WO1986002772A1

WO1986002772A1 - Transformer tank with cooling by concentric and radial radiators and with reduced capacity

Info

Publication number: WO1986002772A1
Application number: PCT/FR1985/000300
Authority: WO
Inventors: René PIOCH
Original assignee: Pioch Rene
Priority date: 1984-10-29
Filing date: 1985-10-23
Publication date: 1986-05-09
Also published as: DE3590650T1; FR2575816B1; JPS62500553A; GB2176058B; GB8612117D0; BR8507019A; GB2176058A; FR2575816A1

Abstract

The cooling of tanks by means of concentric and radial radiators (1) comprised of vanes (2) arranged about a cylinder (3) occluded in its central portion by a torpedo (6) forcing all the fluid to be cooled to pass integrally through the vanes. The device is completed by solid and coated elements, made of cork or glass, intended to reduce the volume of the required dielectric. The invention concerns more particularly power transformers and heating or refrigerating installations as well as air conditioning systems.

Description

TRANSFORMER TANK COOLED BY RADIAL AND CONCENTRIC RADIATORS AND WITH REDUCED CAPACITY

Currently, transformer tanks are equipped with devices to cool the liquid dielectric which they contain and which is used to convey the heat given off by the energized windings.

If for small power transformers simple wave panels that is to say fin fitted or flat radiators few joined the cu ^¬ ve enough, it is different for power transformers because the heat dissipation increases in proportions such as the current devices which consist of a multiplication of flat radiators are no longer sufficient or quickly limit the possible overpower to absorb the spikes that the transformer can withstand. Anyway, the proliferation of these radiators do not result in increased proportion ^¬ tional dissipation for their unit cooling capacity decreases with their number. This requires increasing the volume of the dielectric to have a significant thermal buffer but it also increases the price of the transformed ^¬ tor, dielectrics are becoming more expensive.

Not all improvements and improvements on flat radiators have brought any real solution.

Aerial fans are often added, but they do not work in optimal performance conditions because of the design of the radiator batteries. A second type of process involves passing the dié ^¬ electric radiator through the same kind as those used for the ^¬ Tomobiles with fans but the risk of clogging the pipes is large, forcing to increase their section and thereby reducing the capaci ^¬ ty per unit volume of the radiator and the volume of the dielectric. The present invention avoids these difficulties and greatly expands the do ^¬ maine current application by getting a much higher efficiency of the cooling system, allowing a significant reduction in the volume required dielectric.

This invention consists in using a circular wave panel (fig.l) consisting of fins (2) arranged radially around a cylinder (3) cen ^¬ tral. We do not insist on the procedure of making these ele ^¬ ments that falls within known techniques (bending, welding).

This set of fins is extended by two cylinders (4 and 4a) welded provided with the connection device to the tank such as flanges (5). In this cyclic lindre (3) internally delimited by the fins (2) is arranged a sacking tor ^¬ (6) adjusted, and terminated by two ribs (7). This torpedo is of a length less than the fins so as to provide two circular passages (8 and 8a) in communication with each fin. This device forces the cooling fluid to pass necessarily through all the fins and this uniformly (dotted arrow, fig. 2) since the device is concentric with respect to the axis of the central cylinder (3). This gives a forced circulation which allows all the fins to have the same maximum fri¬ gorific efficiency, the speed of the fluid being the same in all the fins and the entire surface of the fins being in contact with the fluid and the air, (white arrow, fig.l). Such a device will generally be arranged vertically. To further increase this efficiency, it is possible to produce this axial radiator with materials with very high calorific value such as aluminum. This device also allows the use of mechanical means allowing the multiplication of heat dissipation. A first means consists in ^' introducing the radiator (1) into a sheath (10) arranged around the fins so as to create a duct (11) inside which the radiator is located, thus creating a well-known chimney effect and which will accelerate the circulation of. air and therefore performance. A second means consists in placing a fan (12) which will create a violent current of air inside the duct which cools the fins vigorously and, by conductivity, the fluid which circulates there. The efficiency of such a device is maximum since all of the air propelled by the ventila¬ tor passes through the duct and cools the device. A variant of this last device consists in giving the ends (13) of the fins a general T shape so that this part directly constitutes the sheath (10), thereby increasing the surface area for exchange with the air. (fig. 4).

A third device consists in placing at the end of the sheath opposite the fan an overhead turbine (15) driving a submerged pump (15a) in the central cylinder (3) leading to the fins (2) (fig.2). The large speed of air in the sheath will rotate this turbine (15) which will drive the pump (15a). Thus, by turning on the fan, one obtains an increase in the speed of the air (therefore its mass) in the duct but also simultaneously an increase in the speed of the oil passing through the radiator (therefore its mass) without these increases in speed disrupting the operation and therefore the performance of the assembly. Such a device allows a significant increase in heat dissipation as well as the recovery of part of the energy supplied by the fan. By placing the air turbine at the lower end of the duct and the fan at the upper end (suction), another increase in system efficiency is obtained (Carnot cycle and adiaba- relaxation - as of 1 r).

A variant (fig. 10) of this device consists in creating the duct with a battery of flat radiators (27 by the adaptation of two cheeks (28). At one end of this duct is arranged a fan (12) blowing or vacuuming which creates a strong draft in the duct.

It should be noted that it is not possible to add to it the turbine (15) because that would seriously disturb the circulation of the oil which would tend to pass in priority by the radiators closest to the entry and the out of the oil (4) and which are the least cooled. A second variant consists in adapting the principle of the inlet and the outlet of the oil (8 and 8a) at the two ends of the fins for the on¬ tanks of the low-power transformers (fig. 10) or double wave panels (fig. 9). For this, it is necessary to have inside the tank (14) a sheet (38) of width less than the height of the fins (2) to provide two passages (8 and 8a) for the oil. This device has the effect of eliminating all the secondary convections (39) which are of lower efficiency by keeping only the inlet (8) of the oil at its maximum temperature (upper part of the tank). -

In the case of double wave panels (fig. 9), the common central part is occupied by a torpedo (6) filled with cork (9) leaving an upper and lower passage for the entry and exit of the oil (8 and 8a). To avoid that the fins, under the effect of thermal stresses or depression crush or reduce the passage of oil, it is used either half-stamps of oval or round shape (E) opposite, or balls (B) partially housed in spherical external stampings. These systems hinder the passage of oil by reducing its passage. in the case of the invention, the radiator being of revolution, it is possible to replace these systems with U-shaped parts (13a) welded between two fins (2) (fig.4) so as to prevent any crushing fin. These judiciously arranged parts serve as a thermal bridge, increasing the cooling of the assembly and also serving as deflectors for channeling the air passing through the radiator. These parts playing the role of reinforcement doi¬ wind to reduce the thickness of the sheet used for the manufacture of the radiator and therefore its weight and thermal inertia. They can also replace the sheath (10) provided around the radiator

These radiators will be of a determined length for reasons of ease of manufacture and transport, but it is possible to couple them to constitute a column of radiators of required height or capacity (fig. 6) This possibility offered by the axial design radiators allows much greater flexibility in the study of the necessary refrigeration device for a given transformer.

The section of the radiator is of any geometric shape, for example round (fig.l) or square (fig.5). A e ^'xtrêmité of each fin, it is possible to crush a portion (24) to give an oblique shape to the passage of oil, facili¬ as its circulation by deleting two blind spots. These crushed parts can be folded (fig.3) to obtain a better thrust on the blades of the turbine and facilitate the penetration of the air drawn by the ventila¬ tor. An essential advantage of the process, taking into account the possibility of considerably increasing the cooling capacity, consists in being able to use the transformer in excess power, for example at the time of peak consumption, since the increase in heat dissipation can be absorbed by the safe cooling system for normally cooled windings.

By equipping the cylinders (4 and 4a) for connecting the radiators to the valve tank (22, 23), it is possible to mount these elements on site after transporting the transformer but also to be able to remove them for repair or change of heat capacity in off-peak hours without stopping the use of the transformer.

It is obvious that the device described has an exceptional flexibility which allows it to be adapted very exactly to climatic or use conditions or even to be modified without stopping the transformer. An automatic control device for these valves as well as for the fans and the pump allows self-regulation of the temperature of the windings. the torpedo (6) partially closing off the cylinder (3) is filled with a fluid-tight material (9) such as cork, which prevents the torpedo from being filled with the useless fluid since it is static. Only the voids existing between the pieces of cork will be occupied by the fluid, the torpedo being deliberately not waterproof. This vacuum represents only about ten percent of the total volume of the torpedo.

Modern liquid dielectrics used as refrigerants are expensive whether mineral or chemical. Numerous attempts to reduce the volume occupied by these dielectrics inside the tank have been unsuccessful since they were hollow bodies presenting the risk of filling, causing the level of the dielectric to drop and rapid destruction. transformer, or blocks of wood as expensive as the oil being replaced. The solution presented consists in using a truly waterproof material which is compatible with dielectrics, resistant to temperatures of use and at a lower cost than that of the replaced dielectric. One of these materials is steam agglomerated cork. It comes in the form of volumes of various shapes (16) (17), those of the molds where it was agglomerated. To prevent it from falling apart even partially and cork particles from blocking certain cooling channels, it is coated with an envelope (18) This envelope can be formed by a fine fabric, a thermo-sheath shrink, varnish or sprayed plaster, all known solutions. This envelope must not be impervious to the dielectric so as to allow, during filling under vacuum or by gravity, that the voids remained between the cork grains at the time of its agglomeration are filled by the dielectric so as to obtain a body saturated and therefore having a stable and neutral volume. The level of the dielectric in the tank will therefore be maintained. These elements will be arranged between the windings and the tank. As they are massive, they are not a good conductor of heat so we must avoid them touching this tank because they would reduce the surface which participates in the general cooling. For this, small bosses (19) will be regularly distributed on the faces of these elements located towards the walls of the tank (14) or else, the edges of plates assembled obliquely in certain parts of the tank will be used ( 20) (24) (fig. 5). The thermal bridges will thus be reduced to the maximum. Known fixing means such as tab or flange will be overmolded during agglomeration or coating to hold in place these elements which, of very low density (of the order of 0.18) would be found anarchically at the top of the tank, this is important because these elements will be given simple shapes but directing the circulation of the dielectric towards the points to be cooled so as to optimize this cooling.

Another possibility may be constituted by the use of glass spheres (fig ll) of a certain dimension (a few millimeters to a few hundred meters), the density of which will be determined as a function of the position they will have to occupy in the transformer (fig.12), this density can be higher (bottom filling) (29), slightly lower (filling the volume located above the windings) (31) or equal to that of the dielectric used (30). Like cork, these hollow spheres can be coated in ^: a plastic sheath (32). The density of the spheres will be obtained by varying the thickness (33) of their wall, that is to say the weight of ground used for their manufacture so that this density is close to that of the di¬ electrics used (0, 8 to 1, -5), the limits of use being not to disturb the circulation of the oil and therefore convection. The spherical shape has a good sliding coefficient. Other more streamlined shapes 86/02772 5

(fig.11) such as ellipticals with a thicker end (34) to keep them in an upright position are also possible. These spheres can be agglomerated to form large volumes (fig.13) and _r appropriate form their plastic casing ensuring this fastening while maintaining a relative flexibility to the whole. This device based wanders present the maximum security as the dielectric point of view of ininf ^{'lammabilité.}

Its use can be envisaged to reduce the masses of resin in the case of coated transformers, these balls of the same density as the resin being incorporated at the time of casting (fig. 14). This increases isolation by reducing the cost price. In this particular case, these beads will be smaller in size for better distribution.

These balls will be manufactured starting from a werre tube filled with a gas which can be a gaseous dielectric such as SF6 (sulfur hexafluoride) and which will be found in the empty central part of these balls, increasing their dielectric quality.

The adoption of such elements is made possible by the possibilities of increasing the cooling power of the radial radiators described above since the reduction in the volume of the cooling dielectric (21) for identical dissipation can only be obtained ^. by an increase in efficiency of the radiators or a higher speed of passage through these radiators, which is the case with the present invention.

Claims

1- Transformer tank cooled by natural or mechanical ventilation, characterized in that the cooling takes place using radial and concentric radiators and that the capacity of the tank is reduced by solid sealed elements. 2- transformer tank according to claim 1 characterized in that the cooling of the dielectric is provided by radiators (1) constituted by a central cylinder (3) around which fins are arranged radially (2) communicating with this cylinder central by its two ends (8), the central part being occupied by a torpedo (6) terminated by two warheads so that the dielectric which travels through the radiator passes in¬ integrally and regularly in each fin; device which can be adapted to wave tanks by placing inside the tank a sheet of dimension smaller than the fins to provide two passages for the oil which will allow the entry and exit of the oil, or to a double finned panel with an adequately shaped torpedo in the central common part.

3- transformer tank according to claim 1 characterized in that the radiator is placed in a sheath (10) so as to constitute a duct (11) through which a fan (12) draws air at large speed all of this air used to cool the fins of the radiator placed in the duct, the device being circular and concentric, a particular T shape can be given to these fins allowing them to replace the sheath (IU), this device can be applied to a battery of flat radiators by having two cheeks to form a rectangular duct at the lower end of which is placed a fan. 4- transformer tank according to claim 1 characterized in that in the cylinder (3) bringing the dielectric to the fins (2), there is a pump (15a) available to accelerate the circulation of the dielectric and increase heat exchanges, which is actuated by an overhead turbine (15c), itself driven directly by the air drawn by the fan arranged at the other end of the sheath, a device which is ^' adaptable to flat radiator batteries by having two walls for form a sheath inside which will be arranged the fan. 5- transformer tank according to claim 1 characterized in that to reduce the volume of the dielectric, it is used elements cons¬ constituted by a porous envelope (18) trapping a material (9) itself waterproof such as cork chipboard, elements provided with necessary fixing means and whose shape and position make it easier to circulate 5/0

tiυn of the dielectric inside the tank to optimize its refrigerating function, the porosity of the envelope allowing during initial filling the impregnation of the voids remaining between the cork particles at the time of its molding, a special case being constituted by the torpedo (6) occu¬ pant the central part of the radiator and double wave panels and filled with the same material.

5- transformer tank according to claim 1 characterized in that the elements intended to reduce the volume of the dielectric are glass of spherical or ovoid shape, the thickness of their wall (that is to say the weight of glass used) makes it possible to obtain elements with a density lower, equal to or greater than that of the dielectric or of the resin in which they are immersed or poured, these glass elements possibly being like cork coated to increase their solidity or to agglomerate them into volumes of determined shape and dimension and filled with an insulating gas. 7- transformer tank according to claim 1 characterized in that the two ends (24) of the radiator plates are crushed along an oblique or a curve to facilitate the circulation of the dielectric by eliminating two dead angles, the parts thus crushed serving to thermal dissi¬ pation and can be folded at an angle to facilitate the passage of air powered by the fan and increase the thrust on the blades of the turbine.

8- transformer tank according to claim 1 characterized in that to obtain a height or a specific cooling capacity, the radiators can be stacked end to end and made removable without stopping the transformer by placing in the conduit (4) leading to the tank and in the receiver duct of the tank (42) two valves capable of ensuring thermoregulation.