Abstract:
A blower assembly of an HVAC system may include an electrically-conductive plating applied to an inner surface of a blower housing, a first electrode attached to the electrically-conductive plating at an inner wall of the blower housing via an electrically-conductive RTV silicone, and a second electrode attached to the electrically-conductive plating at an outer wall of the blower housing via an electrically-conductive RTV silicone. The first electrode may pass a current through the electrically-conductive plating of the blower housing to the second electrode that may act as an ohmic heater and provide a thermal energy discharge which may exchange heat with an airflow flowing through the blower housing as a result of operating the blower assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application No. 61/933,263 filed on Jan. 29, 2014 by Stephen Stewart Hancock, entitled “Method of Attaching Electrodes to Plated Thermoset Plastic Heated Blower Housing,” the disclosure of which is hereby incorporated by reference in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       REFERENCE TO A MICROFICHE APPENDIX 
       [0003]    Not applicable. 
       BACKGROUND 
       [0004]    Heating, ventilation, and/or air conditioning (HVAC) systems may generally comprise a blower assembly that may be selectively operated to deliver an airflow through an air handling unit (AHU) based on a demand for heating or cooling. In some applications, a blower assembly may be required to deliver a heated airflow to an air-conditioned space. In such applications, a blower assembly may require electrical resistance heating sources to heat an airflow exiting through the blower assembly in order to deliver the heated airflow to the air-conditioned space. 
       SUMMARY 
       [0005]    In some embodiments of the disclosure, a blower housing is disclosed as comprising an inner surface configured as an ohmic heater. 
         [0006]    In other embodiments of the disclosure, a HVAC system is disclosed as comprising an air handling unit comprising a blower assembly comprising an inner surface configured as an ohmic heater. 
         [0007]    In yet other embodiments of the disclosure, method of heating an airflow in an HVAC system is disclosed as comprising: providing a blower assembly in an air handling unit of an HVAC system, wherein the blower assembly comprises a blower housing having an inner surface configured as an ohmic heater; passing an airflow through the air handling unit; and exchanging heat from the ohmic heater to the airflow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description: 
           [0009]      FIG. 1  is an oblique view of an air handling unit according to an embodiment of the disclosure; 
           [0010]      FIG. 2  is an orthogonal view of the front of the air handling unit of  FIG. 1  according to an embodiment of the disclosure; 
           [0011]      FIG. 3  is a front-upper-right oblique view of the blower assembly of  FIG. 2  according to an embodiment of the disclosure; 
           [0012]      FIG. 4  is a cutaway side view of a blower housing comprising electrodes attached to an inner surface of the blower housing according to an embodiment of the disclosure; 
           [0013]      FIG. 5  is a detailed view the cutaway side view of the blower housing of  FIG. 5  comprising an electrically-conductive plating according to an embodiment of the disclosure; and 
           [0014]      FIG. 6  is a flowchart of a method of constructing an ohmic heater is shown according to an embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Referring now to  FIG. 1-2 , an oblique view, a front orthogonal view, and a partially exploded oblique view of an AHU  100  are shown, respectively, according to an embodiment of the disclosure. AHU  100  may generally be described as comprising a top side  106 , a bottom side  108 , a front side  110 , a back side  112 , a left side  114 , and a right side  116 . Such directional descriptions are meant to assist the reader in understanding the physical orientation of the various components parts of the AHU  100 , but such directional descriptions shall not be interpreted as limitations to the possible installation orientations and/or configurations of the AHU  100 . Additionally, the above-listed directional descriptions may be shown and/or labeled in the figures by attachment to various component parts of the AHU  100 . Attachment of directional descriptions at different locations or two different components of AHU  100  shall not be interpreted as indicating absolute locations of directional limits of the AHU  100 , but shall instead indicate that a plurality of shown and/or labeled directional descriptions in a single figure shall provide general directional orientation to the reader so that directionality may be easily followed amongst various figures. Furthermore, the component parts and/or assemblies of the AHU  100  may be described below as generally having top, bottom, front, back, left, and right sides which should be understood as being consistent in orientation with the top side  106 , bottom side  108 , front side  110 , back side  112 , left side  114 , and right side  116  of the AHU  100 . 
         [0016]    AHU  100  generally comprises an upper blower section  102  attached to a lower heat exchanger section  104 . The blower section  102  comprises a four-walled fluid duct that accepts fluid (air) through an open bottom side of the blower section  102  and allows exit of fluid through an open top side of the blower section  102 . In some embodiments, the exterior of the blower section  102  may generally comprise a blower section outer skin  118  and a blower section panel  120 . The blower section panel  120  is removable from the remainder of the blower section  102 , thereby allowing access to an interior of the blower section  102 . Similarly, the heat exchanger section  104  comprises a four-walled fluid duct that accepts fluid (air) from the air handler bottom  108  and passes the fluid from an open bottom side of the heat exchanger section  104  and allows exit of the fluid through an open top side of the heat exchanger section  104 . The exterior of the heat exchanger section  104  generally comprises a heat exchanger section outer skin  122  and a heat exchanger section panel  124 . The heat exchanger section panel  124  is removable from the remainder of the heat exchanger section  104 , thereby allowing access to an interior of the heat exchanger section  104 . 
         [0017]    The AHU  100  further comprises a plurality of selectively removable components. A refrigeration coil assembly  128  that may be removable from and carried by the heat exchanger section  104 . Similarly, the AHU  100  comprises a blower assembly  130  that may be removable from and carried by the blower section  102 . The AHU  100  may be considered fully assembled when the blower assembly  130  is carried within the blower section  102 , the refrigeration coil assembly  128  is carried within the heat exchanger section  104 , and when the blower section panel  120  and heat exchanger section panel  124  are suitably associated with the blower section outer skin  118  and the heat exchanger section outer skin  122 , respectively. When the AHU  100  is fully assembled, fluid (air) may generally follow a path through the AHU  100  along which the fluid enters through the bottom side  108  of the AHU  100 , successively encounters the refrigeration coil assembly  128  and the blower assembly  130 , and thereafter exits the AHU  100  through the top side  106  of the AHU  100 . In some embodiments, the AHU  100  may generally be configured as a pull-through type AHU, where the blower  130  may generally be configured to pull air through the refrigeration coil assembly  128 . 
         [0018]    Referring now to  FIG. 3 , an oblique view of the blower assembly  130  is shown from a front-upper-right viewpoint according to an embodiment of the disclosure. The blower assembly  130  generally comprises a motor  200  having a shaft  202  upon which an impeller  204  is mounted. The motor  200  is attached to a plurality of motor mounts  206  that holds the motor  200  in place relative to a left shell  208  of the blower assembly  130  and a right shell  210  of the blower assembly  130 . In some embodiments, the left shell  208  and the right shell  210  may be selectively joined together via integral snap features as well as retaining clips  212  and/or any other suitable fastening means. The snap features and the retaining clips  212  may be operated to optionally disconnect the left shell  208  from the right shell  210 . When joined, left shell  208  and the right shell  210  may be conceptualized as defining two distinct functional portions of the blower assembly  130  that generally form the blower housing  214 . 
         [0019]    A primary function of the blower housing  214  is to receive at least a portion of each of the motor  200  and the impeller  204  while also defining an intermediate air path that extends from each of the left air input port  216  of the blower assembly  130  and the right air input port  218  of the blower assembly  130 , along inner surfaces  224  of the left shell  208  and the right shell  210 , and exits through the blower output  220 . It is the shape of the interior of the blower housing  214  in combination with the movement of the impeller  204  that allows the optional intake of air through the left air input port  216  and the right air input port  218  and subsequent output of that air through the blower output  220 . Another functional portion of the blower assembly  130  may be referred to as the blower deck  222 . A first primary function of the blower deck  222  is to serve as a physical component used in mounting the entire blower assembly  130  within and relative to the blower section  102 . A second primary function of the blower deck  222  is to serve as a substantial air pressure barrier between the portion of the interior of the blower section  102  that houses the blower assembly  130  and the interior of the heat exchanger section  104 . 
         [0020]    In some embodiments, a portion of the blower assembly  130  may be configured as an ohmic heating device. As will be explained later in more detail, the inner surface  224  of the left shell  208  and/or the right shell  210  of the blower assembly  130  may comprise an electrically-conductive plating  225 . Furthermore, in order to pass a current through the electrically-conductive plating  225  on the inner surface  224  of the left shell  208  and/or the right shell  210 , the blower assembly  130  may comprise an outer electrode  248  and an inner electrode  250 . In some embodiments, the outer electrode  248  may be attached to the electrically-conductive plating  225  along a larger diameter portion of a shell  208 ,  210 , while the inner electrode  250  may be attached to the electrically-conductive plating  225  along a smaller diameter portion of a shell  208 ,  210 . Furthermore, in some embodiments, where the ohmic heating provided by passing a current from one electrode  248 ,  250  to the other electrode  248 ,  250  through the electrically-conductive plating  225  on the inner surface provides sufficient heat to an airflow through the AHU  100 , heater assembly  126  may not be required. 
         [0021]    Referring now to  FIG. 4 , a cutaway side view of a blower housing  300  comprising electrodes  308 ,  312  attached to an inner surface  314  of the blower housing  300  is shown according to an embodiment of the disclosure. Blower housing  300  may generally be substantially similar to blower housing  214  of  FIG. 4  and may comprise a left shell and a right shell that is substantially similar to the left shell  208  and the right shell  210  of blower housing  214  of  FIG. 4 . Blower housing  300  may also comprise an outer wall  302  and an inner wall  304 . In some embodiments, blower housing  300  may also comprise an inner surface  314  that may be substantially similar to inner surface  224  of  FIG. 4  and that may generally extend from the outer wall  302  to the inner wall  304 . Additionally, blower housing  300  may comprise a blower output  316  that may be substantially similar to blower output  220  of  FIG. 4 . In some embodiments, blower housing  300  may be a component of the blower assembly  130  shown in  FIGS. 2-4 . 
         [0022]    Generally, the blower housing  300  may be formed from a thermosetting plastic. However, in some embodiments, blower housing  300  may be formed from a composite material and/or any other suitable material. The inner surface  314  of the blower housing  300  may generally comprise an electrically-conductive plating  320  applied thereto. In some embodiments, the electrically-conductive plating  320  applied to the inner surface  314  of the blower housing  300  may comprise stainless steel. In some embodiments, the electrically-conductive plating  320  may comprise aluminum, copper, titanium, and/or any other suitable electrically-conductive material that may adhere to the inner surface  314  of the blower housing  300 . The electrically-conductive plating  320  may generally be applied to the inner surface  314  as a thin, film-like layer. In some embodiments, the electrically-conductive plating  320  of the inner surface  314  of the blower housing  300  may comprise a thickness of at least about 5 Angstroms, about 6 Angstroms, about 7 Angstroms, about 8 Angstroms, about 9 Angstroms, about 10 Angstroms, about 11 Angstroms, about 12 Angstroms, about 13 Angstroms, about 14 Angstroms, and about 15 Angstroms. It will be appreciated that the application of a thin electrically-conductive plating  320  may provide a resistance to electrical current that may generally cause the electrically-conductive plating  320  to heat up. Accordingly, in some embodiments, the thickness of the plating may be selected based on the amount of heat required. 
         [0023]    Blower housing  300  may generally comprise an outer electrode  308  and an inner electrode  312 . The electrodes  308 ,  312  may generally comprise a relatively low electrical resistance and may generally be configured to distribute an electrical current through the electrically-conductive plating  320  of the inner surface  314 . In some embodiments, the electrodes  308 ,  312  may enter the blower housing  300  through the blower output  316 . In other embodiments, however, the electrodes  308 ,  312  may enter the blower housing  300  through a hole in the outer wall  302  and/or any other suitable aperture in the blower housing  300  that allows the electrodes  308 ,  312  to be attached to the outer wall  302  and the inner wall  304 , respectively. Generally, the electrodes  308 ,  312  may be flexible. Accordingly, in some embodiments, the outer electrode  308  may be attached peripherally to the inner surface  314  of the blower housing  300  at the outer wall  302  and may substantially conform to a contour of the outer wall  302 , while the inner electrode may be attached to the inner surface  314  of the blower housing  300  at the inner wall  312  and may substantially conform to a contour of the inner wall  304 . In some embodiments, the outer electrode  308  may be attached to the inner surface  314  at the outer wall  302  so that a substantial portion of outer electrode  308  attached to the inner surface  314  may be in electrical connection with the inner surface  314  of the blower housing  300 . Additionally, in some embodiments, the inner electrode  312  may be attached to the inner surface  314  at the inner wall  304  so that a substantial portion of inner electrode  312  attached to the inner surface  314  may be in electrical connection with the inner surface  314  of the blower housing  300 . In some embodiments, substantially the entire portion of the electrodes  308 ,  312  attached to the inner surface  314  may be in substantial electrical connection with inner surface  314  of the blower housing  300 . 
         [0024]    Most generally, the outer electrode  308  may be attached to the inner surface  314  at the outer wall  302  by an outer adhesive layer  306 , while the inner electrode  312  may be attached to the inner surface  314  at the inner wall  304  by an inner adhesive layer  310 . The adhesive layers  306 ,  310  may generally comprise an electrically-conductive adhesive configured to adhere to a majority of metallic materials and/or typical substrates, including, but not limited to, the thin, electrically-conductive plating  320  of the inner surface  314  of the blower housing  300 . In some embodiments, the adhesive layers  306 ,  310  may comprise an electrically-conductive silicone that is a room-temperature vulcanizing (RTV) silicone. In some embodiments, the adhesive layers  306 ,  310  may comprise RTV silicone that is impregnated with graphite and/or nickel which may provide the electrical-conductive properties to the RTV silicone. 
         [0025]    Because the electrodes  308 ,  312  may generally conform to the contour of the inner surface  314  and/or the electrically-conductive plating  320  at the outer wall  302  and inner wall  304 , respectively, the adhesive layers  306 ,  310  may be configured to remain pliable, even after curing. In some embodiments, the adhesive layers  306 ,  310  may also be configured to withstand high thermal stresses due to the current passing through the layers  306 ,  310 . Additionally, in some embodiments, attaching the electrodes  308 ,  312  to the electrically-conductive plating  320  of the inner surface  314  via the adhesive layers  306 ,  310  as opposed to directly attaching the electrodes  306 ,  310  to the electrically-conductive plating  320  of the inner surface  314  may prevent the electrodes  308 ,  312  from shearing the electrically-conductive plating  320  of the inner surface  314  due to excessive strain from the thermal expansion differential between the hot conductive plating  320  and the relatively cool electrodes  308 , 312 . In operation, and most generally, the blower housing  300  may be configured so that a current may flow from the so-called “hot” electrode through the electrically-conductive plating  320  of the inner surface  314  to the so-called “ground” electrode. In some embodiments, the inner electrode  312  may comprise the so-called “hot” electrode, while the outer electrode  312  may comprise the so-called “ground” electrode. In such embodiments, the current may generally flow from the inner electrode  312  through the electrically-conductive plating  320  of the inner surface  314  to the outer electrode  308 . In alternative embodiments, however, the outer electrode  308  may comprise the so-called “hot” electrode, while the inner electrode  312  may comprise the so-called “ground” electrode. In such alternative embodiments, the current may generally flow from the outer electrode  308  through the electrically-conductive plating  320  of the inner surface  314  to the inner electrode  312 . As current is passed through the electrically-conductive plating  320  of the inner surface  314 , the current may cause the electrically-conductive plating  320  of the inner surface  314  to heat up. The heating up of the electrically-conductive plating  320  of the inner surface  314  may generally be referred to as ohmic heating. 
         [0026]    The outer electrode  308  and the inner electrode  312  may generally be configured such that a substantial portion of each of the outer electrode  308  and the inner electrode  312  attached to the inner surface  314  may be in electrical connection with the electrically-conductive plating  320  of the inner surface  314 . In some embodiments, substantially all of the outer electrode  308  and the inner electrode  312  attached to the inner surface  314  via the outer adhesive layer  306  and the inner adhesive layer  310 , respectively, may be in electrical connection with the electrically-conductive plating  320  of the inner surface  314 . Attaching the electrodes  308 ,  312  substantially all the way around the walls  302 ,  304 , respectively, may generally distribute the current passing from one of the electrodes  308 ,  312 , through the electrically-conductive plating  320 , and to the other electrode  308 ,  312 , throughout the electrically-conductive plating  320  of the inner surface  314  of the blower housing  300 . In some embodiments, distributing the current throughout the electrically-conductive plating  320  of the inner surface  314  by attaching the electrodes  308 ,  312  to the inner surface  314  substantially all the way around the outer wall  302  and inner wall  304 , respectively, may produce a substantially isothermal temperature across the electrically-conductive plating  320  of the inner surface  314 . Additionally, in some embodiments, distributing the current throughout the electrically-conductive plating  320  of the inner surface  314  by attaching the electrodes  308 ,  312  to the inner surface  314  substantially all the way around the outer wall  302  and inner wall  304 , respectively, may also prevent current from concentrating at a single electrical connection point to the inner surface  314 , which may produce excessive local temperatures near the connections and cause damage and/or failure of the respective electrical connections to the electrically-conductive plating  320 . 
         [0027]    Because blower housing  300  may be substantially similar to blower housing  214  in  FIG. 4 , blower housing  300  may substantially similarly define an intermediate air path that extends from an input port  318  that may be substantially similar to left air input port  216  and/or right air input port  218  of blower assembly  224 , along inner surface  314 , and exits the blower output  316 . As an airflow is passed through the intermediate air path of the blower housing  300 , the electrically-conductive plating  320  of the inner surface  314  may transfer at least a portion of the heat generated through ohmic heating by the current passing through the electrically-conductive plating  320  of the inner surface  314  to the airflow. In some embodiments, an ambient airflow entering the blower housing  300  may cool a motor of a blower, such as motor  200  of blower  130  in  FIG. 4 , while the blower housing  300  may be configured to heat the airflow to provide electric heat downstream of the blower  130  shown in  FIGS. 2-4 . 
         [0028]    Most generally, the current flow through the electrically-conductive plating  320  of the inner surface  314  may cause the electrically-conductive plating  320  to heat up in accordance with the equation P=I 2 R, where P is the power measured in Watts, I is the current measured in Amperes, and R is the resistance measured in Ohms. Alternatively, the current flow through the electrically-conductive plating  320  of the inner surface  314  may cause the electrically-conductive plating  320  to heat up in accordance with the equation P=V 2 /R, where P is the power measured in Watts, V is the voltage measured in Volts, and R is the resistance measured in Ohms. For example, in some embodiments, supplying a voltage of about 230 V and a current of about 40 Amperes may result in about 9.2 kW of heat produced by the blower housing  300  at 5.75 Ohms of resistance. 
         [0029]    Referring now to  FIG. 5 , a detailed view of the cutaway side view of the blower housing  300  of  FIG. 4  comprising an electrically-conductive plating  320  is shown according to an embodiment of the disclosure. As shown, the outer wall  302  comprises an inner surface  314  that is plated with a thin, electrically-conductive plating  320 . Additionally, the outer electrode  308  may generally be attached to and substantially electrically connected along the outer wall  302  to the electrically-conductive plating  320  of the inner surface  314  via the outer adhesive layer  306 . Additionally, the outer electrode  308  may conform to the profile of the outer wall  302 , the electrically-conductive plating  320 , and/or the outer adhesive layer  306 . It will be appreciated that while the outer wall  302 , outer adhesive layer  306 , and outer electrode  308  are shown in Detail A, the inner wall  304 , inner adhesive layer  310 , and inner electrode  312  may configured in substantially the same manner, respectively. 
         [0030]    Referring now to  FIG. 6 , a flowchart of a method  400  of constructing an ohmic heater is shown according to an embodiment of the disclosure. The method  400  may begin at block  402  by providing a blower housing  300 . The method  400  may continue at block  404  by applying a thin, electrically-conductive plating to an inner surface of the blower housing. In some embodiments, the thickness of the electrically-conductive plating may be selected as a function of the heat required to be supplied. In some embodiments, the electrically-conductive plating may comprise stainless steel. The method  400  may continue at block  406  by applying an adhesive to a first adhesive section and a second adhesive section of the inner surface of the blower housing. In some embodiments, the adhesive may comprise electrically-conductive RTV silicone. In some embodiments, the first adhesive section may comprise an inner surface at the inner wall of the blower housing, and the second adhesive section may comprise an inner surface at the outer wall of the blower housing. The method  400  may conclude at block  408  by attaching a first electrode to the first adhesive section and a second electrode to the second adhesive section. 
         [0031]    At least one embodiment is disclosed and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, R l , and an upper limit, R u , is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=R l +k*(R u −R l ), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Unless otherwise stated, the term “about” shall mean plus or minus 10 percent of the subsequent value. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of the term “optionally” with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention.