WF is a type of 'jet refrigeration' and does not require coolants or compressors to produce large volumes of chilled water. WF only needs low pressure waste steam and water to operate.
So how does it work?
WF uses a combination of specially designed technologies to cool down industrial process water or liquid gas to maximize heat transfer efficiency.
The process utilizes the theory of jet refrigeration. Low pressure waste steam passes through a series of ejectors and condensers which cools down circulated water within the facility. The generated chilled water flows through heat exchangers. It is these heat exchangers where the circulation water from the industrial process meets with the WF chilled water and is cooled to the desired temperature.
WF is a closed loop system. The whole system is controlled and automated by the use of an integral Digital Control System (DCS). Each system is individually designed to cool down water to specific temperature requirements.
An example of a 4,000,000kcal plant
One module is capable of producing 200m³ per hour of chilled water at approximately 4-6°c. To achieve this approximately 2500kg/h of low pressure waste steam between 2-4 bar pressure is passed through the ejectors. Approximately 10% of the chilled water production is from make-up water, thus every module requires approximately 20m³ per hour of make-up water.
The use of a modular design enables increased chilled water production capacity by simply adding modules to the system.
Steam: Low-pressure waste steam from the industrial process is piped to this collection point. It is then distributed to the various ejectors on the plant. The steam can be as low as 1 bar pressure.
The WF digital control system regulates pressure and flow rates at this point and automatically opens and closes valves according the variables set by the system.
The waste steam does not need to be anything more than 2-4 bar (even as low as 1 bar). The design and size of the ejectors creates the vacuum needed for the chilling effect to occur.
Chilling Unit: Water to be chilled is sprinkled over the top of the evaporator column and then gravity feeds to the chilled water tank below. From the water tank it is pumped to the heat exchangers to cool down industrial process water. The steam from the steam configuration pipe is fed through the venturi type ejectors, (above) and creates a vacuum in the evaporator column. It is this vacuum effect that removes latent heat from the chilled circulation water being sprinkled through the evaporator column. The removal of this latent heat rapidly cools down the temperature of the water within the evaporator.
The shape and design of the venturi ejectors speed up the flow of steam. As the steam speeds up the pressure differential created causes a movement of air from the evaporator column and thus a vacuum is created. Once the steam reaches the end of the ejectors the steam expands as the throat of the ejector widens. Rapid expansion causes the steam to lose temperature and form water droplets.
The chilling unit
Aerial view of 2 chilling units
Panoramic view of 2 chilling units
Used steam is collected in the condenser column. Condensing media within the chamber enhances the condensing effect. Circulation water is also used at this point to assist cooling within the chambers. Heat is also removed from the smaller auxiliary venturi ejectors further on in the process. Condensed steam is re-circulated and steam that still exists as a vapour is released to atmosphere.
Heat Exchange: The final stage of the process. The chilled water is pumped to the heat exchangers. At the same time industrial process water is also pumped to the heat exchangers from outside the plant. The resultant heated, chilled water from the WF process is re-circulated to the top of the evaporator column where it can be chilled again. The now cooled industrial process water can be used to enhance heat exchange in other parts of the site. It may even be used to aid air-conditioning.
Example of a Spiral Type Heat Exchanger
Water Circulation Unit: As mentioned above circulation water is used to maintain temperatures within the plant. The used water is contained in a large tank and pumped to a cooling water system before being used again within the process.
Water Filter Unit: To maintain optimum capacity within the plant excess water is required. Depending on the application and location up to 10% of chilled water production can be from make-up water. To ensure this water contains no particulates a water filter unit is built into the system. Some of this make-up water can be collected from the condensed steam.
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