EP0959307A1 - Sorption plate heat exchanger - Google Patents

Abstract

An air conditioning system has plate type heat exchangers to exchange heat between the incoming air flow and the expelled air flow to conserve energy. The incoming air is dehumidified using hydroscopic liquid sprayed over the plate heat exchangers. Liquid which drains off the heat exchangers is collected and recycled, ie. the water is removed by heating. The liquid is cooled and recycled to the heat exchangers.

Description

The invention relates to a method for drying or drying and Cooling from at least one plate heat exchanger into a room directed air, with a liquid, hygroscopic sorbent.

The common term air is here and in the following for simplicity's sake atmospheric outside air, process air and others to be dried or to used drying and cooling gases. Under a room becomes a closed Volume understood, which is a room of a building, a Vessel or a defined body content in general means.

For air conditioning of living, working and storage rooms as well as temperature-sensitive Objects are heated and / or depending on the sensitivity level Refrigeration systems used, which not only for heating, but also to cause a relatively high energy consumption for cooling. in the Framework of increasingly harsh environmental conditions, coupled with the long-term rising energy costs, the recycling principle has on this Territory. The escaping exhaust air is depending on the season used for precooling or preheating the outside air. To achieve a the highest possible efficiency, the two air currents are more strict Separation with the largest possible exchange surfaces passed through each other. The plate heat exchangers which are frequently used work in known manner after the counter or after the cross flow principle.

The constantly increasing demands on a comfortable living quality can however, are no longer fulfilled by exclusive heating and cooling, Air conditioning also includes regulation of humidity. In particular In the hot season, the demands on air conditioning include one Reduction of humidity, which increases relatively when cooled. at The dehumidification of the outside air does not only become solid, hygroscopic materials used, but also liquid sorbents. Saturated solutions of hygroscopic salts dissolved in water lower the moisture content of passing air by absorbing or condensing water becomes. As with any condensation process, this creates heat, which however, because of the greater absorbency at lower temperatures is undesirable.

Sorbents known per se are saturated solutions of salts of Alkali and alkaline earth metals, for example lithium chloride and / or calcium chloride. In addition to the absorption capacity also play in the selection Factors, such as environmental compatibility, toxic Actions and not least the price.

For the understanding of the driving force in an absorption process in which Practice usually briefly referred to as Sorptionsvorgang, is the knowledge of Vapor pressure above the liquid level of great importance. A good Sorbent has a lower vapor pressure than water in air. at a greater difference, the sorption is higher.

Sorption systems are generally known for dehumidifying air, in which the mass and heat transfer during absorption via suitable Exchange surfaces of packages takes place. The saline solution is determined by means of suitable Spraying devices distributed over the exchange surfaces and flows in countercurrent in the direction of gravity. For example, a pack consists of Packings, such as Raschig rings, Pall rings, Intalox saddles or Berl saddles.

By absorbing atmospheric moisture becomes the hygroscopic saline solution diluted until it can absorb significantly less or no more water.

Cheap and ecologically harmless saline solutions are based on the one-way principle used and disposed of. This applies, for example, to an aqueous one Calcium chloride solution too. In contrast to that in this sorption technology Often used lithium chloride, calcium chloride is non-toxic and even fully food grade. In addition, calcium chloride is much less corrosive as that too harmful lithium chloride. With lithium chloride can be reached a lower dew point than with calcium chloride. Against, and this is Also important for economic processes, calcium chloride is essential cheaper than lithium chloride. Finally, calcium chloride can be used in winter service Frost-free roads can be used in large quantities.

Another advantage of liquid hygroscopic sorbents is in that when supplying outside air into a room a perfect Sterilization of the supply air is ensured, which is especially true of inhabited or other rooms with a special purpose is of importance.

With a rotating sorption dehumidifier, the sorption wheel known per se, can the condensation heat generated during dehumidification which greatly reduces the water absorption of the sorbent, not sufficient be dissipated. In addition, there is the so-called drag heat through the regeneration.

The increasing density of regulations in all areas is also contributing The regulations on the dehumidification of outside air do not stop. For example in Germany (except coastal areas) according to DIN 4710 (11.82) for Dehumidification of the outside air to 8 g / kg with 2900 dehumidification hours be calculated to the above maximum outside air condition to reach. This means that mainly in the summer months must be dehumidified, according to statistics for 71 days. The average Exposure during these 71 days is only about 24% of the maximum Dehumidification.

The inventor has set himself the task of a method and a device to create the type mentioned, which is the dehumidification Enable air without the usual warm-up in a simple, economical way.

With regard to the method, the object is achieved according to the invention, that the air on the input side of a plate heat exchanger with the liquid, hygroscopic sorbent in the flow direction continuously or periodically sprayed and the heat of condensation while maintaining a practically isothermal dehumidification of the air is continuously discharged. Specific and further embodiments of the method are the subject dependent claims.

The plate heat exchanger used to carry out the process according to the invention is usually a cross-flow, but can also be a Countercurrent exchanger be known per se. Material must the requirements for corrosion resistance are met.

• Das aufgesprühte Wasser darf nicht abtropfen.
• Die luftbestrichenen Flächenelemente müssen jedoch bis zum nächsten Besprühen feucht bleiben.

The heat of condensation formed during the sorption process can be met particularly advantageously while maintaining a virtually isothermal dehumidification of the air, when a fine spray of treated water is sprayed into the cooling air flow channels on the input side of a crossflow heat exchanger at equal time intervals. Two conditions must be met simultaneously:

• The sprayed-on water must not drip off.
• The air-coated surface elements, however, must remain moist until the next spraying.

These conditions are fulfilled by a program-controlled migration and cooling water spraying nozzle bar or a correspondingly controlled matrix-shaped nozzle field. The cleaning of the cooling air flow channels done by flushing out at the end of a working period.

This preferred cooling method has the great advantage that no cooling water drips and so the sorbent further diluted and the regeneration at most difficult and more expensive. For details regarding a plate heat exchanger with the mentioned wetting submissions is to the WO, A1 96/22497.

The preferably saturated sorbent solution is continuously or in relatively short time intervals of a few seconds to a few Minutes, suitably 10 seconds to 3 minutes, into the sorption flow channels sprayed. By the condensation of humidity is dilutes the sorbent, it flows more solution from the channels than is sprayed.

Cheap, ecologically safe sorbents, such as a aqueous calcium chloride solution, are discharged directly into the sewer or a meaningful third use supplied.

In general, the diluted from the sorption flow channels dilute Sorbent collected for desorption of the absorbed Water is heated and / or the overlying cavity partially evacuated. The Procedure is programmed so that the recorded during the sorption process Amount of water is expelled again. The concentrated in the saturated area Saline solution is under refrigeration for reuse in the input side Passed spray nozzles of the plate heat exchanger and again returned to the cycle.

Regeneration is essential in hygroscopic saline solutions which reused because of their environmental impact or their high price be or have to be. By evaporation or other expulsion of Water is the aqueous salt solution, also called brine, back in their saturated returned to its original state and reused.

According to the known state of the art, to obtain a specific Air condition with a refrigeration system are initially cooled so far that on or immediately above the dew point line, a point below the desired one Air condition is achieved. By heating the air with a normal, hot water operated heater then becomes the desired air condition reached. This method is energetically complex and complicated.

In contrast, after a further development of the invention, for example For the air conditioning of inhabited rooms, the air for the time being at one Temperature of 30 to 35 ° C, especially at about 32 ° C, almost isothermal dehumidified. In the case of isothermal dehumidification, the temperature fluctuations are within a range of ± 2 ° C, preferably ± 1 ° C. In an isothermal Dehumidification in the temperature range of about 32 ° C, at about 40% relative Moisture, which corresponds to about 12.7 g of water / kg of air, takes up the sorbent about half of the humidity at a final temperature of also about 32 ° C, the relative humidity is still 26.6%, which is about 8g Water / kg of air corresponds. In a sorption without cooling, the Supply air instead of isothermally adiabatically warm to over 42 ° C. Because on both Sides of the plate heat exchanger energetically with a state change (Condensation and evaporation) is worked, it is possible the dehumidification process allow isothermal drainage.

The dehumidified, with respect to the room temperature still too warm air can now cooled by evaporative cooling in a second plate heat exchanger be, preferably by the above-described special evaporative cooling. So the temperature can be around 5 to 15, preferably around about 10 ° C, lowered and the desired room temperature can be achieved.

If the optimum humidity is not yet present after this cooling, then can be at a pre-calculated temperature above the desired Cooled room temperature and then with further cooling at constant Enthalpy be moistened again in a second heat exchanger. Cooling with humidification, however, becomes clear before reaching completed the dew point line. Cooling at constant enthalpy by moistening is for example 2 to 10 ° C, especially about 5 ° C. The approach to the dew point line is expedient at most about 2 ° C.

With respect to the device for carrying out the method, the object solved according to the invention that a sorption to the Drying or drying and cooling of air at least one corrosion resistant Plate heat exchanger with an input side of the sorption flow channels arranged spray nozzle beam or a spray nozzle matrix for the treated sorbent and an input side of the cooling air flow channels angeordenten spray nozzle beam for the cooling water, a Drip tray for the dripping, diluted sorbent and a treatment loop for the sorbent with a desorption device, a cooling device and a pump. Special and further education Embodiments of the device are the subject of dependent claims.

The plate heat exchanger is preferably constructed of plastic films. Particularly suitable are plate heat exchangers with alternating, themselves crossing sorption and cooling air flow channels. Unlike metallic Materials for the plate heat exchanger may be the plastic plates be made thin only because of their low thermal conductivity, for example, from tear-resistant plastic films of a thickness in the range of 0.1 to 1 mm, in particular 0.5 to 0.7 mm. With correspondingly greater thickness these can also be provided with covered metallic reinforcements, For example, films or crossing threads.

The inventive method and the associated device allow with simple means to dehumidify large volumes of air simply and inexpensively and where necessary or desirable to cool. Reaching the dew point line is avoided in all process steps. Thanks to the brine, the is either disposed of or regenerated, is also a perfect germ free the supply air ensured.

• Fig. 1 eine Sorptionsanlage mit einem Plattenwärmeaustauscher,
• Fig. 1a ein Detail des Wärmeaustauschers gemäss Fig. 1,
• Fig. 2 eine Sorptionsanlage mit zwei Plattenwärmeaustauschern,
• Fig. 3 eine Variante von Fig. 2,
• Fig. 4 ein Mollier-h-x Diagramm für feuchte Luft, und
• Fig. 5 eine Variante von Fig. 4.

The invention will be explained in more detail with reference to embodiments shown in the drawing, which are also the subject of dependent claims. They show schematically:

• 1 shows a sorption with a plate heat exchanger,
• 1a is a detail of the heat exchanger according to FIG. 1,
• 2 shows a sorption plant with two plate heat exchangers,
• 3 shows a variant of Fig. 2,
• Fig. 4 is a Mollier-hx diagram for humid air, and
• 5 shows a variant of Fig. 4th

A sorption system 10 shown in FIG. 1 with cooling possibility comprises as a core piece for sorption-assisted air conditioning a plate heat exchanger 12. This is designed as a cross-flow heat exchanger and module-shaped constructed of plastic films. This type of heat exchangers is in itself well known, for example from EP, B1 0449783 and WO, A1 96/22497. However, because of the low susceptibility to corrosion Plastic films are preferred despite the lower conductivity compared to metal foils.

The moist outside air 14 flows through, as indicated in FIGS. 1 and 1a arranged in parallel sorption flow channels 16 and are as dried Supply air 18 in a room 20, for example, an inhabited room, headed. By alternately arranged between the sorption flow channels 16 Cooling air flow channels 22 also flows moist outside air 14 through the cross-flow heat exchanger 12 and occurs as heated cooling air 24 back to the atmosphere. Correspondingly, the in the cooling air flow channels 22 incoming outside air 14 also be exhaust air, the heated Cooling air 24 is the exhaust air in this case.

The plate heat exchanger 12 forming plastic films 28 are according to Fig. 1a arranged such that the flow channels 16, 22 each closed alternately in a direction of flow for the outside air 14 are.

On the inlet side of the sorption flow channels 16, a migrating spray nozzle bar 26 (WO, A1 96/22497) or a spray nozzle matrix 30 is arranged, which sprays a liquid, hygroscopic sorbent 32 into all sorption flow channels. In the present case, the sorbent 32 is an aqueous, saturated CaCl ₂ solution. As it flows through the sorption flow channels, the sprayed sorbent 32 absorbs moisture from the outside air 14 and dries it, releasing heat of condensation. In the course of flowing through the sorption flow channels, the atomized sorbent is deposited on the plastic films 28 and can - if still sufficiently concentrated - take up residual moisture. The surface of the plastic films of the plate heat exchanger can be made enlarged, for example by roughening or velor coating. The increased surface area with a layer of sorbent intensifies the sorption process. In a wandering spray nozzle bar 26, the moisture absorption takes place predominantly by precipitated sorbent 32. From the plate heat exchanger 12 exits dried supply air 18, which for example still contains half of the original moisture. Further drops from the plate heat exchanger 12 diluted sorbent 34 from.

The invention essential advantages, a higher specific dehumidification performance and a virtually isothermal dehumidification process can only be achieved when the condensation heat is dissipated optimally.

According to the example of Fig. 1 is therefore the input side of the cooling air flow channels 22 (Fig. 1a) also a spray nozzle matrix or preferably a wandering spray bar 38 arranged, it is in this respect again expressly referred to WO, A1 96/22497. The incoming outside air 14 is added so much cooling water 36 that the output side drips nothing the plastic films 28, however, always remain moist.

• Im Winter zum Befeuchten der Aussenluft 14, indem durch den wandernde Spritzdüsenbalken 26 oder die Spritzdüsenmatrix 30 statt Sorptionsmittel 32 reines Kühlwasser 36 eingedüst wird.
• Zusätzlich zum Befeuchten kann die Aussenluft 14 durch Einleiten von Abluft in die Kühlluft-Strömungskanäle 22 vorgewärmt werden.
• Durch Einleiten von Kühlluft oder Warmluft in die Kühlluft-Strömungskanäle 22 kann eine reine Wärmeregulierung ohne Änderung des absoluten Feuchtigkeitsgehaltes der einströmenden Aussenluft erfolgen.

The plate heat exchanger 12 with the sprayers can be used versatile as needed:

• In winter for moistening the outside air 14, 32 pure cooling water 36 is injected instead of sorbent 32 by the migrating spray nozzle beam 26 or the spray nozzle matrix.
• In addition to humidifying, the outside air 14 may be preheated by introducing exhaust air into the cooling air flow channels 22.
• By introducing cooling air or hot air into the cooling air flow channels 22, a pure heat regulation can take place without changing the absolute moisture content of the incoming outside air.

In the area below the outlet openings for the supply air 18 is a trough 40th for the dripping dilute sorbent 34. The supply air 18 flows through a known droplet separator 42, which prevents that droplets of sorbent 34 remain in the supply air 18. To the Expelling the water condensed in the sorbent 34 is a treatment cycle 52, which comprises a brine / brine heat exchanger 44, a desorption device 46, a cooling device 48 and a pump 50 comprises the now re-enriched sorbent 32 in the range the plate heat exchanger 12 returns and thus the conditioning circuit 52 closes.

The desorption device 46 is in the present case as an evaporator 54 with a drain 55 and a heater 56 is formed. The heating takes place with However, steam could also be powered by electricity or to others known manner. The mid-range, preheated Dilute sorbent 34 is heated and by evaporation of water concentrated until the value determined by the process computer is reached.

The pre-cooled in the brine / brine heat exchanger 44 concentrated sorbent 32 is in the cooling device 48, a ventilated air cooler, on a optimal operating temperature brought.

Below the outlet openings for the heated cooling air 24 is a collecting tray 58 with a drain 59 for cleaning water of the cooling air flow channels 22 arranged. These channels will be washed out by the end of work (WO, A1 96/22497).

In Fig. 2 is a sorption with two plate heat exchangers 12, 12 ' wherein the preparation of the dilute sorbent 34 according to Fig. 1 is done and therefore not shown.

The first plate heat exchanger 12 substantially corresponds to that of FIG. 1. However, the cooling air flow channels 22 (FIG. 1a) are outflowing Exhaust air 60 exiting the space 20, which is sprayed with cooling water 36 and as exhaust air 62 exits into the atmosphere. The sprayed, with condensed Moisture of the outside air 14 diluted sorbents 34 is from a deflection 64 in the area above the tub 40 is deflected.

The dried outside air 14 is passed through a second plate heat exchanger 12 'out and dosed if necessary by spraying with cooling water 36 moistened. The entering into the space 20 supply air 18 is thus with respect to temperature and water content air conditioned.

Over the spray nozzle bar 38 'is cooling water at regular time intervals 36 sprayed, in compliance with the above-mentioned conditions of continuous moisturizing of the plastic films 28 (Fig. 1a), but without dripping.

Again, depending on the external conditions (season, weather conditions, etc.) are different Operating modes possible. The plate heat exchanger 12 can be switched off and with the heat exchanger 12 'by in the description of Fig. 1 mentioned operations are cooled and / or heated, without the absolute moisture content is changed. Likewise, the plate heat exchanger 12 'off and with the plate heat exchanger 12th dried or dried and cooled.

Another variant of a sorption with two plate heat exchangers 12, 12 'is shown in Fig. 3. The outside air 14 is as above shown before entering a first plate heat exchanger 12 continuously or periodically sprayed with liquid hygroscopic sorbent 32, wherein the outside air 14 is dehumidified. The over a mist eliminator 42 passed to a second plate heat exchanger 12 'and there cooled.

The exhaust air 60 from the space 20 divided into two partial streams. A first partial flow is after the periodic spraying with cooling water 36 through the first plate heat exchanger 12 and passes as exhaust air 62 in the Atmosphere off, analogous to a second partial stream 62 ', which for cooling through the second plate heat exchanger 12 '.

In the present case, outside air of 32 ° C with 12.5 g water / kg air is isothermal passed through the first heat exchanger 12. Through the sorption process the absolute humidity is lowered to 8g water / kg air, which Temperature remains, as mentioned, at 32 ° C. In the second plate heat exchanger 12 ', the partially dried air is cooled to 22 ° C, the absolute humidity stays unchanged.

In Fig. 4, a so-called Mollier-h-x diagram for humid air is a Air conditioning with a sorption plant 10 e.g. shown in FIG. 2 or 3. Humid outside air has a temperature of 32 ° C and an absolute Humidity of 12.8 g water / kg air. The humid outside air of a relative Humidity of 40% is achieved by sorption in a plate heat exchanger 12 is virtually isothermal by means of a sprayed sorbent dehumidified. The temperature rises slightly to 34 ° C, so it remains practical isothermal and in this first step to 6 g of water / kg of air dried. The relative humidity has dropped from 40% to below about 17%. By stronger cooling, this first step could easily be kept even more isothermal.

In a second step, the outside air is no longer dehumidified, only still cooled. As a result, the temperature drops at the same absolute humidity to 22 ° C. The relative humidity is now around 35%.

In a third step, the dehumidified and cooled air is through passed another plate heat exchanger and moistened and cooled there. The temperature drops to about 17 ° C, which becomes absolute humidity increased to 8 g of water / kg of air. The relative humidity is now just above 60%. This last step takes place at unchanged enthalpy, the curve runs parallel between two enthalpy curves 66 in the Mollier-h-x diagram. The dew point line 68 with 100% relative humidity is not reached.

On the basis of a further Mollier-h-x diagram, according to FIG. 5, a simplified, usually preferred variant shown in two instead of three steps. Moist outdoor air has a temperature of 32 ° C and a absolute humidity of 12.8 g of water / kg of air, giving a relative humidity of 40%. With an isothermal sorption process according to 1, the absolute humidity is lowered to 8 g of water / kg of air, the relative humidity has dropped to about 26%. In the second operation the air is lowered directly to the final temperature of 20 ° C without dehumidification, the relative humidity increases to about 52%.

Claims (10)

Method for drying or drying and cooling air (14) conducted into a space (20) via at least one plate heat exchanger (12), with a liquid, hygroscopic sorbent (32),
characterized in that
the air (14) on the input side of a plate heat exchanger (12) with the liquid, hygroscopic sorbent (32) in the flow direction continuously or periodically sprayed and the heat of condensation is continuously discharged while maintaining a virtually isothermal dehumidification of the air. Method according to claim 1, characterized in that in one Cross-flow plate heat exchanger (12,12 ') on the input side in the same Time intervals a fine spray of treated water (36) in the Cooling air flow channels (22) is sprayed, with no sprayed Water drips and the air-coated surface elements (28) to the remain wet after the next spraying. Method according to claim 1 or 2, characterized in that the from the sorption flow channels (16) dripping dilute sorbent (34) collected, for the desorption of the absorbed water heated and with cooling for reuse the plate heat exchanger (12). Method according to one of claims 1 to 3, characterized that the air at a temperature of 30 to 35, especially at about 32 ° C, isothermal dehumidified and by evaporative cooling the temperature by 5 to 15 ° C, in particular by about 10 ° C, is lowered. Method according to one of claims 1 to 4, characterized that the dehumidified or dehumidified and cooled air among others Cooling at constant enthalpy is moistened again, wherein Cooling and humidification well before reaching the dew point line (68) is completed. A method according to claim 5, characterized in that the temperature the air is lowered by a further 2 to 10 °, in particular about 5 ° C, but not more than about 2 ° C above the dew point line (68). Method according to one of claims 1 to 6, characterized in that as a sorbent (32,34) is sprayed a saturated solution of CaCl ₂ . Device for carrying out the method according to one of claims 1 to 7,
characterized in that
a sorption plant (10) for drying or drying and cooling air at least one corrosion-resistant plate heat exchanger (12, 12 ') with a spray nozzle bar (26) arranged on the inlet side of the sorption flow channels (16) or a saturated sorbent spray nozzle matrix (30) ( 32) and an inlet side of the cooling air flow channels (22) angeordent spray nozzle bar (38) for the cooling water (36), a drip tray (40) for the dripping, dilute sorbent (34) and a treatment circuit (52) for the sorbent (34) comprising a desorption device (46), a cooling device (48) and a pump (50). Apparatus according to claim 8, characterized in that the plate heat exchangers (12,12 ') of plastic films (28) are constructed, preferably with alternating, intersecting sorption and cooling air flow channels (16,22). Apparatus according to claim 8 or 9, characterized in that the Desorption (46) as an evaporator (54) and / or evacuator and the cooling device (48) are designed as ventilated air cooler, wherein between the desorption and the cooling device preferably one Brine / brine countercurrent heat exchanger (44) is arranged.

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