EP3462099B1

EP3462099B1 - Air conditioning device and method

Info

Publication number: EP3462099B1
Application number: EP17193632.1A
Authority: EP
Inventors: Ralf Carlsson
Original assignee: Enervent Zehnder Oy
Current assignee: Enervent Zehnder Oy
Priority date: 2017-09-28
Filing date: 2017-09-28
Publication date: 2021-07-28
Anticipated expiration: 2037-09-28
Also published as: EP3462099A1

Description

FIELD OF THE INVENTION

The invention relates to an air conditioning device as defined in the preamble of claim 1, and to an air conditioning method as defined in the preamble of claim 8.

BACKGROUND OF THE INVENTION

In hot and humid countries, such as the Mediterranean countries, the Arab countries and many of the Far East countries, it is necessary to cool the room spaces to achieve modern and comfortable housing conditions. A traditional way of providing air conditioning is to conduct fresh outdoor air into the indoor space at a temperature of, for example, approximately 30-35°C and a relative humidity of approximately 70-80%. The room space is then equipped with one or more coolers through which the room air is circulated, such that it cools down to a desired level. At the same time, moisture is removed from the air, and it is most often conducted into the outdoor air with the warm exhaust air of the cooler.
A major problem in modern technology is large electricity consumption. The absolute humidity of warm air drawn from outside is often of the order of 15 - 20 g/kg air, so cooling the air, and thereby water, requires energy. Another problem is caused by the humidity. When cooling the warm and humid supply air, its temperature decreases and its relative humidity rises. Although some of the water can be removed as condensation water, the relative humidity of the cooled air returned to the room space is very high. This often causes significant mould problems in buildings subject to hot climate conditions. In extremely difficult conditions, the lifetime of buildings will not even exceed ten years due to mould problems.
Prior art in the field of the invention has been disclosed in patent US6199388 , disclosing an air conditioning device for controlling humidity and temperature of supply air drawn from an outdoor space into an indoor space. It comprises a supply channel provided with a blower for conducting supply air from an outdoor space into an indoor space, and an exhaust channel provided with a second blower for conducting exhaust air from the indoor space into the outdoor space. Further, it comprises two rotating heat exchangers between the channels, and a cooler in the supply channel for lowering the temperature of the supplied supply air. However, the device does not function efficiently under all conditions, because moisture and heat are not always transferred in desired ways.
WO 2009/049673 A1 discloses an air conditioning device according to the preamble of claim 1.

OBJECT OF THE INVENTION

The object of the invention is to remedy the defects of the prior art described above. Specifically, the object of the invention is to disclose a new air conditioning device and a corresponding method, by means of which the energy consumption of air conditioning may be significantly reduced. Further, the object of the invention is to provide air-conditioned residential spaces where humidity is lower than currently, mould growth possibilities have been eliminated, and durability and lifetime of the buildings have been increased, even multiplied, compared to the current state.

SUMMARY OF THE INVENTION

The air conditioning device according to the invention is intended for controlling humidity and temperature of supply air drawn from an outdoor space into an indoor space. The air conditioning device comprises a supply channel provided with a first blower for conducting supply air from an outdoor space into an indoor space, and an exhaust channel provided with a second blower for conducting exhaust air from the indoor space into the outdoor space. Further, between the supply channel and the exhaust channel there is a rotating energy exchanger, and in the supply channel there is provided a cooler downstream of the energy exchanger for lowering the temperature of the supplied supply air below the dew point. According to the invention, the exhaust channel comprises, before the energy exchanger, an additional cooler for lowering the temperature of the exhaust air stream before the energy exchanger. Thus, it is an essential feature of the invention that the exhaust air is cooled before this energy exchanger.
In the air conditioning device according to the invention there are used rotating energy exchangers that are structures known per se. The energy exchanger generally has an aluminium disc-type rotating honeycomb structure, one half of which is arranged in the supply channel and the other half in the exhaust channel air stream. Thus, as the discs are constantly rotating, they alternately warm up in the warmer air stream and cool down in the cooler air stream, transferring heat between the supply channel and the exhaust channel air streams. It is also essential in the operation of the energy exchanger that it may also transfer moisture between the air channels, i.e. when cooling the hot and humid air below the dew point, the water condenses on the surface of the discs, and as the discs rotate the water is transferred into the drier and colder air stream.
Due to cooling of the exhaust air by means of the air conditioning device according to the invention, the absolute humidity of the supply air can be reduced at the energy exchanger to such extent that the benefits obtained are significantly greater than the energy needed for cooling the exhaust air. When the absolute humidity of the supply air is very low, its further cooling and/or warming to a desired final temperature does not require much energy.
According to one embodiment of the invention, the exhaust channel comprises, in the exhaust air flowing direction before the energy exchanger, a first air filter. By means of the first air filter, impurities entrained into the exhaust air may be filtered out from the exhaust air.
According to one embodiment of the invention, the supply channel comprises, in the supply air flowing direction before the energy exchanger, a second air filter. By means of the second air filter, impurities entrained in the supply air may be filtered out from the supply air.
The compact air conditioning device according to the invention dries the air efficiently, i.e. it significantly decreases the absolute humidity of the air flowing through it. This also gives the possibility of providing the air conditioning device with a water recovery arrangement for recovering the condensed water and conducting it for further use. The recovery arrangement is advantageously provided at least in connection with the coolers, from where the largest amounts of water are recovered. The recovered water may be used for watering plants, flushing the WC or showering, i.e. for all other purposes except cooking.
In the air conditioning device according to the invention, the blower in the supply channel and the blower in the exhaust channel and their operation are most suitably arranged such that the air stream of the supply channel is greater than the air stream of the exhaust channel. Thus, in the indoor space of the air-conditioned rooms there is always a positive pressure when the air conditioning device is operating. This ensures that outdoor air that is too warm or too humid is not able to flow into the air-conditioned space through the structures. Likewise, the arrangement ensures that the structures remain dry, prevents mould growth in the structures, and thus significantly increases the lifetime of the entire building.
The air conditioning method according to the invention is intended for controlling humidity and temperature of supply air drawn from an outdoor space into an indoor space. In the method, the heat and moisture of the supply air drawn from an outdoor space are transferred by a mechanical energy exchanger into the exhaust air, and the supply air after the energy exchanger is cooled below the dew point to separate moisture from the air stream. According to the invention, the exhaust air is cooled before the mechanical energy exchanger to provide more efficient cooling and drying of the supply air at the mechanical energy exchanger.
Preferably, in the method according to the invention, humidity of the supply air is measured, and on that basis it is decided how much the exhaust air is cooled before it is conducted to the energy exchanger.
The method according to the invention is most suited to be used in tropical or subtropical conditions where the temperature is above 25°C, preferably above 30°C, and the relative humidity is above 75%, even above 90%.
In one embodiment of the invention, the heat obtained from the employed cooling processes, i.e. cooling of the supply air and/or cooling of the exhaust air, for cooling the water is used for controlling the final temperature of the supply air.
The air conditioning device and the air conditioning method according to the invention provide considerable advantages over the prior art. The inventive air conditioning device and air conditioning method are based on the utilization of existing energy streams as efficiently as possible, and on the realization that warming or cooling the water in air requires a considerable amount of energy. Thus, in terms of the energy consumption of air conditioning, the key factor is the absolute humidity of the supply air being processed. The cooling and ventilating effect of the exhaust air employed in the invention is enhanced by separate cooling before the mechanical energy transfer, whereby the absolute humidity of the supply air can be significantly decreased. Further, raising the temperature of the supply air after a separate cooler to a suitable level to be blown into the room space is effected by means of the thermal energy obtained from the condensation heat of the water cooler.
Based on the performed tests and calculations, the device and method according to the invention decrease the consumption of electrical energy for air conditioning, heating and warm tap water in a normal-size house located in a hot climate by up to 80%. Thus, the savings easily exceed even 100kWh/day. In addition, it should be noted that significant savings are also achieved in the consumption of water, as each day approximately 200-3001 of water becomes available for free as an air conditioning by-product. The financial benefit obtained from the recovered water varies largely by country according to the price of water, but it may be even more than 50€/month.

LIST OF FIGURES

In the following, the invention will be described in detail with reference to the accompanying drawing, which schematically shows one air conditioning device according to the invention.

Fig. 1 is a schematic illustration of an air conditioning device according to the invention, and
Fig. 2 shows one embodiment of an air conditioning device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The air conditioning device of Fig. 1 has been arranged between an outdoor space 3 and an indoor space 4, i.e. for example in a residential building or a hotel, to transfer air from outside into the building and back outside. The air conditioning device comprises a supply channel 2, its inner end, i.e. the end in proximity to the indoor space 4, having a first blower 1 by means of which air is caused to flow from the outdoor space 3 into the indoor space 4, and an exhaust channel 6, its outer end, i.e. the end in proximity to the outdoor space 3, having a second blower 5 by means of which air flows from the indoor space into the outdoor space.
Between the supply channel 2 and the exhaust channel 6 there is a rotating energy exchanger 7, i.e. a structure where metal discs rotating around a shaft are alternately provided in the supply channel and in the exhaust channel, transferring heat and humidity from the hotter air stream into the colder one.
After the energy exchanger 7 in the supply channel 2 there is a cooler 9, the cooling circuit of which is connected with a cooling device outside the air conditioning device (not shown in the figure).
Fig. 2 shows an embodiment of the device comprising, in the supply air flowing direction after the cooler 9, a heater 10 arranged in the supply channel 2, and in connection with the cooler 9 a recovery arrangement 13 for condensed water.
According to one embodiment of the device, the water recovery arrangement is also connected to an additional cooler 11 which is arranged in the exhaust channel 6 before the energy exchanger 7.
According to one embodiment of the device, the water recovery arrangement is connected to the cooler 9 and the additional cooler 11.
In one embodiment of the device, the exhaust air channel 6 comprises, in the exhaust air flowing direction before the energy exchanger 7, a first air filter 8 that cleans the air exhausted from the room of possible impurities. This way, these impurities are not transferred back to the supply air through the energy exchanger 7.
In one embodiment of the device, the supply channel 2 comprises, in the supply air flowing direction before the energy exchanger 7, a second air filter 12 that cleans impurities entrained in the outdoor air before feeding the supply air into the room.
In one embodiment of the device, the supply channel 2 comprises, in the supply air flowing direction after the energy exchanger 7, a third air filter 14 for cleaning the supply air of impurities.
An air conditioning device according to one embodiment operates in the following way when the conditions are as follows. In the outdoor space 3 the temperature is 34°C, the relative humidity is 80% and the absolute humidity is 27.3g/kg. In the indoor space 4, respectively, the temperature is 21-24°C and the relative humidity is 45-55%.
When the device operates under these conditions, the in-flowing air first enters the energy exchanger 7 where the rotating metal discs pick up heat from the supply air, thereby cooling it. At the same time, humidity condenses on the disc surfaces. After the energy exchanger 7, the temperature of the supply air is 19.6°C and its relative humidity is approximately 75%. Next, the supply air is cooled at the cooler 9. At the cooler, the temperature of the supply air decreases to approximately 12°C, while its relative humidity is approximately 100%.
Next, the supply air enters the heater 10 arranged at the end of the supply channel 2, i.e. in a place where the absolute humidity is the lowest, i.e. where the amount of air to be heated is the lowest.
By following the removal of the exhaust air from the indoor space 4, it is first observed that the temperature of the exhaust air is initially 21-24°C and its relative humidity is 45-55%. First, the exhaust air is cooled in the additional cooler 11, such that its temperature decreases to approximately 17°C and its relative humidity rises to a value of approximately 80%.
When the exhaust air reaches the energy exchanger 7, its temperature is 17.2°C, i.e. the exhaust air cools the metal discs of the first energy exchanger to a temperature of 17.2°C. When the discs this cold move into the supply channel where the temperature of the air is 34°C, the supply air cools down to a significant degree, and a considerable portion of the humidity condenses on the metal discs. When the moist and warmed-up disc rotates back into the exhaust channel, it warms up and dries off therein, the exhaust air carrying the condensed moisture from the discs into the outdoor space 3.
The air conditioning device and the corresponding method according to the invention are based on the right and optimal control of energy transfer between different air streams, and on the basic premise that in air conditioning, it is not advantageous to warm up or evaporate water with expensive external energy any more than what is necessary. Thus, it is advantageous to keep the absolute humidity as low as possible, such that when the air stream is being warmed up, only or mainly air, instead of water, is being warmed. Further, by setting the value for absolute humidity of the supply air below the absolute humidity target value of the supply air, it is ensured that the supply air remains dry and has a drying effect on the structures.
The invention is not limited merely to the above-described examples, but many variations are possible within the scope of the claims.

Claims

An air conditioning device for controlling humidity and temperature of supply air drawn from an outdoor space into an indoor space, the air conditioning device comprising:
- a supply channel (2) having a first blower (1) for conducting supply air from an outdoor space (3) into an indoor space (4),

- an exhaust channel (6) having a second blower (5) for conducting exhaust air from the indoor space (4) into the outdoor space (3),

- a rotating energy exchanger (7) arranged between the supply channel and the exhaust channel,

- in the supply channel, a cooler (9) downstream of the energy exchanger for lowering the temperature of the supplied supply air below the dew point, characterized in that the exhaust channel comprises, before the energy exchanger, an additional cooler (11) for lowering the temperature of the exhaust air stream before the energy exchanger.
The air conditioning device according to claim 1, characterized in that the supply channel (2) comprises, after the cooler, a heater (10) for raising the temperature of the supply air to be conducted into the indoor space (4) to a desired level.
The air conditioning device according to claim 1 or 2, characterized in that the energy exchanger is formed by a rotating disc energy exchanger where discs that pick up and release heat and moisture are arranged to rotate between the supply channel and the exhaust channel.
The air conditioning device according to any one of claims 1 - 3, characterized in that the air conditioning device comprises a water recovery arrangement (13) for recovering condensed water and conducting it for further use.
The air conditioning device according to claim 4, characterized in that the water recovery arrangement (13) is connected at least to the cooler (9) and the additional cooler (11) for recovering the water condensed therein.
The air conditioning device according to any one of claims 1 - 5, characterized in that the exhaust channel (6) comprises, in the exhaust air flowing direction before the energy exchanger (7), a first air filter (8).
The air conditioning device according to any one of claims 1 - 6, characterized in that the supply channel (2) comprises, in the supply air flowing direction before the energy exchanger (7), a second air filter (12).
An air conditioning method for controlling humidity and temperature of supply air drawn from an outdoor space into an indoor space, in which method the heat and humidity of supply air drawn from an outdoor space (3) are transferred by a mechanical energy exchanger (7) into exhaust air, and after the energy exchanger (7) the supply air is cooled below the dew point to separate moisture from the supply air, characterized in that the exhaust air is cooled before the mechanical energy exchanger (7) to provide more efficient cooling and drying of the supply air at the energy exchanger.
The air conditioning method according to claim 8, characterized in that the humidity of the supply air is measured, and the exhaust air is cooled on the basis of the measurement.
The air conditioning method according to claim 8 or 9, characterized in that after cooling, the supply air is heated according to the target room temperature.
The air conditioning method according to any one of claims 8 - 10, characterized in that the method is applied in tropical or subtropical conditions where the temperature is above 25°C, preferably above 30°C, and the relative humidity is above 75%, even above 90%.
The air conditioning method according to claim 11, characterizedin that the heat obtained from cooling of the supply air and/or cooling of the exhaust air is used for controlling the final temperature of the supply air.