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ACTIVE LEARNING PROCESS. Branch: Computer Engineering. Guided By : Prof. Jugal Panchal. Prepared By :. MOGBEKUMA CHRISTIAN 13ISCE08 MBUYI BISELELE 13ISCE09 YANNICK MANGOMBA 13ISCE10 SUMIT CHAKRABORTY 13ISCE11. What is steam?.
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ACTIVE LEARNING PROCESS Branch: Computer Engineering Guided By : Prof. JugalPanchal Prepared By : MOGBEKUMA CHRISTIAN 13ISCE08 MBUYI BISELELE 13ISCE09 YANNICK MANGOMBA 13ISCE10 SUMIT CHAKRABORTY 13ISCE11
What is steam? • As the temperature increases and the water approaches its boiling condition, some molecules attain enough kinetic energy to reach velocities that allow them to momentarily escape from the liquid into the space above the surface, before falling back into the liquid.
Some point of difference between steam and gas • Steam is state of substance in which evaporation is not completed in from its liquid state while gas is state in which there is complete vaporization of liquid. It is gaseous state • when the steam is cooled it gets condensed while the gas in gaseous state at moderate pressure and temperature
Types of steam • The steam during the steam generation exist in three different types: wet steam, dry and saturated steam and superheated steam • Wet steam: • Both the water molecules and steam coexist to form a two phase mixture,, is called wet steam. Which will be in thermal equilibrium because both of them will be at the same saturation temperature
Continued.... • Dry and saturated steam • A steam at the saturation temperature corresponding to a given pressure and having no water molecules entrained in its known as dry and saturated steam. Or dry steam. • Since the dry saturated steam does not contain any water molecules in it, its dryness fraction will be unity
contunued • Superheated steam • When a dry saturated steam is heated further at the given constant pressure, its temperature rises beyond its saturation temperature. The steam in this state is said to be superheated
Measurement of dryness fraction • The dryness fraction can be measured by experimentally. Calorimeters are used for measurement of dryness fraction of steam, they are 4 types of methods of determining the dryness fraction of steam • Bucket or barrel calorimeter • Throttling calorimeter • Separating calorimeter • Combined separating and throttling calorimeter
Bucket or Barrel calometer • This method of measuring the dryness fraction of steam is not exact method. • CONSTRUCTION : The calorimeter is placed in the vessel. The top cover is placed in position and the steam pipe is connected to main steam pipe.
Continued..... • The steam comes in contact with water in the calorimeter when steam is passed through the water. It condenses and gives out its entire enthalpy of evaporation (latent heat) and part of its sensible heat. Due to heat transfer from steam to water in the calorimeter, the temperature of water increases.
Throttling Calorimeter • Construction and Working : This calorimeter is shown in diagram is used for finding dryness fraction of steam having very low portion of wet particles i.e. High dryness fraction. In throttling as explained in diagram, total enthalpy remains constant before and after throttling process.
Separating Calorimeter • This calorimeter shown in diagram is used for measuring dryness fraction of very wet steam. This calorimeter works on principle of separating the water particles from a sample of steam and finding their mass fraction in the sample.
Combined separating and throttling Calorimeter • Separating calorimeter gives only approximate result because of complete separation of moisture by mechanical means is not possible. Throttling calorimeter is not suitable, if steam is very wet (x≤0.9). Also throttling calorimeter fails if the steam is not superheated after throttling for accurate measurement of dryness fraction of steam.