WO2025005867A1

WO2025005867A1 - Water recovery system for a building hvac installation

Info

Publication number: WO2025005867A1
Application number: PCT/SG2023/050452
Authority: WO
Inventors: Chung Ming Kelvin LOH
Original assignee: Air Royal Pte Ltd
Current assignee: Air Royal Pte Ltd
Priority date: 2023-06-28
Filing date: 2023-06-28
Publication date: 2025-01-02
Anticipated expiration: 2025-12-28

Abstract

A water recovery system for a building HVAC installation having one or more cooling towers comprising: a water recovery unit (6) for receiving a warm moist air stream from the cooling tower(s) (5), and including a cooling heat exchanger (37), and a water tank (41) for collecting water condensed from the cooling heat exchanger, and for transferring a dry air stream to the HVAC installation; wherein the water condensed by the water recovery unit is transferred to the cooling tower(s) for reuse therein.

Description

WATER RECOVERY SYSTEM FOR A BUILDING HVAC INSTALLATION

FIELD

[0001] The present invention relates to a water recovery system for a building HVAC installation.

BACKGROUND

[0002] The following discussion of the background to the invention is intended to facilitate an understanding of the present invention only. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge of the person skilled in the art in any jurisdiction as at the priority date of the invention.

[0003] HVAC installations in large buildings typically use cooling towers to cool water used within the HVAC installation. The cooling tower operates by bringing air and water into direct contact with each other in order to reduce the water’s temperature. This results in a small part of the water being evaporated as part of the cooling process. This results in an ongoing loss of water during operation of the HVAC installation which needs to be replenished from external sources. This water loss significantly adds to the operational costs in running of the HVAC installation. It would therefore be advantageous to minimise this water loss from the cooling towers.

[0004] Conventional cooling towers are ‘open loop’ in operation because of the loss of water through evaporation. An alternative option is to use ‘closed loop’ cooling towers that minimises or eliminates that amount of water lost through evaporation during operation. Such cooling towers operate using ‘adiabatic cooling’, where precooling pads are utilised to depress the ambient wet and dry bulb of the incoming air to the cooling tower. This allows for greater heat rejection within the cooling water, while at the same time minimising or eliminating water loss through evaporation. Such closed loop cooling towers however typically require about ten times more installation space than conventional cooling towers. This can therefore make it impractical or not possible to install such closed loop cooling towers where space is limited or not available for such an installation. Furthermore, such closed loop cooling towers also typically require high-cost heat exchangers made using aluminium or copper material. This can result in the capital costs associated with a closed loop cooling tower installation about 10 to 20 times higher than a comparable conventional cooling tower installation.

[0005] An object of the invention is to ameliorate one or more of the above- mentioned difficulties.

SUMMARY

[0006] According to an aspect of the present disclosure, there is provided a water recovery system for HVAC installations having one or more cooling towers comprising: a water recovery unit for receiving a warm moist air stream from the cooling tower(s), and including a cooling heat exchanger, and a water tank for collecting water condensed from the cooling heat exchanger, and for transferring a treated dry air stream to the building or HVAC installation; wherein the water condensed by the water recovery unit is transferred to the cooling tower(s) for reuse therein.

[0007] In some embodiments, the cooling heat exchanger is an evaporator heat exchanger, and the water recovery unit further comprises a condenser heat exchanger and a compressor for circulating refrigerant to the condenser heat exchanger and the evaporator heat exchanger, wherein the condenser heat exchanger heats a dry air stream from the evaporator heat exchanger.

[0008] In some embodiments, the cooling heat exchanger is a chilled water heat exchanger supplied with chilled water from a water chiller unit of the HVAC installation.

[0009] In some embodiments, the water recovery system further comprises a turbine assembly including a turbine chamber and turbine wheel accommodated therein.

[0010] In some embodiments, the turbine assembly is adapted to receive the warm moist air stream from the cooling tower(s), and the water recovery unit is located downstream from an exhaust air outlet of the turbine assembly.

[0011 ] In some embodiments, the water recovery unit is located upstream from the turbine assembly which is adapted to receive and transfer the dry air stream from the water recovery unit to the HVAC installation.

[0012] In some embodiments, the turbine wheel is interconnected to a compressor wheel of a compressor assembly via a primary connecting shaft, the compressor assembly including a compressor chamber for accommodated therein the compressor wheel, wherein the compressor assembly directs ambient cool air back to the cooling tower(s).

[0013] In some embodiments, the compressor wheel is interconnected via the primary connecting shaft to an overdrive gearbox, and wherein the overdrive gearbox is interconnected to a generator via a secondary connecting shaft, the generator supplying electricity to at least the water recovery unit or to supplement other energy sources.

[0014] According to another aspect of the present disclosure, there is provided a method of recovering water from a building HVAC installation having one or more cooling towers comprising: transferring a warm moist air stream from the cooling tower(s) to a water recovery system comprising a water recovery unit including a cooling heat exchanger for condensing water from the warm moist air stream, collecting the condensed water in a water tank, transferring the condensed water back to the cooling tower(s) for reuse therein, and transferring a dry air stream from the water recovery unit to the HVAC installation.

[0015] In some embodiments, the cooling heat exchanger is an evaporator heat exchanger, and the water recovery unit further comprises a condenser heat exchanger and a compressor for supplying refrigerant to the condenser heat exchanger and the evaporator heat exchanger, the method further comprising heating the dry air stream from the evaporator heat exchanger with the condenser heat exchanger.

[0016] In some embodiments, the cooling heat exchanger is a chilled water heat exchanger supplied with chilled water from a water chiller unit of the HVAC installation,

[0017] Other aspects and features will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In the figure, which illustrate, by way of example only, an embodiment of the present invention,

[0019] Figure 1 is a schematic view of a water recovery system for an HVAC system according to the present disclosure.

[0020] Other arrangements of the invention are possible and, consequently, the accompanying drawing not to be understood as superseding the generality of the preceding description of the invention.

DETAILED DESCRIPTION

[0021] Throughout this document, unless otherwise indicated to the contrary, the terms “comprising”, “consisting of”, “having” and the like, are to be construed as non- exhaustive, or in other words, as meaning “including, but not limited to”.

[0022] Furthermore, throughout the specification, unless the context requires otherwise, the word “include” or variations such as “includes” or “including” will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. [0023] Example embodiments of the present invention will now be described with reference to the accompanying drawings. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention. Other definitions for selected terms used herein may be found within the detailed description of the invention and apply throughout the description. Additionally, unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one or ordinary skill in the art to which this invention belongs. Where possible, the same reference numerals are used throughout the figures for clarity and consistency.

[0024] [Fig. 1] shows the water recovery system 1 in association with the HVAC installation 3 of a building 2. The HVAC installation includes one or more cooling towers 5 shown separately in [fig. 1 ] in association with the water recovery system 1 and installed within the building 2. The or each cooling tower 5 includes a semi outer enclosure 9 accommodating therein an upper exhaust fan 11 for drawing an ambient air stream12 into the enclosure 9, and for expelling a warm moist air stream 23 from the enclosure 9. The ambient air 12 is drawn though a infill material 19 provided within the enclosure 9, with a heated condenser water distribution system 13 provided over the infill material 19, the heated condenser water distribution system 13 including one or more distribution pipes 15, each pipe 15 is provided with a series of spray nozzles 17 to thereby allow heated condenser water 10 from the HVAC installation 3 to be sprayed over the infill material 19. The heated condenser water 10 passes generally downwardly though the infill material 19 and is brought into direct contact with the ambient air 12 passing generally upwardly through the infill material 19. A portion of the heated condenser water 10 evaporates into water vapour when brought into contact with the ambient air 12 thereby cooling the remainder of the water that drips downwardly from the infill material 19 to a collection basin 21 located at the base of the enclosure 9. The exhaust fan 11 exhausts a warm moist air stream 23 from the cooling tower 5 containing the water vapour evaporated within the cooling tower 9. This evaporated water can be recovered by the water recovery system 1 according to the present disclosure. It is to be appreciated that the present invention is not restricted to the type of cooling tower shown in [fig. 1 ] and that different types of cooling towers can be used. For example, the water recovery system 1 could alternatively be used on crossflow, counterflow, induced draft and forced draft cooling towers.

[0025] The warm moist air stream 23 from the cooling tower(s) 5 is collected from each cooling tower exhaust fan 1 1 using a duct assembly (not shown) to transfer the warm moist air stream 23 to the water recovery system 1 according to the present disclosure. The water recovery system 1 includes a water recovery unit 6 having a cooling heat exchanger 37 for cooling the incoming warm moist air stream 23 such that the water vapour held within the warm air stream 23 is condensed into water that can be collected as condensed water in a water tank 41 . The cooling heat exchanger 37 may be in the form of an evaporator heat exchanger. The now cooled air steam then passes through a condenser heat exchanger 39 within the water recovery unit 6 that treats the cooled air. The water recovery system 6 further includes a compressor 43 for circulating the refrigerant from the evaporator heat exchanger 37, and for compressing the refrigerant to increase the pressure and temperature of the refrigerant before transferring the compressed refrigerant to the condenser heat exchanger 39 where the heat from the refrigerant can be transferred to the cooled air stream as noted above. The water recovery unit 6 then supplies a treated dry air stream 24 to the HVAC installation 3 which can then be circulated through the conditioned space of the building 2.

[0026] The water recovery system 1 further comprises a turbine assembly 25 having a turbine housing 27 within which is located a turbine wheel 29. The warm moist air stream 23 from the cooling tower 9 can be delivered to the turbine assembly 25 before being discharged though the turbine assembly exhaust air outlet 30. The warm moist air steam 23 is discharged to the water recovery unit 6 which is located downstream from the turbine assembly exhaust air outlet 30 as shown in [fig. 1 ], It is however also envisaged that the water recovery unit 6 be located upstream from the turbine assembly air inlet 26. In this configuration, the turbine assembly 25 is adapted to receive and transfer the dry air stream 24 from the water recovery unit 6 to the HVAC installation 3.

[0027] The water-cooled chiller 7 is used within the building HVAC installation 3 to supplied chilled water to absorb ambient heat from the conditioned space of the building. It is also envisaged that the cooling heat exchanger 37 be alternatively be in the form of a chilled water heat exchanger supplied with chilled water from a water- cooled chiller 7 of the building HVAC installation 3. That water cooled chiller 7 receives water from both the water collection basin 21 of the cooling tower 5 and the water tank 41 of the water recovery system 6. This ensures that preferably over 90% of the water utilised by the HVAC installation 3 is recovered and recycled though the installation thereby reducing the total amount of water required to operate the HVAC installation 3.

[0028] The water recovery system 1 according to the present disclosure may also include features that can both increase the operational efficiency of the cooling towers 5 as well as reducing the amount of electricity that may be consumed by the HVAC installation 3. The turbine wheel 29 of the turbine assembly 25 is driven for rotation by the warm moist air stream 23 passing therethrough. The turbine wheel 29 is connected by a primary connecting shaft 28 to the compressor wheel 35 of a compressor assembly 31 . The rotation of the compressor wheel 35 draws an ambient air stream 32 into the compressor chamber 33 accommodating the compressor wheel 35. This ambient air stream 32 can then be supplied to the cooling towers 5. This then avoids the problem called ‘short circuiting’ where heated air discharged from the cooling towers 5 is redrawn back into the cooling towers 5 thereby reducing the operational efficiency of the cooling towers 5. The water recovery system 1 according to the present disclosure avoids this problem by both drawing away the warm moist air discharged from the cooling towers 5 as well as by supplying a cooler ambient air stream 32 to the cooling towers 5. The compressor wheel 35 is connected via the primary connecting shaft 28 to an overdrive gearbox 37, which is in turn connected via a secondary connecting shaft 36 to a generator 38. The rotation of the compressor wheel 35 therefore drives the generator 38 which then generates electricity that can be for example used to power the compressor 43 of the water recovery unit 6 as shown in [fig. 1 ] or which can be used to supplement the electricity supply to the HVAC installation 3.

[0029] The overdrive gearbox 37 may for example be a planetary gearbox and may have a gear ratio of between 1 :3 to 1 :300. The use of alternative gearbox types and gear ratios is also envisaged. The generator 38, which may be in the form of a dynamo or alternator, may be connected to a storage battery (not shown) to provide temporary storage of the electricity generated by the generator 38. In some applications, a transformer may be required after the generator 38. For example, the generator 38 will supply electricity to the transformer which will then convert the voltage and ampere of the electricity according to the temporary or permanent storage requirements for different respective applications.

[0030] The water recovery system 1 according to the present disclosure provides a number of advantages including: a) Reduced water usage by the HVAC installation due to the recovery of a significant amount of the water evaporated from the cooling towers; b) Reuse of cooler condensate water to feed back into cooling tower which contributes to improve to reduce load of the pump and water-cooled chiller, thus improving efficiency the system as a whole; c) Reduced electricity costs due to the generation of electricity from energy recovered from the HVAC system; d) Improved operational efficiency of the cooling towers due to the elimination of ‘short circuit’ issues and the supply of additional cooler air to the cooling towers; and e) Improved operational efficiency of the HVAC installation due to the supply of additional treated air to the system.

[0031] It should be appreciated by the person skilled in the art that the above invention is not limited to the embodiment described. It is to be appreciated that modifications and improvements may be made without departing from the scope of the present invention.

[0032] It should be further appreciated by the person skilled in the art that one or more of the above modifications or improvements, not being mutually exclusive, may be further combined to form yet further embodiments of the present invention. It is for example envisaged that a valve (not shown) could be added to either or both the turbine assembly 25 and the compressor assembly 31 to control the flow of incoming moving air source to the turbine wheel 29. The function of this valve is to arrest the amount of incoming moving air flow if there is any excessive air flow from the HVAC installation 3. Diversion of the incoming or outgoing moving air regulates the rotational speed of the turbine or compressor wheels 29,35, which in turn regulates the rotating speed of the compressor assembly 31. The primary function of the valve(s) is to regulate the maximum speed or pressure in the water recovery system 1 , to protect the turbine and compressor assemblies 29,35 overdrive gear box 21 and generator 23. It is also envisaged that a brake (not shown) may be also or alternatively added after the overdrive gearbox 37 and before the generator 37 to arrest to excessive incoming moving air source flow during excessive incoming moving air condition. The primary function of the brake is to regulate the maximum speed of the water recovery system 1 to protect the generator 37.

Claims

[Claim 1 ] A water recovery system for a building HVAC installation having one or more cooling towers comprising: a water recovery unit for receiving a warm moist air stream from the cooling tower(s), and including a cooling heat exchanger, and a water tank for collecting water condensed from the cooling heat exchanger, and for transferring a treated dry air stream to the HVAC installation; wherein the water condensed by the water recovery unit is transferred to the cooling tower(s) for reuse therein.

[Claim 2] A water recovery system according to claim 1 , wherein the cooling heat exchanger is an evaporator heat exchanger, and the water recovery unit further comprises a condenser heat exchanger and a compressor for circulating refrigerant to the condenser heat exchanger and evaporator heat exchanger, wherein the condenser heat exchanger heats a dry air stream from the evaporator heat exchanger.

[Claim 3] A water recovery system according to claim 1 , wherein the cooling heat exchanger is a chilled water heat exchanger supplied with chilled water from a water chiller unit of the HVAC installation.

[Claim 4] A water recovery system according to any one of the preceding claims, wherein the water recovery system further comprises a turbine assembly including a turbine chamber and turbine wheel accommodated therein.

[Claim 5] A water recovery system according to claim 4, wherein the turbine assembly is adapted to receive the warm moist air stream from the cooling tower(s), and the water recovery unit is located downstream from an exhaust air outlet of the turbine assembly.

[Claim 6] A water recovery system according to claim 4, wherein the water recovery unit is located upstream from the turbine assembly which is adapted to receive and transfer the dry air stream from the water recovery unit to the HVAC installation.

[Claim 7] A water recovery system according to any one of claims 4 to 6, wherein the turbine wheel is interconnected to a compressor wheel of a compressor assembly via a primary connecting shaft, the compressor assembly including a compressor chamber for accommodated therein the compressor wheel, wherein the compressor assembly transferred ambient cool air back to the cooling tower(s).

[Claim 8] A water recovery system according to claim 7, wherein the compressor wheel is interconnected via the primary connecting shaft to an overdrive gearbox, and wherein the overdrive gearbox is interconnected to a generator via a secondary connecting shaft, the generator supplying electricity to at least the water recovery unit or to supplement other energy sources.

[Claim 9] A method of recovering water from a building HVAC installation having one or more cooling towers comprising: transferring a warm moist air stream from the cooling tower(s) to a water recovery system comprising a water recovery unit including a cooling heat exchanger for condensing water from the warm moist air stream, collecting the condensed water in a water tank, transferring the condensed water back to the cooling tower(s) for reuse therein, and directs a dry air stream from the water recovery unit back to the HVAC installation.

[Claim 10] A method according to claim 9, wherein the cooling heat exchanger is an evaporator heat exchanger, and the water recovery unit further comprises a condenser heat exchanger and a compressor for supplying refrigerant to the condenser heat exchanger and evaporator heat exchanger, the method further comprising heating the dry air stream from the evaporator heat exchanger with the condenser heat exchanger.

[Claim 1 1 ] A method according to claim 9, wherein the cooling heat exchanger is a chilled water heat exchanger supplied with chilled water from a water chiller unit of the HVAC installation.

[Claim 12] A method according to any one of claims 9 to 1 1 , wherein the water recovery system further comprises a turbine assembly including a turbine chamber and turbine wheel accommodated therein, the turbine assembly being adapted to receive the warm moist air stream from the cooling tower(s), and the water recovery unit is located downstream from an exhaust air outlet of the turbine assembly.

[Claim 13] A method according to any one of claims 9 to 1 1 , wherein the water recovery system further comprises a turbine assembly including a turbine chamber and turbine wheel accommodated therein, the water recovery unit being located upstream from the turbine assembly which is adapted to receive and transfer the dry air stream from the water recovery unit to the HVAC installation.

[Claim 14] A method according to claim 12 or 13, wherein the turbine wheel is interconnected to a compressor wheel of a compressor assembly via a primary connecting shaft, the compressor assembly including a compressor chamber for accommodated therein the compressor wheel, wherein the compressor assembly transferred ambient cool air to the cooling tower(s).

[Claim 15] A method according to claim 14, wherein the compressor wheel is interconnected via the primary connecting shaft to an overdrive gearbox, and wherein the overdrive gearbox is interconnected to a generator via a secondary connecting shaft, the generator supplying electricity to at least the water recovery unit