ME 3011 Ch 5

Nozzle

A device that increases the velocity of a fluid at the expense of pressure

Mixing chamber

A device where two fluids exchange heat when mixed

Heat exchanger

A device where two fluids exchange heat without mixing

Which of the following devices are considered as mixing chambers?

A T-elbow A Y-elbow A tub with inlets for both hot and cold water and one outlet

Diffuser

A device that increases the pressure of a fluid by slowing it down

Which of the following devices requires work input?

Compressor Pump Fan

In a single-stream, steady flow system, the mass flow rate can be defined as the product of ______, ________, and _______.

Density Velocity Area

Which of the following statements are true regarding throttling valves?

For a single-stream, steady flow throttle valve, the inlet and outlet enthalpies can be approximated to be the same. The flow through a throttle valve may be assumed to be adiabatic. Throttle valves are flow-restricting devices that cause a pressure drop in a fluid.

In the energy balance equation for heat exchangers, which of the following are often neglected? (Select all that apply.)

Heat transfer with entire exchanger as the control volume Δpe w Δke

Which of the following statements are true of the conservation of mass?

In a steady flow process, the total rate of mass entering a control volume is equal to the total rate of mass leaving it. The rate of change of mass within a control volume minus the net flow rate in and plus the net flow rate out of the control surface must equal to zero.

Which of the following statements are true about nozzles and diffusers?

Nozzles and diffusers typically involve no heat transfer. Any change in potential energy in nozzles and diffusers can be neglected. Nozzles and diffusers typically involve no work.

Which of the following energies are part of the total energy of a flowing fluid?

Potential energy Enthalpy Kinetic energy

For a compressor with an intercooler, which of the following energy changes are usually neglected in the energy balance equation?

Potential energy Kinetic energy

Identify the true statements about the steady-flow process.

The steady flow implies that the fluid properties can change from point to point, but at any point, they remain constant during the entire process. During a steady flow process, boundary work is zero. The steady-flow process is a process during which a fluid flows through a control volume and does not change with time.

True or false: Flow work can be expressed in terms of other properties.

True

True or false: In a single-stream, steady flow system, the mass flow rates for the inlet and outlet must be the same.

True

True or false: Since liquid can be considered as incompressible, the volume flow rates into and out of a steady flow device will remain constant.

True

True or false: The total energy for a flowing fluid consists of an additional term when compared with the total energy for a nonflowing fluid.

True

Which of the following statements are true about unsteady flow processes?

Unsteady-flow or transient flow involves changes within the control volume with time, such as charging or discharging problems. Unlike steady flow processes, unsteady flow processes start and end over some finite time period instead of continuing indefinitely. Unsteady flow systems may involve boundary work.

In an open system, when mass flows across control volume boundaries, some work is required to push the mass into or out of the control volume, and this is known as ______ work.

boundary

Refrigerant flow across a throttle valve usually experiences a large pressure drop. This large pressure drop in the refrigerant across a throttle valve usually causes its temperature to ______.

decrease

For a well-insulated mixing chamber, which terms in the energy balance equation can be left out?

q w Δpe Δke

During a steady-flow process, the fluid properties at an inlet or exit must ______.

remain constant

In a steady flow process, the change of total energy of the control volume must ______.

remain zero

If properties are allowed to change within the control volume, the processes are called _______ flow.

unsteady or transient

In a steady flow process, energy can be transferred by ______.

work, mass, and heat