How a Condenser Works

There are a number of condenser auxiliaries that are essential to the proper functioning of the condenser: 1)a condensate hot well for collecting the condensate, 2) a condensate pump to return the condensate to a surge tank where it can be reused as boiler feed-water; 3) a circulating pump for circulating the cooling water; 4) an atmosphere relief valve for relieving the pressure in the condenser in case the condenser or auxiliaries do not function properly; 5) an air ejector or a vacuum pump for removing the non-condensable gases from the condenser.

The condensate pump and circulating-water pump are generally of the centrifugal type. If the source of the cooling water is a lake or a river, there is no need for water conservation. However, in many localities, the water supply may be low. In such case, the cooling water, after passing through the condenser, is pumped to a cooling pond or cooling tower where it is cooled by contact with air and then is re-circulated through the condenser. If non-condensable gases are permitted to collect in the condenser, the vacuum in the condenser will decrease. A decrease in the vacuum will result in a decrease in the pressure drop through the turbine and will affect adversely the turbine efficiency. Also, the non-condensable gases are highly corrosive. Thus, their removal from the condenser is essential. They may be removed by a vacuum pump or by a steam-jet air ejector.

Steam enters the first and second stages through nozzles where it acquires a high velocity. The air and some vapor from the main condenser are entrained by the high-velocity steam and are compressed in the first stage, forcing tube. The forcing tube is the Venturi-shaped section. The steam and vapor are condensed on the intercondenser and drained to the .hot well of the main condenser.

Air in the inter-condenser is then entrained by high-velocity steam leaving the second-stage nozzles and is com-pressed further in the second stage, forcing tube. Steam is condensed in the after condenser and is drained to the main condenser. The air is vented to the atmosphere. Normally, condensate from the turbine condenser is used as cooling water to condense the steam in the ejector. Both the condensate and cooling water will then be returned to a surge tank.

The Two-Drum Water-Tube Boiler

A typical small two-drum water-tube boiler is fired by a spreader stoker equipped with a dump grate. By means of baffles, the gases are forced to follow a path from the furnace to the boiler exit. This arrangement of gas flow is known as a "three pass" design. A water level is maintained slightly below the midpoint in the steam drum. Water circulates from the steam drum to the lower or mud drum through the six rows of tubes in the rear of the boiler-tube bank where the comparatively low gas temperature results in a low heat-transfer rate. Circulation is from the mini drum to the steam drum through the front boiler tubes and the side-wall furnace tubes. The side-wall furnace tubes are supplied with water from the mud drum by means of circulators connected to rectangular water boxes located in the side walls at the level of the grate. Water for the front-wall tubes is supplied to a round front nail header by down-comer tubes connected to the steam drum and insulated from the furnaces by a row of insulating brick. Most of the steam is generated in the furnace-wall tubes and in the first and second rows of boiler tubes which can “see” the flame in the furnace and absorb energy by radiation.

Boilers of this type have been standardized in a range of sizes capable of generating 8,000 to 50,000 lb of steam per hr.

The position of the drums and the shape of the tubes result in a compact unit having a well-shaped and economically constructed furnace. By simple changes in the arrangement of furnace-wall tube, the design can be adopted to almost any kind of firing equipment and fuel.

Energy

Energy is the property (or the quantity of the property) of changing the state of a system or doing work. The expressions energy and power have different meaning in different scientific and non-scientific fields. Physics aims to explain quantitatively this property and gives a definition that makes it possible to consider energy as a description of the whole state and the different ways jobs are done are unified in this treatment.

Energy is a fundamental quantity that every physical system possesses; it allows us to predict how much work the system could be made to do, or how much heat it can exchange. In the past, energy was discussed in terms of easily observable effects it has on the properties of objects or changes in state of various systems. Basically, if something changes, some sort of energy was involved in that change. As it was realized that energy could be stored in objects, the concept of energy came to embrace the idea of the potential for change as well as change itself. Such effects (both potential and realized) come in many different forms; examples are the electrical energy stored in a battery, the chemical energy stored in a piece of food, the thermal energy of a hot water heater, or the kinetic energy of a moving train. To simply say energy is "change or the potential for change", however, misses many important examples of energy as it exists in the physical world.

Energy can be used not only to produce observable change, it also is used to prevent change in which case unaided observation of this kind of energy can be difficult. For example, looking at a statue holding a 50 pound weight, the presence of energy needed to do so may not be observable. However, if you are holding up the fifty pound weight instead of the statue the need for energy to accomplish this becomes apparent. You can feel the gravitational force on you both when you are moving the weight up and when you are not moving it. Energy can be readily transformed from one form into another; for instance, using a battery to power an electrical heater converts electrical energy into thermal energy. In the previous example of holding the fifty pound weight, the work you perform to raise the weight is observed as kinetic energy of motion which is converted to potential energy and added to the weight's potential energy as you continue to hold the weight up against the pull of gravity. Letting go of the weight once again transforms this stored potential energy back into kinetic energy as the weight falls under the force of gravity. The law of conservation of energy states that the total amount of energy, corresponding to the sum of a system's constituent energy components, remains constant. Scientists have also defined several forms of energy that are not easily measured by the unaided observer.