative means to validate why the arch layout appeared to be the most effective drying layout, other than undertaking more tests. This is when he came up with the idea of using simulations. Software Cradle was recommended by university researchers investigating airflow in indoor living spaces. Dr. Yamagata decided to consult Software Cradle for further help.


Having received a request from Dr. Yamagata, Software Cradle performed computational analyses using scSTREAM, and compared the analysis results with the test findings. As shown in Figure 1, the analysis results show that the drying process involves downdraft, and not updraft. The heat of vaporization created by vapor from the wet laundry cools the surrounding air. The cooled air is collected below the arched laundry, which creates downdraft (results shown in Figure 2).



​*1 Satoshi Matsunaga: Nichijo seikatsu ni okeru sentaku iryo no heyaboshishu to sono yokusei, Journal of Japan Association on Odor Environment, Vol. 36 (2005) No. 2
*2 Presented at the Japan Research Association for Textile End-Uses in 2013

*All product and service names mentioned are registered trademarks or trademarks of their respective companies.
*Contents and specifications of products are as of June 30, 2016 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.

Company Details


Lion Corporation
Business Founded 1891
Lion Corporation Established 1918
Head Office Sumida-ku, Tokyo, Japan
Representative Itsuo Hama (President)
Number of Employees 6,816 (consolidated) [as of December 31, 2015]
Businesses The manufacture and sale of toothpastes, toothbrushes, soaps, cleansers, hair- and skin-care products, cooking-related products, and pharmaceuticals. Exports to overseas affiliates.



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