Sería muy fácil buscar estas definiciones en la Wikipedia pero, tal y como reza nuestro eslogan “Energía para todos los públicos”, vamos a intentar ofrecer una explicación para dummies de los conceptos de radiación, conducción y convección.
Conducción
Es la más sencilla de entender, consiste en la transferencia de calor entre dos puntos de un cuerpo que se encuentran a diferente temperatura sin que se produzca transferencia de materia entre ellos.
Ejemplo:
Tengo una barra metálica con un extremo a 80ºC y otro a temperatura ambiente, si no tengo ninguna otra influencia externa y el extremo caliente se mantiene a 80ºC, habrá una transferencia de calor por conducción desde el extremo caliente hacia el frío incrementando la temperatura de este último
Radiación
Es el calor emitido por un cuerpo debido a su temperatura, en este caso no existe contacto entre los cuerpos, ni fluidos intermedios que transporten el calor. Simplemente por existir un cuerpo A (sólido o líquido) a una temperatura mayor que un cuerpo B existirá una transferencia de calor por radiación de A a B.
Para que este fenómeno se perciba es necesario un cuerpo a una temperatura bastante elevada ya que la transferencia térmica en este caso depende de la diferencia de temperaturas a la cuarta potencia: Ta4-Tb4.
Ejemplo:
Dejas tu coche aparcado en la playa un día no muy caluroso, al volver te apoyas sin querer en el capó del coche y el grito se oye a varios kilómetros de distancia. En este caso aunque el sol se encuentra a bastante distancia de nuestro coche, su temperatura absoluta es tan alta que hace que la transferencia por radiación sea muy importante. Aquí no tiene a penas influencia que el aire ambiente esté caliente ya que si hubiéramos dejado el coche a la sombra esto no ocurriría.
Convección
En este sistema de transferencia de calor interviene un fluido (gas o líquido) en movimiento que transporta la energía térmica entre dos zonas.
La transmisión de calor por convección puede ser:
- Forzada: a través de un ventilador (aire) o bomba (agua) se mueve el fluido a través de una zona caliente y éste transporta el calor hacía la zona fría.
- Natural: el propio fluido extrae calor de la zona caliente y cambia su densidad haciendo que se desplace hacía la zona más fría donde cede su calor.
Ejemplo:
Si enciendo un radiador y espero a que alcance una temperatura bastante alta, no tengo más que poner una mano encima (a una distancia prudencial) para ver que existe un flujo de aire por convección natural. El aire alrededor del radiador se calienta disminuyendo su densidad, por lo tanto, al pesar menos que el aire ambiente, fluye hacía arriba dando paso a un “aire de renovación” alrededor del radiador, reiniciando el proceso de forma cíclica.
Finalmente, os dejamos una imagen que resume perfectamente los tres métodos de transferencia de calor: conducción, convección y radiación.
One of the topics most treated in Nergiza although indirectly is the transfer of heat, whether in the form of heating, air conditioning or energy losses. That is why today we want to clarify the three basic forms of heat transmission that exist: radiation, conduction and convection. It would be very easy to look up these definitions in Wikipedia but, as our slogan "Energy for all publics", we will try to offer an explanation for dummies of the concepts of radiation, conduction and convection. Driving It is the simplest to understand, consists of the transfer of heat between two points of a body that are at different temperature without any transfer of matter between them. Example: I have a metal rod with one end at 80ºC and another at room temperature, if I do not have any other external influence and the hot end is maintained at 80ºC, there will be a heat transfer by conduction from the hot end to the cold increasing the temperature of this latest Radiation It is the heat emitted by a body due to its temperature, in this case there is no contact between the bodies, nor intermediate fluids that carry the heat. Simply because there is a body A (solid or liquid) at a temperature higher than a body B there will be a heat transfer by radiation from A to B. For this phenomenon to be perceived, a body at a fairly high temperature is necessary since the thermal transfer in this case depends on the temperature difference at the fourth power: Ta4-Tb4.
One of the topics most treated in Nergiza although indirectly is the transfer of heat, whether in the form of heating, air conditioning or energy losses. That is why today we want to clarify the three basic forms of heat transmission that exist: radiation, conduction and convection. It would be very easy to look up these definitions in Wikipedia but, as our slogan "Energy for all publics", we will try to offer an explanation for dummies of the concepts of radiation, conduction and convection. Driving It is the simplest to understand, consists of the transfer of heat between two points of a body that are at different temperature without any transfer of matter between them. Example: I have a metal rod with one end at 80ºC and another at room temperature, if I do not have any other external influence and the hot end is maintained at 80ºC, there will be a heat transfer by conduction from the hot end to the cold increasing the temperature of this latest Radiation It is the heat emitted by a body due to its temperature, in this case there is no contact between the bodies, nor intermediate fluids that carry the heat. Simply because there is a body A (solid or liquid) at a temperature higher than a body B there will be a heat transfer by radiation from A to B. For this phenomenon to be perceived, a body at a fairly high temperature is necessary since the thermal transfer in this case depends on the temperature difference at the fourth power: Ta4-Tb4.
One of the topics most treated in Nergiza although indirectly is the transfer of heat, whether in the form of heating, air conditioning or energy losses. That is why today we want to clarify the three basic forms of heat transmission that exist: radiation, conduction and convection. It would be very easy to look up these definitions in Wikipedia but, as our slogan "Energy for all publics", we will try to offer an explanation for dummies of the concepts of radiation, conduction and convection. Driving It is the simplest to understand, consists of the transfer of heat between two points of a body that are at different temperature without any transfer of matter between them. Example: I have a metal rod with one end at 80ºC and another at room temperature, if I do not have any other external influence and the hot end is maintained at 80ºC, there will be a heat transfer by conduction from the hot end to the cold increasing the temperature of this latest Radiation It is the heat emitted by a body due to its temperature, in this case there is no contact between the bodies, nor intermediate fluids that carry the heat. Simply because there is a body A (solid or liquid) at a temperature higher than a body B there will be a heat transfer by radiation from A to B. For this phenomenon to be perceived, a body at a fairly high temperature is necessary since the thermal transfer in this case depends on the temperature difference at the fourth power: Ta4-Tb4.
One of the topics most treated in Nergiza although indirectly is the transfer of heat, whether in the form of heating, air conditioning or energy losses. That is why today we want to clarify the three basic forms of heat transmission that exist: radiation, conduction and convection. It would be very easy to look up these definitions in Wikipedia but, as our slogan "Energy for all publics", we will try to offer an explanation for dummies of the concepts of radiation, conduction and convection. Driving It is the simplest to understand, consists of the transfer of heat between two points of a body that are at different temperature without any transfer of matter between them. Example: I have a metal rod with one end at 80ºC and another at room temperature, if I do not have any other external influence and the hot end is maintained at 80ºC, there will be a heat transfer by conduction from the hot end to the cold increasing the temperature of this latest Radiation It is the heat emitted by a body due to its temperature, in this case there is no contact between the bodies, nor intermediate fluids that carry the heat. Simply because there is a body A (solid or liquid) at a temperature higher than a body B there will be a heat transfer by radiation from A to B. For this phenomenon to be perceived, a body at a fairly high temperature is necessary since the thermal transfer in this case depends on the temperature difference at the fourth power: Ta4-Tb4.
Example:
You leave your car parked on the beach one day not very hot, when you return you inadvertently lean on the hood of the car and the shout is heard several kilometers away. In this case, although the sun is quite a distance from our car, its absolute temperature is so high that it makes the radiation transfer very important. Here it does not have to influence that the ambient air is hot because if we had left the car in the shade this would not happen.
Convection
In this heat transfer system involves a moving fluid (gas or liquid) that transports the thermal energy between two zones.
Convection heat transfer can be:
Forced: through a fan (air) or pump (water) moves the fluid through a hot zone and this moves the heat to the cold zone.
Natural: the fluid itself extracts heat from the hot zone and changes its density causing it to move to the cooler area where it gives off its heat.
Example:
If I turn on a radiator and wait until it reaches a fairly high temperature, I have only to put a hand on it (at a prudential distance) to see that there is a flow of air by natural convection. The air around the radiator is heated by decreasing its density, therefore, by weighing less than ambient air, it flows upwards giving way to a "refreshing air" around the radiator, restarting the process cyclically.
Finally, we leave you an image that perfectly summarizes the three methods of heat transfer: conduction, convection and radiation.
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