Patent Application
20220412601
The present description relates generally to rooftop air conditioning (AC) units, and more particularly to an energy recovery ventilator (ERV) system for a modified rooftop AC unit.
There is a need to recover energy from the conditioned air leaving the building (whether it be heating or cooling), for example, via the rooftop AC unit. However, conventional rooftop AC units may lack the space necessary to incorporate ERV systems. This makes traditional retrofits difficult and may require the movement or resizing of various components or other layout changes.
According to one aspect of the invention, a rooftop AC unit includes a cabinet, an energy recovery wheel which is rotatably mounted within the cabinet, and a controller. The energy recovery wheel is configured to transfer heat between an outdoor air stream and a return air stream when rotated into an operational position and is further configured not to transfer heat between the outdoor air stream and the return air stream when rotated into a bypass position. The controller is configured to select the operational position of the energy recovery wheel and an operational mode of the energy recovery wheel.
According to another aspect of the invention, an ERV system for a rooftop AC unit includes an energy recovery wheel which is rotatably mounted within the cabinet and a controller. The rooftop AC unit includes a cabinet. The energy recovery wheel is configured to transfer heat between an outdoor air stream and a return air stream when rotated into an operational position and is further configured not to transfer heat between the outdoor air stream and the return air stream when rotated into a bypass position. The controller is configured to select the operational position of the energy recovery wheel and an operational mode of the energy recovery wheel.
According to yet another aspect of the invention, a method of operating a rooftop AC unit which includes an ERV system includes configuring a plurality of dampers to direct a flow of outdoor air and a flow of return air through the ERV system. A controller selects an operational mode of an energy recovery wheel. The energy recovery wheel rotates about a positional axis of rotation to position the energy recovery wheel in both an outdoor air path and a return air path to facilitate exchanging heat between an outdoor air stream and a return air stream. The positional axis of rotation is orthogonal to an operational axis of rotation. A supply fan draws a mix of outdoor air and return air through the energy recovery ventilator system. The energy recovery wheel rotates about an operational axis of rotation within a cabinet to exchange heat between the outdoor air stream and the return air stream.
The subject matter, which is regarded as the disclosure, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The following descriptions of the drawings should not be considered limiting in any way.
An energy recovery wheel is included within a cabinet of a rooftop AC system which has been modified to include streamlined components. The energy recovery wheel is rotatable about two axes and is integral to the modified rooftop AC unit. The energy recovery wheel is placed between separated air streams and can be rotated out of the way when not in use while still maintaining air stream separation.
Exhaust section 12 can be located upstream of filter section 14, evaporative coil section 16, and supply/heating section 18 with respect to airflow through prior art AC unit 10. Condensing section 20 can be located adjacent to supply/heating section 18 such that supply/heating section 18 is located between evaporative coil section 16 and condensing section 20. Cabinet 22 is a housing which surrounds the other components of prior art AC unit 10. Filters 24 can be located within filter section 14. Supply fan 26 can be located downstream of exhaust fan 28 with respect to the flow of outdoor air through cabinet 22. Filters 24 can be located upstream of supply fan 26. Exhaust fan 28 can be located upstream of supply fan 26 and filters 24, such that filters 24 are located between exhaust fan 28 and supply fan 26. During operation, return air can enter cabinet 22 at return inlet 30 within exhaust section 12. Return air can flow through filter section 14, evaporative coil section 16, and supply/heating section 18 and exit cabinet 22 at supply inlet 32 as re-conditioned supply air.
In the depicted example, supply fan 26 draws supply air through cabinet 22. Supply fan 26 can draw outdoor air in through prior art AC unit 10. Filters 24 can filter return air flowing through filter section 14. Exhaust fan 28 can draw return air into and through cabinet 22. Exhaust fan 28 can discharge return air outside of the building. During operation, prior art AC unit 10 provides ventilation to a building, and can additionally provide heating and/or cooling. A number of dampers (not shown in
Modified AC unit 100 can operate in substantially the same way as prior art AC unit 10 with respect to ventilation. Exhaust fan 120 can be positioned at an end of cabinet 114 and oriented parallel to the cross section shown in
In comparison to prior art AC unit 10 described above, certain components of modified AC unit 100 can be resized or moved. With respect to the location of filters 24 within prior art AC unit 10, filters 116 of modified AC unit 100 have been rotated 90 degrees to create room within cabinet 114. With respect to the size and location of exhaust fan 28 within prior art AC unit 10, exhaust fan 120 of modified AC unit 100 has been moved to an end of cabinet 114 and has been flattened. These modifications provide space for energy recovery section 104 within cabinet 114 while allowing cabinet 114 to be the same size as cabinet 22. As discussed in more detail below, energy recovery wheel 122 allows modified AC to transfer heat energy between the outdoor air and the return air.
Each cassette 128 includes a heat exchanger which allows energy recovery wheel 122 to transfer heat energy between two air sources. The two air sources can be, for example, outdoor air and return air. Cassettes 128 can be removable from energy recovery wheel 122, allowing for an individual cassette 128 to be serviced, replaced, or otherwise maintained. Energy recovery wheel 122 can be positioned so as to transfer heat between outdoor air and return air. This can be achieved by, for example, positioning energy recovery wheel 122 in both the outdoor air stream and the return air stream. Energy recovery wheel 122 can be rotated about operational axis R-R such that cassettes 128 are successively moved between the outdoor air stream and the return air stream. Each cassette 128 can thereby absorb heat from the warmer of the outdoor air stream and the return air stream and reject heat into the cooler of the outdoor air stream and the return air stream. For example, if the outdoor air is warmer than the return air, each cassette 128 can absorb heat from the outdoor air during the period of rotation when the cassette 128 is in contact with the outdoor air stream. The cassette 128 can then reject heat into the return air during the period of rotation when the cassette 128 is in contact with the return air stream. Energy recovery wheel 122 can be in heating mode when transferring heat energy from the outdoor air stream to the return air stream. Energy recovery wheel 122 can be in cooling mode when transferring heat energy from the return air stream to the outdoor air stream. When installed within a cabinet, such as cabinet 114 of
Energy recovery wheel 122 can be positioned within cabinet 114 such that exhaust fan 120 is downstream of energy recovery wheel 122 with respect to the return air stream, and supply fan 118 (not shown in
Energy recovery wheel 122 is rotatably mounted within cabinet 114 via bearing system 136. Energy recovery wheel 122 can be rotated about positional axis S—S between positions. In the example depicted, energy recovery wheel 122 can be rotated between an operational position, such as operational position A, and a bypass position, such as bypass position B. As described below, energy recovery wheel 122 can also have an operational mode and a bypass mode. These modes refer to the functioning of energy recovery wheel 122 during operation of modified AC unit 100.
Energy recovery wheel 122 can have an operational mode in which it exchanges heat between the outdoor air stream and the return air stream. This can be achieved by, for example, positioning energy recovery wheel 122 in both the outdoor air stream and the return air stream such that energy recovery wheel 122 is located in both the outdoor air path and the return air path, and each cassette 128 (shown in
Energy recovery wheel 122 can have a bypass mode in which it does not exchange heat between the outdoor air stream and the return air stream. This can be achieved by, for example, positioning energy recovery wheel 122 out of one or both of the outdoor air stream and the return air stream such that energy recovery wheel 122 is positioned between the outdoor air path and the return air path. In the depicted example, energy recovery wheel 122 is in a bypass mode when it is located in bypass position B. The positioning of energy recovery wheel 122 in bypass position B allows for energy recovery wheel 122 to not transfer heat and thereby to be in bypass mode. It should be understood that energy recovery wheel 122 can be positioned between the outdoor air path and the return air path even when either outdoor air or return air is not actively flowing through ERV system 132 (i.e. when at least one of dampers 134a-134c is closed). In the depicted example, walls 138 of cabinet 114 define operational position A and bypass position B of energy recovery wheel 122 and allow for air stream separation to be maintained when energy recovery wheel 122 is in either of operational position A or bypass position B.
The controller can include a memory unit, one or more processors, and one or more communication devices. The memory unit can be configured to store information within the controller during operation, and can be a computer-readable storage medium which includes a non-transitory medium. The one or more processors can be configured to implement functionality and/or process instructions for execution within the controller. The one or more communication devices can be configured to communicate with external devices via one or more networks, such as one or more wireless or wired networks or both. The controller can additionally include components such as an input device, output device, sensor system, and/or power source.
The controller can be configured to receive and carry out instructions for the operation and configuration of components within modified AC unit 100. For example, the controller can be configured to select a position for each of dampers 134a-134c, thereby selecting a mode for modified AC unit 100 as described in more detail below. The controller can be further configured to select a mode of energy recovery wheel 122. For example, the controller can be configured to direct the rotation actuator to move energy recovery wheel 122 into operational mode from bypass mode, or vice versa. The controller can be configured to automatically detect conditions such as temperature and/or humidity inside and outside the building and carry out pre-determined instructions based on the detected conditions. Additionally and/or alternatively, the controller can be configured to carry out instructions from a user.
When modified AC unit 100 is in mixed air mode, all dampers 134a-134c are at least partially open. This allows both outdoor air and indoor return air to flow through cabinet 114. Dampers 134a-134c are configurable to allow varying flow rates of outdoor air and/or indoor return air through cabinet 114. For example, when modified AC unit 100 is in mixed air mode, some of dampers 134a-134c can be completely open, and others of dampers 134a-134c can be partially open. This configuration can be varied as desired based on conditions such as outdoor air temperature and/or humidity.
When modified AC unit 100 is in outdoor air mode, dampers 134a and 134b are at least partially open, and damper 134cis closed. This allows exhaust fan 120 to exhaust indoor return air and supply fan 118 to draw in outdoor air. The closing of damper 134c prevents indoor return air from flowing back through modified AC unit 100 and causes the adjustable mix of outdoor air and return air drawn by supply fan 118 to be all outdoor air.
When modified AC unit 100 is in return air mode, dampers 134a and 134b are closed and damper 134c is at least partially open. This allows only indoor return air to flow through modified AC unit 100 such that the mix of outdoor air and return air drawn by supply fan 118 is all return air. It should be understood that, because in most operating modes buildings typically require at least some ventilation with outdoor supply air, return air mode may be infrequently used, but the disclosed modified AC unit 100 is capable of operating in a return air mode. Return air mode can be used in situations where, for example, extreme outdoor temperatures make drawing in outdoor air undesirable (such as extreme cold).
Incorporating an ERV system with an energy recovery wheel into a modified rooftop air conditioning unit provides several advantages. An integral ERV system can capture heat energy which would otherwise be wasted and can improve energy efficiency, and an energy recovery wheel which can be rotated out of the way when not in use affords users flexibility. An energy recovery wheel which that is rotated out of the way when not in use (for example, when in the bypass mode disclosed in this application) prevents a pressure drop across the AC system. Finally, resizing and rearranging components within the AC unit can allow the size of the cabinet to remain the same as an old cabinet. This decreases the cost to replace the unit and makes replacement easier by allowing an old cabinet to be entirely replaced with a new modified unit containing the ERV system.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
