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Ejectors are devices that use a high-pressure fluid to entrain and compress a low-pressure fluid, creating a mixed fluid at an intermediate pressure. Ejectors have many applications in refrigeration, air conditioning, power generation, chemical processing, and aerospace engineering. Ejectors are simple, reliable, and energy-efficient, but they also require careful design and optimization to achieve the desired performance.

In this article, we will provide a guide for engineers who want to learn more about ejector design calculation pdf download. We will explain the basic principles of ejector operation, the different types of ejectors, the main design parameters and criteria, and the methods and tools for ejector design and performance prediction. We will also provide some examples and references for further reading.

## Basic Principles of Ejector Operation

An ejector consists of three main components: a primary nozzle, a mixing chamber, and a diffuser. The primary nozzle converts the high-pressure primary fluid into a high-velocity jet that enters the mixing chamber. The jet creates a low-pressure region that entrains the low-pressure secondary fluid from the suction port. The jet and the secondary fluid mix in the mixing chamber and form a mixed fluid at an intermediate pressure. The mixed fluid then enters the diffuser, where it is decelerated and further compressed to the discharge pressure.

The performance of an ejector is usually characterized by two parameters: the entrainment ratio and the compression ratio. The entrainment ratio is defined as the mass flow rate of the secondary fluid divided by the mass flow rate of the primary fluid. The compression ratio is defined as the ratio of the discharge pressure to the suction pressure. The entrainment ratio and the compression ratio depend on the operating conditions (such as the primary pressure, the suction pressure, and the back pressure) and the geometrical parameters (such as the nozzle area ratio, the ejector area ratio, and the mixing chamber length).

## Different Types of Ejectors

Ejectors can be classified into different types according to various criteria, such as the working fluids, the flow regimes, and the design configurations. Some common types of ejectors are:

• Gas/gas ejectors: These ejectors use gas as both the primary and secondary fluids. They are widely used in gas compression, vacuum pumping, gas recirculation, and gas mixing applications.

• Liquid/liquid ejectors: These ejectors use liquid as both the primary and secondary fluids. They are mainly used in liquid pumping, liquid mixing, and liquid extraction applications.

• Steam/jet ejectors: These ejectors use steam as the primary fluid and water or another liquid as the secondary fluid. They are commonly used in refrigeration, air conditioning, and desalination systems.

• Supersonic ejectors: These ejectors operate in supersonic flow regimes, where both the primary and secondary fluids reach sonic or supersonic velocities. They are typically used in aerospace engineering, such as rocket propulsion and air-breathing engines.

Constant-area mixing ejectors: These ejectors have a constant cross-sectional area in

the mixing chamber,

where

the primary nozzle exit

is located within

the cylindrical part

of

the ejector.

They are simpler

to design

but have lower performance

• than constant-pressure mixing ejectors.

Constant-pressure mixing ejectors: These ejectors have a variable cross-sectional area in

the mixing chamber,

where

the primary nozzle exit

is located in

a suction chamber (usually conical)

in front of

the cylindrical part

of

the ejector.

They have higher performance

but require more complex design

• than constant-area mixing ejectors.

## Main Design Parameters and Criteria

The main design parameters of an ejector are:

The nozzle area ratio: This is defined as

the ratio of

the nozzle exit area

to

the nozzle throat area.

It determines

the expansion ratio

and velocity

of

• the primary jet.

The ejector area ratio: This is defined as

the ratio of

the diffuser exit area

to

the nozzle throat area.

It determines

the compression ratio

and pressure recovery

of

• the mixed fluid.

The mixing chamber length: This is defined as

the distance between

the nozzle exit

and

the diffuser entrance.

It determines

the degree of mixing

and entrainment

of

• the secondary fluid.

The main design criteria of an ejector are:

The critical mode: This is

the operating mode

where

the mixed fluid reaches

the sonic velocity

at

the diffuser entrance.

It represents

the maximum performance

of

the ejector,

as any further increase

in back pressure

will cause

a decrease

in entrainment ratio

• and compression ratio.

The optimum mode: This is

the operating mode

where

the entrainment ratio

is maximized

for a given back pressure.

It represents

the best trade-off between entrainment ratio

and compression ratio,

as any further increase

in back pressure

will cause

a decrease

• in both parameters.

The efficiency: This is defined as

the ratio of

the useful work output

to

the work input

of

the ejector.

It measures

the energy conversion

and loss

of

the ejector.

The efficiency

can be calculated

by different methods,

such as

the exergy analysis,

the entropy generation analysis,

or

• the coefficient of performance analysis.

## Methods and Tools for Ejector Design and Performance Prediction

Ejector design and performance prediction can be performed by various methods and tools,

depending on

Ejectors are devices that use a high-pressure fluid to entrain and compress a low-pressure fluid, creating a mixed fluid at an intermediate pressure. Ejectors have many applications in refrigeration, air conditioning, power generation, chemical processing, and aerospace engineering. Ejectors are simple, reliable, and energy-efficient, but they also require careful design and optimization to achieve the desired performance.

In this article, we will provide a guide for engineers who want to learn more about ejector design calculation pdf download. We will explain the basic principles of ejector operation, the different types of ejectors, the main design parameters and criteria, and the methods and tools for ejector design and performance prediction. We will also provide some examples and references for further reading.

## Basic Principles of Ejector Operation

An ejector consists of three main components: a primary nozzle, a mixing chamber, and a diffuser. The primary nozzle converts the high-pressure primary fluid into a high-velocity jet that enters the mixing chamber. The jet creates a low-pressure region that entrains the low-pressure secondary fluid from the suction port. The jet and the secondary fluid mix in the mixing chamber and form a mixed fluid at an intermediate pressure. The mixed fluid then enters the diffuser, where it is decelerated and further compressed to the discharge pressure.

The performance of an ejector is usually characterized by two parameters: the entrainment ratio and the compression ratio. The entrainment ratio is defined as the mass flow rate of the secondary fluid divided by the mass flow rate of the primary fluid. The compression ratio is defined as the ratio of the discharge pressure to the suction pressure. The entrainment ratio and the compression ratio depend on the operating conditions (such as the primary pressure, the suction pressure, and the back pressure) and the geometrical parameters (such as the nozzle area ratio, the ejector area ratio, and the mixing chamber length).

## Different Types of Ejectors

Ejectors can be classified into different types according to various criteria, such as the working fluids, the flow regimes, and the design configurations. Some common types of ejectors are:

• Gas/gas ejectors: These ejectors use gas as both the primary and secondary fluids. They are widely used in gas compression, vacuum pumping, gas recirculation, and gas mixing applications.

• Liquid/liquid ejectors: These ejectors use liquid as both the primary and secondary fluids. They are mainly used in liquid pumping, liquid mixing, and liquid extraction applications.

• Steam/jet ejectors: These ejectors use steam as the primary fluid and water or another liquid as the secondary fluid. They are commonly used in refrigeration, air conditioning, and desalination systems.

• Supersonic ejectors: These ejectors operate in supersonic flow regimes, where both the primary and secondary fluids reach sonic or supersonic velocities. They are typically used in aerospace engineering, such as rocket propulsion and air-breathing engines.

Constant-area mixing ejectors: These ejectors have a constant cross-sectional area in

the mixing chamber,

where

the primary nozzle exit

is located within

the cylindrical part

of

the ejector.

They are simpler

to design

but have lower performance

• than constant-pressure mixing ejectors.

Constant-pressure mixing ejectors: These ejectors have a variable cross-sectional area in

the mixing chamber,

where

the primary nozzle exit

is located in

a suction chamber (usually conical)

in front of

the cylindrical part

of

the ejector.

They have higher performance

but require more complex design

• than constant-area mixing ejectors.

## Main Design Parameters and Criteria

The main design parameters of an ejector are:

The nozzle area ratio: This is defined as

the ratio of

the nozzle exit area

to

the nozzle throat area.

It determines

the expansion ratio

and velocity

of

• the primary jet.

The ejector area ratio: This is defined as

the ratio of

the diffuser exit area

to

the nozzle throat area.

It determines

the compression ratio

and pressure recovery

of

• the mixed fluid.

The mixing chamber length: This is defined as

the distance between

the nozzle exit

and

the diffuser entrance.

It determines

the degree of mixing

and entrainment

of

• the secondary fluid.

The main design criteria of an ejector are:

The critical mode: This is

the operating mode

where

the mixed fluid reaches

the sonic velocity

at

the diffuser entrance.

It represents

the maximum performance

of

the ejector,

as any further increase

in back pressure

will cause

a decrease

in entrainment ratio

• and compression ratio.

The optimum mode: This is

the operating mode

where

the entrainment ratio

is maximized

for a given back pressure.

It represents

the best trade-off between entrainment ratio

and compression ratio,

as any further increase

in back pressure

will cause

a decrease

• in both parameters.

The efficiency: This is defined as

the ratio of

the useful work output

to

the work input

of

the ejector.

It measures

the energy conversion

and loss

of

the ejector.

The efficiency

can be calculated

by different methods,

such as

the exergy analysis,

the entropy generation analysis,

or

• the coefficient of performance analysis.

## Methods and Tools for Ejector Design and Performance Prediction

Ejector design and performance prediction can be performed by various methods and tools,

depending on