18 Questions
What is the main function of a nozzle?
Increasing the velocity of a fluid
Which device slows down a fluid to increase its pressure?
Diffuser
In which direction does a turbine produce work?
Against the blades
What type of device is a compressor?
Work consuming
Which statement is true about the enthalpy of an ideal gas?
It depends on temperature only
What characteristic does a diffuser have in terms of fluid velocity and pressure?
Decreases velocity, increases pressure
What term is used to describe the work required to push mass into or out of an open system?
Flow work
In the context of flowing fluids, what does 'emass' denote?
Total energy per unit mass of a flowing fluid
Which term refers to the energy transported by mass through an inlet or exit in an open system?
Total energy per unit mass
What is the specific term used to describe the amount of work done in pushing a fluid element across the boundary in an open system?
Flow energy per unit mass
Which type of engineering devices operate under similar conditions for extended periods of time?
Steady-flow devices
What is the term for the specific energy associated with the motion of particles in a flowing fluid?
Specific kinetic energy
What happens to the internal energy of the fluid if it initially was 800 kJ and loses 500 kJ of heat during the cooling process while 100 kJ of work is done by the paddle wheel on the fluid?
It decreases by 700 kJ
How does the area under a process curve on a P-V diagram relate to work done?
It represents the boundary work done
In which type of process does temperature remain constant?
Isothermal process
What does the boundary work represent in a gas expansion or compression process?
Work done on/by the gas
Which property remains constant during an isothermal compression of an ideal gas?
Temperature
In a polytropic process for gases, how are pressure and volume typically related?
$P = CV^n$
Study Notes
Nozzles and Diffusers
- Nozzles increase the velocity of a fluid at the expense of pressure
- Diffusers increase the pressure of a fluid by slowing it down
- Both are commonly used in jet engines, rockets, spacecraft, and even garden hoses
Turbines and Compressors
- Turbines are work-producing devices that drive electric generators in power plants
- As fluid passes through a turbine, work is done against the blades, causing the shaft to rotate and produce work
- Compressors, pumps, and fans are devices used to increase the pressure of a fluid, involving work inputs
- Compressors are work-consuming devices
Open Systems and Flow Work
- Open systems involve mass flow across their boundaries, requiring work to push mass into or out of the system
- This work is known as flow work or flow energy
- Flow energy per unit mass is calculated as the work done to push a fluid element across the boundary, divided by the mass of the fluid element
- Total energy of a flowing fluid per unit mass includes kinetic energy, potential energy, and flow energy
First Law of Thermodynamics for Open Systems
- Energy transport by mass is calculated as the sum of the energy transported by mass through inlets and exits
- Energy balance for open systems accounts for energy transported by mass and energy transferred by heat and work
- Steady flow energy equation is used to analyze engineering devices that operate at steady-state conditions
Steady-Flow Engineering Devices
- Many engineering devices operate under steady-state conditions, including nozzles, diffusers, turbines, compressors, throttling valves, and mixing chambers
Explore the functions of nozzles and diffusers commonly used in jet engines, rockets, spacecraft, and more. Understand how nozzles increase fluid velocity at the expense of pressure, while diffusers increase pressure by slowing down the fluid.
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