Practical insights on Thermal Manikin Evaporative Resistance Test ASTM F2370

For evaluating thermal comfort in an indoor environment, a thermal manikin is a very dependable instrument. ASTM F2370 is a test method for determining cloth insulation against heat when worn in everyday use styles while the wearer is standing or walking. This article will tell you further how this test can be conducted in a textile lab.

Evaporative Resistance and thermal manikin

It is the property of a material to resist heat transfer and moisture through evaporation. It has an essential role in heat stress models, which predict human body behaviour in different climatic regions. For this purpose, heat stress models evolved as thermal manikins. A thermal manikin is an artificially human-shaped model used for measuring heat transfer rates through different parts of the body. The manikin uses these rates to determine the distribution of skin and interior temperatures.

Summary of ASTM F2370

The manikin is equipped with the test ensemble’s components in the same order as it would be in everyday use. The manikin is sized and shaped like an adult human body. It is internally heated to a skin surface temperature that is uniform in the manikin body. It has movable arms and legs for measuring thermal insulation of ensemble clothing. The manikin is kept in a climate chamber with adjustable air humidity, defined air temperature, and airspeed.

Thermal Manikin

The physiological thermal manikin model receives the heat flux from each zone.   It is positioned within the range of three ambient temperature sensors, three ambient humidity sensors, and two ambient wind speed sensors. These sensors are positioned 0.5 meters distant from the manikin. The shaft can be rotated to remove the sensor before positioning the dressing and dummy. The precision of the humidity sensor should be greater than 5%, and the temperature sensor has an accuracy of 0.2°C. The wind speed sensor also has an accuracy of better than 0.05 m/s.

There are three positions for the manikin body: Dynamic walking, Flat laying, and Static standing. Static standing and Dynamic walking positions are used to test clothing, and the Flat laying position is primarily used to assess the heat resistance of the quilt and sleeping bag. The motion control system uses an external connection mode, making it easy to choose between testing in dynamic and static states. A servo motor drive motion mechanism and high-strength aircraft aluminium profile are used throughout the frame to configure and control the amplitude and movement of models precisely.

Uses of Manikin Measurement Technology

In the fields of clothing ergonomics research, clothing science bionics and biophysics, it is acknowledged as a vital component of measuring heat transfer, including conduction, convection, radiation and evaporation. While wearing professional protective uniforms that prevent sweat from evaporating, human bodies cannot cool themselves, leading to uncomfortably and even health problems. It is extensively used in apparel, aerospace, fire safety, petroleum, traffic safety, occupational health, and other areas for assessing the integral heat resistance and moisture resistance performance of clothing using the best available technology.

Similar Standards to ASTM F2370

The following test methods are also used for measuring the thermal resistance properties of garments.

1. GB/T 18398 – Testing method for clothing thermal resistance
2. GB/T 11048 – Warmth retention property of textiles
3. ISO 15831 – Measurement of thermal insulation by means of thermal manikin
4. ASTM F1291 – For Measuring the Thermal Insulation of clothing using a heated Manikin
5. ASTM F1720 – Standard for Standard Test Method for measuring thermal Insulation of sleeping bags using a heated Manikin

ASTM D2370 Test Method Procedure

Apparatus

1. Sweat Generation and Sweat area – All of manikin’s surface should have sweat producing abilities to portray actual human. It should have a water-fed capillary network throughout its whole surface.
2. Temperature – The manikin’s skin should have an average temperature of 34.5-35.5°C. the temperature should be maintained throughout the body.
3. Testing Chamber – Testing must be done in uniform conditions. Place the manikin in a room having dimensions 1.5 x 1.5 x 2.5 meters.

Sample Preparation

1. Take three identical garments to test. If identical garments are not available, proceed to test with only one garment.
2. Take the garment size according to manikin. Garments should have an appropriate fit to manikin as required in end use. If end use are tight or loosely fit garments, they should be tested on manikin accordingly.
3. Garments should be conditioned for 12 hrs prior to testing.

Test Procedure of ASTM F2370

1. Take test garments according to thermal manikin size.
2. Set the skin temperature of thermal manikin body dummy at 32-35℃.
3. Set the manikin’s experimental status. i.e. static or dynamic, and set the step length and step speed.
4. Set the climate chamber temperature according to the estimated thermal resistance value of the clothing to be tested. When naked, the temperature should not be less than 10℃ below the skin temperature. When the thermal resistance value is between 1 and 3, it should not be less than 20℃ below the skin temperature. When the temperature is greater than 3, it should not be less than 30℃ below the skin temperature.
5. Adjust the humidity of the climate chamber to 30-50%.
6. Regulate the wind speed of the climate chamber at 0.15-8 m/s.
7. Take note of the climate chamber environment’s values, ensuring the change of the ambient temperature in the climate chamber is not more than 1℃, the change of the relative humidity is not more than 5%, and the change of the wind speed is not more than 50%. For 30 to 60 minutes, keep the environmental value consistent.
8. After the warm manikin enters the dynamic heat balance, the skin temperature ambient temperature and the heating power shall be measured every minute, and this state shall be maintained for more than 10 minutes.
9. Start the test by dressing the manikin in the test clothes. The warm manikin needs to be retained for more than 20 minutes when it enters the dynamic thermal balance once more.
10. The thermal resistance test is completed, and the test data can be studied.

Conclusion

Thermal manikins assess skin temperature and heat loss with great accuracy. They also replicate different environmental temperatures to analyze human behaviour precisely. Clothing values in different zones and detailed thermal sensation measures are possible with this invention. These findings are helpful in understanding body groups and body zones of different human natures.

Experience & Insights

• If possible, choose fitted clothes according to end use to reduce measurement uncertainty because loose clothing tends to shift shape as the posture of the manikin is changed.

FAQs

1. How do thermal manikins work?

Thermal manikin measures the difference in heat loss in a controlled environment and sends the data of all sectors to the physical model. The physiological model reads skin temperature, respiration rate, and sweat rate in all sections. It then sends these values to the manikin, forecasting how the human body would react in a particular environment.

2. For how long, thermal manikins are used?

Dr. Harwood Belding is credited for developing the first operational thermal manikin for the United States military in 1941. The testing involved utilizing human volunteers to test protective clothes and equipment.

Related Resources

EN 342 ASTM F2370 Sweat Thermal Manikin System DR606-34T

Fire-Retardant Clothing Research in Combustion Laboratories

Walk-in Climate Room DR048-16