| 1. | An arrangement for ensuring that ice will form substantially uniformly on the outer surface of a tubular heat exchanger which is submersed to the bottom of a body of water and which comprises a single tubular member, or a plurality of tubular members connected in parallel, within which there flows a liquid heat carrier whose inlet tempera¬ ture is lower than the freezing point of the water in said body of water, characterized in that the tubular member or each tubular member is so arranged that parts thereof con tact said bottom at a plurality of locations so chosen that the distance between two mutually adjacent locations is short in relation to the length of tube between two consecutive contact locations between the tubular member and said bottom, at least the majority of said parts in contact with the bottom of said body of water being covered with a suitably coherent layer of lump ballast material, such as shingle or gravel, which, due to the relatively low input temperature of the heat carrier flowing through said tubular member is caused to freeze to form a block of ice and ballast material, said frozen block therewith forming a heat conductor for distributing cold from the inlet of the tubular member and the areas adjacent thereto to remaining regions of said tubular member, so that there is formed a cylindrical ice coating of substantially uniform thickness on those parts of the tubular member which lie freely placed in said water between said locations. |
| 2. | An arrangement according to Claim 1, characterized in that the amount of ballast material is sufficient to anchor the tubular member or each tubular member to the bottom of said body of water, in addition to ensuring that ice will form uniformly on the outer surface of said tubular member. |
PLACED IN WATER
The present invention relates to an arrangement according to the preamble of Claim 1. The invention can e applied in conjunction with heat-pump systems of the
A few years ago, the formation of ice on the heat ex* changer was considered a disadvantage and should be avoided, since strruucctural damages had occurred as a result thereof.
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 conf guration, which may have a diameter of say 50 cm at the beginning of the heat exchanger, and may terminate at a distance of 200 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 uniform icing of heat ex¬ changers 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 car¬ rier 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 method, a tube-part for outgoing heat carrier is brought into contact with the tube part for incoming heat carrier. This contact can be made along the whole of the tube-parts or at given locations therealong. The tube-parts are thus caused to freeze together and an ice-cylinder is
formed around the two tube-parts, which contributes towards uniform icing.
All of the aforedescri bed methods for producing uniform icing are encumbered with disadvantages. None of the ύ methods facilitates anchoring of the ice-coated heat ex¬ changer. The method in which the heat-carrier flow is re¬ versed requires the provision of automatic devices and auto¬ matically controlled valves, which costs money and reduces reliability. In the method in which the heat pump is run 0 intermittently, the heat exchanger is not used to the whole of its capacity, which means that a larger heat exchanger must be used in order to obtain a certain given capacity. The third method requires the tube-parts forming the heat- exchanger loop to be placed closely together over a signi- 5 ficant part of their lengths. This lowers the capacity of the heat exchanger, since when iced-up the double-laid tube will have substantially the same heat transfer capacity per meter as a single ice-covered tube. Consequently, a larger heat exchanger is required to maintain the caDacitv ϋ desired.
The present invention, which is characterized by the features set forth in the claims, ensures uniform icing ir¬ respective of the length of the heat-exchanger tube or the parallel-coupled heat exchanger tubes, by providing a cold 5 bridge between a selected number of locations on each heat- exchanger tube. The cold bridge is produced by arranging the heat-exchanger tube so that it contacts the bottom of the body of water at any number of locations, which are spaced at any distance apart, normally 10-100 cms. The tube, o or tubes, is or are then covered at these locations with a layer of shingle or stone of suitable size, or with some other lump ballast material, to a height which is normally preferably equal to the distance between two mutually ad¬ jacent contacting locations of the tube-parts with the 5 bottom of the body of water volume.
At low water temperatures and low heat-carrier tempera¬ tures, ice will first form around those tube-parts which are
covered with shingle or stone, owing to the fact that at these locations the intrinsic convective power transfer is far smaller than with a tube located freely in water. When the distance between the locations at which the tube-parts contact said bottom and the height of the shingle or stone layer are appropriately selected, a cold bridge will de¬ velop in the shingle or stone before any appreciable icing occurs on those parts of the heat exchanger located freely in water. This enables ice to form uniformly over the whole length of the heat-exchanger tubing located freely in water.
The invention will now be described with reference to an exemplifying embodiment thereof illustrated in the accompanying drawing, in which Figure 1 is a schematic side view of an arrangement according to the invention; and
Figure 2 is an end view of the arrangement illustrated in Figure 1.
A heat-exchanger tube ό is immersed in a body 1 of water having a top defining surface 12 and a bottom 2. The heat exchanger as a whole can comprise any selected number of heat-exchanger tube members connected in parallel. The heat-exchanger tube 3 is lain in a closed loop within which there circulates a heat carrier 11. The temperature of the heat carrier 11 in the initial, underwater part 7 of the heat exchanger tube 3 is lower than the freezing point of the water. The cold heat carrier 11 is conducted in the heat-exchanger tube 3 down to a pile 4 of shingle or gravel, wherewith ice 5 is formed between the individual stones forming said pile 4. The ice first forms around the in¬ coming tube-part 7, at its location beneath the pile 4 of shingle, and is then gradually formed around the outgoing tube-part 8, and its location within said pile 4. The ice 5 has finally frozen practically the whole of the pile 4 of shingle, to form a coherent frozen block. When the pile 4 of shingle freezes, pronounced cold bridges form between parts of the heat-exchanger tube 3 located in the frozen pile 4 of shingle. For example, cold is transferred from
the ingoing tube-part 7 to the outgoing tube-part 8 by the transfer of cold from the locations 9 and 11 to the loca¬ tion 10 on the heat exchanger tube 3. The continued supply of cold heat carrier 11 will result in an even cylindrical formation of ice along the whole of that part of the tubing 3 located freely in the water 1. The transfer of heat from the water 1 to the heat carrier 11 is lower for that part of the heat exchanger 3 located in the pile 4 of shingle than for that part located freely in the water. By and large, this is compensated for, however, when the pile 4 of shingle freezes and a large quantity of heat is taken from the ice surface 13 on the pile 4. The quantitites in which shingle is placed over the heat-exchanger tube 3 can be ad¬ justed to prevent the heat-exchanger tube 3 from rising in the water as a result of the buoyancy developed by the ice 6,
Next Patent: ACCUMULATION PLANT FOR HEAT TRANSFER