8/14/2019 Unit Iv2013

1/9

UNIT IV

1. State Daltons law of partial pressure.

Daltons law of partial pressure states the total pressure of a mixture of gases

is equal to the sum of the partial pressure exerted by individual gases if eachone of them occupied separately in the total volume of the mixture at mixturetemperature.

P=P1+P+P!+.........P"

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

1. #ntermolecular attractive study is made.

. $hape factor is considered.

%hese assumptions are not made in ideal gas equation of state.

!. Distinguish "etween ideal and real gas

&n ideal gas is one which strictly follows the gas laws under all conditions oftemperature and pressure.

#n actual practice' there is no real gas which strictly follows the gas laws overthe entire range of temperature and pressure. (owever hydrogen' oxygen'

nitrogen and air behave as an ideal gas under certain temperature andpressure limits.

#. $hat is meant "% &irtual e'pansion

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

%he equation of state of a pure substance is given by

P = *% + a%, +b%, +c%, +d%, +............

- / 0 2

%he coefficient of a%,' b%,' c%,' d%,......are virial coefficients. %he virialcoefficient will vanish when the pressure becomes 3ero. 4inally' the equationof state reduces to the ideal5gas equation.

8/14/2019 Unit Iv2013

2/9

(. $hat are )a'well relations

=5

=

=

=5

%hese are "nown as 6axwell relations.

7. Define *oule+Thomson ,o+effi,ient.

8oule5%homson co5efficient is defined as the change in temperature withchange in pressure' "eeping the enthalpy remains constant.#t is denoted bythe

-. Define ,o+effi,ient of &olume e'pansion and Isothermal

,ompressi"ilit%

o+effi,ient of &olume e'pansions/

9o5efficient of volume expansions isdefined as the change in volume with change in temperature per unit volume"eeping the pressure constant. #t is denoted by :.

8/14/2019 Unit Iv2013

3/9

Isothermal ,ompressi"ilit%;

#t is defined as the change in volume withchange in pressure per unit volume by "eeping the temperature constant. #t isdenoted by

8/14/2019 Unit Iv2013

4/9

e "now that the equation of state as

P) = *%

Differentiating the above equation of state with respect to % by "eepingpressure' p constant.

= =

#t simplifies that the 8oule5%homson co5 efficient is 3ero for ideal gas.

11. $hat is ,lasius ,lape%ron 4quation

9lapeyron equation which involves relationship between the saturationpressure' saturation temperature' the enthalpy of evaporation and thespecific volume of the two phases involved.

dt

12. State Tds equations.

%ds equations are

%ds =

%ds =

8/14/2019 Unit Iv2013

5/9

1!. State the assumptions made in 5ineti, theor% of gases

1. %here is no intermolecular force between particles.

. %he volume of the molecules is negligible in comparison with the gas.

!.

1#. State Helmholt3 fun,tion

(elmholt3 function is property of a system and is given by subtracting theproduct of absolute temperature %, and entropy s, from the internal energy@.

%hat is (elmholt3 function = u5%s

1(. State 6i""s fun,tion

Aibbs function is property of a system and is given by

A= u5%s +pv =h5%s

here

h 5 Bnthalpy

% 5 %emperature

$ 5Bntropy

UNIT V

1. $hat is the differen,e "etween air ,onditioning and refrigeration

8/14/2019 Unit Iv2013

6/9

*efrigeration is the process of providing and maintaining the temperature inspace below atmospheric temperature.

&ir 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 ps%,hrometr%

%he science which deals with the study of behaviour of moist air mixture ofdry air and water vapour, is "nown as psychrometry.

!. Define dr% "ul" temperature

%he temperature which is measured by an ordinary thermometer is "nown as

dry bulb temperature. #t is generally denoted by .

#. Define wet "ul" temperature

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

denoted by .

(. Define dew point temperature

%he temperature at which the water vapour present in air begins to condensewhen the air is cooled is "nown as dew point temperature. #t is denoted by

.

7. Define 8elati&e humidit%

*elative 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 ' *( or, C =

-. Define spe,ifi, humidit%

8/14/2019 Unit Iv2013

7/9

$pecific 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'

0. Define a"solute humidit%

&bsolute 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.

. Differentiate "etween a"solute and relati&e humidit%

&bsolute humidity is defined as the ratio of the mass of water vapour , in acertain volume of moist air at a given temperature to the mass of water

vapour , at atmospheric conditions.

*( 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.

1. 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. $hat is dew point temperature How is it related to dr% "ul"and wet "ul" temperature at the saturation ,ondition

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

4or saturated air'the dry bulb'wet bulb and dew point temperature are allsame.

8/14/2019 Unit Iv2013

8/9

12. State Daltons law of partial pressure.

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

+

here

>aromertic pressure.

= partial pressure of dry air.

= Partial pressure of water vapour.

1!. Define 9pparatus Dew :oint ;9D:< of ,ooling ,oil.

4or dehumidification' the cooling coil is to be "ept at a mean temperaturewhich is below the dew point temperatureDP%, the entering air. %histemperature of the coil is called &DP temperature.

1#. =ist down the ps%,hrometri, pro,ess.

1. $ensible heating process.

. $ensible cooling process.

!. (umidification process.

. Dehumidification process.

E. (eating and humidification process.

7. 9ooling and dehumidification process.

F. &diabatic mixing of air stream process.

G. Bvaporative cooling process.

1(. Define "%pass fa,tor;>:?< of a ,oil

%he ratio of the amount of air which does not contact the cooling coilamountof bypassing air, to the amount of supply air is called >P4.

8/14/2019 Unit Iv2013

9/9

i.e.' >P4 =

17. Define the humidifi,ation pro,ess.

(umidification is defined as the process of adding moisture at constant dry

bulb temperature. $o' but . $o' the humidity ratio increases

from