At the end of the process, which of the following situations will be true ?

No vapour will be left in the system

Superheated vapour will be left in the system

No vapour will be left in the system

A liquid + vapour mixture will be left in the system

The mixture will exist at a dry saturate vapour state

Gaseous Nitrogen at 30°C is expanded through a converging nozzle from a total pressure of 0.5 MPa to a back pressure chamber. If the back pressure is increased from 0.1 MPa to 0.4 MPa in steps of 0.02 MPa, the trend in mass flow rate through the nozzle

Will remain constant till a point and then gradually increase

Will remain constant till a point and then gradually decrease

Will remain constant till a point and then gradually increase

Polytropic index n is given by

\(\frac{{\ln \left( {\frac{{{p_1}}}{{{p_2}}}} \right)}}{{\ln \left( {\frac{{{v_1}}}{{{v_2}}}} \right)}}\)

\(\frac{{\ln \left( {\frac{{{p_2}}}{{{p_1}}}} \right)}}{{\ln \left( {\frac{{{v_1}}}{{{v_2}}}} \right)}}\)

\(\frac{{\ln \left( {\frac{{{p_1}}}{{{p_2}}}} \right)}}{{\ln \left( {\frac{{{v_1}}}{{{v_2}}}} \right)}}\)

\(\frac{{\ln \left( {\frac{{{v_1}}}{{{v_2}}}} \right)}}{{\ln \left( {\frac{{{p_2}}}{{{p_1}}}} \right)}}\)

\(\frac{{\ln \left( {\frac{{{v_2}}}{{{v_1}}}} \right)}}{{\ln \left( {\frac{{{p_2}}}{{{p_1}}}} \right)}}\)

A compressor undergoes a reversible, steady flow process. The gas at inlet and outlet of the compressor is designated as state 1 and state 2 respectively. Potential and kinetic energy changes are to be ignored. The following notations are used:v = specific volume and P = pressure of the gas.The specific work required to be supplied to the compressor for this gas compression process is

\(\mathop \smallint \limits_1^2 Pdv\)

\(\mathop \smallint \limits_1^2 vdP\)

A reversible polytropic process is given by

\(\frac{{{T_1}}}{{{T_2}}} = {\left\{ {\frac{{{P_1}}}{{{P_2}}}} \right\}^{n - 1}}\)

\(\frac{{{T_1}}}{{{T_2}}} = {\left\{ {\frac{{{\rho _1}}}{{{\rho _2}}}} \right\}^{n}}\)

\(\frac{{{P_1}}}{{{P_2}}} = {\left\{ {\frac{{{\rho _1}}}{{{\rho _2}}}} \right\}^n}\)

\(\frac{{{T_1}}}{{{T_2}}} = {\left\{ {\frac{{{P_1}}}{{{P_2}}}} \right\}^{n - 1}}\)

\(\frac{{{T_1}}}{{{T_2}}} = {\left\{ {\frac{{{\rho _1}}}{{{\rho _2}}}} \right\}^{\frac{{n - 1}}{n}}}\)

In a polytropic process, heat rejected is given by

\(\frac{\gamma - n}{\gamma} \times\) work done on the system

\(\frac{\gamma}{\gamma - 1} \times\) work done on the system

\(\frac{\gamma - n}{\gamma - 1} \times\) work done on the system.

\(\frac{\gamma - n}{\gamma} \times\) work done on the system

\(\frac{\gamma - n}{\eta} \times\) work done on the system.

In a throttling process with negligible change in the potential and kinetic energies:

the enthalpy does not remain constant

In a compressor, work is done by:

The rotating part called stator

A static component known as impeller

Correct statement for First law of thermodynamics

Work done by the system equals to heat transferred by the system

Total energy of system and surroundings remains constant

Work done by the system equals to heat transferred by the system

Internal energy of a system remains constant during a process

Entropy of a system remains constant during a process.

185 + Mcqs in First Law Thermodynamics in Fluid Mechanics Page 2 McqOptions

51.	At the end of the process, which of the following situations will be true ?
A.	Superheated vapour will be left in the system
B.	No vapour will be left in the system
C.	A liquid + vapour mixture will be left in the system
D.	The mixture will exist at a dry saturate vapour state
Answer» B. No vapour will be left in the system

Discussion

52.	A mixture of gases expands from 0.03 m3 to 0.06 m3 at a constant pressure of 1 MPa and absorbs 84 kJ of heat during the process. The change in internal energy of the mixture is
A.	30 kJ
B.	54 kJ
C.	84 kJ
D.	114 kJ
Answer» C. 84 kJ

Discussion

53.	Gaseous Nitrogen at 30°C is expanded through a converging nozzle from a total pressure of 0.5 MPa to a back pressure chamber. If the back pressure is increased from 0.1 MPa to 0.4 MPa in steps of 0.02 MPa, the trend in mass flow rate through the nozzle
A.	Will gradually decrease
B.	Will gradually increase
C.	Will remain constant till a point and then gradually decrease
D.	Will remain constant till a point and then gradually increase
Answer» D. Will remain constant till a point and then gradually increase

Discussion

54.	Paddle wheel work and expansion of gas into vacuum (free expansion) is a
A.	Quasi-equilibrium process
B.	Quasi static process
C.	Isotropic process
D.	Non-equilibrium process
Answer» E.

Discussion

55.	Polytropic index n is given by
A.	\(\frac{{\ln \left( {\frac{{{p_2}}}{{{p_1}}}} \right)}}{{\ln \left( {\frac{{{v_1}}}{{{v_2}}}} \right)}}\)
B.	\(\frac{{\ln \left( {\frac{{{p_1}}}{{{p_2}}}} \right)}}{{\ln \left( {\frac{{{v_1}}}{{{v_2}}}} \right)}}\)
C.	\(\frac{{\ln \left( {\frac{{{v_1}}}{{{v_2}}}} \right)}}{{\ln \left( {\frac{{{p_2}}}{{{p_1}}}} \right)}}\)
D.	\(\frac{{\ln \left( {\frac{{{v_2}}}{{{v_1}}}} \right)}}{{\ln \left( {\frac{{{p_2}}}{{{p_1}}}} \right)}}\)
Answer» B. \(\frac{{\ln \left( {\frac{{{p_1}}}{{{p_2}}}} \right)}}{{\ln \left( {\frac{{{v_1}}}{{{v_2}}}} \right)}}\)

Discussion

56.	In a cyclic process, heat transfers are 157 kJ, -262 kJ, -486 kJ and 315 kJ Net work for this cycle process is:
A.	151 kJ
B.	276 kJ
C.	176 kJ
D.	252 kJ
Answer» C. 176 kJ

Discussion

57.	A system is undergoing a cycle that consists of three processes. During the first process, the work is 5 kJ and the heat is 23 kJ. In the second process no work takes place and the heat interaction is -50 kJ. The third process is adiabatic. The work in the third process is
A.	-32 kJ
B.	-23 kJ
C.	-22 kJ
D.	Zero
Answer» B. -23 kJ

Discussion

58.	In a thermodynamic system, thermal equilibrium is achieved when two bodies reach
A.	same thermal energy
B.	same entropy
C.	same temperature
D.	same molecular energy
Answer» D. same molecular energy

Discussion

59.	______ is used for pumping water into a boiler.
A.	Rotor
B.	Feed pump
C.	Duplex pump
D.	Economiser
Answer» C. Duplex pump

Discussion

60.	An ideal gas undergoes an isothermal process between states 1 and 2. The applicable equation is:
A.	P1V1 = P2V2
B.	P1/T1 = P2/T2
C.	PVγ = constant
D.	ρ = constant
Answer» B. P1/T1 = P2/T2

Discussion

61.	Assume air as a perfect gas. It flows into a diffuser at 300 m/s, 300 K and 100 kPa. At exit, the velocity is negligibly small, but the pressure is high. Assuming zero heat transfer, the exit temperature is:
A.	325 K
B.	452.6 K
C.	344.8 K
D.	425 K
Answer» D. 425 K

Discussion

62.	In a two component system, if the non-compositional variable is only temperature, the number of degrees of freedom in the case of a single phase field as per Gibbs Phase Rule is?
A.	0
B.	1
C.	2
D.	3
Answer» D. 3

Discussion

63.	If the work is done by the system, it is known as
A.	Positive work
B.	Negative work
C.	Adiabatic work
D.	Isothermal work
Answer» B. Negative work

Discussion

64.	A compressor undergoes a reversible, steady flow process. The gas at inlet and outlet of the compressor is designated as state 1 and state 2 respectively. Potential and kinetic energy changes are to be ignored. The following notations are used:v = specific volume and P = pressure of the gas.The specific work required to be supplied to the compressor for this gas compression process is
A.	\(\mathop \smallint \limits_1^2 Pdv\)
B.	\(\mathop \smallint \limits_1^2 vdP\)
C.	v1(P1 – P2)
D.	– P2(v1 – v2)
Answer» C. v1(P1 – P2)

Discussion

65.	A calorically perfect gas (specific heat at constant pressure 1000 J/kg K) enters and leaves a gas turbine with the same velocity. The temperatures of the gas at turbine entry and exit are 1100 K and 400 K, respectively. The power produced is 4.6 MW and heat escapes at the rate of 300 kJ/s through the turbine casing. The mass flow rate of the gas (in kg/s) through the turbine is
A.	6.14
B.	7
C.	7.5
D.	8
Answer» C. 7.5

Discussion

66.	0.8 kg of air flows through a compressor under steady state conditions. The properties of air at entry are : pressure 1 bar, velocity 10 m/s, specific volume 0.95 m3/kg and internal energy 30 kJ/kg. The corresponding values at exit are 8 bar, 6 m/s, 0.2 m3/kg and 124 kJ/kg. Neglecting change in potential energy, the power input will be
A.	117 kW
B.	127 kW
C.	137 kW
D.	147 kW
Answer» C. 137 kW

Discussion

67.	For a given system, if heat is denoted by ‘Q’ and work is denoted by ‘w’. the cyclic integral of (dQ – dw) for a closed system will be:
A.	positive
B.	negative
C.	zero
D.	unpredictable
Answer» D. unpredictable

Discussion

68.	Certain quantities cannot be located on the graph by a point but are given by the area under the curve corresponding to the process. These quantities in concepts of thermodynamics are called as
A.	cyclic functions
B.	point functions
C.	path functions
D.	real functions
Answer» D. real functions

Discussion

69.	A room contains 25 kg of air at 100 kPa and 14°C. The room has a 250 W refrigerator and 1 kW electric resistance heater. During a cold winter day, it is observed that both the refrigerator and the heater are running continuously, but the air temperature in the room remains constant. The rate of heat loss from the room during that day is
A.	3600 kJ/hr.
B.	1250 kJ/hr.
C.	4500 kJ/hr.
D.	2700 kJ/hr.
Answer» D. 2700 kJ/hr.

Discussion

70.	In a general compression process, 1 kJ of mechanical work is supplied to 2 kg of fluid and 400 J of heat is rejected to the cooling jacket. The change in specific internal energy would be-
A.	700 J/kg
B.	350 J/kg
C.	300 J/kg
D.	600 J/kg
Answer» D. 600 J/kg

Discussion

71.	A system will be in thermodynamic equilibrium only if it is in ____.A. Thermal equilibriumB. Mechanical equilibriumC. Chemical equilibrium
A.	Only A
B.	Only B
C.	Only C
D.	A, B and C
Answer» E.

Discussion

72.	A reversible polytropic process is given by
A.	\(\frac{{{T_1}}}{{{T_2}}} = {\left\{ {\frac{{{\rho _1}}}{{{\rho _2}}}} \right\}^{n}}\)
B.	\(\frac{{{P_1}}}{{{P_2}}} = {\left\{ {\frac{{{\rho _1}}}{{{\rho _2}}}} \right\}^n}\)
C.	\(\frac{{{T_1}}}{{{T_2}}} = {\left\{ {\frac{{{P_1}}}{{{P_2}}}} \right\}^{n - 1}}\)
D.	\(\frac{{{T_1}}}{{{T_2}}} = {\left\{ {\frac{{{\rho _1}}}{{{\rho _2}}}} \right\}^{\frac{{n - 1}}{n}}}\)
Answer» C. \(\frac{{{T_1}}}{{{T_2}}} = {\left\{ {\frac{{{P_1}}}{{{P_2}}}} \right\}^{n - 1}}\)

Discussion

73.	Molecules of Argon have how many degrees of freedom?
A.	two
B.	one
C.	three
D.	five
Answer» D. five

Discussion

74.	_____ property is stated by first law of thermodynamics.
A.	Temperature
B.	Entropy
C.	Pressure
D.	Internal energy
Answer» E.

Discussion

75.	An ideal gas undergoes an isothermal expansion from state R to state S in the turbine as shown in the diagram given below:The area of the shaded region is 1000 N-m. The amount is turbine work done during the process is
A.	14,000 N – m
B.	12,000 N – m
C.	11,000 N – m
D.	10,000 N – m
Answer» D. 10,000 N – m

Discussion

76.	In a polytropic process, heat rejected is given by
A.	\(\frac{\gamma}{\gamma - 1} \times\) work done on the system
B.	\(\frac{\gamma - n}{\gamma - 1} \times\) work done on the system.
C.	\(\frac{\gamma - n}{\gamma} \times\) work done on the system
D.	\(\frac{\gamma - n}{\eta} \times\) work done on the system.
Answer» C. \(\frac{\gamma - n}{\gamma} \times\) work done on the system

Discussion

77.	Consider the following statements for isothermal process:1. Change in internal energy is zero2. Heat transfer is zeroWhich of the above statements is/are correct?
A.	1 only
B.	2 only
C.	Both 1 and 2
D.	Neither 1 nor 2
Answer» B. 2 only

Discussion

78.	Change in internal energy in a reversible process occurring in a closed system is equal to the heat transferred, if the process occurs at constant
A.	Pressure
B.	Volume
C.	Temperature
D.	Enthalpy
Answer» C. Temperature

Discussion

79.	Calculate the enthalpy of 3 kg of fluid that occupies a volume of 1.5 m3/kg, if the internal energy is 3.5 MJ/kg and the pressure is 0.3 MN/m2
A.	3.95 MJ
B.	3.65 MJ
C.	10.95 MJ
D.	None of these
Answer» E.

Discussion

80.	A tank containing air is stirred by a paddle wheel. The work input to the wheel is 14000 kJ and heat transferred to the surrounding from the tank is 5000 kJ. The change in internal energy of the system (air) is:
A.	-9000 kJ
B.	+9000 kJ
C.	+19000 kJ
D.	-19000 kJ
Answer» C. +19000 kJ

Discussion

81.	Air is being forced by the bicycle pump into a tyre against a pressure of 4.5 bars. A slow downward movement of the piston can be approximated as
A.	isobaric process
B.	adiabatic process
C.	throttling process
D.	isothermal process
Answer» E.

Discussion

82.	Change in internal energy of a system is zero if _________ is constant.
A.	entropy
B.	work
C.	temperature
D.	mass
Answer» D. mass

Discussion

83.	Control volume refers to
A.	A fixed region in space
B.	A specified mass
C.	An isolated system
D.	A reversible process only
Answer» B. A specified mass

Discussion

84.	A gas is contained in a cylinder with a moveable piston of 100 kg mass. When 2500 J of heat flows into the gas, the internal energy of the gas increases by 1500 J. What is the distance through which the piston rises?
A.	2 m
B.	1 m
C.	2.5 m
D.	0.5 m
Answer» C. 2.5 m

Discussion

85.	Diffusor increases the pressure of a fluid at the expense of its:
A.	kinetic energy
B.	impact energy
C.	potential energy
D.	rotational energy
Answer» B. impact energy

Discussion

86.	A 100 W electric bulb was switched on in a 2.5 m × 3 m × 3 m size thermally insulated room having a temperature of 20°C. The room temperature at the end of 24 hours will be. (Take density of air = 1.2 kg/m3 and cv of air = 0.717 kJ/kg.
A.	321 °C
B.	341 °C
C.	450 °C
D.	470 °C
Answer» E.

Discussion

87.	Constant volume process is
A.	Isopiestic process
B.	Hyperbolic process
C.	Isometric process
D.	Polytropic process
Answer» D. Polytropic process

Discussion

88.	A gas is compressed in a frictionless piston from an initial state of y m3 and 1 MPa to a final state of 0.2 m3 and 1 MPa. There is a transfer of 40 kJ of heat from the gas and a drop of 20kJ in internal energy. What is the initial state volume of the gas?
A.	0.2
B.	0.22
C.	19.8
D.	20.2
Answer» C. 19.8

Discussion

89.	A gas expands in a frictionless piston – cylinder arrangement. The expansion process is very slow, and is resisted by an ambient pressure of 100 kPa. During the expansion process, the pressure of the system (gas) remains constant at 300 kPa. The change in volume of the gas is 0.01 m3. The maximum amount of work that could be utilized from the above process is
A.	0 kJ
B.	1 kJ
C.	2 kJ
D.	3 kJ
Answer» D. 3 kJ

Discussion

90.	A mono-atomic ideal gas (γ = 1.67, molecular weight = 40) is compressed adiabatically from 0.1 MPa, 300 K to 0.2 MPa . The universal gas constant is 8.314 kJmol-1K-1. The work of compression of the gas (in kJ kg-1) is
A.	29.7
B.	19.9
C.	13.3
D.	0
Answer» B. 19.9

Discussion

91.	If a gas vapour is allowed to expand through a very minute aperture, then such a process is known as _________.
A.	Free expansion
B.	Throttling
C.	Hyperbolic expansion
D.	Parabolic expansion
Answer» C. Hyperbolic expansion

Discussion

92.	In a throttling process with negligible change in the potential and kinetic energies:
A.	the enthalpy remains constant
B.	the entropy remains constant
C.	the pressure remains constant
D.	the enthalpy does not remain constant
Answer» B. the entropy remains constant

Discussion

93.	Isothermal compressibility of an ideal gas is
A.	nR/VP
B.	nRT/VP2
C.	RT/VP2
D.	nRT/VP
Answer» C. RT/VP2

Discussion

94.	In a compressor, work is done by:
A.	The fluid on the rotor
B.	The rotor on the fluid element
C.	The rotating part called stator
D.	A static component known as impeller
Answer» C. The rotating part called stator

Discussion

95.	Correct statement for First law of thermodynamics
A.	Total energy of system and surroundings remains constant
B.	Work done by the system equals to heat transferred by the system
C.	Internal energy of a system remains constant during a process
D.	Entropy of a system remains constant during a process.
Answer» B. Work done by the system equals to heat transferred by the system

Discussion

96.	Gas laws are least valid in the case of
A.	Mono-atomic gases
B.	Real gases
C.	Vapours
D.	Mixture of gases
Answer» D. Mixture of gases

Discussion

97.	In a constant volume process, the reversible moving boundary work associated with closed system (in kJ/kg) is:
A.	0.5
B.	1
C.	0
D.	1.5
Answer» D. 1.5

Discussion

98.	A container filled with 2 kg of O2 is heated at constant pressure from 27°C to 127°C. The heat supplied in this process is:
A.	205 kJ
B.	100 kJ
C.	225 kJ
D.	182 kJ
Answer» E.

Discussion

99.	A room contains 60 kg of air at 100 kPa and 15°C. The room has a 250 W refrigerator (the refrigerator consumes 250 W of electricity when running), a 120 W TV, a 1 kW electric resistance heater, and a 50-W fan. During a cold winter day, it is observed that the refrigerator, the TV, the fan, and the electric resistance heater are running continuously but the air temperature in the room remains constant. The rate of heat loss from the room that day is
A.	3312 kJ/h
B.	4752 kJ/h
C.	5112 kJ/h
D.	2952 kJ/h
Answer» D. 2952 kJ/h

Discussion

100.	A certain amount of an ideal gas initially at a pressure P1 and temperature T1. First, it undergoes a constant pressure process 1 – 2 such that T2 = 3T1/4. Then, it undergoes a constant volume process 2 – 3 such that T3 = T1/2. The ratio of the final volume to the initial volume of the ideal gas is
A.	0.25
B.	0.75
C.	1
D.	1.5
E.	2
Answer» C. 1

Discussion

Explore topic-wise MCQs in Fluid Mechanics.

At the end of the process, which of the following situations will be true ?

A mixture of gases expands from 0.03 m3 to 0.06 m3 at a constant pressure of 1 MPa and absorbs 84 kJ of heat during the process. The change in internal energy of the mixture is

Gaseous Nitrogen at 30°C is expanded through a converging nozzle from a total pressure of 0.5 MPa to a back pressure chamber. If the back pressure is increased from 0.1 MPa to 0.4 MPa in steps of 0.02 MPa, the trend in mass flow rate through the nozzle

Paddle wheel work and expansion of gas into vacuum (free expansion) is a

Polytropic index n is given by

In a cyclic process, heat transfers are 157 kJ, -262 kJ, -486 kJ and 315 kJ Net work for this cycle process is:

A system is undergoing a cycle that consists of three processes. During the first process, the work is 5 kJ and the heat is 23 kJ. In the second process no work takes place and the heat interaction is -50 kJ. The third process is adiabatic. The work in the third process is

In a thermodynamic system, thermal equilibrium is achieved when two bodies reach

______ is used for pumping water into a boiler.

An ideal gas undergoes an isothermal process between states 1 and 2. The applicable equation is:

Assume air as a perfect gas. It flows into a diffuser at 300 m/s, 300 K and 100 kPa. At exit, the velocity is negligibly small, but the pressure is high. Assuming zero heat transfer, the exit temperature is:

In a two component system, if the non-compositional variable is only temperature, the number of degrees of freedom in the case of a single phase field as per Gibbs Phase Rule is?

If the work is done by the system, it is known as

For a given system, if heat is denoted by ‘Q’ and work is denoted by ‘w’. the cyclic integral of (dQ – dw) for a closed system will be:

Certain quantities cannot be located on the graph by a point but are given by the area under the curve corresponding to the process. These quantities in concepts of thermodynamics are called as

In a general compression process, 1 kJ of mechanical work is supplied to 2 kg of fluid and 400 J of heat is rejected to the cooling jacket. The change in specific internal energy would be-

A system will be in thermodynamic equilibrium only if it is in ____.A. Thermal equilibriumB. Mechanical equilibriumC. Chemical equilibrium

A reversible polytropic process is given by

Molecules of Argon have how many degrees of freedom?

_____ property is stated by first law of thermodynamics.

An ideal gas undergoes an isothermal expansion from state R to state S in the turbine as shown in the diagram given below:The area of the shaded region is 1000 N-m. The amount is turbine work done during the process is

In a polytropic process, heat rejected is given by

Consider the following statements for isothermal process:1. Change in internal energy is zero2. Heat transfer is zeroWhich of the above statements is/are correct?

Change in internal energy in a reversible process occurring in a closed system is equal to the heat transferred, if the process occurs at constant

Calculate the enthalpy of 3 kg of fluid that occupies a volume of 1.5 m3/kg, if the internal energy is 3.5 MJ/kg and the pressure is 0.3 MN/m2

A tank containing air is stirred by a paddle wheel. The work input to the wheel is 14000 kJ and heat transferred to the surrounding from the tank is 5000 kJ. The change in internal energy of the system (air) is:

Air is being forced by the bicycle pump into a tyre against a pressure of 4.5 bars. A slow downward movement of the piston can be approximated as

Change in internal energy of a system is zero if _________ is constant.

Control volume refers to

A gas is contained in a cylinder with a moveable piston of 100 kg mass. When 2500 J of heat flows into the gas, the internal energy of the gas increases by 1500 J. What is the distance through which the piston rises?

Diffusor increases the pressure of a fluid at the expense of its:

A 100 W electric bulb was switched on in a 2.5 m × 3 m × 3 m size thermally insulated room having a temperature of 20°C. The room temperature at the end of 24 hours will be. (Take ​density of air = 1.2 kg/m3 and cv of air = 0.717 kJ/kg.

Constant volume process is

A gas is compressed in a frictionless piston from an initial state of y m3 and 1 MPa to a final state of 0.2 m3 and 1 MPa. There is a transfer of 40 kJ of heat from the gas and a drop of 20kJ in internal energy. What is the initial state volume of the gas?

A mono-atomic ideal gas (γ = 1.67, molecular weight = 40) is compressed adiabatically from 0.1 MPa, 300 K to 0.2 MPa . The universal gas constant is 8.314 kJmol-1K-1. The work of compression of the gas (in kJ kg-1) is

If a gas vapour is allowed to expand through a very minute aperture, then such a process is known as _________.

In a throttling process with negligible change in the potential and kinetic energies:

Isothermal compressibility of an ideal gas is

In a compressor, work is done by:

Correct statement for First law of thermodynamics

Gas laws are least valid in the case of

In a constant volume process, the reversible moving boundary work associated with closed system (in kJ/kg) is:

A container filled with 2 kg of O2 is heated at constant pressure from 27°C to 127°C. The heat supplied in this process is:

A 100 W electric bulb was switched on in a 2.5 m × 3 m × 3 m size thermally insulated room having a temperature of 20°C. The room temperature at the end of 24 hours will be. (Take density of air = 1.2 kg/m3 and cv of air = 0.717 kJ/kg.