Fan Speed Control for Preventing Frost Condition of an Evaporator

This application claims priority to and the benefit under 35 U.S.C. § 119 (e) of U.S. Provisional Application No. 63/568,486, filed Mar. 22, 2024, and entitled “AIR FUNNEL FOR A HEAT PUMP SYSTEM OF A WATER HEATER,” the entire disclosure of which is hereby incorporated herein by reference.

The present disclosure generally relates to a heat pump system for a water heating appliance, and more specifically, to a fan speed control for preventing a frost condition within an evaporator for the heat pump system.

Water heaters are utilized for transferring heat into a reservoir of water for delivery throughout a structure. Certain water heaters include a heat pump system that utilizes a thermal exchange media for transferring heat between an evaporating device that absorbs heat from the surrounding area and to a condensing device which rejects heat into the water being heated. Blowers are typically utilized for producing airflow through portions of the heat pump system. In certain conditions, the evaporator can develop frost which limits the flow of air around the coils of the evaporator.

According to one aspect of the present disclosure, a water heating appliance includes: a reservoir for storing water to be heated; a refrigerant path having a compressor that directs a thermal exchange media through the refrigerant path having an evaporator that absorbs heat from process air, an evaporator fan that directs the process air across a surface of the evaporator, and a condensing coil that delivers the heat to the reservoir; a temperature sensing system that monitors a temperature of the water to be heated and a surface temperature of the evaporator; and a controller in communication with the temperature sensing system and the evaporator fan. The controller monitors a rate of change of the surface temperature. In response to the rate of change of the surface temperature being a decreased rate, the controller compares the decreased rate to at least a rate of change of the temperature of the water to be heated. In response to the decreased rate diverging from the rate of change of the temperature of the water, indicative of a frost condition, the controller operates the evaporator fan at an increased speed to direct an increased flow of the process air over the surface of the evaporator to increase the surface temperature and define the rate of change of the surface temperature to be an increased rate.

According to another aspect of the present disclosure, a heat pump system for a water heating appliance includes a refrigerant path that includes an evaporator that absorbs heat from process air, an evaporator fan that directs the process air across coils of the evaporator, a compressor for directing a thermal exchange media through the refrigerant path, and a condenser that includes a condensing coil and water to be heated. The heat pump system further includes a controller that monitors a surface temperature of a surface of the coils, a rate of change of the surface temperature, a temperature difference between a media temperature of the water to be heated and the surface temperature, and a rate of change of the temperature difference. In response to a rate of change of the surface temperature defining a decreased rate, the controller compares the decreased rate to at least a rate of change of the temperature difference. In response to the rate of change of the temperature difference being beyond a threshold rate, indicative of a frost condition, the controller increases a speed of the evaporator fan to deliver additional process air across the surface of the coils. The additional process air operates to increase the surface temperature of the coils of the evaporator and decrease the temperature difference to be within a standard operating condition.

According to yet another aspect of the present disclosure, a water heating appliance includes a refrigerant path having a compressor that directs a thermal exchange media through the refrigerant path. The refrigerant path has an evaporator that absorbs heat from process air, an evaporator fan that directs the process air across a surface of the evaporator, and a condensing portion that delivers the heat to water within a reservoir. The water heating appliance also includes a temperature sensing system that monitors a media temperature of the water and a surface temperature of the evaporator. The water heating appliance further includes a controller in communication with the temperature sensing system to determine a rate of change of the surface temperature. In response to the rate of change of the surface temperature defining a decreased rate, the controller compares the decreased rate to a temperature difference between the media temperature and the surface temperature and a rate of change of the temperature difference. In response to the rate of change of the temperature difference increasing to a frost condition, the controller operates a motor of the evaporator fan to increase the flow of the process air across the surface of the evaporator to increase the surface temperature of the evaporator and decrease the temperature difference to be below a threshold difference and within a standard operating condition. In response to the temperature difference reaching the standard operating condition, the controller operates the motor of the evaporator fan to decrease the flow of the process air across the surface of the evaporator.

These and other features, advantages, and objects of the present disclosure will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.

The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles described herein.

As required, detailed embodiments of the present disclosure are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to a detailed design; some schematics may be exaggerated or minimized to show function overview. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the concepts as oriented in. However, it is to be understood that the concepts may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

The present illustrated embodiments reside primarily in combinations of method steps and apparatus components related to a heat pump system for a water heating appliance, and more specifically, to a fan speed control for preventing a frost condition within an evaporator for the heat pump system. Accordingly, the apparatus components and method steps have been represented, where appropriate, by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Further, like numerals in the description and drawings represent like elements.

As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items, can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

In this document, relational terms, such as “first” and “second,” “top and “bottom,” and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. Whether or not a numerical value or end-point of a range in the specification recites “about,” the numerical value or end-point of a range is intended to include two embodiments: one modified by “about,” and one not modified by “about.” It will be further understood that the end-points of each of the ranges are significant both in relation to the other end-point, and independently of the other end-point.

The terms “substantial,” “substantially,” and variations thereof as used herein are intended to note that a described feature is equal or approximately equal to a value or description. For example, a “substantially planar” surface is intended to denote a surface that is planar or approximately planar. Moreover, “substantially” is intended to denote that two values are equal or approximately equal. In some embodiments, “substantially” may denote values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

As used herein the terms “the,” “a,” or “an,” mean “at least one,” and should not be limited to “only one” unless explicitly indicated to the contrary. Thus, for example, reference to “a component” includes embodiments having two or more such components unless the context clearly indicates otherwise.

Referring to, reference numeralgenerally designates a heat pump system incorporated within a water heating appliance. The heat pump systemutilizes a thermal exchange mediafor transferring heatcollected within an evaporatorand into a media, such as water, that is to be heated within a reservoir. The heat pump systemcan be utilized within a tank-type water heating appliance, or within a tankless-type water heating appliance. Additionally, certain hybrid configurations of water heaters can utilize the heat pump systemthat may include a reservoirof waterto be heated, as well as a tankless-component of a water heating appliance.

Referring again to, the water heating applianceincludes the reservoirfor storing a fluid, typically water, to be heated. The heat pump systemincludes a refrigerant paththat includes a compressorthat directs a thermal exchange mediathrough the refrigerant path. The refrigerant pathincludes the evaporatorthat absorbs heatfrom ambient air. An evaporator fan, which can include a blowerhaving a blower housing, directs the ambient airacross a surfaceof coilsfor the evaporator. A condensing portion, which can include one or more coils, is included within the heat pump systemthat delivers the heat, absorbed by the evaporator, to the reservoir. This heat, in turn, is delivered from the thermal exchange mediawithin the coilsoff the condensing portionand into the waterbeing heated therein. A temperature sensing systemmonitors a media temperatureof the waterbeing heated as well as a temperature of the evaporator, typically in the form of a surface temperatureof the coilsfor the evaporator. A controlleris in communication with the temperature sensing systemand the evaporator fan. The controllermonitors a temperature differencebetween the media temperatureof waterwithin the reservoirand the surface temperatureof the coilsfor the evaporator. The controlleralso monitors a rate of changeof the surface temperature. In response to the rate of changeof the surface temperaturedefining a decreased rate, the controllermonitors a rate of changeof the temperature difference. The rate of changeof the temperature differenceexceeding a threshold rate, in combination with the decreased rate, is typically indicative of a frost condition. When the frost conditionis determined, the controlleroperates a motorfor the evaporator fanto direct additional amounts of ambient airover the surfaceof the evaporator, typically through an increased speedof the evaporator fan. The increased airflowof ambient airover the evaporatorserves to increase the surface temperatureof the coilsfor the evaporator. Additionally, the increase in the surface temperatureof the coilsfor the evaporatormodifies the rate of changeof the surface temperaturefrom the decreased rate, indicative of the frost condition, to an increased rate. The increased airflowof ambient airover the evaporatoralso decreases the temperature differencebetween the media temperatureof the waterwithin the reservoirand the surface temperatureof the coilsfor the evaporator. The evaporator fanis operated at the increased speeduntil such time as the temperature differenceis below the threshold differenceindicative of a standard operating conditionof the evaporatorand the heat pump system.

In the context of the device, as disclosed herein, the term decreased raterefers to a variation in the rate of change that produces a lesser rate of increase of the surface temperatureof the evaporator. Additionally, the decreased ratecan also refer to a negative rate of change where the surface temperatureof the evaporatordecreases. This can also be referred to as a negative rate of change, a negative slope, a cooling rate of change, or other similar terminology. The decreased ratewith respect to the rate of change of the surface temperatureis described herein to mark the conditions where the controllerlooks to other operating parameters of the heat pump systemfor verifying the existence of a frost condition. The decreased rate, described herein, is typically the initial indicator of the frost condition. Once this initial indicator is determined, the controllerlooks to other temperature and operational readings for verification that the frost conditionis in its beginning stages or the frost conditionis presently occurring.

The motorfor the evaporator fancan be a multi-speed fan that is configured to operate at a plurality of speedsof the evaporator fan. The controlleroperates the motorof the evaporator fanbased upon a rate of changethat the temperature differencechanges, typically increasing, which is indicative of the frost condition. Minor fluctuations in the temperature differencebetween the media temperatureof the waterand the surface temperatureof the coilsof the evaporatorcan occur in the standard operating conditionof the heat pump system. Where the rate of changeof the temperature differenceincludes a more rapid rate of change, this can be indicative of an onset of a frost conditionor the occurrence of a frost condition. In these more drastic rates of change, the frost conditioncan be marked by a lesser increase in the media temperature, in combination with a decrease in the surface temperatureof the coilsfor the evaporator. This type of change in the temperature difference, indicative of the frost condition, is reflected by a rapid rate of changein the temperature difference.

In certain aspects of the device, the temperature differencecan be used to set the speed of the motorfor the evaporator fan. By way of example, and not limitation, where the decreased rateof the surface temperaturedecreases rapidly and the temperature difference, in turn, increases rapidly, the controllercan operate the motorat a high speed settingto generate a high degree of airflowof ambient airacross the surfaceof the evaporator. By increasing the airflowof this warmer ambient airacross the evaporator, the surface temperatureof the evaporatortends to increase, thereby preventing frost condition, or, if needed, decreasing the amount of frost on the evaporator. Stated another way, increasing the airflowof the ambient airacross the evaporatorcauses the evaporatorto absorb greater amounts of heat. While absorbing greater amounts of heat, the surface temperatureof the evaporatortends to increase, thereby preventing, or mitigating, a frost conditionof the evaporator.

In addition, the speed of the motorcan be determined by the effect of a previous increase in the speed of the motorfor the evaporator fan. Where the frost conditionis recognized by the controller, the temperature sensing systemcontinues to monitor the rate of changeof the surface temperature, the temperature difference, and the rate of changein the temperature difference. Where the increase in speed of the motorfor the evaporator fandoes not result in a change in the rate of changeof the surface temperatureto be the increased rate, or a decrease in the temperature difference, or a decrease in the rate of changein the temperature difference, the controllercan operate the motorand the evaporator fanto further increase the speed of the motorto direct greater amounts of ambient airover the coilsfor the evaporator. It is contemplated that further increases in the speed of the motorcan be utilized where needed, depending on the design of the heat pump systemand the motorof the evaporator fan. When the surface temperatureincreases at the increased rate, the rate of changeof the surface temperaturefor the evaporatorwill be greater than the rate of changeof the media temperaturefor the waterto be heated within the reservoir. When the surface temperatureincreases relative to the media temperatureto define the threshold difference, the temperature differenceagain defines the standard operating conditionand the evaporator fanis again operated at the base speed setting.

In the various aspects of the device, the motoris a variable speed motor that can be controlled, typically by the controller, to operate according to the plurality of speedsthrough discrete steps, or through a gradual increase and decrease of speeds. In certain aspects of the device, the motorfor the evaporator fanis a variable speed motor with infinitely variable speed control. In such an aspect of the device, the motorcan be operated through the plurality of speeds, which can include a range of precise and continuously variable speed settings.

Referring now to, the controlleroperates the motorfor the evaporator fanto define the plurality of speedsof the evaporator fan. Under the standard operating condition, the controlleroperates the motorfor the evaporator fanat a base speed setting. As discussed herein, for the fan speed control system, the controllercan operate the motorof the evaporator fanbased on the rate of changeof the surface temperature and at least partially based upon the temperature difference and the rate of changeof the temperature differencebetween the media temperatureof the waterwithin the reservoirand the surface temperatureof the coilsfor the evaporator. Where the surface temperaturechanges at the decreased rateand the temperature differenceincreases minimally, the controllercan operate the evaporator fanat a medium speed settingthat is faster than the base speed setting. Additionally, where the surface temperaturechanges at the decreased rateand the temperature differenceincreases at a higher rate, the controllercan operate the motorfor the evaporator fanat the high speed setting, which is faster than the medium speed setting, to greatly increase the amount of ambient air, and heat, moving over the surfaceof the evaporator. When the temperature differencereturns to the standard operating condition, the controllercan instruct the motorfor the evaporator fanto return to the base speed settingindicative of a normal operation of the heat pump system.

Referring again to, the water heating applianceincludes an outer housingthat encloses the various components of the heat pump system, the reservoirand other components of the water heating appliance. The water heating applianceincludes an upper housingthat encloses components of the heat pump system. The water heating appliancealso includes a lower housingthat encloses the reservoirfor storing waterand maintaining the temperature of the heated water. The upper housingof the water heating applianceincludes an air inletand an air outletthat are each positioned, typically, within a top wallof the upper housing. These apertures provide for the expedient movement of process air, typically in the form of ambient air, through the upper housingto be acted upon by the evaporator fanand the evaporatorof the heat pump system.

Referring again to, the heat pump systemincludes the evaporatorthat receives the thermal exchange media, typically from an expansion device. The thermal exchange medialeaving the evaporatoris heated within the coilsof the evaporatorby absorbing the heatfrom the ambient air. The thermal exchange media, containing the absorbed heatfrom the ambient air, is then directed to the compressor. The thermal exchange medialeaving the compressoris pressurized, heated, and typically in the form of gas. This form of the thermal exchange mediais then directed to the condensing portionof the heat pump system, such as the coilsof the condensing portion, where heatfrom the thermal exchange mediais rejected into a separate media. In the case of the water heating appliance, the condensing portionis typically in the form of the coilsof the condensing portionthat act on the reservoir. The media being heated is waterto be heated in the reservoir, or a conduit of waterthat is heated as it moves through the condensing portionof the heat pump system. After leaving the condensing portionof the heat pump system, the thermal exchange mediais delivered to the expansion devicewhere the thermal exchange mediais converted to a cooled liquid form. This cooled liquid form of the thermal exchange mediais then delivered into the evaporatorof the heat pump systemto receive additional amounts of heatfrom the ambient air. This heatcan then be transferred to the condensing portionof the heat pump system. This process continues to move heatfrom the ambient airand to the waterwithin the reservoir.

Typically, the compressor, the evaporator, and the expansion deviceare located within the upper housingof the water heating appliance. The condensing portionof the heat pump systemis typically located in the lower housingproximate the reservoirof waterto be heated. Other locations of these components are also contemplated.

Referring again to, the evaporatorof the heat pump systemis positioned adjacent to the blowersuch that the process air, typically in the form of the flow of ambient air, can move through the evaporator. In this configuration, heatis extracted from the process airand delivered into the thermal exchange mediavia the evaporator. The even movement of process airthrough the evaporator, which is typically generated by an air funnel, ensures that the process airmoves through the evaporatorat an even and consistent rate. In this manner, a maximum amount of heatcan be extracted from the process airdelivered into the thermal exchange media.

According to the various aspects of the device, it is contemplated that the thermal exchange mediacan be in the form of refrigerant, water, air, glycol, and other similar substances that are effective at absorbing and releasing heatwithin a heat pump system.

The temperature sensing systemfor the heat pump systemincludes a plurality of temperature sensorsthat are positioned in communication with portions of the heat pump system. For monitoring the surface temperatureof the coilsfor the evaporator, an evaporator sensoris positioned on an upstream portion of the coilsfor the evaporator, near the expansion device. For monitoring a media temperatureof the waterwithin the reservoir, a media sensoris positioned on or within the reservoirfor measuring the media temperaturewithin the reservoir. The waterwithin a lower portionof the reservoircan be used for consistently and accurately monitoring the media temperatureof the water. As the heat pump systemoperates, the waterwithin the reservoiris heated. Through the process of convection, the warmer watertends to rise within the reservoirand cooler watertends to descend within the reservoircausing a mixing of the heated and cooled waterwithin the reservoir. By monitoring the media temperatureof the waterwithin the lower portionof the reservoir, a more accurate temperature reading is provided for use in the fan speed control system. Additional temperature sensorscan be located within an airflow pathfor monitoring a temperature of the ambient air, on a position of the refrigerant pathupstream of the compressor, a position of the refrigerant pathdownstream of the compressor, an upper portionof the reservoir, and other sections of the heat pump system. For purposes of implementing an aspect of the fan speed control system, as described herein, the evaporator sensorand the media sensorare typically utilized for measuring the temperature differencebetween the media temperatureof the waterwithin the reservoirand the surface temperatureof the coilsfor the evaporator.

Referring again to, during operation of the heat pump system, the controlleroperates the motorof the evaporator fanthrough the plurality of speeds. As discussed herein, under the standard operating condition, the motoroperates at the base speed settingof the plurality of speeds. When the rate of changeof the surface temperatureis defined by the decreased rate, and when the temperature differenceexceeds the threshold differencebetween the media temperatureand the surface temperatureto indicate a frost condition, the controlleroperates the motorat an increased speedto increase the flow of ambient airacross the coilsfor the evaporator. The controlleroperates the motorat this increased speeduntil the temperature differencereturns to the threshold difference, or below the threshold difference, that is indicative of the standard operating condition. Stated another way, when the temperature differencereturns to the standard operating condition, the controllerwill again operate the motorfor the evaporator fanat the base speed setting.

According to the various aspects of the device, as illustrated in, fluctuations occur in the media temperatureand the surface temperature. Typically, these changes happen contemporaneously such that the temperature differencebetween the media temperatureand the surface temperatureremains at a generally consistent amount. As exemplified in, the center of the graph is indicative of a draw of waterfrom the reservoir. After this draw of wateroccurs, additional waterfrom a municipal water supply, well, or other outside source is added to the reservoir. This addition of water decreases the media temperaturesuch that the heat pump systemactivates to increase the temperature of the water. During this activation of the heat pump system, the surface temperatureof the coilsfor the evaporatorand the media temperatureof the waterwithin the reservoirboth increase, with the media temperaturegenerally increasing at a faster rate. Under the standard operating condition, this similar rate of increase is typical and produces the temperature differencebeing at or below the threshold difference, as shown on the left half of the graph.

During operation of the water heating appliance, fluctuations in the surface temperaturecan be severe or drastic when measured over short periods of time, such as seconds or approximately one minute. To account for these drastic localized changes, the controllercan calculate averages of the surface temperatureto arrive at the surface temperatureand the rate of changeof the surface temperature. It is contemplated that the surface temperaturecan be measured frequently, such as from approximately every few seconds to approximately every minute. Several of these measurements can be averaged together to arrive at the surface temperatureand the rate of changeof the surface temperature. The averaging calculation can be performed for approximately every five minutes to approximately every 30 minutes to arrive at the surface temperatureand the rate of changeof the surface temperature.

Referring again to, during a frost condition, which is exemplified, in a non-limiting manner on the right side of the graph, the surface temperatureof the coilsfor the evaporator, sometimes referred to as the saturated suction temperature or the evaporating temperature, increases only marginally. This marginal increase in the surface temperature can be indicative of an onset of or precursor to a frost condition. As the condition persists, the surface temperaturebegins to decrease, which can be indicative of the frost condition. At the same time, the media temperatureof the waterwithin the reservoirincreases. This creates a greater temperature differencebeyond the threshold difference. Stated another way, the rate of changeof the surface temperature(the decreased rate) and the rate of changeof the media temperature(increasing) diverge from one another resulting in a consistently increasing temperature difference. The diverging rates of changeand the increased temperature differenceare each indicative of the frost condition. This condition, in combination with the decreasing rate of the surface temperaturebelow the threshold rate, can activate the controllerto operate the evaporator fanat one of the medium speed settingor the high speed setting. Operation of the medium speed settingor the high speed settingcan depend upon the decreasing rate of the surface temperatureand the rate of changeof the temperature difference, as well as the degree of variance between the surface temperatureof the coilsand the media temperatureof the waterwithin the reservoir. A greater rate of changein the temperature difference, resulting in a greater variation between the surface temperatureof the coilsand the media temperatureof the water, can cause the controllerto activate the high speed settingof the motor. Where the temperature differenceis only minimally beyond the threshold difference, the controllercan operate the motorfor the evaporator fanat the medium speed setting.

Typically, the plurality of speedsof the motorfor the evaporator fanincludes the base speed setting, the medium speed settingthat is faster than the base speed setting, and a high speed settingthat is faster the medium speed setting. It is contemplated that additional speed settings can be included within the fan speed control systembased upon the design of the heat pump systemand the water heating appliance.

Referring again to, during operation of the heat pump system, the media sensorand the evaporator sensormonitor the temperatures of the waterwithin the reservoirand the surface temperatureof the coils, respectively. During the standard operating condition, the temperature differencebetween the media temperatureand the surface temperaturemaintains a generally consistent temperature differencewithin the threshold difference. In certain conditions, the surface temperaturemay have a rate of changethat is the decreasing rate, and the media temperatureexperiences a similar decrease, which is typically at a more accelerated rate of change. An example of such a condition may be where there is a draw of waterfrom the reservoirand cool or cold wateris added to the reservoirto replace the used water. In such a situation, the frost conditionis not present and the controllerwill maintain the motorat the base speed setting.

Referring again to, under certain conditions, this temperature differencebetween the surface temperatureand the media temperaturecan increase. Typically, this increase in the temperature differenceoccurs when airflowthrough the evaporatoris impeded by some obstruction. In the case of a frost condition, the formation of ice crystals on the coilsfor the evaporatorcan impede the flow of ambient airthrough the evaporator. When ambient airis unable to move across sections of the evaporator, heatmay not be absorbed from ambient airinto thermal exchange mediavia the coilsof the evaporator. This results in the surface temperatureof the coilsdecreasing, or not increasing at an appropriate rate, due to the decreased amount of heatsurrounding at least some portions of the evaporator. This condition can become exacerbated as lesser amounts of ambient airare able to move past portions of the evaporatorand ice crystals may form more rapidly around more of the evaporator. This can result in the rate of changein the surface temperaturedefining a decreased rate. Contemporaneously, the media sensorof the temperature sensing systemmay indicate a consistent temperature or slightly increasing temperature of the waterwithin the reservoir. Conversely, the surface temperatureof the coilswill tend to decrease at the decreased rate, thereby increasing the temperature differencebetween the media temperatureand the surface temperature, and possibly the rate of changeof the temperature difference.

Referring again to, at the initial stages of this increase in the temperature differencebetween the media temperatureand the surface temperature, and the rate of changeof the surface temperaturebeing the decreasing rate, the fan speed control systemcan be operated where the controlleroperates the motorfor the evaporator fanat one of the increased speeds. Initially, the controllermay operate the motorat the medium speed settingto moderately increase the amount of ambient airmoving across the coilsfor the evaporator. The increased flow of ambient airalso results in an increased amount of heatthat can be absorbed by the evaporator. As described herein, this increased amount of heatmoving over the coilsand being absorbed by the evaporatoralso increases the surface temperatureof the coilsfor the evaporator. Using this system, the increased surface temperatureresults in preventing the formation and/or the melting of ice crystals that may have accumulated on the surfaceof the coilsfor the evaporator.

Referring again to, where the medium speed settingmay be inadequate for mitigating the increase in temperature differencebetween the media temperatureand the surface temperature, the controllercan operate the motorat the high speed settingto greatly increase the flow of ambient airmoving across the evaporator. This greater increase of ambient airresults in a greater amount of heatthat can be absorbed by the evaporator, thereby further increasing the surface temperatureof the coilsfor the evaporator. As discussed herein, this has the effect of decreasing the temperature difference. When the temperature differencehas returned to within the threshold difference, indicative of the standard operating condition, the controllercan again operate the motorfor the evaporator fanat the base speed setting.

Referring to, according to the various aspects of the device, the heat pump systemfor the water heating applianceincludes the heat exchange loop that includes the evaporatorthat absorbs heatfrom ambient air. The evaporator fandirects the ambient airacross the coilsfor the evaporator. The compressoris used for directing the thermal exchange mediathrough the refrigerant path. The compressorreceives the heat, via the thermal exchange media, from the evaporatorand delivers this heatto the waterto be heated within the reservoir. The controllermonitors the temperature differencebetween the media temperatureof the waterto be heated within the reservoirand the surface temperatureof the surfaceof the coilsfor the evaporator. The measurement of the media temperatureand the surface temperaturedefines the temperature difference. An increase in the temperature differencecan be indicative of the frost condition. In response to the temperature differenceexceeding the threshold differenceand reaching the frost condition, the controllerincreases the speed of the motorfor the evaporator fanto deliver additional ambient airacross the surfaceof the coilsfor the evaporator. The additional ambient airoperates to increase the surface temperatureof the coils, thereby decreasing the temperature differenceto be within the standard operating condition, the temperature differenceof the standard operating conditionbeing less than the temperature differenceof the frost condition.

According to various aspects of the device, the heat pump systemcan include the air funnelthat is configured to maintain a consistent and even air pressureand a consistent and even air velocitywithin the evaporator. To maximize the capture of heatfrom within the evaporatorduring the standard operating conditionand during operation of the fan speed control systemfor mitigating the frost condition, the even and consistent movement of process airthrough the entirety of the evaporatoris useful for preventing and mitigating a frost condition. This even and consistent movement of process airserves to increase the efficiency of the heat pump systemto deliver heatinto the waterto be heated within the reservoir. The air funnel, as described more fully herein, includes a series of sections that operate sequentially to maintain the substantially even and consistent air pressurewithin the evaporator, and to also maintain a substantially consistent decline of air pressureof the process airas it moves between a downstream surfaceof the evaporatorand through a portof the air funnel, and into the evaporator fan. Typically the evaporator fanincludes the motorthat rotates the blowerwithin a blower housing. During operation of the evaporator fan, the air funnelassists in directing the process airmoving between an upstream surfaceof the evaporatorand the downstream surfaceof the evaporator. As described herein, the air funnelmaintains a consistent and even air pressureand air velocitywithin the evaporator. This configuration minimizes the occurrence of a pressure drop of the process airwithin the evaporator. The existence of a pressure drop can be indicative of a lack of airflowwithin a portion of the evaporator. In this manner, by maintaining the airflowto be consistent and even, the entirety of the evaporatoror substantially all of the evaporatorcan be utilized for transferring heatfrom the process airand into the thermal exchange mediafor moving through the evaporatorof the heat pump system.

Referring again to, the air funnelthat is attached to the evaporatorincludes a transition sectionthat engages the evaporator. This transition sectionincludes a pressure maintenance portionand a pressure regulation portion. The pressure maintenance portionof the air funnelis positioned around the evaporatorsuch that the pressure maintenance portionoperates to maintain the air pressureand air velocityof the process airmoving through the evaporatorto be at a consistent and even rate. Subsequently, the pressure regulation portionof the transition sectionoperates on the process airleaving the evaporatorto manage the transfer of the process airbetween the downstream surfaceof the evaporatorand the portthat is coupled with and leads into the blowerfor the evaporator fan. The geometry of this pressure regulation portionof the air funnelcollects the flowof process airfrom the rectangular evaporator and generates a consistent and even decrease in air pressure, as well as a consistent and even increase in air velocity, of the process airas the process airtransitions to the rounded port, typically in the form of a rounded port, that leads to the evaporator fan. This phenomena, as commonly referred to as a Venturi effect, is caused by a narrowing of a flowof the process airmoving through space. The pressure regulation portionof the air funnelmanages the Venturi effect to ensure that, as the process airmoves through the pressure regulation portion, each section of the flowof process airexperiences a similar decrease in air pressureand increase in air velocityas it approaches the port. This even and consistent movement of the process airminimizes pressure drop and, in turn, minimizes locations where the evaporatoris not absorbing a sufficient amount of heatto prevent a frost condition.

Referring again to, the air funnelalso includes a converging sectionthat is downstream of the transition sectionand forms the rounded portthat directs the process airinto the blower. This converging sectionof the air funneldirects the process airfrom the transition sectionand into an inner perimeterof the port. Once through the port, the process airis moved by the blowerthrough the air outletand out of the upper housing.

Referring again to, the pressure maintenance portionof the air funnelextends across a depthof the evaporatorbetween the upstream surfaceof the evaporatorand the downstream surfaceof the evaporator. It is contemplated that this pressure maintenance portionis substantially rectangular to match the profile of the evaporator. In certain aspects of the device, the pressure maintenance portioncan also extend at least partially into the space of the air funnelthat is immediately adjacent to the downstream surfaceof the evaporator. This pressure maintenance portionof the air funnelcan be defined by a flangeof the air funnelthat engages the rectangular outer edgeof the evaporator. This flangecan engage a single surface of the evaporator. Additionally, the flangecan extend around multiple surfaces of the outer edgeof the evaporatorto encircle a portion of the evaporatoror the entirety of the outer edgeof the evaporator.

According to various aspects of the device, the pressure regulation portionof the air funnelincludes a concave shape that is positioned to extend from the downstream surfaceof the evaporator. This pressure regulation portionincludes a cross-sectional profile that is generally in the shape of a parabolic arc that proceeds from the rectangular downstream surfaceof the evaporatorand toward the circular converging sectionthe air funnel. This parabolic curvature of the pressure regulation portionoperates to gradually and evenly decrease the air pressureof the process air, thereby managing the Venturi effect within the air funnel. Additionally, the pressure regulation portionmaintains the flowof process airbetween the rectangular configuration of the evaporatorand around the configuration of the converging section.

By managing the Venturi effect, sections of the flowof process airare prevented from moving at a greatly accelerated rate or decelerated rate, relative to adjacent portions of the flowof process air. Undesirable and isolated changes in air pressureand air velocitymay result in a section of the process airthat experiences a pressure drop. These sections of pressure drop with the process aircan have an impact upstream that may result in an uneven flowof process airthrough the evaporator. Additionally, as described herein, pressure drop within a portion of the coilsof the evaporatormay result in the initiation of the frost condition. This pressure drop may also result in a decreased ability to mitigate a frost conditionwithin the evaporator. By managing the Venturi effect to create a consistent decrease in air pressureand a consistent increase in air velocity, the process airis able to move evenly and consistently through the entirety of the coilsfor the evaporatorto efficiently transfer heatfrom ambient airand into the thermal exchange mediawithin the coilsof the evaporator. The ability of the air funneland the portions thereof operates to manage the Venturi effect, as described herein, through operation of the evaporator fanthough the plurality of speedsof the evaporator fan.

Referring again to, the pressure regulation portionof the transition sectionmoves into the converging sectionof the air funneland transitions from the concave portion of the air funnelto a convex portion of the air funnel, which is located in the converging section. This convex portion of the converging sectionof the air funnelfurther directs the flowof process airthrough the portand into the blower. Again, this transition of the air funnelbetween the pressure regulation portionand the converging sectionof the air funnelmaintains a consistent and even decrease of air pressure, as well as consistent and even increase in air velocityas the flowof process airmoves through the portand into the blower housing.

In certain aspects of the device, the converging sectionof the air funnelcan be positioned in an eccentric position with respect to the transition section. Stated another way, the converging sectionand the portcan be positioned in an off-axis or off-center position within the air funnelwith respect to the transition sectionas well as the evaporator. The curvature of the concave portion of the pressure regulation portiondirects the process airto maintain a consistent and even increase in air velocity, and corresponding consistent decrease in air pressure.

To accommodate the off-axis position of the port, the pressure regulation portionincludes a non-symmetrical curvature of the concave portion. This non-symmetrical configuration of the concave portion directs the process airin a consistent increase in air velocityand corresponding decrease in air pressure. In this manner, the curvature of the concave portion can define a steeper curve on the short side of the air funnel, the short side being that side of the air funnelwhere the portis closer to the outer edgeof the evaporator. Similarly, for the long side of the air funnel, that portion of the concave portion where the portis farther from the outer edgeof the evaporatorcan have a shallower curve.

In certain aspects of the device, the portand the converging sectioncan be centrally located within the air funnel. In such configuration, the evaporator fanof the bloweris also centrally located within the air funnel.