Refrigeration – Automatic control – Of external fluid or means
Patent
1994-01-24
1995-10-31
Tanner, Harry B.
Refrigeration
Automatic control
Of external fluid or means
621766, 62411, 62436, F25D 1706
Patent
active
054618770
DESCRIPTION:
BRIEF SUMMARY
This invention relates to both a method and means for air conditioning, and although generally applicable, has special value when it is associated with air conditioning for humid and temperate climates.
BACKGROUND OF THE INVENTION
Tropical and humid climates present serious design problems at various combinations of climatic conditions with room sensible and latent heat load conditions. These problems also occur in temperate climates, often at non-peak humid weather conditions when room sensible heat load is low and the room latent heat load is high. The method of this invention, and the means necessary for that method to be performed, address the dynamics of the problem arising from changing climate, changing ventilation requirements and changing room sensible and latent heat loads. The objectives of the invention are to achieve low running costs, good performance within comfort standards, low first costs and low intrusion of the air conditioning equipment into rentable space. The main objective is to provide an improved system performance which can be achieved over a full operating range of the air conditioning system of the invention, and in particular, overcome the problems arising from humid air, inadequate ventilation and the associated health hazards (the "sick building syndrome").
The modern air conditioning system involves so many interacting variables that any attempt to make a scientifically valid assessment of performance over a complete operating range for each design, let alone to undertake a full optimisation, has always been regarded as impractical. Optimisation of one particular parameter, or of the range of one particular variable, at one particular operating condition affects other variables to an extent which can render the study valueless. These other variables are not necessarily affected at that particular operating condition. For example, in a system being selected in a temperate climate the peak refrigeration requirement usually occurs when high people loads, requiring high ventilation air supply, coincide with the afternoon peak of a hot day, during which transmission is at its maximum. A dehumidifier coil can be selected which, at this peak lead condition, satisfactorily meets that design requirement while making provision for future changes and allowing a safe margin for errors in the lead estimates. However the performance of this dehumidifier coil during certain critical part lead conditions depends on the way in which the designer has chosen to satisfy the peak lead condition. An excellent peak lead selection can, at part lead, result in a sick building with high humidity and outside air intake which is well below the minimum levels prescribed by the relevant Standard.
PRIOR ART
In tropical climates it is conventional practice to pro-cool the outside air, however the coolant leaving the outside air heat exchanger is not usually sent on to the return air heat exchanger since it is in no position to offset the room sensible and latent heat loads properly.
The chilled water serves only a small outside air flow rate based on ventilation specifications, and a very much larger return air flow rate determined by the room sensible heat difference between the design room dry bulb temperature and the supply air. In Singapore for the design of a multistorey office building this is usually in the ratio of outside air to return air flow rate of 1 to 10 or less.
In existing practice the chilled water flow rate would be selected to have a water temperature rise of about 8.degree. C. for the outside air heat exchanger resulting in a reduced mass transfer of moisture from the air.
In this invention the outside air heat exchanger is served by a chilled led water flow rate which is inordinately large for the relatively small outside air flow rate passing through the exchanger. This is because it is based on the requirements of the peak simultaneous demand of the return air complex to which the outside air coolant then flows. Hence, in direct contrast to existing practice the water tempera
REFERENCES:
patent: 2828464 (1958-03-01), Nixon et al.
patent: 4319461 (1982-03-01), Shaw
patent: 4457357 (1984-07-01), Van Arnhem
patent: 4841733 (1989-06-01), Dussault et al.
patent: 4876858 (1989-10-01), Shaw et al.
patent: 5058388 (1991-10-01), Shaw et al.
Luxton Russell E.
Shaw Allan
Luminis PTY Ltd.
Tanner Harry B.
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