What is the difference between force and natural circulation in a boiler?

What is the difference between force and natural circulation in a boiler?

A forced circulation boiler is a boiler where a pump is used to circulate water inside the boiler. This differs from a natural circulation boiler which relies on current density to circulate water inside the boiler. In some forced circulation boilers, the water is circulated twenty times the rate of evaporation.

What is the difference between natural circulation and forced circulation?

The type that circulates water using only the density difference is called a natural circulation boiler, while the type that includes a pump is called a forced circulation boiler.

Which boiler is natural circulation boiler?

In a natural circulation boiler the circulation is achieved by the difference in density when the water in the boiler is heated. In natural circulation steam boilers the circulation of water is by convection currents, which are set up during the heating of water.

What are the different types of circulation in boiler?

Water circulation in boiler can be classified in three different types of systems.

• Natural Circulation.
• Controlled Circulation.
• Combined Circulation.

Why must a boiler have thorough circulation?

For a boiler to make steam continuously, it must have water circulating through its tubes. Since a combination of water and steam is less dense than water, gravity will cause the water to move down and the steam/water mixture to rise.

How does a natural circulation boiler work?

Natural circulation is caused by the density difference between saturated water and heated water partially filled with steam bubbles. In a natural circulation unit the water tubes are connected to a loop, Fig. 4.3. Heat is applied to one leg, called the raiser tube, where the water–steam mixture flows upward.

What is forced circulation system?

Forced circulation systems use electrical pumps, valves, and controllers to circulate water or other heat-transfer fluids through the collectors. This enables a high degree of flexibility in the positioning of the system components. For example, the tank can be installed in a basement.

What is forced circulation cooling system?

In this method, a water pump is used to force water from the radiator to the water jacket of the engine (Fig. 5.3). After circulating the entire run of water in jacket, water comes back to the radiator where it loses its heat by the process of conduction.

What is boiler efficiency?

Definition of Boiler Efficiency is “The percentage of the total absorption heating value of outlet. steam in the total supply heating value.” In other word, it is a rate how the boiler runs efficiently.

Why economiser is used in boiler?

Economiser is a device used to heat feed water by utilising the heat in the exhaust flue gases before leaving through the chimney. It improves the economy of the steam boiler. It increases the steam raising capacity of a boiler because it shortens the time required to convert water into steam.

What is a boiler feedwater circulation system?

The piping system carrying the water to the economizer inlet header is called the feedwater piping system. The steam drum is 6.5 ft in diameter and collects and distributes the water/steam as it continuously circulates throughout the boiler.

What is circulation ratio of boiler?

Circulation ratio is defined as the ratio of the mass of the steam/water mixture to the mass of steam at the exit of the evaporator tube field. A circulation ratio of 5:1 means there is five times as much water flowing through the downcomer and into the tubes than steam being generated in the tubes.

How is forced circulation determined in a boiler?

It’s not so much the difference in temperature, it’s the difference in density between the steam and water which determines natural or forced circulation. This is determined by the pressure. The higher the pressure, the less difference in density between steam and water.

Is the boiler too big for natural circulation?

The boiler would indeed be too large and too complicated for just natural waterside circulation. In addition to Sharik’s response there are boilers that may have horizontal tubes or circuits that may be sloped but there may not be enought density difference in the water steam mix to drive the circulation.

What are the differences between natural circulation and forced circulation?

Under the subcritical pressure, the natural circulation boiler with the flue gas parameter of 16.6~18.2 MPa and the working pressure of the drum reaches 18.6~20.6 MPa, and the natural circulation still has sufficient water circulation driving force to achieve safe and reliable operation. 2. Has a fixed evaporation section end point.

Do you need a drum in forced circulation boiler?

The drum of the forced circulation boiler is no longer necessary. It can have a drum and can have no drum. However, the pump head has higher requirements and consumes more electricity. When the pump stops running, the flow of water in the pot also stops, and a reliable method is needed to prevent the water from vaporizing the water.