Abstract:
An energy recovery ventilator cabinet containing a plurality of enthalpy wheels. The enthalpy wheels are substantially perpendicular to a stream of forced air, allowing the air to pass through the wheels. The enthalpy wheels are also disposed such that portions overlap, allowing multiple enthalpy wheels to be disposed in a smaller space than if the enthalpy wheels were placed side by side. This arrangement has led to energy recovery effectiveness similar to that obtained by a larger, single enthalpy wheel, but has the advantage of using less space.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is related to U.S. patent application Ser. No. 13/274,562 by McKie et al., entitled, “A TRANSITION MODULE FOR AN ENERGY RECOVERY VENTILATOR UNIT” (“Appl-1”); U.S. patent application Ser. No. 13/274,587 by McKie et al., entitled, “SENSOR MOUNTING PANEL FOR AN ENERGY RECOVERY VENTILATOR UNIT” (“APPL-2”); and U.S. patent application Ser. No. 13/274,629, by McKie et al., entitled, “DESIGN LAYOUT FOR AN ENERGY RECOVERY VENTILATOR SYSTEM” (“Appl-3”), which are all filed on the same date as the present application, and, which are incorporated herein by reference in their entirety. One or more of the above applications may describe embodiments of Energy Recovery Ventilator Units and components thereof that may be suitable for making and/or use in some of the embodiments described herein. 
     TECHNICAL FIELD 
     This application is directed, in general, to space conditioning systems and methods for conditioning the temperature and humidity of an enclosed space using an energy recovery ventilator. 
     BACKGROUND 
     Energy recovery ventilator units are often used in space conditioning systems to maintain air quality while minimizing energy losses. Currently, there is a lack of energy recovery ventilator units that can provide a high fresh-air proportion without using a single large diameter energy exchange enthalpy wheel. A large diameter enthalpy wheel adds to the foot-print, size, weight, and cost of the cabinet to house a large wheel. Consequently, existing energy recovery ventilator units can have poor compatibility with smaller (e.g., less than 20 tons) roof-top air handling units. 
     SUMMARY 
     One embodiment of the present disclosure is an energy recovery ventilator unit. The unit comprises a cabinet and a plurality of enthalpy wheels mounted in the cabinet. Major surfaces of each of the enthalpy wheels are substantially separated from each other and substantially perpendicular to a direction of primary forced-air intake into the cabinet. The major surface of one of the enthalpy wheels substantially overlaps, in the direction of primary forced-air intake, with the major surface of at least one of the other enthalpy wheels. 
     Another embodiment of the present disclosure is a method of assembling an energy recovery ventilator unit. The method comprises providing a cabinet and mounting a plurality of enthalpy wheels in the cabinet. Major surfaces of each of the enthalpy wheels are substantially perpendicular to a direction of primary forced-air intake into the cabinet. The major surface of one of the enthalpy wheels substantially overlaps, in the direction of primary forced-air intake, with the major surface of at least one of the other enthalpy wheels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  presents a three-dimensional view of an example energy recovery ventilator unit of the disclosure; 
         FIG. 2  presents a plan view of the example energy recovery ventilator unit presented in  FIG. 1 , along view line  2  as shown  FIG. 1 ; 
         FIG. 3  presents a side of a selected portion the example energy recovery ventilator unit presented in  FIG. 1 , along view line  3  as shown  FIG. 1 ; 
         FIG. 4  presents a plan view of an alternative example energy recovery ventilator unit that is analogous to the view in presented in  FIG. 2 , but having have more than two wheels; 
         FIG. 5  presents a plan view of another alternative example energy recovery ventilator unit that is analogous to the view in presented in  FIG. 2 , but having have more than two wheels; and 
         FIG. 6  presents a flow diagram of an example method of manufacturing an energy recovery ventilator unit of the disclosure, including any of the example embodiments discussed in the context of  FIGS. 1-5 . 
     
    
    
     DETAILED DESCRIPTION 
     The term, “or,” as used herein, refers to a non-exclusive or, unless otherwise indicated. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. 
     One embodiment of the present disclosure is an energy recovery ventilator unit.  FIG. 1  presents a three-dimensional view of an example energy recovery ventilator unit  100  of the disclosure.  FIG. 2  presents a plan view of the example energy recovery ventilator unit  100  presented in  FIG. 1 , along view line  2  as shown  FIG. 1 .  FIG. 3  presents a side of a selected portion the example energy recovery ventilator unit  100  presented in  FIG. 1 , along view line  3  as shown  FIG. 1 . Some exterior portions of a cabinet  105  are not shown in these figures so that the features within the cabinet  105  can be more clearly depicted. 
     As illustrated in  FIG. 1 , the energy recovery ventilator unit  100  comprises a cabinet  105  and a plurality of enthalpy wheels  110 ,  112  mounted in the cabinet  105 , The wheels  110 ,  112  are mounted such that major surfaces  115 ,  117  of each of the enthalpy wheels  110 ,  112  are substantially perpendicular to a direction  120  of primary forced-air intake into the cabinet  105  (e.g., via an intake blower  125 ), and, the major surface  115  of one of the enthalpy wheels (e.g., one of surface  115  or surface  117 , of one of the wheels  110 ,  115 ) substantially overlaps, in the direction  120  of primary forced-air intake, with the major surface of at least one of the other enthalpy wheels (e.g., the other one of the surfaces  115 ,  117  of the other of wheels  110 ,  112 ). 
     Mounting the wheels  110 ,  112  so that their major surfaces  115 ,  117  substantially overlap facilitates housing the wheels in a smaller-sized cabinet  105  than otherwise possible when using a single wheel, or, when using plurality of side-by-side wheels. It is surprising that such a configuration can be used to obtain desirable levels of energy recovery because of the perception that off-setting and overlapping the wheels in this fashion would have negative effects of airflow distribution on energy transfer. For instance, certain commercial suppliers of enthalpy wheels supplier recommend a maximum overlap of no more that 15 percent to avoid negative effects of air-flow distribution on energy transfer. 
     As part of the present disclosure, however, it was discovered that by substantially separating the enthalpy wheels  110 ,  112  from each other, negative air-flow distribution effects can be minimized, resulting in little to no loss in energy recovery effectiveness as compared to unit with a single wheel, or of side-by-side wheels, having major surfaces of comparable total area. 
     An additional benefit is that in some cases, the total cost of the plurality of the smaller-diameter wheels  110 ,  112  can be less than the cost of a single large wheel. Moreover, the individual weight of smaller-diameter wheels can be low enough that that single installer can pick up and move the wheel around, thereby reducing the cost of servicing or installing the unit  100 . Also, the use of a plurality of wheels  110 ,  112  may provide a redundancy of function. For instance, if one wheel becomes inoperable, one or more of the other wheels can still have some functionality, which may not the case when using a unit with a single wheel. 
     For the purposes of the present disclosure, the term substantially separated from each other, as used herein, means that the opposing major surface areas of two adjacent wheels  110 ,  112  are separated by a distance  205  ( FIG. 2 ), in the direction  120  of primary air intake, that is far enough apart that a desired airflow rate through the cabinet  105  (e.g., about 4000 cubic feet per minute, in some embodiments) can be achieved without have to expend more than 125 percent of the power to achieve the same airflow rate for a cabinet design having a single wheel, or side-by-side wheel, configurations with major surfaces of comparable total area. One skilled in the art, based on the present disclosure, would appreciate that the specific distance  205  separating two adjacent wheels  110 ,  112  would depend on the extent of overlap between the wheels  110 ,  112  and the desired airflow rate. 
     In some embodiments, the enthalpy wheels  110 ,  112  are separated, in the direction  120  of primary forced-air intake, by the distance  205  equal to or greater than one-third of a diameter  210  of two adjacent ones of the enthalpy wheels  110 ,  112 . For example, in some embodiments of the unit  100 , two of the enthalpy wheels  110 ,  112  have a same diameter  210  of about 35 inches. In such cases, the two wheels  110 ,  112  can be separated by a distance  205  of about 12 or more inches. In embodiments where there are two wheels of different diameters, then the separation distance  205  can be equal to or greater than the about one-third of the smallest diameter wheel of the two adjacent wheels. 
     For the purposes of the present disclosure, the term substantially perpendicular to the direction of primary forced-air intake, as used herein, means that the average direction  120  of forced air from the intake blower  125  in the cabinet  105  forms an angle  215  with respect to the major surfaces  115 ,  117  that equals about 90 degrees±20 degrees. 
     For the purposes of the present disclosure, the term substantially overlap, as used herein, means that there is greater than 15 percent overlap between either of the major surfaces  115 ,  117  of adjacent pairs of the enthalpy wheels  110 ,  112  which overlap in the direction  120  of forced airflow. For instance, as shown in  FIG. 3 , if the total area of the major surfaces  115 ,  117  of two same-sized wheels each equals  100  arbitrary area units of measure, then more than 15 area units of measure are in an overlap zone  310  for either of the wheels  110 ,  112 . For instance, in some embodiments of the unit  100 , the major surface areas  115 ,  117  of two of the enthalpy wheels  110 ,  112  overlap by up to about 50 percent of the total area of either of the enthalpy wheel&#39;s major surfaces  115 ,  117 . Moreover in some such embodiments, the separation distance  205  can be equal to or greater than one-third of a diameter  210  of same-sized wheels  110 ,  112 . 
     As illustrated in  FIG. 1 , in some embodiments, the major surfaces  115 ,  117  of each of the enthalpy wheels  110 ,  112  are vertically oriented in the cabinet  105 , and, the wheels  110 ,  112  are arranged substantially parallel to each other. For instance, the major surfaces  115 ,  117  of the wheels  110 ,  112  are substantially perpendicular (e.g., forming an angle  130  of 90±10) with respect to sidewalls  135 ,  137  of the cabinet  105 . 
     Having such a vertical orientation and parallel arrangement can facilitate removal of the enthalpy wheels  110 ,  112 , from the cabinet  105  for cleaning or replacement, e.g., by sliding the wheels  110 ,  112  out of the cabinet (e.g., by sliding the each wheel through one or more service doors  132 ), without having to lift the wheels  110 ,  112  or to remove more than one wheel at a time, such as the case for certain tilt-mounted wheel configurations (e.g., a so-called “V-bank” configuration) or side-by-side configurations. Additionally, the casings  140  used to hold the vertically orientated and parallel arranged wheels  110 ,  112  can have less parts and be easier to manufacture than assemblies that hold wheels in a tilted configuration in a cabinet. 
     As further illustrated in  FIGS. 1 and 2 , in some embodiments each of the enthalpy wheels  110 ,  112  are housed in their own casings  140 , and, a partitioning wall  145  connects the casings  140  together to form an air-tight and moisture-tight seal in the cabinet  105 . That is, the partitioning wall  145  is configured to be sealed such that air and moisture can only travel through the enthalpy wheels  110 ,  112  from one zone (e.g. an intake zone  150 ) to another zone (e.g., a supply zone  155 ), in the cabinet  105 . As illustrated in  FIG. 2 , in some cases, the enthalpy wheels  110 ,  112 , and the partitioning wall  145 , after being connected together through the wall  145 , form a Z-shaped, or transposed Z-shaped, pattern that is recognizable from certain overhead views of the unit  100 . However, embodiments of the unit  100  are not necessarily limited to having such patterns. 
       FIG. 4  presents a plan view of an alternative example energy recovery ventilator unit  100  that is analogous to the view presented in  FIG. 2 , but having more than two wheels. As illustrated in  FIG. 4  the unit  100  has three enthalpy wheels  110 ,  112 ,  410 . The major surface areas (e.g., surface area  415 ), of one of the enthalpy wheels (e.g., wheel  410 ) substantially overlaps with major surface areas  115 ,  117  of two other ones of the enthalpy wheels  110 ,  112 , in the direction  120  of forced-air intake. In such embodiments the partitioning wall  140  could have two separate parts: a first part  420  connecting the first wheel  110  and the third wheel  410 , and a second part  425  connecting the second wheel  112  and the third wheel  410 . As illustrated in  FIG. 4 , not all of wheels (e.g., the two side-by-side wheels  110 ,  112 ) have to overlap with each other, 
     In some cases, to help reduce the size of cabinet  105  it can be advantageous for all three of the wheels  110 ,  112 ,  410  to overlap with each other. For instance, as illustrated in  FIG. 5 , the unit  100  could have three wheels  110 ,  112 ,  510 , and, major surfaces  115 ,  117 ,  515  of all three wheels  110 ,  112 ,  510  overlap with each other. Adjacent pairs of the enthalpy wheels (e.g., wheels  110 ,  112 , and, wheels  112 ,  510 ) are connected to each other by two separate parts  520 ,  525  of the partitioning wall  140 . 
     As noted above, mounting the enthalpy wheels so that their major surfaces substantially overlap facilitates the use of smaller-sized cabinets. For example as illustrated in  FIG. 2 , in some embodiments, a width  220  of the cabinet  105  is less than two-thirds of the sum of diameters  210  of the enthalpy wheels  110 ,  112 . Consider, e.g., an embodiment of the unit  100  having two enthalpy wheels  110 ,  112  and the major surfaces  115 ,  117  of the two wheels  110 ,  112  overlap by about 50 percent. In such embodiments, the cabinet  105  can have a width  220  that is about 60 percent of the sum of the diameters  210  of the two wheels  110 ,  112 . For instance, when the wheels  110 ,  112  both have a diameter  210  of about 35 inches, then the cabinet&#39;s width  220  can be about 47 inches. This can be a substantial reduction in cabinet width compared to some single wheel configurations, such as, e.g., a single 44-inch diameter wheel mounted in a 70-inch wide cabinet. 
     Mounting the enthalpy wheels so that their major surfaces substantially overlap with each other can also facilitate the placement of a secondary intake opening  160  to the supply zone  155  of the cabinet  105 . Under certain favorable ambient outdoor conditions, the secondary intake opening  160  can provide free-cooling to a conditioned space without having to expended energy to force air through the enthalpy wheel  110 ,  112  via the intake blower  125 . Space for the secondary intake opening  160  in the supply zone  155  can be created, without increasing the cabinet&#39;s size, by mounting one wheel  110  to an opposite sidewall  135  of the cabinet  105  as the sidewall  137  that the secondary intake opening  160  is located in. Such a configuration advantageously avoids having to increase the vertical height or horizontal width of the cabinet  105  to accommodate the opening  160 . 
     The secondary intake opening  160  is configured to provide a controlled delivery of outside air to the supply zone  155 . For example, the secondary opening  160  can be covered with an air control assembly  164  (e.g., including baffles or other adjustable air-restriction structure) configured to regulate the amount of air allowed though the secondary intake opening  160 . 
     In some embodiments, as shown in  FIG. 1 , the intake blower  125  can be located on one end of the cabinet  105 , and, a return blower  170  can be located on an opposite end  175  of the cabinet  105 . Such a configuration can facilitate efficient air flow through the unit  100 , as well as facilitate the placement of the secondary intake opening  160  in a sidewall  137  of the cabinet  105 . 
     As further illustrated in  FIGS. 1-2 , some embodiments of the unit  100  further include a secondary return exhaust opening  180  that enters into a return zone  182  of the cabinet  105 . The secondary return exhaust opening  180  allow return air from a conditioned space to be expelled from the unit without having to expended energy to force air through the enthalpy wheel  110 ,  112  via the return blower  170 . The secondary return exhaust opening  180  can be covered with an air control assembly  184  (e.g., baffles or other adjustable air-restriction mechanisms) configured to regulate the amount of air allowed though the secondary exhaust opening  180 . 
     In some embodiments to facilitate servicing, the secondary intake opening  160  and secondary return exhaust opening  180  are formed in the same sidewall  137  of the cabinet  105 . 
     Another embodiment of the present disclosure is a method of manufacturing an energy recovery ventilator unit, such as any of the units  100  discussed in the context of  FIGS. 1-5 .  FIG. 6  presents a flow diagram of an example method  600  of manufacture. 
     With continuing reference to  FIGS. 1-5  throughout, the example method  600  comprises a step  610  of providing a cabinet  105 . For example, steel walls  135 ,  137  can be covered with a thermal insulation material and coupled together (e.g., via welds or fasteners) to form an airtight- and moisture-tight seal, as part of providing the cabinet in step  610 . 
     The method  600  further comprises a step  620  of mounting a plurality of enthalpy wheels  110 ,  112  in the cabinet  105  such that major surfaces  115 ,  117  of each of the enthalpy wheels  110 ,  112  are substantially perpendicular to a direction  120  of primary forced-air intake into the cabinet  105 . Additionally, the mounting is such that the major surface  115 ,  117  of one of the enthalpy wheels  110 ,  112  substantially overlaps, in the direction  120  of primary forced-air intake, with the major surface  115 ,  117  of at least one the other enthalpy wheels  115 ,  117 . 
     In certain embodiments of the method  600 , mounting the wheels  110 ,  112  in step  620 , can include a step  630  of housing each of the wheels in their own casing  140 . In some embodiments, the wheels  110 ,  112  can be housed in their own casings  140  before being mounted in the cabinet  105 . That is, the wheel  110  and casing  140  are together mounted in the cabinet  105  as part of step  620 . In other cases, the wheels  110 ,  112  can be housed in a casing  140  that is already installed in the cabinet  105 . That is, the wheel is separately mounted in the cabinet  105 . 
     In some embodiments of the method  600 , mounting the enthalpy wheels  110 ,  112  in step  620  further includes a step  635  of connecting a partitioning wall  145  between the casings  140  to form an air-tight and moisture-tight seal. 
     In some embodiments of the method  600 , the mounting step  620  can include a step  640  of vertically orienting the major surfaces  115 ,  117  of each of the enthalpy wheels  110 ,  112  with respect to a base  190  (e.g., a planar base platform) of the unit  100 . 
     In some embodiments of the method  600 , mounting the enthalpy wheels  110 ,  112  in step  620 , can further include a step  645  of independently sliding the enthalpy wheels  110 ,  112  into the cabinet  105 . That is, any of the wheels  110 ,  112  can slide into or out of the cabinet  105  without having to remove or move any of the other wheels. To facilitate sliding, in some cases, the casings  140  housing each wheel  110 ,  112  can have support wheels or rollers. 
     Some embodiments of the method  600  can further include a step  650  of mounting an air control assembly  164  to a secondary intake opening  160  formed in the cabinet  105 , wherein the secondary intake opening  160  is configured to provide a controlled delivery of outside air to a supply zone  155  of the cabinet  105  which bypasses the enthalpy wheels  110 ,  112 . 
     Those skilled in the art to which this application relates will appreciate that other and further additions, deletions, substitutions and modifications may be made to the described embodiments.