Convection: the mass transfer of heat from one place to another. It happens as a group of heated molecules moves to another location taking the heat with them. Convection in the water cycle is when the air near the surface is heated, then rises taking heat with it.

Mantle convection occurs because relatively hot rocks are less dense and rise in a gravitational field while relatively cold rocks are more dense and sink. The rise of hot rocks advects heat upward while the fall of cold rocks advects cold downward; this counterflow is equivalent to an upward heat flux.

Convection is a way in which heat travels. It occurs when heat is transferred by the movement of liquids or gases. Natural convection occurs when fluids are heated. When the fluid molecules are heated, the fluid becomes larger and lighter.

Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. The liquid or gas in hot areas is less dense than the liquid or gas in cold areas, so it rises into the cold areas. The denser cold liquid or gas falls into the warm areas.

Convection happens when air moves around, carrying heat from one place to another. So in order to stop convection from happening, you just have to get the air to stay still. Warm air will rise relative to cold air even when nothing else is moving it, so keeping air still is not so easy to do.

Explanation: Thermal convection is one of the forms of heat propagation that occurs in liquids and gases. For this reason, we can conclude that a good example of convection is “hot air rising and cooler air falling”.

In convection, heat supplied is absorbed by the molecules and the material expands. As this happens, density decreases and heated part of the material begins to move upwards. During the process, heat is transferred by actual motion of the molecules from one place to another. Was this answer helpful?

Conduction transfers heat from one object to another through physical contact. Convection transfers heat to air or water. Radiation transfers heat via infrared radiation. Evaporation transfers heat as water changes state from a liquid to a gas.

Natural convection, or free convection, occurs due to temperature differences which affect the density, and thus relative buoyancy, of the fluid. Heavier (denser) components will fall, while lighter (less dense) components rise, leading to bulk fluid movement.

Common units used to measure the convective heat transfer coefficient are:

1. 1 W/(m2 K) = 0.85984 kcal/(h m2 ° C) = 0.1761 Btu/(ft2 h ° F)
2. 1 kcal/(h m2 ° C) = 1.163 W/(m2 K) = 0

Spontaneous convection is driven by buoyancy for the most part and surface tension to a lesser extent.

• exposed surface area.
• viscosity.
• density.
• conductivity (when conductivity is high, there is no need for convection)
• acceleration due to gravity.

1: Natural convection heat transfer from a hot body. The temperature of the air adjacent to the hot object is higher, thus its density is lower. This movement is called the natural convection current. Note that in the absence of this movement, heat transfer would be by conduction only and its rate would be much lower.

The parameter of importance in forced convection is the Péclet number, which is the ratio of advection (movement by currents) and diffusion (movement from high to low concentrations) of heat. When the Peclet number is much greater than unity (1), advection dominates diffusion.

Forced convection creates a more uniform and therefore comfortable temperature throughout the entire home. This reduces cold spots in the house, reducing the need to crank the thermostat to a higher temperature, or putting on sweaters.

The key difference between natural and forced convection is that in natural convection, the motion of the fluid is influenced by natural means whereas, in forced convection, the motion of fluids is influenced by external means.