Abstract:
In order to make use of disused chimneys within residences, a passive heat recovery and ventilation system is fitted within a chimney of a house, the system including inlet and outlet flow ducts fitted within the chimney flue, and extending to the chimney top, and a passive heat recovery device ( 2 ) located at the chimney top including a heat exchanger part ( 6 ) located in the chimney flue and having air inlet and air outlet ports ( 24, 26 ) communicating with the flow ducts, and including an air flow part ( 4 ) positioned on top of the chimney which replaces the chimney pot, and which exhausts stale air and draws in ambient air. The air flow part includes a turbine ventilator ( 18 ) for drawing out stale air, and a circular array of louvred air inlets ( 11, 12 ) for permitting inflow of fresh air.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a passive heat recovery and ventilation system, primarily for residential purposes. 
       BACKGROUND ART 
       [0002]    A wind driven passive heat recovery ventilator incorporated into living accommodation is disclosed in GB-A-2374661. It includes a rotatable air inlet/outlet head protruding through the roof, which is turned to face the wind by means of a wind vane. A heat exchanger within the building heats incoming air from the heat of exhausting air. Such a system has been incorporated into practical living accommodation, for example BedZED which is described in various publications, see for example: 
         [0000]    http://en.wikipedia.org/wiki/BedZED. 
         [0003]    BedZED includes rotatable wind cowls mounted on special purpose base units installed on the roof of a building. The building does not lose heat like conventional buildings because the building is designed to be airtight. Air can only move in and out through the wind cowls on the roof. Cool air coming in replaces warm air going out (the stack effect) and the air currents are separated within a heat exchanger. BedZED is a specially constructed building, and is not adapted for use in existing homes. 
         [0004]    Another system for new build homes is disclosed in DE-A-1982640, wherein a so-called chimney, which is not a chimney in the traditional sense, comprises a specially constructed shaft, which acts as a bus to interconnect the energy technology of the building. Such “chimney” includes a heat exchanger and electric fan ventilation box. 
         [0005]    Traditionally, homes, houses and other buildings have been constructed with a chimney, the term chimney, for the purposes of this specification, being intended to include a fireplace, chimney flue leading to the top of the chimney, where the is located a chimney pot. This traditional construction is not concerned with passive heat recovery issues. In a typical UK home 20% of all energy expenditure is from air leaks and required ventilation. Roughly, very much depending on the home, 7% of all household energy use is for required ventilation. For existing homes, there are fan driven products which act as heat recovery ventilators—see for example http://www.fantech.net/shr.pdf. The fan driven products consume a small amount of electricity all of the time. Because electricity is dirty in comparison to natural gas, the CO2 emissions for fan driven units may actually be worse than without. 
         [0006]    A system has been proposed making use of an existing chimney system in US Patent Application No. US 2003/0121513, which employs a fireplace as an element of the ventilation system. Electric blowers located at the fireplace force out exhaust air, and draw in fresh air. A separate ventilation channel conveys outdoor ambient air into the building interior. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the invention to provide a passive heating and ventilation system for fitting within an existing home having a traditional chimney. 
         [0008]    In a first aspect, the invention provides a method of converting an existing chimney of a building into a passive heat recovery and ventilator system, the method comprising:
       providing a fresh air outlet in the chimney flue and a stale air inlet in the chimney flue,   inserting first and second ducts within the chimney flue, the first duct extending from the fresh air outlet to the chimney top, and the second duct extending from the stale air inlet to the chimney top,   inserting a passive heat exchanger means in the chimney top and connected with said first and second ducts for transferring heat from stale outgoing air to fresh incoming air, and positioning an air flow means on top of the chimney and communicating with the heat exchanger for exhausting stale air and drawing in ambient air.       
 
         [0012]    The present invention in a second aspect provides a passive heat recovery system fitted within a chimney of a building, the system including inlet and outlet flow ducts fitted within the chimney flue, and extending to the chimney top, and a heat recovery device located at the chimney top including a heat exchanger part located in the chimney flue and having air inlet and air outlet ports communicating with said flow ducts, and including an air flow part positioned on top of the chimney, for exhausting stale air and for drawing in ambient air. 
         [0013]    The concept of the invention is to provide a small device, for residential applications, which is designed to fit within disused chimneys of existing houses. The device may be unitary, or formed as two parts which are connected together to form a single unit. The unit has a similar envelope to a chimney pot. Chimney pots for residences tend to be of a similar diameter, commonly between 20 and 30 cm, and communicating with a square chimney flue. The present invention is not limited to any specific dimension, but may be of any size, but however corresponding to the dimensions of the existing chimney. Having a chimney pot sized unit will minimize the need for structural reinforcement and potentially allow for installation on listed buildings. Planning permission may also be straight forward. 
         [0014]    The preferred unit includes a cylindrical air inlet/outlet part to be positioned on top of the chimney and replacing the conventional chimney pot. The air inlet comprises a manifold of cylindrical louvred air inlets extending around the periphery of the unit, so as to be responsive to air currents or wind from any direction. The air outlet preferably extends axially to the top of the unit. The air outlet may include a manifold of cylindrical louvred air outlets extending around the periphery of the unit, so that air can flow out regardless of wind direction. 
         [0015]    However, in a particularly preferred form, the manifold of cylindrical louvred air outlets comprising the air outlet is replaced by a turbine ventilator. Turbine ventilators are known devices—see for example http://www.atco.co.th/., and are wind driven devices with a large number of overlapping vane or scoop elements which rotate under wind pressure and operate to create a flow of air. For the purposes of the present invention, the term “turbine rotator” is intended to include all such devices, including turbine ventilators, Savonius turbines, Flettner ventilators, etc., that is wind driven devices having a plurality of vane or scoop elements which rotate under wind pressure and operate to create a flow of air. 
         [0016]    In the present invention, the turbine rotator acts, when rotated by wind to draw stale air out of the air outlet. Importantly, since wind flow is an irregular phenomenon, with fluctuations occurring over a period of the order of seconds, the turbine rotator is beneficial, since it continues to operate by reason of its inertia in periods of lack of wind, thereby creating a more reliable operation than prior art devices which use wind cowls, vanes etc. 
         [0017]    In a third aspect, the present invention provides a passive heat recovery and ventilation device for a passive heat recovery system fitted within a chimney of a building, the device including a heat exchanger part being dimensioned to fit within a chimney flue at the chimney top, and the device including an air flow part for positioning on top of the chimney, which includes an air outlet for exhausting stale air and an air inlet for drawing in fresh ambient air, wherein said air inlet comprises a plurality of louvred air inlets extending around the periphery of the airflow part, and communicating with an interior plenum, and said air outlet includes a turbine rotator mounted at the top of the air flow part, 
         [0018]    said air inlet and air outlet communicating with said heat exchanger part for transfer of heat between outlet and inlet air flows, and said heat exchanger part having air flow ports for connection to air flow ducts fitted within the chimney flue. 
         [0019]    Further, the turbine ventilator may be arranged to drive a fan in the air inlet duct so as to boost the pressure of air inflow. This pressure boost will be more constant than the irregular inflow pressure created by external wind acting on the louvers of the air inlet, since the combination of turbine rotator for stale air and fan for inlet air acts as a flywheel or smoothing capacitor, and continues to operate by reason of its inertia in periods of lack of wind, thereby creating a more reliable operation. This therefore is a further advantage of this form of the invention. 
         [0020]    It is known to combine a turbine ventilator with a fan to improve the evacuation of stale air, see for example the turbo fan vent described in U.S. Pat. No. 4,641,571. However it has not been previously proposed to combine a turbine ventilator with a fan, which act respectively on oppositely directed air flows. 
         [0021]    In a fourth aspect the present invention provides a ventilator device for an enclosed space, and including an air flow part having an exhaust flow path for exhausting stale air and an inlet flow path for drawing in ambient air, wherein the exhaust air flow path includes a turbine rotator, for positioning externally of the enclosed space, and arranged to draw out exhaust air under the influence of external wind, and wherein the turbine rotator is arranged to drive a fan located in the air inlet flow path, for boosting the pressure of the inflow of ambient air. 
         [0022]    Said fan may be of a centrifugal type, axial flow type, or mixed centrifugal/axial flow type. A Mixed flow fan, as the name implies, is a cross between a centrifugal and an axial fan. The advantages of a centrifugal fan and a mixed flow fan are that they may have similar flow characteristics to a turbine ventilator, and that they respond to air being driven into only one part of the fan from the louvers (that is the part exposed to wind flow), centrifugal and mixed flow fans acting like each blade is separate. The problem with using a centrifugal fan is that the output flow is radial and it preferably ought to be axial. Since there is limited radial space, an axial fan may be used; and this reduces manufacturing costs. For mixed flow fans, the benefits are 
         [0000]    1—Similar flow characteristics to a turbine ventilator (this makes it easier to balance the flow given a variable speed)
 
2—Axial flow
 
3—Higher pressure than an axial fan
 
4—Fairly insensitive to turbulence and variance in the input flow.
 
         [0023]    The preferred ventilator device of the invention also includes a heat exchanger device, located in the chimney flue, extending from the air flow part and terminating in air inlet and air outlet ports. The air inlet and outlet ports are coupled to respective inlet and outlet ducts that are mounted within the chimney flue and which extend to appropriate air inlets and outlets located within the home. The heat exchanger device functions to warm incoming air with the heat of outgoing air. Extractor fans may be located in the air inlet and/or outlet within the home to assist flow; nevertheless, the system of the invention remains a passive heat recovery and ventilation system. 
         [0024]    Installation is similar to lining an old chimney and installing a new chimney pot. The upgrade thus can be done in one day, requires only repair of existing structures and does not require a new hole in the roof. Importantly, in many jobs, no scaffolding would be required. While not a trivial cost, the cost will be low by construct standards. By being air driven, there is also no need for an electrician. As only one team need be involved, the problems of subcontractors are minimized and the installation really can be done in a reliable time frame. 
         [0025]    It is estimated the present invention may save roughly 5% of the average energy consumption of a UK home simply be replacing trickle vents and air bricks. By more thoroughly sealing the home, a further 5% to 10% of energy consumption could be reduced. While weatherproofing alone would be responsible for the further saving, having a heat recovery ventilator in accordance with the invention would encourage homeowners to weatherproof their homes as weatherproofing would not contribute to damp or a feeling of stuffiness. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    A preferred embodiment of the invention will now be described with reference to the accompanying drawings, wherein: 
           [0027]      FIG. 1  is a perspective view of a preferred passive heat recovery ventilator device according to the present invention; 
           [0028]      FIGS. 2 to 6  are schematic views illustrating the installation of the preferred passive heat recovery system in a disused chimney of a house, in accordance with the invention; 
           [0029]      FIG. 7  is a cross-sectional view of the device of  FIG. 1 ; 
           [0030]      FIG. 8  is a perspective view of the lower heat exchanger part of the two-part device; 
           [0031]      FIG. 9  is a perspective view of the upper air-flow part of the two-part device; 
           [0032]      FIG. 10  is a perspective view of a fan assembly of the upper air-flow part, comprising turbine ventilator and centrifugal fan; 
           [0033]      FIG. 11  is a plan view of the centrifugal fan of  FIG. 10 ; and 
           [0034]      FIG. 12  is a perspective view of an inner cowl frame of the upper air-flow part of the two-part device. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0035]    In a preferred embodiment, two ducts are fitted inside a disused chimney to allow for fresh air to enter into a building and stale air to be extracted from the building. The two flows are passed through a counter-flow heat exchanger mounted at the chimney top. The fresh air recovers heat from the stale air, thus reducing heating energy requirements while providing fresh air for ventilation. In air-conditioned situations, the fresh air will transfer heat to the stale air to reduce cooling energy requirements while providing fresh air. Fresh air enters and stale air exits the chimney through a wind flow device fitted on the top of the chimney. Typically, the unit will replace an existing chimney pot or cap. The wind flow device uses louvred deflectors and the natural energy of the wind to force fresh air into the mechanism. The louvers are fixed and direct wind coming from any horizontal direction into the mechanism. A combination of natural wind energy and the stack effect (where hot air rises) extracts the stale air. Wind is arranged to drive a turbine ventilator to create an upward flow. The upward flow creates a lower pressure area to draw out the stale air. Where needed a wind driven or electric propeller can be fitted to improve flow through the system. 
         [0036]    Referring to  FIG. 1 , heat recovery device  2  is of elongate form with a cylindrical upper module forming an air flow part  4  and a lower part forming a heat exchanger  6 . The device has an outer casing  8  of steel or plastic. The two parts  4 ,  6  are separated by a flange assembly  9 . 
         [0037]    Air flow part  4  include a cylindrical casing part  10  having vertical columns of louvers  11  providing arcuate apertures  12  spaced around the periphery of the casing, with adjacent columns separated by vertical wall sections  14 . The space within the casing comprises a fresh air plenum  16 . Since air inlets  12  extend around the entire periphery of the casing, air flow or wind from any direction will flow directly into the air inlets and enter the plenum  16 . Louvers  11  are downwardly angled, and create a pressure differential for incoming air. 
         [0038]    A stale air outlet flow path extends from heat exchanger  6  axially through airflow module  4  to the top of casing  10  and terminates in a turbine ventilator  18 . 
         [0039]    Heat exchanger device  6  includes a stack of parallel plates  20 , of thin metal or plastic, mounted within casing  8 . The upper ends of plates  20  are coupled to stale air outlet turbine ventilator  18  and fresh air plenum  16  at  21  so that spaces  22  between adjacent plates form flow paths for outgoing stale air. Interleaved spaces  24  between adjacent plates form flow paths for incoming fresh air, and are coupled to plenum  16 . Heat transfer occurs between the air flows by heat conduction through the plates. 
         [0040]    The lower ends of the plates are coupled to stale air inlet port  28  and fresh air outlet port  26 . Spaces  24  communicate with port  26  and spaces  22  communicate with port  28 . 
         [0041]    Referring now to  FIGS. 2 to 6 , the preferred method of installing a passive heat recovery system will be described. In  FIG. 2 , a chimney  40  in a residence is brick-built, and comprises a fire place  42  having a flue  44  extending to a chimney top  46 , having a chimney pot  48 . In order to convert this chimney to a heat recovery ventilator system, a first step is shown in  FIG. 3  wherein the chimney pot is removed together with surrounding mortar, and the chimney is swept if necessary. A channel  50  is cut into the flue for forming a stale air vent. A channel  52  is cut into the fireplace for fresh air; alternatively an existing air aperture to the chimney flue is adapted as a fresh air vent, and existing fireplace accessories are removed. 
         [0042]    In  FIGS. 4 and 5 , vertical metal ducts  60 ,  62  are positioned within the chimney flue and extend to the heat exchanger at the chimney top. A ducting end piece  64  is positioned within the fireplace  42 . At the chimney top  46 , heat exchanger  6  is inserted into the chimney flue  44 , and ports  26  and  28  are inserted into ducts  64 ,  66 . Connection is made as a force fit, but some form of bonding may be employed. As shown in  FIG. 6 , the air flow module  4  is then attached to heat exchanger  6 , and located on the chimney top. The heat exchanger and the air flow part are then secured to one another and fixed in position by flange assembly  9 , as described below. 
         [0043]    In modifications, as shown in  FIG. 6 , an air flow inlet blower fan  70  is provided at the air inlet  52  to augment flow, and an air extractor fan  72  is positioned at the end of an extension duct  74  for extracting stale air. 
         [0044]    Some form of shut off may be employed in the system so that the backpressure from inside the house does not force the fresh air out of the other fresh air inlets. The shut off can be very light and if the shut off fails, it will fail in an orientation where the predominant wind will continue to drive the system. 
         [0045]    Referring now to the specific construction of device  2 , in  FIGS. 1 ,  7  and  8 , the lower heat exchanger part  6  has end sections  26 ,  28  for fitting to ducts within a chimney flue, and which communicate with respective spaces  24 ,  22  within the heat exchanger  6  at a base region  75 , involving selective blocking of the spaces  22 ,  24 . An upper region  76  of the heat exchanger communicates with an inner stale air exit flow path  78 , and a surrounding fresh air inlet flow path  80 . The spaces  22 ,  24  of the heat exchanger are selectively blocked in region  76  to permit spaces  22  to communicate with inner flow path  78  and spaces  24  to communicate with outer fresh air path  80 . As best seen in  FIG. 8 , the top of part  6  has an outwardly extending flange  81  for mounting to the top of a chimney stack. 
         [0046]    Fresh air flow path  80  communicates with fresh air plenum  16  within air flow part  4 . Stale air flow exit flow path  78  continues in air flow part  4  to the top of part  4  where it communicates with turbine ventilator  18  mounted on top of part  4 . Turbine ventilator  18  comprises a large number of scoop shaped elements  84  arranged in a circle, and arranged in known manner to rotate in response to external wind from any direction. The ventilator has a long shaft  86  mounted on an upper bearing  88  and extending though flow path  78  to a lower bearing  90  where it is coupled with a fan assembly, ( FIGS. 7-11 ) comprising an inner flow regulator  92  mounted within air flow path  78 , and an outer centrifugal fan  94  mounted between fresh air plenum  16  and fresh air path  80 . 
         [0047]    As shown in  FIG. 12 , an inner cowl  100  within the air flow part  4  serves to define and separate the stale air flow path  78  and the fresh air plenum  16 . It provides a housing  102  for the fan assembly and a base flange  103  for registering with flange  81  of heat exchanger part  6 . Radial ribs or walls  14  provide supports for louvres  11 , which are fitted between the ribs  14 . The top part  106  of cowl unit  100  provides a flattened rim area  108  to which the turbine ventilator  18  is secured. As shown in  FIG. 8 , the top of part  6  has a circular raised portion  108  for registering with base  102  and coupling together the air flow paths of parts  4 ,  6 . 
         [0048]    Thus in operation, stale air flow upwardly from ducts,  62  into heat exchanger part  6 , where its heat is employed to heat incoming fresh air. The flow of stale air is regulated by the operation of inner fan  92  and turbine ventilator  18 , turbine ventilator  18  rotating in response to external wind. For fresh air inflowing through louver apertures  12 , the fan  94  operates to boost the pressure of the fresh air flow. Importantly, the combined fan assembly comprising turbine ventilator  82 , and fan  94  has an inertia, and acts as a flywheel or “smoothing capacitor” to ensure a reasonably constant air flow both of stale air and fresh air, in the circumstance where external wind flow may be irregular. Fan  94  acts to boost the inlet pressure, balance the flow between the exit and inlet streams and act as a capacitor to smooth the wind intermittency. While the fan  94  is extracting energy from the turbine ventilator, the wind pressure through louvers  12  is still the main flow driver. 
         [0049]    For installation, for the most part, the heat exchanger  6  and airflow device  4  are held in place via gravity. In addition, four anchors bolts installed in the chimney top may lock the units by affixing through apertures  110  in flanges  81 ,  103 . A sealing gasket may be compressed between the flanges. 
         [0050]    The airflow part  4  will either be made of metal or plastic. The heat exchanger of this second embodiment is made up of a series of channels, separated by aluminium plates. The casing of the heat exchanger is made up of three plastic sections screwed together. The plastic sections hold the aluminium plates. Another way to manufacture the heat exchanger would be to extrude the heat exchanger section out of one piece of aluminium and cap the ends with plastic or steel sections