Dehumidifier apparatus, cooling systems and methods of operation thereof

Abstract

The invention relates to a dehumidifier apparatus, comprising a dehumidifier housing (22), a liquid circulation system (39) and a vacuum pump (34) disposed between the dehumidifier housing (22) and the liquid circulation system (39). The interior of the dehumidifier housing (22) is separated into an air chamber (24) and a vacuum chamber (26) by a water vapour permeable membrane (28), the air chamber (24) having an air inlet (30) to receive humid air, and an air outlet (32) through which dehumidified air, in use, exits. A vacuum pump inlet (35) of the vacuum pump (34) is in fluid communication with the vacuum chamber (26), and a fluid conduit (36) extends between a vacuum pump outlet (41) of the vacuum pump (34) and a vacuum mixing condenser (40) of the liquid circulation system (39). In use, fluid containing moisture exits the fluid conduit (36) below the surface of circulation liquid (42) within the vacuum mixing condenser (40), whereby the moisture is condensed and mixed in the circulation liquid (42). The liquid circulation system (39) comprises a liquid circulation arrangement configured for receiving circulation liquid from the vacuum mixing condenser (40) and for returning cooled circulation liquid to the vacuum mixing condenser (40). A cooling system using the dehumidifier apparatus is also disclosed, as are methods of operating the dehumidifier apparatus and the cooling system.

Description

[0001] Dehumidifier Apparatus, Cooling Systems and Methods of Operation Thereof

[0002] Technical Field

[0003] The invention relates to air conditioning systems, and more particularly to a dehumidifier apparatus, a cooling system, and methods of operation thereof.

[0004] Background

[0005] The global air conditioning systems market size was about US$119.36 billion in 2022. Humidity is one of the most significant factors in air conditioning to guarantee indoor environment quality. Air humidity needs to be well controlled to prevent excessive body perspiration buildup caused by moisture saturation in the air, and droplets forming on cold-water pipes, furniture and doors. Such moisture may increase mold growth, dust mite populations, and other damp conditions which is undesirable. According to the standards provided by the American Society of Heating, Refrigerating and Air- Conditioning Engineers (ASHRAE), occupied spaces should have a relative humidity of between 30% to 60%. In the UK, the average relative humidity is about 80%, 75%, 85%, and 87% in spring, summer, autumn, and winter, respectively. Accordingly, there is a large need for dehumidification, and the UK residential dehumidifier market alone is expected to reach US$ 85.28 million in 2026.

[0006] Air dehumidifiers can also contribute to cooling. The global markets for industrial cooling, district cooling, and data centre cooling were valued at US$20.98 billion, US$28.19 billion, and US$18.65 billion respectively in 2023. Evaporative cooling is one of the most cost-effective cooling technologies, and the global market for evaporative cooling is set for substantial growth, with a projected value of US$6.5 billion by the end of 2024. However, evaporative cooling technologies are subject to ambient conditions and perform poorly in countries with a humid air climate due to a less significant evaporative cooling effect. Air dehumidification may overcome this problem and unlock the potential of evaporative cooling technologies in the home, business and industry applications.

[0007] Most air dehumidification systems are based on a moisture-condensing process during which the air is cooled down to its dew point. The condensing-based air dehumidification is typically not energy-efficient due to air overcooling and reheating. Membrane-based air dehumidification systems are a relatively recent development which are an alternative way to provide dehumidification. Such membrane-based air dehumidification systems are driven by a chemical potential difference of moisture between the two sides of the membrane, and no heat input is required to the membrane.

[0008] It is known to provide a membrane-based air dehumidifier, which has a high permeation of water molecules through the membrane and a limited permeation for oxygen and nitrogen molecules. The most common arrangement uses a vacuum pump to create a partial moisture pressure difference between a feed side and a permeate side of the membrane, facilitating moisture removal from the humid air through the membrane. The low-pressure moisture and air on the permeate side is compressed from l-2kPa to about lOlkPa (i.e. one atmosphere) to condense the permeate and extract water thereby reducing humidity. Such an arrangement has the problem that the vacuum pump has a very high power consumption to create the large pressure ratio. In practice, not only moisture but also some air pass through the membrane, which is disadvantageous and unavoidable. The water vapour fraction in the permeate fluid is about 90% to 99%, depending on the selectivity of the membrane, and the air within the permeated fluid result in even higher power consumption for the vacuum pump.

[0009] It is also known to provide an arrangement using two membranes to reduce the energy consumption of the vacuum pump. Such an arrangement may have a much lower outlet pressure, for example 3.5kPa. A vacuum compressor is used to increase a pressure of the moist air to a pressure that is higher than the partial pressure for the moisture to remain in the air, so that the moisture can permeate through the second membrane. After the second membrane the air and vapour mixture returns back to ambient. Since the outlet pressure is relatively low, i.e. 3.5kPa, the vacuum compressor has a relatively low power input. However, this arrangement still faces the challenge of air removal, because air passes through both membranes. The arrangement may require two vacuum pumps connected to the two vacuum chambers to transfer the permeating air back to the ambient and maintain sub-atmospheric pressure at the inlet and outlet of the compressors. Further, both vacuum pumps transfer both air and moisture, and given the air permeance rate, the mass flow rate of the mixture increases with a decreased partial pressure of the air. Consequently, the two vacuum pumps may still contribute to a large power consumption and unsteady operation.

[0010] It is also known to provide an arrangement based on vacuum condensation. With such an arrangement water vapor on the feed side of the membrane passes through the membrane due to a partial vacuum on the permeate side. The moist permeate is then compressed using a vacuum compressor to a saturation pressure. The low-pressure water vapor extracted from the air is subsequently condensed and exhausted to the ambient conditions using a water pump.

[0011] Another prior art dehumidifier apparatus is known from US 2019 / 0176084 (The Texas A&M University System) as shown in Figure 1, generally designated 10. This arrangement uses a vacuum pump 12 to extract the air in the permeate side of the membrane, which is a cumbersome arrangement. A second vacuum pump 14 then compresses moist permeate, which is subsequently condensed in a heat exchanger 16. With such an arrangement the moist permeate is compressed by the second vacuum pump 14 from a partial vacuum pressure of about 2kPa (shown at 18) to about lOlkPa (shown at 19), which potentially leads to a large power consumption. In the moisture extraction process shown in Figure 1, the moisture is also compressed with the air, which may result in re-evaporation of water in the system, which is inefficient. Overall the arrangement shown in Figure 1 may not handle the fluids in an efficient manner, which may lead to an excessive power consumption due to the requirements for two vacuum pumps.

[0012] It is broadly an object of the present invention to address one or more of the above mentioned disadvantages of the previously known dehumidifier apparatus.

[0013] Summary

[0014] What is required is a dehumidifier apparatus which may reduce or minimise at least some of the above-mentioned problems. According to a first aspect of the invention, there is provided a dehumidifier apparatus, comprising a dehumidifier housing, a liquid circulation system, and a vacuum pump disposed between the dehumidifier housing and the liquid circulation system, wherein an interior of the dehumidifier housing is separated into an air chamber and a vacuum chamber by a water vapour permeable membrane, the air chamber having an air inlet to receive humid air, and an air outlet to output dehumidified air, wherein a vacuum pump inlet of the vacuum pump is in fluid communication with the vacuum chamber, wherein a fluid conduit extends between a vacuum pump outlet of the vacuum pump and a vacuum mixing condenser of the liquid circulation system, wherein fluid containing moisture is arranged to exit the fluid conduit below a surface of circulation liquid within the vacuum mixing condenser, and wherein the liquid circulation system comprises a liquid circulation arrangement configured for receiving circulation liquid from the vacuum mixing condenser in which the fluid that is output from the fluid conduit is mixed and / or condensed, and for returning cooled circulation liquid to the vacuum mixing condenser.

[0015] Such an apparatus provides the advantage that air can be suitably dehumidified, while reducing or minimising the energy consumed by the system, and avoiding the drawbacks of dew-point based dehumidification systems.

[0016] Preferably the liquid circulation arrangement comprises a multiphase pump disposed, in direction of flow in the liquid circulation system, between the liquid outlet of the vacuum mixing condenser and the liquid inlet thereof. A benefit is that the multiphase pump recirculates the circulation liquid so as to return in cooled form, for use in the mixing / condensation of the fluid (permeate). Another benefit is that the multiphase pump compresses and continuously removes the permeating air.

[0017] Preferably the multiphase pump is disposed at a lower elevation than the vacuum mixing condenser. An advantage is that, through the conveyance of the circulation liquid at least partially under gravity, energy consumption by the multiphase pump is reduced; thus, utilising such a height difference permits energy to be “recovered” from the pressurised water circulation system.

[0018] In embodiments the multiphase pump is disposed at a lower elevation than the vacuum mixing condenser by a first distance, wherein the first distance (i) lies in the range 0.1 to 10m, (ii) lies in the range 9 to 10m or (iii) is 10m. A height difference of about 10 meters may reduce the energy usage by 10% (i.e. reducing a typical power consumption of lOOWatts to be reduced by lOWatts).

[0019] Preferably, the liquid circulation arrangement comprises a cooler disposed, in the direction of flow in the liquid circulation system, between the liquid outlet of the vacuum mixing condenser and the liquid inlet thereof. A benefit is that the circulation liquid is returned in cooled form, so as to enhance the mixing / condensation of the fluid (permeate).

[0020] Preferably, the liquid circulation arrangement comprises, in sequence in the direction of flow in the liquid circulation system between the liquid outlet of the vacuum mixing condenser and the liquid inlet thereof, the multiphase pump and the cooler. Advantageously, the two devices in sequence recirculate the circulation liquid so as to return in cooled form, for use in the mixing / condensation of the fluid (permeate).

[0021] Preferably, the cooler is disposed at a lower elevation than the vacuum mixing condenser. Again, utilising such a height difference permits energy to be “recovered” from the pressurised liquid circulation system. Preferably, the cooler is disposed at a lower elevation than the vacuum mixing condenser by a second distance, wherein the first distance is substantially equal to or less than the second distance. This configuration assists in reduction of energy consumption. In embodiments, the second distance (i) lies in the range 0.1 to 10.3m or (ii) lies in the range 9 to 10.3m.

[0022] Preferably, the fluid conduit extends such that an end thereof opposite the vacuum pump outlet extends by a predetermined distance into the interior of the vacuum mixing condenser. This can ensure that the fluid (permeate) contacts the circulation liquid at a distance from the exterior of the vacuum mixing condenser, and / or where the circulation liquid is at its coolest, improving the efficiency of condensation. The fluid conduit may comprise an elongate pipe.

[0023] In an embodiment the fluid conduit is coupled for fluid communication with the vacuum mixing condenser at a point below the liquid inlet thereof. This can ensure that the fluid (permeate) contacts the circulation liquid where the circulation liquid is at its coolest, improving the efficiency of condensation. Preferably, the liquid outlet is disposed at a higher elevation on the vacuum mixing condenser than the liquid inlet thereof. Advantageously, this ensures that the warmest circulation liquid is removed from the vacuum mixing condenser at a given time, for cooling, thereby improving efficiency. Another advantage is a more efficient removal of non-condensable air from the condenser because air has a lower density.

[0024] In an embodiment, a first liquid circulation conduit extends between the liquid outlet and the multiphase pump, the first liquid circulation conduit or a substantial part thereof preferably extending vertically or substantially vertically. Beneficially, this assists with gravity feed of circulation liquid to the multiphase pump.

[0025] In an embodiment, a second liquid circulation conduit extends between the multiphase pump and the cooler, the second liquid circulation conduit preferably extending horizontally or substantially horizontally. This affords a configuration where the cooler is installed at an appropriate height.

[0026] In an embodiment, a third liquid circulation conduit extends between the cooler and the liquid inlet of the vacuum mixing condenser, whereby circulation liquid in the cooler is transferable to the vacuum mixing condenser for mixing with circulation liquid therein. In embodiments, the third liquid circulation conduit comprises (i) a first part, preferably extending vertically or substantially vertically, (ii) a second part, preferably extending horizontally or substantially horizontally and / or (iii) a third part, preferably extending vertically or substantially vertically. This affords a configuration where the cooler is installed at an appropriate height in relation to the vacuum mixing condenser and the multiphase pump, so as to reduce or minimise energy consumption required for the multiphase pump.

[0027] Preferably the vacuum pump comprises a vacuum compressor configured to receive as the fluid a permeate from the vacuum chamber and to compress the permeate to a pressure lying within the range 3 to lOkPa, and preferably 5 kPa. Power consumption for dehumidifier apparatus is thereby reduced by employing the vacuum mixing condenser to greatly decrease an outlet pressure required for the vacuum compressor.

[0028] In embodiments, the cooler (i) comprises a cooling tower, (ii) has a vertical length dimension of up to 10.3m, (iii) has an upper vent for venting air received from the multiphase pump to atmosphere via the vacuum mixing condenser and / or (iv) has a lower drain or overflow whereby any excess circulation liquid received by the cooler is removable.

[0029] Preferably, the dehumidifier apparatus includes a controller coupled to the vacuum pump, the controller being configured to supply a first drive signal to the vacuum pump to cause fluid received at the vacuum pump inlet from the vacuum chamber to be compressed and output via the outlet port. The amount of pumping out of fluid from the vacuum chamber can be suitably controlled, e.g. to optimise pressure within the vacuum chamber and / or enhance efficiency of operation of the vacuum mixing condenser.

[0030] Preferably, the controller is further coupled to the multiphase pump, the controller being configured to supply a second drive signal to the multiphase pump to cause circulation liquid received from the circulation liquid outlet of the vacuum mixing condenser to be compressed and output in the direction of flow in the circulation system. The amount of pumping of the circulation liquid can be suitably controlled, e.g. to optimise or enhance efficiency of operation of the cooler and / or vacuum mixing condenser.

[0031] In an embodiment, the vacuum pump inlet of the vacuum pump is in fluid communication with the vacuum chamber via an outlet port of the dehumidifier housing.

[0032] In embodiments the circulation liquid comprises (i) water, or (ii) water and a predetermined proportion of biocidal additive or anti-bacterial additive.

[0033] Preferably, water is used as the circulation liquid. The advantages of using water as the cooling medium (circulation liquid) include low cost, low viscosity, environmentally friendliness, and high specific heat capacity (which will lead to a lower flow rate and pump power consumption). Unlike water used in a dew-point type coolers of the prior art, the cooling water in this embodiment is for moisture condensation. In embodiments, the dehumidified air flows over the dry membrane and is not in contact with the bacteria if present in the circulation system, thereby not affecting the quality of the supply air.

[0034] In other embodiments, other fluids may be used to cool down / condense the moisture in the fluid exiting the vacuum chamber, including thermal oil, aliphatic hydrocarbons fluids and / or a desiccant liquid. However, once the moisture is condensed, it will need to be separated from the cooling medium (or regeneration) using a separator, which can be energy consuming. Otherwise, the cooling medium cannot work effectively in the long term.

[0035] In another aspect, there is provided a cooling system comprising: a dehumidifier apparatus according to any of claims 1 to 25 of the appended claims; an air driving device; wherein a controller is configured to supply a third drive signal to the air driving device to drive ambient air between the air inlet and the air outlet, from which dehumidified and / or cooled air is expelled. Air may thus be forced through the air chamber in a controlled manner, where necessary to control the rate of moisture extraction from the air via the membrane. In embodiments, the air driving device comprises an air compression pump disposed at the air inlet and / or an air extraction pump disposed at the air outlet.

[0036] In another aspect, there is provided a method of operating a dehumidifier apparatus, the method including: providing a dehumidifier apparatus according to any of claims 1 - 27 of the appended claims; providing a controller, coupled to the vacuum pump, the method comprising supplying, by the controller a first drive signal to the vacuum pump to cause fluid received at the vacuum pump inlet from the vacuum chamber to be compressed and output via the outlet port.

[0037] The method preferably further comprises supplying, by the controller, a second drive signal to the multiphase pump to cause circulation liquid and vapour received from the liquid outlet of the vacuum mixing condenser to be compressed and output in the direction of flow in the liquid circulation system. In another aspect, there is provided a method of operating a cooling system, the method including: providing a cooling system according to any of claims 26 - 27 of the appended claims; and supplying, by the controller, a third drive signal to the air driving device to drive the ambient air between the air inlet and the air outlet, from which dehumidified and / or cooled air is expelled.

[0038] According to an alternative characterisation of the invention there is provided a dehumidifier apparatus, comprising a dehumidifier housing, a liquid circulation system, and a vacuum pump disposed between the dehumidifier housing and the liquid circulation system, wherein an interior of the dehumidifier housing is separated into an air chamber and a vacuum chamber by a water vapour permeable membrane, the air chamber having an air inlet to receive humid air, and an air outlet to output dehumidified air, wherein a vacuum pump inlet of the vacuum pump is in fluid communication with the vacuum chamber, wherein a fluid conduit extends between a vacuum pump outlet of the vacuum pump and a vacuum mixing condenser of the liquid circulation system, wherein fluid containing moisture is arranged to exit the fluid conduit into circulation liquid within the vacuum mixing condenser, wherein the fluid output from the fluid conduit is mixed and / or condensed in the circulation liquid.

[0039] According to another alternative characterisation of the invention there is provided a dehumidifier apparatus, comprising a dehumidifier housing, a vacuum mixing condenser for holding cooling fluid, and a vacuum pump disposed between the dehumidifier housing and the vacuum mixing condenser, wherein an interior of the dehumidifier housing is separated into an air chamber and a vacuum chamber by a water vapour permeable membrane, the air chamber having an air inlet to receive humid air, and an air outlet to output dehumidified air, wherein a vacuum pump inlet of the vacuum pump is in fluid communication with the vacuum chamber, wherein a fluid conduit extends between a vacuum pump outlet of the vacuum pump and the vacuum mixing condenser, wherein fluid containing moisture is arranged to exit the fluid conduit below a surface of the cooling fluid of the vacuum mixing condenser such that the fluid output from the fluid conduit is mixed and / or condensed by the cooling fluid.

[0040] Any preferred or optional features of one aspect or characterisation of the invention may be a preferred or optional feature of other aspects or characterisations of the invention.

[0041] Brief Description of the Drawings

[0042] Other features of the invention will be apparent from the following description of preferred embodiments shown by way of example only with reference to the accompanying drawings, in which;

[0043] Figure 1 shows a schematic view of a dehumidifier apparatus according to the prior art;

[0044] Figure 2 shows a schematic view of a dehumidifier apparatus according to an embodiment of the invention; and

[0045] Figure 3 shows steps of a method according to an embodiment of the invention. Detailed Description

[0046] In accordance with the invention, a dehumidifier apparatus comprises a dehumidifier housing, a liquid circulation system and a vacuum pump disposed between the dehumidifier housing and the liquid circulation system. The interior of the dehumidifier housing is separated into an air chamber and a vacuum chamber by a water vapour permeable membrane, the air chamber having an air inlet to receive humid air, and an air outlet through which dehumidified air, in use, exits.

[0047] Figure 2 shows a schematic view of a dehumidifier apparatus according to an embodiment of the invention, generally designated 20. In this embodiment, the dehumidifier apparatus 20 has a dehumidifier housing 22 which is separated into an air chamber 24 and a vacuum chamber 26 by a membrane 28, preferably a water vapour permeable membrane, as is known in the art and discussed hereinabove. In this embodiment, the air chamber 24 has an air inlet 30 to receive a current of humid air shown by arrow 31, and an air outlet 32 to output a current of air with a reduced humidity shown by the arrow 33.

[0048] As will be appreciated by skilled persons, other apparatus such as a fan (not shown) may be required to create the current of air into and out of the air chamber 24. For example, an air driving device comprising an air compression pump disposed at the air inlet 30 and / or an air extraction pump disposed at the air outlet 32 may be used.

[0049] In accordance with the invention, a vacuum pump inlet 35 of the vacuum pump 34 is in fluid communication with the vacuum chamber 26. In an embodiment, the vacuum pump inlet 35 of the vacuum pump 34 is in fluid communication with the vacuum chamber 26 via an outlet port 37 of the dehumidifier housing 22. In an embodiment, the vacuum pump 34 comprises a vacuum compressor configured to receive the fluid as a permeate from the vacuum chamber 26 and to compress the permeate to a pressure lying within the range 3 to lOkPa, and preferably 5 kPa. It will be appreciated that the permeate is humid air and is a mixture of air and water vapour. However, the water vapour would be the predominant component of the permeate.

[0050] Further, in accordance with the invention, a fluid conduit 36 extends between a vacuum pump outlet 41 of the vacuum pump 34 and a vacuum mixing condenser 40 of the liquid circulation system, generally designated 39. More particularly, in the embodiment of Fig. 2, the vacuum chamber 26 has an outlet in fluid communication with a vacuum compressor 34 to provide a partial vacuum thereto. The vacuum compressor 34 may be alternatively termed a vacuum pump 34. The vacuum compressor 34 has an output pipe (example of a fluid conduit) 36 with an outlet 38 to deliver a permeate (i.e. humid air and water) to a vacuum mixing condenser 40. The vacuum mixing condenser 40 may alternatively be termed a condenser 40. In the embodiment of Fig. 2, the vacuum mixing condenser 40 is a vessel with circulation liquid (e.g. water) 42 therein, and a portion of the output pipe 36 is within the water 42 so that the outlet 38 is also in the water. The gases mixture on the permeate side (i.e. in the vacuum chamber 26) are compressed under a low-pressure ratio by the vacuum compressor 34, and as shown by an arrow 43, the compressed moisture / air that is output from the vacuum compressor 34 directly mixes with the cooling water 42 in the vacuum mixing condenser 40. In the description herein, references are made to water as the circulation liquid 42; however, other circulation liquids may be used in place of water. The circulation liquid may comprise water with a predetermined proportion of biocidal additive or anti-bacterial additive. Alternatively, the circulation liquid may comprise a thermal oil, aliphatic hydrocarbons fluids and / or or a desiccant liquid.

[0051] In an embodiment, the fluid conduit 36 extends such that an end thereof, which may be opposite the vacuum pump outlet 37, extends by a predetermined distance into the interior of a vacuum mixing condenser 40.

[0052] Thus, in accordance with the invention, in use, fluid containing moisture exits the fluid conduit 36 below the surface of circulation liquid 42 in the vacuum mixing condenser 40.

[0053] Further, in accordance with the invention, the liquid circulation system comprises a liquid circulation arrangement configured for receiving circulation liquid 42 from the vacuum mixing condenser 40 in which the fluid that exits the fluid conduit is mixed and / or condensed, and for returning cooled circulation liquid 42 to the vacuum mixing condenser 40.

[0054] In an embodiment, the liquid circulation arrangement comprises a multiphase pump 48 disposed, in direction of flow in the liquid circulation system 39, between the liquid outlet 46 of the vacuum mixing condenser 40 and the liquid inlet 44 thereof. In the embodiment of Fig. 2, the vacuum mixing condenser 40 has a liquid inlet 44 and a liquid outlet 46. The liquid outlet 46 may be located at an upper part of the vacuum mixing condenser 40, and the liquid inlet 44 may be located at a lower part of the vacuum mixing condenser 40. In this embodiment, the liquid outlet 46 of the vacuum mixing condenser 40 is in fluid communication with an inlet of the multiphase pump 48. The positions of the fluid conduit 36 and the liquid inlet are largely independent. The liquid inlet 44 may be at the bottom of the vacuum mixing condenser 40 where it is lower than the fluid conduit 36. Both the fluid conduit 36 and liquid inlet 44 are preferably placed at lower positions of the vacuum mixing condenser 40.

[0055] In an embodiment, the liquid circulation arrangement comprises a cooler 50 disposed, in the direction of flow in the liquid circulation system 39, between the liquid outlet 46 of the vacuum mixing condenser 40 and the liquid inlet 44 thereof. In the embodiment of Fig. 2, an outlet of the multiphase pump 48 is in fluid communication with an inlet of a cooler 50. Whereas in the vacuum mixing condenser 40 the air and water are at a relatively low pressure, the water leaving the cooler 50 is at an atmospheric pressure.

[0056] Thus, in an embodiment, the liquid circulation arrangement comprises, in sequence in the direction of flow in the liquid circulation system 39 between the liquid outlet 46 of the vacuum mixing condenser 40 and the liquid inlet 44 thereof, the multiphase pump 48 and the cooler 50.

[0057] In an embodiment, an outlet of the cooler 50 is in fluid communication with the liquid inlet 44 of the vacuum mixing condenser 40. The cooler 50 may also have a drain 52 to remove excess water as required. The cooler 50 may also has a vent 54 to release air to atmosphere as required.

[0058] In embodiments, the vacuum mixing condenser 40, the multiphase pump 48 and the cooler 50 together form components of the water circulation system 39. As shown in Figure 2, the general direction of water circulation is anticlockwise, and valves (i.e. oneway valves) may be used as required within the water circulation 39 system to promote or maintain water circulation in one direction.

[0059] In embodiments, each of the vacuum mixing condenser 40, the multiphase pump 48 and the cooler 50 may be at different heights relative to each other. In embodiments, the multiphase pump 48 is disposed at a lower elevation than the vacuum mixing condenser 40 and / or the cooler 50 is disposed at a lower elevation than the vacuum mixing condenser 40. In the embodiment of Fig. 2, an elevation difference between the vacuum mixing condenser 40 and the multiphase pump 48 is shown by arrow 56. An elevation difference between the vacuum mixing condenser 40 and the cooler 50 is shown by arrow 58. Utilising such a height difference permits energy to be “recovered” from the pressurised water circulation system as discussed below.

[0060] The height elevation of multiphase pump 48 shown by arrow 56 is flexible. However, in the embodiments described herein, the multiphase pump 48 should be higher than or at the same height as the cooler 50, but not lower than the cooler 50 for the following reasons. If the multiphase pump 48 is placed at a similar elevation level to the cooler 50, then the fluid in the conduit 60 utilizes gravitational work (i.e. shown by arrow 56) for pressurization and increase the inlet pressure of the multiphase pump 48 with a lower air volumetric flow rate, thereby reducing the pumping power and technical requirements. If the multiphase pump 48 is placed at a higher elevation than the cooler, it can still use gravity to increase its inlet pressure (i.e. its outlet pressure can be less than 1 atm).

[0061] It will be understood that the power input of the vacuum compressor 34 is influenced by its outlet pressure, which is related to the water temperature in the vacuum mixing condenser 40 and is independent from the height of the cooler 50. On the contrary, the gravitational work mentioned previously influences the inlet pressure of the multiphase pump 48 and its power input.

[0062] The liquid circulation arrangement will briefly be addressed in more detail. In an embodiment, the liquid outlet 46 is disposed at a higher elevation on the vacuum mixing condenser 40 than the liquid inlet 44 thereof. Further, in an embodiment, a first liquid circulation conduit 60 extends between the liquid outlet 46 and the multiphase pump 48, the first liquid circulation conduit 60 or a substantial part thereof preferably extending vertically or substantially vertically. In an embodiment, a second liquid circulation conduit 62 extends between the multiphase pump 48 and the cooler 50, the second liquid circulation conduit 62 extending horizontally or substantially horizontally. In an embodiment, a third liquid circulation conduit 64 extends between the cooler 50 and the liquid inlet 44 of the vacuum mixing condenser 40, whereby circulation liquid in the cooler 50 is transferable to the vacuum mixing condenser 40 for mixing with circulation liquid therein. In embodiments, the third liquid circulation conduit 64 comprises (i) a first part 66, preferably extending vertically or substantially vertically, (ii) a second part 68, preferably extending horizontally or substantially horizontally and / or (iii) a third part 70, preferably extending vertically or substantially vertically. As used herein, “substantial part” means 70-99.99% thereof, more preferably 80-99.99% thereof, and more preferably 90-99.99% thereof. As used herein, “substantially vertically” and “substantially horizontally” mean, respectively, within 10 degrees, more within 5 degrees, and more preferably within 2 degrees, of the vertical and horizontal. However, it will be understood that due to the directional effect of gravity and that gravitational work is influence by the elevation difference, the conduits do not necessarily need to be vertical to meet the elevation difference. For flexibility of installation, a slope of the conduits is allowed, as long as there is an elevation difference as described. In other words, whereas the elevation is significant, the slope or angle of the conduit is less significant.

[0063] Also shown in the conduit 64 is a throttle valve 69, which is a valve to control the flow of fluid within the circulation system 39. For example, a further pressure reduction can be imparted by the throttle valve 69 if the elevation difference is not sufficient (i.e. if the dimension shown by arrow 56 is small such as Im to 3m), whereby the throttle valve 69 is operable to reduce fluid pressure before it enters the vacuum mixing condenser 40.

[0064] As noted above, in an embodiment, the dehumidifier apparatus includes a controller coupled to the vacuum pump 34, the controller being configured to supply a first drive signal to the vacuum pump 34 to cause fluid received at the vacuum pump inlet 35 from the vacuum chamber 26 to be compressed and output via the outlet port 37. In an embodiment, the controller is further coupled to the multiphase pump 48, the controller being configured to supply a second drive signal to the multiphase pump 48 to cause circulation liquid received from the circulation liquid outlet 46 of the vacuum mixing condenser 40 to be compressed and output in the direction of flow in the circulation system 39.

[0065] Referring again to Fig. 2, during operation of the dehumidifier apparatus 20 the humid air 31 flows into the air chamber 24 of the dehumidifier chamber 22 at a pressure of about 1 atmosphere (i.e. about lOlkPa) and the dehumidified air 33 is used for ventilation or evaporative cooling purposes. Moisture is transferred through the membrane 28 into the vacuum chamber 26 such that low-pressure air with moisture is within the vacuum chamber 26. The low-pressure air and moisture are then compressed by the vacuum compressor 34 to a pressure of about 3 to 10 kPa and output via the pipe 36. Typically pressure of the water 42 within the vacuum mixing condenser 40 may be 5kPa. It will be appreciated that the water 42 is typically a water / air mixture. The pipe 36 is cooled by the water 42 in the vacuum mixing condenser 40 (i.e. cooling water from the cooler 50), and the compressed moist air within the pipe 36 is condensed directly in the vacuum mixing condenser 40. The condensed moisture, cooling water 42, and non-condensable air flow leave the vacuum mixing condenser 40 via the water outlet 46, and are first pressurized by gravity due to the elevation difference shown by arrow 56 and then further pressurized by the multiphase pump 48. The air and water mixture from the vacuum mixing condenser 40 experiences a quasi -isothermal pressurization process through a multiphase pump 48. The pressurized water / air mixture flows out of the multiphase pump 48 and into the cooler 50 where it is cooled down. The cooler 50 may be similar to a conventional cooling tower.

[0066] Air from the multiphase pump 48 is vented to atmosphere via the vent 54 of the cooler 50. Any excess water from the cooler 50 may also be removed as required via the drain 52, although it will be appreciated that in general the water may be evaporated by the cooler 50, and that the cooler 50 may require an additional supply of water (not shown) if needed. The pressure at the cooler 50 may be about 1 atmosphere (i.e. about lOlkPa). The cooled water from the cooler 50 flows to the inlet 44 of the vacuum mixing condenser 40 with a reduced pressure due to the elevation difference shown by arrow 58. Further pressure reduction may be made by the throttle valve 69 as mentioned above if the elevation difference is not sufficient. During operation of the dehumidifier apparatus 20 the cooling water 42 absorbs heat from the output pipe 36 and from the fluid exiting the output pipe 36, and the vacuum mixing condenser 40 also carries away the non-condensable gas and water. In the case that the multiphase pump 48 is above the cooler 50, the fluid exiting the multiphase pump 48 is further pressurized by gravity due to the elevation difference with the cooler 50.

[0067] It is envisaged that the membrane 28 of the dehumidifier chamber 22 may have an area (i.e. an area of one surface of the membrane 28) of about Im2, but the membrane 28 may have a larger or smaller area surface. There are several different material types that may be used for the membrane 28, for example, zeolitic membranes, polymer membranes, and mixed matrix membranes. Polymer membranes are typically physically robust. Zeolitic membranes are not self-supported but generally grow on porous support materials like aluminium or stainless steel. Mixed matrix membranes combine the polymer membranes and zeolite membranes. Some examples of suitable membranes are listed in the following Table 1, which shows a water vapor permeability and selectivity for various polymers at 30 degrees Celsius. It will be understood that the membrane 28 operates via a chemical potential difference of moisture between the two sides of the membrane 28, and does not require heat input to the membrane 28.

[0068] It is envisaged that the height difference between the vacuum mixing condenser 40 and the multiphase pump 48 (i.e. arrow 56), and the vacuum mixing condenser 40 and the cooler 50 (i.e. arrow 58) may be up to 10.3 meters. The height difference may be zero or close to zero, but it is envisaged that a working height difference may be between 0 meters to 10.3 meters. However, an elevation difference between the vacuum mixing condenser 40 and multiphase pump 48 of about 2m to 3m is has been found to be sufficient to provide the gas volume fraction below 50%, which is handleable by commonly available multiphase pumps 48.

[0069] The upper working height difference of 10.3m is significant because this is the maximum height for a column of water that can be supported by an average atmospheric pressure at sea level. Although it will be appreciated that the maximum working height difference may be less than 10.3m if the dehumidifier apparatus 20 is used above sea level, or greater than 10.3m if the dehumidifier apparatus 20 is used below sea level. For example, if the apparatus is used above sea level at an altitude of 1000m, then the maximum working height difference may be 9.1m (i.e. equivalent to a pressure of 89874.57Pa).

[0070] The inventor has determined that utilising a height difference of about 10 meters may permit total power input to the dehumidifier apparatus 20 to be reduced by 10% (i.e. reducing a typical power consumption of lOOWatts to be reduced by lOWatts). The power input of the vacuum pump 34 is influenced by its outlet pressure, which is related to the water temperature in the vacuum mixing condenser 40 and is independent from the height of the cooler 50. On the contrary, the gravitational work influences the inlet pressure of the multiphase pump 48 and its power input. By reducing the pump input power, the dehumidifier input power drops. Accordingly, utilising such a height difference permits energy to be “recovered” from the pressurised water circulation system.

[0071] The cooler 50 may be typically located on an outside of a building, and for example on an exterior wall of the building. In such an arrangement the cooler 50 may be up to 10.3m in a vertical length dimension so that a cooling effect can be achieved along a full height thereof, and so that the energy to be recovered from the pressurised water circulation system. It will be appreciated that a controller (not shown) may be coupled to the various components of a water circulation system such as the vacuum mixing condenser 40, the multiphase pump 48 and the cooler 50 for operating them as required.

[0072] An improved cooling system may be provided using the teaching of the present invention. The cooling system may comprise a dehumidifier apparatus as set out hereinabove or according to the appended claims, and an air driving device; and the controller (not shown) may be configured to supply a third drive signal to the air driving device to drive the ambient air between the air inlet and the air outlet, from which cooled air is expelled. In an embodiment, the air driving device comprises an air compression pump disposed at the air inlet 30 and / or an air extraction pump disposed at the air outlet 32.

[0073] In accordance with another aspect of the invention, there is provided a method of operating a dehumidifier apparatus 20. Figure 3 shows steps of a method according to an embodiment of the invention, generally designated 80. It will be appreciated that the steps may be performed in a different order, and may not necessarily be performed in the order shown in Figure 3. Initially, at step 82 there is the step of providing a controller (not shown), coupled to the vacuum pump 34 and / or to the multiphase pump 48 and optionally to one or more valves (not shown) used in the circulation system 39.

[0074] The method optionally includes next determining at step 84 the current state / position of one or more valves (not shown). There follows, at step 86 and depending upon the determined current state / position of valves (not shown), optionally the step 82 of moving the one or more valves of circulation system 39 to an operational state / position.

[0075] Subsequently, the method comprises supplying, at step 88, by the controller (not shown) a first drive signal to the vacuum pump 34 to cause fluid received at the vacuum pump inlet 35 from the vacuum chamber 26 to be compressed and output via the outlet port 41.

[0076] The method may comprise supplying, at step 90, by the controller (not shown), a second drive signal to the multiphase pump 48 to cause circulation liquid 42 received the liquid outlet 44 of the vacuum mixing condenser 40 to be compressed and output in the direction of flow in the liquid circulation system 39.

[0077] In the case of the above-described cooling system, its method of operating may include: providing a cooling system as described hereinabove or according to any of claims 26 - 27 of the appended claims; and supplying, by the controller (not shown), a third drive signal to the air driving device (not shown) to drive the ambient air between the air inlet 30 and the air outlet 32, from which cooled air is expelled.

[0078] The above embodiments have several significant innovative and advantageous aspects as discussed below.

[0079] Firstly, the inventor has used a vacuum mixing condenser 40 in the membrane-based dehumidifier apparatus 20, which is not known from the prior art. The compressed moisture from the vacuum pump 34 is directly mixed and condensed by the cooling water from the cooler 50 without a secondary heat exchanger, which is not known from the prior art. In contrast the prior art arrangements require the moisture to be condensed in a heat exchanger.

[0080] The inventor has discovered that addressing the challenge of large power consumption for dehumidifier apparatuses can be at least partially achieved by employing the vacuum mixing condenser 40 to greatly decrease an outlet pressure for the vacuum compressor 34 (e.g. from 101 kPa to 5 kPa, or within the range 3 to lOkPa). Moisture is in direct contact with the cooling water 42 in the vacuum mixing condenser 40, thereby facilitating an effective heat exchange to condense water from the fluid that exits the vacuum compressor 34.

[0081] Secondly, the inventor has discovered a way to recover energy in the water circulatory system by using an elevation difference, whereby condensed moisture, cooling water, and non-condensable air from the vacuum mixing condenser 40 are pressurized by gravity before entering the multiphase pump 48. The multiphase pump 48 then further pressurises condensed moisture, cooling water, and non-condensable air. In this manner the multiphase pump 48 is assisted by a gravity-driven pre-pressurization process. The cooling water not only carries away air in the vacuum mixing condenser 40, but also helps to pressurize the air with high water density.

[0082] Thirdly, the inventor has discovered a way to eliminate the requirement for a second vacuum pump for the extracting air in the permeate to the ambient. Air permeation through the membrane 28 is inevitable to some extent, and it is challenging to handle the permeated air. Whereas the prior art systems use a second vacuum pump to remove the air from the permeate side, in the above embodiments the water-air mixture is pressurized by gravity to a pressure close to or equal to an atmospheric pressure when it reaches the multiphase pump 48 which is then passed on to the cooler 50. Any air from the multiphase pump 48 is vented to atmosphere via the vent 54 of the cooler 50.

[0083] Compared with the prior art vacuum membrane-based dehumidification systems, the invention, at least in embodiments, may reduce the power consumption for dehumidification by 80%. For example, to compress 1g of moisture from about 2kPa to lOlkPa in a prior art system the power consumption in the ideal process is about 874W. In contrast, the above embodiments may only require 138W when the moisture is compressed to 5kPa because at this pressure the moisture can be condensed by a cooling water temperature of 32.8 degrees Celsius and the power consumption is reduced by 84%. Further, the above embodiments are able to dehumidify air to 50% relative humidity at 25 degrees Celsius.

[0084] Overall it will be understood that the embodiments of the invention aim to solve problems in air dehumidification and evaporative cooling, and advantageously uses only one membrane 28, with the permeated air can being carried away by the cooling water from the vacuum mixing condenser 40. However, it will be appreciated that more than one membrane can be used in series or in parallel in the dehumidifier housing 22 to increase the dehumidification capacity as required. As air permeation through the membrane 28 is unavoidable, the prior art systems struggle to maintain a low pressure at the outlet of the vacuum compressor 34 because as more air accumulates the air pressure increases, and the vacuum compressor 34 power consumption rises. The above embodiments have the effect of mixing the permeated air and moisture at the vacuum compressor 34, the vacuum mixing condenser 40, and the multiphase pump 48 for later separation at the cooler 50.

[0085] Compared to the prior art dehumidification systems, the embodiments of the invention lead to a lower power consumption due to the direct mixing of moisture and circulating liquid (e.g. cooling water 42). The embodiments of the invention provide direct condensation of moisture by the cooling water 42 with the advantages of a decreased condensation temperature and pressure, less pressure drop, and require a relatively small vacuum mixing condenser 40. For example, for a prior art system with a cooling water temperature of 32.8 degrees Celsius, the condensation temperature of the moisture may be 37.8 degrees Celsius or even higher in order to efficiently transfer heat through the exchanger. With the prior art systems, the outlet pressure of the vacuum pump can be higher than 6.6kPa with a power consumption of 187W for compressing 1g moisture. Moreover, for the prior art systems, when the vacuum pump for extracting air into the atmosphere is taken into account the power consumption will be even larger. In comparison, the above embodiments may save at least 27% of the required electricity, and eliminate secondary heat transfer, whilst also overcoming the challenge of air removal.

[0086] Another important significance of the above embodiments is the removal of air after it is compressed by the compressor (i.e. the vacuum pump 34). Membranes are not ideal, and the permeation of air the membrane 28 is inevitable to some extent. Even if 1% of air is present in the permeated air in the vacuum chamber 26 it will have a significant impact on the power consumption of the vacuum pump 34. The reason is, under vacuum conditions, the densities of air and water vapor are low, and the specific volumes are large. For example, if the flow rate of the moisture / air from the vacuum pump 34 is 1 g / s (with % of air) and the outlet pressure of the vacuum pump 34 is 5kPa with a temperature of 33 degrees Celsius, then the specific volume will be 28.1 cubic meter per kg and the volumetric flow rate will be 28.1 litres per second. If air is not removed in time, then it will occupy about 204 litres of space in 10 minutes (specific volume of air at 5kPa and 33 degrees Celsius is 17.6 cubic meters per Kg). The vacuum chamber 26 has a high technical requirement, and a large container will not be cost-effective meaning that air should be removed in a timely manner. With the prior art arrangement of Figure 1 the removal of air depends on a vacuum pump, which may need to operate simultaneously with the compressor. In the process, not only air but also moisture will be extracted into the ambient by the vacuum pump, which is inefficient because water is in binary liquid-vapor phase in the loop and its saturation vapour pressure will be about 5kPa. The moisture flow rate through the prior art vacuum pump shown in Figure 1 may be many times higher than that of air, leading to large power consumption by the vacuum pump. In contrast, with the above embodiments shown in Figures 2 and 3, air is removed by the circulation liquid (e.g. water) 42 without the requirement for second vacuum pump.

[0087] It will be understood that the multiphase pump 48 is a liquid-gas mixer pump that transport of liquids and gas as one common mixture. The multiphase pump 48 is a general term and may be any pump that is capable of such transport of liquid and gas as common mixture. The multiphase pump 48 of the embodiments shown in Figures 2 and 3 can continuously remove air and send it to the ambient (via the vent 54) without the requirement for a second vacuum pump because the cooling water 42 has a large flow rate. For example, to cool Ig / s of moisture (the latent heat being about 2500kJ / kg), the flow rate of the cooling water 42 can be 200 times higher (e.g. 0.2 kg / s). Therefore, the vacuum mixing condenser 40 provides not only efficient moisture condensation but also air removal.

[0088] From the foregoing the inventor has determined that the five main factors on the coefficient of performance for the dehumidification apparatus 20 are the selectivity of the membrane 28, the flow rate of the cooling water 42, the permeance pressure, the pressure of the vacuum mixing condenser 40, and the gravitational work provide by the height difference (i.e. shown by arrows 56, 58).

Claims

CLAIMS1. A dehumidifier apparatus, comprising a dehumidifier housing, a liquid circulation system, and a vacuum pump disposed between the dehumidifier housing and the liquid circulation system, wherein an interior of the dehumidifier housing is separated into an air chamber and a vacuum chamber by a water vapour permeable membrane, the air chamber having an air inlet to receive humid air, and an air outlet to output dehumidified air, wherein a vacuum pump inlet of the vacuum pump is in fluid communication with the vacuum chamber, wherein a fluid conduit extends between a vacuum pump outlet of the vacuum pump and a vacuum mixing condenser of the liquid circulation system, wherein fluid containing moisture is arranged to exit the fluid conduit below a surface of circulation liquid within the vacuum mixing condenser, and wherein the liquid circulation system comprises a liquid circulation arrangement configured for receiving circulation liquid from the vacuum mixing condenser in which the fluid that is output from the fluid conduit is mixed and / or condensed, and for returning cooled circulation liquid to the vacuum mixing condenser.

2. A dehumidifier apparatus according to claim 1, wherein the liquid circulation arrangement comprises a multiphase pump disposed, in direction of flow in the liquid circulation system, between the liquid outlet of the vacuum mixing condenser and the liquid inlet thereof.

3. A dehumidifier apparatus according to claim 2, wherein the multiphase pump is disposed at a lower elevation than the vacuum mixing condenser.

4. A dehumidifier apparatus according to claim 2 or 3, wherein the multiphase pump is disposed at a lower elevation than the vacuum mixing condenser by a first distance, wherein the first distance (i) lies in the range 0.1 to 10m, (ii) lies in the range 9 to 10m or (iii) is 10m.

5. A dehumidifier apparatus according to any of the preceding claims, wherein the liquid circulation arrangement comprises a cooler disposed, in the direction of flow in the liquid circulation system, between the liquid outlet of the vacuum mixing condenser and the liquid inlet thereof.

6. A dehumidifier apparatus according to claim 5, when dependent upon any of claims 2 to 4, wherein the liquid circulation arrangement comprises, in sequence in the direction of flow in the liquid circulation system between the liquid outlet of the vacuum mixing condenser and the liquid inlet thereof, the multiphase pump and the cooler.

7. A dehumidifier apparatus according to claim 5 or 6, wherein the cooler is disposed at a lower elevation than the vacuum mixing condenser.

8. A dehumidifier apparatus according to claim 5 or 6, when dependent upon claim 4, wherein the cooler is disposed at a lower elevation than the vacuum mixing condenser by a second distance.

9. A dehumidifier apparatus according to claim 8, when dependent upon claim 4, wherein the first distance is substantially equal to or less than the second distance.

10. A dehumidifier apparatus according to claim 8, when dependent upon claim 4, wherein the second distance (i) lies in the range 0.1 to 10.3m or (ii) lies in the range 9 to 10.3m.

11. A dehumidifier apparatus according to any of the preceding claims, wherein the fluid conduit extends such that an end thereof opposite the vacuum pump outlet extends by a predetermined distance into the interior of the vacuum mixing condenser.

12. A dehumidifier apparatus according to claim 11, wherein the fluid conduit comprises an elongate pipe.

13. A dehumidifier apparatus according to any of the preceding claims, wherein the fluid conduit is coupled for fluid communication with the vacuum mixing condenser at a point below the liquid inlet thereof.

14. A dehumidifier apparatus according to claim 2, or any claim dependent thereon, wherein the liquid outlet is disposed at a higher elevation on the vacuum mixing condenser than the liquid inlet thereof.

15. A dehumidifier apparatus according to claim 2, or any claim dependent thereon, wherein a first liquid circulation conduit extends between the liquid outlet and themultiphase pump, the first liquid circulation conduit or a substantial part thereof preferably extending vertically or substantially vertically.

16. A dehumidifier apparatus according to claim 2, or any claim dependent thereon, wherein a second liquid circulation conduit extends between the multiphase pump and the cooler, the second liquid circulation conduit preferably extending horizontally or substantially horizontally.

17. A dehumidifier apparatus according to claim 2 and 5, or any claim dependent thereon, wherein a third liquid circulation conduit extends between the cooler and the liquid inlet of the vacuum mixing condenser, whereby circulation liquid in the cooler is transferable to the vacuum mixing condenser for mixing with circulation liquid therein.

18. A dehumidifier apparatus according to claim 17, wherein the third liquid circulation conduit comprises (i) a first part, preferably extending vertically or substantially vertically, (ii) a second part, preferably extending horizontally or substantially horizontally and / or (iii) a third part, preferably extending vertically or substantially vertically.

19. A dehumidifier apparatus according to any of the preceding claims, wherein the vacuum pump comprises a vacuum compressor configured to receive as the fluid a permeate from the vacuum chamber and to compress the permeate to a pressure lying within the range 3 to lOkPa, and preferably 5 kPa.

20. A dehumidifier apparatus according to claim 5, or any claim dependent thereon, wherein the cooler (i) comprises a cooling tower, (ii) has a vertical length dimension of up to 10.3m, (iii) has an upper vent for venting air received from the multiphase pump to atmosphere via the vacuum mixing condenser and / or (iv) has a lower drain or overflow whereby any excess circulation liquid received by the cooler is removable.

21. A dehumidifier apparatus according to any of the preceding claims, including a controller coupled to the vacuum pump, the controller being configured to supply a first drive signal to the vacuum pump to cause fluid received at the vacuum pump inlet from the vacuum chamber to be compressed and output via the outlet port.

22. A dehumidifier apparatus according to claim 21, when dependent upon claim 2, wherein the controller is further coupled to the multiphase pump, the controller being configured to supply a second drive signal to the multiphase pump to cause circulation liquid and vapour received from the circulation liquid outlet of the vacuum mixing condenser to be compressed and output in the direction of flow in the circulation system.

23. The dehumidifier apparatus according to any of the preceding claims, wherein the vacuum pump inlet of the vacuum pump is in fluid communication with the vacuum chamber via an outlet port of the dehumidifier housing.

24. The dehumidifier apparatus according to any of the preceding claims, wherein the circulation liquid comprises (i) water, or (ii) water and a predetermined proportion of biocidal additive or anti-bacterial additive.

25. The dehumidifier apparatus according to any of the preceding claims, wherein the circulation liquid comprises thermal oil, aliphatic hydrocarbons fluids and / or a desiccant liquid.

26. A cooling system comprising: a dehumidifier apparatus according to any of the preceding claims; an air driving device; wherein a controller is configured to supply a third drive signal to the air driving device to drive ambient air between the air inlet and the air outlet, from which dehumidified and / or cooled air is expelled.

27. The cooling system of claim 26, wherein the air driving device comprises an air compression pump disposed at the air inlet and / or an air extraction pump disposed at the air outlet.

28. A method of operating a dehumidifier apparatus, the method including: providing a dehumidifier apparatus according to any of claims 1 - 27; providing a controller, coupled to the vacuum pump, the method comprising supplying, by the controller a first drive signal to the vacuum pump to cause fluidreceived at the vacuum pump inlet from the vacuum chamber to be compressed and output via the outlet port.

29. A method according to claim 28, when dependent upon claim 2, further comprising supplying, by the controller, a second drive signal to the multiphase pump to cause circulation liquid received from the liquid outlet of the vacuum mixing condenser to be compressed and output in the direction of flow in the liquid circulation system.

30. A method of operating a cooling system, the method including: providing a cooling system according to any of claims 26 - 27; and supplying, by the controller, a third drive signal to the air driving device to drive the ambient air between the air inlet and the air outlet, from which dehumidified and / or cooled air is expelled.

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