Download ME 2322 – Thermodynamics I PRE-LECTURE Lesson 14 Complete

ME 2322 – Thermodynamics I
PRE-LECTURE
Lesson 14
Complete the items below
Name:_________________________
1.
(10pt) Volume flow rates can be converted to mass flow rates by multiplying/dividing the
volume flow rate by the substances’ specific volume.
2. (10 pt) When using a fluid velocity to calculate flow rates, you must use the velocity component
perpendicular to the flow area.
3. (10pt) When the fluid area-average specific volume and velocity are used, the mass flow rate is
given by:
4. (15 pt) The conservation of mass equation for an open system with multiple inlets and outlets is
written as:
5.
(15 pt) The general equation for the mass flow rate is:
6. (15 pt) The integral form of the conservation of mass is written as:
7. (10 pt) The term
physically represents the rate at which mass is accumulated in the
system.
8. (10 pt) The term
physically represents the rate at which mass enters the system.
9. (5 pt) When mass flows into a system and not out, the mass contained in the system must
increase with time.
ME 2322 – Thermodynamics I
PRE-LECTURE
Lesson 15
Complete the items below
Name:_________________________
1.
(5pt) Fluid properties in a steady-state system can change with location, but not with time.
2. (5 pt) Uniform (one-dimensional) flow implies that fluid properties are the same/different across
any inlets or outlets for a steady-flow system.
3. (10pt) The mass balance for a uniform-flow, single-stream steady-state system can be written as
A1V1 /v1 = A2V2 /v2? True/false
4. (10 pt) In a steady-state system, all changes with time are zero.
5. (15 pt)Incompressible oil enters a nozzle with velocity V1 and area A1. It leaves through an area
that is ½ the size of A1. The oil velocity at the exit is double that at the entrance.
6. (15 pt)Incompressible oil enters a nozzle with velocity V1 and area A1. It leaves through an area
that is three times the size of A1. The oil velocity at the exit is 1/3 that at the entrance.
7. (15 pt) A commercial salad dressing mixer mixes 2000 kg/hr of water with 800 kg/hr of canola
oil. What is the rate of salad dressing production in kg/min? 46.7 kg/min
8. (15 pt) The mass balance for a steady-state system with multiple inlets and outlets is written as:
9. (10 pt) Subcooled liquid water (v = 0.001 m3/kg) enters a system with a volume flow rate of 25
m3/s. What is the mass flow rate at this entrance? 25,000 kg/s
ME 2322 – Thermodynamics I
PRE-LECTURE
Lesson 16
Complete the items below
Name:_________________________
1. (15 pt) Flow work represents the work required to move fluid across an open-system boundary.
2. (5 pt) The equation for the flow work is:
3.
(10 pt) Enthalpy is the sum of the internal energy and flow work.
4.
(15 pt) The rate at which energy is transported through an opening in a uniform-flow opensystem is given by:
5. (15 pt) Energy can be transferred into (out of) a steady-flow system by heat, work, and mass.
6.
(15 pt) The first law for a steady-flow system can be written in rate form as:
7. (15) The first law reduces to:
For a steady-state, single-stream system on a per unit mass basis and negligible kinetic and
potential energies.
8. (5 pt) The symbol
9. (5 pt) the symbol
represents power.
represents rate of heat transfer.f
ME 2322 – Thermodynamics I
PRE-LECTURE
Lesson 17
Complete the items below
Name:_________________________
1. (10 pt) The process experienced by the stream passing though a pipe or duct is a constant
pressure process.
2. (10 pt) The first law for a multi-stream mixing chamber must be written on a per unit mass/rate
basis.
3. (10 pt) The first law for a pipe or duct can be written on either a rate or per unit mass basis.
4. (20 pt) Write the general first law equation below.
5.
(5 pt) Per unit mass (i.e., specific) quantities can be converted to rate quantities in open
systems by multiplying them by the mass flow rate.
6.
(10 pt) According to the first law, nozzles increase kinetic energy while decreasing enthalpy of a
fluid.
7. (10 pt) Diffusers do not transfer heat or work.
8. (15 pt) Turbines are adiabatic machines that produce work by decreasing the enthalpy of the
working fluid as it passes through the turbine.
9. (5 pt) The kinetic and potential energies of a turbine can typically be neglected.
10. (10 pt) Compressors decrease/increase the specific volume of the working fluid by applying
work to it.
11. (5 pt) What working fluid property remains constant throughout a throttling device? enthalpy
12. (5 pt) What working fluid property decrease as it passes through a throttle device? pressure
13. (5 pt) What property remains constant in a mixing device? pressure
14. (5 pt) The pressure of each stream in heat exchanger does not change? True/False
15. (10 pt) Heat exchangers can be modeled as either a multi-stream device or as two single-stream
devices.
16. (5 pt) The two streams of a heat exchanger do not intermix? True/False.
17. (5 pt) The two streams of a heat exchanger must be the same fluid? True/False
18. (10 pt) The process experienced by the streams passing though a heat exchanger is a constant
pressure process.
19. (10 pt) Write the general energy balance equation below.
20. (10 pt) Both the energy and mass balance must be satisfied for all thermodynamic systems.
21. (10 pt) When an initially empty rigid tank is filled from a constant fluid property source, the final
specific internal energy of the fluid in the tank must equal the specific enthalpy of the source.
22. (10 pt) In order to maintain the temperature constant while empting a rigid container, you must
add work and/or heat.
ME 2322 – Thermodynamics I
PRE-LECTURE
Lesson 18
Complete the items below
Name:_________________________
1. (10 pt) What working fluid property remains constant throughout a throttling device?
ENTHALPY
2.
(10 pt) What working fluid property decreases as it passes through a throttle device? pressure
3. (10 pt) What property remains constant in a mixing device? pressure
4. (10 pt) The pressure of each stream in heat exchanger does not change? True/False
5. (10 pt) Heat exchangers can be modeled as either a __multi_________-stream device or as two
__single_________________-stream devices.
6. (5 pt) The two streams of a heat exchanger do not intermix? True/False.
7. (5 pt) The two streams of a heat exchanger must be the same fluid? True/False
8.
(10 pt) The process experienced by the streams passing though a heat exchanger is a constant
__pressure_________________ process.
9.
(10 pt) Both the __energy_____________ and ____mass____________ balance must be
satisfied for all thermodynamic systems.
10. (10 pt) When an initially empty rigid tank is filled from a constant fluid property source, the final
specific internal energy of the fluid in the tank must equal the specific enthalpy of the source.
11. (10 pt) In order to maintain the temperature constant while empting a rigid container, you must
add work and/or heat.
ME 2322 – Thermodynamics I
PRE-LECTURE
Lesson 19
Complete the items below
Name:_________________________
1. (10 pt) A thermal energy reservoir can transfer heat without changing its temperature.
2. (5 pt) A thermal energy reservoir from which heat is removed is called a source reservoir.
3. (5 pt) A thermal energy reservoir to which heat is added is called a sink reservoir.
4. (5 pt) The second law is a consequence of the fact that processes only occur in certain
directions.
5.
(5 pt) Is it possible to operate a heat engine without any heat rejection? No
6.
(15 pt) Write the Kelvin-Planck statement of the second law below:
It is impossible for any device that operates in a cycle to receive heat from a single reservoir and
produce a net amount of work.
7. (15 pt) Write the Clausius statement of the second law below:
It is impossible for any system to operate such a way that the sole result would be an energy
transfe by heat from a cooler to a hotter body
8. (5 pt) The Kelvin-Planck statement limits the thermal efficiency to less than 100%.
9. (5 pt) A refrigerator or heat pump rejects heat to a high-temperature energy reservoir.
10. (5 pt) The desired output of a refrigerator is Ql while that of a heat pump is Qh.
11. (10 pt) Write the definition of a reversible process below.
a process that can be reversed without leaving any trace in the surroundings
12. (15 pt) List 3 things that make a process irreversible below.

Friction

Unrestrained expansion

Heat transfer over a finite temperature difference
ME 2322 – Thermodynamics I
PRE-LECTURE
Lesson 20
Complete the items below
Name:_________________________
1.
(10 pt) Write the entropy statement of the second law below:
It is impossible for any system to operate in a way that destroys entropy
2. (10 pt) Write the two second law corollaries below:

The thermal efficiency of any heat engine is always less than that of all reversible
engines operating between the same reservoirs

All reversible engines operating between the same reservoirs have the same thermal
efficiency
3. (10 pt) Write the equation for the thermal efficiency of a heat pump in terms of the heat
transfers below:
4. (10 pt) Write the equation for the thermal efficiency of a refrigerator in terms of the heat
transfers below:
5. (10 pt) Write the relationship between the COPs below.
6. (10 pt) The coefficient of performance of an actual refrigerator must be less than or equal to
that of an equivalent Carnot refrigerator.
7. (5 pt) Is there any limit of the values of the COPs? No
8.
(5pt) Some of the work produced by a heat engine is consumed internally by the heat engine.
9.
(15 pt) Write the first law as applied to a heat engine below:
10. (15 pt) Write the equation for the thermal efficiency of a heat engine in terms of the heat
transfers below:
ME 2322 – Thermodynamics I
PRE-LECTURE
Lesson 21
Complete the items below
Name:_________________________
1. (10) The thermal efficiency of a heat engine can never exceed 100%.
2. (15 pt) Write the relationship between heat transfers and thermodynamic temperature for a
reversible heat engine below.
3. (5 pt) The International Temperature scale agrees/disagrees with the thermodynamic
temperature scale.
4. (20 pt) Write the second law corollaries for heat pumps below:
(A) The COP is always less than that of an equivalent reversible heat pump
(B) All reversible heat pumps operating between the same two thermal reservoirs have the
same COP
5. (10 pt) A reversible heat engine uses two thermal reservoirs at 500 K and 300 K. Heat is added
to this engine at a rate of 100 kW. What is the rate at which this engine rejects heat? 60 kW
6. (10 pt) A reversible heat pump uses two thermal reservoirs at 500 K and 300 K. Heat is added to
this heat pump at a rate of 100 kW. What is the rate at which this heat pump rejects heat? 167
kW
7. (5 pt) There is no upper limit on the COP of a heat pump? True/false
8. (5 pt) There is no upper limit on the COP of a heat engine? True/false
9. (5 pt) All heat engines that use the same thermal reservoirs have the same thermal efficiency?
True/false
10. (5 pt) All heat pumps that use the same thermal reservoirs have the same thermal efficiency?
True/false
11. (10 pt) Heat is added to a reversible heat engine at a rate of 1 MW from a thermal reservoir
whose temperature is 900 K. If this engine rejects heat at a rate of 300 kW, what is the
temperature of the thermal sink? 300 K
ME 2322 – Thermodynamics I
PRE-LECTURE
Lesson 22
Complete the items below
Name:_________________________
1.
(10 pt) What is the upper limit on the thermal efficiency of a heat engine whose energy
reservoirs are at 427 oC and 27 oC? 57%
2. (15 pt) The problem with many alternative energy proposals is with the quality of the energy.
3. (15 pt) Write the equation for the thermal efficiency of a reversible heat engine in terms of the
reservoir temperatures below.
4. (10pt) The coefficient of performance of an actual heat pump must be less than or equal to that
of an equivalent Carnot heat pump.
5. (20 pt) You wish to use a heat pump to heat a house (T = 72 oF) using ground water (T = 50 oF) as
a thermal reservoir. What is the maximum COP you can achieve? 24.2
6. (10 pt) The actual heat pump COP of question 5 less than/greater than/equal to the number you
calculated.
7. (10 pt) Irreversibilities cause the performance index of cyclic devices to be less than that of
equivalent reversible devices.
8. (10 pt) It is possible to create a cyclic device which receives heat from a thermal reservoir and
only produces work. True/false
ME 2322 – Thermodynamics I
PRE-LECTURE
Lesson 23
Complete the items below
Name:_________________________
1. (10 pt) Write the equation for the thermal efficiency of a Carnot heat engine below:
  1
TL
TH
2. (10 pt) Can the thermal efficiency of an actual engine ever exceed that of an equivalent Carnot
engine? Yes/no
3. (10 pt) Write the equation for the COP of Carnot refrigerator below:
TL
TH  TL
CO Pr 
4.
(10 pt) Write the equation for the COP of a Carnot heat pump below.
COPhp 
5.
TH
TH  TL
(20pt) List the completely reversible processes of a Carnot cycle below:
(A) Isothermal expansion
(B) Adiabatic expansion
(C) Isothermal compression
(D) Adiabatic compression
6.
(10 pt) Write the inequality of Clausius below:

Q
T
0
7. (5 pt) The inequality of Clausius is consistent with the Kelvin-Planck statement of the Second
Law.
8. (15 pt) Write the inequality of Clausius for an internally reversible cycle below.

Q
T
9. The
0
of an actual heat engine must be positive/zero/negative.