Midterm 1 Flashcards
Sign convention is that Qin and Wout are
positive
Brouwers Rules:
Rule 6
Ethics
Fundamental cannons of engineering ethics
- hold paramount the safety, health, and welfare of the public
- build their reputation on the merit of their services, shall not compete unfairly with others
- be faithful agents or trustees, avoid conflicts of interest
- objective and truthful
- consider environmental impacts
Closed system
No transfer of mass
Open system
region of space through which mass flows
Change in energy of closed system
ΔE=ΔU+ΔKE+ΔPE
W>0 means work is done ____ the system
by
Q>0 means heat transfer ___ the system
to
Rankine Cycle Model
Rankine Cycle
Turbine Work Equation
Rankine Cycle
Condenser Heat Transfer Eq
Rankine Cycle
Pump Work Eq
Rankine Cycle
Boiler Heat Transfer Eq
Rankine Cycle
Thermal Efficiency
Rankine Cycle
Back Work Ratio
Rankine Cycle Processes
1-2
2-3
3-4
4-1
Rankine Cycle Ideal
TS Diagram
Rankine cycle
Increasing Boiler pressure (increases or decreases) thermal efficiency?
What is the TS diagram?
Increase
Rankine Cycle
Decreasing compressor pressure (increases or decreases) thermal efficiency?
What is the TS diagram?
Increases
Rankine cycle
Isentropic efficiency turbine
Rankine Cycle
Isentropic Pump Efiiciency
Rankine Cycle
Most significant source of irreversibility
combustion
Rankine Cycle
What is superheat?
Adding heat to vapor before entering the turbine so that the vapor is supereated
Rankine Cycle
The superheater in the cycle is a ___ and the combination of the boiler and superheater is called a ______.
heat exchanger
steam generator
Rankine Cycle
Using a superheater ____ the thermal efficiency. It also ____ the quality at the turbine exit.
increases
increases
Rankine Cycle
With reheat, a power plant can take advantage of ____ efficiency that results from ____ boiler pressure and avoid ____ quality steam at the turbine exit.
increased
higher
low
Rankine Cycle
Advancements in materials have allowed for power plants to operate with steam generator pressures exceeding the critical pressure of water. These plants are called _____ vapor power plants.
Supercritical.
Rankine Cycle
Ideal reheat diagram
Rankine Cycle
Ideal Reheat TS Diagram
Rankine Cycle
Supercritical TS Diagram
Rankine Cycle
During regeneration, the average temperature of heat addition is ____, thereby tending to ____ the thermal efficiency.
increased
increase
Rankine Cycle
An open feedwater heater is
a type of direct contact heat exchanger in which streams at different temperatures mix to foorm a stream at an intermediate temperature
Rankine Cycle
A source of irrevirsibility with open feedwater heaters is in ____.
mixing
Rankine Cycle
With open feedwater heaters, the amount of energy to vaporize or superheat steam is ____, resulting in ____ thermal efficiency.
reduced
increased
Rankine Cycle
Closed feedwater heaters are shell-and-tube type recuperators in which the feedwater temperature _______ as the extracted steam condenses on the outside of the tubes carrying the feedwater.
increases
Rankine Cycle
Open feedwater heater diagram
Rankine Cycle
Open feedwater heater TS diagram
Rankine Cycle
Closed Feedwater heater diagram
Rankine Cycle
Closed feedwater heater TS diagram
Rankine Cycle
Cogeneration systems are
integrated systems that simultaneously yield two valuable products- electricity and steam- from a single fuel input.
Rankine Cycle
Regenerative vapor power cycle w open feedwater heater
Equations for turbine, pump, steam generator, and condenser
Rankine Cycle
y for open feedwater heater
Rankine Cycle
y for closed feedwater heater
Deaeration is
a process of purifying the working fluid in a multiple-feedwater-heater system to prevent corrosion ( heater operating at P> Patm so that oxygen and other dissolved gasses can be vented)
________ is used as the working fluid in the vast majority of vapor power systems
demineralized water
Organic Rankine Cycles employ _____ as working fluids due to their relatively low boiling points, allowing for low-temp power production
organic substances like hydrocarbons, refrigerants, ammonia, and silicon oiol
Gas Power Systems
Compression Ratio is defined as
the volume of the dead center divided by the volume at the top dead center
Gas Power Systems
Two principle types of reciprocating internal combustion engines are
Spark-ignition engine
compression-ignition engine
in a spark ignition engine, a mixture of ____ and ____ is ignited by a _____.
fuel
air
spark plug
In a compression ignitioin engine, ____ is compressed to a high enough temperature and pressure that _____ occurs spontaneously when fuel is injected
air
combustion
In engines, the mean effective pressure is
the theoretical constant pressure that, when acted on by a piston during the power stroke, would produce the same net work as actually developed in one cycle
mep=
(net work for one cycle) / (displacement volume)
Which energy variables should be used for first law analysis of the “open” (control volume, CV) and “closed” (control mass) thermodynamic cycles?
Enthalpy (H) for open systems and internal energy (U) for closed systems
Which of the following statements is not true?
Entropy of a working fluid undergoing a process within a system can only increase.
The figure below shows p-v diagram for Carnot cycle. Which one of the following processes are incorrectly matched with what is happening during the process?
Process 3-4: Adiabatic Expansion
None of the above
Process 4-1: Isothermal Compression
Process 1-2: Adiabatic Compression
Process 2-3: Isothermal Expansion
None of the above
Which one of the following options correctly represents the Rankine cycle’s thermal efficiency?
W_net/Q_in
1-(T_cold/T_hot)
1-(Q_out/Q_in)
(h1’-h4)/(h2’-h3)
W_net/Q_in
or
1-(Q_out/Q_in)
Which one of the following is true about Otto and Diesel Cycles?
Assuming the same compression ratio, Otto cycle is more efficient.
Otto cycle is practically more efficient than Diesel cycle
The working fluid of both cycles is a mixture of air and fuel that when analyzing cycles, thermal properties of the mixture have to be accounted for.
Diesel cycle is more efficient because heat addition occurs at constant pressure instead of at constant volume.
Assuming the same compression ratio, Otto cycle is more efficient.
Select all that are true about Air standard assumptions.
The working fluid is air and behaves as an ideal gas.
The exhaust process is replaced by the heat rejection process.
All the process are internally reversible.
“Cold air standard assumptions” is just an another name for Air standard assumptions.
When analyzing the combustion process, the air standard assumptions cannot be applied because they do not account for any fuel-mixing effect.
The working fluid is air and behaves as an ideal gas.
The exhaust process is replaced by the heat rejection process.
All the process are internally reversible.
Otto Cycle
TS Diagram
Diesel Cycle
TS Diagram
Dual Cycle
TS Diagram
Otto Cycle
Process
Brayton cycle
Ideal Shematic
Brayton cycle
TS Diagram ideal
Brayton Cycle
Reheat TS Diagram
Brayton Cycle
Combined Schematic
Brayton Cycle
Regeneration TS Diagram
Brayton Cycle
Reheat and intercooling Schematic
Brayton Cycle
Reheat and intercooling TS Diagram
Brayton Cycle
Regeneration Schematic
Brayton Cycle
Reheat Schematic
Ericsson TS Diagram
Stirling TS Diagram
Jet Engine Schematic
Jet Engine TS Diagram
