Modeling the efficiency and heat gain of a phase change material cooling vest: The effect of ambient temperature and outer isolation

Abstract

Cooling garments containing phase change materials are one of the practical techniques used for improving thermal comfort and worker's performance in hot environments and under protective clothing. Such garments absorb the body's excessive heat and help the body reach thermal comfort situation by reducing the heat content of the body. The amount of heat absorbed by the phase change materials and the efficiency of the cooling garment can be affected by several parameters. This study uses a software modeling to investigate the effect of different factors such as ambient temperature, the use of protective clothing over the cooling garment, and the type of phase change material bags coating on the efficiency of the cooling garment. The results showed that temperature of the environment in which the cooling garment is used could largely affect the cooling efficiency of such garments. Increasing the ambient temperature from 30 to 40 C can reduce the cooling efficiency of the garment up to 70%. Also, the use of cooling garment under protective clothing was simulated in this paper as a practical way to improve the thermal situation of the body. It was also shown that insulating the outer surfaces of phase change material bags against the surrounding environment could enhance the cooling power of the garment by 20 to 34% depending on the type of the coverings.

Analytical Model for Thermoregulation of the Human Body in Contact with a Phase Change Material (PCM) Cooling Vest

“…The parameters that we varied were the PCM thickness (obtained from m 3 = ρ 3 A 3 d 3 ) and the PCM melting temperature, T 3 m . Figure 7a shows that the plateau cooling power drops linearly with the melting temperature of the PCM, as could be expected from Equation (18). Note that the cooling power is independent of the thickness of the PCM layer that is used.…”

“…Figure 7a shows that the plateau cooling power drops linearly with the melting temperature of the PCM, as could be expected from Equation (18). Note that the cooling power is independent of the thickness of the PCM layer that is used.…”

“…Therefore, in recent years, a number of research groups developed their own numerical models in which heat and moisture transfer in personal cooling garments is modeled in combination with PCM materials. Yazdi [17][18][19] modeled the effects of cooling vests using ANSYS finite element software which allows them to include details about the PCM geometry and placement. They show that wearing cooling vests also has negative effects: increase in metabolic costs due to extra weight, sweat blockage and reduced heat loss due to vasoconstriction [19].…”

“…They show that wearing cooling vests also has negative effects: increase in metabolic costs due to extra weight, sweat blockage and reduced heat loss due to vasoconstriction [19]. In addition, they show that 49-57% of the cooling efficiency is lost to the environment due to radiation and suggest covering the PCM element with an extra insulation layer [18]. Itani [20][21][22] set up a series of heat and mass balance equations for the different clothing and PCM layers and solved them in an iterative way using an explicit numerical scheme.…”

A Meta Study of the Relationship Between Phase Change Material Parameters and Temperature Reduction in Fire Fighter Protective Clothing

“…During a phase change, energy is used purely for transition, meaning there is a period of time where no temperature change occurs [9]. When applied to the FFPC this buffer period of constant temperature has the benefit of both decreasing the rate of body temperature rise and potentially increasing the amount of time an operator can remain in the aforementioned environments [10].…”