Refrigeration – Processes – Accumulating holdover ice in situ
Patent
1987-11-18
1990-01-16
Capossela, Ronald C.
Refrigeration
Processes
Accumulating holdover ice in situ
62434, F25D 300
Patent
active
048940771
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method of accumulating and restituting cold, wherein, during cold-accumulating phases, in a storage vessel containing a mass of cold-accumulating and cooling liquid, a cluster of rigid aggregates of crystals of this frozen liquid is accumulated, and wherein, during cold-restitution phases, the cold accumulated in the storage vessel is restituted to a utilization circuit by fusion of said crystals in the vessel, by making a stream of said liquid circulate in closed circuit, successively through said cluster and said utilization circuit.
The present invention also relates to a device for implementing this method, including a storage vessel containing a cold-accumulating and cooling liquid, at least partially in the form of a cluster of rigid aggregates of crystals of said frozen liquid, these crystals being obtained by freezing this liquid by vaporizing a refrigerant brought into direct contact with cold-accumulating and cooling liquid, and means for injecting refrigerant at least partially in the liquid state, into this liquid.
The systems operating according to this known method, invented by M. L. Simon and described for example in Swiss patent No. 628,417, have multiple advantages over other known systems for accumulating cold wherein a cold-accumulating liquid, formed in general, as in the SIMON system, of water or an aqueous solution, for example a eutectic or non-eutectic solution of mineral salts such as sodium chloride or calcium chloride, is frozen on the outer surface of a refrigerant-evaporator or a heat exchanger traversed by water with glycol cooled to a temperature below 0.degree. C.
In particular, these new systems are notably more compact, simpler and more economical than other known systems.
Moreover, their thermodynamic efficiency, which constitutes an important quality coefficient, is superior to that of these conventional systems because, with this new process, the vaporization temperature of the refrigerant, which presents a large surface for direct contact with the cold-accumulating and cooling liquid to be frozen, is very close to the freezing temperature of this liquid, while with the other known systems, this vaporization temperature is several degrees Celsius less than said freezing temperature because the exchange of heat between the refrigerant and the cold-accumulating and cooling liquid is effected across the whole thickness of the solid ice deposit, of low thermal conductivity, which covers the above-mentioned evaporator or heat exchanger. This drawback is reduced, but not eliminated in other known systems wherein solid aggregates of macroscopic ice crystals are produced by indirect cooling of the accumulating liquid on the wall surface of a refrigerant evaporator and are mechanically scraped off or carried off by a thin film flowing by gravity over the surface of a cold wall to constitute with cooling liquid a heterogeneous mixture of pasty consistency which is conveyed and then discharged into a cold-storage vessel, as described in U.S. Pat. No. 4,480,455 or in U.S. Pat. No. 4,509,344.
Cold accumulating systems are in general characterized by two other economically significant quality coefficients: their cold-accumulating capacity per unit volume of space utilized by the installations (kcal/m.sup.3) on one hand, and their cooling efficiency of the cooling liquid during their cold-restitution phases on the other hand. This cooling efficiency may be defined, for a given flow rate D of the cooling liquid (m.sup.3 /h), as the ratio: R(D)=(.theta.1-.theta.2)/.theta.1-.theta.o) where .theta.1 is the temperature of the cooling liquid heated after its passage in the utilization circuit, on its arrival in the accumulator, where .theta.2 is the temperature of this liquid after its cooling in the accumulator, at the outlet of the latter, and where .theta.o is the freezing temperature of the cooling liquid. This ratio R(D), included between 0 and 1, is independent of the temperature .theta.1, but varies with the flow rate D.
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Pfau Jean
Simon Laszlo
Capossela Ronald C.
Coldeco S.A.
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