A space conditioning system with a defrosting mode

Abstract

The present application proposes a heat pump system (100) comprising one or more compressors (1), one or more first heat exchangers (11) arranged to receive compressed refrigerant from a discharge side of the compressor (1), and a flow switcher (2) arranged to receive condensed refrigerant from the first heat exchanger (11). The system (100) further comprises one or more second heat exchangers (12) and one or more third heat exchangers (13) in refrigerant flow communication with each other at respective first ends thereof, wherein one or more expansion valves (14) are disposed in-between the second heat exchanger (12) and third heat exchanger (13). The second heat exchanger (12) and a third heat exchanger (13) are in refrigerant flow communication with the flow switcher (2) at respective second ends (122, 132) thereof distal to said respective first ends with regard to a refrigerant flow path. The flow switcher (2) is arranged to, in a first mode, provide refrigerant flow communication between the first heat exchanger (11) and second heat exchanger (12), and between the third heat exchanger (13) and the compressor (1); and in a second mode, provide refrigerant flow communication between the first heat exchanger (11) and third heat exchanger (13), and between the second heat exchanger (12) and the compressor (1).

Description

[0001] A SPACE CONDITIONING SYSTEM WITH A DEFROSTING MODE

[0002] Technical field

[0003] The present application relates to a space conditioning system. In particular, the present application relates to a system according to the preamble of claim 1.

[0004] Background

[0005] Machines designed for climate and temperature control are generally built on physical principles of vapor compression cycle. Notwithstanding of specific type and purpose, those machines, which are designed to interact with internal or external air are exposed to phenomenon of ice buildup on surface of evaporator’s coils and fins that occurs at evaporation temperatures of up to 0 °C, that correspond to air temperatures of up to 7 °C. Regular defrost actions are required in order to control this phenomenon.

[0006] There are many technical solutions developed to ease the negative impact from this problem, but in practical terms, one leading method to control ice growth is the Reverse Cycle Defrost (abbreviated as RCD). RCD diverts refrigerant path, so the hot, high pressure refrigerant vapor from compressor is directed not to the first heat exchanger but to the evaporator, where it condenses by melting down ice on external surface whilst first heat exchanger is temporary switched to function as evaporator. Although RCD is considered as an acceptable compromise between energy efficiency and cost of a flow switcher that enables the diversion, the major downside of this method is that implementation of RCD requires regular extraction (or, borrowing) of earlier supplied heat from a heating system. Furthermore, follow up compensation of the borrowed heat is required upon completion of each defrost cycle. Depending to external conditions and controlling algorithms by different manufacturers, RCD usually starts every 40 to 50 minutes and lasts between 5 and 7 minutes.

[0007] Losses associated with removing heat from a heating system are not noticeable by heat pump users, because a heating system with fabric of dwelling carries substantial thermal inertia; so, penalty on true energy cost is not very obvious. However, air inside a cabin of an electric vehicle has very low extent of thermal inertia; and therefore, RCD defrosting is not considered applicable in space conditioning systems or heat pumps that are designed for electric vehicles. The rate of ice growth and its cumulative negative effect on overall performance can vary significantly depending on the climate zone and altitude, which together affects the relative humidity of the air.

[0008] Exceeding growth of ice on evaporator surface causes degradation in performance due to reduction in the air flow through the evaporator fins, that in turn increases the thermal resistance of the evaporator, which is closely related to decreased potential to extract heat from the air passing through evaporator’ fins.

[0009] Notwithstanding of all the negative effects referenced above, RCD is considered as a useful compromise to control frost formation on evaporators of refrigeration and various cooling systems, because heat out of first heat exchangers of these machines is a waste heat. This is different for another type of vapor compression machines known as air source heat pump (abbreviated as ASHP), since heat flow from first heat exchangers is the core function of this type machines.

[0010] Nowadays ASHP is versatile carbon saving heating solution, by allowing extraction of low-grade heat from outdoor air which is a universally available source. Although efficiency of ASHP is lower when compared to heat pumps designed for work with other, more stable sources of primary heat; ASHP is considered as a cost-effective solution due to relatively low capital outlay required for installation.

[0011] When ambient air temperature drops below 7 °C, evaporator of an ASHP requires regular defrosting. At defrosting, the heating system not only stops receiving heat, but also provides heat energy to defrost the evaporator with simultaneous consumption of electrical energy by the compressor. Upon completion of a defrost cycle, ASHP has to work considerable time in order to compensate the amount of heat that is extracted from heating system for melting the ice buildup on evaporator surfaces. Alternatively, US Patent No. 5,269,151 discloses a heat pump system, in which the heat pump requires shutdown at defrosting. And, instead of extracting heat from heating system, it passively uses heat accumulated within thermal energy storage, by heat exchange between phase change material and liquid refrigerant after condensation of the refrigerant at condenser. Although such heat pump system might require less electric power for defrost and doesn’t use heating system as heat source, its disadvantage is that the heating operation has to be stopped at every defrost cycle.

[0012] The above makes difference on impact from both, frost formation and use of the RCD method within ASHP application. Manufacturers employ RCD to enable regular defrosting cycles within various designs of the climatic equipment and particularly, ASHP. Despite all the differences in specific designs, RCD can be performed by use of one or more flow switchers which may include one or more four-way valves actuated by solenoid, or equivalents thereof.

[0013] Summary

[0014] An object of the present invention is to overcome the shortcomings in the prior art. The present application proposes a system and method that enable uninterrupted use of a first heat exchanger during RCD. Thus, the system and method disclosed in the present specification mitigates all the downsides, even the major downside, that are associated with typical RCD. The proposed idea solves the above-mentioned problems associated with defrost cycles with a simple, easy to maintain and low-cost apparatus.

[0015] The present disclosure also includes a range of advantageous features to vapor compression cycle performance within numerous applications, including climatic systems and refrigeration machines. Thus, machines that employ the system and method according to the present application can be considered a separate class of vapor compression machines.

[0016] The most universal characteristic of the common RCD arrangement in a vapor compression machine is that the flow switcher such as a four-way valve is generally located right after the compressor. In a main purpose operation at a primary mode of such prior art apparatus, the refrigerant that is pressurized by the compressor is directed to the condenser as a first heat exchanger, whereas in a defrost cycle the refrigerant is directed to the evaporator. In other words, a refrigerant from a discharge side of the compressor first passes through the flow switcher and only then reaches to the condenser. At switching to a defrosting mode, the flow switcher takes an alternative position to direct the refrigerant to the evaporator instead of the first heat exchanger, notwithstanding the type and purpose of the respective system.

[0017] However, in contrary to the typical positioning, the proposed solution envisages positioning of the four-way valve after the first heat exchanger, so its action is to reverse the direction of refrigerant path between a second heat exchanger that can be arranged to provide thermal communication between the refrigerant and a thermal accumulator and a third heat exchanger that normally functions as evaporator. The thermal accumulator, which can also be named as thermal energy storage (abbreviated as TES) is arranged to be charged whilst subcooling of condensed refrigerant at normal operation, e.g., by including a phase change material such as water. Within the context of the present application, the term normal operation refers to instances where the system is in a primary, main purpose mode of the system such as heating or cooling by thermal communication of a space with first heat exchanger or evaporator, respectively; and a defrost mode corresponds to RCD mode which is a defrosting operation that takes place by alternation from the primary mode.

[0018] Hot condensate from the first heat exchanger is subcooled by transferring heat to the TES. Depending on the degree of subcooling, the heat accumulated in the TES can exceed 15% of the first heat exchanger capacity, which covers the need for heat capacity to ensure cyclic defrosting of the evaporator. At the same time, in a conventional vapor compression machine, including air source heat pumps (abbreviated as ASHP), most of the heat content in the condensate is lost at sudden pressure reduction in a respective expansion valve. So, the present application permits accumulation of heat without any additional energy consumption but for account of loss reduction.

[0019] In the defrost mode (that is, RCD), the first heat exchanger continues its duty as condenser for nonstop delivery of heat to heating system, the second heat exchanger that can be provided with TES works as a second evaporator and hot condensate from first heat exchanger is supplied directly to the third heat exchanger that functions as evaporator in the first mode, for defrosting the same by subcooling of the refrigerant.

[0020] The absence of any need to borrow heat from the heating system for RCDs, allows strategy of preventive defrosts with shorter periods between RCDs. ASHP systems are usually arranged to run defrost cycles within periods from 40 minutes to 50 minutes. Reducing the step between RCD cycles in such prior art systems will require additional heat extraction from the heating apparatus, which will deteriorate proportion of the compressor's useful work, since more electricity will be spent on defrosting and compensation for the heat borrowed from the heating system. In case of an alternative heat pump system described in the US Patent No. 5,269,151 stopping the system’s compressor too often will dramatically reduce heat supply to the heating system, which in its turn leads to insufficient heat accumulation at TES that would be required for more frequent defrosts. The present solution allows reduction of time between defrost cycles to 30 minutes, and in case of high outdoor air humidity, such as 80% or higher relative humidity, periods between RCD cycles can be even reduced to 15 minutes. Another advantage of the present solution is that at switching to RCD mode, heat supply from the first heat exchanger to a heating system doesn’t only remain uninterrupted but also efficiency of the system in defrost mode is increased. This is because instead of a cold outside air, system uses heat accumulated in the process of subcooling, which has substantially higher temperature grade than an outside air.

[0021] Brief description of the figures

[0022] The accompanying drawings are given solely for the purpose of exemplifying the invention whose advantages over prior art were outlined above and will be explained in detail hereinafter:

[0023] Fig.1 schematically represents an exemplary embodiment of the system according to the present invention in a first mode.

[0024] Fig.2 represents the embodiment from Fig.1 in a second mode.

[0025] Fig.3 schematically represents another exemplary embodiment of the system according to the present invention in the first mode, which corresponds to a heater in a respective main operation.

[0026] Fig.4 is the embodiment depicted in Fig.3 in the second mode that corresponds to a defrosting operation.

[0027] Fig.5 schematically represents a further exemplary embodiment of the system according to the present invention in the second mode, which corresponds to a chiller in respective main operation.

[0028] Fig.6 is a simplified schematical representation of the system according to the present invention, showing the heat transfer directions in the second heat exchanger and third heat exchanger with respect to the refrigerant at the first mode.

[0029] Fig.7 represents the system from Fig.6, showing the heat transfer directions in the second heat exchanger and third heat exchanger with respect to the refrigerant at the first mode.

[0030] Fig.8 illustrates a cycle on an enthalpy-pressure diagram without subcooling of a refrigerant.

[0031] Fig.9 illustrates a cycle on an enthalpy-pressure diagram with subcooling of the refrigerant.

[0032] Detailed description

[0033] Referring to the figures summarized above, the present invention proposes a space conditioning system (100) comprising a compressor (1 ), a first heat exchanger (11 ) arranged to receive compressed refrigerant from a discharge side of the compressor

[0034] (I ), and a flow switcher (2) arranged to receive condensed refrigerant from the first heat exchanger (11 ). The system (100) further comprises a second heat exchanger (12) and a third heat exchanger (13) in refrigerant flow communication with each other at respective first ends thereof, wherein one or more expansion valves (14) are disposed in-between the second heat exchanger (12) and third heat exchanger (13). Thus, the second heat exchanger (12) and third heat exchanger (13) are arranged in series. The second heat exchanger (12) and third heat exchanger (13) are in refrigerant flow communication with the flow switcher (2) at respective second ends (122, 132) thereof distal to said respective first ends (121 , 131 ) with regard to a refrigerant flow path. So, the second heat exchanger (12) can be considered to guide the refrigerant stream to flow between a first end (121 ) and a second end (122) thereof; and the third heat exchanger (13) can be considered to guide the refrigerant stream to flow between a first end (131 ) and a second end (132) thereof.

[0035] The flow switcher (2) is arranged to:

[0036] - in a first mode, provide refrigerant flow communication between the first heat exchanger (11 ) and second heat exchanger (12), and between the third heat exchanger (13) and the compressor (1 ); and

[0037] - in a second mode, provide refrigerant flow communication between the first heat exchanger (11 ) and third heat exchanger (13), and between the second heat exchanger (12) and the compressor (1 ).

[0038] Fig.1 schematically represents an exemplary embodiment of the system (100) according to the present invention in the first mode. Here, the first mode corresponds to the main purpose primary operation mode of the system (100). Refrigerant stream from the discharge side of the compressor (1 ) is directed to the first heat exchanger (11 ), which serves as a condenser. The condensed refrigerant from the first heat exchanger

[0039] (II ) is transferred to the second heat exchanger (12) through the flow switcher (2). Here, the second heat exchanger (12) serves for subcooling of the condensed refrigerant. Heat extracted from the refrigerant at the second heat exchanger (12) can be transferred to a thermal energy storage. Thus, the second heat exchanger (12) can be arranged to provide thermal communication between the refrigerant and a thermal energy storage. The thermal energy storage can include a phase change material, e.g., water, a brine, a wax, or any composition that can be used in thermal batteries or thermal accumulators such as ice packs or ice accus. At an instance where the thermal energy storage is in a frozen state at the first mode, the heat extracted from the refrigerant at the second heat exchanger (12) can be absorbed by the thermal energy storage not only in the form of sensible heat, but also as latent heat, thereby providing an enhanced extent of subcooling. The subcooled refrigerant from the second heat exchanger (12) passes through the expansion valve (14), and the expanded refrigerant from the expansion valve (14) is transferred to the third heat exchanger (13).

[0040] In the first mode, the third heat exchanger (13) serves as an evaporator for the refrigerant. Dependent mostly to the ambient conditions around outer surfaces of the third heat exchanger (13), such as temperature and relative humidity of ambient air in contact with such outer surfaces, frost formation takes place thereon throughout the operation of the system (100) in the first mode. The system (100) is arranged for being switched from the first mode to the second mode, thereby initiating a defrost operation without interruption of the function of the first heat exchanger (11 ).

[0041] Fig.2 represents the embodiment from Fig.1 in the second mode. In the second mode, the compressor (1 ) continues feeding the first heat exchanger (11 ) with compressed refrigerant. Heat is rejected from the refrigerant passing through the first heat exchanger (11 ) without interruption. Condensed refrigerant from the first heat exchanger (11 ) is directed to the third heat exchanger (13). Heat transfer takes place from the refrigerant to melt ice buildup around the third heat exchanger (13), thereby effecting a defrost operation whilst subcooling the refrigerant. Thanks to the subcooling of the refrigerant at the third heat exchanger (13) when in the second mode, an enhanced evaporation capacity is maintained in the second mode. The subcooled refrigerant from the third heat exchanger (13) is passed through the expansion valve (14), and the expanded refrigerant is then transferred to the second heat exchanger (12).

[0042] In the case where the second heat exchanger (12) is provided with a thermal energy storage, heat accumulation increases the temperature of the thermal energy storage during operation in the first mode. Thus, the thermal energy storage is at a relatively high temperature at initiation of the second mode. Accordingly, in the second mode, the second heat exchanger (12) serves not only as an evaporator but also as a subcooler to the refrigerant. Thus, in the second mode, an enhanced evaporating capacity is available at the second heat exchanger (12). Heat transfer from the thermal energy storage to the refrigerant at the second heat exchanger (12) results in cooling to partial or complete freezing of the thermal energy storage media during the second mode; thereby preparing the thermal energy storage for serving with an enhanced capacity when the system (100) is switched back to the first mode. Evaporated refrigerant from the second heat exchanger (12) is then transferred to a suction side of the compressor (1 ) through the flow switcher (2), to complete the cycle. The defrosting operation can be ceased by shifting back to the first mode.

[0043] The system (100) can be provided with a controller (3) that is arranged for switching between the first mode and second mode based on one or more process parameters. The one or more process parameters can include one or more selected from a temperature at the first heat exchanger (11 ), a temperature at the second heat exchanger (12) and a temperature at the third heat exchanger (13). Shifting between the first mode and the second mode can be performed by a controller (3) that can be in data communication with a temperature metering device at the third heat exchanger (13). In such case, transitions between first and second modes are based on an outer surface temperature at the third heat exchanger (13) or time required for defrost.

[0044] Although the subordination with regard to the controller (3) can be shown with dotted lines in the respective drawings, it can be admitted that a person skilled in the art of process control can contemplate all the control parameters and data and control communication lines between the controller (3) and any of relevant features of the system (100), in order to implement the operation of the first and second modes and duly switching within these first and second modes. Therefore, possible data and control communication lines are normally not shown in appended drawings.

[0045] The third heat exchanger (13) can be arranged to, in the first mode, transfer heat extracted from air to the refrigerant. Thus, in the first mode, the third heat exchanger (13) is considered suitable for being employed in cooling of air in a refrigerator’s camera, a supermarket shelf, or in HVAC-cooling. Any embodiment of the system (100) can further comprise one or more fans for propelling air onto the third heat exchanger (13), to arrange forced convection heat transfer from the third heat exchanger (13). The one or more fans can be arranged to pause when in defrost operation, via the controller.

[0046] In a possible embodiment of the system (100) can be considered to comprise the following:

[0047] - a closed-circuit pipework for provision of a flow path to a refrigerant,

[0048] - a compressor (1 ) for compressing the refrigerant,

[0049] - a first heat exchanger (11) for rejection of heat from the refrigerant from the first heat exchanger (1 ), thereby effecting a condensation of the refrigerant, - a second heat exchanger (12) arranged for provision of thermal communication between the refrigerant and a thermal energy storage,

[0050] - a third heat exchanger (13) arranged for provision of thermal communication between the refrigerant and ambient air, and

[0051] - an expansion valve (14) for passage of the refrigerant whilst flowing between the second heat exchanger (12) and the third heat exchanger (13).

[0052] In such possible embodiment, the pipework can comprise the following:

[0053] - a first conduit (41 ) for feeding compressed refrigerant from the discharge side of the compressor (1 ) to the first heat exchanger (11 ),

[0054] - a second conduit (42) for removing the refrigerant from the first heat exchanger (11 ).

[0055] - a third conduit (43) for feeding the refrigerant to the suction side of the compressor (1 ),

[0056] - a fourth conduit (44) for refrigerant flow communication between the second heat exchanger (12) and second exchanger (13), the expansion valve (14) being disposed on the fourth conduit (44),

[0057] - a fifth conduit (45) connected to a distal side of the second heat exchanger (12) with regard to the fourth conduit (44), and

[0058] - a sixth conduit (46) connected to a distal side of the third heat exchanger (14) with regard to the fourth conduit (44).

[0059] The pipework can be provided with a flow switcher (2) at a distal end of the second conduit (42) with regard to the first heat exchanger (11 ), the flow switcher (2) being switchable between the first mode and second mode. The flow switcher (2) can be arranged to:

[0060] - in the first mode, provide refrigerant flow communication between the second conduit (42) and fifth conduit (45), and between the sixth conduit (46) and the third conduit (43); and

[0061] - in the second mode, provide refrigerant flow communication between the second conduit (42) and sixth conduit (46), and between the fifth conduit (45) and the third conduit (43).

[0062] Fig.3 schematically represents another exemplary embodiment of the system (100) according to the present invention in the first mode, which corresponds to a heater in a respective primary operation mode. As shown in Fig.3, the first heat exchanger (11 ) can be optionally adapted to arrange thermal communication between one or more secondary fluid lines (20) and refrigerant at the first heat exchanger (11 ). Here, the first heat exchanger (11 ), second heat exchanger (12) and third heat exchanger (13) can be respectively considered to serve as a condenser, a subcooler and an evaporator for the refrigerant, as in the first mode that is discussed above with reference to Fig .1 .

[0063] The secondary fluid can be water (e.g., sanitary water), such that the heat rejected from the refrigerant at the first heat exchanger (11 ) is transferred to the water which can be then utilized as heated tap water. Alternatively, or furthermore, such secondary fluid can be a central heating fluid, such that the heat rejected from the refrigerant at the first heat exchanger (11 ) is transferred to the central heating fluid. Hence, the present application further proposes a system (100) that is arranged for heating sanitary water and / or a central heating fluid. In other words, the present application further proposes a system (100) that is -suitable for being- integrated to one or more secondary fluid lines (20), that can be arranged for guiding sanitary water and / or one or more fluids for being circulated in one or more central heating systems. As the system (100) is arranged for non-stop running of the first heat exchanger (11 ) at both of the first and second modes, no interruption takes place in heat transfer from refrigerant to sanitary water or central heating fluid at a defrosting operation.

[0064] As shown in Fig.3, the second heat exchanger (12) can be optionally adapted to arrange thermal communication between the thermal energy storage and a tertiary fluid that can be streamed in a tertiary fluid line (30). By absorption of heat from the tertiary fluid by the thermal energy storage at the second heat exchanger (12), the tertiary fluid cools down. Such tertiary fluid can be utilized in a fluid-cooling circuit. The tertiary fluid can be air, water or brine. The fluid-cooling circuit can be employed in information technologies-related cooling, e.g., at a data centre; cooling of central processing units, pharmaceuticals, or HVAC-cooling. The system (100) that includes such second heat exchanger (12) that provides thermal communication between the thermal energy storage and a tertiary fluid, is particularly preferable for being used in relatively warm climates and / or warm seasons. In a possible embodiment, the tertiary fluid can be sanitary water, e.g., for provision of cooled tap water. Hence, the present application further proposes a system (100) that is arranged for thermal communication between one or more tertiary fluids and refrigerant at the second heat exchanger (12). In other words, the present application further proposes a system (100) that is -suitable for being- integrated to one or more tertiary fluid lines (30), for heat transfer between refrigerant at the second heat exchanger (12) one or more tertiary fluids in the one or more tertiary fluid lines (30) when the system (100) is in use.

[0065] Fig.4 shows the embodiment depicted in Fig.3 in the second mode that corresponds to a defrosting operation. Here, the first heat exchanger (11 ) serves as a condenser, the second heat exchanger (12) serves as an evaporator and the third heat exchanger (13) that undergoes defrosting serves as a subcooler for the refrigerant. So, heat rejection to the secondary fluid at the first heat exchanger (12), and where applicable, heat absorption from the tertiary fluid at the second heat exchanger (12) are maintained without interruption at defrosting of the third heat exchanger (13).

[0066] Fig.5 schematically represents a further exemplary embodiment of the system according to the present invention in the second mode. Here, the system (100) can be considered as a chiller in respective main operation mode. Similar to that discussed above with reference to Fig.3; the first heat exchanger (11 ) can be adapted to arrange thermal communication between the refrigerant and a secondary fluid that can be streamed in a secondary fluid line (20), and / or the second heat exchanger (12) can be adapted to arrange thermal communication between the thermal energy storage and a tertiary fluid that can be streamed in a tertiary fluid line (30). In the main operation mode of the present embodiment, the first heat exchanger (11 ), the second heat exchanger (12) and the third heat exchanger (13) respectively serve as a desuperheater, an evaporator and a condenser for the refrigerant. In the case of a relatively high load, also condensation of the refrigerant to a limited extent can take place at the first heat exchanger (11 ). Since the second heat exchanger (12) serves as evaporator when in the second mode of such embodiment, frost buildup can take place at the second heat exchanger (12).

[0067] Defrosting of the second heat exchanger (12), and / or where applicable, avoiding frost of a tertiary fluid, takes place when the system (100) is switched to the first mode to alter the flow direction of the refrigerant.

[0068] When switched to the first mode, the de-superheated refrigerant from the first heat exchanger (11 ) is transferred via the flow switcher (2) to the second heat exchanger (12). De-superheated refrigerant with a relatively high temperature rejects heat at least in the form of latent heat, or also in the form of sensible heat if the system (100) is arranged for subcooling of the refrigerant at the second heat exchanger (12) when in the first mode. Defrosting and / or avoidance of frost formation is thus achieved. The condensed or subcooled refrigerant is then passed through the one or more expansion valves (14) and transferred to the third heat exchanger (13), which serves as evaporator when in the first mode.

[0069] Fig.6 is a simplified schematical representation of the system according to the present invention, showing the heat transfer directions in the second heat exchanger (12) and third heat exchanger (13) with respect to the refrigerant at the first mode. The compressor (1 ) and first heat exchanger (11 ) are not shown in order to emphasize that the undisturbed operation of the first heat exchanger (11 ) and that the heat transfer directions in the second heat exchanger (12) and third heat exchanger (13) with respect to the refrigerant are merely dependent to the state of the flow switcher (2). Fig.7 represents the system from Fig.6, showing the altered heat transfer directions in the second heat exchanger (12) and third heat exchanger (13) with respect to the refrigerant at the second mode.

[0070] Fig.8 illustrates a cycle on an enthalpy-pressure diagram without subcooling of a refrigerant. Line a-c represents the evaporation capacity, whereas from a to b vapor quality of the refrigerant increases until complete evaporation, and from b to c the gaseous refrigerant is superheated. Line c-d represents compression of the refrigerant at the compressor (1 ). Line d-f represents heat of rejection whereas from d to e enthalpy extraction from the gaseous refrigerant takes place until respective dew point, and from e to f the vapor quality of the refrigerant decreases until complete condensation. Line f-a represents expansion of the condensed refrigerant to complete the cycle.

[0071] Fig.9 illustrates a cycle on an enthalpy-pressure diagram with subcooling of the refrigerant. Line h-c represents the evaporation capacity, whereas from h to b vapor quality of the refrigerant increases until complete evaporation, and from b to c the gaseous refrigerant is superheated. Line c-d represents compression of the refrigerant at the compressor (1 ). Line d-f represents heat of rejection whereas from d to e enthalpy extraction from the gaseous refrigerant takes place until respective dew point, and from e to f the vapor quality of the refrigerant decreases until complete condensation. Line f-h represents subcooling of the condensed, liquid refrigerant. Line g-h represents expansion of the subcooled refrigerant to complete the cycle. The subcooling results in a lower extent of enthalpy at beginning of the evaporation, thereby providing an increased evaporation capacity. Accordingly, the system (100) is preferably arranged for subcooling of the refrigerant as discussed above with reference to Fig.1 to Fig.5. It should be noted that in vapor compression cycle thermodynamics, there are three factors affecting the subcooling of the condensate in two consecutive stages of the cycle: a) Subcooling in a condenser: This type of subcooling occurs at the outlet of the condenser due to a counterflow of two media in the heat exchanger. This effect can be specifically achieved this effect in order to prevent the extremely undesirable refrigerant flashing in a condensate line between the condenser and an expansion valve. Flashing in this section of the cycle can occur due to slight pressure losses associated with resistance in the pipework, coupled with additional subcooling, which is described below. b) Natural subcooling: Temperature of condensate entering the pipe after the condenser may vary from 35 °C to 55 °C in different operating modes, in some cases temperature can be lower or much higher, while the ambient air temperature may have a negative value. The temperature difference between the two media causes a slight decrease in the temperature of the condensate without any influence on the pressure, resulting in an extent of subcooling. c) Artificial subcooling: Subcooling of condensate with use of a special heat exchanger can be maximised; under certain conditions, share of this type of subcooling can exceed 97% of the total effect by all three factors affecting total subcooling. The thermal energy storage discussed with reference to possible embodiments of the system (100) according to the present application works with this particular form of condensate subcooling.

[0072] Actual subcooling affects the overall efficiency of a vapour compression machine with a designated purpose of heating or cooling. Yet, if direct effect of the subcooling on increase in cooling capacity of a system (100) designed for cooling or refrigeration purposes is visually high, the same effect on a system (100) designed for heating purposes is not so obvious. That’s because increased evaporator capacity has no direct relation to the increase in heating capacity of the first heat exchanger. However, the introduction of subcooled refrigerant into the evaporator has a positive effect on quality of heat exchange process with cold air, which is greatly enhances the overall efficiency of a system (100) for heating purposes.

[0073] The system (100) according to the present disclosure can be considered in accordance with one or more of the following aspects: - The system (100) can include three heat exchangers that are the first heat exchanger (11 ), second heat exchanger (12) and third heat exchanger (13), respectively. At one of the first mode or second mode these three heat exchangers can serve as an evaporator, a condenser and a subcooler; where respective functions of the second heat exchanger (12) and third heat exchanger (13) (which can be considered as heat exchangers with their evaporator and subcooler functions) can be swapped depending to a selected one of paths of the refrigerant stream being regulated over the flow switcher (2), which is preferably a single four-way valve.

[0074] - By being directly fed from the discharge side of the compressor (1 ) in an uninterrupted fashion even at switching between the first mode and second mode, the first heat exchanger (11 ) can be considered to provide heat exchanging function with high refrigerant pressure, without interruption even when switched between modes for defrosting operation. In the embodiments where the first heat exchanger (11 ) is a condenser, it can serve for non-stop heating or in the case with a secondary fluid line (20), for non-stop production of hot water, that can be used as hot sanitary tap water, or as heating fluid for central heating systems.

[0075] - In a preferred embodiment, the first heat exchanger (11 ) serves as a desuperheater and condenser (not as an evaporator) regarding the refrigerant in both of the first and second modes, for (non-stop-) production of hot water, that can be used as hot sanitary tap water, or as heating fluid for central heating systems.

[0076] - In any of the embodiments, the flow switcher (2) can comprise a plurality of valves that are arranged for flow diversion, yet preferably the flow switcher (2) comprises a single, four-way valve.

[0077] - In one or more of the preferred embodiments, liquid refrigerant stream leaving the first heat exchanger (11 ) that uninterruptedly serves as condenser, can be directed in an alternated fashion between the first and second modes via the flow switcher (2), for swapping the functions of the second heat exchanger (12) and third heat exchanger (13) as a subcooler and an evaporator in an interchangeable fashion.

[0078] - The system (100) can be preferably adapted to supply air heated by thermal contact with the first heat exchanger (11 ) to an electric vehicle cabin. With this approach, it is rendered unnecessary to extract earlier supplied warm air from the cabin in order to defrost an evaporator as an external heat exchanger. Accordingly, the present application proposes a system (100) as defined in the respective independent claim, in which the first heat exchanger (11 ) is further arranged to heat air to be supplied to a cabin of an electric vehicle. Furthermore, the present application proposes an electric vehicle with a cabin, the electric vehicle being provided with the system (100) wherein the first heat exchanger (11) is in thermal communication with air to be supplied into the cabin, when the system (100) is in use. The present application further proposes a method as defined in the respective independent claim, wherein the method further includes heating of air to be supplied into an electric vehicle cabin by thermally communicating with refrigerant at the first heat exchanger (11 ).

[0079] - In any embodiment of the system (100) according to the present specification, the expansion valve (14) can comprise a single bi-directional electronic expansion valve. Alternatively, the expansion valve (14) can comprise a couple of electronic expansion valves that are arranged be operated in tandem, wherein either one of them is ceased and the other one of them is operational in terms of expanding the refrigerant stream in respective first mode or second mode, in order to expand refrigerant stream in directions with regard to each other; that is, from the second heat exchanger (12) to the third heat exchanger (13) or vice versa.

[0080] - In any embodiment of the system (100), the refrigerant pipework can be provided with one or more receivers and / or filter driers.

[0081] - Any embodiment of the system (100) can be provided with one or more of the following features:

[0082] - suction line accumulators,

[0083] - suction line accumulators with integrated heat exchangers, and

[0084] - suction line heat exchangers, that can be located on low pressure vapor refrigerant portions of the pipework.

[0085] Said low pressure portions can be considered the portions of the pipework from the expansion valve (14) to the suction side of the compressor (1 ) with regard to a flow direction of the refrigerant. For instance, one or more of said features can be disposed on the third conduit (43); that is, in-between the flow switcher (2) and the suction side of the compressor (1 ).

[0086] In accordance with the embodiments of system (100) that are discussed above, the present application also proposes a method for space conditioning with a system (100) that has a first mode and a second mode, wherein the first mode comprises the following sequential steps l-VII:

[0087] I. directing a refrigerant stream from a discharge side of one or more compressors (1 ) to one or more first heat exchangers (11 ) where heat transfer takes place to or from the refrigerant,

[0088] II. passing the refrigerant stream from the first heat exchanger (11 ) through a flow switcher (2),

[0089] III. directing the refrigerant stream from the flow switcher (2) to one or more second heat exchangers (12) where heat transfer takes place to or from the refrigerant, IV. passing the refrigerant stream from the second heat exchanger (12) through one or more expansion valves (14) where an isenthalpic expansion of the refrigerant can take place,

[0090] V. directing the refrigerant stream from the expansion valve (14) to one or more third heat exchangers (13) where heat transfer takes place to or from the refrigerant,

[0091] VI. passing the refrigerant stream from the third heat exchanger (13) through the flow switcher (2),

[0092] VII. directing the refrigerant stream from the flow switcher (2) to a suction side of the compressor (1 ).

[0093] The method further comprises switching from the first mode to second mode by alteration of the positioning of the flow switcher, and the second mode comprises the following sequential steps, thereby achieving uninterrupted operation of the first heat exchanger (11 ): i. directing the refrigerant stream from discharge side of one or more compressors (1 ) to one or more first heat exchangers (11 ) where heat transfer takes place to or from the refrigerant, ii. passing the refrigerant stream from the first heat exchanger (11 ) through a flow switcher (2), iii. directing the refrigerant stream from the flow switcher (2) to the one or more third heat exchangers (13) where heat transfer takes place to or from the refrigerant, iv. passing the refrigerant stream from the third heat exchanger (13) through one or more expansion valves (14) where an isenthalpic expansion of the refrigerant can take place, v. directing the refrigerant stream from the expansion valve (14) to the one or more second heat exchangers (12) where heat transfer can take place to or from the refrigerant, vi. passing the refrigerant stream from the second heat exchanger (12) through the flow switcher (2), vii. directing the refrigerant stream from the flow switcher (2) to the suction side of the compressor (1 ).

[0094] A preferred version of the method further comprises provision of thermal communication between one or more secondary fluid lines (20) and refrigerant at the first heat exchanger (11 ). Preferably, the method can comprise guiding sanitary water and / or one or more fluids for being circulated in one or more central heating systems through said one or more secondary fluid lines (20). A preferred version of the method further comprises provision of thermal communication between the refrigerant and a thermal energy storage at the second heat exchanger (12). Preferably, the method can comprise the arrangement of a phase changing material e.g., water, a brine, a wax, or any composition that is suitable for use in thermal batteries or thermal accumulators such as ice packs or ice accus as the thermal energy storage as discussed above. In a preferred version, the method can comprise provision of thermal communication between the thermal energy storage and one or more tertiary fluid lines (30) at the second heat exchanger (12).

[0095] In a preferred version of the method, the switching between the first mode and second mode can be arranged on the basis of one or more process parameters selected from a temperature at the first heat exchanger (11 ), a temperature at the second heat exchanger (12), a temperature at the third heat exchanger (13), and a duration of defrost operation. Preferably, the switching between the first mode and second mode is arranged on the basis of the temperature at the third heat exchanger (13) as the process parameter.

[0096] As discussed above, a preferred version of the method can include heating of air to be supplied into a cabin of an electric vehicle, at the first heat exchanger (11 ). This is performed by thermally communicating the air to be supplied into the cabin with refrigerant at the first heat exchanger (11 ). Taking the set of features that constitute the independent method claim into consideration, the present disclosure enables the implementation of a defrosting operation in conditioning of electric vehicle cabins. Switching between the first mode and second mode does not interrupt the heating of air to be supplied into the electric vehicle cabin.

[0097] Referring to the content provided throughout the present specification, the aforementioned problems are solved with the embodiments of the system (100) and variations of the method according to the present invention. List of reference si

[0098] 1 compressor

[0099] 2 flow switcher

[0100] 3 controller

[0101] 11 first heat exchanger

[0102] 12 second heat exchanger

[0103] 13 third heat exchanger

[0104] 14 expansion valve

[0105] 20 secondary fluid line

[0106] 30 tertiary fluid line

[0107] 41 first conduit

[0108] 42 second conduit

[0109] 43 third conduit

[0110] 44 fourth conduit

[0111] 45 fifth conduit

[0112] 46 sixth conduit

[0113] 100 system

[0114] 121 first end (of the second heat exchanger)

[0115] 122 second end (of the second heat exchanger)

[0116] 131 first end (of the third heat exchanger)

[0117] 132 second end (of the third heat exchanger)

Claims

CLAIMS1. A space conditioning system (100) comprising one or more compressors (1 ), one or more first heat exchangers (11 ) arranged to receive compressed refrigerant from a discharge side of the compressor (1 ), and a flow switcher (2) arranged to receive condensed refrigerant from the first heat exchanger (11 ); characterized in that the system (100) further comprises one or more second heat exchangers (12) and one or more third heat exchangers (13) in refrigerant flow communication with each other at respective first ends (121 , 131 ) thereof; the system (100) further comprises one or more expansion valves (14) disposed inbetween the second heat exchanger (12) and third heat exchanger (13); wherein the second heat exchanger (12) and third heat exchanger (13) are in refrigerant flow communication with the flow switcher (2) at respective second ends (122, 132) thereof distal to said respective first ends (121 , 131 ) with regard to a refrigerant flow path; the flow switcher (2) is arranged to: in a first mode, provide refrigerant flow communication between the first heat exchanger (11 ) and second heat exchanger (12), and between the third heat exchanger (13) and the compressor (1 ); and in a second mode, provide refrigerant flow communication between the first heat exchanger (11 ) and third heat exchanger (13), and between the second heat exchanger (12) and the compressor (1 ).

2. System according to claim 1 , wherein the first heat exchanger (11 ) is adapted to arrange thermal communication between one or more secondary fluid lines (20) and refrigerant at the first heat exchanger (11 ).

3. System according to claim 2, wherein the one or more secondary fluid lines (20) are arranged for guiding sanitary water and / or one or more fluids for being circulated in one or more central heating systems.

4. System according to any of claims 1 to 3, wherein the second heat exchanger (12) is arranged to provide thermal communication between the refrigerant and a thermal energy storage.

5. System according to claim 4, wherein the thermal energy storage includes a phase changing material.

6. System according to claim 5, wherein the phase changing material is selected from water, a brine, a wax, or a composition suitable for use in thermal batteries or thermal accumulators.

7. System according to any of claims 4 to 6, wherein the second heat exchanger (12) is arranged to provide thermal communication between the thermal energy storage and one or more tertiary fluid lines (30).

8. System according to any of claims 1 to 7, provided with a controller (3) that is arranged for switching between the first mode and second mode based on one or more process parameters selected from a temperature at the first heat exchanger (11 ), a temperature at the second heat exchanger (12), a temperature at the third heat exchanger (13), and a duration of a defrost operation.

9. System according to any of claims 1 to 8, comprising a closed-circuit pipework for provision of a flow path to a refrigerant, the pipework comprises:- a first conduit (41 ) for feeding compressed refrigerant from the discharge side of the compressor (1 ) to the first heat exchanger (11 ),- a second conduit (42) for removing the refrigerant from the first heat exchanger (11 ).- a third conduit (43) for feeding the refrigerant to a suction side of the compressor (1 ),- a fourth conduit (44) for communicating the refrigerant between the second heat exchanger (12) and second exchanger (13), the expansion valve (14) being disposed on the fourth conduit (44),- a fifth conduit (45) connected to a distal side of the second heat exchanger (12) with regard to the fourth conduit (44),- a sixth conduit (46) connected to a distal side of the third heat exchanger (14) with regard to the fourth conduit (44), and- the flow switcher (2) at a distal end of the second conduit (42) with regard to the first heat exchanger (11 ); wherein the flow switcher (2) is arranged for:- in the first mode, provide refrigerant flow communication between the second conduit (42) and fifth conduit (45), and between the sixth conduit (46) and the third conduit (43); and- in the second mode, provide refrigerant flow communication between the second conduit (42) and sixth conduit (46), and between the fifth conduit (45) and the third conduit (43).

10. System according to any of claims 1 to 9, wherein the first heat exchanger (11 ) is arranged to heat air to be supplied to a cabin of an electric vehicle.

11. An electric vehicle with a cabin, wherein the electric vehicle is provided with the system (100) according to any of claims 1 to 10, and the first heat exchanger (11 ) is in thermal communication with air to be supplied into the cabin when the system (100) is in use.

12. A method for space conditioning with a system (100) that has a first mode and a second mode, wherein the first mode comprises the following sequential steps I- VII:I. directing a refrigerant stream from a discharge side of one or more compressors (1 ) to one or more first heat exchangers (11 ) where heat transfer takes place to or from the refrigerant,II. passing the refrigerant stream from the first heat exchanger (11 ) through a flow switcher (2),III. directing the refrigerant stream from the flow switcher (2) to one or more second heat exchangers (12) where heat transfer takes place to or from the refrigerant,IV. passing the refrigerant stream from the second heat exchanger (12) through one or more expansion valves (14),V. directing the refrigerant stream from the expansion valve (14) to one or more third heat exchangers (13) where heat transfer takes place to or from the refrigerant,VI. passing the refrigerant stream from the third heat exchanger (13) through the flow switcher (2),VII. directing the refrigerant stream from the flow switcher (2) to a suction side of the compressor (1 ); the method further comprising switching from the first mode to second mode by alteration of the positioning of the flow switcher, and the second mode comprises the following sequential steps i-vii: i. directing the refrigerant stream from discharge side of one or more compressors (1 ) to one or more first heat exchangers (11 ) where heat transfer takes place to or from the refrigerant,II. passing the refrigerant stream from the first heat exchanger (11 ) through a flow switcher (2), ill. directing the refrigerant stream from the flow switcher (2) to the one or more third heat exchangers (13) where heat transfer takes place to or from the refrigerant, iv. passing the refrigerant stream from the third heat exchanger (13) through one or more expansion valves (14), v. directing the refrigerant stream from the expansion valve (14) to the one or more second heat exchangers (12) where heat transfer takes place to or from the refrigerant,vi. passing the refrigerant stream from the second heat exchanger (12) through the flow switcher (2), vii. directing the refrigerant stream from the flow switcher (2) to the suction side of the compressor (1 ).

13. Method according to claim 12, further comprising provision of thermal communication between one or more secondary fluid lines (20) and refrigerant at the first heat exchanger (11 ).

14. Method according to claim 13, wherein the method comprises guiding sanitary water and / or one or more fluids for being circulated in one or more central heating systems through said one or more secondary fluid lines (20).

15. Method according to any of claims 12 to 14, further comprising provision of thermal communication between the refrigerant and a thermal energy storage at the second heat exchanger (12).

16. Method according to claim 15, comprising arrangement of a phase changing material selected from water, a brine, a wax, or a composition suitable for use in thermal batteries or thermal accumulators, as the thermal energy storage.

17. Method according to any of claims 15 or 16, further comprising provision of thermal communication between the thermal energy storage and one or more tertiary fluid lines (30) at the second heat exchanger (12).

18. Method according to any of claims 12 to 17, wherein the switching between the first mode and second mode is arranged on the basis of one or more process parameters selected from a temperature at the first heat exchanger (11 ), a temperature at the second heat exchanger (12) and a temperature at the third heat exchanger (13).

19. Method according to claim 18, wherein the switching between the first mode and second mode is arranged on the basis of the temperature at the third heat exchanger (13) as the process parameter.

20. Method according to any of claims 12 to 19, including heating of air to be supplied into a cabin of an electric vehicle, by thermally communicating the air with refrigerant at the first heat exchanger (11 ).

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