Air-source heat pump

Abstract

To provide an air-source heat pump that mitigates the shortcomings of existing air-source heat pumps. [Solution] A method is provided which is carried out by a controller of an air source heat pump, wherein the heat pump comprises an air heat exchanger having a plurality of independently controllable channels for transporting a refrigerant, and the method is provided which includes operating the heat pump in heating mode, and in heating mode using the air heat exchanger to extract energy from ambient air using the distribution of refrigerant flow through the plurality of independently controllable channels, and performing a stepwise defrosting process by adjusting the distribution of refrigerant flow in the plurality of independently controllable channels so as to selectively defrost a portion of the air heat exchanger while continuing to extract energy from ambient air by the operation of the heat pump in heating mode by continuing to flow refrigerant through at least a portion of the independently controllable channels. A corresponding apparatus is also provided.

Description

Technical Field

[0001] The present invention relates to an air source heat pump and an air heat exchanger matrix for 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) deployment of fuels for heating / cooling (fossil / renewable)" concludes that heating and hot water alone account for 79% of total final energy use (192.5 Mtoe) in European households. The European Commission also reports that "According to Eurostat 2019 figures, around 75% of heating and cooling is still covered by fossil fuels, with only 22% covered by renewable energy". To achieve the EU's climate and energy targets, energy consumption in the heating and cooling sector must be significantly reduced and the use of fossil fuels must be curbed. Heat pumps that extract energy from air, ground or water are considered to make a potentially important contribution to addressing this issue. Very few households have access to water bodies that allow the use of heat pumps that extract energy from water, and the costs and spatial requirements for installing ground heat exchangers are very high, so it is generally cheaper and simpler to install air source heat pumps. It is also widely recognized that air source heat pumps are superior as a replacement for existing gas central heating boilers.

[0003] However, air-source heat pumps have one drawback that heat pumps that extract energy from water or the ground do not. That is, when the heat pump is operated to extract energy from the ambient air in warm or cool climates ("heating mode"), the air heat exchanger of the heat pump needs to be defrosted periodically. An air heat exchanger is a heat exchanger in which heat from the 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 along the tubes by the action of a fan or impeller. In heating mode, because the liquid refrigerant is colder than the ambient air, energy is extracted from the ambient air, the liquid refrigerant vaporizes as a result of the temperature rise of the liquid refrigerant, and the temperature of the ambient air decreases. As a result, water vapor in the ambient air tends to condense on the surface of the air heat exchanger. If the ambient air temperature is sufficiently low, the water condensed on the surface of the air heat exchanger freezes and forms ice. When ice accumulates, the heat transfer efficiency of the air heat exchanger decreases, and if the ice accumulates significantly, the gaps between adjacent conduits in the air heat exchanger become blocked, reducing airflow and further decreasing efficiency. Therefore, air-source heat pumps are configured to perform a so-called defrost cycle from time to time, during which warm refrigerant is supplied to the air heat exchanger to melt the ice and restore the efficiency of the air heat exchanger. Generally, a defrost cycle involves either diverting hot gas from the compressor discharge or high-pressure receiver to the air heat exchanger (known as hot gas defrosting), or reversing the normal energy extraction cycle to operate the heat pump in reverse, moving energy from the home to the ambient air (this is essentially running the heat pump in cooling mode for a short period of time). The frequency of defrost cycle operation may be every 35 minutes, and each cycle may last about 10 minutes, but this varies depending on ambient conditions and the amount of heat load the system is trying to supply. Naturally, the overall efficiency of the air-source heat pump decreases because the heat pump needs to be operated in reverse to defrost the air heat exchanger. [Overview of the project] [Problems that the invention aims to solve]

[0004] The present invention aims to provide an air-source heat pump that, in whole or in part, mitigates at least some of the drawbacks of existing air-source heat pumps. [Means for solving the problem]

[0005] In one embodiment, an air source heat pump is provided, comprising a controller and an air heat exchanger, wherein the air heat exchanger receives a liquid refrigerant to extract energy from ambient air flowing over the air heat exchanger during use, the air heat exchanger comprises a plurality of independently controllable channels for transporting the refrigerant through the air heat exchanger, the air heat exchanger is part of an assembly comprising a flow control device, the flow control device being connected to and operable under the control of the controller, thereby selectively adjusting the flow of the refrigerant through one or more of the plurality of independently controllable channels, the controller being programmed to perform a stepwise defrosting process, the stepwise defrosting process comprising controlling the flow control device to make a first change to the flow rate of the refrigerant flowing through one or more of the plurality of independently controllable channels in order to selectively defrost a portion of the heat exchanger corresponding to only a portion of the independently controllable channels, and a second change to the flow rate of the refrigerant flowing through one or more of the plurality of independently controllable channels in order to selectively defrost the other portion of the heat exchanger corresponding to the other of the independently controllable channels.

[0006] According to the first embodiment, an air source heat pump comprising a controller and an air heat exchanger, wherein the air heat exchanger receives a liquid refrigerant to extract energy from ambient air flowing over the air heat exchanger during use, the air heat exchanger comprises a plurality of independently controllable flow paths for transporting the refrigerant through the air heat exchanger, the air heat exchanger is part of an assembly comprising a flow control device, the flow control device being connected to and operable under the control of the controller, thereby allowing the flow of the refrigerant to pass through one or more subsets of the plurality of independently controllable flow paths while passing through the others of the plurality of independently controllable flow paths. An air-source heat pump is provided, wherein the controller is programmed to perform a defrosting process, the defrosting process comprising: a first step of controlling the flow control device to maintain the flow through one or more independently controllable channels while selectively blocking the flow of refrigerant through only a portion of the independently controllable channels; and then controlling the flow control device to restart the flow of refrigerant through the independently controllable channels whose flow was selectively blocked in the first step, and selectively blocking the flow through at least a portion of the one or more independently controllable channels whose flow was maintained in the first step.

[0007] According to a second embodiment, an air source heat pump is provided, comprising a controller and an air heat exchanger, wherein the air heat exchanger receives a liquid refrigerant to extract energy from ambient air flowing over the air heat exchanger during use, the air heat exchanger comprises a plurality of independently controllable channels for transporting the refrigerant through the air heat exchanger, the air heat exchanger is part of an assembly comprising a flow control device, the flow control device being connected to and operable under the control of the controller, thereby selectively adjusting the flow of the refrigerant through the plurality of independently controllable channels, the heat pump having a first distribution of refrigerant flow across the plurality of independently controllable channels to extract energy from ambient air in heating mode, the controller being programmed to control the flow control device to perform a stepwise defrosting process, in which the distribution of refrigerant flow through a subset of the plurality of independently controllable channels is adjusted to selectively defrost the first portion of the air heat exchanger while continuing to flow the refrigerant through at least a portion of the independently controllable channels, thereby enabling the heat pump to continue extracting energy from ambient air during the defrosting process.

[0008] In a heat pump configuration according to any aspect of the present invention, the heat required to melt the ice accumulated on the air heat exchanger (which is a result of the heat pump extracting energy from the ambient air and occurs when the heat pump is operating in heating mode) is advantageously obtained from the ambient air flowing over the heat exchanger, rather than from the refrigerant circuit, as in cases where defrosting is performed by reversing the flow of the liquid refrigerant or by using a high-temperature gas defrosting method (which also usually involves reversing the flow). It can be seen that defrosting can be achieved without using energy derived from the (warm) refrigerant. Furthermore, the heat pump of the first aspect can continue to extract ambient heat in a continuous heating phase even while the heat exchanger is being defrosted.

[0009] In a heat pump according to an embodiment of the present invention, the controller may be programmed to switch to a first defrost mode in which the distribution of refrigerant flow through a portion of a plurality of independently controllable channels is different from the distribution of refrigerant flow through a portion of a plurality of independently controllable channels in the heating mode, thereby selectively defrosting a first portion of the air heat exchanger, after which the distribution of refrigerant flow returns to the first distribution. Optionally, the stepwise defrosting process may include the controller switching from the first distribution of refrigerant flow to a second defrost mode after the distribution of refrigerant flow returns to the first distribution, in which the distribution of refrigerant flow through a portion of a plurality of independently controllable channels is different from the distribution of refrigerant flow through a portion of a plurality of independently controllable channels in the heating mode and the first defrost mode.

[0010] Optionally, the first defrost mode may include selectively blocking the flow of refrigerant through only a portion of the independently controllable channels while maintaining flow through one or more other independently controllable channels. Optionally, the second defrost mode may include restarting the flow of refrigerant through the independently controllable channels whose flow was selectively blocked in the first defrost mode, and selectively blocking the flow through at least a portion of the one or more independently controllable channels whose flow was maintained in the first defrost mode.

[0011] In an air-source heat pump according to any aspect of the present invention, the defrosting process may include a first step of controlling a flow control device to selectively block the flow of refrigerant through only a portion of the independently controllable flow paths while maintaining the flow through one or more other independently controllable flow paths; and then controlling the flow control device to restart the flow of refrigerant through the independently controllable flow paths whose flow was selectively blocked in the first step, and selectively block the flow through at least a portion of the one or more independently controllable flow paths whose flow was maintained in the first step.

[0012] The processor may be configured / programmed to control the flow control device to maintain a substantially constant overall flow rate while changing the flow rate of refrigerant through different channels. For example, if the flow rate of refrigerant through one or more channels is selectively reduced, the flow rate through one or more other channels can be increased to compensate so that the overall flow rate remains substantially unchanged. Similarly, if the flow rate of refrigerant through one or more channels is selectively increased, the flow rate through one or more other channels can be decreased to compensate so that the overall flow rate remains substantially unchanged. Maintaining the overall flow rate in this way makes it easier to maintain stable operation of the heat pump.

[0013] There may be two, three, or more independently controllable flow paths. Each of these independently controllable flow paths may have its own dedicated expansion valve, or two or more of the independently controllable flow paths may share an expansion valve.

[0014] In an air-source heat pump according to any aspect of the present invention, the controller may be configured to restart the flow of refrigerant through an independently controllable channel whose flow was selectively blocked in the first step, before selectively blocking the flow through at least one of the independently controllable channels whose flow was maintained in the first step.

[0015] In an air-source heat pump according to any aspect of the present invention, the controller may be configured to selectively block the flow through at least one of the independently controllable channels whose flow was maintained in the first step, while simultaneously restarting the flow of refrigerant through the independently controllable channels whose flow was selectively blocked in the first step.

[0016] In an air-source heat pump according to any aspect of the present invention, the controller may be configured to initiate selective blocking of the flow through at least one of the independently controllable channels whose flow was maintained in the first step, and at the same time initiate restarting the flow of the refrigerant through the independently controllable channels whose flow was selectively blocked in the first step.

[0017] In an air-source heat pump according to any aspect of the present invention, the air heat exchanger may have at least three independently controllable flow paths for transporting a refrigerant through the air heat exchanger, and the controller may be configured in a first step to control a flow control device to selectively block the flow of refrigerant through only one of the independently controllable flow paths while maintaining the flow through the other independently controllable flow paths.

[0018] In an air-source heat pump according to any aspect of the present invention, the flow control device may be equipped with a dedicated expansion valve for each independently controllable flow path.

[0019] In an air-source heat pump according to any aspect of the present invention, each independently controllable flow path may include a plurality of conduits for passing a refrigerant. Optionally, with respect to each independently controllable flow path, each conduit of the plurality of conduits may be connected in parallel to a refrigerant distribution unit. Optionally, within the air heat exchanger, with respect to each independently controllable flow path, each conduit of the plurality of conduits may be grouped into one or more groups consisting of the plurality of conduits. Optionally, the groups of conduits in different independently controllable flow paths may be arranged alternately with respect to one another.

[0020] In an air-source heat pump according to any aspect of the present invention, independently controllable flow paths are arranged alternately with respect to each other, so that in the air heat exchanger, one or more conduits of the first independently controllable flow path may be sandwiched on both sides by one or more conduits of different independently controllable flow paths.

[0021] In an air-source heat pump according to any aspect of the present invention, the assembly may include a refrigerant subcooler configured to receive little to no airflow, and the refrigerant is configured to flow through the refrigerant subcooler before reaching a flow control device.

[0022] In an air-source heat pump according to any aspect of the present invention, the controller may be configured to determine, at least in part, the necessity of performing a defrost operation of the air heat exchanger based on a change in the power consumption characteristics of the heat pump's fan motor. Optionally, the power consumption characteristics are current consumption or the rate of change in current consumption.

[0023] In an air-source heat pump according to any aspect of the present invention, the controller may be configured to selectively block the flow of refrigerant by controlling the flow control device to stop the flow of refrigerant through a selected independently controllable flow path while maintaining the flow through one or more other independently controllable flow paths. Alternatively, the controller may be configured to selectively block the flow of refrigerant by controlling the flow control device to maintain the reduced flow of refrigerant through a selected independently controllable flow path while maintaining the flow through one or more other independently controllable flow paths.

[0024] An air-source heat pump according to any aspect of the present invention may be configured to perform defrosting in response to a trigger that performs defrosting of an air heat exchanger.

[0025] According to the third aspect, there is provided a method implemented by a controller of an air-source heat pump, wherein the heat pump comprises an air heat exchanger having a plurality of independently controllable flow paths for conveying a refrigerant, the method comprising: operating the heat pump in a heating mode, and in the heating mode, extracting energy from ambient air using the distribution of refrigerant flow through the plurality of independently controllable flow paths by using the air heat exchanger; and performing a stepwise defrosting process by adjusting the distribution of refrigerant flow in the plurality of independently controllable flow paths so as to selectively defrost a part of the air heat exchanger while continuing to extract energy from the ambient air through the operation of the heat pump in the heating mode by continuing to flow the refrigerant through at least a part of the independently controllable flow paths.

[0026] In the method according to the third aspect, adjusting the distribution of the refrigerant flow may include selectively blocking the refrigerant flow through only a part of the refrigerant conveying conduits of the air heat exchanger while maintaining the flow through the other ones of the refrigerant conveying conduits of the air heat exchanger. Optionally, the refrigerant flow through the refrigerant conveying conduits of the air heat exchanger where the flow is selectively blocked can be resumed before selectively blocking the flow through at least a part of the refrigerant conveying conduits of the air heat exchanger where the flow is maintained.

[0027] In the method according to the third aspect, the resumption of the refrigerant flow through the refrigerant conveying conduits of the air heat exchanger where the flow is selectively blocked can be started at the same time as selectively blocking the flow through at least a part of the refrigerant conveying conduits of the air heat exchanger where the flow is maintained.

[0028] In the method according to the third aspect, the heat pump may be connected so as to supply heat to a heating system, and the method may further include performing the defrosting operation without interrupting the supply of heat to the heating system.

[0029] According to a fourth aspect, there is provided a method implemented by a controller of an air-source heat pump, wherein the heat pump comprises an air heat exchanger provided with a plurality of refrigerant conveying conduits, the method comprising, in response to a trigger for performing a defrosting operation of the air heat exchanger, the following: in a first step, selectively blocking the flow of refrigerant through only a part of the refrigerant conveying conduits of the air heat exchanger while maintaining the flow through the others of the refrigerant conveying conduits of the air heat exchanger, and thereafter, resuming the flow of refrigerant through the refrigerant conveying conduits of the air heat exchanger where the flow has been selectively blocked, selectively blocking the flow through at least a part of the refrigerant conveying conduits of the air heat exchanger whose flow was maintained in the first step, and defrosting the air heat exchanger by the above steps.

[0030] In the heat pump of any aspect of the present invention, the heat pump may be provided with a mechanism for detecting ice accumulation, or a mechanism for detecting climatic conditions under which ice accumulation is expected, and may also be provided with any other mechanism for ensuring timely defrosting based on one or more of these triggers. Further, the heat pump may be provided with a processor configured to put the heat pump into a defrost mode as needed. One possible trigger includes detection of a change in one or more power characteristics required by the motor of the heat pump fan. For example, the processor may be responsive to detection of a change in current consumption (e.g., an increase in current), or a change in the rate of change of current consumption (e.g., an increase or decrease in the rate of change of current consumption). The processor may be configured to respond to detection of a change in a vector characteristic rather than simply responding to an increase in the overall level, and may be configured to respond to a change in the overall level, or the rate of change of a characteristic such as motor current. For example, the processor may be configured to respond to an evaluation of an increase relative to a known (stored) current consumption value when no ice is accumulated on the evaporator, which is determined, for example, during commissioning of the heat pump. Additionally or alternatively, the heat pump may receive an externally generated trigger. [Brief explanation of the drawing]

[0031] Embodiments of the present invention will be described below with reference to the accompanying drawings, merely as examples. [Figure 1] This diagram schematically shows an air-source heat pump operating in heating mode. [Figure 2] This diagram schematically shows the air-source heat pump shown in Figure 1 operating in defrost mode. [Figure 3A] This figure schematically shows an air heat exchanger assembly according to one aspect of the present invention. [Figure 3B] This figure schematically shows the details of an air heat exchanger matrix according to one aspect of the present invention. [Figure 4] This figure schematically shows an air-source heat pump according to one aspect of the present invention. [Modes for carrying out the invention]

[0032] 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 simplicity, electrical elements, sensing elements, and control elements, as well as connections, including the heat pump controller or processor, are omitted. Starting from the lower right corner of the figure, a low-temperature liquid refrigerant is delivered from a liquid receiver 12 to a heating expansion valve 16 along a conduit 14 that penetrates the air heat exchanger 20. The conduit 14 has an open end 15. The open end 15 is immersed in the liquid refrigerant when in use, so that liquid refrigerant, rather than refrigerant vapor, is supplied from the receiver 12 to the conduit 14.

[0033] In the heating expansion valve 16, the refrigerant passes through a small opening, causing a pressure drop and thereby 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 vaporize, resulting in a decrease in the temperature of the refrigerant, and the refrigerant exits the expansion valve as a mixture of liquid and vapor. The refrigerant enters the distribution unit 18 from the expansion valve 16. In the distribution unit 18, a single input conduit is connected to multiple output conduits, each output conduit leading to a conduit in the air heat exchanger 20.

[0034] A one-way valve 50 is provided in parallel with the heating expansion valve 16, and is directed to allow flow from the distribution section 18 to the conduit 14 (the direction in which the refrigerant flows during the cooling operation mode) and to prevent the flow of refrigerant from the conduit 14 to the distribution section. Therefore, in the heating mode, the refrigerant must pass through the heating expansion valve 16 in order to reach the distribution section 18. As those skilled in the art will understand, the heating expansion valve 16 (like other expansion valves in a heat pump) is controlled by the heat pump's processor to achieve a target value of refrigerant overheating appropriate for the current operating conditions.

[0035] A filter dryer 51 may be provided in the flow path leading to the heating expansion valve 16. If a filter dryer 51 is present, during cooling and defrosting, the flow to the filter dryer 51 is also bypassed by the flow passing through the one-way valve 50.

[0036] In one modification, the distribution unit 18 may have three flow paths: a single input conduit 17 with a small internal fixed orifice, multiple output conduits (indicated by reference numeral 19), and an internal bypass conduit (not shown). In heating mode, the refrigerant flows through the heating expansion valve 16 to the single input conduit 17 of the distribution unit 18, through the small internal fixed orifice, and out of the multiple output conduits 19. In heating mode, there is no flow through the internal bypass conduit. Expansion of the refrigerant is achieved by the heating expansion valve and the fixed orifice. In cooling mode, the refrigerant flows from the multiple output conduits 19, out of the internal bypass conduit, through the one-way valve 50, and bypasses the internal fixed orifice and the heating expansion valve 16; therefore, in cooling mode, the heating expansion valve 16 and the internal fixed orifice of the distribution unit 18 have a negligible effect. In another modification, the distribution unit may be formed without the small internal fixed orifice and the bypass conduit.

[0037] Although the air heat exchanger 20 is schematically shown to include only four conduits traversing the air heat exchanger, in practice there are more such conduits, each conduit typically having heat-conducting fins to improve heat transfer from the air to the refrigerant inside the conduit. The air heat exchanger 20 is equipped with (or connected to) a fan 24 that moves (suctions or blows) ambient air over the matrix 22 of the air heat exchanger 20.

[0038] In heating mode, the refrigerant in the air heat exchanger 20 is heated by energy absorbed from the surrounding air, causing the refrigerant to change state into vapor. The vapor itself absorbs energy from the air, further heating it and potentially becoming superheated vapor. The vaporized refrigerant exits the air heat exchanger 20 via a recovery unit or manifold 26. The recovery unit or manifold 26 is led to a return conduit 28, which is led to port 1, the first port of the four-way valve 30. The vaporized refrigerant exits the four-way valve 30 via port 2 and flows from there to the compressor 32. In the compressor, the heated vaporized refrigerant received at low pressure is compressed into high-pressure vapor, and the refrigerant's temperature rises further during the compression process. The refrigerant returns from the compressor 32 through the four-way valve 30, entering the valve via port 3 and exiting via port 4. Port 4 is led to the heat exchanger matrix (not shown) in the heating system heat exchanger 34. The heating system heat exchanger 34 may be a water heat exchanger as shown herein, in which energy from a high-temperature refrigerant is transferred to water (or, in the case of space heating, some other suitable working fluid) for, for example, space heating by a central heating system, or to supply hot water for residential or industrial use. The high-temperature refrigerant enters the heat exchanger 34 at port 36, condenses, and then exits as cooled refrigerant at port 38. The water for heating enters the heat exchanger 34 at port 40, which is the low-temperature side of the heat exchanger 34, and exits at port 42, which is the high-temperature side of the heat exchanger 34.

[0039] Within the heating system heat exchanger 34, the refrigerant condenses from vapor to liquid, releasing heat into the water in the water circuit of the heat exchanger 34. The cooled liquid refrigerant flows from port 38 to a one-way valve 54. The one-way valve 54 is directed to allow flow from the water heat exchanger 34 to the liquid receiver 12. Thus, this one-way valve 54 functions as a bypass for another expansion valve 44. The other expansion valve 44 is provided to expand the refrigerant as it flows from the liquid receiver 12 towards the water heat exchanger 34 in cooling operation mode (and therefore also during defrosting of the air heat exchanger). In heating mode, the refrigerant can flow through the one-way valve 54 and bypass the cooling expansion valve 44 with minimal restriction, so the cooling expansion valve 44 has a negligible effect in heating mode. The cooled liquid refrigerant then returns to the liquid receiver 12, which is the starting point of this process. The heating system heat exchanger 34 can also use a refrigerant to heat air, for example, for the purpose of heating a space with hot air, instead of using a refrigerant to heat water, but it will be understood that the principle is the same.

[0040] Figure 1 also includes a further heat exchanger 46, which is led from the refrigerant conduit 14 via a further expansion valve 48. This further heat exchanger 46 is optional, but is preferably provided as a means of cooling (and controlling the temperature of) the compressor and the electric inverter (not shown) that supplies power to various other electrical components and systems of the heat pump. The further heat exchanger 46 may include a heat sink, which is thermally connected to the inverter and optionally connected to other electronic and power components of the heat pump. The cooling provided by the further heat exchanger 46 contributes to ensuring the correct operation of the inverter and other electronic components and extending their lifespan. In addition, this cooling captures heat that would normally be waste heat, which is supplied to the refrigerant, which is then supplied to the compressor 32, and thus further contributes 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 the operating mode (i.e., heating, cooling, defrosting). The inverter cooling expansion valve is controlled by the heat pump processor to adjust the refrigerant conditions passing through the inverter cooling heat exchanger, thereby achieving a desired cooling effect, such as a target value for the inverter drive temperature.

[0041] When the heat pump shown in Figure 1 is operated on a cool day in a warm climate, water vapor in the ambient air may condense on the air heat exchanger 20 and turn into ice. The accumulation of ice on the air heat exchanger 20 restricts the airflow through the air heat exchanger and also reduces the energy transfer efficiency from the ambient air to the refrigerant. The heat pump typically includes a mechanism for detecting ice accumulation, or a mechanism for detecting climatic conditions under which ice accumulation is expected, or any other mechanism for ensuring timely defrosting, and further includes a processor configured (e.g., programmed) to enter defrosting 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. A processor or controller typically includes and / or is connected to a memory configuration that stores relevant code, instructions, programs, algorithms, and data that enable the processor to perform the relevant operations, functions, methods, and processes.

[0042] Although not shown in Figure 1, for the reasons described above, it is preferable to provide a drip tray below the air heat exchanger 20 in order to collect condensed water when the heat pump is operating in defrost mode or heating mode.

[0043] 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 at or just upstream of the compressor inlet, particularly the degree of overheating.

[0044] Figure 2 corresponds to Figure 1, but shows a heat pump operating in cooling mode instead of heating mode, which is also used in defrosting mode. In cooling mode, the refrigerant flow is reversed compared to 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 is sent to the manifold 26 instead of passing adjacent to the heating system heat exchanger 34, and from there to the air heat exchanger 20. By supplying the high-temperature refrigerant to the air heat exchanger, ice deposits can be thawed. The cooled refrigerant exits the air heat exchanger 20 via the distribution unit 18 and then returns to the liquid receiver 12 via the one-way bypass valve 50.

[0045] From the liquid receiver 12, the refrigerant flows along the conduit 52. The conduit 52 has an open end 53. The open end 53 is immersed in the liquid refrigerant when in use, so that liquid refrigerant, rather than refrigerant vapor, is supplied from the receiver 12 to the conduit 52. The refrigerant from the receiver 12 flows along the conduit 52 through the cooling expansion valve 44 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 by the cooling expansion valve 44.

[0046] In the expansion valve, the refrigerant passes through a small opening, causing a pressure drop and thereby 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 vaporize, resulting in a decrease in the temperature of the refrigerant (therefrigerant then exits the expansion valve as a mixture of liquid and vapor). The expansion valve can be controlled by the heat pump processor based on data from pressure and temperature sensors 31 located on the input side of the compressor 32.

[0047] The refrigerant flowing through the heating system heat exchanger 34 absorbs heat from the hot water in the heat exchanger (which may be flowing from port 40 to port 42) and vaporizes. The heated vaporized refrigerant exits the heat exchanger at port 36 and is sent to port 4 of the four-way valve 30, exiting through port 2. From port 2 of the four-way valve 30, the refrigerant vapor is sent 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 supplying it to port 3 of the four-way valve 30. The refrigerant exits the four-way valve through port 1. The input side of the compressor 32 is always at low pressure when the compressor is operating, so under the control of the heat pump processor, the refrigerant continues to flow through the inverter heat exchanger 46 towards the compressor 32.

[0048] Referring next to Figure 3A, the mechanism of a novel air heat exchanger assembly 300 according to one aspect of the present invention can be schematically confirmed. The air heat exchanger assembly 300 comprises an air heat exchanger matrix 322, which is connected between a distributor 302 (from which the refrigerant is received) and a recovery unit or manifold unit 304 (the refrigerant flows from the matrix 322 toward the recovery unit or manifold unit 304). Optionally but preferably, the air heat exchanger assembly 300 also comprises a liquid subcooler 306. The refrigerant flows through the liquid subcooler 306 on its way from the refrigerant conduit 14, which transports the refrigerant from the liquid refrigerant receiver 12, toward the distributor 302. If a liquid subcooler 306 is present, it is preferable that the liquid subcooler 306 receives little to no airflow from the fan 24, thereby maintaining the lower part of the air heat exchanger at a higher temperature than the ambient temperature. This serves to ensure that the liquid refrigerant received by the distributor 302 is cooled to a temperature below the boiling point of the refrigerant, while preventing ice buildup at the bottom of the air heat exchanger.

[0049] In the example shown, the air heat exchanger matrix 322 consists of two independently controllable flow paths / circuits A and B. Each independently controllable flow path / circuit is supplied by a dedicated distribution unit, from which each dedicated distribution unit receives refrigerant from a dedicated expansion valve. Thus, in this example, it can be seen that flow path A is supplied by a dedicated distribution unit 318A that receives refrigerant from a dedicated expansion valve 316A, and flow path B is supplied by a dedicated distribution unit 318B that receives refrigerant from another dedicated expansion valve 316B. Three or more independently controllable flow paths / circuits may be provided (e.g., 3, 4, 5, 6, 7, 8, 9, or 10 or more). The number of independently controllable flow paths / circuits can be changed depending on the application and circumstances. Here, each independently controllable flow path / circuit is shown to have its own dedicated expansion valve 316, but it will be understood that it is also possible to share one expansion valve among multiple independently controllable flow paths / circuits, and control of each independently controllable flow path / circuit is performed by each additional (non-expansion, e.g., solenoid) valve located downstream of the shared expansion valve. Furthermore, using a multi-outlet expansion valve can be advantageous in some cases. A multi-outlet expansion valve, for example, circulates the refrigerant to each of several different outlets, functioning as both an expansion valve and a distributor, thereby reducing the number of individual expansion valves used.

[0050] In the example shown, the conduits of two independently controllable flow paths / circuits A and B are arranged alternately, with pairs of conduits in B separated by conduits in A, and pairs of conduits in A separated by conduits in B. However, it will be understood that each illustrated element A1-A6, B1-B6 can actually represent one conduit or multiple (2, 3, 4, 5, 6, 7, 8, 9, 10, or more) conduits. An example of such an arrangement is schematically shown in Figure 3B. In Figure 3B, the air heat exchanger matrix also consists of two independently controllable flow paths / circuits A and B (although obviously more independently controllable flow paths / circuits are possible), which are provided as banks A1-A8 and B1-B8, with groups of conduits arranged alternately. In this example, each group consists of five individual conduits, but as mentioned above, each group of conduits can contain two to more than 10 individual conduits. Furthermore, for the sake of clarity, the schematic diagram does not show the existence of gaps (air gaps) between adjacent elements of the air heat exchanger matrix. However, since adjacent elements of the matrix are separated from each other, it should be understood that air can flow over and between the conduits (as if the diagram were printed on paper, entering or leaving the paper). Each conduit may be a finned tube, but other forms of structure are also conceived. The air heat exchanger matrix may consist of only a single layer of conduits or multiple layers of conduits (2, 3, 4, 5, 6, 7, 8, 9, or 10 or more), but generally it is preferable to have 1 to 5 layers, for example, 2 or 3 layers.

[0051] In Figures 3A and 3B, the air heat exchanger matrix is ​​depicted as having a rectangular contour, but it will be understood that this is simply for the sake of clarity. In practice, an air heat exchanger can have an outer circumference of any suitable shape to fit the housing it is mounted in. For example, it may be advantageous to have an air heat exchanger with a generally circular outer circumference for mounting in a suitable housing, because this facilitates the provision of more uniform air movement through the air heat exchanger, which is based, for example, on using a fan with blades that form a circle whose outer circumference roughly corresponds to the diameter of the air heat exchanger matrix.

[0052] Typically, household-sized heat pumps can use tubing with an outer diameter of 5mm to 7mm. Good thermal performance can be achieved by using copper tubing with aluminum fins, such as fins with through holes for receiving the tubing. For tubing with an outer diameter of 5mm to 7mm, a convenient center spacing may be in the range of 15mm to 25mm, for example, 18mm to 22mm, or about 20mm. Conveniently, tubing in adjacent layers may be offset, such as the gap between adjacent tubing in the first row being located in front of the tubing in the second layer.

[0053] Instead of interlacing independently controllable flow paths / circuits, it is also possible to arrange the flow paths in a block. For example, the upper and lower halves of a heat exchanger can each be provided as a single block of multiple flow paths, provided that the resulting asymmetry of airflow is acceptable. Also, when defrosting the upper half, water from the melted ice may flow down to the lower half, but since frost still adheres to the lower half and cooling continues, refreezing is possible. Such refreezing tends to be less of a problem in interlaced arrangements, which is one reason why interlaced arrangements are preferred.

[0054] The reasons for forming an air heat exchanger with multiple independently controllable flow paths / circuits (thus effectively forming a section-type air heat exchanger) are explained below. As discussed in Figure 2, in heating mode, ice accumulates in the air heat exchanger of an air-source heat pump, reducing efficiency and necessitating periodic defrosting cycles, which in turn reduce the overall efficiency of the heat pump. To achieve defrosting, the direction of the refrigerant flow must be reversed (from the direction used in heating mode), which is particularly detrimental to overall efficiency. The inventors have found that by providing an air heat exchanger with multiple independently controllable flow paths / circuits, it is possible to defrost a portion of the independently controllable flow paths / circuits by changing the refrigerant flow rate (i.e., the amount of refrigerant passing through a subset of selected flow paths) rather than reversing the refrigerant flow. Typically, the change in flow rate is a reduction in flow rate, but it is also possible to perform selective defrosting by increasing the refrigerant flow rate. However, this carries the risk that the refrigerant may not completely vaporize as it passes through the heat exchanger, and therefore, further control measures may be required to prevent the compressor from receiving liquid refrigerant.

[0055] The change in flow rate may include selective blocking (reduction) of the refrigerant flow to selected channels / circuits, for example, when the ambient temperature is above freezing point (frost accumulation on the air heat exchanger is primarily caused by the presence of refrigerant at temperatures below 0°C, rather than sub-zero ambient temperatures), while continuing to operate the heat pump in heating mode (as shown in Figure 1) using the remaining independently controllable channels / circuits, or at least significantly limiting the refrigerant flow through them. By changing the refrigerant flow to a selected subset of the controllable channels (e.g., under the control of the heat pump controller), the conduits in question are no longer cooled to the same extent and therefore tend toward the ambient temperature, resulting in the thawing of ice accumulated in the areas of the air heat exchanger associated with these conduits. Once the conduits in question are defrosted, the heat pump controller can be used to control another subset of the controllable channels, which can then be defrosted. This process can be repeated until all conduits in the air heat exchanger matrix are defrosted, and the cycle is then repeated as needed or as determined according to a predetermined schedule. As mentioned above, the processor may be configured / programmed to control the flow control device to maintain the overall refrigerant flow rate (the actual refrigerant flow rate will naturally usually depend on the set operating conditions, e.g., the output being taken out, and therefore is not always a single constant value when the heat pump is in heating mode).

[0056] Figure 4 schematically shows the arrangement of elements to assist a heat pump 410, in particular the heat pump processor 400, according to one aspect of the present invention in determining whether a defrosting cycle is necessary, and further determining what approach to the defrosting cycle is appropriate, for example, whether to selectively shut down a portion of the air heat exchanger to melt ice with ambient temperature, or whether to supply heated steam to the air heat exchanger. The heat pump comprises a housing 411, inside which are an air heat exchanger matrix 422, one or more fans 424 with attached drive motors 404, a processor 400, and (optionally) a heating system heat exchanger 434. However, the heating system heat exchanger 434 may be installed remotely, for example, in place of a gas boiler replaced by the heat pump.

[0057] The processor 400 has associated memory 402 (which stores software instructions for controlling the operation of the processor) and is operationally connected to dedicated expansion valves 416A, 416B, and 416C, one for each of the three independently controllable flow paths / circuits A, B, and C. The processor 400 is also operationally connected to a motor 404 that drives a fan 424 that rotates to send ambient air to the air heat exchanger matrix 422, and may be configured to control the fan motor and receive information about the motor's power consumption from appropriate circuits, for example, based on the current consumed by the motor.

[0058] In Figure 4, the air heat exchanger matrix 422 is shown to be located downstream of the fan 424 and its motor 404, but in practice the fan (and preferably its motor as well) may be located downstream of the air heat exchanger matrix 422, in which case the fan is preferably configured to draw air into the air heat exchanger matrix 422 rather than to push air through it.

[0059] The processor 400 may also be operationally connected to a temperature and humidity sensing device 406 configured to sense the ambient temperature and humidity at the location of the air heat exchanger 422. The processor 400 and the air heat exchanger matrix may be housed in a single structure or in separate structures / housings. For example, the processor may be located in a housing within a building heated by a heat pump, while the air heat exchanger 422 may be located in a separate housing outside the building. In the latter case, the housing for the air heat exchanger 422 may also include a processor or controller (e.g., a microcontroller) controlled by or operating in conjunction with the processor within the building. In the latter case, the processor within the building may communicate with components and systems in or associated with the external housing by wired or wireless means (e.g., using Matter, Bluetooth, Zigbee, Wi-Fi, 5G, etc.). The processor 400 may also be operationally connected to a control device 440 that controls the heating system of the building 435. The control device may comprise one or more thermostats 442 and a controller 444 that can operate to control the heating system, the controller 444 which, for example, sets the start and end times of the heating period. The controller 444 may form part of a “smart home” or home automation system that can be used to schedule the operation of heating systems (e.g., both room heating and household hot water), security monitoring systems, lighting, etc. Such a home automation system may be programmed to control the operation of systems and subsystems such as room heating and hot water heating based on occupancy data provided by the occupants of the building, or data derived from diary / schedule information about the occupants’ activities and planned occupancy. The home automation system may also use occupancy information provided by motion sensors or the opening and closing of doors (both internal and external), which tracks actual occupancy using sensors that are also supported by security monitoring systems, or derived from the operation of electrical switches.The heat pump processor 400 can use such actual and predicted occupancy data, along with data regarding the planned heating period, to determine whether or not to perform a defrosting operation. For example, if the heating controller 444 is scheduled to turn off the heating system when it is determined that the air heat exchanger may benefit from defrosting, and therefore will stop requesting energy from the heat pump in the near future (e.g., less than one hour or less than 30 minutes), the processor 400 can decide not to perform a defrosting operation.

[0060] The processor 400 may be operationally connected to a camera (e.g., a video camera) and / or another optical sensor 408 to detect ice accumulation on the air heat exchanger matrix 422, optionally using image processing if a camera is used, and optionally using machine learning to detect ice accumulation and the need for defrosting based on signal / image analysis. The processor 400 may also be operationally connected to the internet 450 and therefore operationally connected to a weather forecast source 460 (local or hyperlocal), and may also be connected to a system backend 412 managed by the heat pump manufacturer / supplier or installer. The processor 400 may use data from the weather forecast source 460 to prepare for adverse weather conditions in which frost or ice buildup on the air heat exchanger may occur faster and / or more severely than usual, for example by limiting (reducing) the maximum output of the heat pump (i.e., reducing ice buildup by reducing the amount of heat extracted from the air; for example, the heat pump controller may be configured to reduce the amount of energy extracted to 10-12 kW instead of 16 kW, which is, for example, a 25-50% reduction in energy extraction), or by reducing the superheat setting so that the refrigerant is supplied to the air heat exchanger at a higher temperature to reduce ice buildup. In this way, the heat pump can prepare for future adverse weather conditions and enable a reduced frequency of defrosting operations. Alternatively, especially in adverse weather conditions, the heat pump can increase the frequency of defrosting cycles or switch to supplying high-temperature refrigerant vapor to the air heat exchanger, rather than relying on simply shutting down a portion of the air heat exchanger first. The system backend may also be configured to provide advance notice of weather events, which may be based, for example, on reports from other heat pumps located in the same neighborhood or from other heat pumps located in areas experiencing the arrival of a weather front heading toward the location of the heat pump in question.The system backend 412 can also, naturally, provide necessary firmware upgrades and respond to “incident alerts,” which can be done, for example, by detecting or responding to reports of system or component failures, and by arranging the dispatch of engineers or service agents along with necessary replacement parts or inspection and maintenance items.

[0061] The processor 400 may be configured to detect frost buildup on the air heat exchanger based on characteristic changes in the electrical behavior or power consumption characteristics of the fan motor. For example, the power consumption characteristics may be current consumption, rate of change of current consumption, or effective duty cycle in a pulse width modulation (PWM) driver. An increase in power consumed by the fan motor, detected based on, for example, an increase in current consumption, an increase in supply voltage, or an increase in the effective duty cycle in a PWM driver, may indicate that the fan motor must operate more vigorously to move air into the air heat exchanger, which is likely a result of partial or complete blockage of the air heat exchanger. The detected increase in power consumption may also correlate with certain environmental factors, usually temperature and humidity (e.g., relative humidity), and the rate of increase may be significant. The processor may therefore be usefully configured to apply machine learning based on these factors, thereby determining whether the detected increase in power consumption is likely a result of ice or snow buildup on the air heat exchanger, or possibly due to another cause, such as the buildup 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 an alert to the building owner / occupant regarding the need to clean the air inlet (and may also be sent to the system backend 412), which may optionally be sent by the system backend 412, for example, as a push notification to the 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 initial installation and use this as a baseline for comparison with later power consumption values, and may also be programmed before installation based on machine learning performed, for example, during the development of the heat pump. Continuous monitoring of fan power consumption (continuous or periodic) may also reveal the need for maintenance (e.g., the need to clean the air inlet, remove pest infestations such as wasps or beehives, or replace a damaged fan or fan motor).

[0062] Motor 404 is preferably an electronically rectified motor (EC motor), also known as a brushless DC motor (BLDC motor) using a direct current (DC) power supply. It can switch the DC current to the motor windings using an electronic controller (usually located within the fan motor housing), thereby generating a substantially rotating magnetic field in space, which the permanent magnet rotor follows. The controller can control the motor speed and torque by adjusting the phase and amplitude of the DC current pulses and / or using either form of pulse width modulation and / or voltage control. This control system is a replacement for the mechanical commutator (brushes) used in many conventional electric motors. The fan motor controller itself is controlled by a heat pump controller that supplies fan speed request signals based on the operating state of the heat pump. Numerous means of communication exist between the fan controller and the heat pump controller (analog, PWM, MODBUS, etc.), but the use of MODBUS is preferred. This is because it enables bidirectional communication, allowing the heat pump controller to obtain information from the fan controller, such as fan motor current, power, voltage, pulse amplitude and / or duration and / or frequency, and use this information.

[0063] The processor may also be able to detect the success of defrosting the air heat exchanger based on characteristic changes in the fan motor's power consumption characteristics, such as a decrease in current consumption. However, it should be recognized that effective defrosting of the heat exchanger may actually lead to an increase in current consumption, for example, if the air supply to the fan was substantially cut off. For this reason, it is important to observe the fan motor's behavior under various test conditions, which will allow the processor to be properly programmed to optimally detect the state of the air heat exchanger based on the motor drive characteristics and thus optimize control.

[0064] Additionally or alternatively, the processor 400 may be configured to detect ice buildup on the air heat exchanger based on a pressure difference detected across the entire air heat exchanger, where this pressure difference is the difference between the pressure measured, for example, by a first pressure sensor 470 inside the housing of the air heat exchanger (so to speak, on the "upstream" side of the air heat exchanger) and the pressure measured, for example, by a second pressure sensor 472 outside the housing. In general, a fan attached to the air heat exchanger draws 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 by passing over or through the air heat exchanger and exiting through an outlet of the housing. Alternatively, it is also possible to draw air into the housing through the air heat exchanger, but this is a less preferred configuration, in which case the pressure difference technique is not always a reliable means of detecting ice buildup, and this depends very much on the specific configuration chosen.

[0065] In any case, the processor 400 can also use information provided by the heating system controller 440 and / or the home automation system 444 to determine whether or not to perform a defrost operation when it is deemed necessary.

[0066] If the fan motor has an attached fan motor controller, the processor 400 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 may be configured (e.g., programmed) to periodically or continuously update the processor 400 with information about the fan motor's power consumption and / or other performance characteristics. The fan motor controller may optionally report to the processor 400 based on the fan motor's operating behavior and consideration of all (or a subset thereof) of the motor drive factors.

[0067] 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 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, such as when accelerating the fan from a stationary state or zero rpm (or low rpm state) to a desired or target fan speed or fan speed range. The controller may be programmed or configured to achieve and maintain different specific fan speeds or speed ranges depending on different control states of the heat pump, such as signals from the heat pump processor, such as heat pump output settings and / or heat pump operating modes (e.g., heating, cooling, defrosting). To control the fan speed and / or the rate of increase of the fan speed, the controller can adjust one or more of several variables, such as the pulse width and / or effective duty cycle in the pulse width modulation drive, the current and / or voltage supplied to the motor, and the amplitude and / or phase of the 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 consequently the rate of change of the rotational speed, based on information derived from the motor's electrical characteristics / requirements and / or behavior. If a separate fan motor controller does not exist, the heat pump processor may be programmed or configured to behave with respect to the fan motor controller as described above. If a dedicated fan motor controller is provided, the fan motor controller may be programmed or configured to provide the heat pump processor with information about the rotational speed, the rate of increase of the rotational speed, and / or the motor's electrical characteristics / requirements and / or behavior. Such information may be provided continuously or periodically, and may be provided automatically or in response to a request from the heat pump processor.

[0068] In some cases, it may be preferable to provide multiple motor-driven fans in an air-source heat pump. While the above description has generally focused on controlling a single-motor-driven fan for clarity and brevity, it will be understood that the principles of the methods and systems described above are equally applicable to multi-motor setups.

[0069] A differential pressure method can be used to detect blockage of an air heat exchanger. However, the applicants have found that detecting blockage of an air heat exchanger based on changes in the power consumption characteristics of the fan motor is generally more reliable, and that this detection eliminates the need for a sensitive pneumatic sensor (the reliability of sensitive pneumatic sensors is not always good).

Claims

1. An air-source heat pump comprising a controller and an air heat exchanger, wherein the air heat exchanger receives a liquid refrigerant to extract energy from ambient air flowing over the air heat exchanger during use, the air heat exchanger comprises a plurality of independently controllable flow paths for transporting the refrigerant through the air heat exchanger, the air heat exchanger is part of an assembly equipped with a flow control device, the flow control device is connected to the controller and is operable under the control of the controller, thereby selectively adjusting the flow of the refrigerant through the plurality of independently controllable flow paths. In the heating mode, the heat pump has a first distribution of refrigerant flow across the plurality of independently controllable channels to extract energy from the ambient air. An air-source heat pump, wherein the controller is programmed to control the flow control device to perform a stepwise defrosting process, and in the stepwise defrosting process, the distribution of the refrigerant flow through a subset of the plurality of independently controllable flow paths is adjusted to selectively defrost a first portion of the air heat exchanger while continuing to flow the refrigerant through at least a portion of the independently controllable flow paths, thereby enabling the heat pump to continue extracting energy from the ambient air during the defrosting process.

2. The air heat source heat pump according to claim 1, wherein the controller is programmed to switch to a first defrosting mode, and in the first defrosting mode, the distribution of the refrigerant flow through a portion of the plurality of independently controllable flow paths is different from the distribution of the refrigerant flow through a portion of the plurality of independently controllable flow paths in the heating mode, thereby selectively defrosting the first portion of the air heat exchanger, and then returning to the first distribution of the refrigerant flow.

3. The air-source heat pump according to claim 2, wherein the controller switches from the first distribution of refrigerant flow to a second defrost mode after the stepwise defrosting process has returned to the first distribution of refrigerant flow, and in the second defrost mode, the distribution of refrigerant flow through a portion of the plurality of independently controllable flow paths is different from the distribution of refrigerant flow through a portion of the plurality of independently controllable flow paths in the heating mode and the first defrost mode.

4. The air-source heat pump according to claim 2 or 3, wherein the first defrosting mode includes selectively blocking the flow of refrigerant through only some, but not all, of the independently controllable flow paths while maintaining the flow through one or more other of the independently controllable flow paths.

5. The air-source heat pump according to claim 4, wherein the second defrost mode includes restarting the flow of refrigerant through the independently controllable channels whose flow was selectively blocked in the first defrost mode, and selectively blocking the flow through at least a portion of one or more of the independently controllable channels whose flow was maintained in the first defrost mode.

6. The defrosting process includes a first step of controlling the flow control device to selectively block the flow of refrigerant through only a portion, not all, of the independently controllable flow paths, while maintaining the flow through one or more of the other independently controllable flow paths, Subsequently, the flow control device is controlled, In the first step, the flow of refrigerant through the independently controllable channel, whose flow was selectively blocked, is restarted, and The first step involves selectively blocking the flow through at least a portion of the one or more independently controllable channels through which the flow is maintained. An air-source heat pump according to claim 1, including the air-source heat pump described in claim 1.

7. The air-source heat pump according to claim 6, wherein the controller is configured to restart the flow of refrigerant through at least one of the independently controllable channels whose flow was selectively blocked in the first step, before selectively blocking the flow through at least one of the independently controllable channels whose flow was maintained in the first step.

8. The air-source heat pump according to claim 6, wherein the controller is configured to selectively block the flow through at least one of the independently controllable channels whose flow was maintained in the first step, and at the same time to restart the flow of refrigerant through the independently controllable channels whose flow was selectively blocked in the first step.

9. The air-source heat pump according to claim 6, wherein the controller is configured to initiate selective blocking of the flow through at least one of the independently controllable channels whose flow was maintained in the first step, and at the same time initiate restarting the flow of refrigerant through the independently controllable channels whose flow was selectively blocked in the first step.

10. The air heat source heat pump according to any one of claims 1 to 9, wherein the air heat exchanger has at least three independently controllable flow paths for transporting a refrigerant through the air heat exchanger.

11. The air heat source heat pump according to any one of claims 1 to 10, wherein the flow control device is provided with a dedicated expansion valve for each of the independently controllable flow paths.

12. The air-source heat pump according to any one of claims 1 to 11, wherein each of the independently controllable flow paths includes a plurality of conduits for passing a refrigerant.

13. The air heat source heat pump according to claim 12, wherein, with respect to each independently controllable flow path, each of the plurality of conduits is connected in parallel to the refrigerant distribution unit.

14. The air heat source heat pump according to claim 12 or 13, wherein, with respect to each independently controllable flow path within the air heat exchanger, each of the plurality of conduits is grouped into one or more groups consisting of the plurality of conduits.

15. The air-source heat pump according to claim 14, wherein each group of conduits for different independently controllable flow paths is arranged alternately with respect to one another.

16. The air heat source heat pump according to any one of claims 1 to 12, wherein the independently controllable flow paths are arranged alternately with respect to each other, so that in the air heat exchanger, one or more conduits of the first independently controllable flow path are sandwiched on both sides by one or more conduits of different independently controllable flow paths.

17. The air-source heat pump according to any one of claims 1 to 16, wherein the assembly comprises a refrigerant subcooler (306), the refrigerant subcooler (306) is configured to receive little to no airflow, and the refrigerant is configured to flow through the refrigerant subcooler (306) before reaching the flow control device (302).

18. The air heat source heat pump according to any one of claims 1 to 17, wherein the controller (400) is configured to determine, at least in part, the necessity of performing a defrosting operation of the air heat exchanger based on a change in the power consumption characteristics of the heat pump's fan motor (404).

19. The air-source heat pump according to claim 18, wherein the power consumption characteristic is current consumption or rate of change of current consumption.

20. The air-source heat pump according to any one of claims 1 to 19, wherein the controller (400) is configured to selectively block the flow of refrigerant by controlling the flow control device to stop the flow of refrigerant through the selected independently controllable flow path while maintaining the flow through one or more other independently controllable flow paths.

21. The air-source heat pump according to any one of claims 1 to 19, wherein the controller (400) is configured to control the flow control device to selectively block the flow of refrigerant by maintaining a reduced flow of refrigerant through a selected independently controllable flow path while maintaining a flow through one or more other independently controllable flow paths.

22. A method carried out by a controller of an air-source heat pump, wherein the heat pump comprises an air heat exchanger having a plurality of independently controllable flow paths for transporting a refrigerant, and the method is The heat pump is operated in heating mode, and in the heating mode, the air heat exchanger is used to extract energy from the ambient air using the distribution of refrigerant flow through the plurality of independently controllable flow paths. By continuously flowing refrigerant through at least a portion of the independently controllable flow paths, the distribution of refrigerant flow in the plurality of independently controllable flow paths is adjusted to selectively defrost a portion of the air heat exchanger while continuing to extract energy from the ambient air through the operation of the heat pump in heating mode, thereby performing a stepwise defrosting process. Methods that include...

23. The method according to claim 22, wherein adjusting the distribution of the refrigerant flow includes selectively blocking the flow of refrigerant through only a portion of the refrigerant transport conduits of the air heat exchanger while maintaining the flow through the other refrigerant transport conduits of the air heat exchanger.

24. The method according to claim 23, wherein the flow of refrigerant through the refrigerant transport conduit of the air heat exchanger that has been selectively blocked is restarted before selectively blocking the flow through at least a portion of the refrigerant transport conduit of the air heat exchanger that has been selectively blocked.

25. The method according to claim 23, wherein the restart of the flow of refrigerant through the refrigerant transport conduit of the air heat exchanger, whose flow has been selectively blocked, is initiated simultaneously with selectively blocking the flow through at least a portion of the refrigerant transport conduit of the air heat exchanger, whose flow has been maintained.

26. The method according to any one of claims 22 to 25, wherein the heat pump is connected to supply heat to a heating system, and the method further comprises performing the defrosting operation without interrupting the supply of heat to the heating system.

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