The present invention relates to an apparatus for cooling a fluid that comprises
an ice storage reservoir,
means for circulating a cooling fluid within the reservoir where it can exchange heat with the ice, and
means for circulating a fluid to be cooled within the reservoir where it can exchange heat with the ice.
It also relates to an ice storage reservoir which is such that it can be a part of such an apparatus, as well as to banks of tubes or groups of tube banks for heat exchange that can be part of the reservoir so as to ensure the transfer of heat between the cooling fluid or the cooled fluid, on the one hand, and the ice, on the other hand.
Recently, apparatus for cooling fluid have been introduced that comprise an ice storage reservoir for cooling purposes in air treatment installations as, for example, air conditioning, in which the air to be treated notably passes through a heat exchanger, called a "chiller," for exchange of heat with an antifreeze liquid such as glycolated water that is at a temperature less than ambient and circulated for this purpose by a pump between the chiller and the ice storage reservoir. The antifreeze liquid flows in the reservoir so as to be cooled by direct heat transfer with the ice, freely or in a manner guided by baffles. The antifreeze liquid here constitutes the fluid to be cooled by heat exchange with the ice in the reservoir.
Naturally, the ice first has to be frozen, then refrozen again in the reservoir as the ice melts as a result of heat exchange with the fluid to be cooled. For this purpose, one can use two ice making methods, in both cases by means of the flow of a cooled fluid in the reservoir.
A first ice making method uses the direct expansion of an appropriate refrigerant, such as Freon.RTM., as the cooling fluid contained in a closed flow loop that passes through the reservoir and also contains, besides the reservoir, other components of a traditional refrigeration system such as a compressor, a condenser and an expansion device.
A second method uses as the cooling fluid the cooled fluid itself, namely the antifreeze liquid itself such as glycolated water, which fluid, outside the reservoir, flows through a heat exchanger where it is cooled by an evaporating refrigerant, such as Freon.RTM., supplied by a closed loop refrigeration system that also, as is usual, contains a compressor, a condenser and an expansion device. The chilled fluid then returns to the ice storage reservoir where it cools the water to make ice.
The incorporation of an ice storage reservoir into a fluid cooling apparatus is of particular interest in terms of energy cost savings since it offers the possibility of making and storing the ice during periods of the day or week, called "off-peak hours," during which the energy required for this purpose, usually the electric power that operates the compressor of the refrigeration system, is the least expensive. It is thus possible to meet the maximum cooling load during the other periods of the day or of the week, that is, to avoid, to the extent possible, operating the compressor and consequently using electrical power, during those other periods of the day or the week during which, at the same time, energy costs are the highest and the need for cooling in general is greatest. The cooling capacity that is then required to supply the chiller of the associated air conditioning installation is, for the most part, supplied by heat exchange with the cooling fluid, that is, the antifreeze liquid such as glycolated water, with the ice being produced and stored between times. Naturally, even during those periods, the refrigeration system can be operated to provide additional cooling capacity if the need requires.
However, in their currently known embodiments, fluid cooling systems having an ice storage reservoir have a number of shortcomings.
Using glycolated water or other antifreeze liquids as the coolant in the ice storage reservoir and, possibly, as the cooling fluid for making ice, presents disadvantages inherent in using any liquid, that is, the need for appropriate leakproof piping systems to interconnect, for example, the chiller of the air treatment apparatus with flow control and safety valves and with other parts of the flow loop as well as complex and expensive control and regulation devices. One may need to periodically replenish the entire system as well as to maintain the proportion of antifreeze in the liquid. Certain repair or maintenance operations require draining and refilling the system, which procedures require large labor expenditure as well as extended periods during which the refrigeration apparatus is shut down because of malfunction or for preventive maintenance. In addition, the consequences of a possible leak of glycolated water or other antifreeze liquid, such as soiling of and damage to the areas adjacent to the apparatus, are considerable.
When one also uses as the cooling fluid intended for making ice a fluid that is initially liquid and vaporized in piping that is intended to be immersed essentially continuously in the ice within the storage reservoir, it is necessary to take numerous precautions to avoid any leak in this piping, given the danger represented by refrigerants such as Freon.RTM. that refrigerate by expansion and evaporation. In addition, in practice, using expansion and evaporation systems presents difficulties, notably because of the risks of retention of the compressor lubricating oil in other parts of the system, where the oil then remains and gradually accumulates, degrading system operation.
When the cooling fluid itself is an antifreeze liquid such as glycolated water and is used as the cooling fluid intended for making the ice in the storage reservoir, the known refrigeration apparatus also have the drawback of an increased requirement for space due the increased number and individual size of the necessary components.
European Patent Application 0 441 553 [U.S. Pat. No. 5,005,368 issued 9 Apr. 1991 to MacCracken et al.] recently proposed an air conditioning apparatus in which the air to be conditioned itself circulates, as the fluid to be cooled, inside the ice storage reservoir, where it is placed in a direct thermal exchange relationship with the ice. The ice is made in the storage reservoir through the direct expansion of an appropriate fluid which changes from a liquid to a gas during this expansion. The circulation of the air to be conditioned itself inside the storage reservoir as the fluid to be cooled, and the production of the ice through a direct expansion eliminate the drawbacks inherent in the use of an antifreeze liquid such as glycolated water but the drawbacks inherent in the production of cold through direct expansion still remain.