Heat transfer ppt

Without this ability, the material--like wood- does not conduct heat well. The friction between the wall and the flowing fluid reduces its velocity to zero. By adding the insulation around the pipe the outside surface area is increased, which will increase the heat transfer. In other word, the law states that the rate of energy emission from a black body is proportional to the fourth power of the absolute temperature. Heat is transferred only by conduction through this layer.

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Potential energy is the energy which a body possesses as a consequence of its position in a gravitational field Kinetic energy is the energy which a body possesses as a consequence of its motion e.

It is also known as film coefficient tranwfer heat transfer coefficient of the film. The presence of water in steam pipes should never be permitted.

Conductive heat cannot travel through a vacuum. A hot storage vessel or a steam pipe will lose heat to the atmosphere by radiation, conduction and convection. By convection is meant the process of heat transport occurring through the movement of the macroparticles of the liquid or gas in space from a region of one atmosphere to that of another.

One-hundredth the diameter of a human hair. This increase in energy can flow through materials and from one material to another.

Thermal conductivity values Gases Liquids Solids — Air. To make this website work, we log user data and share it with processors. On the other hand, since convection currents form very easily, the heat loss from an unlagged surface is considerable.

The water separator is always fitted near the boiler to separate water carried forward mechanically from the boiler.

HEAT TRANSFER. - ppt download

Within certain limits, the higher the number of the tubes in the bundle, the greater will be the total surface area offered for heat transfer. If on the hot side of the wall, the film layer has a thickness of x1, the eq. That means the transfer of energy of one atom to the next is more effective.

In other word, the law states that the rate of energy emission from a black body is proportional to the fourth power of the absolute temperature. The amount of latent heat released is 2 — 5 times greater than the amount of sensible heat in the hot water saturated water tranxfer condensation. In addition to these simple flow arrangements, more complex ones are encountered in practice: Heat is a form. Shorter wavelengths carry more energy than longer wavelengths.

The radiation of all bodies depends on temperature.

Steam is created by heating liquid water to a point where the intermolecular trxnsfer between the molecules are broken, allowing the molecules to move apart. This is the idea behind a styrofoam coolers, the air pockets between the styrofoam beads do not conduct heat very well.


The temperature at which the first water molecule transforms to vapor is called the boiling point. If the fluids cross each other, the pattern is referred to as cross —flow c.

When heat is being conducted from one fluid to another through a solid barrier e. In a boiler, if steam is transter away faster than it is being generated, the surface of water will be below atmospheric pressure. Without this ability, the pppt wood- does not conduct heat well.

Water being a better conductor of heat than dry steam, will act as a conductor between the steam and the metallic pipe, setting up active condensation and preventing economical working of boiler. Conduction Conduction is the transfer of thermal energy by collisions between particles in matter. Thermal resistance is known as the R-value The R-value of a p;t is its resistance to heat flow and is an indication of its ability to insulate.

Fiberglass is not a good conductor nor is air. This latent heat is released instantaneously and is transferred by means of a heat exchanger to the product being heated. Less dense materials are better insulators.

Heat can be conducted through solids, liquids and gases.

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