Question

What is latent heat? How is the latent heat loss from the human body affected by \((a)\) skin wettedness and \((b)\) relative humidity of the environment? How is the rate of evaporation from the body related to the rate of latent heat loss?

Short answer

Answer: Skin wettedness refers to the proportion of skin surface covered by a layer of sweat. An increase in skin wettedness allows for more efficient latent heat loss through providing a larger surface area for evaporation. Relative humidity is the amount of moisture in the air compared to the maximum amount at a given temperature. High relative humidity makes it challenging for sweat to evaporate, slowing down latent heat loss and possibly leading to overheating. The rate of evaporation from the body is directly related to the rate of latent heat loss; higher rates of evaporation correspond to more efficient body temperature regulation. Factors such as skin wettedness and relative humidity influence the rate of evaporation and, hence, the rate of latent heat loss.

Step-by-step solution

Understand latent heat

(Latent heat is the amount of heat absorbed or released by a substance during a phase change, such as from solid to liquid or from liquid to gas, without changing its temperature. In the context of the human body, latent heat is mainly associated with the process of sweating, where the body releases heat to cool itself.)

Explaining skin wettedness effect on latent heat loss

(Skin wettedness refers to the proportion of the skin surface covered by a layer of sweat. As skin wettedness increases, it provides more surface area for sweat evaporation, allowing for more efficient latent heat loss. This is important for maintaining body temperature, especially during periods of high physical activity or hot conditions.)

Explaining relative humidity effect on latent heat loss

(Relative humidity is the amount of moisture in the air compared to the maximum amount of moisture the air can hold at a given temperature. When relative humidity is high, the air is already saturated with moisture, making it more difficult for sweat to evaporate from the skin's surface. This slows down the rate of latent heat loss and can lead to overheating. Conversely, when relative humidity is low, sweat evaporates more easily, facilitating a more efficient latent heat loss and helping to maintain a comfortable body temperature.)

Relationship between the rate of evaporation and latent heat loss

(The rate of evaporation from the body is directly related to the rate of latent heat loss. When sweat evaporates from the skin's surface, it absorbs heat from the body, cooling it down. The faster the evaporation process, the higher the rate of latent heat loss, and the more effectively the body can regulate its temperature. Factors that affect the rate of evaporation, such as skin wettedness and relative humidity, also influence the rate of latent heat loss accordingly.)