Air-source heat pump

Abstract

An air-source heat pump is provided, comprising a compressor (332) for compressing a refrigerant, an air heat exchanger (320) for extracting energy from ambient air during a heating operation mode, a drip tray for collecting condensates dripping from the air heat exchanger, and a fan (324) for generating airflow through the air heat exchanger. Here, the air heat exchanger (320) includes a liquid subcooler (23) at its bottom, configured to receive a liquid refrigerant and supply it to an expansion valve (316) positioned so that the refrigerant passes through before passing through an evaporator at the top of the air heat exchanger (320), the liquid subcooler (23) being at least partially housed in a drip tray and shielded from the airflow.

Description

Technical Field

[0001] The present invention relates to an air source heat pump and a method for defrosting an air source heat pump.

Background Art

[0002] According to Directive 2012 / 27 / EU, buildings account for 40% of final energy consumption and 36% of CO2 emissions. The 2016 European Commission report "Mapping and analysis of the current and future (2020-2030) heating and cooling fuel deployment (fossil fuels / renewable energy)" concluded that in EU households, heating and hot water provision alone account for 79% (192.5 Mtoe) of total final energy consumption. The European Commission also reports that: "According to 2019 Eurostat figures, around 75% of heating and cooling is still generated from fossil fuels, and only 22% is generated from renewable energy. To achieve the EU's climate and energy targets, the heating and cooling sector must significantly reduce its energy consumption and cut the use of fossil fuels. Heat pumps that extract energy from air, ground or water are regarded as potentially important contributors to addressing this issue. Since only a very small proportion of households have access to water bodies to support the use of heat pumps that extract energy from water, and the cost and space requirements for installing ground heat exchangers are very significant, installing an air source heat pump is generally cheaper and more convenient. It is also generally recognized that air source heat pumps are a better alternative to existing gas central heating boilers.

[0003] However, air-source heat pumps have one drawback not shared by heat pumps that extract energy from water or ground: in warm and cold climates, when operating the heat pump to extract energy from ambient air ("heating mode"), the air heat exchanger of the heat pump needs to be periodically defrosted. An air heat exchanger is a heat exchanger in which heat from ambient air is transferred to a liquid refrigerant in heating mode. Typically, a matrix of finned tubes (more commonly conduits) receives the cold liquid refrigerant, and ambient air moves over the tubes by the action of a fan or impeller. In heating mode, energy is extracted from the ambient air because the liquid refrigerant is colder than the ambient air, and the liquid refrigerant evaporates as a result of its temperature rise, causing the ambient air temperature to drop. Therefore, water vapor carried by the ambient air tends to condense on the surface of the air heat exchanger. If the ambient air temperature is low enough, the water condensing on the surface of the air heat exchanger will freeze and form ice. Ice buildup reduces the heat transfer efficiency of the air heat exchanger, and significant ice buildup can clog gaps between adjacent conduits in the air heat exchanger, leading to loss of airflow and thus a further decrease in efficiency. Therefore, air-source heat pumps are configured to occasionally perform what is known as a thaw cycle (which actually involves briefly operating the heat pump in a cooling mode where heat is released from the refrigerant through the air heat exchanger to the surroundings), during which time relatively warm refrigerant is supplied to the air heat exchanger to melt the ice and thus restore the efficiency of the air heat exchanger. The frequency of thaw cycle events can be every 35 minutes, for approximately 10 minutes each, but depends, among other things, on ambient conditions and the amount of heat load the system is trying to supply. Thus, a thaw cycle involves the reverse of the normal energy extraction cycle used in heating mode, where the heat pump operates in reverse and energy is transferred from the home (e.g., from heated spaces within the home, or from hot water in a space heating system or household hot water supply) to the air heat exchanger and thus to the surroundings.

[0004] During normal operation, condensate forms on the evaporator surface of the outdoor heat exchanger and flows down the outside of the evaporator. Similarly, during the thawing cycle, frozen condensate accumulated on the evaporator melts and flows down the outside of the evaporator. For this reason, a drip tray is provided below the air heat exchanger as part of the heat pump assembly (optionally within the heat pump body) to capture the condensate and guide it to an appropriate discharge point to avoid adverse effects on the product or the surrounding environment. For example, if not properly managed, there is a risk of condensate entering parts of the heat pump that are not suitable for contact with condensate, such as electrical components. Also, the accumulation of condensate puddles around or below the heat pump in areas such as patios and walkways can freeze, posing a safety hazard to nearby residents.

[0005] Under certain conditions during normal operation, frost and ice coatings may form on the evaporator surface, causing condensate inside and near the drip tray beneath the evaporator to freeze. This can obstruct the flow of condensate within, through, or out of the drip tray, leading to problems caused by disrupted condensate management.

[0006] The present invention aims to address this problem at least partially and to reduce the potential problems caused by condensation. [Overview of the Initiative]

[0007] According to a first embodiment, an air source heat pump is provided, comprising a compressor for compressing a refrigerant, an air heat exchanger for extracting energy from ambient air during a heating operation mode, a drip tray for collecting condensates dripping from the air heat exchanger, and a fan for generating an airflow through the air heat exchanger, wherein the air heat exchanger includes a liquid subcooler at the bottom configured to receive a liquid refrigerant and supply the refrigerant to an expansion valve positioned so that the refrigerant passes through before passing through an evaporator at the top of the air heat exchanger, the liquid subcooler being at least partially housed in the drip tray and at least partially shielded from the airflow.

[0008] According to a second embodiment, an air source heat pump is provided, comprising a compressor for compressing a refrigerant, an air heat exchanger for extracting energy from ambient air during a heating operation mode, a drip tray for collecting condensates dripping from the air heat exchanger, and a fan for generating an airflow through the air heat exchanger, wherein the air heat exchanger includes at its bottom a liquid subcooler configured to receive a liquid refrigerant and supply the refrigerant to an expansion valve positioned so that the refrigerant passes through before passing through an evaporator at the top of the air heat exchanger, The liquid supercooler is at least partially housed within the drip tray by being contained in a trough or well, and is shielded from airflow.

[0009] According to a third embodiment, an air source heat pump is provided which includes a compressor for compressing a refrigerant and an air heat exchanger for extracting energy from ambient air during a heating operation mode, wherein the air heat exchanger includes a liquid subcooler at the bottom configured to receive a liquid refrigerant and supply the refrigerant to an expansion valve positioned so that the refrigerant passes through before passing through an evaporator at the top of the air heat exchanger. Here, the heat pump is A drip tray for collecting condensate dripping from the air heat exchanger, The system includes a fan for generating airflow through an air heat exchanger, where at least a portion of the liquid subcooler is housed in a drip tray, the drip tray shielding a portion of the subcooler from the airflow.

[0010] An apparatus according to any of the first to third embodiments reduces the likelihood of condensate freezing in the drip tray and reduces the likelihood of obstruction of condensate flow.

[0011] In an air-source heat pump according to any of the first to third embodiments, one or more structures or formations may be provided to shield the subcooler from the airflow. Together, one or more structures or formations may define a cavity in which the subcooler is housed, the cavity communicating with a drip tray. One or more structures may comprise at least one flange, optionally at least one pair of opposing flanges. One or more structures may comprise grooves or recesses formed in the floor of the heat exchanger housing. One or more structures or formations may form part of a drip tray structure for collecting / managing condensate outflow.

[0012] In an air-source heat pump according to any modification of the first to third embodiments, the heat pump may be housed in a housing made of plastic material, the drip tray may be formed integrally with the housing, and optionally one or more structures may be formed integrally with the housing. The plastic housing may comprise a plastic molded product, the drip tray may be formed as part of the molded product, and optionally one or more structures may be formed as part of the molded product. The plastic molded product may house an air heat exchanger and optionally a compressor. Such a device can help reduce manufacturing costs while providing advantages in handling condensates.

[0013] In an air-source heat pump according to any modification of the first to third embodiments, the subcooler may comprise a plurality of tubes of different lengths that together form one or more circuits for refrigerant flow.

[0014] One or more structures or formations can provide at least partial shielding from airflow to all of the tubes of multiple lengths.

[0015] Alternatively, one or more structures or formations can shield only a subset of tubes of a certain length from airflow. The subset may comprise at least half of the plurality, or optionally a majority of the plurality.

[0016] In an air-source heat pump according to any modification of the first to third embodiments, the air heat exchanger may be a finned structure in which individual fins function both as a liquid subcooler and as an upper part. The individual fins may be arranged so that when condensate is formed from water vapor in the atmosphere, the condensate flows down the fins from the upper part towards the liquid subcooler. [Brief explanation of the drawing]

[0017] Next, embodiments of the present invention will be described as merely examples with reference to the attached drawings. [Figure 1] Figure 1 schematically shows an air-source heat pump operating in heating mode. [Figure 2] Figure 2 schematically shows the air source heat pump of Figure 1 operating in defrost mode. [Figures 3a-3d] Figures 3a-3d are schematic partial vertical cross-sectional views of the lower end of the air heat exchanger and a portion of the support structure of a heat pump according to one embodiment of the present invention. [Figure 4] Figure 4 schematically illustrates a heat pump according to one aspect of the present invention. [Modes for carrying out the invention]

[0018] Figure 1 schematically shows an air-source heat pump 10 operating in heating mode. The main mechanical components of the heat pump are shown, but for clarity, electrical, sensing, and control elements, as well as connections, including the heat pump's controller or processor, are omitted. Starting from the lower right corner of the figure, cold liquid refrigerant is pushed out from the receiver 12 under the action of the compressor 32, along a conduit 14 that passes through the lower part 23 of the air heat exchanger 20 to the heating expansion valve 16, where the lower part 23 functions as a subcooler device during heating mode. The upper part of the air heat exchanger 20, labeled 21, functions as a refrigerant evaporator in heating mode.

[0019] The conduit 14 has an open end 15 that is immersed in the liquid refrigerant in the receiver 12 when in use, and liquid refrigerant, not refrigerant vapor, is supplied from the reservoir 12 to the conduit 14.

[0020] During heating mode, passing the warm liquid refrigerant from the receiver or liquid reservoir 12 through the subcooler device 23 provides some degree of subcooling of the refrigerant to ensure that the refrigerant is completely condensed before it is expanded through the heating expansion valve 16. A small amount of subcooling is beneficial to the operation of the refrigerant cycle. Excessive subcooling is detrimental to efficiency because the evaporator 21 must provide a large heat input to the refrigerant before the process of evaporating the refrigerant begins.

[0021] In the heated expansion valve 16, the pressure of the refrigerant decreases as it passes through a small opening, lowering the boiling point of the refrigerant. Depending on the temperature of the refrigerant at the expansion valve inlet and the pressure of the refrigerant at the expansion valve outlet, some of the refrigerant may spontaneously evaporate, resulting in a decrease in the temperature of the refrigerant, and the refrigerant exiting the expansion valve as a mixture of liquid and vapor. From the expansion valve 16, the refrigerant enters the distributor 18, where a single input conduit is coupled to multiple output conduits, each output conduit supplying conduits to the evaporator 21.

[0022] A one-way valve 50 is provided in parallel with the heating expansion valve 16, which is oriented to permit flow from the distributor 18 to the conduit 14 (the direction in which refrigerant flows during the cooling operation mode) and prevent direct flow of refrigerant from the conduit 14 to the distributor, so that in the heating mode, refrigerant must pass through the heating expansion valve 16 to reach the distributor 18. As will be appreciated by those skilled in the art, the heating expansion valve 16 (like other expansion valves of the heat pump) is controlled by the processor of the heat pump to achieve a target value of refrigerant superheat degree according to the current operating conditions at that time.

[0023] A filter drier 51 may be provided in the flow path to the heating expansion valve 16, and if present, it is also bypassed by the flow through the one-way valve 50 during cooling and defrosting.

[0024] In one variant, the distributor 18 may include three flow paths, namely a single input conduit 17 having a small internal fixed orifice (not shown), a plurality of output conduits (indicated by reference numeral 19), and an internal bypass conduit. In the heating mode, refrigerant flows through the heating expansion valve 16 into the single input conduit 17 of the distributor 18, and exits from the plurality of output conduits 19 through the small internal fixed orifice. In the heating mode, there is no flow through the internal bypass conduit. Expansion of the refrigerant occurs through the heating expansion valve and the fixed orifice. In the cooling mode, refrigerant can flow out of the plurality of output conduits 19 through the internal bypass conduit and through the one-way valve 50, bypassing the internal fixed orifice and the heating expansion valve 16 such that the heating expansion valve 16 and the internal fixed orifice of the distributor 18 have a negligible effect in the cooling mode. In another variant, the distributor may be formed without the small internal fixed orifice and the internal bypass conduit.

[0025] The evaporator 21 is schematically shown as having just four conduits traversing the air heat exchanger, but in practice, more such conduits are provided, and each typically has thermally conductive fins to improve heat transfer from the air to the refrigerant in the conduit. The heat pump includes a motor-driven fan 24 that moves ambient air over the evaporator 21.

[0026] In heating mode, the refrigerant in the evaporator 21 is heated by energy absorbed from the ambient air, causing the refrigerant to change state to vapor, which can be further heated by absorbing energy from the air, potentially superheating the vapor. The evaporated refrigerant exits the evaporator 21 via a manifold or collector 26 that delivers the refrigerant to the first port of the four-way valve 30, towards the return conduit 28 supplying port 1. The evaporated refrigerant exits the four-way valve 30 via port 2 and flows from there to the compressor 32. In the compressor, the low-pressure received and heated vaporized refrigerant is compressed into high-pressure vapor, and the temperature of the refrigerant increases further during the compression process. The refrigerant returns from the compressor 32 through the four-way valve 30, enters via port 3, exits via port 4, and is supplied to the heat exchanger matrix (not shown) in the heating system heat exchanger 34. The heating system heat exchanger 34 may be a heating system heat exchanger in which energy from a high-temperature refrigerant is transferred to water (or some other suitable working fluid in the case of ambient heating), as shown in the figure, and is used, for example, for ambient heating via a central heating system, or for providing hot water for household or industrial use. The high-temperature refrigerant enters the heat exchanger 34 through port 36, condenses, and then exits through port 38 as cooled refrigerant. The water for heating enters the heat exchanger 34 through port 40 on the low-temperature side of the heat exchanger 34 and exits through port 42 on the high-temperature side of the heat exchanger 34.

[0027] Within the heating system heat exchanger 34, the refrigerant condenses from vapor to liquid, transferring heat to the water in the water circuit of the heat exchanger 34. From port 38, the cooled liquid refrigerant proceeds to a one-way valve 54 oriented to allow flow from the heating system heat exchanger 34 to the liquid reservoir 12. Thus, this one-way valve 54 acts as a bypass for another cooling expansion valve 44, which is provided to expand the refrigerant as it flows from the liquid reservoir 12 towards the heating system heat exchanger 34 in the cooling operation mode (and therefore also during thawing of the air heat exchanger). In the heating mode, the refrigerant can flow through the one-way valve 54, bypassing the cooling expansion valve 44 with minimal restriction, and as a result, the cooling expansion valve 44 has a negligible effect in the heating mode. The liquid refrigerant then returns to the liquid reservoir 12, which is the starting point of the process. It will be understood that the heating system heat exchanger 34 may use the refrigerant to heat air instead of water (e.g., for warm air space heating), but the principle remains the same.

[0028] Figure 1 also includes an additional heat exchanger 46 supplied from the refrigerant conduit 14 via an additional expansion valve 48. This additional heat exchanger 46 is optional, but preferably, provided as a means to cool (and control the temperature of) an electric inverter (not shown) that supplies power to the compressor and various other electrical components and systems of the heat pump. The additional heat exchanger 46 may include a heat sink thermally coupled to the inverter and, optionally, to other electronic and power components of the heat pump. The cooling provided by the additional heat exchanger 46 helps ensure the proper operation of the inverter and other electronic components, extends their lifespan, and captures what would otherwise be waste heat, supplying it to the refrigerant, which is then supplied to the compressor 32, thus further contributing to the efficiency of the heat pump. The function of the inverter cooling expansion valve and inverter cooling heat exchanger and the direction of flow through them are independent of and unrelated to the operating mode (i.e., heating, cooling, defrosting). The inverter cooling expansion valve is controlled by the heat pump processor to adjust the refrigerant state passing through the inverter cooler heat exchanger, thereby achieving the desired cooling effect, such as the target value of the inverter drive temperature.

[0029] When the heat pump in Figure 1 is operated on a cool day in a temperate climate (e.g., 1–10°C), water vapor in the ambient air may condense in the evaporator 21 and then turn into ice. The accumulation of ice on the evaporator 21 restricts the airflow through the evaporator 21 and reduces the efficiency of energy transfer from the ambient air to the refrigerant. The heat pump typically includes either a mechanism for detecting ice accumulation or a mechanism for detecting climatic conditions when ice accumulation is expected, or some other mechanism for ensuring timely thawing and has a processor (e.g., programmed) configured to put the heat pump into thawing mode as needed. Throughout this specification, references to a processor refer to a processor or controller (e.g., a microcontroller or microprocessor) configured or programmed to perform the relevant functions and operations. The processor or controller typically includes and / or is coupled to a memory configuration that stores relevant code, instructions, programs, algorithms, and data to enable the processor to perform the relevant operations, functions, methods, and procedures.

[0030] Although not shown in Figure 1, for the reasons described above, it is preferable to provide a drip tray below the evaporator 21 to collect condensate when the heat pump is operating in heating mode or defrosting mode.

[0031] A sensor 31 for measuring the temperature and pressure of the refrigerant may be provided at the inlet of the compressor 32. Based on the values ​​obtained from these sensors 31, the heat pump processor or controller can determine the state of the refrigerant, particularly the degree of superheating at or just upstream of the compressor inlet.

[0032] Figure 2 corresponds to Figure 1, but shows a heat pump operating in cooling mode, which is also used in defrosting mode, not just heating mode. In cooling mode, the flow of the refrigerant is reversed compared to the flow in heating mode, and this reversal is achieved by controlling the four-way valve 30 so that the output from the compressor 32, received at port 3, flows to port 1 instead of port 4. Thus, the refrigerant heated by the compressor 32 proceeds to the collector 26, and from there to the evaporator 21, instead of passing through the heat exchanger 34. By supplying the evaporator 21 with high-temperature refrigerant, ice deposits can be melted. The cooled refrigerant exits the evaporator 21 via the distributor 18 and returns to the receiver 12 through the one-way bypass valve 50 and the subcooler.

[0033] From the receiver 12, the expanded refrigerant flows out along the conduit 52. The conduit 52 has an open end 53 that is immersed in the liquid refrigerant during use, so that liquid refrigerant, not refrigerant vapor, is supplied from the reservoir 12 to the conduit 52. The refrigerant from the reservoir 12 flows through the cooling expansion valve 44 along the conduit 52 and from there to the port 38 of the heating system heat exchanger 34. In cooling mode, due to the position and orientation of the one-way valve 54, there is no flow through the bypass conduit. The expansion of the refrigerant is achieved via the cooling expansion valve 44. In the expansion valve, the refrigerant passes through a small opening, causing a decrease in pressure and a decrease in the boiling point of the refrigerant. Depending on the temperature of the refrigerant at the expansion valve inlet and the pressure of the refrigerant at the expansion valve outlet, some of the refrigerant may spontaneously evaporate, resulting in a decrease in the temperature of the refrigerant (the refrigerant exits the expansion valve as a mixture of liquid and vapor). The expansion valve may be controlled by the heat pump processor based on data from the input pressure and temperature sensors 31 of the compressor 32.

[0034] The expanded refrigerant flowing through the heating system heat exchanger 34 absorbs heat from the hot water in the heat exchanger (water flowing from port 40 to port 42 during use) and evaporates. The heated vaporized refrigerant exits the heat exchanger through port 36, proceeds to port 4 of the four-way valve 30, and exits through port 2. From port 2 of the four-way valve 30, the refrigerant vapor proceeds to the compressor 32. It is important that the refrigerant reaches the compressor in vapor form because the compressor could be damaged if it receives liquid refrigerant. The compressor compresses the refrigerant, further increasing its temperature, and supplies the refrigerant to port 3 of the four-way switch 30. The refrigerant exits the four-way switch through port 1. Since the input side of the compressor 32 is always at low pressure when the compressor is operating, in cooling mode, the refrigerant continues to flow through the inverter heat exchanger 46 towards the compressor 32, as it did in heating mode, under the control of the heat pump processor.

[0035] The purpose of the distributor 18 is to distribute the refrigerant as evenly as possible to the multiple parallel circuits of the evaporator 21 when operating in heating mode. During reverse operation in defrost mode, the hot refrigerant gas is supplied to the collector 26, which is usually downstream of the evaporator 21, instead of to the distributor 18 as it is in normal "forward" operation in heating mode. In reverse operation, the collector 26 functions to distribute the hot refrigerant gas to the multiple parallel circuits of the evaporator 21. Due to its shape, the collector 26 typically achieves a relatively poor distribution (the collector 26 is generally just a simple large-diameter pipe extending along the length of the end of the evaporator 21, to which the parallel circuits are connected).

[0036] Due to the relatively poor distribution performance of collector 26 and the natural buoyancy effect of the high-temperature refrigerant gas, an imbalance in defrosting performance is typically observed, causing the upper circuit of evaporator 21 to defrost more quickly than the lower circuit. As a result, melted condensate from the upper part of evaporator 21 can flow down over the still-melted ice at the bottom of evaporator 21 and refreeze. This creates a risk that the melted condensate will freeze and block or partially block the drip tray below evaporator 21, thereby preventing further melted condensate from flowing into the drip tray. It also creates a risk that the melted condensate will cause problems with the reliable operation of the heat pump and / or pose health and safety risks in the vicinity of the heat pump.

[0037] The air heat exchanger 20 is proposed to be configured to include a subcooler 23 as a subcooler section located at the base of the heat exchanger 20, and an evaporator section 21 above it. The subcooler section 23 preferably comprises one or more tubes or tube circuits located at the base of the air heat exchanger 20, separated from the tube circuit of the evaporator section 21. The connecting piping of the air heat exchanger assembly is then configured so that the condensed liquid refrigerant from the condenser or receiver 12 is guided through the subcooler 23 at the base of the air heat exchanger 20 assembly before entering the heating expansion valve 16, where it expands, and then distributed to the tube circuit of the evaporator section 21 via a distributor 18. The subcooler 23 provides improved quality of the refrigerant supplied to the evaporator section of the air heat exchanger.

[0038] Moving to Figure 3a, we can see the proposed apparatus intended to reduce the risk of the drip tray freezing during thawing, between thawing cycles, or as a result of cumulative heating-thawing-heating cycles. Figure 3 schematically shows a vertical cross-section of the lower part of the heat exchanger 20, with the bottom receiving the associated drip tray structure 300. As before, the heat exchanger 20 comprises an upper part that functions as an evaporator 21 in heating mode and a lower part 23 that functions as a supercooler in heating mode. The evaporator section 21 consists of a circuit of tubes or conduits 321, and similarly, the supercooler 23 consists of a circuit of tubes or conduits 323A-D. The tubes / conduits of the heat exchanger are typically coupled to fins that generally extend vertically (rather than horizontally) so that condensate can easily flow down the fins and into the drip tray structure 300. The diagram shows only the lower part of the heat exchanger 20, so only 9 rows of tubes / conduits are shown, but in reality, more rows (e.g., 40-70, 45-65, 50-60) are provided. In contrast, supercoolers typically have only a few rows of tubes / conduits, so the 3 rows of tubes shown are more typical of the number of rows actually used (typically fewer than 10 rows are used, e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 row may be used). Depending on the number of rows of tubes / conduits to be accommodated, the fins of the heat exchanger can be in the range of 600-900 mm in length and between 50-75 mm in width (e.g., 55-70, 60-66 mm). The conduits and fins are preferably made of a material with high thermal conductivity, such as copper (or copper alloy) or aluminum (or aluminum alloy). During use, under the operation of the heat pump fan 24, air flows through the heat exchanger 20 from one side of the heat exchanger to the other side, as indicated by the arrows.

[0039] Figure 3a shows four tubular sections 323A-D that constitute the supercooler when viewed in cross-section. In this example, these four tubular sections can provide two flow paths and two return paths, with the flow paths supplying the return paths, and therefore in practice, the four tubular sections shown in cross-section could simply be a cross-section through a single continuous conduit providing the complete flow path of the supercooler. Thus, for example, 323A could be a cross-section through a flow path that runs to the distal end of the supercooler and there connects to return path 323B. Return path 323B may connect to flow path 323C at the proximal end of the supercooler, and flow path 323C may subsequently connect to return path 323D. Return path 323D may then connect to the first flow path of the flow path of the evaporator 21 at the proximal end of the heat exchanger 20. This arrangement is used because it is assumed that the illustrated heat exchanger has all connections on one side of the assembly, and therefore all circuits of the supercooler and evaporator must proceed in one direction, then change direction and return again. However, it is equally possible to have a refrigerant inlet on one side of the heat exchanger and a refrigerant outlet on the opposite side, so the flow path may simply go from one end to the other without returning. Alternatively, it is possible to return from end A to end B, then to end A, then to B (3 passes). Many possible arrangements are possible depending on how the pipes are connected at each end (for example, the flow can be split at any end if desired, so for example, there may be three pipes, and the flow can all go down one, then split at the distal end and return along the other two pipes).

[0040] In this example, which has four tubular sections, it can be seen that the three lowest sections (A, C, and D) are shielded from the airflow caused by the fan. Here, all of these are located entirely within a cavity or recess 301 defined in this case by opposing flanges 302 and 302'. That is, all three of these sections are shielded from the airflow caused by the operation of the heat pump fan. These three tubular sections exist in two rows, and both rows are shielded by flanges. The fourth tubular section 323D, which exists as a third row, is also partially shielded by flange 302, as can be seen from the position of the dashed line 303 indicating the level of the upper edge of flange 302. In this example, the conduits or tubular sections constituting the subcooler are substantially shielded from the airflow caused by the fan by a pair of flanges 302, in that three of the four sections are completely shielded and the fourth section is partially shielded. Of course, the fin portions that constitute the heat exchanger 20 and are adjacent to the associated conduits are also shielded by flanges, but when considering the degree to which the subcooler is shielded from airflow, it is easier to consider only the conduits. Substantially shielded should be interpreted as meaning that at least half of the tubular portions (and / or at least half of the rows) that constitute the subcooler are shielded from the airflow caused by the fan.

[0041] The figure shows the supercooled 23 housed within a groove or recess 301. Here, the recess 301 is formed between a pair of upright flanges 302 and 302' on either side of the drip tray structure 300, but it could equally be formed simply as a groove on the surface without using flanges upright to the surface. The recess 301 communicates with a channel 304, which further communicates with a drip tray outlet (not shown). During use, condensate formed on the evaporator 21 is collected in the channel 304 before exiting the drip tray 300 via the drip tray outlet. The recess 301 is formed such that the walls of the recess (which may be defined by a pair of flanges) shield the tubes / conduits of the supercooler 23 from the airflow passing through the heat exchanger, while the tubes / conduits of the evaporator 21 are not shielded in the same way. The figure shows that the supercooler circuit 23 at the base of the evaporator 21 is largely enclosed by the surrounding structure of the drip tray, restricting the airflow over the supercooler to reduce the amount of supercooling that would otherwise occur if the supercooler were fully exposed. The supercooler is shown here as having three rows of conduits, with the bottom two rows set at a level below the upper level of the recess. By shielding the supercooler 23 from large airflows, the temperature at the bottom of the outdoor heat exchanger remains warmer than if the supercooler were exposed to full airflow, thereby reducing the risk of the water in the drip tray freezing.

[0042] By shielding the subcooler within the drip tray, some of the heat from the subcooler is retained within the drip tray (rather than being blown away under the action of the fan), reducing the risk of the contents of the drip tray freezing. The heat from the subcooler is also transferred by conduction (through the fins) and / or convection to the lower part of the evaporator above the subcooler, which may help thaw (if applicable) or provide heat to that colder part of the evaporator with the refrigerant (increasing the temperature difference and thereby improving the efficiency of heat transfer to the refrigerant).

[0043] The drip tray structure 300 may be formed directly within the heat pump casing. Optionally, the heat pump casing may be formed of a plastic material, for example by molding (e.g., rotational molding, blow molding, or injection molding) or by 3D printing, and the drip tray structure 300 is provided by the integral features of the casing. The plastic molded product may be made of, for example, MDPE, HDPE, or polypropylene. The plastic molded product may be formed as a hollow body. Filling the hollow molded product entirely or partially may increase its structural stability, improve the thermal insulation properties of the housing—possibly improving the energy efficiency of the heat pump, and / or improving the sound insulation performance of the housing (potentially reducing noise pollution caused by the heat pump compressor). Therefore, the hollow body may then be filled entirely or partially with a thermally insulating material (e.g., polyurethane foam, foamed plastic beads) and / or a sound-insulating material (as described, but optionally a liquid or sand material).

[0044] Figure 3b corresponds to Figure 3a, but shows a possible configuration in which the fan 350 is positioned diagonally to the upper right of the heat exchanger 20, drawing air through the heat exchanger 20 from left to right (the air is drawn in through the air inlet, indicated as 360, and discharged through the outlet 352). The approximate direction of the airflow through the heat exchanger is indicated by a thick arrow, which is approximately parallel to the axis defined by the rows of tubes within the heat exchanger (indicated by the thin line 355).

[0045] While a pair of flanges is generally effective in trapping heat in the space between them, air shielding (i.e., shielding the subcooler from the airflow caused by the fan) can be easily achieved without relying on the use of a pair of flanges.

[0046] Figures 3c and 3d generally correspond to Figures 3a and 3b, but show an alternative configuration in which the supercooler is shielded from the airflow caused by the fan from only one side, rather than both sides. Here again, only the lower part of the heat exchanger 20 is shown so that the details of the configuration around the supercooler can be represented at a larger scale. In Figure 3c, the supercooler is shielded by the flange 302 only on the upstream side of the heat exchanger 20. On the downstream side, where the air exits the heat exchanger 20, the supercooler is not shielded. In the configuration shown, instead, the floor 360 of the compartment housing the heat exchanger 20 is generally sloped upward to guide the air that has passed through the heat exchanger 20 toward the outlet 352. The flange 302 and the floor 360 together can still define the cavity in which the supercooler is housed.

[0047] Conversely, Figure 3d shows an arrangement in which the subcooler is shielded by the flange 302' only on the downstream side. Instead of the upright upstream flange 302, a lip or other shallow feature (or a series of features, there would be no need for a continuous single feature) 362 may be provided to prevent the lower end of the heat exchanger 20 from sliding forward or otherwise coming off. However, it will be understood that the same effect can be achieved equally well by providing a restraining feature on the heat pump case (perhaps as part of the case or as part of the internal chassis) at the end of the heat exchanger 20. In that case, the lip 362 or alternative feature on the lower edge of the heat exchanger 20 can be omitted. Depending on whether the lip 362 or equivalent feature is provided, the subcooler may or may not be housed in a cavity. The inclined floor feature 360 ​​of the modification in Figure 3c can also be optionally used with the downstream flange arrangement in Figure 3d, as indicated by the dashed line 360.

[0048] The configurations shown in Figures 3c and 3d may be slightly less effective in shielding the subcooler than those shown in Figures 3a and 3b, but still provide satisfactory performance.

[0049] Figure 4 schematically illustrates a heat pump 410 according to one aspect of the present invention, particularly illustrating the arrangement of elements for supporting the heat pump processor 400 when determining whether a defrost cycle is necessary and when determining the time for performing the defrost cycle. The heat pump has a housing 411, inside which are arranged an air heat exchanger matrix 20, one or more fans 424 having a coordinated drive motor 404, a processor 400, and (optionally) a heating system heat exchanger 434. However, this may be mounted separately, for example, in place of a gas boiler replaced by the heat pump. The processor 400, having a coordinated memory 402 (which stores software instructions for controlling the operation of the processor, etc.), is operably connected to a valve device 430 for use in controlling the direction of refrigerant flow within the heat pump, particularly to allow reversing the direction of flow through the air heat exchanger matrix between heating and defrosting operation modes. As described above, the valve arrangement 430 may comprise four-way valves or any suitable combination of simpler valves 430A, 430B, and 430C. The processor 400 may also be operably connected to a motor 404 that drives a fan 424 that rotates to drive (pull or push) ambient air over the air heat exchanger matrix 20, and may be configured to both control the fan motor and receive information from a suitable circuit regarding the electrical characteristics or behavior of the fan motor, such as the power consumption of the motor based on the current drawn by the motor 404.

[0050] Figure 4 shows the evaporator section 21 of the air heat exchanger 20, and the lower part of the air heat exchanger, which includes the subcooler device 23, is mostly hidden within the drip tray structure 300. The heat exchanger 20 is preferably arranged so that its fins extend generally vertically.

[0051] Figure 4 also shows an air heat exchanger 20 located upstream of the fan 424 and its motor 404, with the fan positioned to draw air through the air heat exchanger 20. While this is a preferred configuration, alternatively, the fan may be positioned to push air through the air heat exchanger 20 (the air heat exchanger located downstream of the fan).

[0052] The processor 400 may also be operably connected to a temperature and humidity sensing device 406 configured to sense ambient temperature and humidity at the location of the air heat exchanger 420, and may also be connected to the sensor 31 on the input side of the compressor (as described above). The processor 400 and the air heat exchanger 20 may be contained within a single structure, or they may be housed in separate structures / housings, for example, the processor may be located in a housing within a building heated by a heat pump, and the air heat exchanger 20 may be located in a separate housing outside the building. In the latter case, the housing of the air heat exchanger 20 may be controlled by the processor in the building, or may include a processor or controller (e.g., a microcontroller) that operates in conjunction with the processor. Also in the latter case, the processor in the building may communicate with components and systems of the external housing or linked to it by wired or wireless means (e.g., using Matter, Bluetooth, Zigbee, Wi-Fi, 5G, etc.). The processor 400 may be operably connected to a camera (e.g., a video camera) and / or another optical sensor 408 to detect ice accumulation on the air heat exchanger 20, optionally using image processing if a camera is used, and optionally using machine learning, based on signal / image analysis, to detect ice accumulation and the need for thawing. The processor 400 may be operably connected to the internet 450, and therefore to a (local or hyperlocal) weather forecast source 460, and to a system backend 412 managed by the heat pump manufacturer / supplier or installer.Using data from weather forecast source 460, processor 400 may be configured to prepare for adverse weather conditions, such as situations where frost or ice accumulation on the air heat exchanger is likely to be more rapid and / or severe than normal, for example, by limiting (reducing) the maximum output of the heat pump (i.e., reducing the amount of heat extracted from the air, thereby reducing ice accumulation—for example, instead of extracting 16 kW, the heat pump controller reduces the amount of energy extracted to 10-12 kW—for example, a 25-50% reduction in energy extraction), or by reducing the overheat setting so that the refrigerant is supplied to the air heat exchanger at a higher temperature to reduce ice accumulation. In this way, the heat pump can be prepared for the coming adverse weather conditions and, in some cases, enable a reduction in the frequency of thawing events. Alternatively, especially in adverse weather, the heat pump may lead to an increase in the frequency of thawing cycles. The system backend 412 may also be configured to provide advance notice of weather events, for example, based on reports from other heat pumps located in the same neighborhood or in locations experiencing the arrival of a weather front that is en route to the location of the heat pump in question. The system backend 412 can also, of course, provide any necessary firmware upgrades, respond to “incident warnings” by, for example, detecting a failure of a system or component, or respond to reports of failures of a system or component by, for example, arranging the dispatch of an engineer or service agent with any necessary replacement parts or service items.

[0053] The processor 400 may be configured to distinguish between blockages or obstructions caused by frost accumulation on the air heat exchanger and blockages or obstructions caused by other causes (such as leaf accumulation or partial or complete blockage of the air inlet or outlet), based on information from the temperature and humidity sensor 306, or from an external weather information source (such as an online weather resource), and knowledge of the heat pump's recent operating history. These information sources may be supplemented by information from the system camera 408 and from the system backend (optionally following a request for relevant information), such as information on the possibility of frost accumulation, and / or information on the behavior of other air heat pumps in the vicinity of the facility, supported by the system backend 412.

[0054] The processor 400 may be programmed or configured to detect blockages, such as frost accumulation on the air heat exchanger, based on changes in the power consumption characteristics of the fan motor. For example, the power consumption characteristics may be the amount of current consumed, the rate of change in current consumption, the applied voltage, the effective duty cycle in the PWM driver, etc. An increase in power consumed by the fan motor may be detected, for example, based on increased current consumption (or an increase in the effective duty cycle in the PWM driver), and may indicate that the fan motor must operate more strongly to drive air through the air heat exchanger, possibly as a result of partial or complete blockage of the air heat exchanger. The detected increase in power consumption may also be correlated with specific environmental factors, typically temperature and humidity (e.g., relative humidity), and the rate of increase may be significant. Therefore, the processor may be usefully configured to apply machine learning based on these factors to determine whether the detected increase in power consumption is likely to be the result of some other cause, such as the accumulation of ice or snow on the air heat exchanger, or possibly the accumulation of leaves or other debris at the air inlet of the housing containing the air heat exchanger. In the latter case, the processor may be configured to generate a warning (which is also sent to the system backend 412) for the building owner / occupant regarding the need to clean the air inlet, and the warning may optionally be sent by the system backend 412, for example, as a push notification to a user device, or even as an automated phone call, email, or letter. The processor 400 may be configured to detect and record the power consumption of the fan motor 404 at the time of initial installation and to use this as data that can be used to compare subsequent power consumption figures, or it may be pre-programmed before installation, for example, based on machine learning or empirical testing performed during the development of the heat pump. Continuous monitoring (continuous or periodic) of fan power consumption characteristics may also reveal the need for maintenance (e.g., cleaning the air inlet, removing the intrusion of pests such as wasps or beehives, or replacing a damaged fan or fan motor).The air inlet and / or outlet of a heat pump may be blocked by external obstructions (such as towels or clothing hung over the inlet, the placement of equipment such as paddleboards or surfboards, or building materials over the inlet or outlet), or internal obstructions (such as insect or rodent nests or other results of insect or rodent activity, or accumulations of leaves or vegetation) may obstruct the normal path of airflow between the air inlet and outlet. Any of these obstructions, if sufficiently important, should be detectable by the heat pump processor according to an embodiment of the present invention.

[0055] Similarly, the processor may be able to detect the normal defrosting of the air heat exchanger based on characteristic changes in the fan motor's power consumption characteristics, such as a reduction in current consumption or a reduction in the effective duty cycle in the PWM driver. However, it should be understood that the effective defrosting of the heat exchanger may actually lead to an increase in current consumption, for example, if there was a substantial lack of air supply to the fan. For this reason, it is important to observe the fan motor's behavior under various test conditions so that the processor can be appropriately programmed to best detect the state of the air heat exchanger based on the motor's driving characteristics and thus optimize control.

[0056] If the fan motor has a fan motor controller with which it interacts, the processor 300 can receive information about the fan motor's behavior from the fan motor controller, rather than directly detecting the fan motor's behavior. The fan motor controller can be configured (e.g., programmed) to periodically or continuously update the processor 300 with information about the fan motor's power consumption and / or other performance characteristics. The fan motor controller can optionally report to the processor 300 based on considerations of the fan motor's operating behavior and all (or a subset) of the motor's drive elements.

[0057] A controller for a fan motor (which may or may not be an electronically rectified motor) may be programmed or configured to control the rotational speed of the fan motor, for example, to maintain a specific speed (X rpm) or to maintain a speed within a specific range (Y~Z rpm). Additionally or alternatively, the controller may be programmed or configured to control the fan motor to achieve a specific rate of increase in fan speed or a specific rate of increase in fan speed within a specific range, for example, to accelerate the fan from stationary or zero rpm (or low rpm) to a desired or target fan speed or range of fan speed. The controller may be programmed or configured to achieve and maintain different specific fan speeds or speed ranges according to different control states of a heat pump, such as those signaled by a heat pump processor, including heat pump power settings and / or heat pump operating modes (e.g., heating, cooling, defrosting). To control the fan speed and / or rate of increase in fan speed, the controller may adjust one or more of several variables, such as pulse width and / or effective duty cycle in a pulse width modulation drive, current and / or voltage supplied to the motor, and amplitude and / or phase of current pulses applied to the motor. The fan motor controller can receive information about the motor's rotational speed from one or more sensors and / or determine the rotational speed, and therefore the rate of change of the rotational speed, based on information derived from the motor's electrical characteristics / demands and / or behavior. If there is no separate fan motor controller, the heat pump's processor may be programmed or configured to operate as described with reference to the fan motor controller. If a dedicated fan motor controller is provided, the fan motor controller may be programmed or configured to provide the heat pump's processor with information about the rotational speed, the rate of increase of the rotational speed, and / or the motor's electrical characteristics / demands and / or behavior. Such information may be provided continuously or periodically, automatically, or in response to a request from the heat pump's processor.

[0058] Additionally or alternatively, the processor 400 may be configured to detect blockages, such as ice buildup, on the air heat exchanger based on the detected pressure difference across the air heat exchanger between, for example, a pressure measured inside the housing of the air heat exchanger (so to speak, on the "upstream" side of the air heat exchanger) by a first pressure sensor 470 and a pressure measured outside the housing by, for example, a second pressure sensor 472. A fan coupled to the air heat exchanger may be positioned to draw air into the housing through one or more air inlets 480 away from the air heat exchanger, and the air is discharged from the housing through the air heat exchanger and exits through an outlet 482 of the housing. That is, the fan is positioned upstream of the air heat exchanger and pushes air onto the air heat exchanger substantially downstream. Alternatively, the air heat exchanger may be positioned on the inlet side of the fan and the fan is downstream of the air heat exchanger, so that the fan draws air into the housing through the air heat exchanger. The accuracy of pressure difference technology can be affected by whether the fan is upstream or downstream of the air heat exchanger, and as a result, under some circumstances, it may not prove to be a reliable means of detecting blockages such as ice buildup, and accuracy can depend heavily on the precise configuration chosen.

[0059] While pressure difference methods can be used to detect blockages in air heat exchangers, detecting blockages based on changes in the electrical behavior or characteristics of the fan motor is generally more reliable and avoids the need for highly sensitive pneumatic sensors (whose reliability is not always good).

Claims

1. An air-source heat pump comprising a compressor (332) for compressing a refrigerant, an air heat exchanger (320) for extracting energy from ambient air during a heating operation mode, a drip tray for collecting condensates dripping from the air heat exchanger, and a fan (324) for generating airflow through the air heat exchanger, wherein the air heat exchanger (320) includes a liquid subcooler (23) at the bottom configured to receive a liquid refrigerant and supply the refrigerant to an expansion valve (316) positioned so that the refrigerant passes through before passing through an evaporator at the top of the air heat exchanger (320), the liquid subcooler (23) being at least partially housed in the drip tray and at least partially shielded from the airflow.

2. The air source heat pump according to claim 1, wherein one or more structures or formations are provided to shield the supercooler from the airflow.

3. The air source heat pump according to claim 2, wherein the one or more structures or formations together define a cavity in which the subcooler is housed, and the cavity is in communication with the drip tray.

4. The air source heat pump according to claim 2 or 3, wherein the one or more structures comprises at least one flange.

5. The air source heat pump according to claim 4, wherein one or more of the structures comprises at least one pair of opposing flanges.

6. The air-source heat pump according to any one of claims 2 to 5, wherein the one or more structures comprises a groove or recess formed in the floor of the housing of the heat exchanger.

7. The air source heat pump according to any one of claims 2 to 6, wherein the one or more structures or formations form part of the drip tray structure for collecting / managing the outflow of condensate.

8. An air source heat pump according to any one of the preceding claims, wherein the heat pump is housed in a housing made of plastic material, the drip tray is formed integrally with the housing, and optionally one or more of the structures are formed integrally with the housing.

9. The air source heat pump according to claim 8, wherein the housing made of plastic material comprises a plastic molded product, the drip tray is formed as part of the molded product, and optionally one or more of the structures are formed as part of the molded product.

10. The air source heat pump according to claim 9, wherein the plastic molded product accommodates the air heat exchanger and optionally the compressor.

11. The air-source heat pump according to any one of claims 2 to 10, wherein the subcooler comprises a plurality of tubes of various lengths that together form one or more circuits for refrigerant flow.

12. The air source heat pump according to claim 11, wherein the one or more structures or formations provide at least partial shielding from the airflow to all of the tubes of the plurality of lengths.

13. The air source heat pump according to claim 11, wherein the one or more structures or formations shield only a subset of the tubes of the plurality of lengths from the airflow.

14. The air source heat pump according to claim 13, wherein the subset comprises at least half of the plurality, or optionally a majority of the plurality.

15. The air source heat pump according to any one of the preceding claims, wherein the air heat exchanger is a finned structure in which individual fins function on both the liquid subcooler and the upper part.

16. The air source heat pump according to claim 15, wherein the individual fins are arranged such that when condensate is formed from water vapor in the atmosphere, the condensate flows down the fins from the top toward the liquid supercooler.

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