Hydroweave® - How It Works
 
In today's market, there are several different types of cooling options that are available for portable body cooling. The most sophisticated of these are essentially portable, tethered air conditioners that have been developed for military use, particularly explosive ordinance disposal personnel and astronauts. As one would expect, these systems are not only heavy, but are also extremely expensive. Furthermore, as with any system, there is the tradeoff between cooling effect and the burden on the individual by adding weight. Other systems relying on fluid flow include recirculating vests using pumps and motors; these also suffer from severe weight penalties and are generally not user friendly.

Probably the most common cooling garments, (vests) are those that rely on ice packs which are inserted into various pockets built into the vest. These systems tend to be heavier and also offer limited cooling effect when compared to the BodyTeq products. Ice packs are bulky and the fact that they are placed at specific body areas means that cooling is only provided to those locations where the pockets are located. Additionally, this style of design makes it more difficult to configure the garment for full body applications, and non-uniform body cooling can present false impressions to the wearer about his or her true physiological state; e.g., core body temperature is rising even though he or she feels cool.

Since BodyTeq products do not rely on bulky, localized cooling areas, the weight penalty is minimal and works out to be much less than a similarly designed ice pack vest. BodyTeq products must be soaked in water before use, while icepacks must be kept in a freezer before use. Typically, it is much easier to soak the garment than it is to have ready access to a freezer.

The effectiveness of the garment is based on its ability to absorb heat from the body and release that heat to the outside environment. The water that is absorbed by the batting material provides a heat transfer medium for this effect. As the heat accumulates in the material, the heat causes the water to evaporate from the vest. The direction of this heat is to the outside because the moisture differential is less to the outside (the environment next to the body is generally at a high relative humidity). Thus, the garment provides both evaporative cooling and conduction, the two principal means of body cooling.

The length and magnitude of this cooling effect will depend upon several factors:

• The activity level of the wearer

• The temperature and relative humidity of the environment

• The physical condition of the wearer

• The type and configuration of other clothing being worn

As might be expected, higher activity levels will reduce the effective cooling time. Similar effects will be experienced with relatively high temperatures and relative humidity. In addition, the greater the surface area of the body covered and in contact with Hydroweave® fabric, a more substantial cooling effect will result. Cooling effects may be diminished if insultated underclothing is worn to limit contact of the vest with the wearer's skin, or if barrier clothing is worn over the vest, creating a microenvironment immediately outside the vest.

Use of these garments is limited to warm-to-hot conditions, or where activity is high during moderate temperature environments. Use of these garments is not advisable during cool weather operations because heat will be transferred from the body to the garment making the wearer feel uncomfortably cool.

Some concerns have arisen that Hydroweave® can act as a heat sink under certain environmental conditions, i.e., once it has absorbed heat from the body in a warm environment, then continued wearing could result in heat transfer back to the body as the garment's cooling ability is depleted. This phenomena should not be a concern because as explained above, the driving force is away from the body. The microenvironment between the body and the vest is generally at high humidity, therefore the evaporative heat is released away from the body as water evaporates from the BodyTeq product. In addition, any system (including ice pack technology) will have its effectiveness diminished over time where the transfer of heat away from the body is lessened as the material reaches its heat storage capacity. For example, as the icepacks absorb heat, they obviously reach ambient temperature. The same is true for BodyTeq products, but the key difference between the delivery systems is that while ice packs rely on conductive cooling only, BodyTeq products made with Hydroweave® use the two forms of heat transfer for achieving their cooling effect.

Finally, it must be remembered that a person who is sweating will already be generating water that is absorbed into conventional clothing or stays on the surface of the skin. Since the BodyTeq product is already providing cooling, it is preventing much of the body sweating that normally occurs and uses the material instead to transfer heat via evaporation of the water in the material.
 

Evaporative Cooling Discussion

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