11.4:
Mechanism of heat transfer
An environment is considered thermoneutral when the human body neither consumes nor releases energy to maintain core temperature.
The body uses four mechanisms: conduction, convection, evaporation, and radiation, to maintain temperature when the environment is not thermoneutral.
Conduction is the heat flow between two objects when in direct contact. It happens when the skin comes into contact with a cold or hot object.
For example, an ice pack helps reduce fever, facilitating conductive heat loss.
Convection is transferring heat away from the body via air movement or transmitting heat to the air surrounding the skin.
For instance, a fan uses air to transmit heat away from the body.
Evaporation is the transfer of heat energy that occurs when a liquid transforms into a gas.
Sweating causes heat loss through evaporation.
Radiation is the transmission of heat from the surface of one object to another without direct contact. The body transfers heat from the uncovered surface of the body.
For example, the sun increases the temperature of the skin through radiation.
11.4:
Mechanism of heat transfer
Understanding heat transfer mechanisms is essential for understanding how our bodies maintain balance in different environmental conditions. When the environment is thermoneutral, the body is in a state of balance, neither using nor releasing energy to maintain its core temperature. However, when the environment is not thermoneutral, the body employs four heat transfer mechanisms to maintain homeostasis: conduction, convection, evaporation, and radiation. These mechanisms facilitate heat transfer from higher concentration to lower concentration regions and are fascinating and essential to our understanding of human physiology.
Conduction, a heat transfer mechanism, is a process we encounter daily. It's the transfer of heat between two objects in direct contact. In humans, this occurs when the skin contacts an object with a different temperature. For example, when a nurse places an ice pack on a patient with a fever, heat transfers from the warmer body to the colder ice pack, thereby reducing the patient's body temperature. This practical application of conduction demonstrates its relevance and importance in our understanding of thermoregulation.
Convection, another heat transfer mechanism, is a process we can observe in our surroundings. It involves the transfer of heat away from the body through air movement. It occurs when heat from the skin warms the surrounding air, which then rises and is replaced by cooler air that warms up. An example is using a fan to cool down; the fan speeds up air movement around the body, enhancing heat loss through convection. This real-life example of convection helps us visualize and understand the concept better.
Evaporation is when a liquid converts into a gas, releasing heat from the body. It is a primary method by which the body loses heat. For instance, during physical activity, humans perspire, and as the sweat evaporates, it cools the body.
Radiation is the emission of heat from the surface of one object to another without direct contact between them. For example, the body can radiate heat to the cooler surrounding environment or absorb heat from the sun, increasing body temperature without physical contact between the body and the heat source. For example, radiation is when our body feels warm standing near a bonfire, even without touching it.