WO2010031592A1

WO2010031592A1 - Method for operating a sorption air conditioning system with enthalpy heat exchanger for the cyclic humidification and dehumidification of indoor air

Info

Publication number: WO2010031592A1
Application number: PCT/EP2009/006926
Authority: WO
Inventors: Donald Herbst
Original assignee: Donald Herbst
Priority date: 2008-09-16
Filing date: 2009-09-16
Publication date: 2010-03-25
Also published as: DE102008048238B4; DE102008048238A1; CN102165267A

Abstract

The invention relates to a method for operating an air conditioning system, using at least one enthalpy exchanger (1), wherein the heat exchange surface is brought into contact with a fluid used to cool or heat air (3), with air to be dehumidified or humidified and with a hygroscopic sorption solution. The fluid and the sorption solution are conducted cocurrently and the fluid and the air are conducted counter-currently through the enthalpy exchanger. The air conditioning system is used depending on the temperature and/or the humidity of the air both in the dehumidification operation and in the humidification operation. The sorption solution is conducted from a storage unit (11) in circulation mode into the enthalpy exchanger and is fed back from the enthalpy exchanger into the storage unit. The increase of the water content of the sorption solution during the dehumidification operation is reversed during the humidification operation.

Description

METHOD FOR OPERATING A SORPTION AIR CONDITIONER WITH

ENTHALPY HEAT EXCHANGERS FOR CYCLIC HUMIDIFICATION AND DEHUMIDIFICATION OF ROOM AIR

The invention relates to a method for operating an air conditioning system using at least one enthalpy exchanger.

From US Pat. No. 6,745,826 B2, a heat exchanger is known comprising plates arranged parallel to one another and forming a multiplicity of tube-like parallel passages. Water flows through these passages. Air flows through the gap between the plates transversely to the water flow direction. In addition, a liquid desiccant flows down the gap forming surfaces of the plates from top to bottom to dehumidify the air. After leaving the nip, the liquid desiccant (sorbent solution) is collected and regenerated for a new use. During this regeneration, the water taken up from the air must be expelled again. This can be done by means of an additional, heat-requiring heat exchanger. The heat can be, for example be supplied by a boiler or solar absorber. This requires either heating energy or high investment costs, a lot of space and considerable maintenance costs.

DE 199 52 639 A1 discloses a process for air conditioning by sorption and desorption of water by means of a recirculated hygroscopic sorption solution which comprises the steps of: a) drying an air stream to be conditioned by sorption of water contained therein and b) Regeneration of the sorbent solution which is low in concentration due to the sorption of water by desorption of water using low-temperature heat and ambient air.

It is therefore an object of the present invention, a method for operating an air conditioner using at least one enthalpy or heat exchanger, wherein the heat exchange surface on one side with a serving for cooling or heating of air fluid and on the other side with dehumidifying or humidifying air as well as being contacted with a hygroscopic sorption solution such that the fluid and the sorbent solution are passed in cocurrent and the fluid and the air are passed countercurrently through the enthalpy exchanger, indicating that the regeneration of the sorbent solution does not occur requires additional energy and works largely maintenance-free.

This object is achieved by a method having the features of claim 1. Advantageous developments of this method will become apparent from the dependent claims. The fact that the air conditioning is used depending on the temperature and / or humidity of the air in both the dehumidifying and humidifying operation and that the sorbent in recirculation mode from a memory in the Enthalpietau- shear out and from the Enthalpietauscher in the memory is returned, wherein the dehumidifying operation increase in the water content of the sorbent solution is reversed in humidification, and due to a setting in memory concentration gradient of the sorbent in the dehumidifying operation sorption from a higher concentration region of the memory in the Enthalpietauscher out of this and in recycled a lower concentration region of the memory and in humidifying operation sorption from a region having a lower concentration of the memory in the enthalpy and out This is returned to a higher-concentration region of the memory, it is achieved that both the dehumidifying operation and the humidifying operation are carried out in the desired manner, wherein a total of considerable energy savings takes place. This advantage results from the fact that the manner usual in dehumidifying operation with cooling of the air by the fluid and the humidifying operation are usually coupled with a heating of the air by the fluid.

Due to a natural concentration gradient, the concentration of the sorption solution in the storage increases from top to bottom, and in the dehumidifying operation sorption solution from the lower part of the storage in the Entthalpietauscher out and returned from this in the upper part of the memory, and in humidifying sorption solution is led from the upper part of the memory in the Enthalpiespeicher and returned from this in the lower part of the memory.

It is desirable that the concentration reduction of the sorption solution in the dehumidifying operation is as high as possible when passing through the enthalpy exchanger. This ensures that the cycle of water uptake and water delivery through the sorbent solution can last over a full year, without the need for an excessively large supply.

Advantageously, the concentration reduction of the sorption solution should be at least 15% in the cooling operation between the removal from the store and the return to the store.

The invention will be explained in more detail below with reference to an embodiment shown in FIGS. Show it:

Fig. 1 shows an air conditioner in the dehumidifying or cooling operation and

2 shows the air conditioning system according to FIG. 1 in the humidification or heating operation.

The reproduced in the figures air conditioning contains two constructed in the same way Enthalpietauscher 1 and 2, wherein the Enthalpietauscher 1 for cooling and dehumidification or for heating and humidifying supply air 3 and the Enthalpietauscher 2 for heating or cooling of a fluid used in the enthalpy exchanger 1 for cooling or heating the supply air through the exhaust air 4 of the cooled or heated by Enthalpietauscher 1 space. As a suitable fluid, water is preferably used.

The enthalpy exchangers 1 and 2, for example, each contain an unillustrated capillary tube from one or more capillary tube mats, which consist of preferably parallel to each other and vertically arranged capillary tubes. These are flexible plastic tubes with an outer diameter between 0.5 and 5 mm. The capillary tube each have a common flow line 5 and 6 for the supply of fluid to the respective Enthalpietauscher 1 and 2 and a common return line 7 and 8 for the removal of the fluid from the respective Enthalpietauscher 1 and 2. The feed line 5 of the Enthalpietauschers. 1 and the return line 8 of the enthalpy exchanger 2, on the one hand, and the feed line 6 of the enthalpy exchanger 2 and the return line 7 of the enthalpy exchanger 1, on the other hand, are interconnected so that the fluid in the circuit flows successively through the capillary tube registers of the two enthalpy exchangers 1 and 2. A pump 9 ensures the constant circulation of the fluid. The supply and return lines are arranged so that the fluid flows in the enthalpy exchangers 1 and 2 from top to bottom, while the supply or exhaust air flows in countercurrent thereto from bottom to top.

When cooling the supply air, its dehumidification is preferably also sought, while, conversely, when the supply air is heated, it is additionally intended to humidify it. For this purpose, the heat exchanger 1 via an inlet 10 is a hygroscopic Sorptionlösung supplied, which is located in a container 11. The capillary tubes are wetted at their upper end with this sorption solution, and this flows along the capillary down to an outlet 12, via which it is returned to the container 11. A metering pump 13 keeps the sorption solution in constant circulation.

In order to achieve a high dehumidifying or moistening effect, it is necessary for the capillary tubes to be wetted uniformly over their entire length with the sorption solution. This can, even if to increase the efficiency of the Enthalpietauschers the supplied amount of the sorbent solution is minimized, be achieved in that the capillary tubes have a hydrophilic or water-spreading surface with a contact angle of less than 20 °. For this purpose, the capillary tubes are preferably coated with a nonwoven fabric.

The hygroscopic sorbent solution is suitably an aqueous LiCl solution having a concentration in the range of about 15% to 40%. Another suitable sorption solution is a CaCl ₂ solution or a mixture of these two solutions. Due to the specific weight and also the control of the inflow direction, a concentration gradient arises in the container 11 in such a way that a lower region 14 with a higher concentrated (rich) sorption solution and an upper region 15 with a weaker concentrated (poor) sorption solution are formed , Within these ranges, of course, there is also the concentration gradient from top to bottom. In the cooling operation illustrated in FIG. 1, in which the supply air 3 in the enthalpy exchanger 1 is simultaneously dehumidified, the inlet 10 is connected to a passage 16 near the bottom of the container 11, so that the rich sorption solution is supplied to the capillary tubes. As it flows down the capillary tubes, the sorbent solution absorbs moisture from the supply air, increasing its water content and thus reducing its concentration. The thus obtained poor sorption solution is then returned to the container 11 via the outlet 12 and a float 17 located in the container 11 on the surface of the sorption solution. In this way, in the cooling operation, the volume of the sorption solution in the container 11 is increased.

In the illustrated air conditioning, an extremely high heat recovery takes place, which eliminates an additional heating or cooling of the supply air by a respective Enthalpietauscher for the supply air and the exhaust air is used.

In cooling or summer operation, the supply air 3 is cooled in the first Enthalpietauscher 1 and dehumidified. The fluid (cooling water) flows in the circuit through both Enthalpietauscher 1 and 2. It is heated in the register of the first Enthalpietauschers 1 in the cooling and dehumidification of the supply air 3. In the register of the second enthalpy exchanger 2, the fluid is again cooled by the exhaust air 4 after it has been adiabatically cooled to its dew point temperature in an upstream humidifier. The exhaust air 4 is thereby heated and humidified and then led out of the building. In the heating or winter operation shown in FIG. 2, the supply air 3 is heated and humidified in the first enthalpy exchanger 1. The fluid is now cooled in the enthalpy exchanger 1 and via the return line 7 and the feed line 6 into the second

Enthalpietauscher 2 passed, in which it is heated by the exhaust air 4 before it is passed through the return line 8 and the feed line 5 back to Enthalpietauscher 1.

In heating operation, the float 17 and the inlet 10 on the one hand and the passage 16 and the outlet 12 on the other hand are connected to one another by appropriate valve control. Thus, the poor sorbent solution from the container 11 is used for wetting the capillary tubes, and it is deprived of water when passing through the enthalpy exchanger 1 due to the humidification of the supply air 3, so that it as a rich sorption on the outlet 12 and the passage 16 the area 14 is supplied in the container 11. In this case, there is a reduction in the volume of the sorption solution corresponding to the amount of moisture released to the supply air 3.

In heating mode, the silt solution diluted by the cooling operation can thus be regenerated. By controlling the amount of sorption solution fed to the enthalpy exchanger 1 via the metering pump 13, it can be determined how much the supply air 3 humidifies and thus the sorption solution is concentrated. The tolerance for the adjustment of the room humidity in the winter is relatively high, so that a large margin exists. In this way, an increase in concentration, which compensates for a previous reduction in concentration in the cooling operation, can be set very precisely. The container 11 must store the initial sorption solution and, in addition to regeneration, the entire amount of water that was taken up by the sorption solution during the cooling operation from the supply air 3. In an air-conditioning system with, for example, 10,000 m ³ / h of supply air, which can be used to air-condition an office of around 2,000 m ^{2 of} usable floor space, Central European climates generate around 14,500 liters of water per year in the summer.

With the highest possible concentration of the rich sorption solution and the lowest possible concentration of the poor sorption solution, the storage volume of the container 11 can be minimized. Thus, for the example above, with a sorbent solution of LiCl at a rich solution of 40% and a poor solution of 20, 30 or 35%, respectively a storage volume of 29, 58 or 116 m ^{3 is} needed. It is therefore expedient for reducing the storage capacity to make the concentration difference between rich and poor sorption solution as large as possible, advantageously greater than 15%.

The concentration difference can be controlled by the flow rate of the sorption solution in the enthalpy exchanger 1. The lower the flow rate, the higher the concentration difference. However, for a uniform wetting of the capillary tubes, a minimum flow rate is required, so that the desired concentration difference is often not achieved in one pass through the enthalpy exchanger 1. However, it is then possible to return the sorption solution leaving through the outlet 12 directly via the inlet 10 into the enthalpy exchanger 1, so that the sorption solution more than once the enthalpy exchanger 1 passes through until it has reached the desired concentration difference and is passed into the container 11.

In the case of heating, the adiabatic cooling of the exhaust air is turned off in an air washer before it enters the enthalpy exchanger 2. By contrast, it is possible to continue the sprinkling of the capillary tube register of the enthalpy exchanger 2 with water, because the degree of efficiency is thereby increased. In addition, a large part of the enthalpy exchanger is moistened anyway at lower outside temperatures by the condensate water emerging from it when the exhaust air cools down.

The overall efficiency of the air conditioner can be significantly increased if the capillary tube of the enthalpy exchanger 2 is also sprinkled with sorption solution during heating or winter operation. For this purpose, an inlet 18 and an outlet 19 are provided accordingly. The sorption solution can also be removed from the container 11 for this purpose and returned to it. By wetting the surface of the capillary tubes with the sorbent solution, the dew point of the air is raised so that the heat of condensation resulting from the contact between the moist exhaust air and the surface of the capillary tubes becomes effective at higher temperatures. Thus, in a capillary tube coil sprinkled with a LiCl sorption solution, condensation heat can already be released at an air temperature of 20 ^° C. In a non-sprinklered register, however, this is done assuming an air temperature of 22 ⁰ C and 50% relative humidity until a drop below the dew point of about 11 ⁰ C. Measures against the formation of ice on the capillary tubes in the enthalpy exchanger 2 can also be dispensed with since the irrigation of the capillary tube register with sorption solution can greatly reduce the temperature for ice formation.

Finally, the sorption solution can also be used as antifreeze for the fluid flowing through the capillary tubes of the two enthalpy exchangers 1 and 2. In heating operation, the temperature of the fluid in the return line 7 is lowered almost to the outside air temperature. The fluid must therefore be mixed with antifreeze, which usually consists of a glycerol solution. However, this significantly increases the viscosity of the fluid, so that the power to be permanently provided by the pump 10 can increase to four times. In addition, such antifreeze deteriorates the heat transfer, and the specific heat capacity of the fluid is reduced, so that the flow rate of the fluid must be increased.

These disadvantages are significantly reduced when the sorption solution is used as antifreeze. This can be fed by means of a simple valve circuit and suitable connection lines from the container 11 in the capillary tube, wherein the concentration of each prevailing outside temperature can be adjusted in such a way that it is as high as necessary, but as low as possible.

Claims

claims

Method for operating an air conditioning system using at least one enthalpy exchanger (1), in which the heat exchange surface on one side is provided with a fluid for cooling or heating air (3) and on the other side with air to be dehumidified or humidified (3 ) and a hygroscopic sorption solution, such that the fluid and the sorption solution are cocurrent and the fluid and air (3) are countercurrent through the enthalpy exchanger

(1), that the air conditioning system is operated in dehumidification mode as well as in the dehumidification mode depending on the temperature and / or humidity of the air (3)

Humidification operation is used and that the sorption solution is circulated from a memory (11) in the Enthalpietauscher (1) and returned from the Enthalpietauscher (1) in the memory (11), wherein the dehumidifying occurred in the increase in the water content of the sorption in humidifying and, on the basis of a concentration gradient of the sorption solution in the dehumidifying operation which is set in the tank (11), sorption solution is passed from a region of the tank (11) having a higher concentration into the enthalpy exchanger (1) and from this into a lower concentration having area of

Accumulator (11) and in the humidifier Operation sorption from a region having a lower concentration of the memory (11) in the Enthalpietauscher (1) and out of this into a higher concentration tion having area of the memory

(11) is returned.

2. The method according to claim 1, characterized in that the concentration of the sorbent solution in the memory (11) increases from top to bottom and in dehumidifying operation sorption from the lower part (14) of the memory (11) in the Enthalpietauscher (1) and out this in the upper part (15) of the memory (11) and led back in humidifying sorption from the upper part (15) of the memory (11) in the Enthalpietauscher (1) and out of this in the lower part (14 ) of the memory (11) is returned.

3. The method according to claim 1 or 2, characterized in that the concentration reduction of the sorption solution in the dehumidifying operation in a passage through the Enthalpietauscher (1) is as high as possible.

4. The method according to claim 1 or 2, characterized in that the sorption solution before returning to the memory (11) repeatedly passes through the Enthalpietauscher (1).

5. The method according to any one of claims 1 to 4, character- ized in that the concentration reduction of the sorption solution over the amount of per unit time to the Enthalpietauscher (1) guided sorption solution is controlled.

6. The method according to any one of claims 3 to 5, characterized in that the concentration reduction of the sorption solution in the cooling operation between the removal from the memory (11) and the return to the memory (11) at least

15%.

7. The method according to any one of claims 1 to 6, characterized in that an aqueous LiCl solution is used as the sorbent solution.

8. The method according to claim 7, characterized in that the concentration of LiCl solution in the memory (11) is in the range between 15% and 40%.

9. The method according to any one of claims 1 to 8, character- ized in that the sorption solution is added to the fluid as antifreeze.

10. The method according to any one of claims 1 to 9, characterized in that at least two Enthalpietauscher (1, 2) are used, which are flowed through by the fluid in a closed circuit in succession, wherein in the dehumidifying operation, the first Enthalpietauscher (1) for cooling and Dehumidification of supply air (3) and the second Enthalpietauscher (2) for cooling the fluid by exhaust air (4) and in humidifying the first Enthalpietauscher (1) for heating and humidifying supply air (3) and the second Enthalpietauscher (2) Heating of the fluid by exhaust air (4) can be used.

11. The method according to claim 10, characterized in that the heat exchange surface of the second Enthalpietauschers (2) is also wetted with sorbent solution.

12. The method according to claim 10 or 11, characterized in that the concentration gradient of the sorption solution in the second Enthalpietauscher (2) is reverse to that in the first Enthalpietauscher (1).

13. The method according to any one of claims 1 to 12, characterized in that the exhaust air (4) is cooled adiabatically before entering the second Enthalpietauscher (2).