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    ENGINEERING THERMODYNAMICSUNIT I

    1. Define the term thermal engineering?Thermal engineering is the science that deals with the energy transfer to

    practical applications such as energy transfer, power generation,refrigeration, gas compression, and its effect on the properties of workingsubstance.

    2. What is meant by thermodynamic system? How do you classify it?Thermodynamic system is defined as the any space or matter or group ofmatter where the energy transfer or energy conversions are studied.

    It may be classified into three types.

    (a) Open system(b) Closed system

    (c) Isolated system.

    3. What is meant by closed system? Give an example.When a system has only heat and work transfer, but there is no masstransfer, it is called as closed system.

    Example: piston and cylinder arrangement.

    4. Define an open system. Give an example.When a system has heat, work, and mass transfer, it is called as opensystem.

    Example: Air compressor.

    5. Distinguish between open and closed system?

    Sl.No.

    Closed system Open system

    1. There is no mass transfer. Mass transfer will takes place.

    2. Only heat and work transfer. Heat and work transfer takesplace.

    3. System boundary is fixed one. System boundary may or may notchange.

    4. Ex: Piston & cylinderarrangement, Thermal powerplant.

    Air compressor, boiler.

    6. Define an isolated system?

    Isolated system is not affected by surroundings. There is no heat, workand mass transfer takes place. In this system, total energy remainsconstant.

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    7. What is boundary?

    System and surroundings are separated by an imaging line is calledboundary.

    8. What is meant by surroundings?

    Any other matter out side of the system boundary is called assurroundings

    9. Define specific heat capacity at constant pressure?

    It is defined as the amount of heat energy required to raising or loweringthe temperature of unit mass of the substance through one degree whenthe pressure is kept constant. It is denoted by Cp.

    10.Define specific heat capacity at constant volume?

    It is defined as the amount of heat energy required to raising or loweringthe temperature of unit mass of the substance one degree when volume iskept constant. It is denoted by Cv.

    11. What is meant by thermodynamic property?

    Thermodynamic property is any characteristic of a substance which isused to identify yhe state of the system and can be measured, when thesystem remains in an equilibrium state.

    12. What do you understand by equilibrium of a system?

    When a system remains in equilibrium state, it should not undergo anychanges on its own accord.

    13.Define intensive and extensive properties.

    The properties which are independent on the mass of the system is calledintensive properties.

    E.g Pressure, Temperature, Specific volume etc.

    The properties which are dependent on the mass of the system is calledextensive properties.

    E.g: Total energy, Total volume, weight etc.

    14. What is meant by Perpetual motion Machine of first kind?

    PMM of the first kind delivers work continuously without any input. Itviolates first law of thermodynamics. It is impossible to construct an

    engine working with this principle.

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    15.Prove that for an isolated system, there is no change in internalenergy.

    For any isolated system, there is no heat, work and mass transfer.

    Q=W=0

    According to the first law of thermodynamics.

    Q=W+U

    U=0

    16. Define the term process.

    It is defined as the change of state undergone by a gas due to energyflow.

    17. Define the term cycle.

    When a system undergoes a series of processes and return to its originalcondition, It is known as cycle.

    18. What is Quasi-static process?

    The process is said to be quasi-static, It should proceed infinitesimallyshow and follow continuous series of equilibrium states. Therefore, thequasi-static process may be a reversible process.

    19. Define the term internal energy.

    Internal energy of the gas is the energy stored in a gas due to itsmolecular interactions

    20. What is meant by thermodynamic work?

    It is the work done by the system when the energy transferred across theboundary of the system. It is mainly due to intensive property differencebetween the system and surrounding.

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    21. What is meant by point function?

    The quantity which is independent on the process or path followed by thesystem is known as point function.

    Example: Pressure, Volume, temperature etc.

    22. What is meant by path function?

    The quantity which is dependent on the process or path followed by thesystem is known as path function.

    Example: Heat transfer, Work transfer.

    23. Define the term enthalpy.

    The combination of internal energy and flow energy is known as enthalpyof the system

    24. Define zeroth law and first law of thermodynamics?

    Zeroth law of thermodynamics states that when two systems areseparately in thermal equilibrium with a third system, then theythemselves are in thermal equilibrium with each other.

    First law of thermodynamics states that when system undergoes a cyclicprocess, net heat transfer is equal to work transfer.

    25.Prove that for an isolated system, there is no change in internalenergy.

    For any isolated system, there is no heat, work and mass transfer.

    Q=W=0

    According to first law of thermodynamics,

    Q=W+U

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    U=0

    UNIT II

    1. State Kelvin plank statement of second law of thermodynamics.

    Kelvin plank states that it is impossible to construct a heat engineworking on cyclic process, whose only purpose is to convert all the heatenergy given to it in an equal amount of work.

    2. State clausius statement of second law of thermodynamics?

    It states that heat can flow from hot body to cold body without any

    external aid but heat cannot flow from cold body to hot body without anyexternal aid.

    3. State carnot theorem?

    No heat engine operating in a cyclic process between two-fixedtemperatures can be more efficient that a reversible engine operatingbetween the same temperature limits.

    4. Define PMM of second kind?

    Perpetual motion machine of second kind draws heat continuously fromsingle reservoir and converts it into equivalent amount of work, Thus itgives 100 percentage efficiency.

    5. What is the difference between a heat pump and refrigerator?

    Heat pump is a device which operating in a cyclic process maintains thetemperature of a hot body at a temperature higher that the temperature

    of surrounding.

    A refrigerator is a device which operating in a cyclic process, maintains thetemperature of a cold body at a temperature lower than the temperatureof the surrounding.

    6. What is meant by heat engine?

    A heat engine is a device, which is used to convert the thermal energy into

    mechanical energy.

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    7. Define the term COP?

    Coefficient of performance is defined as the ratio of heat extracted orrejected to work input.

    Heat extracted or rejected

    COP = work input

    8. Why a heat engine cannot have 100 efficiency?

    For all the heat engines there will be a heat loss between system andsurroundings. Therefore we cannot convert all the heat input into useful

    work.

    9. What are the process involved in carnot cycle?

    Carnot cycle consists of

    1. Reversible adiabatic compression.

    2. Reversible isothermal heat addition.

    3. Reversible adiabatic expansion.

    4. Reversible isothermal heat rejection.

    10. Define the term absolute entropy?

    The change in entropy of the system with respect to ambient conditions orany other standard reference condition is known as absolute entropy.

    11. Why carnot cycle cannot be realized in practice?

    (1). In a carnot cycle, all the four processes are reversible but in actualpractice there is no process is reversible.

    (2). There are two processes to be carried out during compression andexpansion. For isothermal process, the piston moves very slowly and foradiabatic process the piston moves as fast as possible. This speedvariation during the same stroke of the piston is not possible.

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    (3). It is not possible to avoid friction between moving parts completely.

    12.Name two alternative methods by which the efficiency of a carnotcycle can be increased?

    (1). Efficiency can be increased as the higher temperature T2 increases.

    (2). Efficiency can be increases as the lower temperature T1 decreases.

    13. Define the terms source, sink, and heat reservoir.

    Source:

    The part where the heat to be rejected to work absorbing or workdeveloping device is called source.

    Sink:

    The part which receives heat from work absorbing or workdeveloping device is called sink.

    Reservoir:

    The part which supplies or receives heat continuously withoutchange in its temperature is called as reservoir.

    14. Define entropy?

    Entropy is an index of unavailability or degradation of energy.

    15. Is the second law is independent of first law? Explain.

    Yes. The second law is independent of first law. The second law speaksabout the quality of energy.

    16. Define change of entropy. How is entropy compared withheat transfer and absolute temperature?

    The measure of irreversibility when the energy transfer takes place within

    the system or between the system and surrounding is called as change ofentropy. It is simply known as unaccounted heat loss.

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    17.Write the expression for efficiency of the carnot cycle?

    T2 T1

    carnot = T2

    T1 Lower temperature

    T2 Higher temperature

    18. What is the corollaries of carnot theorem?

    (1). All the reversible engines operating between the two given thermalreservoirs with fixed temperature have the same efficiency.

    (2). The efficiency of any reversible heat engine operating between tworeservoirs is independent of the nature of the working fluid and dependsonly on the temperature of the reservoir.

    19. What do you mean by clausius inequality?

    It is impossible for a self acting machine working in a cyclic processunaided by any external agency to convert heat from body at a lowertemperature to a body at a higher temperature.

    20. Can entropy of universe ever decrease ? why?

    Entropy of universe cannot ever decrease. It will be remain constant or willdecrease due to irreversibility.

    21. What is the essence of the second law of thermodynamics?

    (1). To know the feasibility of process.

    (2). To know about the quality of energy.

    22. Why the performances of refrigerator and heat pump aregiven in terms of C.O.P and not in terms of efficiency?

    The performance of any device is expressed in terms of efficiency for workdeveloping machines. But heat pump and refrigerator are work absorbingmachines. So, the performance of those devices based on C.O.P only.

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    23.Comment on the statement The entropy of universe tends to bemaximum?

    If the entropy of universe tends to be maximum, the irreversibility will bemore due to friction between moving parts.

    24. What is meant by principle of increase of entropy?

    For any infinitesimal process undergone by a system, change in entropy,dsdQ

    dT

    For reversible, dQ=0, hence, ds=0

    For irreversible, dS>0.

    So, the entropy of an isolated system would never decrease. It will alwaysincrease and remains constant if the process is reversible, is called asprinciple of increase of entropy.

    25. For compression process between same states, which willconsume more work reversible or irreversible.

    Irreversible work will be more in the compression process. Generally forcompression, the actual work given will be higher than the calculatedwork.

    UNIT III

    1. Define latent heat of ice?

    Total amount of heat added during conversion of ice of zero degree

    Celsius into water of zero degree Celsius.

    2. What is pure substance?

    Pure substance is a substance which has a fixed chemical compositionthroughout its mass. Examples:Water, nitrogen, carbon-di-oxide, andhelium. A pure substance does not have to be of a single chemicalelement or compound. A mixture of various chemical elements orcompounds is also called as pure substance as long as the mixture ishomogeneous.

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    3. What is saturation temperature and saturation pressure?

    At a given pressure, the temperature at which a liquid boils is calledsaturation temperature. At the given temperature, the pressure at whichthe liquid boils is called saturation pressure. It is also called as vapourpressure.

    4. Define latent heat of vaporization?

    The amount of heat added during heating of water from boiling point todry saturated stage is called as latent heat of vaporization or enthalpy ofvaporization or latent heat of steam.

    5. Define the terms boiling point and melting point

    Boiling point:

    It is the temperature at which the liquid starts to change itsstate from liquid to vapour.

    Melting point:

    It is the temperature at which the solid starts to change its

    state from solid to liquid.

    6. Define sensible heat of water?

    The amount of heat required to raise the temperature of unit mass ofwater from 0C to the saturation temperature under a constant pressure.It is denoted by hf.

    7. Define the term superheat enthalpy.

    The heat supplied to the dry steam at saturation temperature, to convertit into superheated steam at the temperature Tsup is called superheatenthalpy.

    8. Define wet steam and dry steam?

    The steam which partially evaporated and having water particles insuspension is called wet steam.

    The steam which fully in evaporated state and is not having any water

    particles is called dry steam.

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    9. What is meant by superheated steam? And indicate its use.

    If the dry steam is further heated, then the process is called superheatingand steam obtained is known as superheated steam.

    Uses:

    1. Superheated steam has more heat energy and more work can beobtained using it.

    2. Thermal efficiency increases as the temperature of superheatedsteam is high.

    10. Define triple point and critical point for pure substance?

    Triple point:

    Triple point is the state at where all the three phases that is,solid, liquid and vapour to exist in equilibrium.

    Critical point:

    It represents the highest pressure and temperature atwhich the liquid and vapour phases coexist in equilibrium. At the criticalpoint the liquid and vapour phases are indistinguishable that is liquid

    directly converted into vapour.

    11. Explain the terms: Degree of superheat, Degree ofsubcooling.

    Degree of superheat:

    It is the difference between superheatedtemperature and saturated temperature at the same pressure.

    Degree of subcooling:

    It is the amount by which the water is cooledbeyond the saturated temperature at the same pressure.

    12. State phase rule of pure substances?

    The number of independent variables associated with a multicomponent,multiphase system is given by the phase rule. It is also called as Gibbsphase rule.It is expressed by the equation as

    n=C- +2

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    Where,

    n = the number of independent variable,

    c = the number of components,

    = the number of phases present in equilibrium.

    13.When saturation pressure increases, what happens to saturationtemperature and freezing point?

    When saturation pressure increases, then the saturation temperature isincreasing and the freezing point decreasing.

    14. Determine the condition of steam of 2 bar whose entropy is

    6.27kJ/kg.

    From steam table at 2 bar Sg = 7.1268kJ/kg K

    Since entropy of given steam of pressure 2 bar is less than entropy of drysteam at that pressure, the steam is in wet condition.

    15. Determine the specific enthalpy and specific entropy of120C saturated steam?

    From steam table at 120C

    Specific enthalpy, hg = 2706kJ/kg

    Specific entropy, Sg = 7.1293kJ/kg K

    16. Determine whether water at the following states is a

    compressed liquid, a superheated vapour or a mixture ofsaturated water steam. (a) 18 Mpa, 0.003m/kg (b) 130C,200kpa.

    Case(a)

    P = 18 Mpa

    V = 0.003m/kg

    From steam table, corresponding to 18 Mpa, read

    Vg = 0.007497m/kg

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    Since v< vg, the steam is in wet condition that is mixture of liquid andsteam.

    Case (b)

    T = 130C

    P = 200Kpa

    From steam table, corresponding to 200kpa, read

    Tsat = 120.2C

    Since T

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    (i) Isothermal heat transfer (evaporation and condensation) is possiblein practice.

    (ii) The work ratio is high compared to the gas power cycles.

    21.Mention the improvements made to increase the ideal efficiencyof ranking cycle.

    1. Lowering the condenser pressure

    2. Super heated steam is supplied to the turbine.

    3. Increase the boiler pressure to certain limit.

    4. Implementing reheat and regeneration in the cycle.

    22. Name the different components in steam power plant

    working on a rankine cycle.

    Boiler, Turbine, Cooling Tower or Condenser, and Pump.

    23. What are disadvantages of reheating?

    The cost of plant increases due to the reheater and its long connections. Italso increases the condenser capacity due to increased dryness fraction.

    24. List the advantages of reheat cycle.

    1. Marginal increase in thermal efficiency.

    2. Increase in work done per kg of steam which results in reduced size ofboiler and auxiliaries for the same output.

    3. We can prevent the turbine from erosion.

    25. What are the disadvantages of bleeding?

    Cost of the plant increases and the work done per kg of steam is reducedwhich results in higher boiler capacity for given output.

    UNIT IV

    1. State Boyles law.

    Boyles law states, The volume of a given mass of agas varies inversely as

    its absolute pressure, when the temperature remains constant.

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    1

    2. State Charle,s law.

    Charle,s law states The volume of a given mass of a gas varies directly asits absolute temperature, when the pressure remains constant.

    T

    3. State Joules law.

    Joules law states, The internal energy of a given quantity of a gas dependsonly on the temperature.

    4. State Regnaults law.

    Regnaults law states that Cp and Cv of a gas always remains constant.

    5. State Avogadros law.

    Avogardros law states, Equal volumes of different perfect gases at thesame temperature and pressure, contain equal number of molecules.

    6. State Daltons law of partial pressure.

    Daltons law of partial pressure states the total pressure of a mixture ofgases is equal to the sum of the partial pressure exerted by individualgases if each one of them occupied separately in the total volume of themixture at mixture temperature.

    P=P1+P2+P3+.........Pk

    7. How does the Vander waals equation differ from the ideal gasequation of state?

    1. Intermolecular attractive study is made.

    2. Shape factor is considered.

    These assumptions are not made in ideal gas equation of state.

    8. Distinguish between ideal and real gas?

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    An ideal gas is one which strictly follows the gas laws under all conditionsof temperature and pressure.

    In actual practice, there is no real gas which strictly follows the gas laws

    over the entire range of temperature and pressure. However hydrogen,oxygen, nitrogen and air behave as an ideal gas under certaintemperature and pressure limits.

    9. What is meant by virtual expansion?

    Viral or virtual expansions are only applicable to gases of low and mediumdensities.

    The equation of state of a pure substance is given by

    P = RT + a(T) +b(T) +c(T) +d(T) +............

    The coefficient of a(T), b(T), c(T), d(T)......are virial coefficients. The virialcoefficient will vanish when the pressure becomes zero. Finally, the

    equation of state reduces to the ideal-gas equation.

    10. What are Maxwell relations?

    =-

    =

    =

    =-

    These are known as Maxwell relations.

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    11. Determine the molecular volume of any perfect gas at600N/m and 30C. Universal gas constant may be taken as8314J/Kg mole-K

    Given data:

    P = 600N/m

    T = 30C =30+273 =303K

    R = 8314J/kgmole-K

    Solution:

    Ideal gas equation, Pv = mRT

    V =mRT

    P

    18314303

    = 600

    = 4198.57m/kg-mole

    12.Define Joule-Thomson co-efficient.

    Joule-Thomson co-efficient is defined as the change in temperature withchange in pressure, keeping the enthalpy remains constant.It is denotedby the

    13. Define co-efficient of volume expansion and Isothermalcompressibility?

    Co-efficient of volume expansions:

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    Co-efficient of volume expansionsis defined as the change in volume with change in temperature per unitvolume keeping the pressure constant. It is denoted by .

    Isothermal compressibility:

    It is defined as the change in volume withchange in pressure per unit volume by keeping the temperature constant.It is denoted by K.

    K= -

    14. What is compressibility factor?

    We know that, the perfect gas equation is pv = RT. But for real gas, acorrection factor has to be introduced in the perfect gas equation to takeinto account the deviation of real gas from the perfect gas equation. Thisfactor is known as compressibility factor(z) and is defined by

    Z =

    15. What does compressibility factor signify? What is its valuefor an ideal gas at critical point?

    1. Intermolecular attractive study is made.

    2. Shape factor is considered.

    At critical point, the Vander waals equation

    for ideal gas.

    16. What is Joule-Thomson co-efficient? Why is it zero for anideal gas?

    Joule-Thomson co-efficient is defined as the change in temperature with

    change in pressure, keeping the enthalpy remains constant. It is denotedby

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    =

    We know that the equation of state as

    PV = RT

    Differentiating the above equation of state with respect to T by keepingpressure, p constant.

    = =

    It simplifies that the Joule-Thomson co- efficient is zero for ideal gas.

    17. What is clasius clapeyron Equation?

    Clapeyron equation which involves relationship between the saturationpressure, saturation temperature, the enthalpy of evaporation and thespecific volume of the two phases involved.

    dt

    18. State Tds equations.

    Tds equations are

    Tds =

    Tds =

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    19. State the assumptions made in kinetic theory of gases?

    1. There is no intermolecular force between particles.

    2. The volume of the molecules is negligible in comparison with the gas.

    20. State Helmholtz function

    Helmholtz function is property of a system and is given by subtracting theproduct of absolute temperature (T) and entropy (s) from the internalenergy U.

    That is Helmholtz function = u-Ts

    21. State Gibbs function

    Gibbs function is property of a system and is given by

    G= u-Ts +pv =h-Ts

    Where

    h - Enthalpy

    T - Temperature

    S -Entropy

    22. What is a thermodynamic cycle?

    Thermodynamic cycle is defined as the series of processes performed onthe system, so that the system attains its original state.

    23. What is meant by air standard cycle?

    If we use air as a working substance in the thermodynamic cycles it iscalled air standard cycles.

    24. Name the various gas power cycles

    1. Carnot cycle

    2. Otto cycle

    3. Diesel cycle

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    4. Brayton cycle

    25. Mention the various processes of the Otto cycle.

    1. Isentropic compression.

    2. Constant volume heat supplied.

    3. Isentropic expansion, and

    4. Constant volume heat rejection.

    UNIT V

    1. What is the difference between air conditioning and refrigeration?

    Refrigeration is the process of providing and maintaining the temperaturein space below atmospheric temperature.

    Air conditioning is the process of supplying sufficient volume of clean aircontaining a specific amount of water vapour and maintaining thepredetermined atmospheric condition with in a selected enclosure.

    2. Define psychrometry?

    The science which deals with the study of behaviour of moist air (mixtureof dry air and water vapour) is known as psychrometry.

    3. Define dry bulb temperature?

    The temperature which is measured by an ordinary thermometer is known

    as dry bulb temperature. It is generally denoted by .

    4. Define wet bulb temperature?

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    It is the temperature of air measured by a thermometer when its bulb iscovered with wet cloth and exposed to a current rapidly moving air. It is

    denoted by .

    5. Define dew point temperature?

    The temperature at which the water vapour present in air begins tocondense when the air is cooled is known as dew point temperature. It is

    denoted by .

    6. Define Relative humidity?

    Relative humidity is the ratio of the mass of water vapour ( ) in a certain

    volume of moist air at a given temperature to the mass of water vapour (

    ) in the same volume of saturated air at the same temperature.

    i .e , RH (or) =

    7. Define specific humidity?

    Specific humidity ( ) is the ratio of mass of water vapour( ) to the mass

    of dry air in the given in the given volume of mixture.

    i.e,

    8. Define absolute humidity?

    Absolute humidity is defined as the ratio of the mass of water vapour( )

    in a certain volume of moist air at a given temperature to the mass of

    water vapour( ) at atmospheric conditions.

    9. Differentiate between absolute and relative humidity?

    Absolute humidity is defined as the ratio of the mass of water vapour( )

    in a certain volume of moist air at a given temperature to the mass of

    water vapour( ) at atmospheric conditions.

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    RH is the ratio of the mass of water vapour( ) in a certain volume of

    moist air at a given temperature to the mass of water vapour( ) in the

    same volume of saturated air at the same temperature.

    10. Define degree of saturation?

    Degree of saturation is the ratio of specific humidity of moist air to thespecific humidity of saturated air at same temperature.

    11. What is dew point temperature? How is it related to dry bulband wet bulb temperature at the saturation condition?

    It is the temperature at which the water vapour present in air begins tocondense when theair is cooled.

    For saturated air,the dry bulb,wet bulb and dew point temperature are allsame.

    12. State Daltons law of partial pressure.

    The total pressure exerted by air and water vapour mixture is equal to thebarometric pressure.

    +

    Where

    Baromertic pressure.

    = partial pressure of dry air.

    = Partial pressure of water vapour.

    13. Define Apparatus Dew Point (ADP) of cooling coil.

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    For dehumidification, the cooling coil is to be kept at a mean temperaturewhich is below the dew point temperature(DPT) the entering air. Thistemperature of the coil is called ADP temperature.

    14. List down the psychrometric process.

    1. Sensible heating process.

    2. Sensible cooling process.

    3. Humidification process.

    4. Dehumidification process.

    5. Heating and humidification process.

    6. Cooling and dehumidification process.

    7. Adiabatic mixing of air stream process.

    8. Evaporative cooling process.

    15. Define bypass factor(BPF) of a coil?

    The ratio of the amount of air which does not contact the coolingcoil(amount of bypassing air) to the amount of supply air is called BPF.

    i.e., BPF =

    16.Define the humidification process.

    Humidification is defined as the process of adding moisture at constant

    dry bulb temperature. So, but . So, the humidity ratio

    increases from

    17. State the effects of very high and a very low bypass factor.

    Very high bypass factor:

    1. It requires lower ADP. Refrigerant plant should be of largercapacity.

    2. It requires more air. Larger fan motor required.

    3. It requires less heat transfer area.

    4. It requires more chilling water. Larger piping required.

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    Very low bypass factor:

    1. Higher ADP is to be employed.

    2. It requires less air. Fan and motor size reduced.

    18. What factors affect bypass factor?

    1. Pitch of fins.

    2. Number of coil tubes.

    3. Air velocity over the coil.

    4. Direction of air flow.

    19. What are the assumptions made while mixing two airstreams?

    1. Surrounding is small

    2. Process is fully adiabatic.

    3. There is no work interactions.

    4. Change in kinetic and potential energies are negligible.

    20. How are air-conditioning systems classified?

    1. Based on construction of components:

    a. Unitary system.

    b. Central system.

    c. Package system.

    d. Split units.

    2. Based on fluid flow methods:

    a. Direct expansion(DX) system.

    b. Chilled water (DX) system.

    c. Chilled water air washer system.

    21. How does humidity affect human comfort?

    If the humidity is above a certain level, water vapour from human body

    moisture cannot be absorbed by the atmospheric air. It results indiscomfort because of sweating.

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    22. What are the various sources of heat gain of an air-conditioned space?

    1. solar gain through glass panes.

    2. solar gain through roof and walls.

    3. heat gain from occupants.

    4. heat gain from appliances and lights.

    5. duct leakage.

    6. infiltration.

    7. vapour transmission.

    23. What are the requirements of comfort a/c ?

    a. Supply of and removal of .

    b. Removal of heat of occupants.

    c. Removal of moisture of occupants.

    d. Good air distribution.

    e. Maintaining air purity.

    24. Define effective temperature?

    Effective temperature is defined as that temperature of saturated air atwhich the subject would experience the same feeling of comfort asexperienced in the actual unsaturated environment.

    25. What factors affect effective temperature?

    1. climatic and seasonal differences.

    2. Clothing.

    3. Age.

    4. activity.

    5. stay duration.

    6. air velocity.

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