CA2877249C - Variable effectiveness heat recovery ventilator - Google Patents
Variable effectiveness heat recovery ventilator Download PDFInfo
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- CA2877249C CA2877249C CA2877249A CA2877249A CA2877249C CA 2877249 C CA2877249 C CA 2877249C CA 2877249 A CA2877249 A CA 2877249A CA 2877249 A CA2877249 A CA 2877249A CA 2877249 C CA2877249 C CA 2877249C
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- heat exchange
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F12/00—Use of energy recovery systems in air conditioning, ventilation or screening
- F24F12/001—Use of energy recovery systems in air conditioning, ventilation or screening with heat-exchange between supplied and exhausted air
- F24F12/002—Use of energy recovery systems in air conditioning, ventilation or screening with heat-exchange between supplied and exhausted air using an intermediate heat-transfer fluid
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/70—Control systems characterised by their outputs; Constructional details thereof
- F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
- F24F11/83—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers
- F24F11/85—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers using variable-flow pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/30—Control or safety arrangements for purposes related to the operation of the system, e.g. for safety or monitoring
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
- F24F11/63—Electronic processing
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/70—Control systems characterised by their outputs; Constructional details thereof
- F24F11/72—Control systems characterised by their outputs; Constructional details thereof for controlling the supply of treated air, e.g. its pressure
- F24F11/74—Control systems characterised by their outputs; Constructional details thereof for controlling the supply of treated air, e.g. its pressure for controlling air flow rate or air velocity
- F24F11/77—Control systems characterised by their outputs; Constructional details thereof for controlling the supply of treated air, e.g. its pressure for controlling air flow rate or air velocity by controlling the speed of ventilators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/70—Control systems characterised by their outputs; Constructional details thereof
- F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
- F24F11/83—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F12/00—Use of energy recovery systems in air conditioning, ventilation or screening
- F24F12/001—Use of energy recovery systems in air conditioning, ventilation or screening with heat-exchange between supplied and exhausted air
- F24F12/006—Use of energy recovery systems in air conditioning, ventilation or screening with heat-exchange between supplied and exhausted air using an air-to-air heat exchanger
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F13/00—Details common to, or for air-conditioning, air-humidification, ventilation or use of air currents for screening
- F24F13/22—Means for preventing condensation or evacuating condensate
- F24F2013/221—Means for preventing condensation or evacuating condensate to avoid the formation of condensate, e.g. dew
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F2110/00—Control inputs relating to air properties
- F24F2110/10—Temperature
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/56—Heat recovery units
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Physics & Mathematics (AREA)
- Fuzzy Systems (AREA)
- Mathematical Physics (AREA)
- Fluid Mechanics (AREA)
- Air Conditioning Control Device (AREA)
Abstract
A heat recovery ventilator includes an outgoing duct having an outgoing airflow, an incoming duct having an incoming airflow, a heat exchange fluid circulating through a closed-loop heat exchange duct to transfer thermal energy between an outgoing airflow in the incoming airflow, a heat exchange pump within the closed-loop heat exchange duct for circulating the heat exchange fluid within the closed-loop heat exchange duct, a sensor located in the outgoing duct, and a controller coupled to the sensor and the heat exchange pump and programmed to cause the heat exchange pump to circulate the heat exchange fluid within the closed-loop heat exchange duct at an initial rate of circulation, receive a signal from the sensor associated with at least a temperature of the outgoing airflow, determine, based on the signal, that the temperature of the outgoing airflow is at or below a threshold temperature, and in response to determining that the temperature is below the threshold temperature, cause the pump to circulate heat exchange fluid at a reduced rate of circulation thereby adjusting the effectiveness of thermal energy transfer between the outgoing airflow to the incoming airflow.
Description
VARIABLE EFFECTIVENESS HEAT RECOVERY VENTILATOR
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Description Technical Field [0001]The present disclosure relates to heat recovery ventilators.
Background
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Description Technical Field [0001]The present disclosure relates to heat recovery ventilators.
Background
(0002] Heat recovery ventilators are utilized in ventilation units to exchange thermal energy between outgoing air exhausted from a conditioned space and incoming fresh air supplied to the conditioned space. By exchanging thermal energy, more efficient heating or cooling can be achieved compared to the same energy input to an electric heater or an air conditioner of the ventilation unit in which thermal energy is not exchanged.
[0003] Prior art heat recovery ventilators may have a single heat exchanger through which incoming and exhaust airflows both pass without mixing with one another.
As the two airflows pass through the heat exchanger, the warmer air flow transfers a portion of its heat to the cooler airflow by conduction through the heat exchanger. In this way heat is `recovered' from the warmer airflow, hence the name `heat recovery ventilator'.
As the two airflows pass through the heat exchanger, the warmer air flow transfers a portion of its heat to the cooler airflow by conduction through the heat exchanger. In this way heat is `recovered' from the warmer airflow, hence the name `heat recovery ventilator'.
[0004]In prior art heat recovery ventilators, thermal energy exchanged through .a thermally conductive barrier separating the incoming and outgoing airflows.
The amount of thermal energy exchanged is based on the temperature difference between the incoming and outgoing airflows. When the warmer outgoing airflow is cooled below its dew point, i.e., the temperature at which water vapour in the outgoing airflow condenses, moisture will condense out of the outgoing airflow and collect on the thermally conductive barrier. If the temperature of the thermally conductive barrier is below 0 C, the moisture will form a layer of ice that can eventually block the flow of the outgoing airflow.
-1-.
The amount of thermal energy exchanged is based on the temperature difference between the incoming and outgoing airflows. When the warmer outgoing airflow is cooled below its dew point, i.e., the temperature at which water vapour in the outgoing airflow condenses, moisture will condense out of the outgoing airflow and collect on the thermally conductive barrier. If the temperature of the thermally conductive barrier is below 0 C, the moisture will form a layer of ice that can eventually block the flow of the outgoing airflow.
-1-.
[0005] When the outgoing airflow is blocked due to ice build-up, prior art heat recovery ventilators may enter a 'defrost mode' in which the flow of incoming fresh air is stopped so that the warm outgoing air can blow against the built-up ice to cause thawing. Thus, during the defrost mode, incoming fresh air is not supplied to, and outgoing air is not removed from the conditioned space. In climates having extremely cold temperatures, the amount of time that the heat recovery ventilator spends in defrost mode may be such that the air quality of the conditioned space is negatively impacted.
[0006] Prior art that prevents condensation before it occurs in space conditioners may rely on varying the ratio of incoming to outgoing airflow rates or the input of additional energy to raise temperatures inside the device. Both approaches work reliably and economically when the temperature difference between the conditioned and unconditioned spaces is relatively close. However, as conditioned and unconditioned temperatures diverge, prior art devices that prevent condensation may develop limitations to reliably providing adequate ventilation to a conditioned space similar to those encountered by designs employing a 'defrost mode', or become undesirably expensive to build and operate.
[0007] Improvements to heat recovery ventilators are desired.
Summary
Summary
[0008]One aspect of the invention provides a heat recovery ventilator for transferring thermal energy from an outgoing airflow to an incoming airflow, the heat recovery ventilator includes an outgoing duct having an outgoing fan for moving the outgoing airflow from a conditioned space through the outflow duct, an incoming duct having an incoming fan for moving the incoming airflow through the incoming duct into the conditioned space, a heat exchange pump within a closed-loop heat exchange duct for circulating a heat exchange fluid within the closed-loop heat exchange duct, the closed-loop heat exchange duct comprising a first portion in thermal communication with the outgoing duct and a second portion in thermal communication with the incoming duct, a sensor located in the outgoing duct downstream from a location within the outgoing duct that is in thermal communication with the first portion of the closed-loop heat exchange duct, wherein the sensor measures a temperature of the outgoing airflow at the location, and a controller operatively coupled to the sensor and the heat exchange pump and programmed to cause the heat exchange pump to circulate the heat exchange fluid within the closed-loop heat exchange duct at an initial rate of circulation, receive a signal from the sensor associated with at least the temperature of the outgoing airflow, determine, based on the signal, that the temperature of the outgoing airflow is at or below a threshold temperature, and in response to determining that the temperature is below the threshold temperature, cause the pump to circulate heat exchange fluid at a reduced rate of circulation which is lower than the initial rate of circulation to reduce the thermal energy that is transferred from an outgoing airflow to an incoming airflow.
[0009]According to another aspect, the threshold temperature is determined based on an error limit of the sensor.
[0010] Acco rd n g to another aspect, the reduced rate of circulation is a predetermined percentage of the initial rate of circulation.
[0011]According to another aspect, the threshold temperature is zero degrees Celsius.
[0012] Acco rd i n g to another aspect, causing the pump to circulate heat exchange fluid at a reduced rate of circulation includes turning off the heat exchange pump.
[0013] According to another aspect, the sensor measures a relative humidity of the outgoing airflow.
[0014] According to another aspect, the threshold temperature is determined based on a dew point determined from the relative humidity.
[0015] Acco rd n g to another aspect, the heat exchange fluid is air.
[001 6]According to another aspect, the heat exchange pump is an impeller.
[0017] Acco rd i n g to another aspect, the initial rate of circulation is a rate of circulation at which a mass flow rate of heat exchange fluid multiplied by a heat capacity of the heat exchange fluid equals the lesser of an airflow mass flow rate multiplied by an airflow heat capacity for the outgoing airflow or the incoming airflow.
[0018]According to another aspect, the threshold temperature comprises a first threshold temperature and a second threshold temperature lower than the first threshold temperature, and the controller is programmed to, in response to determining that the temperature is at or below the first threshold temperature, cause the pump to circulate heat exchange fluid at a first reduced rate of circulation, and in response to determining that the temperature is at or below the second threshold temperature, cause the pump to circulate heat exchange fluid at a second reduced rate of circulation that is lower than the first rate of circulation.
[0019]According to another aspect, the first threshold temperature is determined based on an error limit of the sensor, and the first reduced rate of circulation is a percentage of the initial rate.
[0020]According to another aspect, the second threshold temperature is zero degrees Celsius, and the second reduced rate of circulation is provided by turning the heat exchange pump off.
Drawings [0021] The following figures set forth embodiments in which like reference numerals denote like parts. Embodiments are illustrated by way of example and not by way of limitation in the accompanying figures.
[0022] FIG. 1 is a schematic representation of a heat recovery ventilator according to an embodiment;
[0023] FIG. 2 is a schematic representation of a heat recovery ventilator according to another embodiment;
[0024] FIG. 3 is a flow chart illustrating a method for controlling a heat recovery ventilator according to an embodiment;
[0025] FIG. 4 is a flow chart illustrating a method for controlling a heat recovery ventilator according to another embodiment;
[0026] FIG. 5 is a flow chart illustrating a method for controlling a heat recovery ventilator according to another embodiment;
[0027] FIG. 6 is an isometric view of a heat recovery ventilator according to an embodiment;
[0028] FIGS. 7a is the same view of the heat recovery ventilator shown in FIG.
6 with portions of the housing cut away;
[0029] FIG. 7b is an isometric view of a backside of the heat recovery ventilator shown in FIG. 6 with portions of the housing cut away;
[0030] FIG. 8 is a front view of the heat recovery ventilator according to the embodiment shown in FIG. 6 with the front wall of the housing removed; and [0031] FIG. 9 is a schematic isometric view depicting the airflow through the heat recovery ventilator according to the embodiment shown in FIGS. 6 with the housing removed.
Detailed Description [0032] The following describes a heat recovery ventilator in which heat is exchanged between an outgoing airflow flowing through an outgoing duct and an incoming airflow through an incoming duct via a heat exchange fluid flowing through a closed-loop heat exchange duct. The rate of circulation of the heat exchange fluid is adjustable to vary the amount of thermal energy transferred between the incoming airflow and the outgoing airflow. A controller is utilized to control the rate of circulation of the heat exchange fluid based on the temperature of the outgoing airflow to inhibit condensate in the outgoing duct from freezing without interrupting the ventilation of the conditioned space. The disclosed heat recovery ventilator may be utilized to ventilate conditioned spaces located in environments in which the incoming air is below 0 C for extended periods of time, such as in arctic or sub-arctic climates, for example Northern Canada.
[0033] For simplicity and clarity of illustration, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. Numerous details are set forth to provide an understanding of the examples described herein.
The examples may be practiced without these details. In other instances, well-known methods, procedures, and components are not described in detail to avoid obscuring the examples described. The description is not to be considered as limited to the scope of the examples described herein.
[0034] Referring to FIG. 1, a heat recovery ventilator 100 includes an outgoing duct 102, an incoming duct 108, and a closed-loop heat exchange duct 114. The outgoing duct 102 and incoming duct 108 are separate to keep an outgoing airflow, represented by the arrow 104, flowing through the outgoing duct 102 from intermingling with an incoming airflow, represented by the arrow 110, flowing through the incoming duct 108.
Thermal energy is exchanged between the outgoing airflow 104 and the incoming airflow 110 by a heat exchange fluid, represented by the arrow 115, that flows through the closed-loop heat exchange duct 114.
[0035] The outgoing airflow 104 is air from inside a conditioned space 130, such as the inside of a room or a building, for example. The outgoing airflow 104 flows through the outgoing duct 102 to be vented outside of the conditioned space 130, such as the environment outside a building housing the conditioned space, for example. The incoming airflow 110 is air from outside the conditioned space that flows through the incoming duct 108 into the conditioned space 130. The outgoing airflow 104 removes air from within the conditioned space and the incoming airflow 110 replaces the removed air with fresh air.
[0036] The outgoing airflow 104 is forced through the outgoing duct 102 by an outgoing fan 106 and the incoming airflow 110 is forced through the incoming duct 108 by an incoming fan 112. The outgoing fan 106 and incoming fan 112 may include, for example, an impeller or other suitable mechanism for forcing air through the respective outgoing duct 102 and incoming duct 108. The outgoing fan 106 and incoming fan may be electrically powered, for example.
[0037] The closed-loop heat exchange duct 114 includes a first portion 116, in which the heat exchange fluid 115 is in thermal contact with the outgoing airflow 104, and a second portion 118, in which the heat exchange fluid is in thermal contact with the incoming airflow 110. The first portion 116 and the second portion 118 of the closed-loop heat exchange duct 114 may be, for example, heat exchange cores, or any other suitable structures for providing thermal contact between the heat exchange fluid 115 and the outgoing airflow 104 and the incoming airflow 110. Heat exchange cores include at least two channels separated by a thermally conductive wall such that two fluid streams flowing through a respective channel can exchange thermal energy without the two streams intermingling. Heat exchange cores are discussed in more detail below with reference to FIGS. 7a and 7b.
[0038] The closed-loop heat exchange duct 114 includes a pump 120 that circulates the heat exchange fluid 115 through the closed-loop heat exchange duct 114. The pump 120 is a variable speed pump to enable adjustment of a rate of circulation of the heat exchange fluid 115. In an embodiment, the heat exchange fluid 115 may be a gas, such as air, for example. In this embodiment, the pump 120 may be a fan having an impeller or other suitable mechanism for circulating the air through the closed-loop heat exchange duct 114. In another embodiment, the heat exchange fluid is a liquid such as, for example, water or a water-glycol mix. In this embodiment, the pump 120 may be any mechanism suitable for circulating the liquid through the closed-loop heat exchange duct 114.
[0039] In conditions in which the temperature of the incoming airflow 110 is less than zero degrees Celsius, such as in the winter in colder climates, or in arctic environments, the rate of circulation of the heat exchange fluid 115 may be varied to reduce the amount of thermal energy transferred from the outgoing airflow 104 to the incoming airflow 110 such that the temperature of the outgoing airflow 104 is not reduced to the point that condensate in the outgoing duct 102 freezes, forming ice.
[0040] In operation, the pump 120 is turned on to circulate the heat exchange fluid 115 through the closed-loop heat exchange duct 114. A portion of the heat exchange fluid 115 in the first portion 116 absorbs thermal energy from the outgoing airflow 104, heating the heat exchange fluid 115 in the first portion 116 and cooling the outgoing airflow 104 such that the outgoing airflow 104 downstream of the first portion 116 is cooler than the outgoing airflow 104 upstream of the first portion 116. The heated heat exchange fluid 115 exiting the first portion 116 flows through the closed-loop heat exchange duct 114 into the second portion 118 where thermal energy is transferred from the heat exchange fluid 115 in the second portion 118 to the incoming airflow 110, cooling the heat exchange fluid 115 in the second portion 118 and heating the incoming airflow 110 such that the incoming airflow 110 downstream of the second portion 118 is warmer than the incoming airflow 110 upstream of the second portion 118.
[0041] In FIG. 1, the heat exchange fluid 115 is shown circulating through the closed-loop heat exchange duct 114 in a counterclockwise direction, however the heat exchange fluid 115 could also flow in a clockwise direction.
[0042]A controller 122 is also operatively coupled to a sensor 124 within the outgoing duct 102. The sensor 124 measures the temperature of the outgoing airflow 104 prior to exiting the outgoing duct 102. The sensor 124 may be coupled to a wall within the outgoing duct 102 downstream from the first portion 116 of the closed-loop heat exchange duct 114. Locating the sensor 124 immediately downstream of the first portion 116 is desired so that the sensor 124 measures the temperature of the outgoing airflow 104 immediately after passing over the first portion 116. The temperature of the cooled outgoing airflow 104 immediately downstream of the first portion 116 provides the best indication of whether the condensate in the outgoing duct 102 is at risk of freezing.
[0043]In some embodiments, the sensor 124 may also measure the relative humidity of the outgoing airflow 104 in addition to measuring temperature. A single sensor 124 may be utilized to measure both the temperature and humidity, or the sensor 124 may comprise separate temperature and humidity sensors. For example, the sensor may be a Relative Humidity/Temperature Transmitter manufactured by Omega TM
under model number HX94A. Relative humidity measurements may be utilized to determine, for example by the controller, a dew point of the outgoing airflow 104, which provides a better indication of the temperature at which water vapour in the outgoing airflow 104 will condensate. In this embodiment, a determination that ice is likely to form may be made when the temperature of the outgoing airflow 104 is below the lesser of 0 C and the dew point of the outgoing airflow 104.
[0044]The amount of thermal energy transferred from the outgoing airflow 102 to the heat exchange fluid 115 and from the heat exchange fluid 115 to the incoming airflow 110 depends on the mass flow rates and the thermal heat capacities of the outgoing airflow 104, the incoming airflow 110 and the heat exchange fluid 115, and on the temperature differences between the outgoing airflow 104 and the heat exchange fluid 115 in the first portion 116 and between the incoming airflow 110 and the heat exchange fluid 115 in the second portion 118. Assuming that the temperature differences between the airflows 104, 110 and the heat exchange fluid, and the mass flow rates of the airflows 104, 110 are substantially constant, varying the rate of circulation of the heat exchange fluid 115 through the closed-loop heat exchange duct 114 varies the mass flow rate of the heat exchange fluid 115 which, in turn, varies the amount of thermal energy transferred from the outgoing airflow 104 to the incoming airflow 110 via the heat exchange fluid 115.
[0045] The controller 122 is operatively coupled to the pump 120 to vary the rate of circulation of the heat exchange fluid 115 through the closed-loop heat exchange duct 114 by, for example, varying the voltage supplied to the pump 120. The controller 122 may include, for example, a microprocessor 125 that executes computer-executable code stored in a memory 127 to determine whether to reduce the rate of circulation of the heat exchange fluid 115 to inhibit ice formation in the outgoing duct 102 based on the temperature, and relative humidity in some embodiments, measured by the sensor 124. The microprocessor 125 may be, for example, an Arduino TM
microcontroller.
[0046] Referring to FIG. 2, in an alternative embodiment of a heat recovery ventilator 145, a first sensor 140 is located in the outgoing duct 102 upstream from the first portion 116. A second sensor 142 is located in the incoming duct 108 upstream from the second portion 118. In this embodiment, rather than measuring the temperature of the cooled outgoing airflow 104 downstream of the first portion 116 directly, the theoretical temperature value of the cooled outgoing airflow 104 is calculated, for example by a controller 123, based on the temperature of the outgoing airflow 104 upstream of the first portion 116, measured by the first sensor 140, and the temperature of the incoming airflow 110, measured by the second sensor 142.
[0047] The controller 123 controls the pump 120 to vary the rate of circulation of the heat exchange fluid 115 based on the calculated temperature value. The controller 123 may include a microprocessor 125 that executes computer-executable code stored in a memory 129 to calculated the temperature of the cooled outgoing airflow 104 based on the temperature measurements of the first sensor 140 and the second sensor 412 and to determine whether to reduce the rate of circulation of the heat exchange fluid 115 based on the calculated temperature.
[0048] Referring now to the flow chart of FIG. 3, a method for controlling heat recovery ventilator 100 is shown. The method may be carried out by software executed, for example, by a processor of the controller 122. Coding of software for carrying out such a method is within the scope of a person of ordinary skill in the art given the present disclosure. The method may contain additional or fewer processes than shown and/or described, and may be performed in a different order. Computer-readable code executable by a processor of the controller 122 to perform the method may be stored in a computer-readable medium, such as a non-transitory computer-readable medium.
[0049] The rate of circulation of the heat exchange fluid 115 is set to an initial rate at 202. The initial rate of circulation may be a predetermined rate that, for example, exchanges the greatest amount of thermal energy between the outgoing airflow 102 and the incoming airflow 110. The initial rate of circulation for the heat exchange fluid 115 that provides the greatest amount of thermal heat exchange may be determined by determining a rate of circulation for which the product of the mass flow rate times the thermal heat capacity of the heat exchange fluid 115 is equal to the lesser of the products of the mass flow times the thermal heat capacity for the outgoing airflow 104 and the incoming airflow 110. When the heat exchange fluid 115 utilized is air, which has approximately the same thermal heat capacity as the outgoing and incoming airflows 104, 110, the greatest exchange of thermal energy occurs when the rate of circulation in which the mass flow of the heat exchange fluid 115 is equal to the lesser of the mass flows of the outgoing airflow 104 and the incoming airflow 110.
(0050] At 204, the temperature of the outgoing airflow 104 downstream of the first portion 116 is measured. The temperature may be determined by the sensor 124 or may be determined by the controller 122 based on a signal received from the sensor 124. Measuring the temperature may include the controller 122 signaling for the sensor 124 to take a measurement. As discussed above, rather than directly measuring the temperature of the outgoing airflow 104 downstream of first portion 116, the temperature determined at 204 may be a theoretical value calculated from temperature measurements by a first sensor of the temperature of the outgoing air 104 entering the outgoing duct 102 and by a second sensor of the temperature of the incoming airflow 110 entering the incoming airflow side.
[0051]At 206, a determination whether the temperature meets a first threshold is made.
Determining that the first threshold is met may include determining that the measured temperature is less than or equal to the first threshold. The first threshold may be set at, for example, 0 C because 0 C is the temperature at which freezing may begin to occur. In other embodiments, the first threshold may be set to be within the sensor's 124 error limit of 0 C. For example, if the sensor's 124 error limit is 3 C, then the first threshold may be set at 3 C.
(0052] When the determination at 206 is NO, the method returns to step 204 and further measurements of the temperature are made as described above. In this way, the temperature of the outgoing airflow 104 and, in some embodiments the incoming airflow 110, is monitored overtime.
(0053] When the determination at 206 is YES, the method continues to 208 and the rate of circulation is set to a reduced rate that is lower than the initial rate.
Setting the rate of circulation of the heat exchange fluid 115 to a reduced rate reduces the amount of thermal energy transferred from the outgoing airflow 104 to the heat exchange fluid 115 to inhibit the formation of ice in the outgoing duct 102. The reduced rate may be, for example, a rate that optimizes the amount of thermal energy exchanged between the outgoing airflow 104 and incoming airflow 110 while inhibiting ice formation within the outgoing duct 102. In an embodiment the reduced rate may be, for example, a predetermined percentage of the initial rate. In another embodiment, the reduced rate may be effectively zero, which is provided by turning off the power to the pump 120. A
reduced rate of effectively zero will provide effectively no exchange of thermal energy between the outgoing airflow 104 and the incoming airflow 110 and may be utilized when the temperature of the outgoing airflow 104 is such that ice formation in the outgoing duct 102 is imminent or has already begun.
[0054]After the rate of circulation is set to the reduced rate at 208, the method continues to 210 in which the temperature of the outgoing airflow 104 is measured again. Step 210 is carried out similarly to step 204 and, therefore, is not further described to avoid repetition.
[0055]At 212, a determination is made whether the measurement at 210 meets a second threshold. Determining that the second threshold is met may include determining that the measurement is greater than or equal to the second threshold. In some embodiments the second threshold may be the same as the first threshold.
In other embodiments, the second threshold may be higher than the first threshold.
[0056] When the determination at 212 is YES, the method continues to 202 and the rate of circulation is set to the initial rate of circulation. By setting the rate of circulation to the initial rate of circulation when the temperature of the outgoing airflow meets a second threshold increases the rate of circulation and, thus, the amount of thermal energy exchanged between the outgoing airflow 104 and the incoming airflow 110 in order to increase the energy efficiency of the heat recovery ventilator 100 when the risk of ice formation in the outgoing duct 102 is reduced.
[0057] When the determination at 212 is NO, the method returns to 210 and a further temperature measurement is made. In this way, the outgoing airflow 104 and, in some embodiments the incoming airflow 110, is monitored after the rate of circulation is set to the reduced rate of circulation.
[0058] Referring to FIG. 4, a flow chart illustrating an alternative method of controlling the heat recovery ventilator 100 is shown. In the method shown in FIG. 4, steps 302-312 are similar to steps 202-212, respectively, shown in FIG. 3 and described above and, therefore, will not be further described to avoid repetition.
[0059] However, when the measurement does not meet a second threshold, i.e., "NO"
at 312, the method continues to 314 and a determination whether the temperature meets a third threshold is made. The third threshold may be less than the first threshold at 308. Determining that the temperature meets the third threshold may include determining that the temperature is less than or equal to the third threshold.
[0060] When the determination 314 is YES, the method continues to 316 in which the rate of circulation is set to a second reduced rate of circulation. The second rate of circulation may be less than the first rate of circulation. In an embodiment, the first threshold may be 3 C, the reduced rate may be half of the initial rate, the second threshold may be 0 C, and the second reduced rate may be effectively zero.
[0061]After the rate of circulation is set to the second reduced rate, the method returns to 310 in which the temperature is further measured.
[0062] By providing two thresholds having an associated reduced rate of circulation of the heat exchange fluid, the heat recovery ventilator 100 may address the situation in which the temperature of the outgoing airflow 104 continues to drop after the rate of circulation is set to the reduced rate.
[0063] In other embodiments, any number of thresholds having associated reduced rates of circulation may be included. Increasing number of thresholds, each threshold having an associated rate of circulation of the heat exchange fluid 115, provides a heat recover ventilator 100 with increased energy efficiency by better optimizing the amount of thermal energy exchanged between the outgoing airflow 104 and the incoming airflow 110 while inhibiting the formation of ice within the outgoing duct 102.
[0064] Referring to FIG. 5, a flow chart illustrating a method of controlling the heat recovery ventilator 100 in which the sensor 124 measures both temperature and relative humidity is shown. In the method shown in FIG. 5, steps 350, 356-362 are similar to steps 202, 206-212, respectively, shown in FIG. 3 and described above and, therefore, will not be further described to avoid repetition.
[0065]At 352, both the temperature and relative humidity of the outgoing airflow 104 are measured. The temperature and relative humidity may be determined by the sensor 124 or may be determined by the controller 122 based on signals received from the sensor 124. Measuring the temperature and relative humidity may include the controller 122 signaling for the sensor 124 to take a measurement.
[0066]At 354, first and second thresholds are determined based on the measured relative humidity. As discussed above, the relative humidity and temperature of the outgoing airflow 104 determines the dew point at which water vapour condensates out of the outgoing airflow 104. In an embodiment, the first threshold may be set to the lesser of the dew point and 0 C. The second threshold may be determined to be the same as the first threshold. In other embodiments, the second threshold may be higher than the first threshold.
[0067]When the relative humidity of outgoing airflow 104 is very low, the dew point may be less than 0 C. By setting the first threshold to a dew point that is below 0 C, the heat recovery ventilator 100 exchanges more thermal energy while inhibiting ice formation and, thus is better optimized, than if the first threshold were set to 0 C.
(0068] Referring now to FIGS. 6, 7a, and 7b, an example heat recovery ventilator 400 utilizing a heat exchange fluid 115 is shown. The heat recovery ventilator 400 is usable with controller 122 to vary a rate of circulation of a heat exchange fluid 115. The heat recovery ventilator 400 utilizes air as the heat exchange fluid 115 and utilizes a pair of heat exchange cores 432, 436 that generally correspond to the first portion 116 and second portion 118 of the closed-loop heat exchange duct 114 discussed with reference to FIG. 1.
[0069]The heat recovery ventilator 400 includes a housing having an inside wall 404 that is positioned closest the conditioned space when the heat recovery ventilator 400 is installed, an outside wall 406 that is positioned away from the conditioned space, sidewalls 408, 410, a top wall 412, and a bottom wall 414. The inside wall 404 includes two openings 416, 418 and the outside wall 406 includes two openings 420, 422.
[0070] Within the housing 402, a dividing wall 424 separates the housing 402 into an outgoing airflow side 428 and an incoming airflow side 430.
[0071] Outgoing side dividers 440, 441, 442, 443 extending from the dividing wall 424 into the outgoing airflow side 428 separate the outgoing airflow side 428 into four quadrants 470, 471, 472, and 473. Quadrant 470 includes an outgoing impeller coupled to an outgoing airflow inlet 444 that extends from the opening 416 in the outside wall 404 to the outgoing side divider 442. The outgoing impeller 446 functionally corresponds to the outgoing fan 106 in FIG. 1.
[0072] The outgoing airflow side 428 includes an outgoing heat exchange core 432.
The outgoing heat exchange core 432 includes two sets of channels 434 and 435.
The channels 434 facilitate air flowing between quadrant 470 and quadrant 472, and the channels 435 facilitate air flowing between quadrant 471 and quadrant 473.
[0073] An outgoing duct 480 functionally corresponding to the outgoing duct 104 of FIG.
1 is formed by the outgoing airflow inlet 444, quadrant 470, channels 434 of the heat exchange core 432, and quadrant 472.
[0074] Incoming side dividers 445, 447, 449, and 451 extend from the dividing wall 424 into the incoming airflow side 430 to separate the incoming airflow side 430 into four quadrants 474, 475, 476, and 477. Quadrant 477 of the incoming airflow side includes an incoming impeller 450 coupled to an incoming airflow inlet 448 extends from the opening 420. The incoming impeller 450 functionally corresponds to the incoming fan 112 in FIG. 1.
[0075] The incoming airflow side 430 includes an incoming heat exchange core 436.
The incoming heat exchange core 436 includes two sets of channels 438 and 439.
The channels 438 facilitate air flowing between quadrant 475 and quadrant 477, and the channels 439 facilitate air flowing between quadrant 474 and quadrant 476.
[0076] An incoming duct 482 functionally corresponding to the incoming duct 108 in FIG.
1 is formed by the incoming airflow inlet 448, quadrant 477, channels 438 of the incoming heat exchange core 436, and the quadrant 477.
[0077]Although the outgoing heat exchange core 432 and the incoming heat exchange core 436 shown in FIGS. 7a and 7b include four channels each (two channels in each of the two sets of channels), in other embodiments the outgoing heat exchange core 432 and the incoming heat exchange core 436 may include more or less than four channels.
Increasing a number of channels in a heat exchange core increases the surface area over which the two airflows are in thermal contact, increasing the efficiency of the exchange of thermal energy between the airflows. An example of a heat exchange core type usable as the outgoing heat exchange core 432 and the incoming heat exchange core 436 is the 167999 series heat exchange cores manufactured by AIR-ERV
TechonologyTM.
[0078] Quadrant 476 of the incoming airflow side 430 includes a heat exchange impeller 454 coupled to a heat exchange conduit 452 that extends from the dividing wall 424 to the sidewall 410. The heat exchange impeller 454 is a variable speed impeller and functionally corresponds to the pump 120 in FIG. 1. The heat exchange impeller may be a DB175-XX55 series variable speed centrifugal fan manufactured by McLean TM, which has a variable speed between 0 and 2875 RPM associated with input power voltages between OV and 12V, for example.
[0079] A closed-loop heat exchange duct 484 functionally corresponding to the closed-loop heat exchange core 114 in FIG. 1 is formed by the heat exchange conduit 452 and the quadrants 471, 477, 474 and 476.
[0080] Referring now to FIG. 8, the quadrant 472 that forms part of the outgoing duct 480 includes a trough 456 disposed over an inside surface of the bottom wall 414. The trough 456 collects condensate that forms when the air in the outgoing duct 480 is cooled in the outgoing heat exchange core 432. The condensate that is collected in trough 456 flows out of the housing 402 through a drain 458 in the bottom wall 414.
[0081] The quadrant 472 also includes a sensor 624 functionally corresponding to the sensor 124 in FIG. 1. The sensor 624 is a HX94A temperature and humidity sensor manufactured by Omega TM. The sensor 624 extends into the quadrant 472 from an upper portion of the outgoing side divider 443. The sensor 624 includes a casing 625 that thermally separates the sensor 624 from the outgoing side divider 443 to reduce effect of the temperature of the outgoing side divider 443 on the measured temperature.
The sensor 624 is positioned near the outgoing heat exchange core 432 to measure the temperature of the air in the outgoing duct 480 exiting the outgoing heat exchange core 432.
[001 6]According to another aspect, the heat exchange pump is an impeller.
[0017] Acco rd i n g to another aspect, the initial rate of circulation is a rate of circulation at which a mass flow rate of heat exchange fluid multiplied by a heat capacity of the heat exchange fluid equals the lesser of an airflow mass flow rate multiplied by an airflow heat capacity for the outgoing airflow or the incoming airflow.
[0018]According to another aspect, the threshold temperature comprises a first threshold temperature and a second threshold temperature lower than the first threshold temperature, and the controller is programmed to, in response to determining that the temperature is at or below the first threshold temperature, cause the pump to circulate heat exchange fluid at a first reduced rate of circulation, and in response to determining that the temperature is at or below the second threshold temperature, cause the pump to circulate heat exchange fluid at a second reduced rate of circulation that is lower than the first rate of circulation.
[0019]According to another aspect, the first threshold temperature is determined based on an error limit of the sensor, and the first reduced rate of circulation is a percentage of the initial rate.
[0020]According to another aspect, the second threshold temperature is zero degrees Celsius, and the second reduced rate of circulation is provided by turning the heat exchange pump off.
Drawings [0021] The following figures set forth embodiments in which like reference numerals denote like parts. Embodiments are illustrated by way of example and not by way of limitation in the accompanying figures.
[0022] FIG. 1 is a schematic representation of a heat recovery ventilator according to an embodiment;
[0023] FIG. 2 is a schematic representation of a heat recovery ventilator according to another embodiment;
[0024] FIG. 3 is a flow chart illustrating a method for controlling a heat recovery ventilator according to an embodiment;
[0025] FIG. 4 is a flow chart illustrating a method for controlling a heat recovery ventilator according to another embodiment;
[0026] FIG. 5 is a flow chart illustrating a method for controlling a heat recovery ventilator according to another embodiment;
[0027] FIG. 6 is an isometric view of a heat recovery ventilator according to an embodiment;
[0028] FIGS. 7a is the same view of the heat recovery ventilator shown in FIG.
6 with portions of the housing cut away;
[0029] FIG. 7b is an isometric view of a backside of the heat recovery ventilator shown in FIG. 6 with portions of the housing cut away;
[0030] FIG. 8 is a front view of the heat recovery ventilator according to the embodiment shown in FIG. 6 with the front wall of the housing removed; and [0031] FIG. 9 is a schematic isometric view depicting the airflow through the heat recovery ventilator according to the embodiment shown in FIGS. 6 with the housing removed.
Detailed Description [0032] The following describes a heat recovery ventilator in which heat is exchanged between an outgoing airflow flowing through an outgoing duct and an incoming airflow through an incoming duct via a heat exchange fluid flowing through a closed-loop heat exchange duct. The rate of circulation of the heat exchange fluid is adjustable to vary the amount of thermal energy transferred between the incoming airflow and the outgoing airflow. A controller is utilized to control the rate of circulation of the heat exchange fluid based on the temperature of the outgoing airflow to inhibit condensate in the outgoing duct from freezing without interrupting the ventilation of the conditioned space. The disclosed heat recovery ventilator may be utilized to ventilate conditioned spaces located in environments in which the incoming air is below 0 C for extended periods of time, such as in arctic or sub-arctic climates, for example Northern Canada.
[0033] For simplicity and clarity of illustration, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. Numerous details are set forth to provide an understanding of the examples described herein.
The examples may be practiced without these details. In other instances, well-known methods, procedures, and components are not described in detail to avoid obscuring the examples described. The description is not to be considered as limited to the scope of the examples described herein.
[0034] Referring to FIG. 1, a heat recovery ventilator 100 includes an outgoing duct 102, an incoming duct 108, and a closed-loop heat exchange duct 114. The outgoing duct 102 and incoming duct 108 are separate to keep an outgoing airflow, represented by the arrow 104, flowing through the outgoing duct 102 from intermingling with an incoming airflow, represented by the arrow 110, flowing through the incoming duct 108.
Thermal energy is exchanged between the outgoing airflow 104 and the incoming airflow 110 by a heat exchange fluid, represented by the arrow 115, that flows through the closed-loop heat exchange duct 114.
[0035] The outgoing airflow 104 is air from inside a conditioned space 130, such as the inside of a room or a building, for example. The outgoing airflow 104 flows through the outgoing duct 102 to be vented outside of the conditioned space 130, such as the environment outside a building housing the conditioned space, for example. The incoming airflow 110 is air from outside the conditioned space that flows through the incoming duct 108 into the conditioned space 130. The outgoing airflow 104 removes air from within the conditioned space and the incoming airflow 110 replaces the removed air with fresh air.
[0036] The outgoing airflow 104 is forced through the outgoing duct 102 by an outgoing fan 106 and the incoming airflow 110 is forced through the incoming duct 108 by an incoming fan 112. The outgoing fan 106 and incoming fan 112 may include, for example, an impeller or other suitable mechanism for forcing air through the respective outgoing duct 102 and incoming duct 108. The outgoing fan 106 and incoming fan may be electrically powered, for example.
[0037] The closed-loop heat exchange duct 114 includes a first portion 116, in which the heat exchange fluid 115 is in thermal contact with the outgoing airflow 104, and a second portion 118, in which the heat exchange fluid is in thermal contact with the incoming airflow 110. The first portion 116 and the second portion 118 of the closed-loop heat exchange duct 114 may be, for example, heat exchange cores, or any other suitable structures for providing thermal contact between the heat exchange fluid 115 and the outgoing airflow 104 and the incoming airflow 110. Heat exchange cores include at least two channels separated by a thermally conductive wall such that two fluid streams flowing through a respective channel can exchange thermal energy without the two streams intermingling. Heat exchange cores are discussed in more detail below with reference to FIGS. 7a and 7b.
[0038] The closed-loop heat exchange duct 114 includes a pump 120 that circulates the heat exchange fluid 115 through the closed-loop heat exchange duct 114. The pump 120 is a variable speed pump to enable adjustment of a rate of circulation of the heat exchange fluid 115. In an embodiment, the heat exchange fluid 115 may be a gas, such as air, for example. In this embodiment, the pump 120 may be a fan having an impeller or other suitable mechanism for circulating the air through the closed-loop heat exchange duct 114. In another embodiment, the heat exchange fluid is a liquid such as, for example, water or a water-glycol mix. In this embodiment, the pump 120 may be any mechanism suitable for circulating the liquid through the closed-loop heat exchange duct 114.
[0039] In conditions in which the temperature of the incoming airflow 110 is less than zero degrees Celsius, such as in the winter in colder climates, or in arctic environments, the rate of circulation of the heat exchange fluid 115 may be varied to reduce the amount of thermal energy transferred from the outgoing airflow 104 to the incoming airflow 110 such that the temperature of the outgoing airflow 104 is not reduced to the point that condensate in the outgoing duct 102 freezes, forming ice.
[0040] In operation, the pump 120 is turned on to circulate the heat exchange fluid 115 through the closed-loop heat exchange duct 114. A portion of the heat exchange fluid 115 in the first portion 116 absorbs thermal energy from the outgoing airflow 104, heating the heat exchange fluid 115 in the first portion 116 and cooling the outgoing airflow 104 such that the outgoing airflow 104 downstream of the first portion 116 is cooler than the outgoing airflow 104 upstream of the first portion 116. The heated heat exchange fluid 115 exiting the first portion 116 flows through the closed-loop heat exchange duct 114 into the second portion 118 where thermal energy is transferred from the heat exchange fluid 115 in the second portion 118 to the incoming airflow 110, cooling the heat exchange fluid 115 in the second portion 118 and heating the incoming airflow 110 such that the incoming airflow 110 downstream of the second portion 118 is warmer than the incoming airflow 110 upstream of the second portion 118.
[0041] In FIG. 1, the heat exchange fluid 115 is shown circulating through the closed-loop heat exchange duct 114 in a counterclockwise direction, however the heat exchange fluid 115 could also flow in a clockwise direction.
[0042]A controller 122 is also operatively coupled to a sensor 124 within the outgoing duct 102. The sensor 124 measures the temperature of the outgoing airflow 104 prior to exiting the outgoing duct 102. The sensor 124 may be coupled to a wall within the outgoing duct 102 downstream from the first portion 116 of the closed-loop heat exchange duct 114. Locating the sensor 124 immediately downstream of the first portion 116 is desired so that the sensor 124 measures the temperature of the outgoing airflow 104 immediately after passing over the first portion 116. The temperature of the cooled outgoing airflow 104 immediately downstream of the first portion 116 provides the best indication of whether the condensate in the outgoing duct 102 is at risk of freezing.
[0043]In some embodiments, the sensor 124 may also measure the relative humidity of the outgoing airflow 104 in addition to measuring temperature. A single sensor 124 may be utilized to measure both the temperature and humidity, or the sensor 124 may comprise separate temperature and humidity sensors. For example, the sensor may be a Relative Humidity/Temperature Transmitter manufactured by Omega TM
under model number HX94A. Relative humidity measurements may be utilized to determine, for example by the controller, a dew point of the outgoing airflow 104, which provides a better indication of the temperature at which water vapour in the outgoing airflow 104 will condensate. In this embodiment, a determination that ice is likely to form may be made when the temperature of the outgoing airflow 104 is below the lesser of 0 C and the dew point of the outgoing airflow 104.
[0044]The amount of thermal energy transferred from the outgoing airflow 102 to the heat exchange fluid 115 and from the heat exchange fluid 115 to the incoming airflow 110 depends on the mass flow rates and the thermal heat capacities of the outgoing airflow 104, the incoming airflow 110 and the heat exchange fluid 115, and on the temperature differences between the outgoing airflow 104 and the heat exchange fluid 115 in the first portion 116 and between the incoming airflow 110 and the heat exchange fluid 115 in the second portion 118. Assuming that the temperature differences between the airflows 104, 110 and the heat exchange fluid, and the mass flow rates of the airflows 104, 110 are substantially constant, varying the rate of circulation of the heat exchange fluid 115 through the closed-loop heat exchange duct 114 varies the mass flow rate of the heat exchange fluid 115 which, in turn, varies the amount of thermal energy transferred from the outgoing airflow 104 to the incoming airflow 110 via the heat exchange fluid 115.
[0045] The controller 122 is operatively coupled to the pump 120 to vary the rate of circulation of the heat exchange fluid 115 through the closed-loop heat exchange duct 114 by, for example, varying the voltage supplied to the pump 120. The controller 122 may include, for example, a microprocessor 125 that executes computer-executable code stored in a memory 127 to determine whether to reduce the rate of circulation of the heat exchange fluid 115 to inhibit ice formation in the outgoing duct 102 based on the temperature, and relative humidity in some embodiments, measured by the sensor 124. The microprocessor 125 may be, for example, an Arduino TM
microcontroller.
[0046] Referring to FIG. 2, in an alternative embodiment of a heat recovery ventilator 145, a first sensor 140 is located in the outgoing duct 102 upstream from the first portion 116. A second sensor 142 is located in the incoming duct 108 upstream from the second portion 118. In this embodiment, rather than measuring the temperature of the cooled outgoing airflow 104 downstream of the first portion 116 directly, the theoretical temperature value of the cooled outgoing airflow 104 is calculated, for example by a controller 123, based on the temperature of the outgoing airflow 104 upstream of the first portion 116, measured by the first sensor 140, and the temperature of the incoming airflow 110, measured by the second sensor 142.
[0047] The controller 123 controls the pump 120 to vary the rate of circulation of the heat exchange fluid 115 based on the calculated temperature value. The controller 123 may include a microprocessor 125 that executes computer-executable code stored in a memory 129 to calculated the temperature of the cooled outgoing airflow 104 based on the temperature measurements of the first sensor 140 and the second sensor 412 and to determine whether to reduce the rate of circulation of the heat exchange fluid 115 based on the calculated temperature.
[0048] Referring now to the flow chart of FIG. 3, a method for controlling heat recovery ventilator 100 is shown. The method may be carried out by software executed, for example, by a processor of the controller 122. Coding of software for carrying out such a method is within the scope of a person of ordinary skill in the art given the present disclosure. The method may contain additional or fewer processes than shown and/or described, and may be performed in a different order. Computer-readable code executable by a processor of the controller 122 to perform the method may be stored in a computer-readable medium, such as a non-transitory computer-readable medium.
[0049] The rate of circulation of the heat exchange fluid 115 is set to an initial rate at 202. The initial rate of circulation may be a predetermined rate that, for example, exchanges the greatest amount of thermal energy between the outgoing airflow 102 and the incoming airflow 110. The initial rate of circulation for the heat exchange fluid 115 that provides the greatest amount of thermal heat exchange may be determined by determining a rate of circulation for which the product of the mass flow rate times the thermal heat capacity of the heat exchange fluid 115 is equal to the lesser of the products of the mass flow times the thermal heat capacity for the outgoing airflow 104 and the incoming airflow 110. When the heat exchange fluid 115 utilized is air, which has approximately the same thermal heat capacity as the outgoing and incoming airflows 104, 110, the greatest exchange of thermal energy occurs when the rate of circulation in which the mass flow of the heat exchange fluid 115 is equal to the lesser of the mass flows of the outgoing airflow 104 and the incoming airflow 110.
(0050] At 204, the temperature of the outgoing airflow 104 downstream of the first portion 116 is measured. The temperature may be determined by the sensor 124 or may be determined by the controller 122 based on a signal received from the sensor 124. Measuring the temperature may include the controller 122 signaling for the sensor 124 to take a measurement. As discussed above, rather than directly measuring the temperature of the outgoing airflow 104 downstream of first portion 116, the temperature determined at 204 may be a theoretical value calculated from temperature measurements by a first sensor of the temperature of the outgoing air 104 entering the outgoing duct 102 and by a second sensor of the temperature of the incoming airflow 110 entering the incoming airflow side.
[0051]At 206, a determination whether the temperature meets a first threshold is made.
Determining that the first threshold is met may include determining that the measured temperature is less than or equal to the first threshold. The first threshold may be set at, for example, 0 C because 0 C is the temperature at which freezing may begin to occur. In other embodiments, the first threshold may be set to be within the sensor's 124 error limit of 0 C. For example, if the sensor's 124 error limit is 3 C, then the first threshold may be set at 3 C.
(0052] When the determination at 206 is NO, the method returns to step 204 and further measurements of the temperature are made as described above. In this way, the temperature of the outgoing airflow 104 and, in some embodiments the incoming airflow 110, is monitored overtime.
(0053] When the determination at 206 is YES, the method continues to 208 and the rate of circulation is set to a reduced rate that is lower than the initial rate.
Setting the rate of circulation of the heat exchange fluid 115 to a reduced rate reduces the amount of thermal energy transferred from the outgoing airflow 104 to the heat exchange fluid 115 to inhibit the formation of ice in the outgoing duct 102. The reduced rate may be, for example, a rate that optimizes the amount of thermal energy exchanged between the outgoing airflow 104 and incoming airflow 110 while inhibiting ice formation within the outgoing duct 102. In an embodiment the reduced rate may be, for example, a predetermined percentage of the initial rate. In another embodiment, the reduced rate may be effectively zero, which is provided by turning off the power to the pump 120. A
reduced rate of effectively zero will provide effectively no exchange of thermal energy between the outgoing airflow 104 and the incoming airflow 110 and may be utilized when the temperature of the outgoing airflow 104 is such that ice formation in the outgoing duct 102 is imminent or has already begun.
[0054]After the rate of circulation is set to the reduced rate at 208, the method continues to 210 in which the temperature of the outgoing airflow 104 is measured again. Step 210 is carried out similarly to step 204 and, therefore, is not further described to avoid repetition.
[0055]At 212, a determination is made whether the measurement at 210 meets a second threshold. Determining that the second threshold is met may include determining that the measurement is greater than or equal to the second threshold. In some embodiments the second threshold may be the same as the first threshold.
In other embodiments, the second threshold may be higher than the first threshold.
[0056] When the determination at 212 is YES, the method continues to 202 and the rate of circulation is set to the initial rate of circulation. By setting the rate of circulation to the initial rate of circulation when the temperature of the outgoing airflow meets a second threshold increases the rate of circulation and, thus, the amount of thermal energy exchanged between the outgoing airflow 104 and the incoming airflow 110 in order to increase the energy efficiency of the heat recovery ventilator 100 when the risk of ice formation in the outgoing duct 102 is reduced.
[0057] When the determination at 212 is NO, the method returns to 210 and a further temperature measurement is made. In this way, the outgoing airflow 104 and, in some embodiments the incoming airflow 110, is monitored after the rate of circulation is set to the reduced rate of circulation.
[0058] Referring to FIG. 4, a flow chart illustrating an alternative method of controlling the heat recovery ventilator 100 is shown. In the method shown in FIG. 4, steps 302-312 are similar to steps 202-212, respectively, shown in FIG. 3 and described above and, therefore, will not be further described to avoid repetition.
[0059] However, when the measurement does not meet a second threshold, i.e., "NO"
at 312, the method continues to 314 and a determination whether the temperature meets a third threshold is made. The third threshold may be less than the first threshold at 308. Determining that the temperature meets the third threshold may include determining that the temperature is less than or equal to the third threshold.
[0060] When the determination 314 is YES, the method continues to 316 in which the rate of circulation is set to a second reduced rate of circulation. The second rate of circulation may be less than the first rate of circulation. In an embodiment, the first threshold may be 3 C, the reduced rate may be half of the initial rate, the second threshold may be 0 C, and the second reduced rate may be effectively zero.
[0061]After the rate of circulation is set to the second reduced rate, the method returns to 310 in which the temperature is further measured.
[0062] By providing two thresholds having an associated reduced rate of circulation of the heat exchange fluid, the heat recovery ventilator 100 may address the situation in which the temperature of the outgoing airflow 104 continues to drop after the rate of circulation is set to the reduced rate.
[0063] In other embodiments, any number of thresholds having associated reduced rates of circulation may be included. Increasing number of thresholds, each threshold having an associated rate of circulation of the heat exchange fluid 115, provides a heat recover ventilator 100 with increased energy efficiency by better optimizing the amount of thermal energy exchanged between the outgoing airflow 104 and the incoming airflow 110 while inhibiting the formation of ice within the outgoing duct 102.
[0064] Referring to FIG. 5, a flow chart illustrating a method of controlling the heat recovery ventilator 100 in which the sensor 124 measures both temperature and relative humidity is shown. In the method shown in FIG. 5, steps 350, 356-362 are similar to steps 202, 206-212, respectively, shown in FIG. 3 and described above and, therefore, will not be further described to avoid repetition.
[0065]At 352, both the temperature and relative humidity of the outgoing airflow 104 are measured. The temperature and relative humidity may be determined by the sensor 124 or may be determined by the controller 122 based on signals received from the sensor 124. Measuring the temperature and relative humidity may include the controller 122 signaling for the sensor 124 to take a measurement.
[0066]At 354, first and second thresholds are determined based on the measured relative humidity. As discussed above, the relative humidity and temperature of the outgoing airflow 104 determines the dew point at which water vapour condensates out of the outgoing airflow 104. In an embodiment, the first threshold may be set to the lesser of the dew point and 0 C. The second threshold may be determined to be the same as the first threshold. In other embodiments, the second threshold may be higher than the first threshold.
[0067]When the relative humidity of outgoing airflow 104 is very low, the dew point may be less than 0 C. By setting the first threshold to a dew point that is below 0 C, the heat recovery ventilator 100 exchanges more thermal energy while inhibiting ice formation and, thus is better optimized, than if the first threshold were set to 0 C.
(0068] Referring now to FIGS. 6, 7a, and 7b, an example heat recovery ventilator 400 utilizing a heat exchange fluid 115 is shown. The heat recovery ventilator 400 is usable with controller 122 to vary a rate of circulation of a heat exchange fluid 115. The heat recovery ventilator 400 utilizes air as the heat exchange fluid 115 and utilizes a pair of heat exchange cores 432, 436 that generally correspond to the first portion 116 and second portion 118 of the closed-loop heat exchange duct 114 discussed with reference to FIG. 1.
[0069]The heat recovery ventilator 400 includes a housing having an inside wall 404 that is positioned closest the conditioned space when the heat recovery ventilator 400 is installed, an outside wall 406 that is positioned away from the conditioned space, sidewalls 408, 410, a top wall 412, and a bottom wall 414. The inside wall 404 includes two openings 416, 418 and the outside wall 406 includes two openings 420, 422.
[0070] Within the housing 402, a dividing wall 424 separates the housing 402 into an outgoing airflow side 428 and an incoming airflow side 430.
[0071] Outgoing side dividers 440, 441, 442, 443 extending from the dividing wall 424 into the outgoing airflow side 428 separate the outgoing airflow side 428 into four quadrants 470, 471, 472, and 473. Quadrant 470 includes an outgoing impeller coupled to an outgoing airflow inlet 444 that extends from the opening 416 in the outside wall 404 to the outgoing side divider 442. The outgoing impeller 446 functionally corresponds to the outgoing fan 106 in FIG. 1.
[0072] The outgoing airflow side 428 includes an outgoing heat exchange core 432.
The outgoing heat exchange core 432 includes two sets of channels 434 and 435.
The channels 434 facilitate air flowing between quadrant 470 and quadrant 472, and the channels 435 facilitate air flowing between quadrant 471 and quadrant 473.
[0073] An outgoing duct 480 functionally corresponding to the outgoing duct 104 of FIG.
1 is formed by the outgoing airflow inlet 444, quadrant 470, channels 434 of the heat exchange core 432, and quadrant 472.
[0074] Incoming side dividers 445, 447, 449, and 451 extend from the dividing wall 424 into the incoming airflow side 430 to separate the incoming airflow side 430 into four quadrants 474, 475, 476, and 477. Quadrant 477 of the incoming airflow side includes an incoming impeller 450 coupled to an incoming airflow inlet 448 extends from the opening 420. The incoming impeller 450 functionally corresponds to the incoming fan 112 in FIG. 1.
[0075] The incoming airflow side 430 includes an incoming heat exchange core 436.
The incoming heat exchange core 436 includes two sets of channels 438 and 439.
The channels 438 facilitate air flowing between quadrant 475 and quadrant 477, and the channels 439 facilitate air flowing between quadrant 474 and quadrant 476.
[0076] An incoming duct 482 functionally corresponding to the incoming duct 108 in FIG.
1 is formed by the incoming airflow inlet 448, quadrant 477, channels 438 of the incoming heat exchange core 436, and the quadrant 477.
[0077]Although the outgoing heat exchange core 432 and the incoming heat exchange core 436 shown in FIGS. 7a and 7b include four channels each (two channels in each of the two sets of channels), in other embodiments the outgoing heat exchange core 432 and the incoming heat exchange core 436 may include more or less than four channels.
Increasing a number of channels in a heat exchange core increases the surface area over which the two airflows are in thermal contact, increasing the efficiency of the exchange of thermal energy between the airflows. An example of a heat exchange core type usable as the outgoing heat exchange core 432 and the incoming heat exchange core 436 is the 167999 series heat exchange cores manufactured by AIR-ERV
TechonologyTM.
[0078] Quadrant 476 of the incoming airflow side 430 includes a heat exchange impeller 454 coupled to a heat exchange conduit 452 that extends from the dividing wall 424 to the sidewall 410. The heat exchange impeller 454 is a variable speed impeller and functionally corresponds to the pump 120 in FIG. 1. The heat exchange impeller may be a DB175-XX55 series variable speed centrifugal fan manufactured by McLean TM, which has a variable speed between 0 and 2875 RPM associated with input power voltages between OV and 12V, for example.
[0079] A closed-loop heat exchange duct 484 functionally corresponding to the closed-loop heat exchange core 114 in FIG. 1 is formed by the heat exchange conduit 452 and the quadrants 471, 477, 474 and 476.
[0080] Referring now to FIG. 8, the quadrant 472 that forms part of the outgoing duct 480 includes a trough 456 disposed over an inside surface of the bottom wall 414. The trough 456 collects condensate that forms when the air in the outgoing duct 480 is cooled in the outgoing heat exchange core 432. The condensate that is collected in trough 456 flows out of the housing 402 through a drain 458 in the bottom wall 414.
[0081] The quadrant 472 also includes a sensor 624 functionally corresponding to the sensor 124 in FIG. 1. The sensor 624 is a HX94A temperature and humidity sensor manufactured by Omega TM. The sensor 624 extends into the quadrant 472 from an upper portion of the outgoing side divider 443. The sensor 624 includes a casing 625 that thermally separates the sensor 624 from the outgoing side divider 443 to reduce effect of the temperature of the outgoing side divider 443 on the measured temperature.
The sensor 624 is positioned near the outgoing heat exchange core 432 to measure the temperature of the air in the outgoing duct 480 exiting the outgoing heat exchange core 432.
- 16-[0082]The sensor 624 is operatively coupled to a controller, such as controller 122, that is located outside of the housing 402 of the heat recover ventilator 400 in the present example. The controller 122 is also operatively coupled to the heat exchange impeller 454, the outgoing impeller 446, and the incoming impeller 450. The controller 122 is connected to the sensor 624, the heat exchange impeller 454, the outgoing impeller 446, and the incoming impeller 450 by, for examples, wires 628 that pass into the housing 402. In some embodiments, the controller 122 may be wirelessly connected to the sensor 624, the heat exchange impeller 454, the outgoing impeller 446, and the incoming impeller 450. Power supplies are connected to the outgoing impeller 464 and the incoming impeller 446 by wires that also pass into the housing 402.
[0083] The controller 122 also includes a power supply (not shown) to supply a variable input power voltage to the heat exchange impeller 454 to vary a rate of circulation of an airflow through the heat exchange duct 484 based on the temperature measurements from the sensor 624, as described above.
[0084] Referring now to FIG. 9, the passage of airflows through the outgoing duct 480, the incoming duct 482, and the closed-loop heat exchange duct 484 will be described.
[0085] The outgoing impeller 446 generates an outgoing airflow 804 functionally corresponding to the outgoing airflow 104 in FIG. 1. The outgoing impeller 446 draws air from the conditioned space (not shown) through the opening 416 and into the outgoing airflow inlet 444. From the outgoing airflow inlet 444, the outgoing impeller 446 forces the air into the quadrant 470, through the channels 434 of the outgoing heat exchange core 432 into the quadrant 472 and out through opening 422 into the external environment (not shown).
[0086] The opening 416 may be open directly to the conditioned space or may be connected to the conditioned space by a duct (not shown). The opening 422 may be open directly to the external environment of the conditioned space or may be connected to the external environment by a duct (not shown).
[0087] In the heat recovery ventilator 400, the outgoing airflow 804 exits the outgoing duct 480 at a lower portion of the housing 402 such that any condensate that is generated from the cooling of the outgoing airflow 804 in the outgoing heat exchange core 432 is collected by the trough 456 and exits the housing 402 through the drain 458.
[0083] The controller 122 also includes a power supply (not shown) to supply a variable input power voltage to the heat exchange impeller 454 to vary a rate of circulation of an airflow through the heat exchange duct 484 based on the temperature measurements from the sensor 624, as described above.
[0084] Referring now to FIG. 9, the passage of airflows through the outgoing duct 480, the incoming duct 482, and the closed-loop heat exchange duct 484 will be described.
[0085] The outgoing impeller 446 generates an outgoing airflow 804 functionally corresponding to the outgoing airflow 104 in FIG. 1. The outgoing impeller 446 draws air from the conditioned space (not shown) through the opening 416 and into the outgoing airflow inlet 444. From the outgoing airflow inlet 444, the outgoing impeller 446 forces the air into the quadrant 470, through the channels 434 of the outgoing heat exchange core 432 into the quadrant 472 and out through opening 422 into the external environment (not shown).
[0086] The opening 416 may be open directly to the conditioned space or may be connected to the conditioned space by a duct (not shown). The opening 422 may be open directly to the external environment of the conditioned space or may be connected to the external environment by a duct (not shown).
[0087] In the heat recovery ventilator 400, the outgoing airflow 804 exits the outgoing duct 480 at a lower portion of the housing 402 such that any condensate that is generated from the cooling of the outgoing airflow 804 in the outgoing heat exchange core 432 is collected by the trough 456 and exits the housing 402 through the drain 458.
-17-[0088]The incoming impeller 450 generates an incoming airflow 810 functionally corresponding to the incoming airflow 110 in FIG. 1. The incoming impeller 450 draws air from the external environment through the opening 420 and into the incoming airflow inlet 448. From the incoming airflow inlet 448, the incoming impeller 450 forces the air into the quadrant 477, through the channels 438 of the incoming heat exchange core 436 into the quadrant 475, and out of the incoming duct 482 through opening 418 into the conditioned space.
[0089]The opening 420 may be open to the external environment directly or may be connected to the external environment through a duct (not shown). The opening may be open to the conditioned space directly or may be connected to the conditioned space by a duct (not shown).
(0090] The heat exchange impeller 454 generates a heat exchange airflow 815 functionally corresponding to the heat exchange fluid 115 in FIG. 1. The heat exchange impeller 454 draws air from the quadrant 473 through the opening 423 and into the heat exchange conduit 452. From the heat exchange conduit 452, the heat exchange impeller 454 forces the air into the quadrant 476, through the channels 439 of the incoming heat exchange core 436 into the quadrant 474, through the opening 425 into the quadrant 471, through the channels 435 of the outgoing heat exchange core back into the quadrant 473 where the air is drawn through the opening 423 to repeat the cycle. .
[0091]As the heat exchange airflow 815 passes through the outgoing heat exchange core 432, thermal energy from the outgoing airflow 804 is absorbed, heating the heat exchange airflow 815 and cooling the outgoing airflow 804. The heated heat exchange fluid 815 then passes through the incoming heat exchange core 436 where thermal energy is absorbed by the incoming airflow 810, cooling the heat exchange airflow 815 and heating the incoming airflow 810 prior to the incoming airflow flowing into the conditioned space.
(0092] The present disclosure describes a heat recovery ventilator in which the rate of circulation of a heat exchange fluid may be adjusted to adjust the amount of thermal energy transferred between an incoming airflow and an outgoing airflow.
[0089]The opening 420 may be open to the external environment directly or may be connected to the external environment through a duct (not shown). The opening may be open to the conditioned space directly or may be connected to the conditioned space by a duct (not shown).
(0090] The heat exchange impeller 454 generates a heat exchange airflow 815 functionally corresponding to the heat exchange fluid 115 in FIG. 1. The heat exchange impeller 454 draws air from the quadrant 473 through the opening 423 and into the heat exchange conduit 452. From the heat exchange conduit 452, the heat exchange impeller 454 forces the air into the quadrant 476, through the channels 439 of the incoming heat exchange core 436 into the quadrant 474, through the opening 425 into the quadrant 471, through the channels 435 of the outgoing heat exchange core back into the quadrant 473 where the air is drawn through the opening 423 to repeat the cycle. .
[0091]As the heat exchange airflow 815 passes through the outgoing heat exchange core 432, thermal energy from the outgoing airflow 804 is absorbed, heating the heat exchange airflow 815 and cooling the outgoing airflow 804. The heated heat exchange fluid 815 then passes through the incoming heat exchange core 436 where thermal energy is absorbed by the incoming airflow 810, cooling the heat exchange airflow 815 and heating the incoming airflow 810 prior to the incoming airflow flowing into the conditioned space.
(0092] The present disclosure describes a heat recovery ventilator in which the rate of circulation of a heat exchange fluid may be adjusted to adjust the amount of thermal energy transferred between an incoming airflow and an outgoing airflow.
- 18-[0093] Utilizing a heat exchange fluid circulating between an outgoing airflow and an incoming airflow, as well as a controller facilitates heat recovery during uninterrupted ventilation of a conditioned space that inhibits the outgoing airflow from being cooled to the point that ice forms in an outgoing duct.
[0094] In very cold conditions, the disclosed heat recovery ventilator is able to adjust the amount of thermal energy exchanged between the outgoing and incoming airflows to inhibit ice formation, without having to enter a 'defrost mode' in which incoming airflow is stopped in order to thaw formed ice within an outgoing duct, such as in prior art heat recovery ventilators. During a defrost mode, no fresh air is introduced. The colder the incoming air, such as in very cold climates, the less ventilation of the conditioned space occurs because a greater amount of time is spent in defrost mode, which may seriously affect the air quality and occupant health within the conditioned space.
[0095] The disclosed heat recovery ventilator adjusts the effectiveness of the heat exchange between the incoming and outgoing airflows in response to the temperature of the outgoing airflow to better optimize the amount of thermal energy transferred while inhibiting ice formation, facilitating uninterrupted ventilation of the conditioned space.
[0096] In the disclosed heat recovery ventilator, the temperature of the outgoing airflow may be measured immediately after exiting an outgoing heat exchange core in order to better determine when ice formation in the outgoing duct is likely and, thus, when to reduce the rate of circulation of the heat exchange fluid.
[0097] The amount of heat exchanged between the outgoing and incoming airflows may be better optimized by utilizing a dew point of the outgoing airflow, determined from the measured relative humidity of the outgoing airflow, to determine when ice formation in the outgoing duct is likely and, thus, when to reduce the rate of circulation of the heat exchange fluid.
[0098] In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments.
However, it will be apparent to one skilled in the art that these specific details are not required. In other instances, well-known electrical structures and circuits are shown in block diagram form in order not to obscure the understanding. For example, specific details are not
[0094] In very cold conditions, the disclosed heat recovery ventilator is able to adjust the amount of thermal energy exchanged between the outgoing and incoming airflows to inhibit ice formation, without having to enter a 'defrost mode' in which incoming airflow is stopped in order to thaw formed ice within an outgoing duct, such as in prior art heat recovery ventilators. During a defrost mode, no fresh air is introduced. The colder the incoming air, such as in very cold climates, the less ventilation of the conditioned space occurs because a greater amount of time is spent in defrost mode, which may seriously affect the air quality and occupant health within the conditioned space.
[0095] The disclosed heat recovery ventilator adjusts the effectiveness of the heat exchange between the incoming and outgoing airflows in response to the temperature of the outgoing airflow to better optimize the amount of thermal energy transferred while inhibiting ice formation, facilitating uninterrupted ventilation of the conditioned space.
[0096] In the disclosed heat recovery ventilator, the temperature of the outgoing airflow may be measured immediately after exiting an outgoing heat exchange core in order to better determine when ice formation in the outgoing duct is likely and, thus, when to reduce the rate of circulation of the heat exchange fluid.
[0097] The amount of heat exchanged between the outgoing and incoming airflows may be better optimized by utilizing a dew point of the outgoing airflow, determined from the measured relative humidity of the outgoing airflow, to determine when ice formation in the outgoing duct is likely and, thus, when to reduce the rate of circulation of the heat exchange fluid.
[0098] In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments.
However, it will be apparent to one skilled in the art that these specific details are not required. In other instances, well-known electrical structures and circuits are shown in block diagram form in order not to obscure the understanding. For example, specific details are not
-19-provided as to whether the embodiments described herein are implemented as a software routine, hardware circuit, firmware, or a combination thereof.
[0099] The above-described embodiments are intended to be examples only.
Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art. The scope of the claims should not be limited by the particular embodiments set forth herein, but should be construed in a manner consistent with the specification as a whole.
[0099] The above-described embodiments are intended to be examples only.
Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art. The scope of the claims should not be limited by the particular embodiments set forth herein, but should be construed in a manner consistent with the specification as a whole.
- 20 -
Claims (13)
1. A heat recovery ventilator for transferring thermal energy from an outgoing airflow to an incoming airflow, the heat recovery ventilator comprising:
an outgoing duct having an outgoing fan for moving the outgoing airflow from of a conditioned space through the outflow duct;
an incoming duct having an incoming fan for moving the incoming airflow through the incoming duct into the conditioned space;
a heat exchange pump within a closed-loop heat exchange duct for circulating a heat exchange fluid within the closed-loop heat exchange duct, the closed-loop heat exchange duct comprising a first portion in thermal communication with the outgoing duct and a second portion in thermal communication with the incoming duct;
a sensor located in the outgoing duct downstream from a location within the outgoing duct that is in thermal communication with the first portion of the closed-loop heat exchange duct, wherein the sensor measures a temperature of the outgoing airflow at the location; and a controller operatively coupled to the sensor and the heat exchange pump and programmed to:
cause the heat exchange pump to circulate the heat exchange fluid within the closed-loop heat exchange duct at an initial rate of circulation;
receive a signal from the sensor associated with at least the temperature of the outgoing airflow;
determine, based on the signal, that the temperature of the outgoing airflow is at or below a threshold temperature; and in response to determining that the temperature is below the threshold temperature, cause the pump to circulate heat exchange fluid at a reduced rate of circulation which is lower than the initial rate of circulation to reduce the thermal energy that is transferred from an outgoing airflow to an incoming airflow;
thereby reducing the effectiveness of thermal energy transfer between the incoming and outgoing airflows from its theoretical maximum so as to prevent excessive moisture from condensing in the outgoing airflow, and enabling uninterrupted ventilation between a conditioned space and an unconditioned space of arbitrarily different temperatures.
an outgoing duct having an outgoing fan for moving the outgoing airflow from of a conditioned space through the outflow duct;
an incoming duct having an incoming fan for moving the incoming airflow through the incoming duct into the conditioned space;
a heat exchange pump within a closed-loop heat exchange duct for circulating a heat exchange fluid within the closed-loop heat exchange duct, the closed-loop heat exchange duct comprising a first portion in thermal communication with the outgoing duct and a second portion in thermal communication with the incoming duct;
a sensor located in the outgoing duct downstream from a location within the outgoing duct that is in thermal communication with the first portion of the closed-loop heat exchange duct, wherein the sensor measures a temperature of the outgoing airflow at the location; and a controller operatively coupled to the sensor and the heat exchange pump and programmed to:
cause the heat exchange pump to circulate the heat exchange fluid within the closed-loop heat exchange duct at an initial rate of circulation;
receive a signal from the sensor associated with at least the temperature of the outgoing airflow;
determine, based on the signal, that the temperature of the outgoing airflow is at or below a threshold temperature; and in response to determining that the temperature is below the threshold temperature, cause the pump to circulate heat exchange fluid at a reduced rate of circulation which is lower than the initial rate of circulation to reduce the thermal energy that is transferred from an outgoing airflow to an incoming airflow;
thereby reducing the effectiveness of thermal energy transfer between the incoming and outgoing airflows from its theoretical maximum so as to prevent excessive moisture from condensing in the outgoing airflow, and enabling uninterrupted ventilation between a conditioned space and an unconditioned space of arbitrarily different temperatures.
2. The heat recovery ventilator according to claim 1, wherein the threshold temperature is determined based on an error limit of the sensor.
3. The heat recovery ventilator according to claim 2, wherein the reduced rate of circulation is a predetermined percentage of the initial rate of circulation.
4. The heat recovery ventilator according to claim 1, wherein the threshold temperature is zero degrees Celsius.
5. The heat recovery ventilator according to claim 4, wherein causing the pump to circulate heat exchange fluid at a reduced rate of circulation comprises switching off the heat exchange pump.
6. The heat recovery ventilator according to any one of claims 1 to 5, wherein the sensor measures a relative humidity of the outgoing airflow.
7. The heat recovery ventilator according to claim 6, wherein the threshold temperature is determined based on a dew point determined from the relative humidity.
8. The heat recovery ventilator according to any of claims 1 to 7, wherein the heat exchange fluid is air.
9. The heat recovery ventilator according to any one of claims 1 to 8, wherein the heat exchange pump is an impeller.
10. The heat recovery ventilator according to any one of claims 1 to 9, wherein the initial rate of circulation is a rate of circulation at which a mass flow rate of heat exchange fluid multiplied by a heat capacity of the heat exchange fluid equals the lesser of an airflow mass flow rate multiplied by an airflow heat capacity for the outgoing airflow or the incoming airflow.
11. The heat recovery ventilator according to claim 1, wherein:
the threshold temperature comprises a first threshold temperature and a second threshold temperature lower than the first threshold temperature; and the controller is programmed to:
in response to determining that the temperature is at or below the first threshold temperature, cause the pump to circulate heat exchange fluid at a first reduced rate of circulation; and in response to determining that the temperature is at or below the second threshold temperature, cause the pump to circulate heat exchange fluid at a second reduced rate of circulation that is lower than the first rate of circulation.
the threshold temperature comprises a first threshold temperature and a second threshold temperature lower than the first threshold temperature; and the controller is programmed to:
in response to determining that the temperature is at or below the first threshold temperature, cause the pump to circulate heat exchange fluid at a first reduced rate of circulation; and in response to determining that the temperature is at or below the second threshold temperature, cause the pump to circulate heat exchange fluid at a second reduced rate of circulation that is lower than the first rate of circulation.
12. The heat recovery ventilator according to claim 11, wherein the first threshold temperature is determined based on an error limit of the sensor, and the first reduced rate of circulation is a percentage of the initial rate.
13. The heat recovery ventilator according to one of claims 11 and 12, wherein the second threshold temperature is zero degrees Celsius, and the second reduced rate of circulation is provided by turning the heat exchange pump off.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2877249A CA2877249C (en) | 2015-01-08 | 2015-01-08 | Variable effectiveness heat recovery ventilator |
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| Application Number | Priority Date | Filing Date | Title |
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| CA2877249A CA2877249C (en) | 2015-01-08 | 2015-01-08 | Variable effectiveness heat recovery ventilator |
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| CA2877249A1 CA2877249A1 (en) | 2016-07-08 |
| CA2877249C true CA2877249C (en) | 2017-05-09 |
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| CN106765823B (en) * | 2017-03-23 | 2023-04-07 | 福州鹏飞制冷设备有限公司 | Energy-saving air treatment equipment |
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