CN110715482B - Defrosting method of air source heat pump unit - Google Patents
Defrosting method of air source heat pump unit Download PDFInfo
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- CN110715482B CN110715482B CN201910815634.5A CN201910815634A CN110715482B CN 110715482 B CN110715482 B CN 110715482B CN 201910815634 A CN201910815634 A CN 201910815634A CN 110715482 B CN110715482 B CN 110715482B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
- F25B47/02—Defrosting cycles
- F25B47/022—Defrosting cycles hot gas defrosting
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
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- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Defrosting Systems (AREA)
- Air Conditioning Control Device (AREA)
Abstract
The invention relates to the technical field of air source heat pumps, in particular to a defrosting method of an air source heat pump unit, which discloses a defrosting entry condition and comprehensively references an ambient temperature T air Vaporization temperature T e And ambient temperature T air The frost formation condition of the surface of the air side heat exchanger can be accurately judged by the calculation relation, the defrosting accumulated running time, the module water outlet temperature and other factors, so that the air side heat exchanger enters the defrosting process at an accurate time.
Description
Technical Field
The invention relates to the technical field of air source heat pumps, in particular to a defrosting method of an air source heat pump unit.
Background
The air source heat pump unit is used as an air conditioning device capable of supplying cold and heat, and the area is very wide, so that the facing climate environment is complicated and frosting is various. The frosting seriously affects the heat exchange efficiency of the air side heat exchanger, and the heat production amount and the energy efficiency ratio are attenuated, so that when the unit heats and operates, after the frost layer is accumulated to a certain degree, the defrosting operation is needed.
The multi-system air source heat pump unit is characterized in that 2 or more than 2 refrigerant circulation systems are arranged in one heat pump unit.
When the air flow channels of fans used in the air side heat exchangers of multiple systems are in communication with each other, such designs are known as "shared air" systems, such units typically defrost in a synchronized defrost mode (on refrigeration mode for defrost). Synchronous defrosting refers to that when any one system in the unit meets the defrosting entering condition, other systems of the unit enter defrosting operation at the same time. Because the defrosting process is to turn off the fans of the system, prevent the fans from radiating heat to the environment, and ensure that the heat of the defrosting operation system is transferred to the frost layer on the surface of the air side heat exchanger, thereby completing defrosting operation more quickly, when 1 system operates defrosting, the fans are turned off, so that other systems of the shared air unit cannot perform normal heating operation (need to operate the fans), and a synchronous defrosting mode is adopted.
When the common wind type unit is not in full load operation, the heating operation time length among different systems may be different, and the synchronous defrosting of the unit can lead to the 'false defrosting' action that one or more systems are not in full defrosting entering condition and defrost, because the defrosting time group is actually in an operation refrigeration mode, excessive heat loss and waste are caused, and the heating comprehensive energy efficiency ratio of the air conditioning system is reduced.
When the air flow channels of fans used in the air side heat exchangers of multiple systems are independent of each other, such designs are known as "independent air" systems, and such units typically defrost in an asynchronous defrost mode. Asynchronous defrosting refers to that when any one system in a unit meets defrosting entering conditions, the system enters defrosting operation, a fan of the system is closed, other systems of the unit still operate for heating, and the fan is not stopped.
When the independent wind type unit is in full-load operation, the heating operation time periods among different systems are the same or very similar, so that frosting conditions of the surfaces of air side heat exchangers of the systems are approximate, but at the moment, the control program still forces the systems to execute asynchronous defrosting, so that the unit can generate multiple defrosting actions in a short time range, namely 'excessive defrosting', thereby also causing excessive loss and waste of heat and reducing the heating comprehensive energy efficiency ratio of the air conditioning system.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a defrosting method of an air source heat pump unit, which is beneficial to saving heat and improving the comprehensive energy efficiency of the air source heat pump unit.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the defrosting method of the air source heat pump unit comprises at least two groups of refrigerant circulation systems and a control system connected with the refrigerant circulation systems, wherein each group of refrigerant circulation systems comprises an air side heat exchanger which is a fin heat exchanger; the control system judges that the refrigerant circulation system meets the following conditions, and allows the refrigerant circulation system to enter a defrosting process:
condition a, an ambient temperature T of an environment in which the refrigerant cycle system is located air The first preset environmental temperature T0 is less than or equal to air A first preset ambient temperature T0 of 5 ℃ or less air ≤15℃；
The defrosting accumulated running time of the refrigerant circulation system is more than or equal to a defrosting period T;
condition C, when the ambient temperature T air < second preset ambient temperature T1 air The second preset environmental temperature T1 is less than or equal to minus 10 DEG C air When the temperature is less than or equal to 0, the evaporating temperature T e Ambient temperature T < K1% air -C0 and duration t c0 ，t c0 More than 0s, C0 is more than 10 and less than 20, K1 is more than or equal to 0.5 and less than or equal to 0.9; alternatively, when the ambient temperature T air Not less than the second preset environmental temperature T1 air The second preset environmental temperature T1 is less than or equal to minus 10 DEG C air When the temperature is less than or equal to 0, the evaporating temperature T e Ambient temperature T < K2% air -C1 and duration t c1 ，t c1 ＞0s,9＜C1＜19,0.6≤K2≤1.2；
The quantity of the refrigerant circulation systems in the defrosting process is smaller than the quantity N of the allowable defrosting systems of the air source heat pump unit, N is more than 0 and less than or equal to the quantity of the refrigerant circulation systems in the air source heat pump unit, and N is an integer;
condition E, module outlet water temperature T WO The water outlet temperature T0 of the preset module is not less than WO The water outlet temperature T0 of the preset module is less than or equal to 5 DEG C WO The temperature is less than or equal to 15 ℃, and the module is an air source heat pump unit.
Preferably, in condition a, the first preset ambient temperature T0 air 10 ℃; in the condition B, the defrosting period T is 30min; in condition C, the second preset ambient temperature T1 air At-4 ℃, t c0 ＝120s，t c1 =120 s, k1=0.7, c0=13, c1=12, k2=0.8; in the condition D, the number N of the allowable defrosting systems is half of the number of the refrigerant circulation systems in the air source heat pump unit; in condition E, the module water outlet temperature T0 is preset WO Is 10 ℃.
Preferably, the control system determines that the refrigerant circulation system in the defrosting process meets any one of the following conditions, and controls the refrigerant circulation system to exit the defrosting process:
condition a, fin temperature T of air-side heat exchanger of refrigerant cycle system f Not less than a preset defrosting exit fin temperature T f0 The temperature T of a defrosting exit fin is preset at 20 ℃ or less f0 ≤45℃；
Condition b, defrosting operation time T of the refrigerant cycle system C Not less than the maximum time T in defrosting process CMAX The maximum time T of defrosting process is less than or equal to 3min CMAX ≤10min；
A condition c that the refrigerant cycle system high-voltage switch is turned off;
condition d, module water outlet temperature T WO The defrosting exit water outlet temperature T is less than or equal to WO0 Defrosting exit water outlet temperature T of 5 ℃ or less W0 The temperature is less than or equal to 25 ℃, and the module is an air source heat pump unit.
Preferably, the preset defrosting exit fin temperature T f0 30 ℃; the maximum time T of the defrosting process CMAX For 5min; in the condition c, after the high-voltage switch of the refrigerant circulation system is disconnected, the compressor of the refrigerant circulation system is immediately stopped and exits the defrosting process; the defrosting exits the water outlet temperature T W0 Is 10 ℃.
Preferably, the control system may correct a next defrosting cycle of the refrigerant cycle system according to a condition that the refrigerant cycle system exits the current defrosting process.
Preferably, if the refrigerant cycle system in the defrosting process is degraded by the satisfaction of the condition aWhen defrosting is performed, the control system corrects the next defrosting period increasing time T of the refrigerant circulation system p1 ，5min≤T p1 Less than or equal to 20min; if the refrigerant cycle system in the defrosting process exits the defrosting process due to the satisfaction of the condition b, the control system corrects the next defrosting cycle reduction time T of the refrigerant cycle system p2 ，5min≤T p2 Less than or equal to 20min; the next defrost cycle of the refrigerant cycle that is modified must be greater than or equal to the minimum allowable defrost cycle T CMIN 0 < minimum value T of allowable defrosting period CMIN ≤60min。
According to the defrosting method of the air source heat pump unit, the defrosting entering conditions can accurately judge the frosting condition of the surface of the air side heat exchanger, so that the air side heat exchanger enters the defrosting process at an accurate time, the heat is saved, and the comprehensive energy efficiency of the air source heat pump unit is improved. In addition, the defrosting exit condition ensures that the operation of the air source heat pump unit is more reasonable and scientific, and is beneficial to improving the comprehensive efficiency of the air source heat pump unit.
Drawings
FIG. 1 is a schematic view of an air source heat pump unit according to the present invention, wherein each compressor is connected to one air side heat exchanger, and the different air side heat exchangers share a blower and the ventilation channels are in communication;
FIG. 2 is a schematic diagram of another configuration of the air source heat pump unit of the present invention, wherein each compressor is connected to two air side heat exchangers, different air side heat exchangers sharing a blower and the ventilation channels communicating;
FIG. 3 is a schematic structural view of the air source heat pump unit of the present invention, which is in a defrosting process, as in the air source heat pump unit of FIG. 1;
FIG. 4 is a schematic structural view of the air source heat pump unit of the present invention, which is in a defrosting process, as in the air source heat pump unit of FIG. 2;
FIG. 5 is a schematic view of a third configuration of the air source heat pump unit of the present invention, wherein different fans are used for different air side heat exchangers, and ventilation channels of different air side heat exchangers are isolated from each other;
FIG. 6 is an air source heat pump unit of the present invention, similar to the air source heat pump unit of FIG. 5, in an asynchronous defrost operation;
FIG. 7 is a schematic illustration of one embodiment of a defrost method for an air source heat pump unit of the present invention, each air side heat exchanger sharing a fan and having ventilation channels in communication;
FIG. 8 is a schematic illustration of one embodiment of a defrost method for an air source heat pump unit of the present invention, each air side heat exchanger using a different blower and each ventilation channel being isolated from each other;
FIG. 9 is an embodiment of a defrosting method of the air source heat pump unit of the present invention, which is a modified embodiment of the defrosting method shown in FIG. 7;
FIG. 10 is an embodiment of a defrosting method of an air source heat pump unit according to the present invention, which is a modified embodiment of the defrosting method shown in FIG. 8;
FIG. 11 is a graph of a simulated process employing synchronous defrost during part load operation of an air source heat pump unit having a dual refrigerant cycle system in accordance with the present invention;
FIG. 12 is a graph of a simulated process employing asynchronous defrost when the air source heat pump unit of the present invention is operating with a dual refrigerant cycle, shared air, partial load;
FIG. 13 is a graph of a simulated process employing asynchronous defrost when the air source heat pump unit of the present invention is operating with a dual refrigerant cycle, independent wind, partial load;
fig. 14 is a graph of a simulated process of synchronous defrosting for full load operation of an air source heat pump unit having a dual refrigerant cycle system, independent wind or common wind in accordance with the present invention.
Detailed Description
Specific embodiments of the defrosting method of the air source heat pump unit of the present invention are further described below with reference to the examples shown in fig. 1 to 14. The defrosting method of the air source heat pump unit of the present invention is not limited to the description of the following embodiments.
The invention relates to a defrosting method of an air source heat pump unit, which comprises at least two sets of refrigerant circulating systems, wherein each set of refrigerant circulating system comprises an air side heat exchanger, and the air side heat exchanger is a fin heat exchanger; the defrosting method comprises the following steps:
step one, determining a refrigerant circulation system meeting defrosting entering conditions;
step two, calculating a defrosting accumulated operation time difference t between the defrosting accumulated operation time of a certain set of refrigerant circulation system which does not meet the defrosting entering condition and the defrosting accumulated time of the refrigerant circulation system which meets the defrosting entering condition D ；
Step three, comparing the defrosting accumulated running time difference t D And a first preset time t 0 Wherein t is 0 ＞0：
If defrosting accumulated operation time difference t D The first preset time t is less than or equal to 0 The set of refrigerant circulation systems which do not meet the defrosting entering conditions and the set of refrigerant circulation systems which meet the defrosting entering conditions enter the defrosting process;
if defrosting accumulated operation time difference t D > first preset time t 0 The refrigerant circulation system meeting the defrosting entering condition enters the defrosting process, and the set of refrigerant circulation system which does not meet the defrosting entering condition stops waiting or continues to work normally;
and step four, repeating the step two and the step three, and judging whether all the refrigerant systems which do not meet the defrosting entering condition can enter the defrosting process.
The defrosting method of the air source heat pump unit of the invention is based on the defrosting accumulated running time difference t D And a first preset time t 0 If the defrosting accumulated operation time difference t is D > first preset time t 0 The fact that the heating operation time of the set of refrigerant circulation systems which do not meet the defrosting entering conditions is greatly different from that of the set of refrigerant circulation systems which do not meet the defrosting entering conditions is described, and the set of refrigerant circulation systems which do not meet the defrosting entering conditions do not enter the defrosting process at this time, but stop for waiting or normally working, so that false defrosting of the refrigerant circulation systems (systems with shorter heating operation time) is avoided, waste and loss of heat are avoided, and comprehensive energy efficiency of the air source heat pump unit is improved; if defrosting is running cumulativelyDifference t between D The first preset time t is less than or equal to 0 The set of refrigerant circulation systems which do not meet the defrosting entering conditions are explained to be close to the refrigerant circulation systems which meet the defrosting entering conditions in heating operation time, the frosting condition of the surface of the air side heat exchanger is close, the set of refrigerant circulation systems which do not meet the defrosting entering conditions also enter the defrosting process jointly, the times of entering the defrosting process of the air source heat pump unit can be effectively reduced, heat waste and loss caused by repeated and continuous defrosting processes are avoided, and the comprehensive energy efficiency of the air source heat pump unit is improved.
Preferably, the air source heat pump unit comprises M 0 Refrigerant circulation system, M 0 Is an integer greater than 2; if the air source heat pump unit has M in the same time 1 The refrigerant circulation system meets the defrosting entering condition, M 1 If the total number of the refrigerant circulation systems is more than or equal to 2 and less than the total number of the refrigerant circulation systems, in the second step, calculating a defrosting accumulated operation time difference t between a certain set of refrigerant circulation systems which do not meet the defrosting inlet conditions and the refrigerant circulation system which meets the defrosting inlet conditions and has the shortest defrosting accumulated operation time D . For example, the air source heat pump unit includes 6 sets (i.e., M 0 =6) refrigerant circulation systems, a system, B system, C system, D system, E system, and F system, respectively; at a certain moment, the A system, the B system and the C system simultaneously meet the defrosting entering condition (namely M 1 3), if the relation between the defrosting accumulated operation time of the three is that the A system is less than the B system and less than the C system, respectively calculating the defrosting accumulated operation time difference t between the defrosting accumulated operation time of the D system, the E system and the F system and the defrosting accumulated operation time of the A system D 。
For example, as shown in fig. 11, the air source heat pump unit includes two refrigerant circulation systems, namely a system No. 1 and a system No. 2, where the system No. 1 runs for a long period, and the system No. 2 is in an operation and a stop state alternately, so that the output capacity of the whole air source heat pump unit is controlled to be 50-100%, the air source heat pump unit is in a partial load operation state, when the system No. 1 needs to be defrosted, the system No. 2 runs for a short period of time, and does not need to be defrosted, and when the system No. 1 and the system No. 2 are defrosted, the system No. 2 operates as "false defrosting", which causes heat loss of the air source heat pump unit, and the heating comprehensive energy efficiency ratio is reduced.
As shown in fig. 12, the air source heat pump unit includes two refrigerant circulation systems, namely a system No. 1 and a system No. 2, which belong to the type of "shared wind", and by adopting the defrosting method of the air source heat pump unit of the present invention, when the system No. 1 is defrosted, the system No. 2 is stopped and waiting, and when the system No. 2 is defrosted, the system No. 1 is stopped and waiting, so that the "false defrosting" operation of the refrigerant circulation system which does not satisfy the defrosting entry condition is avoided. As shown in fig. 13, the air source heat pump unit includes two refrigerant circulation systems, namely a system No. 1 and a system No. 2, which belong to the type of "independent wind", and when the system No. 1 is defrosted, the system No. 2 works normally, and when the system No. 2 is defrosted, the system No. 1 works normally. With reference to fig. 12 and 13, when the two types of air source heat pump units are in a partial load operation state, the defrosting method of the air source heat pump unit provided by the invention realizes asynchronous defrosting of the No. 1 system and the No. 2 system, and can reduce the defrosting times of the unit within a certain time range, thereby improving the heating comprehensive energy efficiency ratio of the unit.
As shown in FIG. 14, the air source heat pump unit comprises two refrigerant circulation systems, namely a No. 1 system and a No. 2 system, wherein the No. 1 system and the No. 2 system respectively run for a long time, the whole air source heat pump unit is in a full-load running state, frost layers on the surfaces of air side heat exchangers of the two systems are relatively close, the defrosting accumulated running time of the two systems is relatively similar, and the air source heat pump unit adopts the defrosting method of the air source heat pump unit, so that the two systems are synchronously defrosted, the alternate defrosting of the No. 1 system and the No. 2 system in a short time is avoided, the heat loss caused by defrosting is reduced to a certain extent, and the heating comprehensive energy efficiency ratio is also improved.
Preferably, the first preset time t is less than or equal to 5min 0 Less than or equal to 30min. Further, the first preset time t 0 For 10min. Of course, according to the actual situationA first preset time t 0 Can be adjusted, for example, for a first predetermined time t 0 May be any time between 0 and 30 minutes.
Preferably, in step three, if defrosting accumulates the running time difference t D The first preset time t is less than or equal to 0 Then the current evaporating temperature T of the set of refrigerant circulation system which does not meet the defrosting entering condition is calculated e And the current evaporating temperature T e The set of refrigerant circulation systems that do not satisfy the defrost entry condition enter the defrost process if the following conditions are satisfied: when the defrosting entry condition is not satisfied, the ambient temperature T of the environment in which the air-side heat exchanger of the refrigerant cycle system is located air When less than the second preset temperature T1 and T e ＜(K1*T air A1) +B1, or when the ambient temperature T air When the temperature is more than or equal to the second preset temperature T1 and T e ＜(K2*T air -A2) +b2; wherein, T1 is more than minus 8 ℃ and less than 0 ℃, K1 is more than or equal to 0.5 and less than or equal to 0.9, A1 is more than 10 and less than 20, B1 is more than 0 and less than or equal to 2,0.6, K2 is more than or equal to 1.2,11, A2 is more than 19,0 and less than B2; the current evaporating temperature T of the set of refrigerant circulation systems if the defrost inlet condition is not satisfied e When the above conditions are not satisfied, the refrigerant circulation system satisfying the defrosting entry conditions is in the defrosting process, and the set of refrigerant circulation system not satisfying the defrosting entry conditions is normally operated or stopped for waiting. Further, the second preset temperature T1 is-4 ℃, k1=0.7, a1=13, b1=1, k2=0.8, a2=12, and b2=1.
As shown in fig. 7, a first embodiment of the defrosting method of the air source heat pump unit of the present invention is shown.
The air source heat pump unit comprises at least two refrigerant circulation systems and a control system connected with the refrigerant circulation systems, and is of a common wind type (namely, as shown in figures 1-4, the air side heat exchangers of the refrigerant circulation systems use the same group of fans, and the air circulation channels of the fans are mutually communicated); each refrigerant circulation system comprises an air side heat exchanger, wherein the air side heat exchangers are fin heat exchangers; the defrosting method comprises the following steps:
step one, determining a refrigerant circulation system meeting defrosting entering conditions;
for the same air source heat pump unit, only one set of refrigerant circulation system meets the defrosting entering condition at the same time.
Step two, the control system calculates a defrosting accumulated operation time operation difference t between the defrosting accumulated operation time of the refrigerant circulation system meeting the defrosting entering condition and the defrosting accumulated operation time of a certain set of refrigerant circulation system not meeting the defrosting entering condition D 。
Step three, comparing the defrosting accumulated running time difference t D And a first preset time t 0 Wherein the first preset time t 0 ＞0：
If defrosting accumulated operation time difference t D The first preset time t is less than or equal to 0 The set of refrigerant circulation systems which do not meet the defrosting entry conditions and the set of refrigerant circulation systems which meet the defrosting entry conditions enter the defrosting process;
if defrosting accumulated operation time difference t D > first preset time t 0 And the refrigerant circulation system meeting the defrosting entering condition enters the defrosting process, and the set of refrigerant circulation system which does not meet the defrosting entering condition stops and waits.
And step four, repeating the step two and the step three to respectively judge whether each set of refrigerant circulation system which does not meet the defrosting entering condition can enter the defrosting process.
Preferably, the first preset time t 0 For 10min.
Preferably, a method for calculating the defrosting accumulated operation time is as follows:
starting timing conditions: after the refrigerant circulation system is heated and started for the first time, or after the defrosting process is finished and the heating and starting are recovered, the refrigerant circulation system is heated and started from the evaporating temperature T e Time of < third preset temperature T2 (i.e. evaporation temperature T e The time when the temperature is reduced to be below a third preset temperature T2), starting timing, wherein-7 ℃ is less than the third preset temperature T2 which is less than 3 ℃; if during the time, the evaporating temperature T e More than or equal to a third preset temperature T2 and a duration time of more than T1, wherein T1 is more than or equal to 30s, the timing is cleared, and the temperature is at the evaporating temperature T e < third preset temperature T2, restarting timing; if the refrigerant circulation system is stopped in the timing process, the timing is stopped and not cleared, and after the refrigerant circulation system is started again and the running time is greater than or equal to time T3, T3 is more than 0, if the evaporating temperature T e More than or equal to a third preset temperature T2 and more than a duration time T1, resetting the timing, and at the evaporating temperature T e Restarting timing at a time less than the third preset temperature T2; if the refrigerant circulation system is stopped in the timing process, the timing is stopped and not cleared, and after the refrigerant circulation system is started again and the running time is more than or equal to time T3, T3 is more than 0, if the evaporating temperature T e The third preset temperature T2 is less than the third preset temperature T2, the time is accumulated, and only the evaporation temperature T is accumulated e Time < the third preset temperature T2. Further, the third preset temperature T2 is-2 ℃, the time T1 is 60s, and the time T3 is 2min.
Preferably, a first preset time t 0 The determining method comprises the following steps:
step one, a first preset time t is first set 0 Setting a larger value and then spacing the compressors of the two refrigerant circulation systems for a first preset time t 0 Starting operation (one of the refrigerant circulation systems is operated first), when the refrigerant circulation system operated first meets defrosting entering conditions, observing frosting conditions of air heat exchangers of the two refrigerant circulation systems, and if frosting of an air side heat exchanger of the refrigerant circulation system operated later is little at the moment and defrosting is not needed, setting a first preset time t 0 Repeating the above experiment until a first preset time t is obtained 0 Is a rough range value of (a);
step two, a first preset time t is set first 0 Letting two refrigerant circulation systems (system a and system B) be spaced apart for a first preset time t 0 Starting, wherein the system A is started firstly, and then the evaporating temperature T of the system A is recorded after the two refrigerant circulation systems run stably under the working condition A0 Vaporization temperature T of System B B0 After the system A enters the defrosting process, the evaporating temperature T before the system A enters the defrosting process is recorded A1 Vaporization temperature T of system B at corresponding time B1 Calculate the evaporation temperature decay value DeltaT of System A A ＝T A1 -T A0 Evaporation temperature decay value deltat for system B B ＝T B1 -T B0 Comparing the two attenuation values, and properly shortening the preset time t when the difference is larger 0 Through repeated test, a first preset time t is obtained 0 Is a rough range value of (a);
step three, the first preset time t obtained in the step one and the step one respectively is obtained 0 Fitting the approximate range values of (2) to finally determine a first preset time t 0 Is a value of (a).
Preferably, the first defrost access condition (being an existing defrost access condition) is:
condition a, ambient temperature T of the environment in which the air heat exchanger of the refrigerant cycle is located air The first preset environmental temperature T0 is less than or equal to air A first preset ambient temperature T0 of 5 ℃ or less air Less than or equal to 15 ℃, a first preset environmental temperature T0 air Preferably 10 ℃; the defrosting accumulated running time of the refrigerant circulation system is more than or equal to a defrosting period T, and the defrosting period T is preferably 30min; condition C, ambient temperature T air Fin temperature T of heat exchanger with air f The difference of (2) is smaller than the fourth preset temperature T 3 Fourth preset temperature T 3 > 0; the quantity of refrigerant circulation systems in the defrosting process is smaller than the quantity N of the allowable defrosting systems of the air source heat pump unit, N is more than 0 and less than or equal to the quantity N of the refrigerant circulation systems of the air source heat pump unit, N is an integer, and the quantity N of the allowable defrosting systems is preferably half of the quantity of the refrigerant circulation systems of the air source heat pump unit; condition E, module outlet water temperature T WO The water outlet temperature TO of the preset module is not less than WO The water outlet temperature T0 of the preset module is less than or equal to 5 DEG C WO The temperature of the module water outlet T0 is preset and is less than or equal to 15 DEG C WO Preferably at 10 ℃, and the module is an air source heat pump unit. When any refrigerant circulation system in the air source heat pump unit meets the defrosting entering condition (namely, meets the condition A-condition E at the same time), the refrigerant circulation system can enter the defrosting process.
Preferably, the second defrost access condition (defrost access condition preferred for the present invention) is:
condition a, ambient temperature T of the environment in which the air heat exchanger of the refrigerant cycle is located air The first preset environmental temperature T0 is less than or equal to air A first preset ambient temperature T0 of 5 ℃ or less air Less than or equal to 15 ℃, a first preset environmental temperature T0 air Preferably 10 ℃;
the defrosting accumulated running time of the refrigerant circulation system is more than or equal to a defrosting period T, and the defrosting period T is preferably 30min;
condition C, when the ambient temperature T air < second preset ambient temperature T1 air -10 ℃ below zero < a second preset ambient temperature T1 air < 0, a second preset ambient temperature T1 air Preferably-4 ℃, evaporation temperature T e Ambient temperature T < K1% air -C0, and duration t c0 Wherein K1 is 0.5-0.9, K1 is preferably 0.7, 10 < C0 < 20, C0 is preferably 13, t c0 ＞0s，t c0 Preferably 120s; or when the ambient temperature T air Not less than the second preset environmental temperature T1 air The second preset environmental temperature T1 is less than or equal to minus 10 DEG C air Less than or equal to 0 ℃, a second preset environmental temperature T1 air Preferably-4 ℃, evaporation temperature T e Ambient temperature T < K2% air -C1, and duration t c1 ，t c1 ＞0s，t c1 Preferably 120s, wherein 0.6.ltoreq.K2.ltoreq.1.2, K2 preferably being 0.8,9 < C1 < 19, C1 preferably being 12;
the quantity of refrigerant circulation systems in the defrosting process is smaller than the quantity N of the allowable defrosting systems of the air source heat pump unit, N is more than 0 and less than or equal to the quantity N of the refrigerant circulation systems of the air source heat pump unit, N is an integer, and the quantity N of the allowable defrosting systems is preferably half of the quantity of the refrigerant circulation systems of the air source heat pump unit;
condition E, module outlet water temperature T WO The water outlet temperature T0 of the preset module is not less than WO The water outlet temperature T0 of the preset module is less than or equal to 5 DEG C wO The temperature of the module water outlet T0 is preset and is less than or equal to 15 DEG C WO Preferably at 10 ℃, and the module is an air source heat pump unit. Any refrigerant circulation system in the air source heat pump unit meets the defrosting entering conditionWhen (i.e., when both conditions a-E are satisfied), the refrigerant cycle can enter a defrost process.
The first defrosting entry condition is the existing defrosting entry condition, the second defrosting entry condition is the defrosting entry condition which is preferentially adopted by the defrosting method, and compared with the first defrosting entry condition, the time for entering the defrosting process of the refrigerant circulation system can be more accurate, and the specific reasons are as follows:
when the air-side heat exchanger operates as an evaporator, the temperature of the refrigerant inside the heat exchange tube is referred to as an evaporation temperature, the temperature of the air outside the heat exchange tube is referred to as an ambient temperature, and the difference between the two is primarily considered as a heat transfer temperature difference (i.e., ambient temperature-evaporation temperature), which is related to the design of the heat exchanger and the ambient temperature when the heat exchanger operates, that is, even when the design of one heat exchanger has been determined, the heat transfer temperature difference changes with the change of the ambient temperature, for example:
the ambient temperature is 7 ℃, the evaporation temperature is-4 ℃, and the heat transfer temperature difference is 11 ℃;
the ambient temperature is-12 ℃, the evaporation temperature is-19 ℃, and the heat transfer temperature difference is 7 ℃;
thus, there is a computational relationship between the evaporation temperature and the ambient temperature, rather than a constant difference. The general law is: the lower the ambient temperature, the lower the heat transfer temperature difference of the air side heat exchanger.
Of course, even if the ambient temperature is the same, the heat transfer temperature difference may be different, mainly because of the influence of frosting on the surface of the air side heat exchanger, which may result in poor performance of the heat exchanger and reduced evaporation temperature, so that the heat transfer temperature difference becomes large, for example, after frosting on the surface of the air side heat exchanger to a certain extent:
the ambient temperature is 7 ℃, the evaporation temperature is-6 ℃, and the heat transfer temperature difference is 13 ℃;
the ambient temperature is-12 ℃, the evaporation temperature is-21 ℃, and the heat transfer temperature difference is 9 ℃;
thus, there is also a relationship between the evaporating temperature and the ambient temperature after frosting of the heat exchanger, rather than a constant difference.
Therefore, when the ambient temperature of the environment where the air side heat exchanger is located is fixed, if the heat transfer temperature difference gradually becomes larger, the situation that the surface of the heat exchanger is frosted gradually is indicated, that is, the quantity and the thickness of the frosted surface of the heat exchanger can be judged by the size of the heat transfer temperature difference.
The first defrost entry condition produces errors (errors, meaning that when defrosting is performed according to the logic of the first defrost entry condition, the actual frosting of the heat exchanger surface may be "no need to defrost" or "frosted very serious, need to defrost some time earlier") for the following main reasons:
substituting fin temperature for evaporation temperature: the fin temperature is measured as the refrigerant temperature at the inlet end of the heat exchanger and is not the actual evaporating temperature;
when the frosting degree is consistent, if the ambient temperature is different, the heat transfer temperature difference is also different, and in the condition C of the first defrosting entering condition, the ambient temperature T air Fin temperature T of heat exchanger with air f The difference of (2) is smaller than the fourth preset temperature T 3 Fourth preset temperature T 3 > 0 and is a fixed value that does not change with changes in ambient temperature.
The second defrosting entry condition (i.e., the condition preferentially adopted by the defrosting method of the present invention) improves the accuracy of defrosting (i.e., when defrosting is performed according to the logic of the second defrosting entry condition, the actual frosting situation of the surface of the heat exchanger is all near the "defrosting needed" state), specifically for the following reasons:
a curve formula of evaporation temperature and ambient temperature obtained by: vaporization temperature T e Ambient temperature T =k = air C, the curve formula is more scientific and accurate;
step one, the air source heat pump unit heats up until the surface of the air side heat exchanger is frosted and gradually thickened, until the thickness of the frost layer reaches the thickness of defrosting (whether defrosting is needed or not, the thickness and the area ratio of the frost layer can be directly observed by naked eyes, and the heating quantity, the attenuation percentage of the heating efficiency and the like of the air source heat pump unit tested in a laboratory are determined), and the evaporation temperature (namely the evaporation temperature at the moment before defrosting) of the air source heat pump unit is recorded at the moment;
and step two, performing the operation of the step one under a plurality of different environment temperatures to finally obtain the curve formula.
In condition C of the second defrost inlet condition, the evaporating temperature T is introduced e Ambient temperature T air C, i.e. greatly improving the accuracy of the defrosting of the second defrost entry condition.
Specifically, as shown in fig. 1-4, the air source heat pump unit includes 2 sets of refrigerant circulation systems, one set of refrigerant circulation system includes a No. 1 compressor, the refrigerant circulation system is a first system, the other set of refrigerant circulation system includes a No. 2 compressor, the refrigerant circulation system is a second system, an air side heat exchanger connected with the No. 1 compressor and an air side heat exchanger connected with the No. 2 compressor share a fan, and an air circulation channel of the fan is communicated. As shown in fig. 1-4 and fig. 7, when the first system meets the defrosting entry condition, determining a defrosting accumulated operation time difference t between the first system and the second system D And a first preset time t 0 If defrosting accumulated operation time difference t D The first preset time t is less than or equal to 0 The fan is closed, the first system and the second system enter the defrosting process at the same time, and if the defrosting accumulated running time difference t is D > first preset time t 0 And the fan is closed, the first system enters the defrosting process, the second system is stopped for waiting, and after the first system finishes the defrosting process, the first system and the second system are automatically started. Further, the first system meets the defrosting entering condition, the second system does not meet the defrosting entering condition, and the defrosting accumulated running time difference t of the first system and the second system D The first preset time t is less than or equal to 0 Then calculate the current evaporating temperature T of the second system e If the front evaporating temperature T of the second system e If the following conditions are met, the fan is turned off, and the whole air source heat pump unit (namely the first system and the second system) enters a defrosting process: when the defrosting entry condition is not satisfied, the ambient temperature T of the environment in which the air-side heat exchanger of the refrigerant cycle system is located air T at-4 DEG C e ＜(K1*T air -A1)+B1，Or when the ambient temperature T air T is not less than-4 DEG C e ＜(K2*T air A2) +b2, wherein k1=0.7, a1=13, b1=1, k2=0.8, a2=12, b2=1. If the current evaporating temperature T of the second system e If the conditions are not met, the fan is turned off, only the first system enters the defrosting process, the second system is stopped for waiting, and after the first system finishes the defrosting process, the first system and the second system are automatically started.
Preferably, as shown in FIG. 9, in step three, if defrosting accumulates the operation time t D The first preset time t is less than or equal to 0 Then calculate the evaporating temperature difference delta T of the set of refrigerant circulation system which does not meet the defrosting entering condition e Evaporation temperature difference deltat e Is the current evaporating temperature T of the refrigerant circulation system e If the difference between the temperature and the evaporation temperature required by the refrigerant circulation system to enter the defrosting process is delta T e The first preset temperature T is less than or equal to 0 A first preset temperature T 0 If more than 0, the whole air source heat pump unit enters a defrosting process; if the evaporation temperature is different from delta T e > first preset temperature T 0 Only the refrigerant circulation system satisfying the defrost entry condition enters the defrost process.
Specifically, as shown in fig. 1-4 in combination with fig. 9, the first system satisfies the defrost entry condition, the second system does not satisfy the defrost entry condition, and the defrost cumulative operation time t of the first system and the second system is less than or equal to the first preset time t 0 Then calculate the evaporation temperature difference delta T of the second system e If the evaporation temperature is different from DeltaT e The first preset temperature T is less than or equal to 0 The fan is turned off, the whole air source heat pump unit (the first system and the second system) enters a defrosting process, and if the evaporation temperature difference delta T is the same e > first preset temperature T 0 And closing the fan, stopping the first system, stopping the second system, waiting until the first system finishes the defrosting process, and then automatically starting the first system and the second system.
As shown in fig. 8, a second embodiment of the defrosting method of the air source heat pump unit of the present invention is shown.
The present embodiment differs from the first embodiment in that: in this embodiment, the air-source heat pump unit includes at least two refrigerant circulation systems, and the ventilation systems of the respective refrigerant circulation systems are independent of each other (i.e., as shown in fig. 5 and 6, fans used for the air-side heat exchangers of the respective refrigerant circulation systems are different, and the air circulation channels of the respective fans are independent of each other). The defrosting method of the air source heat pump unit of the present embodiment is different from the first embodiment in that: if the whole air source heat pump unit (namely, all the refrigerant circulating systems) enters a defrosting process, all fans are closed, and all the refrigerant circulating systems enter the defrosting process; if only part of the refrigerant circulation system in the air source heat pump unit enters the defrosting process, the fan of the part of the refrigerant circulation system is closed and enters the defrosting process, and the other part of the refrigerant circulation system normally works (namely, maintains the heating mode).
Specifically, as shown in fig. 5, 6, 8 and 10, the air source heat pump unit includes two sets of refrigerant circulation systems, namely a first system and a second system, wherein the first system includes a No. 1 fan and a No. 1 compressor, the second system includes a No. 2 fan and a No. 2 compressor, when both the first system and the second system enter a defrosting process, both the No. 1 fan and the No. 2 fan are closed, and both the No. 1 compressor and the No. 2 compressor enter a refrigerating mode; if only the second system enters the defrosting process, the No. 1 fan is started, the No. 1 compressor keeps a heating mode, the No. 2 fan is closed, and the No. 2 compressor enters a refrigerating mode.
The invention discloses a defrosting method of an air source heat pump unit, and also discloses a condition that a refrigerant circulation system exits a defrosting process.
The air source heat pump unit comprises at least two groups of refrigerant circulation systems and a control system connected with the refrigerant circulation systems, and the control system judges that the refrigerant circulation systems in the defrosting process meet any one of the following conditions, and then the refrigerant circulation systems are controlled to exit the defrosting process: condition a, fin temperature T of air-side heat exchanger of refrigerant cycle system f Not less than a preset defrosting exit fin temperature T f0 The temperature T of a defrosting exit fin is preset at 20 ℃ or less f0 The temperature is less than or equal to 45 ℃; condition b, defrosting operation time T of the refrigerant cycle system C Not less thanMaximum time T of frost process CMAX The maximum time T of defrosting process is less than or equal to 3min CMAX Less than or equal to 10min; a condition c that the refrigerant cycle system high-voltage switch is turned off; condition d, module water outlet temperature T W0 The defrosting exit water outlet temperature T is less than or equal to WO0 Defrosting exit water outlet temperature T of 5 ℃ or less W0 The temperature is less than or equal to 25 ℃. Further, the preset defrosting exit fin temperature T f0 30 ℃; the maximum time T of the defrosting process CMAX For 5min; in the condition c, after the high-voltage switch of the refrigerant circulation system is disconnected, the compressor of the refrigerant circulation system is immediately stopped and exits the defrosting process; the defrosting exits the water outlet temperature T W0 Is 10 ℃.
Preferably, the control system may correct a next defrosting cycle of the refrigerant circulation system according to a condition that the refrigerant circulation system ends the defrosting process: if the refrigerant cycle system in the defrosting process exits the defrosting process because the condition a is satisfied, the control system corrects the next defrosting cycle increase time T of the refrigerant cycle system p1 ，5min≤T p1 Less than or equal to 20min; if the refrigerant cycle system in the defrosting process exits the defrosting process due to the satisfaction of the condition b, the control system corrects the next defrosting cycle reduction time T of the refrigerant cycle system p2 ，5min≤T p2 Less than or equal to 20min; the next defrost cycle of the refrigerant cycle that is modified must be greater than or equal to the minimum allowable defrost cycle T CMIN 0 < minimum value T of allowable defrosting period CMIN Less than or equal to 60 minutes. Further, the minimum value T of the allowable defrosting period CMIN 30min. Specifically, if the refrigerant circulation system exits the defrosting process because of meeting the condition a, it is indicated that the defrosting of the air heat exchanger is smooth and thorough, and it is also indicated that before the defrosting process, the frosting of the air heat exchanger is not too much or the operating condition (climate condition) of the air heat exchanger is good, so that the time of the next defrosting period can be prolonged appropriately, and at most 20 minutes; if the refrigerant cycle system exits the defrost process due to the satisfaction of condition b, this means the fin temperature T f If the conditions are not met and the defrosting process is finished, the air heat exchanger is possibly not completely defrosted, and the defrosting process is also illustratedThe air heat exchanger is frosted thicker between the passes, so that the time of the next defrosting period can be properly shortened, the next defrosting process can be advanced, and the air heat exchanger (such as fins) is prevented from being frosted thicker.
It should be noted that, the defrosting period refers to a time interval between 2 adjacent defrosting processes, and the duration of the defrosting period should be prolonged as long as possible, so as to prevent excessive defrosting times, so that the defrosting time occupies too high proportion of the heating operation time of the whole air source heat pump unit.
It should be noted that when the refrigerant cycle is in the defrost process, the refrigerant cycle is operated in the cooling mode and the fan is turned off.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (6)
1. The defrosting method of the air source heat pump unit is characterized in that the air source heat pump unit comprises at least two groups of refrigerant circulation systems and a control system connected with the refrigerant circulation systems, each group of refrigerant circulation systems comprises an air side heat exchanger, and the air side heat exchanger is a fin heat exchanger; the control system judges that the refrigerant circulation system meets the following conditions, and allows the refrigerant circulation system to enter a defrosting process:
condition a, ambient temperature T of the environment in which the air-side heat exchanger of the refrigerant cycle system is located air The first preset environmental temperature T0 is less than or equal to air A first preset ambient temperature T0 of 5 ℃ or less air ≤15℃；
The defrosting accumulated running time of the refrigerant circulation system is more than or equal to a defrosting period T;
condition C, when the ambient temperature T air < second preset ambient temperature T1 air The second preset environmental temperature T1 is less than or equal to minus 10 DEG C air When the temperature is less than or equal to 0, the evaporating temperature T e Ambient temperature T < K1% air -C0 and duration t c0 ，t c0 More than 0s, C0 is more than 10 and less than 20, K1 is more than or equal to 0.5 and less than or equal to 0.9; alternatively, when the ambient temperature T air Not less than the second preset environmental temperature T1 air The second preset environmental temperature T1 is less than or equal to minus 10 DEG C air When the temperature is less than or equal to 0, the evaporating temperature T e Ambient temperature T < K2% air -C1 and duration t c1 ，t c1 ＞0s,9＜C1＜19,0.6≤K2≤1.2；
The quantity of the refrigerant circulation systems in the defrosting process is smaller than the quantity N of the allowable defrosting systems of the air source heat pump unit, N is more than 0 and less than or equal to the quantity of the refrigerant circulation systems in the air source heat pump unit, and N is an integer;
condition E, module outlet water temperature T WO The water outlet temperature T0 of the preset module is not less than WO The water outlet temperature T0 of the preset module is less than or equal to 5 DEG C WO The temperature is less than or equal to 15 ℃, and the module is an air source heat pump unit.
2. The defrosting method of an air source heat pump unit according to claim 1, wherein: in condition A, a first preset ambient temperature T0 air 10 ℃; in the condition B, the defrosting period T is 30min; in condition C, the second preset ambient temperature T1 air At-4 ℃, t c0 ＝120s，t c1 =120 s, k1=0.7, c0=13, c1=12, k2=0.8; in the condition D, the number N of the allowable defrosting systems is half of the number of the refrigerant circulation systems in the air source heat pump unit; in condition E, the module water outlet temperature T0 is preset WO Is 10 ℃.
3. The defrosting method of an air source heat pump unit according to claim 1, wherein: the control system judges that the refrigerant circulation system in the defrosting process meets any one of the following conditions, and controls the refrigerant circulation system to exit the defrosting process:
condition a, fin temperature T of air-side heat exchanger of refrigerant cycle system f Not less than a preset defrosting exit fin temperature T f0 The temperature T of a defrosting exit fin is preset at 20 ℃ or less f0 ≤45℃；
Condition b, defrosting operation time T of the refrigerant cycle system C Not less than the maximum time T in defrosting process CMAX The maximum time T of defrosting process is less than or equal to 3min CMAX ≤10min；
A condition c that the refrigerant cycle system high-voltage switch is turned off;
condition d, module water outlet temperature T WO The defrosting exit water outlet temperature T is less than or equal to WO0 Defrosting exit water outlet temperature T of 5 ℃ or less W0 The temperature is less than or equal to 25 ℃, and the module is an air source heat pump unit.
4. A defrosting method of an air source heat pump unit according to claim 3, wherein: the preset defrosting exit fin temperature T f0 30 ℃; the maximum time T of the defrosting process CMAX For 5min; in the condition c, after the high-voltage switch of the refrigerant circulation system is disconnected, the compressor of the refrigerant circulation system is immediately stopped and exits the defrosting process; the defrosting exits the water outlet temperature T W0 Is 10 ℃.
5. A defrosting method of an air source heat pump unit according to claim 3, wherein: the control system may correct a next defrost cycle of the refrigerant cycle based on a condition that the refrigerant cycle exits the current defrost process.
6. The defrosting method of an air source heat pump unit according to claim 5, wherein:
if the refrigerant cycle system in the defrosting process exits the defrosting process because the condition a is satisfied, the control system corrects the next defrosting cycle increase time T of the refrigerant cycle system p1 ，5min≤T p1 Less than or equal to 20min; if the refrigerant cycle system in the defrosting process exits the defrosting process due to the satisfaction of the condition b, the control system corrects the next defrosting cycle reduction time T of the refrigerant cycle system p2 ，5min≤T p2 Less than or equal to 20min; the next defrost cycle of the refrigerant cycle that is modified must be greater than or equal to the minimum allowable defrost cycle T CMIN 0 < allowMinimum value T of defrosting cycle CMIN ≤60min。
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