Question

In: Physics

true or false: 1. A flow idealized as a throttling process through a device has h1...

true or false:

1. A flow idealized as a throttling process through a device has h1 < h2 and p1 < p2

2. Steady flow devices that result in a drop in working fluid pressure from inlet to exit are nozzle, turbine, pump, throttling device.

3. Mass flow rate for a flow modeled as one-dimensional depends on a density of working fluid, cross-sectional area through which flow passes, velocity of working fluid, and total volume of working fluid.

4. The mechanisms of energy transfer for a control volume are total energy, enthalpy, and work.

5. Flow work is the work associated with the fluid pressure as mass is introduced at inlets and removed at exits in addition to the work done on a flowing stream by a paddle wheel or piston.

6. Transient operation denotes a change in state with time and elevation.

7. Usually, there are no compressors found within households.

8. When a hair dryer (diffuser) on-off switch is turned to the on position, the hair dryer is in transient operation.

9. An automobile’s radiator is an example of a cross-flow heat exchanger.

10. Wind turbines and hydraulic turbines develop mechanical power from moving streams of air and water, respectively. While wind turbine uses the kinetic energy of flowing stream for power generation, hydraulic turbine uses potential energy of flowing stream for power generation.

Solutions

Expert Solution

1.FALSE.

Explanation: h2=h1 and p1>p2 as it is Isenthalpic process but the pressure reduces.

2.FALSE.

Explanation: Steady flow devices that result in a drop in working fluid pressure from inlet to exit are nozzle, turbine and throttling device. Pump on the other hand does work on the liquid to increase the pressure.

3.FALSE.

Explanation:Mass flow rate for a flow modeled as one-dimensional depends on a density of working fluid, cross-sectional area through which flow passes, velocity of working fluid but NOT on total volume of working fluid.Because the flow rate is defined as product of area and velocity by specific volume.

hence, it doesn't depend on volume of working fluid.

4.TRUE.

Explanation: The mechanisms of energy transfer for a control volume are total energy, enthalpy(heat), and work.

5.TRUE.

Explanation: Work is needed to push the fluid into or out of the boundaries of a controlled volume if mass flow is involved. This work is called flow work.

6.TRUE.

Explanation: A system is said to be in Transient state when process variable have been changed and the system has not yet reached a steady state.Thus it denotes change in state with time and elevation.

7.FALSE.

Explanation: Refrigeration and air conditioner equipments use compressors to move heat in refrigerant cycles.

8.FALSE.

Explanation: When a hair dryer (diffuser) on-off switch is turned to the on position, the hair dryer will be in steady state.

9. TRUE.

Explanation: An automobile’s radiator is an example of a cross-flow heat exchanger as radiator is a type of heat exchanger. It is designed to transfer heat from hot coolant that flows through it to the air blown through it by the fan.

10.TRUE.

Explanation: wind turbine uses the kinetic energy of flowing stream for power generation, hydraulic turbine uses potential energy of flowing stream for power generation.

genius_generous answered 1 year ago

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