Velox Boiler 3892v

Velox Boiler Enil Kansagra-15BIE025 Parth Shah-15BIE053 Parth Modhia-15BIE031 Anand Bhesdadhiya-15BIE006 Jay Bhandari-15BIE005

Velox Boiler.? • Velox boiler is forced circulation fire tube boiler. It is mostly used in gas turbine. • In this boiler, the velocity of flue gases is greater than the velocity of sound, which causes more heat transfer from gas to the water, which increases the steam generation rate. Due to this, it is most important boiler.

Working Principle • When the velocity of the gas is greater than the speed of sound, its heat transfer rate is also increases. So more heat is transfer from gas to water as compare when the heat transfer at the subsonic speed. This is the basic principle of it. This boiler can increase the heat transfer rate or can say steam generation rate without increasing boiler size.

Construction. • Velox boiler is a fire tube forced circulation boiler. It has a gas turbine driven air compressor, which compresses the air. This compressed air enters into the vertical combustion chamber, as result, high rate of heat release from the fuel, which increases the flue gases velocity up to the sound velocity. This is a force circulation boiler, so pump is used to circulate water inside the boiler. This boiler also consist water and fire tube to maintain the flow of gas and water inside the boiler. This boiler also consists other necessary mounting and accessories like economizer, super heater, blow off valve, safety valve etc.

Mountings/Accessories. • Economizer: An economizer is a heat exchanger, used for heating the feed water before it enters the boiler. The economizer recovers some of waste heat of hot flue gases going to chimney. It helps in improving the boiler efficiency. It is placed in the path of flue gases at the rear end of the boiler.

• Super heater: It is a heat exchanger in which heat of combustion products is used to dry the wet steam, pressure remains constant, its volume and temperature increase. Basically, a super heater consists of a set of small diameter U tubes in which steam flows and takes up the heat from hot flue gases.

• Feed Water Pump: It is used to feed the water at a high pressure against the high pressure of steam already existing inside the boiler.

• Steam Injector: A steam injector lifts and forces the feed water into the boiler. It is usually used for vertical and locomotive boilers and can be accommodated in small space. It is less costly. It does not have any moving parts thus operation is salient.

Working The Velox boiler works as a basic heat exchanger. The working of this boiler is as follow. • The air is compressed by air compressor driven by gas a turbine driven. This compressed air es from the combustion chamber, where more heat release by the fuel which increase the velocity of the flue gases up to sound velocity. From the bottom of combustion chamber, this flue gases from the fire tubes. These fire tubes surrounded by the evaporator water tubes. • The water from the economizer es from the evaporator tube force by a circulating pump. This water es 15 - 20 time from the evaporator tube at very high speed. Due to this high speed circulation, heat is transfer from the gases to the water at very high rate.  The mixture of water and steam is formed which further es from the water and steam separator.

Working (Continued..) • The steam from the steam separator es to the super heater and further for process work. The remaining water in the steam separator again es from the evaporator tube. The flue gases from the fire tubes send to the super heater tubes, where it increases the steam temperature. The gas from the super heater sends to the turbine where it rotates the gas turbine and then es from the economizer.

Advantages. 1) 2) 3) 4) 5) 6) 7)

This boiler has high heat transfer rate. It has great flexibility. It is compact in design. It can quickly be started. It is easy to control. It is fully automatic. It has great thermal efficiency of about 90 - 95%. Low excess air is required as the pressurized air is used and the problem of draught is simplified.

Disadvantages 1) Need extra ground as of horizontal constitution 2) Fuel oil burning power stations lies in the high cost of fuel. 3) It can only operate on liquid or gaseous fuels.

Comparison…

Applications • Velox boiler locomotives. • Power generation. • Velox expresso makers

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