2007, Piran, Slovenia

ESTIMATION OF COOLING EFFECT OF ICE PACKS
BY THERMAL MANIKIN
Satoru Ueno, Shin-ichi Sawada
National Institute of Occupational Safety and Health, Kawasaki, Japan
Contact person: uenos@h.jniosh.go.jp
Manikins
INTRODUCTION
Firefighters are required to work physically and psychologically high load tasks in extreme
conditions, such as hot and hazardous environment. To protect themselves from fire, they
have to wear multi-layered heavy protective clothes, and from hazardous gas, they have to
don self-contained breathing apparatus (SCBA). This protective clothing not only has thermal
insulation properties from body to environment, but also limited water vapor permeability.
Much heat production caused by extreme workload such as life-saving (Heimburg, 2006)
does not dissipate easily due to low heat transfer of thick protective clothing. Moreover
limited water vapor permeability impairs physiological cooling of the body, as evaporation is
the only way to decrease body temperature in high ambient temperature. Consequently, core
temperature rises, accompanied by much fluid loss owing to the high sweat secretion, which
leads to tachycardia and work performance decrements (Ftaiti, 2001). In the U.S., about 40%
of cause of death is from cardiovascular disorders (USFA, 2000). To prevent heat related
disorders, microclimate cooling systems that have mobility are needed to reduce heat strain of
fire-fighters. In earlier studies (Smolander, 2004; Muir, 1999), significant reduction in heat
strain was shown while wearing cooling systems. However, there are few studies comparing
the effectiveness of cooling systems on the heat absorption from human body. In this study,
using a thermal manikin, we measured the cooling power of two kinds of refrigerants, based
on the fusion of paraffin situated inside cooling vest pockets.
METHODS
A thermal manikin (MTNW, Seattle) consisting of 26 zones was used to evaluate the cooling
efficiency of refrigerants in the cooling vest. The cooling vest covered the torso, which was
divided into four zones: shoulder, chest, back, stomach. The power supply to each zone was
adjusted so that the surface temperature of each zone could be controlled at 34 throughout
the experiment. To keep the environmental condition of the manikin constant, we installed the
thermal manikin in a climate chamber (20 , relative humidity 50%). This condition
conformed to ISO15831. Physical characteristics of refrigerants are listed in Table 1. Each of
the refrigerants was inserted into pockets of the vest. The vest had 2 parts: the front with 6
pockets and the back with 10 pockets. We estimated the cooling efficiency of 2 refrigerants.
Table 1. Physical characteristics of refrigerants
Type A Type B
Size 76×122×6mm 68×123×18mm
Constituent paraffin 100% (solid) paraffin 50% water 50% (gel)
Weight (1set = 16 pack) 1.28kg/set 1.44kg/set
Procedures: After dressing the manikin with a T-shirt, long pants of working clothing, and
fire-fighter’s clothing, we set the surface temperature of each zones at 34 . In about 5 h, a
thermal steady state was achieved, and we quickly removed the fire-fighter’s clothing from
the manikin, and added the cooling vest on the T-shirt and replaced the fire-fighter’s clothing
quickly. The cooling vest was attached to the manikin by connecting 2 separate parts firmly at
the stomach and shoulders using tape. The vests with type A refrigerant and type B refrigerant
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