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Dept. of Mech & Mfg. Engg. 1 Instructions GENERAL: Enter the room In Time. Switch off your mobile phones. Dont use Lap Tops during my lecture. Maintain Discipline inside the class. Maintain one Separate Note book. Note down Sketches, important points and definitions.

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Dept. of Mech & Mfg. Engg. 2 Instructions Mark distribution: Test = 40 marks Assignment / surprise test = 10 marks End Sem Exam = 50 marks Test: 40 marks There will be 3 Tests. Each test is of 20 marks (10 each from 2 parts) Out of 3 tests, best 2 are considered. Assignment / surprise test: There will be 3 assignments / surprise tests. Each assignment / surprise test is of 10 marks. To award 10 marks, all are considered.

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Dept. of Mech & Mfg. Engg. 3 Reference books 1.Mechanical Engineering Science: K.R. Gopalakrishna, Subhas Publications 2.Elements of Mechanical Engineering: Roy & Choudhury, Laxmi Publications Pvt. Ltd 3.Mechanical Engineering Science: B.K. Mishra, Kumar & Kumar Publishers Pvt. Ltd 4.Mechanical Engineering Science: R.K Rajput, Laxmi Publications Pvt. Ltd.

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Dept. of Mech & Mfg. Engg. 4 MES Part A Part B 1.Properties of steam 2.Steam boilers 3.Steam turbines 4.Refrigeration 5.I C engines 6.Lubrication 1.Transmission of power 2.Machine tools 3.Casting 4.Forging 5.Welding

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Dept. of Mech & Mfg. Engg. 5 PROPERTIES OF STEAM Chapter 1: PROPERTIES OF STEAM Define steam:Define steam: Vapour form of water is called STEAM. Water in solid phase: We call it as ICE Water in liquid phase: We call it as WATER Water in gaseous phase: We call it as STEAM.

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Dept. of Mech & Mfg. Engg. 6 Application of steam Food processing industry. Cooking: hotels, restaurants etc. Used as a working fluid in steam engines and steam turbines. Used in industries for process heating. Petrochemical industry. Washing/drying/sterilizing in hospitals. Health clinic / gym.

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Dept. of Mech & Mfg. Engg. 7 Formation of steam experiment Consider 1 kg of water at 0 o C taken in a cylinder fitted with a freely moving frictionless piston as shown in fig. W Cylinder 1 kg water at 0 o C Pressure P

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Dept. of Mech & Mfg. Engg. 8 The initial condition of water at 0 o C is represented by the point A on the temperature-enthalpy graph A Temperature Enthalpy (h) Temperature (T) o C

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Dept. of Mech & Mfg. Engg. 9 A Temperature Enthalpy (h) Temperature (T) o C T Sat B hfhf Sensible heat h fg Latent heat T Sup AOS C D DOS Fig. 1Fig. 2 Fig. 3 Fig. 4Fig. 5 A BCD

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Dept. of Mech & Mfg. Engg. 10 Definitions Sensible heat :Sensible heat (h f ) : It is defined as the amount of heat required to raise the temperature of 1 kg of water from 0 0 C to the saturation temperature T sat °C at a given constant pressure. Saturation temperature( T sat ):Saturation temperature( T sat ): It is defined as the temperature at which the water begins to boil at the stated pressure

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Dept. of Mech & Mfg. Engg. 11 Latent heat of evaporation (h fg ):Latent heat of evaporation (h fg ): It is defined as the amount of heat required to evaporate 1 kg of water at saturation temperature to 1 kg of dry steam at the same saturation temperature at given constant pressure superheated temperature (T sup )The temperature of the steam above the saturation temperature at a given pressure is called superheated temperature (T sup )

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Dept. of Mech & Mfg. Engg. 12 Amount of superheat (AOS) or enthalpy of superheat:Amount of superheat (AOS) or enthalpy of superheat: It is defined as the amount of heat required to increase the temperature of dry steam from its saturation temperature to any desired higher temperature at the given constant pressure. Degree of superheat (DOS):Degree of superheat (DOS): It is the difference between the superheated temperature and the saturation temperature.

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Dept. of Mech & Mfg. Engg. 13 Different states of steam. The steam as it is being generated can exist in three different states, 1. Wet steam 2. Dry saturated steam 3. Superheated steam.

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Dept. of Mech & Mfg. Engg. 14 Wet Steam: A wet steam is defined as a two-phase mixture of finely divided water particles and dry steam in thermal equilibrium at the saturation temperature corresponding to a given pressure.

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Dept. of Mech & Mfg. Engg. 15 dryness fraction xThe quality of the wet steam is specified by the dryness fraction which indicates the amount of dry steam present in the given quantity of wet steam and is denoted as x. The dryness fraction of a steam is defined as the ratio of mass of the actual dry steam present in a known quantity of wet steam to the total mass of the wet steam.

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Dept. of Mech & Mfg. Engg. 16 Let m g = Mass of dry steam present in the sample quantity of wet steam m f = Mass of suspended water molecules in the sample quantity of wet steam x = m f + m g m g The dryness fraction of the wet steam will be less than 1.

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Dept. of Mech & Mfg. Engg. 17 Dry Saturated Steam: A saturated steam at the saturation temperature corresponding to a given pressure and having no water molecules entrained in it.

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Dept. of Mech & Mfg. Engg. 18 Superheated Steam: A superheated steam is defined as the steam which is heated to temperature higher than its saturated temperature at the given pressure.

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Dept. of Mech & Mfg. Engg. 19 Advantages of Superheated Steam: At a given pressure, the superheated steam possess more heat energy compared to dry saturated steam or wet steam at the same pressure, hence its capacity to do the work will be higher. When superheating is done by the exhausting combustion gases in a boiler, there will be a saving of the energy of combustion which improves the thermal efficiency of the boiler. While expanding in a steam turbine it reduces and in extreme cases prevents the condensation, thus giving better economy. Disadvantages of Superheated Steam: –The high superheated temperatures poses problems in the lubrication. –Higher depreciation and initial cost.

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Dept. of Mech & Mfg. Engg. 20 Enthalpy equations for different states of steam a) Enthalpy of Dry saturated Steam: h g = h f +h fg kJ/kg A BC Sensible Heat Latent Heat h fg T su p Temperature Enthalp y Amount of Superheat Degree of Superheat TsTs hfhf D Temperature

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Dept. of Mech & Mfg. Engg. 21 b) Enthalpy of Wet Steam: h =h f +x h fg kJ/kg A BC Sensible Heat Latent Heat h fg T su p Temperature Enthalp y Amount of Superheat Degree of Superheat TsTs hfhf D Temperature

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Dept. of Mech & Mfg. Engg. 22 c) Enthalpy of Superheated Steam: h sup = h f +h fg + C sup (T sup - T sat ) kJ/kg A BC Sensible Heat Latent Heat h fg T su p Temperature Enthalp y Amount of Superheat Degree of Superheat TsTs hfhf D Temperature

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Dept. of Mech & Mfg. Engg. 23 d) Degree of superheat (DOS): DOS = (T sup - T sat ) A BC Sensible Heat Latent Heat h fg T su p Temperature Enthalp y Amount of Superheat Degree of Superheat TsTs hfhf D Temperature

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Dept. of Mech & Mfg. Engg. 24 e) Amount of superheat (AOS): AOS = C sup (T sup - T sat ) A BC Sensible Heat Latent Heat h fg T sup Temperature Enthalpy Amount of Superheat Degree of Superheat TsTs hfhf D Temperature

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