Heat transfer plays a significant role in determining the thermal comfort and performance of clothing. There are three main modes of heat transfer that affect clothes:
Conduction: Conduction is the transfer of heat through direct contact between objects. When you touch a hot surface, such as a metal plate or a hot stove, heat is conducted from the object to your skin. Similarly, heat can be conducted through the fibers of clothing. Different materials have different thermal conductivities, which affect how much heat is transferred through them. For example, metals are good conductors of heat, while materials like wool or air pockets in insulation layers reduce heat conduction.
Convection: Convection is the transfer of heat through the movement of a fluid, such as air or water. In the context of clothing, convection occurs when air circulates around the body and between clothing layers. When air comes into contact with your skin, it absorbs heat and rises, creating a convective loop. Clothing can affect convection by trapping air next to the body or allowing air to circulate and carry away heat. For example, tightly woven fabrics or layers with trapped air pockets can reduce convective heat loss.
Radiation: Radiation is the transfer of heat through electromagnetic waves. All objects emit and absorb radiant heat energy. In the case of clothing, radiation occurs between the body and the environment. Your body radiates heat in the form of infrared radiation, and this radiation can be absorbed or reflected by clothing. Dark-colored, absorbent materials tend to absorb more radiant heat, while light-colored or reflective materials reflect it. The properties of clothing materials influence how much radiant heat is absorbed or reflected.
To optimize thermal comfort, clothing designers consider these heat transfer mechanisms. They select appropriate materials and design features to regulate heat transfer based on the intended use of the garment. For instance, in cold weather, clothing may incorporate insulating layers and materials that minimize heat loss through conduction, convection, and radiation. In contrast, in hot weather, clothing may emphasize breathability and moisture wicking to facilitate heat dissipation through evaporation and convection.
It's important to note that the specific properties and design of clothing, as well as environmental factors, will influence how heat transfer affects comfort and performance.