Patent Application
20250003658
This application claims the benefit of and priority to Danish Application No. PA 2023 30106, filed Jun. 28, 2023, which is hereby incorporated by reference in its entirety.
The present invention relates to a method for defrosting an air source heat pump comprising a plurality of outdoor evaporators each comprising a number of coils each comprising fins and pipes. The present invention also relates to an air source heat pump comprising a plurality of outdoor evaporators each comprising a number of coils, the heat pump comprising a defrost system that applies a defrosting medium to provide thermal energy to defrost the coils.
Different defrost control strategies have been used in air source heat pumps with the time control method being the most common one. These control strategies include time control, pressure difference control, and temperature control.
Defrosting is an energy demanding process. Accordingly, one would like to wait as long as possible to initiate a defrosting process. The performance, however, decreases as the frost is created and moreover, it is difficult to defrost if one waits too long.
The prior art methods for controlling the defrosting of heat pumps detect a fin temperature and apply it for determining when to start and stop the defrost procedure. These systems are, however, based on a single or two control methods. Accordingly, the prior art solutions have a poor performance.
Thus, there is a need for a method and an air source heat pump which enables a higher performance, and which reduces or even eliminates the above mentioned disadvantages of the prior art.
A method according to the present disclosure is a method for defrosting an air source heat pump comprising a plurality of outdoor evaporators each comprising a number of fans and a number of coils each comprising fins and pipes, wherein the heat pump comprises a defrost system that applies a defrosting medium to provide thermal energy to defrost the coils, the method comprising:
Hereby, it is possible to provide a method that enables a higher performance, and which reduces or even eliminates the above mentioned disadvantages of the prior art.
A method according to the present disclosure is a method for defrosting an air source heat pump. The heat pump comprises a plurality of outdoor evaporators each comprising a number of fans and a number of coils each comprising fins and pipes.
The heat pump comprises a defrost system that applies a defrosting medium to provide thermal energy to defrost the coils.
In an embodiment, the method comprises:
The method comprises determining a maximum allowable pause time (Tpause, max) depending upon the at least one outdoor temperature (Tout 1, Tout 2, Tout 3).
By determining a maximum allowable pause time (Tpause, max) depending on the at least one outdoor temperature (Tout 1, Tout 2, Tout 3), it is possible to provide an adaptive method that automatically adapts to the at least one outdoor temperature (Tout 1, Tout 2, Tout 3).
The term “determine” in the expression: “determine a maximum allowable pause time (Tpause, max) depending on the at least one outdoor temperature (Tout 1, Tout 2, Tout 3)” may by way of example refer to:
In an embodiment, the maximum allowable pause time (Tpause, max) is in the range 10-300 min.
In an embodiment, the maximum allowable pause time (Tpause, max) is in the range 60-200 min.
In an embodiment, the maximum allowable pause time (Tpause, max) is in the range 100-150 min.
In an embodiment, the temperature is a surface temperature.
In an embodiment, the predefined temperature value is 0° C.
In an embodiment, the predefined temperature value is 0.5° C.
In an embodiment, the predefined temperature value is 0.9° C.
In an embodiment, the defrosting medium is water containing glycol.
In an embodiment, the defrosting medium is a high temperature refrigerant.
In an embodiment, the defrosting medium is a medium temperature refrigerant.
In an embodiment, the at least one temperature sensor is arranged to detect a temperature at a surface of at least one of the coils.
In an embodiment, the at least one temperature is an average temperature calculated on the basis of two or more temperatures detected by at least two temperature sensors.
The pause (Tpause) without defrosting is the elapsed time since the end of the last defrosting process for the evaporator in question.
In an embodiment, the method comprises:
Hereby, it is possible to apply the pressure difference (ΔP) across the evaporator to activate the defrost system.
In an embodiment, the method comprises:
In an embodiment, the method comprises:
In an embodiment, the method comprises:
In an embodiment, the method comprises:
In an embodiment, the method comprises:
In an embodiment, the method comprises:
In an embodiment, the method defrosts all evaporators sequentially one at a time.
In an embodiment, no break is provided in between sequential defrost processes.
In an embodiment, the method defrosts a fraction of the evaporators sequentially one at a time. Hereby, the remaining fraction of the evaporators can be operated.
In an embodiment, no break is provided in between the sequential defrost processes.
In an embodiment, a pause is provided between the defrost of the last evaporator and the next process (the subsequent defrost of the first evaporator).
In an embodiment, no pause is provided between the defrost of the last evaporator and the next process (the subsequent defrost of the first evaporator).
In an embodiment, the predefined pressure difference level (ΔPmax) corresponds to a 20-50% blockage ratio.
In an embodiment, the “blockage ratio” is defined as the ratio between the frost thickness and half of the fin spacing (the distance between adjacent fins).
In an embodiment, the predefined pressure difference level (ΔPmax) corresponds to 30-45% blockage ratio.
In an embodiment, the predefined pressure difference level (ΔPmax) corresponds to 40% blockage ratio.
In an embodiment, the defrosting medium is recirculated water-containing liquid.
In an embodiment, the defrosting medium comprises glycol.
In an embodiment, the defrosting medium is cooled refrigerant.
In an embodiment, the defrosting medium is heated refrigerant.
In an embodiment, the heat pump comprises an air inlet and an air outlet, wherein the method comprises detecting a temperature of the air inlet and a temperature of the air outlet, wherein:
This is done to keep the heat in the casing by running the fans upwards for a user defined period. When the time period has been exceeded, a new measurement of one of the sensors is needed to start the period.
In an embodiment, the method comprises:
In an embodiment, the maximum allowable pause time Tpause, max safety is set by the user, wherein the maximum allowable pause time Tpause, max safety overrules the determined Tpause, max.
In an embodiment, the Tpause max savety is in the range 15-600 min.
In an embodiment, the Tpause max savety is in the range 90-400 min.
In an embodiment, the Tpause max savety is in the range 200-600 min.
Tpause max savety may depend on the number of evaporators of the given system.
In an embodiment, the method comprises:
In an embodiment, the Tpause min safety is in the range 10-100 min.
In an embodiment, the Tpause min safety is in the range 10-75 min.
In an embodiment, the Tpause min safety is in the range 10-25 min.
Tpause min savety may depend on the number of evaporators of the given system.
A heat pump disclosed herein is an air source heat pump comprising a plurality of outdoor evaporators each comprising a number of fans and a number of coils. The heat pump comprises a defrost system that applies a defrosting medium to provide thermal energy to defrost the coils, wherein the heat pump comprises at least one temperature sensor arranged and configured to measure at least one temperature (T1, T2, T3) of at least one of the coils of at least one of the outdoor evaporators. The defrost system is configured to perform several defrost processes each having a duration (Tdefrost) separated by a pause (Tpause) without defrosting when the at least one temperature (T1, T2, T3) is below a predefined temperature value. The defrost system comprises:
Hereby, it is possible to provide a provide a heat pump that enables a higher performance, and which reduces or even eliminates the above mentioned disadvantages of the prior art.
The heat pump is an air source heat pump comprising a plurality of outdoor evaporators. Each outdoor evaporator comprises a number of coils.
The heat pump comprises a defrost system that applies a defrosting medium to provide thermal energy to defrost the coils.
The heat pump comprises at least one temperature sensor arranged and configured to measure at least one temperature (T1, T2, T3) of at least one of the coils of at least one of the outdoor evaporators.
In an embodiment, an average temperature is calculated on the basis of temperature measurements made by several temperature sensors.
The defrost system is configured to perform several defrost processes each having a duration (Tdefrost) separated by a pause (Tpause) without defrosting when the at least one temperature (T1, T2, T3) is below a predefined temperature value.
The defrost system comprises at least one temperature sensor arranged and configured to measure at least one ambient (outdoor) temperature (Tout 1, Tout 2, Tout 3).
The defrost system is configured to determine a maximum allowable pause time (Tpause, max) depending on the at least one ambient (outdoor) temperature (Tout 1, Tout 2, Tout 3).
The term “determine” may by way of example refer to:
By determining a maximum allowable pause time (Tpause, max) depending on the at least one outdoor temperature (Tout 1, Tout 2, Tout 3), it is possible to provide an adaptive defrost system that automatically adapts to the at least one outdoor temperature (Tout 1, Tout 2, Tout 3).
In an embodiment, the defrost system comprises:
Hereby, the defrost system can take into consideration the pressure difference (ΔP) across the evaporator.
In an embodiment, the defrost system comprises:
Hereby, the defrost system can take into consideration the relative humidity (H) of the ambient air.
In an embodiment, the air source heat pump is configured to ensure that the defrost system is only activated when the pause (Tpause) has exceeded the minimum allowable pause time (Tpause min safety).
Hereby, it is possible to ensure that pause (Tpause) is not less than the minimum allowable pause time (Tpause, min).
In an embodiment, the air source heat pump is configured to:
In an embodiment, the air source heat pump is configured to:
In an embodiment, the air source heat pump is configured to defrost a fraction of the evaporators at a time only.
In an embodiment, the air source heat pump is configured to defrost all evaporators sequentially one at a time. In an embodiment, no break is provided in between the sequential processes.
In an embodiment, the air source heat pump is configured to defrost a fraction of the evaporators sequentially one at a time.
In an embodiment, a pause is provided between the defrost of the last evaporator and the next process (the subsequent defrost of the first evaporator).
In an embodiment, no pause is provided between the defrost of the last evaporator and the next process (the subsequent defrost of the first evaporator).
In an embodiment, the predefined pressure difference level (ΔPmax) corresponds to 20-50% blockage ratio.
In an embodiment, the heat pump comprises an air inlet and an air outlet, wherein the heat pump is configured to detect a temperature of the air inlet and a temperature of the air outlet, wherein the heat pump is configured to ensure that:
In an embodiment, the least one temperature sensor is arranged and configured to measure at least one surface temperature of at least one of the coils of at least one of the outdoor evaporators.
In an embodiment, the predefined pressure difference level (ΔPmax) corresponds to 35-40% blockage ratio.
In an embodiment, the at least one temperature sensor is arranged to detect a temperature at a surface of at least one of the coils.
In an embodiment, the at least one temperature is an average temperature calculated on the basis of two or more temperatures detected by at least two temperature sensors.
The disclosed systems and methods will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of the systems or methods. In the accompanying drawings:
Referring now in detail to the drawings for the purpose of illustrating particular embodiments of the systems and methods.
Each of the outdoor coils 20, 20′, 20″, 20′″ comprises:
The refrigerant flows from the indoor unit 29 to the forward lines 50′ to the first coil 20 through a first refrigerant pipe 30, to the second coil 20′ through a second refrigerant pipe 30′, to the third coil 20″ through a third refrigerant pipe 30″ and to the fourth coil 20′″ through a fourth refrigerant pipe 30′″.
The refrigerant is returned to the indoor unit 29 from the coils 20, 20′, 20″, 20′″ through the return line 50.
The indoor unit 29 supplies a defrosting medium to the outdoor coils 20, 20′, 20″, 20′″ using a forward line 48 that is connected to the first coil 20 through a first defrosting pipe 31, to the second coil 20′ through a second defrosting pipe 31′, to the third coil 20″ through a third defrosting pipe 31″ and to the fourth coil 20′″ through a fourth defrosting pipe 31′″.
The defrosting medium is returned to the indoor unit 29 from the coils 20, 20′, 20″, 20′″ through the return line 48.
In an embodiment, the indoor unit 29 supplies hot water to a plate heat exchanger (not shown) via a supply water line 36. The indoor unit 29 receives water from the heat exchanger via a return water line 38.
A differential pressure sensor 14 is arranged and configured to detect the pressure difference ΔP across the first evaporator 6. Hereby, the differential pressure sensor 14 is configured to detect when the pressure difference ΔP across the first evaporator 6 is above a predefined pressure difference level ΔPmax.
A first temperature sensor 16 is arranged to detect an ambient (outdoor) temperature Tout 1. The ambient (outdoor) temperature Tout 1 is typically measured at the air-side inlet of the first evaporator 6. In an embodiment, additional outdoor temperatures are detected. In an embodiment, the ambient temperature Tout 1 is the temperature of the inlet (an inlet temperature). The temperature sensors applied for measuring the ambient (outdoor) temperature Tout 1 or other ambient temperatures are typically arranged outside the coils 20, 20′, 20″, 20′″.
In an embodiment, a first ambient (outdoor) temperature Tout 1 is measured at an air-side inlet of the first evaporator 6 using a first temperature sensor 16, wherein a second ambient (outdoor) temperature Tout 2 is measured at an air-side inlet of the first evaporator 6 using a second temperature sensor 16′.
In an embodiment, a first ambient (outdoor) temperature Tout 1 is measured outside the first evaporator 6 using a first temperature sensor 16, a second ambient (outdoor) temperature Tout 2 is measured outside the first evaporator 6 using a second temperature sensor 16′, and a third ambient (outdoor) temperature Tout 3 is measured outside one of the remaining evaporators (e.g. the second evaporator 6′) using a third temperature sensor 16″. In general, the ambient (outdoor) temperatures may be measured using temperature sensors arranged outside, typically at or in close proximity to an air-side inlet.
In an embodiment, an outlet temperature Toutlet is measured at the outlet of the first evaporator 6 using a temperature sensor 46.
In an embodiment, a temperature of the liquid in the return water line 38 is measured using a temperature sensor 32.
In an embodiment, a temperature of the fins of the first evaporator 6 is measured using a temperature sensor 12.
In an embodiment, heat pump 2 comprises a humidity sensor 40 arranged and configured for detecting the relative humidity of the ambient air. In an embodiment, the humidity sensor 40 is outside one of the coils 20, 20′, 20″, 20′″. In an embodiment, the humidity sensor 40 is at the air-side inlet of an evaporator. In general, the relative humidity of the ambient air may be measured using one or more humidity sensors arranged outside, typically at or in close proximity to an air-side inlet.
In an embodiment, heat pump 2 comprises a control unit 10 arranged and configured for carrying out a method disclosed herein. In an embodiment, the control unit 10 is arranged and configured for receiving data from the sensors of the heat pump 2. The data may be transmitted to the control unit 10 via wires or via wireless connections. In an embodiment, the control unit 10 is electrically connected to the indoor unit 29. The indoor unit 29 is connected to an energy source (e.g. the mains) which is not shown in
The heat pump 2 comprises an air inlet S3 and an air outlet S4.
In an embodiment, the heat pump 2 is configured to detect a temperature of the air inlet S3 and a temperature of the air outlet S4. The temperatures may be detected using temperature sensors.
In an embodiment, the heat pump 2 is configured to ensure that, when the difference between the temperature of the air inlet S3 and the temperature of the air outlet S4 during a defrost process exceeds a predefined level, operation of the fans is initiated and maintained for a predefined time period.
In the next step it is evaluated if the temperature of the fins TFin is below a predefined temperature level. In an embodiment, the predefined temperature level is 0° C.
If the temperature of the fins TFin is above the predefined temperature level (e.g. 0° C.), no defrosting is initiated.
If the temperature of the fins TFin is below the predefined temperature level (e.g. 0° C.), it is evaluated if:
If either of these two conditions a), b) is met, the defrosting is initiated and the defrosting is maintained for a time period Tdefrost.
In an embodiment, it is ensured that the time period Tdefrost exceeds a predefined minimum defrosting time period Tdefrost, min. When the time period Tdefrost exceeds the predefined minimum defrosting time period Tdefrost, min, the defrosting of the evaporator can be stopped as long as the fin temperature is above the predefined threshold. If Tdefrost exceeds Tdefrost max safety, the defrost process is stopped.
In an embodiment, the minimum defrosting time period Tdefrost, min is determined (e.g. calculated) on the basis of at least one detected air temperature and/or a return temperature of the defrosting media.
In an embodiment, the maximum allowable pause time Tpause, max is determined (e.g. calculated) on the basis of at least one detected air temperature and/or a relative humidity measurement of ambient air.
Even though it is not shown, the fin temperature is detected after “start defrosting”. Moreover, when the time exceeds the Tdefrost,min, the fin temperature will be checked and if the fin temperature is above a predefined threshold, or the Tdefrost exceeds Tdefrost max safety, the defrost process will be stopped.
At time to, defrost of evaporator 1 is initiated. At time t1 evaporator 1 has been defrosted.
At time t1, defrost of evaporator 2 is initiated. At time t2 evaporator 2 has been defrosted.
At time t2, defrost of evaporator 3 is initiated. At time t3 evaporator 3 has been defrosted.
At time t3, defrost of evaporator 4 is initiated. At time t4 evaporator 4 has been defrosted.
A pause is provided between time t4 and t5.
At time t5, defrost of evaporator 1 is initiated. At time t6 evaporator 1 has been defrosted.
At time t6, defrost of evaporator 2 is initiated. At time t7 evaporator 2 has been defrosted.
At time t7, defrost of evaporator 3 is initiated. At time t8 evaporator 3 has been defrosted.
At time t8, defrost of evaporator 4 is initiated. At time t9 evaporator 4 has been defrosted. A break is conducted from time t9 to t10.
The heat pump 2 comprises an indoor unit 29 arranged and configured to receive a refrigerant through a return line 52 that connects the outlet of the outdoor coil 20 to the indoor unit 29. The indoor unit 29 provides pressurized refrigerant to outdoor coil 20 via the forward line 54.
The indoor unit 29 is in fluid communication with the heat exchanger 120 via the forward line 56 and via the return line 58.
The heat pump 2 comprises a defrosting circuit that delivers a defrosting medium from the indoor unit 29 to the outdoor coil 20 through the forward defrosting line 62. The defrosting medium is returned to the indoor unit 29 via the return defrosting line 64. In an embodiment, the defrosting medium is refrigerant received by the compressor via the forward line 56.
In the next step it is evaluated if Tpause (the elapsed time since the end of the last defrosting process for evaporator in question) has exceeded a predefined level, Tpause min safety. If Tpause has not yet exceeded the predefined level Tpause min safety, a waiting step is conducted until Tpause exceeds the predefined level, so the following condition is met:
In the next steps it is evaluated if:
If either condition a) or condition b) is met, it is evaluated if the coil temperature exceeds a predefined threshold 1. If the coil temperature exceeds the predefined threshold 1, the defrost process is initiated. If not, the previous steps (after Start) are repeated.
If the pressure difference ΔP across the evaporator is not above the predefined pressure difference level ΔPmax and if Tpause (the elapsed time since the end of the last defrosting process for evaporator in question) has not exceeded a predefined maximum allowable level Tpause, max, it is evaluated if the pressure difference ΔP exceeds the predefined pressure difference level ΔPmax and if Tpause has exceeded the predefined maximum allowable level Tpause, max.
During the defrost process the defrost time Tdefrost is initially set to zero and the defrost process continues until the defrost time Tdefrost exceeds a predefined minimum required defrost time level, Tdefrost, min.
In the next step it is evaluated if:
If either of the conditions c) or d) are met, the defrost process (of evaporation 1) is stopped.
If the defrost time Tdefrost has not exceeded the predefined maximum allowable defrost time Tdefrost, max the defrost process continues.
Similarly, if the coil temperature has not yet exceeded the predefined threshold 2 the defrost process continues.
When the defrost process of evaporator 1 has ended the defrost process of evaporator 2 is initiated. This process continues until all evaporators have been defrosted.
In an embodiment, the threshold 1 is 0.5° C. or 0° C.
| Number | Date | Country | Kind |
|---|---|---|---|
| PA 2023 30106 | Jun 2023 | DK | national |
