Heat exchange – Geographical
Patent
1985-04-12
1987-09-01
Davis, Jr., Albert W.
Heat exchange
Geographical
622387, 62260, F25C 112
Patent
active
046902058
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an arrangement for ensuring that ice will form substantially uniformly on the outer surface of a tubular heat exchanger which is submerged to the bottom of a body of water and which includes at least one tubular member within which there flows a liquid heat carrier whose inlet temperature is lower than the freezing point of the water in said body of water. The invention can be applied in conjunction with heat-pump systems of the kind which take energy from an energy-absorbing closed loop which lies partially in water and through which there is circulated a liquid whose freezing point is lower than that of the water in which the loop is placed. That part of the loop which lies in water will hereinafter be referred to as the heat exchanger while the liquid passing through the loop will be called the heat carrier. The heat exchanger may comprise any number of tubular members connected in parallel.
Thus, the heat pump takes energy from the heat carrier, therewith lowering the temperature thereof, whereafter the temperature of the heat carrier is raised again in the heat exchanger, by taking energy from the water in which the heat exchanger is placed. The invention can be applied when the temperature of the water is so low that part of the energy taken from the water occurs through formation of ice on the outer surfaces of the heat exchanger. This naturally implies that the temperature of the heat carrier is below the freezing point of the water.
A few years ago, the formation of ice on the heat exchanger was considered a disadvantage and should be avoided, since structural damages had occurred as a result thereof. Often, the heat exchanger, either in part or as a whole, rose to the surface of the water, which normally resulted in leakage of heat carrier. In recent times it has been observed that important advantages can be obtained in respect of energy-producing heat-pump systems when ice is permitted to form on the heat exchanger. The energy production plant is always able to take energy from the water, even though the temperature thereof lies close to its freezing point. The plant is normally able to run at full capacity, irrespective of whether the temperature of the water falls to its freezing point during certain periods of operation. The problem encountered when permitting ice to form is that it is often necessary to secure the heat exchanger against the buoyancy forces imparted thereto by the ice, which forces can be quite large. Maximum ice-diameters can reach to between 40 and 70 cms, implying a buoyancy force of about 11-33 kg per meter of heat exchanger tubing of conventional sizes. The problem is not lessened by the fact that the extent to which ice forms varies along the heat exchanger tubing, owing to the fact that the temperature of the heat carrier increases progressively therealong. The result is an ice formation of conical configuration, which may have a diameter of say 50 cm at the beginning of the heat exchanger, and may terminate at a distance of 200 m therefrom. Uneven icing is disadvantageous from the aspect of anchoring down the heat exchanger and also from the point of view of capacity in terms of heat transfer, and also in terms of the ability to accumulate a large quantity of ice.
Several methods of creating substantially uniform icing of heat exchangers immersed in water are known to the art. For example, the direction of flow of the heat carrier can be reversed periodically. Although icing is then relatively uniform, the ice is thickest at the beginning and at the end of the heat exchanger, if the heat carrier is allowed to move in both directions for the same length of time. Icing will be relatively uniform when heat is taken from the heat carrier intermittently while constantly circulating the same, provided that the heat pump is working for less than about 65% of the time. When the pump is switched off, cold will be transmitted from the initial parts of the heat exchanger to its remaining parts, resulting in almost uniform icing. In a third metho
REFERENCES:
patent: 672555 (1901-04-01), Hill
patent: 4338043 (1982-07-01), Biancale et al.
patent: 4407351 (1983-10-01), Backlund
patent: 4540041 (1985-09-01), Backlund
Cole Richard R.
Davis Jr. Albert W.
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