Chapters 1 (THERMODYNAMICS) Flashcards
Enthalpy of an ideal gas is a function only of ________
Temperature
Which of the following is the most efficient thermodynamic cycle?
Carnot
What is the first law of thermodynamics?
Energy can neither be created nor destroyed
An ideal gas is compressed isothermally. What is the enthalpy change?
Zero
Name the process that has no heat transfer.
Adiabatic
An ideal gas is compressed in a cylinder so well insulated that there is essentially no heat transfer. The temperature of the gas
Increases
What is the Sl unit of pressure?
Pascal
The equation Cp = Cv + R applies to which of the following?
Ideal gas
In the flow process, neglecting kinetic and potential energies, the integral of Vp represents what ?
Shaft work
Mechanical energy of pressure transformed into energy of heat.
Enthalpy
The theory of changing heat into mechanical work.
Thermodynamics
Average pressure on a surface when a changing pressure condition exist.
Mean effective pressure
Which of the following cycles consist two isothermal and two constant volume processes?
Stirling cycle
A control volume refers to what?
A fixed region in space
In the polytropic process, PV^n = constant, if the value of n is infinitely large, the process is
Isometric
If the temperature is held constant and the pressure is increased beyond the saturation pressure, then the working medium must be:
compressed liquid
Is one whose temperature is below the saturation temperature corresponding to its pressure
Subcooled liquid
Number of molecules in a mole of any substance is a constant is called
Avogadro’s number
If the pressure of a gas is constant the volume directly proportional to the absolute temperature
Charles’ Law
The number of protons in the nucleus of an atom or number of electrons in the orbit of an atom
Atomic number
In a P-T diagram of a pure substance, the curve separating the solid phase from the liquid phase is:
Fusion curve
A water temperature of 18 °F in the water cooled condenser is equivalent in °C to
10
The latent heat of vaporization in Joules per kg is equal to
22.6 x 10^5
Form of energy associated with the kinetic energy of the random motion of large number of molecules
Heat
If the temperature is held constant and the pressure is increased beyond the saturation pressure, then, the working medium must be:
Compressed liquid
Is the condition of pressure and temperature at which a liquid and its vapor are indistinguishable
Critical Point
When a substance in gaseous state is below the critical temperature, it is called
Vapor
Superheated vapor behaves
Approximately as a gas
Which of the following provides the basis for measuring thermodynamic property of temperature?
Zeroth Law of thermodynamics
Which of the following is commonly used as liquid absorbent
Ethylene glycol
Mechanism designed to lower the temperature of air passing through it.
Air cooler
A device for measuring the velocity of wind.
Anemometer
Heat normally flowing from high temperature body to a low temperature body wherein it is impossible to convert heat without other effects.
Second law of thermodynamics
The temperature at which its vapor pressure is equal to the pressure exerted on the liquid
Boiling point
A nozzle is used to
Increase velocity and decrease pressure
The sum of the energies of all the molecules in a system where energies appear in several complex form.
Internal energy
The total energy in a compressible or incompressible fluid flowing across any section in a pipeline is function of
Flow energy, kinetic energy, height above datum and internal energy
The ratio of the density of a substance to the density of some standard substance
Specific gravity
Is one whose pressure is higher than a saturation pressure corresponding to its temperature
Compressed liquid
The changing of solid directly to vapor without passing through the liquid state is called
Sublimation
Weight per unit volume is termed as
Weight density
What is the S1 unit of force?
Newton
The volume of fluid passing a cross-section of steam in unit time.
Discharge
What equation applies in the first law of thermodynamics for an ideal gas in a reversible open steady-state system?
Q + VdP = H2 – H1
A pressure of 1 millibar is equivalent to
1000 dynes/cm^2
When a system deviates infinitesimally from equilibrium at every instant of its state, it is undergoing:
quasi-static process
What is the force which tends to draw a body toward the center about which it is rotating?
Centripetal force
What is the process that has no heat transfer?
Adiabatic
Which of the engine is used for fighter bombers
Turbojet
Exhaust gases from an engine posses:
Kinetic Energy
A critical point the latent enthalpy of vaporization is
Zero
What is the force which tends to draw a body towards the center about which it is rotating?
Centripetal force
When a system deviates and infinitesimally from equilibrium at every instant of its state, it is undergoing
quasi- static process
Work done per unit charge when charged is moved from one point to another
Potential at a point
How many independent properties are requires to completely fix the equilibrium state of a pure gaseous compound?
2
Which of the following relations defines enthalpy?
h = u + pV
Which of the following is true for water at a reference temperature where enthalpy is zero?
Internal Energy is negative
On what plane is the Mollier diagram plotted?
h-s
The compressibility factor z, is used for predicting the behavior of non - ideal gases. How is the compressibility factor defined relative to an ideal gas? ( subscript c refers to critical value )
z= PV/RT
How is the quality x of a liquid - vapor mixture defined?
The fraction of the total mass that is saturated vapor
What is the expression for heat of vaporization?
hg-hf
What is the value of the work done for a closed, reversible, isometric system?
Zero
What is the equation for the work done by a constant temperature system?
W = MRT In (V2/V1)
What is true about polytropic exponent n for a perfect gas undergoing an isobaric process?
n = 0
How does an adiabatic process compare to an isentropic process?
Both: Heat transfer = 0; Isentropic: Reversible
During an adiabatic, internally reversible process, what is true about the change in entropy?
It is always zero
For an irreversible process, what is true about the change in entropy of the system and surroundings?
ds > 0
For which type of process does the equation dQ = Tds hold?
Reversible
Which of the following is true for any process?
∆S (Surrounding) + ∆S (system) ≥ 0
Which of the following thermodynamics cycle is the most efficient?
Carnot
The ideal reversible Carnot cycle involves four basic processes. What type of processes are they?
Two isothermal and two isentropic
What is the temperature difference of the cycle if the entropy difference ∆S, and they work done is W?
W / ∆S
Which of the following is not an advantage of a superheated, closed Rankine cycle over an open Rankine cycle?
Increased boiler life
Which of the following statements regarding Rankine cycle is not true?
In practical terms, the susceptibility of the engine materials to corrosion is not a key limitation on the operating efficiency
Which one of the following is standard temperature and pressure (STP)
0 °C and 1 atm pressure
A substance is oxidized when which of the following occurs?
it losses electrons
Which of the following is not a unit of pressure?
kg / m-s
Definition of Joule
Newton meter
Which of the following is the basis for Bernoulli’s law for fluid flow?
The principle of conservation of energy
Equation of state for a single component can be any of the following except:
A. the ideal gas law
B. any relationship interrelating 3 or more state functions
C. relationship mathematically interrelating
thermodynamic properties of the material
D.A mathematical expression defining a path between states
A mathematical expression defining a path between states
The state of a thermodynamic system is always defined by its:
properties
In any non quasi-static thermodynamic process, the overall entropy of an isolated system will
increase only
Entropy is the measure of :
randomness or disorder
Which of the following statements about entropy is
Entropy of a crystal at 0 °F is zero
Work or energy can be a function of all of the following except :
force and distance
power and time
force and time
temperature and entropy
force and time
Energy changes are represented by all except which one of the following:
dQ / T
U + pV is a quantity called :
enthalpy
In flow process, neglecting KE and PE changes, JvdP represents which item below?
Shaft work
Power may be expressed in units of
Btu / hr
Equilibrium condition exist in all except which of the following?
In a steady state flow process
In a closed system (with a moving boundary) which of the following represents work done during an isothermal process?
W= P1 V1 ln V2 / V1
A substance that exists, or is regarded as existing, as a continuoum characterized by a low resistance to flow and the tendency to assume the shape of its container.
Fluid
A substance that is homogeneous in composition and homogeneous and invariable in chemical aggregation.
Pure substance
A substance whose state is defined by variable intensive thermodynamic properties.
Simple substance
A system in which there is no exchange of matter with the surrounding or mass does not cross its boundaries.
Closed System
A system that is completely impervious to its surrounding or neither mass nor energy cross its boundaries.
Isolated system
A system in which there is a flow of mass across its boundaries
Open system
The properties that are dependent upon the mass of the system and are total values such as total volume and total internal energy.
Extensive properties
The properties that are independent of the mass of the system such as temperature, pressure, density and voltage.
Intensive properties
The properties for a unit mass and are intensive by definition such as specific volume.
Specific Properties
The condition as identified through the properties of the substance, generally defined by particular values of any two independent properties.
State
The only base unit with a prefix kilo is
kilogram
The force of gravity on the body.
Weight
The mass per unit volume of any substance
Density
The force of gravity on unit volume is
specific weight
The reciprocal of density is
Specific volume
Avogadro’s number, a fundamental constant of nature, is the number of molecules in a gram-mole. This constant is
6.02252 x 10^23
The ratio of the gas constant to Avogadro’s number is:
Boltzmann’z constant
The absolute zero on the Fahrenheit-scale is at
–459.7 °F
Absolute temperatures on the Fahrenheit scale are called:
Degrees Rankine
The absolute zero on the Celsius scale is at
-273.15 °C
What is the absolute temperature in celsius scale?
degrees Kelvine
The Fahrenheit scale was introduced by Gabriel Fahrenheit of amstermdam, Holland in what year?
1720
The Centigrade scale was introduced by Anders Celsius in what year?
1740
The National Bureau of Standards uses, among others, the liquid - vapor equilibrium of Nitrogen at
–196 °C
The liquid - vapor equilibrium of Oxygen is at what temperature?
-182.97 °C
The solid- liquid equilibrium of Mercury is at what temperature?
-38.87 °C
The national Bureau of standards uses, among others, the liquid- vapor equilibrium of hydrogen at
–253 °C
The solid- liquid equilibrium of Tin is at what temperature?
231.9 °C
The solid-liquid equilibrium of Zinc is at what temperature?
419.505 °C
The liquid-vapor equilibrium of sulfur is at what temperature?
444.60 °C
The solid-liquid equilibrium of Antimony is at what temperature?
630.5 °C
The solid liquid equilibrium of silver is at what temperature?
960.8 °C
the solid-liquid equilibrium of Gold is at what temperature?
1063 °C
The solid-liquid equilibrium of Platinum is at what temperature?
1774 °C
The solid-liquid equilibrium of Tungsten is at what temperature!
3370 °C
The device that measures temperature by the electromotive force.
thermocouple
The emf is a function of the temperature difference between the junction, a phenomenon called :
Seebeck effect
A device that measure temperature by the electromotive force called thermocouple was discovered by :
Seebeck
When two bodies, isolated from other environment, are in thermal equilibrium with a third body, the two are in thermal equilibrium with each other.
Zeroth law of thermodynamics
The total entropy of pure substances approaches zero as the absolute thermodynamic temperature approaches zero.
Third law of thermodynamics
If any one or more properties of a system change, the system is said to have undergone a
process
