CONTEMPORARY COOLING TECHNOLOGIES

STEAM JET COOLING SYSTEM

Submitted by BUSHRA ZAIDI

SHABINA YASMIN

M.ARCH - Ist SEMESTER (Building Services)

Guided by

AR. MOHD FIROZ ANWAR

FACULTY OF ARCHITECTURE & EKISTICS

JAMIA MILLIA ISLAMIA

NEW DELHI-110025

INTRODUCTION

Steam jet cooling system is a cooling technique which

involves usage of steam and water for cooling purposes.

In steam jet refrigeration systems, water can be used as

the refrigerant. Like air, it is perfectly safe. These systems

were applied successfully to refrigeration.

• Temperatures attained using water as a refrigerant are

in the range which may satisfy air conditioning,

cooling, or chilling requirements.

• Mostly low-grade energy and relatively small amounts

of shaft work.

• This system are the utilization of mostly low-grade

energy and relatively small amounts of shaft work.

• Not used when temperatures below 5°C are required.

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WHY UNCONVENTIONAL?

Steam jet cooling system is preferable over conventional cooling system

because:-

• Employs a steam injector or booster instead of mechanical compressor to

compress the refrigerant to the required condenser pressure level.

• Water is used as the refrigerant; environment is free of CFC’s and other

refrigerants which produce harmful gases leading to depletion of ozone

layer.

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PRINCIPLE

“The boiling point of a liquid changes with change in external pressure.”

In normal conditions, pressure exerted on the surface of a liquid is the

atmospheric pressure. If this atmospheric pressure is reduced on the surface of a

liquid, by some means, then the liquid will start boiling at lower temperature,

because of reduced pressure.

This basic principal of boiling of liquid at lower temperature by reducing the

pressure on its surface is used in steam jet refrigeration system.

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COMPONENTS

• EVAPORATOR

The evaporator or flash chamber is a large vessel and is heavily insulated to

avoid the rise in temperature of water due to highly ambient temperature.

• STEAM JET EJECTOR (replacing compressor)

Used to compress the water vapours coming out of the flash chamber

• CONDENSER Chills the LP, HT air coming from the thermo-compressor using chilled water as

the refrigerating medium.

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STEAM JET EJECTORS • High pressure steam from the boiler(generally called primary fluid or motive

steam/vapour) is admitted to the steam chest and expanded in convergent

–divergent nozzle to a very low pressure and the attains supersonic velocities

in the range of 1000m/s to 1350m/s.

• The flash chamber is connected to the region of low pressure of the ejector.

The water vapour from the flash chamber is entrained in the high velocity jet

of steam and both are mixed in the mixing section at the constant pressure .

• The velocity of mixture will be super sonic after the completion of the mixing

process.

• This supersonic steam get a normal shock in constant area throat of diffuser,

resulting in rise of pressure and subsonic flow.

• The diverting portion of the diffuser velocity head is recovered as pressure

head and finally high pressure steam is condensed in condenser.

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STEAM JET EJECTORS

Cross section of steam jet ejector

Velocity/ Pressure vs. distance

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STEAM JET EJECTORS

Basically, there are three different types of steam jet cooling plants:-

1. Compact Design for small capacities

2. Column Design for medium capacity and large capacities where there is

little floor area

3. Bridge Design for high capacities

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COMPACT DESIGN

These consist of horizontally designed equipment: one flash vessel (1) and one

condenser stage (2) being installed in a common horizontal vessel. The jet pump

(3) is arranged in parallel to this vessel. A small liquid ring vacuum pump (4) is

installed as a de-aeration unit. the condensation heat is removed via the cooling

water – e.g. by a cooling tower(6). The plant is controlled by an operation control

system.

This type of design requires relatively little floor space and not too much height.

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COLUMN DESIGN

These are vertical construction: flash cooling chamber(1) and condenser

chamber (2) are mounted one on top of the other. The flash vessels and the

condenser chambers of each stage are connected to each other through

piping or a jet pump for vapour compression (3). In many cases, a cooling tower

(6) is installed in order to re-cool the cooling water. Generally, a steam jet

vacuum pump is provided as a de-aeration unit. The plant is controlled by an

operation unit.

This type of design requires relatively small floor space but greater height.

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BRIDGE DESIGN These consist of vertically or horizontally arranged flash cooling chambers (1),

horizontally mounted jet pumps(3) and vertically designed condenser

chambers(2). The flash vessels and condenser chambers of each stage are

connected by piping or a jet pump for vapour compression (3). In many cases, a

cooling tower (6) is installed for re-cooling the cooling water. A steam jet vacuum

pump for de-aeration is also included. The plant is controlled by an operation

control system.

This type of design requires relatively little height but more floor space .

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CRITERIA FOR DESIGN OF STEAM JET COOLING SYSTEM

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WORKING OF A STEAM JET COOLING SYSTEM

1. High pressure steam to the nozzle from the boiler which is expanded.

2. Water vapour from the flash chamber entrained with the high velocity steam

jet and it is further compressed in the thermo compressor.

3. The condensate is usually returned to the boiler. Generally, 1% evaporation of

water in the flash chamber is sufficient to decrease the temperature of

chilled water to 6ºC.

4. Chilled water is circulated by a pump to the point of application.

5. The warm water from the load is returned to the flash chamber. The water is

sprayed through the nozzles to provide maximum surface area for cooling.

6. The water, which is splashed in the chamber and any loss of cold water at

the application, must be replaced by makeup water added to the cold

water circulating system.

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Working of a Steam Jet Cooling Cycle

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CASE STUDY

Patumthani, (Thailand) • Here the cooling water temp.

produced by cooling tower is

between 29°C and 33°C.

• The maximum COP of 0.45 is

achieved when the refrigerator is

operated at boiler temp. of 110

°C, evaporator temperature of 17

°C, and cooling capacity of 3000W.

Tushan Cogeneration Company,

a power plant in Anhui province of China. • The total cooling load of the company

reaches the number of 69780kW.

• In China's current industry standard, the

driving steam of the double-effect Li-Br

absorption refrigerator can be

saturated steam

• Combined cycle system with

midpressure of 0.8MPa has refrigeration

capacity as low as 12ºC .

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An Experimental Setup

(Ref: Thesis by Adriaan Jacobus Meyer degree of M.Sc-Engg

in Mechanical Engineering Stellenbosch University)

CASE STUDY

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The boiler Condenser

Evaporator Ejector

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ADVANTAGES

1. Simple and hassle free construction

2. Vibration free system

3. Low production cost

4. Low maintenance cost

5. Water is used as a refrigerant which is perfectly safe.

6. Low running cost

7. Load variation quickly adjusted

8. It is suitable for places where steam is available such as process industry, steel

plant, petroleum plants, thermal power plants etc.

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DISADVANTAGES

1. Not suitable for water temperature below 4ºC.

2. The maintenance of high vacuum in the evaporator is necessary for proper

functioning of the system.

3. Since the ejected vapour and motive steam condensed in the condenser,

the magnitude of heat transfer is about 3 to 4 times that needed in the

vapour compression system per tone per hour. Thus large size of condenser is

needed.

4. Coefficient of Performance is very low.

5. The use of direct evaporation to produce chilled water is usually limited as

tremendous volume of vapour is to be handled.

6. Efficiency of ejector is not good.

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APPLICATIONS

1. Food processing plant

2. Gas plants

3. Breweries

4. Rubber and vulcanizing industries

5. Paper and pulp industries

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THANK YOU !