Quick Answer: What Is The Difference Between Free Convection And Natural Convection?

What kind of factors increase convection?

Convection is most effective where the hot surface is vertical.

The air is heated by the plate and rises by the “chimney effect.” Forced airflow parallel to the plate will increase heat transfer.

Heat transfer will depend on surface area, height, and temperature difference (Fig.


What is the law of convection?

Convection-cooling is sometimes loosely assumed to be described by Newton’s law of cooling. Newton’s law states that the rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings while under the effects of a breeze.

What are examples of conduction convection and radiation?

Example of situation with conduction, convection, and radiationConduction: Touching a stove and being burned. Ice cooling down your hand. … Convection: Hot air rising, cooling, and falling (convection currents) … Radiation: Heat from the sun warming your face.

What is free convection and forced convection?

Convection is classified as natural (or free) and forced convection depending on how the fluid motion is initiated. … Whereas in forced convection, the fluid is forced to flow over a surface or in a tube by external means such as a pump or fan.

Is boiling water an example of convection?

The hot water molecules become less dense, and they rise above the denser cooler molecules. This movement of molecules creates convection currents. Boiling water is an example of forced convection.

What is needed for convection?

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.

What is an example of natural convection?

One of the most common examples of natural convection is the phenomena of the sea and land breeze. Sea breeze: This phenomenon occurs during the day. The sun heats up both the sea surface and land. … Land Breeze: This phenomenon occurs during the night when the situation reverses.

What are 4 examples of convection?

13 Examples Of Convection In Everyday LifeBreeze. The formation of sea and land breeze form the classic examples of convection. … Boiling Water. Convection comes into play while boiling water. … Blood Circulation in Warm-Blooded Mammals. … Air-Conditioner. … Radiator. … Refrigerator. … Hot Air Popper. … Hot Air Balloon.More items…

Is wind natural or forced convection?

The convection caused by winds is natural convection for the earth, but it is forced convection for bodies subjected to the winds since for the body it makes no difference whether the air motion is caused by a fan or by the winds.

What causes free convection?

Free convection refers to fluid motion induced by buoyancy forces. Buoyancy forces may arise in a fluid for which there are density gradients and a body force that is proportional to density. In heat transfer, density gradients are due to temperature gradients and the body force is gravitational.

How do you calculate natural convection?

Natural convection coefficient calculatorPlane area A= m2Plane perimeter P= m.Plane height L= m.Angle from vertical °Diameter D= m.Density ρ = kg/m3 Viscosity μ = N*s/m2 Specific heat C = J/kg*K. Thermal conductivity k = W/m*K. Thermal expansion coefficient β = 1/K.

What is the difference between natural convection and forced convection?

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.

Why would forced convection be used?

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.

What is the process of convection?

Convection is the process of carrying heat stored in a particle of the fluid into another location. Heat loss may occur by convection to cooler surrounding air or heat gain from surrounding warmer air.

What are two types of convection?

There are two types of convection: natural convection and forced convection. Natural convection is produced by density differences in a fluid due to temperature differences (e.g., as in “hot air rises”). Global atmospheric circulation and local weather phenomena (including wind) are due to convective heat transfer.

What causes natural convection?

The driving force for natural convection is gravity. For example if there is a layer of cold dense air on top of hotter less dense air, gravity pulls more strongly on the denser layer on top, so it falls while the hotter less dense air rises to take its place. This creates circulating flow: convection.

Where is forced convection used?

Forced convection is often encountered by engineers designing or analyzing heat exchangers, pipe flow, and flow over a plate at a different temperature than the stream (the case of a shuttle wing during re-entry, for example).

Is a true convection oven worth it?

Generally, true convection speeds up cooking by about 25%. The time savings is subtle with quick-cooking items like cookies—you’ll shave just a minute or so off the baking time—but with a whole turkey, you could save yourself nearly an hour.

What is a good example of convection?

Everyday Examples of Convection radiator – A radiator puts warm air out at the top and draws in cooler air at the bottom. steaming cup of hot tea – The steam you see when drinking a cup of hot tea indicates that heat is being transferred into the air. ice melting – Ice melts because heat moves to the ice from the air.

What are the applications of convection?

Application of Convection CurrentsHousehold ventilation can make our house cool. The air which we breathe out is warmer and lighter. … In a domestic water heater, water is heated in the boiler by a gas burner or heating coil. … An air conditioner also uses convection currents to cool a room.Jun 10, 2020