|
(11) | EP 0 629 825 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||||||
| (54) | Evaporative condenser made of plates for freezer installations |
| (57) A condenser made of plates, applicable on all freezer installations, consists of
a frame on which there is incorporated a battery of plates composed of stainless steel
sheets which are welded and perimetrally arranged in vertical and parallel sense,
on which there are arranged water carrying channels, this water falling on the outer
surface of the plate in divergent directions, and being recovered through suction
pumps which are attached to inlets incorporated in a collecting tray recycling the
used water, and the plates having inputs and outputs connected to appropiate channels,
the input channel, previously incorporated in the plate inlet, having a venturi in
which the gas carried from a compressor is cooled. |
BACKGROUND OF THE INVENTION
[0001] The present specification refers to a patent of invention related to an evaporate condenser of plaques, applicable on the whole freezers installations, the obvious purpose of which is to adequately operate in a freezer installation, the condensation tubular bundle being replaced by heat-exchangers of plaques.
FIELD OF THE INVENTION
[0002] This invention applies to the industry devoted to the manufacture of the whole freezers installations.
RELATED ART
[0003] As is well known, a condenser on a freezer installation is configured as a heat-exchanger, the evident purpose of which is to transfer the heat-resistant flow of a refrigerant fluid to an outer medium, that is to say, water, air, and so on.
[0004] Consequently, it is fully essential that this apparatus will have a good global coefficient of heat transfer so that the passing of the heat flow of a refrigerant fluid to an outer medium can be attained under a fixed surface of the apparatus, with a temperature differential to be as low as possible.
[0005] The fundamental functions performed inside the condenser are as follows, i.e:
- To cool the compressed steams from the unloading temperature of refrigerating compressors until attaining the condensing temperature of the freezing fluid.
- To condensate the steams cooled at the condensation point.
- To eventually undercool the condensate.
[0006] Consequently, a condenser can be divided into three zones, i.e:
- A cooling zone of overheated Steams.
- A condensation zone.
- An undercooling zone of the condensate.
[0007] In each of the above-mentioned zones, that is to say, in the cooling zone of overheated steams, in the condensation zone or the undercooling zone of the condensate, the conditions of the heating flow transfer are, consequently, different.
[0008] Likewise, the partial heat transfer coefficient (K = amount of heat transferred per m² of surface, per hour and per degree of difference between the temperature of the refrigerant fluid and the temperature of the outer cooling medium is, also, very different in each of the mentioned zones, the coefficient K of the first zone, i.e. the cooling of the compression overheated gases being lower, in any case, than that of the other zones, but, neverless, the heat transfer process of the refrigerant fluid to the condensation medium is identical in the mentioned three zones.
[0009] Upon considering the section of the transfer surface of a condenser, independently of the operating zone where this consideration upon the section is made, the following will be clearly defined:
A.- On the freezing side, and under circulation, when the freezer is permanently running, it has, in this particular point, a fixed speed V₁ (m/s) and a temperature 0₁º C.
B.- Outside the transfer surface, the condensation medium, which, under the same operating conditions, has a speed V₂ (m/s) and a temperature 0₂º C.
[0010] Obviously, both streams of fluids are separated by a metallic wall, the thickness of which is "e" millimeters, and it is surrounded on both faces and permanently wetted by the circulating fluids.
[0011] Under these conditions, the thermal change is as follows, i.e:
- Through convection of the refrigerant fluid in the inner surface of the condenser.
- Through conduction thru the separation metallic wall.
- Through convection of the outer surface of the condenser to the condensation medium.
[0012] In practice, the operating conditions are such that, in spite of the precautions to be essentially taken to keep fully clean the exchange surfaces, there is always an amount of atmosferic dust in the case of air condensers, or of incrustation in the case of water condensers, substantially increasing the separation wall - thickness on the outer face, and on the inner face a film from the oil drawn by the refrigerant fluid is formed, and it has been checked that these elements render difficult the passing of the thermal flow according to thickness and its own thermal conductivity.
[0013] The thermal change is really performed as follows:
- Through convection of the refrigerant fluid with the oil film surface on the inner wall of the condenser.
- Through conduction between different superimposed layers, that is to say, oil/metallic wall of separation/incrustation or dust.
[0014] Obviously, oil, incrustation or dust are less heat-conductive than metal, for which reason it is fully essential to keep totally clean the surface wetted by the condensation medium, eliminating, in a more known and efficient possible manner the existence of any incrustation trace.
[0015] With regard to the oil film formed inside the conduits owing to the adherence of this product drawn by the fluid, it has been shown that, in spite of the presence of a fully efficient oil separator in the compressor (i.e. the discharge side) of the installation, it is totally impossible, in practice, to eliminate said oil film.
[0016] The heat flow absortion due to cooling, condensation and under-cooling of the refrigerant fluid, can be only achieved at the condensation medium by rising its temperature, that is to say, by a perceptible heat absortion or a partial change of the physical state, i.e. latent evaporation heat.
[0017] On account of the above exposed, in relation to both heat absortion processes by a fluid, condensers can be clasified in the following manner, i.e:
- Heat sensitive condensers, and
- Latent heat condensers.
[0018] From the heat sensitive condensers, it is known the existence of air heat sensitive condensers and water heat sensitive condensers.
[0019] In the range of air heat sensitive condensers, there are those the air circulation of which is natural, and those the air circulation of which is carried out by forced circulation.
[0020] In relation to the water heat sensitive condensers, there are those known as dipping condensers, backcurrent condensers of dual tube and horizontal multitubular condensers.
[0021] Amongst the latent heat condensers, there are those known as atmosferic ones and forced evaporation ones.
[0023] Nevetheless, in the case of atmosferic latent heat condensers, there are known the vertical multitubular ones, the rain ones, the bakcurrent rain ones.
[0024] However, in the present case, the following is a survey of the evaporate condensers, and it is specifically convenient to point out the these condensers are fundamentally composed of a series of tubes that, according to the nature of the fluid to be flown inside them, they can be made of steel (n/H₃) or copper (freons).
[0026] In the second case, when the tubes are made of copper, they can be protected by an antirust treatment.
[0027] These tubular conduits are configured as vertical tubular coils, and several rows of coils are united on the upper part by using a gas inlet collector, while they are united on the lower part by a liquid outlet collector.
[0028] This type of condensers incorporates always water recirculating circuits, having a centrifugal pump fitted with appropiate means in order to adapt itself to the capacity of the condenser, and having an adequate number of sprinklers to bath the whole surface of the tubular bundle and a network of water distribution and interconnection pipings going from the pump to the sprinklers.
[0029] The evaporate condensers have fans incorporated, the function of which is to carry out an air forced circulation through the tubular bundle in order to cause a partial evaporation of the recirculated water and to cool, consequently, the remaining water.
[0030] This type of condenser is fitted with a wrapping and a tank for water recovery, the wrapping being generally made of a metal material, this installation being fully necessary to achieve an optimal air and water circulation, avoiding external water splashes.
[0031] The wrapping acts, at the same time, as a supporting element to assemble the three above-mentioned elements, and its base incorporates a tank for water recovery from which the water recirculating pump absorbs water.
[0032] This tank has a float valve in order to keep and adequate and steady level and, consequently, allow a similar amount of liquid to be added later to compensate water losses due to evaporation.
[0033] In general, the materials used for constructing the above-mentioned elements would be as follows:
- The sprinklers are made, in general, of brass, bronze or plastics.
- The wrapping and the drop separator are made of sheet and steel profiles, which, after being finished, are protected against rust by applying them a thermogalvanic treatment.
- The fans are usually coated with a chromium electrobath.
[0034] The running range will depend essentially on the hydrometric degree of the air admitted into the condenser, bearing always in mind the weathering conditions of the location where the apparatus is to be installed. Obviously, the condensation point will range between 10ºC and 12ºC above the temperature of the wet - thermometer of the ambient air.
[0035] The operating system utilized is based on a partial evaporation of the water sprayed on the tubular bundle of the condenser, since the amount of the recirculating water is constantly enriched with mineral salts which, upon contacting the heat-exchange surface, react , forming:
A.- Incrustation deposits which, obviously, is a very bad heat conductor in relation to metal, so forming an insulating layer the thickness of which is increasing growing, so causing a decrease of the global coefficient of transfer of the condenser.
B. Incrustations of mud and sludge which are considered as corrosive and gradually damage the conduits.
[0036] When the water heats or evaporates, the formation of insoluble incrustations causes serious problems in the freezers installations, since the heat transfer capacity decreases consequently.
[0037] The deposition of incrustations more currently determined is that formed by calcium carbonate, although it is also possible to find small amounts of magnesium carbonate and calcium sulphate.
[0039] The polyphosphates used to avoid depositions of calcium carbonate incrustations can precipitate and form calcium phosphate deposits.
[0040] The calcium carbonate and calcium sulphate solubility -two substances incorporated in water in solution conditions- decreases with the increase of temperature.
[0041] In a same water system, incrustations are very easy produced on hot surfaces, such as those of condensers.
[0042] These deposits of incrustations can be able to determine at once the breakdown of the freezing system in order to clean the condenser when the loss of capacity exceeds allowed and admissible limits.
[0043] In this point, please refer to the graphics incorporated in pages 5-4 and 5-5 of the Conditioned Air (Carrier) Manual.
[0044] Obviously, it is known the existence of a series of additional operations, all them dedicated to carry out an external and internal cleaning of circuits in order to restore them the own characteristics of a new erected installation, that is to say, by obviathing the existence of both external and internal deposits, and, when eliminating these deposits, to secure that the temperature transfer is ideal, so obviating the need to increase the running or operation power to obtain similar results, which, sometimes, are proved as a total breakdown of the equipment because of the need to carry out an integral repair of channelings or to replace them.
[0045] The existence of leaks arising from the mentioned anomalies is also very frequent in this type of installations.
[0046] Consequently, and in view of that above-mentioned, an evident solution to the existing problems in this matter would be to rely on an equipment fitted with an evaporate condenser, which would be adequately able either to avoid the existence of the above-mentioned deposits and adherences, or to allow, due to its physical shape features, an easy access to those points of the installation requiring a maintenance service in a cadenced way.
[0047] Nevertheless, up-to-date nothing is known about the existence of an evaporative condenser fitted with those features pointed out as suitable.
SUMMARY OF THE INVENTION
[0048] The evaporate condenser of plaques, applicable on the whole freezers installations as proposed by the invention constitutes, per se, an evident solution to the present problems in this matter, since starting from it, it is obviated, in a clear and specific manner, the existence of adherences to the surface of circuits incorporated in freezers installations, and, at the same time, it is possible to configure an installation of easy access to carry out, on it, maintenance operations, among which the possibility of the need to carry out the elimination of those adherences which could deposit on same in a casual manner due to any operating anomaly on the whole installation.
[0049] In a more definite way, the evaporate condenser of plaques, which is the subject-matter of this invention, is fundamentally configured as a condenser of evaporative type, the condensing tubular bundle of which has been replaced by an assembly of heat-exchangers which is formed by a series of plaques.
[0050] The plaques in question are used as heat-exchange elements, which are composed by two stainless steel sheets, which have been adequately perimetricaly welded, and also in adequate points on its surface, a wheel electrowelding being used in these welding operations performed in inert atmosphere.
[0051] After the welding, the plaque -composed of two stainless steel sheets- is subjected to an internal pressure until obtaining a permanent deformation, similar to a swelling, through which a coil-type circuit is made, located between said metal sheets, through which the refrigerant fluid will flow.
[0052] Both the surface of the plaques and their circuitry will vary according to the application to be given.
[0053] The plaques are fitted with an inlet pipe and an outlet pipe, which are joined on the evaporate condensers to an inlet collector and other collector the function of which is to collect the falling water, so forming a vertical plaque battery, the plaques being located parallel one other, at an always fixed gap in relation to one other, in order to permit, on a side, the air and recirculated water fluids to pass therebetween.
[0054] The transfer surface is constituted, by both sides of the plaque in question and, therefore, the number of units of the battery of plaques will depend, consequently, on the need for exchange required by the condenser.
[0055] In relation to the water recirculation, the lower part of the wrapping constitutes a tank for water recovery, from which the recirculating pump or pums will absorb the water, sending it directly to a water distributor which is located at the upper side of the plaque battery, and which has been designed so that it allows the water to be equally distributed to different plaques, and, when leaving same, the water falls like sheets adhered to both faces of the plaque.
[0056] The air, circulating in equicurrent, at the same sense than the water, and being forced by two centrifugal or axial blowers, causes a partial water evaporation on the surface of said water batteries, cooling the remaining water this having a temperature of 5ºC higher than the temperature shown in the wet thermometer of ambient temperature.
[0057] The condensation point attained is above 10ºC on said value, this parameter being similar to that the present evaporate condensers fitted with a tubular bundle.
[0058] This arrangement, appropiate to bath the heat transferring surface, prevents the formation of water evaporation on the metallic surface of same, with no incrustation deposits and, consequently, the heat transfer capacity is not gradually impaired.
[0059] As described above, a part of the condenser which is the subject matter of the invention serves for cooling overheated steams coming from the discharge of compressors at temperatures ranging between 63º and 110º above zero.
[0060] The evaporate condenser of plaques is fitted with a venturi-type liquid recirculation system through which a portion of the condensate mixes with the overheated steam at the condenser inlet, reducing its temperature until that of the condensation, i.e. up to +36ºC, which causes an increase of the heat transfer coefficient in the cooling zone of overheated steams, upon replacing said overheated gas by a condensate gas mixed with liquid coolant and, therefore, a substantial improvement of the global performance of the condenser.
[0061] Likewise, the temperature decrease of the inlet gases increases the calcium carbonate and calcium sulphate solubility carried by the recirculation water in solution, for which reason, the risk of incrustations inside is reduced.
[0062] The wrapping is composed of stainless steel sheets and profiles, and it is designed so that it allows to support all elements composing the condensating unit, forcing the air to pass vertically downward the battery of plaques water bathed, and changing the sense and reducing the air speed in question in order to separate the water drops drawn before being absorbed by the blowers or fans located on the upper side of the condenser in two inclined planes throwing air in a divergent direction.
[0063] The unit is fitted with registry doors and, inside, the sheets surrounding the battery of plaques are fully detachable to provide access to said battery for eventual maintenance or inspection purposes.
[0064] The lower part constitutes, as said above, a tank for water recovery, and it is fitted with a float valve for providing water and replenishing losess due to evaporation, drop dragging and deconcentration drainage.
[0065] This punctual maintenance and repair operation cannot be carried out on the present evaporate condensers owing to the construction of the tubular bundle and condenser wrapping, since there is only one access to the outer surface of the pipes of the rows located on the upper and lower zones, for which reason, any mechanical cleaning, i.e. by threading, high pressure cleaning, and so on, is fully impossible.
[0066] The cleaning system used is chemical, that is to say, recirculating a mixture of acids making use of the water recirculating circuit of the condenser, to try to dissolve any deposit of incrustations, this cleaning being performed in a partial way, since the lower part of the pipes remaining in the acid mixture shaded area recirculated that, by gravity flows from top to bottom, cannot be deincrusted.
[0067] If the chemical cleaning time is extended trying to make it most efficient, corroding attacks against the materials constituting the tubular bundle and wrapping can be produced, damaging the protection of zinc bath, and, later, the steel of the tubes forming the tubular bundle and eventually causing leaks in them.
[0068] Due to a remaining dirtiness, the condenser does not recover its initial efficiency, which causes a permanent increase of the condensation point and, therefore, a loss of Kw/Fr/h performance of the compressor unit ranging from 3.6 to 4% per each increase of ºC of said condensation point.
[0069] Owing to this condenser shape, its complete cleaning is effective and possible due, on the one hand, to the materials used in its construction, and, on the other hand, to the easy access to same.
BRIEF DESCRIPTION OF THE DRAWINGS
[0070] In order to complement this description and to aid to a better understanding of the features of the invention, the accompanying drawings, which are a part of this specification, show in an illustrative but non limitative sense, the following:
Figure 1 is an elevational view of the evaporate condenser of plaques, applicable on the whole freezers installations, of the present invention.
Figure 2 is a plan view of the subject shown in Figure 1.
Figure 3 is an elevational view of a connecting pipe used for interconnecting the plaques at the inlet of gases or fluids arising from a compressor.
Figure 4 is a plan view of the subject shown in Fig. 1.
Figure 5 is an elevational view of a pipe interconnected at the outlet of plaques.
Figure 6 is a view in detail of a discharge collector incorporated in an interconnection piping with the plaques placed at the inlet shown in Figs. 3 and 4.
Figure 7 is a view corresponding to a discharge collector with its appropiate drainer installed on the connection of the piping fixed to the plaques in inlet points, shown in Fig. 5.
Figure 8 is a detail duly sectioned of the pipes shown in Figs. 3, 4 and 5, specifically, a top view.
Figure 9 is a detail of the subject shown in Fig. 1, specifically its lower portion or tank of water recovery and recycling.
Figure 10 is a view of the upper side of the condenserm specifically the pipes recycling the water and, later, transferring it toward conduits connected on the upper part of the freezing plaques.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0071] From these figures, it can be seen how the evaporate condenser of plaques, applicable on the whole freezers installations (1) is constituted starting from the incorporation of a non determined number of trays (2), which will act as elements of heat-exchange, which are composed starting, from two stainless steel sheets which are perimetrally welded in an appropiate way, and also in different points on their surface by means of wheel electrowelding, this operation being always performed in an inert atmosphere.
[0072] There are plaques (2) incorporated on a metallic structure or frame (3), consisting of an indeterminate number of parts the function of which is to support the whole assembly used for configuring the evaporate condersed of plaques itself, having on the lower portion a part (4) on which the whole assembly is supported and adapts itself adequately to a second structure (6) having rigidizing and immobilizing lines and recesses (8), counting on some parts that, as pilasters or supports (7), hold the whole assembly inside a tray (5) in which the water used as freezing element and antitank of the plaques (2) falls gradually.
[0073] The plaques (2) are joined at their mouths to fluid conduits (9) arising from a compressor, these plaques having at their outlet line a second conduit (10), to which all the mouths corresponding to the outlet opeanings installed on the lower zone of the plaques in question are welded.
[0074] The used water falls within the tray (5) and by means of pumps (11), this water is recycled through inlets (16) towards conduits (17) and (18), to which conduits (19) and (19') are interconnected, which convey the water to secondary channelings (21) which are longitudinally multiperforated at their lower side, conveying the water in a harmonic way and forcing the water to fall on hollow parts (20) that, acting as channels, cause the water flow, as a rain or shower, to fall on the plaques (2), and thank to the action of blowers or fans (12) the plaque is freezed, and, at the same time, the water temperature decreases. So, two defined and determinate purposes are obtained: to drop the temperature of the gas contained inside the plaques (2), and to avoid the existence of deposits outside due to the presence of an external water film formed by the water curtain from the channelings (20), this water watering or wetting the surface thereof. This continuous shower of water, externally refrigerated by said blowers (12), obviates the existence of adherences.
[0075] The water falls on a collecting tray (5) and it is recycled again, the necessary amount of water being added continuously in order to replenish its level by means of a level float which determines the addition of evaporated water, this cycle being continuous.
[0076] That is to say, the assembly formed by the tray (5), the pumps (11), the inlets (16), the conduits (17) and (18), the channelings (20) and the pipes (21 interconnected to channelings (17) and (18) in cooperation with conduits (19) and (19'), form a continuous cycle of rain on the plaques (2), so achieving that the condenser acts with no problems at all.
[0077] The conduits (9) and (10), by which the gas flows towards the plaques and the refrigerated gas gets out towards the corresponding place, have appropiate drainers and vacuum cocks (13) and (14) installed, respectively, on conduits (9) and (10).
[0078] The ends of these conduits have a closing or blind element (15), such as is shown in Fig. 3, in the detail corresponding to "C".
[0079] Lastly, it must be pointed out that the evaporate condenser of plaques (1), which is the subject-matter of this invention, has a liquid recirculation system formed starting from a venturi by which a part of the condensate is mixed with the overheated steam at the condenser inlet, reducing its temperature until obtaining the condensation point causing an increase of the heat transfer coefficient in the cooling zone of overheated steams, and, at the same time, the dropping of the gas temperature increases the calcium carbonate and calcium sulphate solubility which are conveyed by the recirculation water, so decreasing any risk of the formation of incrustations inside.
[0080] It is not considered necessary to extend more this description for an expert in the art to understand the scope of the invention and the advantages derived from it.
1. An evaporate condenser of plaques, applicable on the whole freezers installations,
of those constituted starting from the incorporation of an indeterminate number of
plaques (2), located in parallel and vertically, configuring heat exchange elements
formed by two stainless steel sheets, which are welded perimetrically and in different
points of their surface by means of wheel electrowelding in an inert atmosphere, characterized
in that the plaques (2) are fitted with an inlet pipe directly connected to a multiperforated
channel (9), fitted with a draining and control valve (13), having at its ends a blind
closing (15), while the outlet mouths of the plaque (2) are connected to a second
channel (10) having an appropiate drainer (14) and having, at its ends, a blind closing
element (15), the piping (9) being connected to the overheated steam conduit from
the discharge side of compressors, and a venturi being arranged in the conduit towards
the plaques. Within said venturi a part of the condensate is mixed, at the condenser
inlet, with overheated steam, reducing its temperature until reaching 36ºC, the overheated
gas being mixed with the liquid coolant, passing later inside the plaques (2).
2. An evaporate condenser of plaques, applicable on the whole freezers installations,
according to claim 1, characterized in that the plaques (2) are incorporated and adequately
arranged on a frame (3), which is fixed to a lower part (4) located on the upper zone
of a liquid collecting tray (5), firmly fixed at its lower side on a complementary
frame (6) fitted with a series of crevices in which angular projections (8) are inserted,
the frame or structure (3) having supporting feet or a support (7) acting as posts,
the frame (3) having doors acceding inside, which are fully openable.
3. An evaporate condenser of plaques, applicable on the whole freezers installations,
according to claim 1, characterized in that the plaques (2) are refrigerated by means
of a water curtain from channelings (17) and (18), which are interconnected to conduits
(19) and (19') carrying the cooling water to pipes (21) arranged in parallel on the
upper side of the plaques (2). These plates are multiperforated, the water passing
through them and falling in a dimensioned way on the whole surface of channelings
(20)fixed on the upper side of the plaques, also multiperforated, the water emerging
outside through the perforations of the parts (20) and falling as a rain or shower
on the external surface of the plaques (2).
4. An evaporate condenser of plaques, applicable on the whole freezers installations,
according to claim 3, characterized in that the water falling on the external surface
of the plaques (2) is refrigerated by blowers or fans (12) arranged on the upper side,
which air flow or current falls directly upon the area where the plaques are to be
installed (2).
5. An evaporate condenser of plaques, applicable on the whole freezers installations,
according to claim 3 and 4, characterized in that the water freezing the external
surface of the plaques (2), assisted by the flow from blowers (12), falls in a collecting
tray (5) having liquid inlets (16) connected with suction pumps (11) transferring
the recovered water to the conduits (17) and (18) arranged on the upper part of the
condenser.
6. An evaporate condenser of plaques, applicable on the whote freezers installations,
according to claim 5, characterized in that the tray (5) has a level float interconnected
with an inlet of the health network, allowing the water to pass within the tray (5)
when the existing level of same decreases due to evaporation.
7. An evaporate condenser of plaques, applicable on the whole freezers installations,
according to claim 1, characterized in that the wrapping or structure is configured
by using stainless steel sheets and profiles, the same being fully detachable.
8. An evaporate condenser of plaques, applicable on the whole freezers installations,
according to claim 5 and 6, characterized in that the water curtain formed by the
falling of the water conveyed by channelings (20) falls on the plaques (2) in divergent
directions, watering alternatively the outer surface of the plaques sideways fixed
to the plaque carrying the channeling located on its upper part.