Related Concept Videos
01:20Mechanisms of Heat Transfer II
In convection, thermal energy is carried by the large-scale flow of matter. Ocean currents and large-scale atmospheric circulation, which result from the buoyancy of warm air and water, transfer hot air from the tropics toward the poles and cold air from the poles toward the tropics. The Earth’s rotation interacts with those flows, causing the observed eastward flow of air in the temperate zones. Convection dominates heat transfer by air, and the amount of available space for the airflow...
01:14Mechanisms of Heat Transfer I
Just as interesting as the effects of heat transfer on a system are the methods by which the heat transfer occur. Whenever there is a temperature difference, heat transfer occurs. It may occur rapidly, such as through a cooking pan, or slowly, such as through the walls of a picnic ice box. So many processes involve heat transfer that it is hard to imagine a situation where no heat transfer occurs. Yet, every heat transfer takes place by only three methods: conduction, convection, and radiation.
01:14Mechanisms of Heat Transfer
Heat transfer between the human body and its environment occurs through four main mechanisms: conduction, convection, radiation, and evaporation.
Conduction, accounting for approximately 3% of body heat loss at rest, is the process of exchanging heat between molecules of two materials in direct contact. This can result in both heat loss and gain. For instance, when the body is submerged in water, which conducts heat 20 times more effectively than air, it can either lose or gain significant heat.
Conduction, accounting for approximately 3% of body heat loss at rest, is the process of exchanging heat between molecules of two materials in direct contact. This can result in both heat loss and gain. For instance, when the body is submerged in water, which conducts heat 20 times more effectively than air, it can either lose or gain significant heat.
01:19Mechanism 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...
03:02Constant Pressure Calorimetry
Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a substance. The heat is exchanged with a calibrated and insulated device called the calorimeter. Calorimetry experiments are based on the assumption that there is no heat exchange between the insulated calorimeter and the external environment. The well-insulated calorimeters prevent the transfer of heat between the calorimeter and its external...
01:16Specific Heat
The specific heat capacity of a substance refers to the energy required to increase the temperature of one gram of that substance by one degree Celcius. Specific heat capacity is often represented in calories (cal), grams (g), and degrees Celsius (oC), but can also be expressed in joules (J), kilograms (kg), and Kelvin (K), among other units.
For example, increasing the temperature of one gram of water by 1°C requires one calorie of heat energy and can be written as 1 cal/g-°C, or 4186 J/kg/K.
For example, increasing the temperature of one gram of water by 1°C requires one calorie of heat energy and can be written as 1 cal/g-°C, or 4186 J/kg/K.
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Published on: April 10, 2017
A laboratory exercise using a physical model for demonstrating countercurrent heat exchange.
Catherine Loudon1, Elizabeth C Davis-Berg, Jason T Botz
1Department of Ecology and Evolutionary Biology, University of California, Irvine, 92697-2525, USA. cloudon@uci.edu
Advances in Physiology Education
|March 3, 2012
Summary
Students learned about countercurrent exchange using a physical model mimicking bird legs. This laboratory exercise demonstrates how fluid flow direction impacts heat and chemical transport efficiency.
Area of Science:
- Physiology
- Biophysics
- Educational Laboratory Models
Background:
- Countercurrent exchange is a biological mechanism for efficient transport of heat or chemicals.
- It involves fluids moving in opposite directions across a permeable barrier.
- This mechanism is crucial for understanding physiological processes like kidney function and thermoregulation.
Purpose of the Study:
- To teach students the physical principles of countercurrent exchange mechanisms.
- To illustrate how fluid flow direction influences exchange efficiency.
- To provide a hands-on model for understanding biological heat and chemical transport.
Main Methods:
- A physical laboratory model was constructed to simulate countercurrent exchange.
- The model mimicked the arrangement of blood vessels in bird legs.
- Water flowing through tubing served as a proxy for blood flow.
Main Results:
- The model demonstrated that countercurrent flow is more efficient than concurrent flow for heat and chemical exchange.
- It highlighted how vessel looping minimizes exchange at the bend.
- Students gained a better understanding of gradient-driven transport.
Conclusions:
- Physical models are effective tools for teaching complex physiological concepts like countercurrent exchange.
- Understanding countercurrent exchange principles aids in comprehending kidney function and circulatory system adaptations.
- The laboratory exercise reinforced the fundamental concept of passive transport down gradients.