System and method of cooling

Abstract

The invention provides a cooling fluid heat exchange unit including: a primary heat exchange unit including a closed circuit for circulating primary circuit fluid; and a secondary heat exchange unit adapted to provide cooled air in communication with the primary heat exchange unit. The closed circuit for the cooling fluid as it passes through the primary heat exchange unit ensures that the cooling fluid is prevented from exposure to the atmosphere, and in particular, to the air forced through the heat exchange unit.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. patent application Ser. No. 10 / 483,656, entitled SYSTEM AND METHOD OF COOLING, filed on Aug. 27, 2004, the disclosure of which is expressly incorporated herein by reference; U.S. application Ser. No. 10 / 483,656 is related to and claims the benefit under 35 U.S.C. §119 and 35 U.S.C. §365 of International Application No. PCT / AU02 / 00898, filed Jul. 5, 2002.FIELD OF THE INVENTION [0002] The system and method of the present invention relates generally to the cooling of air and more particularly to a system and method of cooling air in systems including a heat exchange unit to effect heat transfer from a cooling fluid. The invention is particularly suited to cooling systems for relatively large volumes which is required in circumstances such as the cooling of air in large office buildings. BACKGROUND OF THE INVENTION [0003] Areas occupied by people generally require some form of heating and / or coolin...

AI Technical Summary

Benefits of technology

[0025] The closed circuit for the cooling fluid as it passes through the primary heat exchange unit ensures that the cooling fluid is prevented from exposure to the atmosphere, and in particular, to the air forced through the heat exchange unit. This separation removes the risk of the generation and distribution of the legionella bacterium. In practice, the closed circuit is likely to form part of a loop within a cooling system where the cooling fluid is transported from a location where the fluid is used to absorb thermal energy and subsequently transported to the heat exchange unit in order for the cooling fluid to release the absorbed thermal energy.

[0026] In a preferred embodiment, the cooled air emitted from the air cooler is substantially free of fluid in a liquid state. In a particularly preferred embodiment, the air cooler and the primary heat exchange unit are separated by a distance along the path of air flow from the cooler to the primary heat exchange unit to reduce the likelihood of fluid in a liquid state passing from the air cooler and impinging upon the primary heat exchange unit.

[0033] In a particularly preferred embodiment, a water absorbent material pad including a plurality of fluted apertures of a size less than 7 mm is used as part of the air cooler. Ordinarily in evaporative cooling applications, a water absorbent material pad with a plurality of 7 mm fluted apertures is used. However, in this embodiment of the invention, use of a pad with fluted apertures of a size less than the standard size of 7 mm has been found to provide a more efficient cooling effect. This particular embodiment also uses variable pitch fans for drawing air through the primary heat exchanger and through the air cooler pads. As a result of the increased efficiency resulting from the use of a pad with fluted apertures less than 7 mm, the overall pad size may be reduced whilst still achieving the same cooling effect that of a pad with standard sized fluted apertures. A reduction in the overall size of an air cooler pad may be significant for installations where a conversion from an existing cooling tower arrangement is required and there is limited physical space in which to install a new cooling fluid heat exchange unit.

[0034] In another embodiment, the cooling fluid comprises highly concentrated ammonia with a primary heat exchange unit comprising stainless steel or aluminium tubing effecting passage of the ammonia through the heat exchange unit. In this particular embodiment, the ammonia enters the primary heat exchange unit in a gaseous state and upon having thermal energy removed, the ammonia is emitted in a liquid state. Whilst ammonia has previously been used as a cooling fluid, it has only been feasible for extremely large installations. As a result of the improved cooling efficiency from use of an air cooling stage, an effective and economically feasible cooling fluid heat exchange unit using ammonia as the cooling fluid may be produced for smaller installations.

Problems solved by technology

Heating and cooling large areas such as office buildings usually requires a significant capital investment in the plant and equipment that effects the heating and / or cooling.

Whilst this type of system is commonly used for large office buildings, cooling towers unfortunately provide an environment conducive to the generation and distribution of a bacterium known as legionella pneumophilia.

Patients become increasingly short of breath and the respiratory symptoms progress to pneumonia, often culminating in respiratory failure.

However, in the dynamic environment of a cooling tower system, the performance of chemicals is different from that in controlled laboratory trials.

As a result, the efficacy of water treatment with a broad spectrum biocide cannot be predetermined for any particular environment and as such, ongoing sampling of cooling tower water is required to ensure that microbial growth has been limited to an acceptable level in addition to any chemical treatment.

Apart from the cost of the biocides, the requirement for ongoing sampling has the effect of significantly increasing the maintenance cost for a cooling tower system.

Apart from the significant capital investment required for an ozone generator, there remains some doubt as to the efficacy of this type of system for preventing microbial growth and the spread of Legionnaires' Disease.

However, the colour, tepidity and chemical composition of the water can interfere with ultraviolet radiation transmission and as such, determination of the ultraviolet absorbency of the water to be treated prior to installing ultraviolet equipment is usually advisable.

Once again, the installation of an ultraviolet radiation system involves a significant capital expenditure and is not an attractive option given that the efficacy of these systems is still currently questionable.

There is a lack of conclusive scientific evidence to demonstrate that these proprietary devices have any significant effect on the microbial load in treated water.

Whilst filtration systems present the simplest method available for the reduction of microbial matter in water, a full-flow filtration plant that will remove fine particles is generally not practicable for most existing systems due to space and weight restrictions.

Additionally, such filtration systems have associated installation and operational costs that generally render this approach economically infeasible.

In any event, with any type of filtration system, there is necessarily an ongoing maintenance cost for backflushing and replacement of filters.

Irrespective of the water treatment systems currently in use, ongoing maintenance in the form of water sampling cannot be avoided and necessarily increases the ongoing maintenance cost for the operation of a cooling system incorporating a cooling tower.

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