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RMK College of Engineering & Technology DEPARTMENT OF MECHANICAL ENGINEERING
UNIVERSITY QUESTIONS ME 6301- Engineering Thermodynamics
Compiled by Dr.P.K.Devan Professor, Mech. Engg
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UNIT-I Short Questions
1. State the the First law law for a closed system undergoin undergoing g a change change of state. state. 2. What are point functions functions and path functio functions ns and give examples examples for for each? each? 3. What What is meant meant by intern internal al energ energy? y? . ! rigid rigid tan" is insulate insulated d around around both its sides sides and ends. #t is separated separated initia initially lly into into two e$ual volumes by a partition. When one side contains 1 "g of gas at 1%% "&! and 3' o() the the othe otherr side side rema remain inss evac evacua uate ted. d. #f the the parti partiti tion on is remo removed ved)) find find press pressur uree and and temperature. '. *riefly *riefly expl explain ain +the +the conce concept pt of conti continuu nuum, m, -. What What is a & 1? Why Why is is it impossi impossible ble?? /. #S it correct correct to say 0total 0total heat heat or heat heat content content of a closed closed system system?? . efine 0process 0process and 0cycle 0cycle with one exampl examplee each. 4. isting istinguis uish h between between heat heat and and temper temperatu ature. re. 1%. efine5 efine5 6a7 system 6b7 (ycle (ycle 11. 11. !n insulated insulated rigid vessel is divided into two parts by a membrane. membrane. 8ne part of the vessel contains air at 1% &a and other part is fully evacuated. 9he membrane ruptures and the air fill the entire vessel. #s there any heat or wor" transfer during the process? :ustify your answer. 12. ;xplain mechanical) mechanical) chemical and thermal e$uilibrium. 13. Show that wor" is path function and not a property. property. 1. athematically state the steady flow energy e$uation and apply it to a condenser. condenser. 1'. &rove that an isolated system) system) there is no change in internal energy. energy. 1-. etermine etermine the molecular molecular volume of any perfect gas at -%% <=m 2 and 3%o(. >niversal gas constant may be ta"en as 32 :="g mole@. 1/. #ndicate the practical application of steady flow energy e$uation. e$uation. 1. What What is the relation relationshi ship p between between a system system and its environm environment ent when the system system is 6a7 !diabatic 6b7 #sothermal
14. What is meant meant by enthalpy? enthalpy? 2%. What What is heat? heat?
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21. &rove that c p Acv B C. 22. State Deroth law of thermodynamics. What is its application? 23. What is the convention for positive and negative wor"? 2. What are the corollaries to the first law of thermodynamics? 2'. istinguish between intensive and extensive properties by giving examples. 2-. educe an expression for the wor" done by a gas in a system during the reversible polytropic process. 2/. What is thermodynamic property? Eow are they classified? 2. #s it possible to compress an ideal gas isothermally in an adiabatic cylinder device? ;xplin. 24. efine thermodynamic system and surroundings. 3%. State Deroth law and First law of 9hermodynamics. Big Questions 1. ! piston and cylinder machines contains a fluid system which passes through a complete cycle of four processes. uring a cycle) the sum of all heat transfers is 1/% ":. 9he system completes 1%% cycles per min. (omplete the following table showing the method for each item and compute the net rate of wor" output in "W.
&rocess aAb bAc cAd dAa
6":=min7 % 21%%% 21%%
W 6":=min7 21/% %
; 6":=min7 3-%%%
2. !ir flows steadily at the rate of %.' "g=s through an air compressor) entering at / m=s velocity) 1%% "&a pressure and %.4' m 3="g volume and leaving at 'm=s) /%% "&! and %.14 m3="g. 9he internal energy of the air leaving is 4% ":="g greater than that of the air entering. (ooling water in the compressor Gac"ets absorbs heat from the air at the rate of ' "W. 6i7 (ompute the rate of shaft wor" input to the air in "W. 6ii7 Find the ratio of the inlet pipe diameter to outlet pipe diameter. 3. 6i7 educe the expression for the displacement wor" in an isothermal process. 6ii7 3 "g of nitrogen gas at - atm and 1-% o( is expanded adiabatically to double its volume then compressed at constant pressure to its initial volume and then compressed again at constant volume to its initial state. (alculate the net wor" done on the gas. raw the pAH diagram for the processes. Specific heat ratio of nitrogen is 1. . 6i7 escribe steady flow energy e$uation and deduce suitable expression for the expansion of gas in a gas turbine with suitable assumptions.
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6ii7 !ir expands by isentropic process through a noIIle from / "&a and 22% o ( to an exit pressure of 4 "&!. etermine the exit velocity and the mass flow rate) if the exit area is %.%%%- m 2.
'. !ir of mass %.' "g is compressed reversibly and adiabatically from % "&a) -% o ( to %. &a and is then expanded at constant pressure to the original volume. S"etch the process on pAv plane and determine the heat transfer and wor" transfer. For air assume CB%.2/":="g@ and c vB%./13 ":="g@. -. !ir at 1%1.32' "&a) 2% o( is ta"en into a gas turbine power plant at a velocity of 1% m=s through an opening of %.1' m 2 crosssectional area. 9he air is compressed) heated) expanded through a turbine and exhausted at %.1 &!) 1'% o( through an opening of %.1% m2 cross sectional area. 9he power output is 3/' "W. (alculate the net amount of heat added to the air in ":="g. !ssume the air obeys the law pvB%.2/6tJ2/37) Where p is the pressure in "&a) v is the specific volume in m 3="g) and t is in temperature in o(. 9a"e c pB 1.%%' ":="g.". /. ! closed system consists of 1 "g of air which is initially at 1.' bar and -/ o(. 9he volume doubles as the system undergoes a process according to the law &H 1.2B(. Find the wor" done) heat transfer and the change in entropy during this process. For air CB%.2/ ":="g.@ and KB1.. . 6i7 !pply the steady flow energy e$uation to a 9urbine and deduce an expression for wor". 6ii7 !n air compressor ta"es in air at 1%% "&!) 1/ o( and delivers it at 1 &a) -%% @ to a constant pressure cooler which it exits at 3%% @. a"ing suitable assumptions find the specific compressor wor" and specific heat transfer. For air CB%.2/ @:="g:@ and KB1. 4. 6i7 ! blower handles 1 "g=sec of air at 243 @ and consumes a power of 1' "W. 9he inlet and outlet velocities of air are 1%% m=sec and 1'% m=sec respectively. Find the exit air temperature) assuming adiabatic conditions. 9a"e c pB1.%%' ":="g@. 6ii7 ! room for four persons has two fans) each consuming %.1 "W power and three 1%% W lamps. Hentilation air at the rate of %.%222 "g=sec enters with an enthalpy of ":="g and leaves with an enthalpy of '4 ":="g.. #f each persons puts out heat at the rate of %.1/' ":=sec) determine the rate at which heat is to be removed by room cooler) si that a steady state is maintained in the room. 1%. 6i7 8ne litre of hydrogen at 2/3 @ is adiabatically compressed to one half of its initial volume. Find the change in temperature of the gas) if the ratio of two specific heats for hydrogen is 1.. 6ii7 9he velocity and enthalpy of fluid at the inlet of a certain noIIles are '% m=sec and 2%% ":="g respectively. 9he enthalpy at the exit of noIIle is 2-%% ":="g. 9he noIIle is horiIontal and insulated so that no heat transfer ta"es place from it. 6a7Find velocity of fluid at exit of the noIIle.6b7 ass flow rate) if the area at inlet of noIIle is %.%4 m2 and specific volume of the fluid is LLLLLLLLLLLLLL . 6c7 ;xit area of noIIle) if the specific volume at the exit of the noIIle is %.4' m 3="g. 11. 6i7 erive an expression for the wor" transfer in an isothermal process. 6ii7 #dentify any four reasons for irreversibility in a process 6iii7 ! wor" done by substance in a reversible non flow manner is in accordance with HB61'=&7 m3) where p is in bar. ;valuate the wor" done on or by the system as 3
pressure increases from 1% to 1%% bar. #ndicate whether it is compression process or expansion process. #f the change in internal energy is '%% ":) calculate the direction and magnitude of heat transfer. 12. 6i7 efine internal energy and prove that it is a point functions. 6ii7 ;stablish the relationship between the specific heat at constant pressure and specific heat at constant volume. 6iii7 #n a gas turbine installation) the gases enters the turbine at the rate of ' "g=sec with a velocity of '% m=sec and enthalpy of 4%% ":="g and leave the turbine with 1'% m=sec. and enthalpy of %% ":="g. 9he loss of heat from the gases to the surroundings is 2'":="g. !ssume CB%.2/ ":="g@) c pB1.%% ":="g@ and inlet conditions to be at 1%% "&! and 2/o (. etermine the diameter of the pipe. 13. 6i7 &rove that the change in entropy during a polytropic process is given by s 2s1Bcv6n "=n17 log 69 2=917. Where "ratio of specific heats and nindex of compression or expansion. 6ii7 ! closed system consists of 1 "g of air which is initially at 1.' bar and -/o(. 9he volume doubles as the system undergoes a process according to the law pH1.2Bconstant. Find the wor" transfer and change in entropy. 1. 6i7 educe an expression for the wor" done by a system during a polytropic process. 6ii7 !ir flows steadily at the rate of %.'"g=sec through an air compressor entering at / m=s velocity) 1%% "&a pressure and %.4' m 3="g specific volume and leaving at ' m=s) /%% "&a and %.14 m 3="g. 9he internal energy of air leaving is 4% ":="g greater than that of the air entering. (ooling water in the compressor Gac"ets absorbs heat at the rate of ' "W. (alculate the rate of shaft wor" input to the compressor. 1'. 6i7 From the first law and using the ideal gas property relations prove that &H K B constant represent the reversible adiabatic process. 6ii7 ! system receives 2%% ": of energy as heat at constant volume. 9hen it is cooled at constant pressure when '% ": of wor" as done on the system while it reGects /% ": of heat. Supposing the system is restored to the initial state by an adiabatic process) how much wor" will be done by the system. 1-. !ir in a closed vessel of fixed volume %.1'm 3 exerts a pressure of 12 bar at 2'% o(. #f the vessel is cooled so that the pressure falls to 3.' bar) determine the final temperature) heat transfer and change of entropy. 1/. ! gas flows steadily through a rotary compressor. 9he gas enters the compressor at a temperature of 1-o() a pressure of 1%% "&a and an enthalpy of 341.2 ":="g. 9he gas leaves the compressor at a temperature of 2'o() a pressure of %.- &a and an enthalpy of '3.'":="g. 9here is no heat transfer to or from the gas as it flows through the compressor. ;valuate the external wor" done per unit mass when the gas velocity at entry is %m=s and that at exit is 1-% m=s. 1. ! gas of mass 1.' "g undergoes a $uasistatic expansion which follows a relationship &BaJbH) where 0a and 0b are constants. 9he initial and final pressures are 1%%% "&a and 2%% "&a respectively and the corresponding volumes are %.2% m 3 and 1.2 m 3. 9he specific internal energy of the gas is given by the relation uB1.'&v M ' ":="g where & is in "&a and v is in m 3="g. (alculate the net heat transfer and the maximum internal energy of the gas attained during expansion.
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14. ! room for four persons has two fans) each consuming %.1 "W power and three 1%% W lamps. Hentilation air at the rate of % "g=hr enters with an enthalpy of ":="g and leaves with enthalpy of '4 ":="g.. #f each persons puts out heat at the rate of -3% ":=h) determine the rate at which heat is to be removed by room cooler) si that a steady state is maintained in the room. 2%. ! mass of air is initially at 2-% o( and /%% "&a and occupies %.%2 m 3. 9he air is expanded at constant pressure to %.% m 3. ! polytropic process with nB1.' is then carried out) followed by a constant temperature process. !ll the processes are reversible. a. S"etch the cycle in the pAv and 9AS planes b. Find the heat received and heat reGected in the cycle. c. Find the efficiency of the cycle. 21. !ir at a temperature of 1'o( passes through a heat exchanger at a velocity of 3% m=s where its temperature is raised to %% o(. #t then enters a turbine with the same velocity of 3% m=s and expands until the temperature falls to -'% o(. 8n leaving the turbine) the air is ta"en at a velocity of -% m=s to a noIIle where it expands until the temperature has fallen to '%%o(. #f the air flow rate is 2 "g=s) calculate a. 9he rate of heat transfer to the air in the heat exchanger b. 9he power output from the turbine assuming no heat loss and . c. 9he velocity at exit from the noIIle) assuming no heat loss. 9a"e the enthalpy of air as hBc pt) where c p is the specific heat e$ual to 1.%%' ":="g@ and +t, the temperature. 22. 6i7 ' "g of air expands in to isothermally from 1m 3 to '.% m 3. !ssuming air to be an ideal gas with constant specific heats) compute the change in entropy of air during the process. 6ii7 What are the limitations of the First law of thermodynamics as applied to various thermal systems. 23. Steam flows steadily through a turbine with a mass flow rate of 3 "g=s. 9he steam is at /% bar and '%%o( while entering the turbine and at %.2 bar on leaving the turbine. 9he expansion process may be considered as isentropic. etermine the turbine output power. 2. 6i7 erive the general energy e$uation for a steady flow system and apply the e$uation to a noIIle and derive an e$uation for velocity at exit. 6iii7 #n an air compressor ) air flows steadily at the rate of %.' "g=sec. !t entry to the compressor) air has a pressure of 1%' "&a and specific volume of %.- m 3="g and at exit those corresponding values are /%' "&a and %.1- m 3="g.
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UNIT-II Short Questions
1. Why the second law of thermodynamics is called a directional law of nature? 2. 9he coefficient of performance of a heat pump is '. Find the (8& of refrigerator if both are reversible devices interacting between same source temperature and sin" temperature. 3. What do you understand by the concept of entropy? . What is loss of availability? Eow is related to entropy of universe? '. What is & ##? -. ention any four factors which render processes irreversible. /. 1 "g water boils melt at constant atmospheric pressure and at 1%% o( to form li$uid water. #f the latent heat of vaporisation of water is 22' ":="g) calculate the entropy change during this process. . What do you understand by a reversible process? 4. What are the two maGor conclusions deduced from the (arnot principle. 1%. What are the limitations of first law of thermodynamics? 11. State the @elvin&lan" and (lausius statements. 12. Write the necessary conditions for reversible process. 13. ! reversible heat engine operates between a source at %%o( and a sin" at 3% o(. What is the least rate of reGection per "W networ" out put of the engine? 1. 1 "g of ice melts at constant atmospheric pressure and at % o( to form li$uid water. #f the latent heat of fusion of ice is 333.3 ":="g) calculate the entropy change in this process. 1'. ;xplain the terms source and sin". 1-. What do you understand by the entropy principle? 1/. State the second law of thermodynamics. !lso write its physical significance. 1. ! domestic food freeIer maintains a temperature of 1' o(. 9he ambient air is at 3% o(. #f heat lea"s into the freeIer at a continuous rate of 1./'":=sec) what is the least power necessary to pump this heat out continuously?
14. #n some refrigerator systems) approximately the power re$uirement is 1 "W for every ton of refrigeration. Find the (8& achieved.
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2%. State the (lausius statement of second law of thermodynamics. 21. State few example of irreversible process. 22. educe the relationship between the (8& of heat pump and refrigerator. 23. What is meant by thermodynamic temperature scale? Eow do you device such scale? 2. What is the process involved in a (arnot cycle) s"etch the same in &H and 9S diagram. BIG QUESTIONS 1. 6i7 Oive the (lausius statement of second law. 6ii7 ! house hold refrigerator is maintained at a temperature of 2/' @. ;very time the door is opened) warm material is placed in side) introducing an average of 2% ":) but ma"ing only a small change in the temperature of the refrigerator. 9he door is opened 2% times a day and the refrigerator operates at 1'P of the ideal (8&. 9he cost of wor" is Cs 2.'% per "Whr. What is the bill for the month of !pril for this refrigerator? 9he atmosphere is at 3%3 @.
2. 6i7 What is a thermal energy reservoir? 6ii7 ;stablish the ine$uality of (lausius. 3. 6i7 State (arnot theorem. 6ii7 !n inventor claims to have developed an engine which receives 1%%% ": at a temperature of 1-% o(. #t reGects heat at a temperature of 'o( and delivers %.12 "Wh of mechanical wor". #s this a valid claim? :ustify your answer through (lausius ine$uality. 6iii7 ! refrigerator operating between two identical bodies cool one of the bodies to a temperature 91. #nitially both the bodies are at temperature 9 1. educe the expression for the minimum specific wor" input) ta"ing their specific heat as c. . 6i7 educe the expression for the entropy change in terms of pressure and temperature. 6ii7 8ne "g of ice at 1% o( is allowed to melt in atmosphere at 3% o(. 9he ice melts and the water so formed rises in temperature to that of atmosphere. etermine the entropy change of universe and write your comment based on principle of increase in entropy. 9he specific heat of ice is 2 ":="g@ and its latent heat is 33' ":="g. '. 9wo (arnot engines ! and * are operated in series. 9he first one receives heat at /% @ reGects to the reservoir at temperature +9,. 9he second engines receives the heat reGected by the first engine and inturn to the reservoir at 3%% @. (alculate the temperature in o( for the following cases. 6i7 Wor" output of the engine is e$ual 6ii7 9he efficiency of the two engines is e$ual. -. ! (arnot engine operates between source temperature 91 and sin" temperature 9 2. #t is decided to increase the efficiency by either increasing the source temperature or decreasing the sin" temperatures by the finite amount. ;stablish which is more effective. /. 6i7 State and prove (arnot theorem. 6ii7 ! reversible power cycle is used to drive a reversible heat pump cycle. 9he power cycle ta"es in 1 heat unit at 91 and reGects 2 at 92. 9he heat pump abstracts from the sin" at 9 and discharges 3 at 93. evelop an expression for the ratio 3=1 in 8
terms of the four temperatures. What must be the relationship of the temperatures for 3=1 to exceed a value of unity? . 6i7 What are the conditions for reversibility? ;xplain. 6ii7 ! heat exchanger circulates '%%% "g=hr of water to cool oil from 1'% o( to '%o(. 9he rate of flow of oil is 2'%% "g=hr. 9he average specific heat of oil is 2.' ":=@g@. 9he water enters the heat exchanger at 21o(. etermine the net change in entropy due to heat exchange process and the amount of wor" obtained if cooling of oil is done by using the heat to run a (arnot engine with sin" temperature of 21 o(. 4. 6i7 educe (lausius ine$uality and interpret it. 6ii7 !n ideal gas of %.12 m 3 is allowed to expand isentropically from 3%% "&a and 12% o( to 1%% "&a. ' ": of heat is then transferred to the gas at constant pressure. (alculate the change in entropy for each process. !ssume KB1. and c pB1.%%3' ":="g@. #f these two processes are replaced by a reversible polytropic expansion) find the index of expansion between original and final states. What will be the total changes in entropy? 1%. ! gas is flowing through a pipe at the rate of 2 "g=s. *ecause of inade$uate insulation the gas temperature decreases from %% to /4%o( between two sections in the pipe.
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UNIT-III Short Questions
1. #f water is at -'o( at 1 atm.) what is the state of water? What is its specific enthalpy? 2. &lot the standard Can"ine cycle on 9s diagram and label all the processes assuming the steam to be dry and saturated at the end of expansion. 3. efine saturation state of steam. . Why (arnot cycle is not practicable for steam power plant? '. efine triple point and identify the triple point of water. -. Steam in pipe line with a pressure with pressure of 1%%% "&a flows through a throttling calorimeter where pressure is 1%% "&a and temperature is 12% o(. What is the initial $uality of steam if enthalpy remains constant during throttling? /. efine the term $uality and give expressions to determine the entropy of wet steam of given $uality x) in terms of entropy of standard li$uid and dry saturated vapour. . What is a pure substance? Oive examples. 4. Eow evaporation differ from boiling?
1%. What do you understand by pure substance? Oive some typical example. 11. What is critical point? What are the properties of water at critical point? 12. efine critical pressure and temperature for water. 13. S"etch the Can"ine cycle on a pH plane and name the various processes. 1. etermine whether water at the following states is a compressed li$uid) a superheated vapour or a mixture of saturated watersteam5 6a7 1 &a) %.%%3 m 3="g 6b7 13% o() 2%% "&a.
Big Questions
1. 3 "g of steam at 1 bar occupy a volume of %.2''% m 3. uring a constant volume process) the heat reGected is 132% ":. etermine final internal energy. Find dryness fraction and pressure) change in entropy and wor" done. 2. 6i7 *riefly explain the process of super heated steam formation with the help of 9s diagram. 6ii7 ! steam power plant runs on a single regenerative heating process. 9he steam enters the turbine at 3% bar and %% o( and steam fraction is withdrawn at ' bar. 9he remaining steam exhausts at %.1% bar to the condenser. (alculate the efficiency) steam fraction and steam rate of the power plant.
3. ! cyclic steam power plant is to be designed for a steam temperature at turbine inlet of -33 @ and an exhaust pressure of "&a. !fter isentropic expansion of steam in the turbine) the moisture content at the turbine exhaust is not to exceed 1'P. etermine the greatest allowable steam pressure at the turbine inlet and calculate the Can"ine cycle efficiency for these steam conditions. ;stimate also the mean temperature of heat addition. . #n a reheat steam cycle) the maximum steam temperature is limited to //3 @. 9he condenser pressure is 1% "&a and the $uality at turbine exhaust is %.//. Ead there been no reheat ) the exhaust $uality would have been %./'42. !ssuming ideal processes) determine 6i7 reheat pressure 6ii7 the boiler pressure 6iii7 the cycle efficiency 6iv7 the steam rate.
'. 6i7 raw p9 diagram and label various phases and transitions. ;xplain the process of sobaric heating above triple point pressure with the help of p9 diagram. 6ii7 2 "g of water at 2%% o( are contained in a 2%m 3 vessel. etermine the pressure) nthalpy) mass and volume of vapour within the vessel. -. raw Can"ine cycle with one open type feed water heater. !ssume the condition of the steam before entering the turbine to be superheated. S"etch the cycle on 9s diagram. 6i7 #n an ideal reheat cycle) the steam enters the turbine at 3% bar and '%% o(. !fter expansion to ' bar) the steam is reheated to '%% o( and then expanded to the condenser pressure of %.1 bar. etrmine the cycle thermal efficiency and mass rate of steam. 9a"e power output as 1%% W. /. 6i7 ! vessel having a volume of ' m 3 contains %.%' m 3 of saturated li$uid water and .4' m3 of saturated water vapour at %.1 &a. Eeat is transferred until the vessel is filled with saturated vapour. etermine the heat transfer) wor" done and change in entropy for the process. 6ii7 ;xplain with neat s"etch the construction of the ollier diagram and give its use in thermodynamic representation. . etermine the volume change when 1 "g of saturated water is completely vaporised at a pressure of 6i7 1 @&a 6ii7 1%% "&a and 6iii7 1%)%%% "&a 4. Steam at / bar and %.4 dryness fraction expands isothermally to 1. bar. (alculate the change in internal energy and enthalpy using steam tables. 1%. ;stimate the $uantity of heat re$uired to produce ' "g of steam at - bar from water at %o() when the steam is %P dry and when it is at 3%% o(. 9a"e c p of superheated steam as 2.3 ":="g@. 11. Steam at 2% bar) with a degree of superheat of % o( is supplied by a boiler at 1.' "g=sec to a turbine. #t is expanded isentropically to %.%/ bar. etermine the $uality of steam after expansion) heat supplied in the boiler in "W) heat reGected in the condenser in "W) power generated and thermal efficiency neglecting pump wor". 12. #n a single heater regenerative cycle the steam enters the turbine at 3% bar) %%o( and the exhaust pressure is %.1% bar. 9he feed water heater is a directcontact type which operates at ' bar. Find 6i7 the efficiency and the steam rate of the cycle and 6ii7 the increase in 13
mean temperature of heat addition) efficiency and steam rate as compared to the Can"ine cycle 6 with out regeneration 7
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UNIT-IV Short Questions
1. What do you mean by e$uation of state? 2. State the altons law of partial pressure. 3. Eave you encountered any ideal gas? #f so) where? . What is coefficient of expansion? '. What is e$uation of state? Write the same for an ideal gas. -. What is the significance of compressibility factor? /. What are reduced properties? Oive their significance. . efine :oule9homson coefficient. 4. S"etch a s"eleton compressibility chart and show the constant reduced temperature characteristics on it. 1%. Eow does the Han der Waals e$uation differ from the ideal gas e$uation of state? 11. educe the expression for the gas constant of the mixture of two non reacting ideal gases ! and *. 12. ;xplain the construction and give the use of generalised compressibility chart. 13. What are the uni$ue features of Hader Waals e$uation of state? 1. What is compressibility factor? What does it signify? What is its value for Hander Waals gas at critical point? 1'. State the !vagodros law and state its significance. 1-. Write the axwells e$uations and its significance. 1/. ! system contains air in the form of li$uidvapour mixture in e$uilibrium. (an this mixture be treated as pure substance? :ustify your answer. Big Questions 1. 6i7 ! certain gas has c pB %.413 and c vB%.-'3 ":="g@. Find the molecular weight and the gas constant C of the gas. 6ii7 erive the (lausius (lapreyon e$uation.
2. 6i7 erive axwells e$uations. 6ii7 &rove 9 ds B cv d9 J 9 6Rp=R97 v dH 3. 6i7 &rove that the total pressure is a sum of partial pressures.
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6ii7 ! closed vessel has a capacity of %.' m3. #t contains 2%P nitrogen and 2%P oxygen) -%P carbon dioxide by volume at 2% o ( and 1 &a. (alculate the molecular mass) gas constant) mass percentage and the mass of mixture. . 6i7 erive 9ds relations in terms of temperature pressure changes and temperature / volume changes. 6ii7 erive :oule @elvin effect with the help of 9p diagram. '. ;xplain the :oule 9homson effect with the help of 9p diagram and derive the expression for :oule 9homson coefficient. Show that the value of this coefficient for an ideal gas is Iero. -. 6i7 What are the difference between real and ideal gases? 6ii7 Write down the van der Waals e$uation of state for real gases and how is it obtained from ideal gas e$uation by incorporating real gas corrections? 6ii7 ! tan" contains %.2 m 3 of gas mixture composed of "g of nitrogen) 1 "g of oxygen and %.' "g of (8 2. #f the temperature is 2% o() determine the total pressure) gas constant and molecular mass of the mixture. /. (alculate the pressure of steam at temperature of '%%o( and a density of 2 "g=m 3 using 6i7 9he ideal gad e$uation 6ii7 9he Han der Waals e$uation 6iii7 9he compressibility factor and 6iv7 9he steam table . &rove that c pcv B 96RH=R97 p2 6R&=RH79. What are the facts one can infer from the above e$uation? 4. >sing axwell relations c pcv B 9HT 2=@ 9. 1%. ! mixture of ideal gas consist of 3 "g of < 2 and ' "g of (8 2 at a pressure of 3%% "&a and a temperature of 2%o(. Find 6i7 9he mole fraction of each constituent 6ii7 9he e$uivalent molecular weight of the mixture 6iii7 9he e$uivalent gas constant of the mixture 6iv7 9he partial pressures and the partial volumes. 11. &rove that c p of ideal gas is a function of temperature only. 12. ! mixture of 2 "g of oxygen and 2 "g !rgon is in an insulated piston cylinder arrangement at 1%% "&a) 3%% @. 9he piston now compresses the mixture to half its initial volume. Find the final pressure) temperature and piston wor". olecular weight of oxygen is 32 and for !rgon is %. Catio of specific heats for oxygen is 1.34 and for !rgon is 1.--/.
13. educe the axwells relations and from the third relation deduce the (lausius (lapeyron e$uation. !lso apply this e$uation to the vaporisation process for pure substance. 1. ;ntropy is a function of any two properties li"e p and H) & and 9 etc. For pure substance with the help of axwells e$uation) &rove 16
6i7 6ii7 6iii7
9dsBcvd9 J
[email protected] 9dsBc pd9H.T.dp.9 9dsBU@cv=TV.dp J Uc p=vTV.dv
1'. etermine change of internal energy and change of entropy when the gas obeys Hander Waals e$uation. 1-. %.' "g of (8 and 1 "g of air is contained in a vessel of volume %. m 3 at 1'o(. !ir has 23P of 82 and /-./P of < 2 by mass. (alculate the partial pressure of each constituent and total pressure in the vessel. olar masses of (8)82 and <2 are 2)32 and 2 "g=" mol. 1/. ;xplain the flow process of ideal gas through throttle valve. erive the expression for :oule 9homson coefficient and deduce its value for an ideal gas. 1. erive 9ds e$uation when 6i7 9 and H independent 6ii7 9 and & independent 6iii7 & and H independent. 14. ! mixture of ideal gases consist of 3 "g of < 2 and ' "g of (8 2 at a pressure of 3%% "&a and at 2%o(. Find 6i7 the mole fraction of each constituent) 6ii7 e$uivalent molecular weight of the mixture 6iii7 e$uivalent gas constant of the mixture 6iv7 the partial pressures and partial volume 6v7 volume and density of the mixture and 6vi7 c p and c v of the mixture. !ssume the value of c p=cv for (82B1.2- and for < 2B1..
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UNIT-V Short Questions
1. What is specific humidity and how do you calculate it? 2. What is meant by adiabatic saturation temperature? 3. efine specific humidity. . efine dew point temperature '. What is sensible heating? -. #f the relative humidity of air is -%P at 3%o() what is the partial pressure of water vapour? /. What is thermodynamic wet bulb temperature? . What is dew point temperature? Eow is it related to dry bulb and wet bulb temperature at the saturation condition? 4. What is adiabatic mixing and write the e$uation for that? Big Questions 1. 6i7 raw the psychrometric chart and show any two psychrometric processes on it. 6ii7 ! sample of moist air at 1 atm. and 2' o( has a moisture content of %.%1P by volume. etermine the humidity ratio) the partial pressure of water vapour) the degree of saturation) the relative humidity and the dew point temperature.
2. 6i7 escribe the process of adiabatic mixing of two streams and deduce the ratio of masses of two streams in terms of humidity and=or enthalpy. 6ii7 9he temperature of the windows in a house on a day in winter is ' o(. When the temperature in the room is 23 o( and the barometric pressure is /. cm Eg) what would be the maximum relative humidity that could be maintained in the room without condensation on the window panes? >nder these conditions) find the partial pressure of the water vapour and air) the specific humidity and the density of the mixture. 3. #n a laboratory test) a sling psychrometer recorded dry bulb and wet bulb temperatures as 3%3 @ and 24 @ respectively. (alculate 6i7 vapour pressure 6ii7 relative humidity 6iii7 specific humidity 6iv7 degree of saturation 6v7 dew point temperature 6vi7 enthalpy of the mixture. . 6i7 1 "g of air at 313 @ dry bulb temperature and '%P relative humidity is mixed with 2 "g of air at 243 @ dry bulb temperature and 243 @ dew point temperature. (alculate the temperature and specific humidity of the mixture. 6ii7 Show the following processes on a s"eleton psychrometric chart. 6a7 ehumidification and cooling 6b7 Eeating and dehumidification '. 6i7 escribe the adiabatic cooling process and deduce the expression for the enthalpy
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6ii7 !ir at 2%o() %P relative humidity is mixed adiabatically with air at % o() %P CE in the ratio of 1 "g of former with 2 "g of latter 6on dry basis7. Find the final condition 6humidity and enthalpy7 of air. -. 6i7 raw the cooling and dehumidification process and explain Sensible Eeat Factor 6SEF7) *ypass Factor and effectiveness of coil. 6ii7 ! stream of air at 1%1.32 "&a) 1 o( and relative humidity of 3%P is flowing at the rate of 1.1' m 3=min. ! second stream at 1%1.32 "&a) 3 o( and CE of '%P is flowing at the rate of .'m 3=min.. 9he two steams are mixed adiabatically to form a third stream at 1%1.32 "&a. etermine the specific humidity ) the relative humidity and the temperature of the third stream. /. !tmospheric air at 1.%132 bar has *9 of 32o( and a W*9 of 2- o(. (ompute5 6i7 9he partial pressure of water vapour 6ii7 9he specific humidity 6iii7 9he dew point temperature 6iv7 9he relative humidity 6v7 9he degree of saturation 6vi7 9he density of the vapour in the mixture 6vii7 9he enthalpy of mixture. . !n air Mwater vapour mixture at %.1 &!) 3% o() %P CE has a volume of '% m 3. (alculate the specific humidity) dew point) wet bulb temperature) mass of dry air and mass of water vapour. 4. 6i7 ;xplain the adiabatic saturation process using 9s diagram and derive an expression to determine the specific humidity of unsaturated air entering the adiabatic saturator. 6ii7 !ir at 2%o() %P relative humidity is mixed adiabatically with air at % o() %P CE in the ratio of 1 "g of former with 2 "g of latter 6on dry basis7. Find the final condition 6humidity and enthalpy7 of air. 1%. ;xplain in detail about the following. a. Sensible heating or cooling b. (ooling and dehumidification. c. Eeating and dehumidification. 11. 9he atmospheric air at 3%o( *9 and /%P CE enters a cooling coil at the rate of 2%% m3=min. 9he coil temperature is 1 o( and the bypass factor is %.1. etermine 6i7 9he temperature of air leaving the coil 6ii7 (apacity of the cooling coil in 9C 6iii7 9he amount of water vapour removed 6iv7 Sensible Eeat Factor for the process. 12. 9he volume flow rate of air is %% m 3=min of recirculated at 22 o( *9 and 1% o( dew point temperature is to be mixed with 3%% m 3=min of fresh air at 3% o( *9 and '%P CE. etermine the enthalpy) Specific volume) Eumidity ratio and dew point temperature of the mixture. 13. 6i7 ifferentiate between ry bulb temperature and wet bulb temperature Wet bulb temperature and wet bulb depression
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6ii7 !ir at 1-o( and 2'P CE passes through a heater and then through a humidifier to reach final dry bulb temperature of 3% o( and '%P CE. (alculate the heat and moisture added to the air. What is sensible heat factor? 1. 6i7 #n an adiabatic mixing of two streams) derive the relationship among the ratio of mass of streams) ratio of enthalpy change and ration of specific humidity change. 6ii7 Saturated air at 2%o( at a rate of 1.1-/ m 3min is mixed adiabatically with the outside air at 3'o( and '%P CE at a rate of %.' m 3=sec. !ssuming adiabatic mixing condition at 1 atm.) determine specific humidity) relative humidity) dry bulb temperature and volume flow rate of the mixture. 1'. ! room / m x m x m is occupied by an air water vapour mixture at 3 o(. 9he atmospheric pressure is 1 bar and the relative humidity is /%P. etermine humidity ratio) dew point temperature) mass of dry air and mass of water vapour. #f the mixture of air water vapour is further cooled at constant pressure until the temperature is 1% o(. Find the amount of water vapour condensed. 1-. !ir at 2%o() %P CE is mixed adiabatically with air at % o() %P CE in the ratio of 1 "g of the former with 2 "g of later. Find the final condition of air. raw the process in chart also as diagram. 1/. 6i7 #ndicate the application of psychrometry in industry 6ii7 9he air in a room has a pressure of 1 atmosphere) a dry bulb temperature of 2 o( and a wet bulb temperature of 1/ o(. (ompute the following5 i. 9he specific humidity ii. 9he dew point temperature iii. 9he relative humidity iv. 9he degree of saturation. **********
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