Tiêu đề BME Chap - 4.pdf ✅

Chapter Properties of Steam 4 syllabus Steam formation. Types of steam, Enthalpy, Specific volume, Internal energy and dryness fraction of steam, use of steam tables, steam calorimeters. 4-3 4.1 Introduction.. ... . .. *..* ************* n*******************************n 4.2 Difference between Gas and Vapour ****************************************** 4-3 4.3 Formation of Steam at Constant Pressure. Explain water Temperature- Enthalpy Diagram for water. (GTU-Summer 2015) Define the terms 1. Melting point 2. Boiling point 3. Critical point. (GTU -Summer 2017) 4-3 Ua. ************************************ 4-3 UQ. UQ. Explain steam formation with figure also draw T-H diagram. (GTU -Summer 2017,- Winter 2018) . 4-3 * *-* *** **.*-. . 4-4 Types of Steam. Define: Wet steam. (GTU-Summer 2012). Define Dry saturated steam. (GTU- Winter 2010) Define: enthalpy of superheated steam.(GTU-Winter 2010) 4.4 ************* ************ ******* *****" *****"******"*****''**************************************** UQ. 4-4 .. . ************************************************* 4-4 UQ. ******"'******"******"*******'*********** 4-5 UQ. ***.*.************* *********************************** 4-5 4.5 Steam Properties . ******************************"*********************************" Prove 4-5 that dryness fraction + wetness fraction = 1 (GTU- Summer 2009) What is dryness fraction ? (GTU-Winter 2009, 2011, Summer 2010, 2013) What do you mean by Dryness fraction? (GTU-Summer 2012) UQ. '********" ** 4-5 UQ. 4-5 UQ. ***************************************************** Express the mathematical formula with standard notation/symbol of properties for 1. Wetness fraction of steam (GTU-Winter 2016) Dryness fraction of steam cannot have the value more than unity: Justihy. (GTU-Winter 2018) Define: Sensible heat.(GTU- Winter 2011, Summer 2013) UQ. 45 UQ. UQ. Define: Latent Heat, Degree of superheat, Enthalpy of evaporation. GTU Summer 2011, 2013, Winter 2011) Define: Latent Heat. (GTU-Winter 2017) Define: Heat of superheat (GTU-Winter 2011, 2017) UQ. ****************i******'******** 4-5 4-5 UQ. ********************************* ************* 4-6 UQ ***** UQ. Express the mathematical formula with standard notationsymbol of properties for 1. Enthalpy of superheated steam (GTU Winter 2010, 2016) Define the following terms: Degree of superheat. (GTU-Summer 2010, 2011, 2012, Winter 2017) 6 Define the following term: critical point and triple point of water (GTU Summer 2015, Winter 2017).46 ****************************tetes*******r**r**l UQ. UQ. 4-7 4.6 Specific Volume of Steam. **********************tht'*****sa*e***t*et************************al Ua. xpress the mathematical formula with standard notation/symbol of properties for Specific volume of wet steam. (GTU Winter 2016) *********ehsen************* ******ss4-7 d***rasnsn****ttk******
(Properties of Steam)...Page no. (4-22) Basic Mechanical Engineering .4-7 (GTU-FY-Common) .4-8 4.7 External Work of Evaporation.. ** 8 Internal Energy of Steam. * * * ''*'''**'***'**''''**''*'***'**''**'*****'**'**** ** ********** * * '''''***'*''*'"****** 4.10 Steam Tables. 4.8 Internal Latent Heat.. 8 4.9 4-8 * *'******'***'''**''**'*'***'''*''''''* ''****'"*****''****'*''''**** . Write the uses of "Steam Tables". (GTU Winter 2016).. Ua. 4-9 4.11 Hints to solve the Problems.. . 4-9 '********''*'**** **'****'*****''''*''''' ''******** * .. 4.11.1 Solved Examples on Wet, Dry and Superheated Steam. SOLVED UNIVERSITY EXAMPLES UEx. 4.11.1 (GTU Winter 2015).. *'*******' ** *** * * ****'*******''''**''''**''''' ""'"'''**'''''''*** iis UEx. 4.11.2 (GTU Summer 2010, 2013, Winter 2008, 2013, 2019).. UEx. 4.11.3 (GTU -Summer 2012, 2015, 2016, Winter 2010). ****'*****'****'****'''*''''*'''''*''''''"''''''***''''' '**' ** 4-10 UEx. 4.11.4 (GTU - Winter 2012).. *''** * *'** '***'**'*'******'**'************'*'*'''''*'*'**'''''**''''*''''''''''*'* ******** UEx. 4.11.5 (GTU - Winter 2017).. ****'***** ** ***'****'********************'****''******'***'''''''**'''******** ******.. 4-9 *******************'**************** * .4-9 . 4-10 , 4-11 4-11 UEx. 4.11.7 (GTU Summer 2014, Winter 2014, 2018). UEx. 4.11.11 (GTU - Winter 2016) .. '**"'**'''''''*''''**'''*''*°''*'''''***° ''''** '***''°''''''' '*'''"'''''''*'**'''**** UEx. 4.11.12 (GTU Winter 2011). UEx. 4.11.13 (GTU Summer 2019). UEx. 4.11.14 (GTU Summer 2019) 4-14 .4-14 "************"*****'""*'*'*'*'*'''*''''***'°**°''"***'"*'''°**''*'*'''"**'*'*** ******'******* .4-14 4-15 4-15 4.12 Throttling process.. UQ. What is throttling process? (GTU-Winter 2013) ******'*****''"""*** '***''''°' **'"'*''''**'''*************** **** a 4-15 T 4.13 Measurement of Dryness Fraction. 4.13.1 Barrel Calorimeter.. ** *******************'*** ******* ** **'**** ********s****** '***********"*********** Explain Barrel calorimeter with neat sketch. (GTU- Winter 2014) 4.13.2 Separating Calorimeter. List methods of measuring dryness fraction. Explain any one of them. (GTU-Summer 2015) 4.13.3 Throtting Calorimeter ... 4-16 4-16 UQ. 4-16 .4-17 UQ. ********'""'' 4-17 4-17 Explain throtting calorimeter GTU- Winter 2009). Explain Separating Calorimeter with neat sketch. (GTU- Summer 2013). UQ. 4-17 UQ. 4-17 UQ. Explain throtting calorimeter with neat sketch. Derive equation for dryness fraction. GTU-Winter 2013,2015. Write a short note on Separating calorimeter with its limitations. (GTU Summer 2014, Winter 2018).417 4-17 UQ. 4.13.4 Combined Separating and Throttling Calorimeter .. Describe Combined calorimeter witha neat sketch. (GTU- Summer 2012)... 4-188 UQ. 4-18 UQ. With a neat sketch explain structure and working of combined separating and and derive throttling calorimeter the suitable equation for finding the dryness fraction of steam. GTU-Winter 2017, Summer 2018) ** ********' '************ **** 4.13.5 Solved Examples on Steam ** "**'"** Calorimeter... 4-18 SOLVED UNIVERSITY EXAMPLES UEx. 4.13.4 (GTU Winter 2008). UEx. 4.13.5 (GTU - Winter 2009). Chapter Ends... *********pss******************************************************************************a************o****n. 4-19 .. 4-20 4-20 **a*a****aansn 4-21 (New Syllabus w.e.f academic year 18-19) (G12-06) ATech-Neo Publications...A SACHIN SHAH Venture
Basic Mechanical Engineering (GTU-FY-Common) (Properties of Steam)...Page no. (4-3) M4.1 NTRODUCTION Water at boiling temperature t,'C Cylinder Water A pure substance is defined as a homogenous substance which retains its chemical composition even though it undergoes a change in phase during a thermodynamic at 0'C Pistion W process. Water is one of tlhe pure substances which can exist in the three different phases i.e. in the solid phase as ice, in the liquid phase as water and in the gascous phase as steam. In all its three different phases. it retains the same chemical Water Hoat Heat (a) b) composition. Steam is the technical term for water vapour, the gascous phase of water, which is formed when water boils. Steam is used as the working substance in the operation of steam engines and steam turbines. Steam does not obey the laws of perfect gases until it is perfectly dry. When the dry steam is further heated so that it becomes superheated steam, it behaves like a perfect gas. Saturated liquid+Water vapour at'C Dry steam at t,'C W Vapour Vapour Water 4.2 DIFFERENCE BETWEEN GAS AND Heat Heat VAPOUR (c) (d) Superheated steam at t,'C Gas Vapour It is the state of substance It is the gaseous state of a in which the evaporation fluid from the liquid state is mixture of minute liquid complete. and consists of Vsup particles in suspension. With changes With changes Heat in In Lemperature and pressure, temperature and pressure, gas remains in its gaseous vapour undergoes change of state, except under extreme phase and readily undergoes conditions of temperature condensation and pressure. (e) (101)Fig. 4.3.1 : Formation of steam at constant pressure Critical point evaporation. Generally Water gas obeys gas Vapour do not obey gas laws region laws 4. nitrogen, Water, hydrogen etc. are examples ammonia etc. are examples of vapour. Air, 0xygen, mercury, Freon, P Superheated region of gas. sup 4.3 FORMATION OF STEAM AT cONSTANT PRESSURE Water-steam region rr--rme rraorrrru---. Ua. Explain water Temperature- Enthalpy Diagram for Enthalpy GTU-Summer 2015) Latent heat of water. evaporauon, n fg UQ Enthalpy of Superheat Sesible heat, h, Define the terms 1. Melting point 2, Boiling point 3. Critical point. UQ GTU- Summer 2017) (102)1 ig. 4.3.2: Temperature-enthalpy (t-h) diagram Explain steam formation with figure also draw T-H diagram. Considerl kg of water at O°C tiaken in the piston-cylinder arrangeent. Weight W is plawed on the piston as shown in Fig. 4.3.1. GTU-Summer 2017, Winter 2018) -** (New Syllabus w.e.f academic year 18-19) (G12-06) Tech-Neo Publications...A SACHIN SHAH Venture
(Properties of Steam).Page no. (4-4) Basic Mechanical Engineering (GTU-FY-Common) The piston and weights maintain constant pressure in the cylinder, When water is heated at constant pressure it is converted to stcam. Let v be the volume occupied by the water in the eylinder. The condition of water at O°C is represented by pwint A on temperatue - enthalpy (t-h) diagram as shown in Fig. 4.3.2. 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 is called enthalpy of super heat or amount of superheat. The difference between superheated temperature and saturation temperature of steam at a given pressure is known The various states involved in the process are discussed n below is degree of superheat. 1 When the water is hcated. the volume of water increases and '. Degree of superheat = sup-t) causes the piston to move slightly upwards. On further heating. temperature reaches the boiling point. The boiling point of water at normal atmospheric pressure of 1.01325 bar is 100 °C. but it increases with inerease in pressure. The 5. If the pressure is increased from p to P 5aturation temperature also increases. The line passing through the points A. B, E and H is known as liquid line which forms the boundary line between water and steam. Similarly, line passing through I, F and C is known as dry saturated steam temperature at which water starts boiling is known as saturation temperature and is denoted by t. The heating of water from 0°C to the saturation temperature is shown by inclined line AB on temperature-enthalpy diagram. line which forms the boundary line between wet steam and superheated steam. When the boiling point is reached, there is slight increase in volume of water as shown by vr in Fig. 4.3.1(b). The amount With the increase of pressure. saturation temperature increases, the latent heat of evaporation decreases. It becomes of heat required to raise the temperature of 1 kg of water from 0°C to the saturation temperature (1, °C) at constant pressure zero at point K where the liquid line and saturation steam line meet. Point K is known as critical point and at this point the is known as sensible heat and is denoted by hr. It is also called enthalpy of the water. saturated liquid state and saturated vapour state become identical. The temperature and pressure corresponding critical point are known as critical temperature and critical If is heating of water is continued, there will be no further rise in temperature of water but evaporation of water takes place at saturation temperature as the water will be saturated with heat and any further addition of heat only changes the phase from liquid phase to gaseous phase. At this stage, water exists as two phase mixture of saturated liquid and vapour pressure respecti vely. For steam., the critical temperature (t) is 374.15 °C and critical pressure is 221.2 bar. 4.4 TYPES OF STEAM Occupying volume Vig as shown in Fig. 4.3.1(c). The steam in this condition is called wet steam. Evaporation of water continues at the same saturation temperature until the whole of the water is completely converted to steam. This constant pressure and constant temperature heat addition process is shown by line BC on t-h diagram. The steam generated by heating of water existsin three different states namely wet steam, dry steam and superheated steam. 1. Wet steam --- At point C. steam formed does not contain any water particles in suspension. The steam formed in this state is called dry steam or dry saturated steam. The volume occupied by the dry steam is v, as shown in Fig. 4.3.1(d). UQ. Define: Wet steam. (GTU Summer 2012); ------ - - - - - -- --- - - --*** Definition : When the steam contains water particiès Suspension formed at the saturation temperature and at a giveu The amount of heat required to evaporate T kg of water at the saturation temperature (t) into 1 kg of dry steam at the same temperature (t) and pressure is called latent heat of evaporation or hidden heat or enthalpy of evaporation and is denoted by hre pressure, it is called wet steam. n wet steam, the evaporation of water is not complele d whole of the latent heat is not absorbed. 2. Dry saturated steam **** - - 4. If the heating of dry steam is continued at constant pressure, UQ. Define Dry saturated steam. (GTU Winter 2010) the temperature increases above the saturation temperature. The temperature of steam above the saturation temperature at a given pressure is called superheated temperature and the process of heating the dry steam above its saturation temperature is called superheating shown by inclined line CD on t-h diagram and steam in this condition is called superheated steam. The volume occupied by superheated steam (Vsup) is shown in Fig. 4.3.1(e). ---- Definition: When the wet stean is further heated and it doe not contain any suspended water particles and its temperature 1S equal to saturation temperature at a given pressure, the s is known as dry saturated stean or dry steam. In dry steam, the evaporation of water is complete as the whole of the latent heat is absorbed. (New Sylabus w.e.f academic year 18-19) (G12-06) Tech-Neo Publications...A SACHIN SHAH Vent hture