Heat Transfer / Thermo Flashcards
another term for momentum diffusivity
kinematic viscosity, m^2/s
heat transfer through physical contact
conduction
heat transfer due to movement of fluid (gas/ liquid)
convection
heat transfer due to electromagnetic waves
radiation
Under the same temperature gradient across various metal plates of the same thickness, the heat conducted per unit of surface area will be largest across
copper
If a man touches two metals which are kept together at room temperature, why would one metal feel colder than the other?
One has a high thermal conductivity
The insulation ability of an insulator with the presence of water would
Decrease
is the change in temperature of a gas when it undergoes isenthalpic expansion.
Joule Thomson Effect
__________ explains the equilibrium constant for any chemical reaction.
Law of mass action
If the vapour pressure at two
temperatures of a solid phase in equilibrium with its liquid phase are known, then the latent heat of fusion can be calculated by the
Clayperon-Claussius equation
Temperature scales with ratios that depend on ratios of heat transfer between a reversible heat engine and the reservoirs.
Absolute temperature scales
Gibbs-Duhem equation relates composition in liquid phase and the __________ at constant temperature & pressure.
-fugacity
-partial pressure
-activity co-efficient
“The rate at which a substance reacts is proportional to its active mass and the rate of a chemical reaction is proportional to the product of active masses of the reacting substances”. This is the
Law of Mass Action
(none of these and sagot)
The change in __________ is equal to the reversible work for compression in steady state flow process under isothermal condition.
Gibbs free energy
A nozzle is a device, which
increases kinetic energy and decreases pressure.
For any closed system formed from known amounts of prescribed chemical species, the equilibrium state is completely determined when any two independent variables are fixed.
Duhem’s theorem
Lee/Kesler correlation is only applicable for the following compound
non-polar and slightly polar
It is a liquid that does not flow at all until a threshold shear stress is attained.
Bingham plastic
The work done in a free expansion process is
Zero
Reaction conversion increases with an increase in temperature in the
Reversible endothermic
Potential flow is the flow of
Incompressible fluids with no shear
With increase in molecular weight of the gas, the head developed by a centrifugal compressor will ___
decrease
Pressure drop is proportional to the 1st power of the velocity
Laminar flow
Closed system that produce the maximum work?
Reversible cyclic process
How to calculate non reversible entropy?
Entropy is state function. S,rev = S,irrev
Gibbs Free Energy
(Proponent, Equation, Definition)
Josiah Willard Gibbs
G=H-TS
Maximum work by system at P&T=k
miles to ft
1 mi = 5280 ft
If a heat transfer equipment, dirt or scale may be accounted by introducing resistance called ______
fouling factors
thermal conductivity of steel, ka
45W/m-K
26 BTU/hr-ft-F
The number of degrees of freedom for an azeotropic mixture in a two component vapour-liquid equilibria is/are
A zero
B one
C two
D three
zero
What is the value of ln y (where y = activity co-efficient) for ideal gases ?
A Zero
B Unity
C Infinity
D Negative
Zero
The number of degrees of freedom for an azeotropic mixture in a two component vapour-liquid equilibria is/are
one
Any substance above its critical temperature exists as
A saturated vapour
B solid
C gas
D liquid
gas
Which of the following decreases with increase in pressure ?
A Melting point of ice
B Melting point of wax
C Boiling point of liquids
D none of these
Melting point of ice
(1) is the mathematical expression
co-efficient of thermal expansion.
In case of steady flow compression polytropic process (PVn = constant), the work done on air is the lowest, when
A n = y = 1.4
B n = 0
C n = 1
D n = 1.66
n = 1
A liquid under pressure greater than its vapour pressure for the temperature involved is called a __________ liquid.
A subcooled
B saturated
C non-solidifiable
D none of these
subcooled
For a real gas, the chemical potential is given by
A RT dlnP
B RT dlnf
C R dlnf
D none of these
RT dlnf
At absolute zero temperature, all substances have the same
A heat capacity
B crystalline structure
C entropy
D none of these
heat capacity
Lowering of condenser temperature (keeping the evaporator temperature constant) in case of vapour compression refrigeration system results in
A increased COP.
B same COP.
C decreased COP.
D increased or decreased COP ; depending upon the type of refrigerant.
increased COP.
Pick out the correct statement.
A If an insoluble gas is passed through a volatile liquid placed in a perfectly insulated container, the temperature of the liquid will increase.
B A process is irreversible as long as Δ S for the system is greater than zero.
C The mechanical work done by a system is always equal to P.dV.
D The heat of formation of a compound is defined as the heat of reaction leading to the formation of the compound from its reactants.
The heat of formation of a compound is defined as the heat of reaction leading to the formation of the compound from its reactants.
Grams of butane (C4H10) formed by the liquefaction of 448 litres of the gas (measured at (STP) would be
A 580
B 640
C 1160
D data insufficient; can’t be computed
The thermodynamic law, PVy = constant, is not applicable in case of
A ideal compression of air.
B free expansion of an ideal gas.
C adiabatic expansion of steam in a turbine.
D adiabatic compression of a perfect gas.
free expansion of an ideal gas.
Mollier diagram is a plot of
entropy vs. enthalpy
is the mathematical expression for
none of these
The activity of an ideal gas is numerically __________ its pressure.
equal to
Specific heat of a gas for a reversible adiabatic process is
A negative
B zero
C infinity
D none of these
zero
When a gas in a vessel expands, its internal energy decreases. The process involved is
A reversible
B irreversible
C isothermal
D adiabatic
reversible
A system is said to be isopiestic, if there is no __________ change.
pressure
In a turbine, the fluid expands almost
A isothermally
B isobarically
C adiabatically
D none of these
adiabatically
The unity of Planck’s constant ‘h’ in the equation, E = hv is
J*S
Refrigeration capacity of a household refrigerator may be round about __________ tons.
0.15
1.5
4.5
6.5
0.15
An ideal gas is taken around the cycle ABCA as shown in P-V diagram below :The work done by the gas during the cycle is equal to
A 12 P1V1
B 6 P1 V1
C 3 P1V1
D P1 V1
3 P1V1
In polytropic process (PVn = constant), if n = 1; it means a/an __________ process.
isothermal
The melting point of paraffin wax (which contracts on solidification) __________ with pressure rise.
increases
A solid metallic block weighing 5 kg has an initial temperature of 500°C. 40 kg of water initially at 25°C is contained in a perfectly insulated tank. The metallic block is brought into contact with water. Both of them come to equilibrium. Specific heat of block material is 0.4 kJ.kg^-1. K^-1. Ignoring the effect of expansion and contraction and also the heat capacity to tank, the total entropy change in kJ.kg^-1 , K^-1 is
0
dW and dq are not the exact differential, because q and W are
A state functions
B path functions
C intensive properties
D extensive properties
path functions
Activity co-efficient is a measure of the
A departure from ideal solution behaviour.
B departure of gas phase from idea] gas law.
C vapour pressure of liquid. D none of these.
departure from ideal solution behaviour.
While dissolving a gas into a liquid at a constant temperature, the ratio of the concentration of the gas in the solution phase and in the gaseous phase is
constant
For an isothermal reversible compression of an ideal gas
A only ΔE = 0
B only ΔH =0
C ΔE = ΔH = 0
D dQ = dE
ΔE = ΔH = 0
Melting of ice exemplifies a/an
A adiabatic process.
B endothermic reaction.
C exothermic reaction.
D process involving a chemical reaction.
endothermic reaction.
Kopp’s rule is used to calculate the heat capacity of
solids
__________ explains the equilibrium constant for any chemical reaction.
Law of Mass Action
Pick out the wrong statement.
A A closed system does not permit exchange of mass with its surroundings but may permit exchange of energy.
B An open system permits exchange of both mass and energy with its surroundings.
C The term microstate is used to characterise an individual, whereas macro-state is used to designate a group of micro-states with common characteristics.
D none of the above.
none of the above.
Requisites of a reversible process is that the
A system and surroundings pressure be equal.
B friction in the system should be absent.
C system and surroundings temperature be equal.
D none of these.
B friction in the system should be absent.
The energy of activation of exothermic reaction is
A zero.
B negative.
C very large compared to that for en-dothermic reaction.
D not possible to predict.
D not possible to predict.
Pick out the wrong statement.
A The chemical potential of a pure substance depends upon the temperature and pressure.
B The chemical potential of a component in a system is directly proportional to the escaping tendency of that component.
C The chemical potential of ith species (μi) in an ideal gas mixture approaches zero as the pressure or mole fraction (xi) tends to be zero at constant temperature.
D The chemical potential of species ‘i’ in the mixture (μi) is mathematically represented as, (1) , where, n, ni and nj respectively denote the total number of moles, moles of ith species and all mole numbers except ith species. ‘G’ is Gibbs molar free energy.
C The chemical potential of ith species (μi) in an ideal gas mixture approaches zero as the pressure or mole fraction (xi) tends to be zero at constant temperature.
In the reaction; N2 + O2 (1) 2NO, increasing the pressure will result in
A shifting the equilibrium towards right,
B shifting the equilibrium towards left.
C no change in equilibrium condition.
D none of these.
no change in equilibrium condition.
Joule-Thomson effect i.e., a throttling process is a constant __________ process.
A entropy
B temperature
C internal energy
D enthalpy
D enthalpy
The number of degree of freedom for an azeotropic mixture of ethanol and water in vapour-liquid equilibrium, is A 3
B 1
C 2
D 0
