U.S. patent application number 15/501122 was filed with the patent office on 2018-04-19 for method and system for controlling frequency of variable-frequency compressor in heat pump water heater.
The applicant listed for this patent is GD MIDEA HEATING & VENTILATING EQUIPMENT CO., LTD., MIDEA GROUP CO., LTD.. Invention is credited to Dengke ZHANG.
Application Number | 20180106483 15/501122 |
Document ID | / |
Family ID | 53811159 |
Filed Date | 2018-04-19 |
United States Patent
Application |
20180106483 |
Kind Code |
A1 |
ZHANG; Dengke |
April 19, 2018 |
METHOD AND SYSTEM FOR CONTROLLING FREQUENCY OF VARIABLE-FREQUENCY
COMPRESSOR IN HEAT PUMP WATER HEATER
Abstract
Disclosed are a method and a system for controlling frequency of
a variable-frequency compressor in a heat pump water heater. The
method includes: detecting water temperature of water flowing out
from a heat exchanger and water tank temperature of a water tank;
determining preset water temperature of the water flowing out from
the heat exchanger according to the water tank temperature; and
controlling the frequency of the variable-frequency compressor
according to the water temperature and the preset water
temperature. The present method and system propose a control mode
of frequency of the compressor based on the water temperature of
the water flowing out from the heat exchanger.
Inventors: |
ZHANG; Dengke; (Foshan,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GD MIDEA HEATING & VENTILATING EQUIPMENT CO., LTD.
MIDEA GROUP CO., LTD. |
Foshan
Foshan |
|
CN
CN |
|
|
Family ID: |
53811159 |
Appl. No.: |
15/501122 |
Filed: |
July 16, 2015 |
PCT Filed: |
July 16, 2015 |
PCT NO: |
PCT/CN2015/084252 |
371 Date: |
February 1, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24D 19/1054 20130101;
F25B 49/02 20130101; F24H 9/2021 20130101; F24H 4/04 20130101 |
International
Class: |
F24D 19/10 20060101
F24D019/10; F24H 9/20 20060101 F24H009/20 |
Foreign Application Data
Date |
Code |
Application Number |
May 22, 2015 |
CN |
201510268372.7 |
Claims
1. A method for controlling frequency of a variable-frequency
compressor in a heat pump water heater, comprising: detecting a
water temperature of water flowing out from a heat exchanger and a
water tank temperature of a water tank; determining a preset water
temperature of the water flowing out from the heat exchanger
according to the water tank temperature; and controlling the
frequency of the variable-frequency compressor according to the
water temperature and the preset water temperature.
2. The method according to claim 1, wherein the preset water
temperature is determined according to: T1S=f(T5), where T1S is the
preset water temperature and T5 is the water tank temperature.
3. The method according to claim 2, wherein T1S is computed
according to: T1S=a1*a2*a3*T5+b, where a1 is a first correction
factor for a water-water heat exchanger in the water tank, a2 is a
second correction factor for a capacity of a heat pump group, a3 is
a third correction factor, and b is a temperature difference
correction factor.
4. The method according to claim 1, wherein controlling the
frequency of the variable-frequency compressor according to the
water temperature and the preset water temperature comprises:
acquiring a temperature difference between the water temperature
and the preset water temperature; determining a temperature range
comprising the temperature difference, and acquiring a correction
value according to the temperature range; and determining a target
frequency of the variable-frequency compressor according to the
frequency of the variable-frequency compressor and the correction
value.
5. The method according to claim 4, further comprising: comparing
the target frequency of the variable-frequency compressor with a
working frequency of the heat pump group in a set of working
frequencies; and acquiring a working frequency closest to the
target frequency, and determining the working frequency closest to
the target frequency as the target frequency.
6. The method according to claim 5, wherein determining the working
frequency closest to the target frequency as the target frequency
further comprises: acquiring a minimum working frequency and a
maximum working frequency of the heat pump group under the water
tank temperature; comparing the working frequency with the minimum
working frequency and the maximum working frequency respectively;
and determining the working frequency as the target frequency if
the working frequency is between the minimum working frequency and
the maximum working frequency.
7. The method according to claim 6, wherein acquiring a minimum
working frequency and a maximum working frequency of the heat pump
group under the water tank temperature further comprises:
determining the minimum working frequency and the maximum working
frequency according to an outdoor temperature T4 and the water tank
temperature T5; determining the minimum working frequency and the
maximum working frequency according to a first preset frequency
range, if the outdoor temperature T4 is smaller than or equal to a
first preset temperature threshold and the water tank temperature
T5 is greater than or equal to a second preset temperature
threshold or if the outdoor temperature T4 is greater than a third
preset temperature threshold and the water tank temperature T5 is
greater than or equal to the second preset temperature threshold
such that the variable-frequency compressor is working at the
frequency in the first preset frequency range, wherein the first
preset temperature threshold is smaller than the third preset
temperature threshold; and determining the minimum working
frequency and the maximum working frequency according to a second
preset frequency range, if the outdoor temperature T4 is in a first
preset temperature range and the water tank temperature T5 is in a
second preset temperature range such that the variable-frequency
compressor is working at the frequency in the second preset
frequency range, wherein the first preset frequency range is
narrower than the second preset frequency range.
8. The method according to claim 6, further comprising: determining
the maximum working frequency as the target frequency if the
working frequency is greater than the maximum working frequency;
and determining the minimum working frequency as the target
frequency if the working frequency is smaller than the minimum
working frequency.
9. A system for controlling frequency of a variable-frequency
compressor in a heat pump water heater, comprising: the
variable-frequency compressor; a heat exchanger connected to the
variable-frequency compressor; a first temperature sensor disposed
at a water outlet of the heat exchanger, configured to detect a
water temperature of water flowing out from the heat exchanger; a
water tank connected to the heat exchanger; a second temperature
sensor disposed in the water tank, configured to detect a water
tank temperature; and a controller, configured to acquire the water
temperature from the first temperature sensor and the water tank
temperature from the second temperature sensor, and to determine a
preset water temperature of the water flowing out from the heat
exchanger according to the water tank temperature, and to control
the frequency of the variable-frequency compressor according to the
water temperature and the preset water temperature.
10. The system according to claim 9, wherein the controller
determines the preset water temperature according to: T1S=f(T5),
where T1S is the preset water temperature and T5 is the water tank
temperature.
11. The system according to claim 10, wherein T1S is computed
according to: T1S=a1*a2*a3*T5+b, where a1 is a first correction
factor for a water-water heat exchanger in the water tank, a2 is a
second correction factor for a capacity of a heat pump group, a3 is
a third correction factor, and b is a temperature difference
correction factor.
12. The system according to claim 9, wherein the controller is
configured to: acquire a temperature difference between the water
temperature and the preset water temperature; determine a
temperature range comprising the temperature difference, and
acquire a correction value according to the temperature range; and
determine a target frequency of the variable-frequency compressor
according to the frequency of the variable-frequency compressor and
the correction value.
13. The system according to claim 12, wherein the controller is
further configured to: compare the target frequency of the
variable-frequency compressor with a working frequency of the heat
pump group in a set of working frequencies; and acquire a working
frequency closest to the target frequency, and determine the
working frequency closest to the target frequency as the target
frequency.
14. The system according to claim 13, wherein the controller is
further configured to: acquire a minimum working frequency and a
maximum working frequency of the heat pump group under the water
tank temperature; compare the working frequency with the minimum
working frequency and the maximum working frequency respectively;
and determine the working frequency as the target frequency if the
working frequency is between the minimum working frequency and the
maximum working frequency.
15. The system according to claim 14, wherein the controller is
further configured to: determine the minimum working frequency and
the maximum working frequency according to an outdoor temperature
T4 and the water tank temperature T5; determine the minimum working
frequency and the maximum working frequency according to a first
preset frequency range, if the outdoor temperature T4 is smaller
than or equal to a first preset temperature threshold and the water
tank temperature T5 is greater than or equal to a second preset
temperature threshold or if the outdoor temperature T4 is greater
than a third preset temperature threshold and the water tank
temperature T5 is greater than or equal to the second preset
temperature threshold such that the variable-frequency compressor
is working at the frequency in the first preset frequency range,
wherein the first preset temperature threshold is smaller than the
third preset temperature threshold; and determine the minimum
working frequency and the maximum working frequency according to a
second preset frequency range, if the outdoor temperature T4 is in
a first preset temperature range and the water tank temperature T5
is in a second preset temperature range such that the
variable-frequency compressor is working at the frequency in the
second preset frequency range, wherein the first preset frequency
range is narrower than the second preset frequency range.
16. The system according to claim 14, wherein the controller is
further configured to: determine the maximum working frequency as
the target frequency if the working frequency is greater than the
maximum working frequency; and determine the minimum working
frequency as the target frequency if the working frequency is
smaller than the minimum working frequency.
17. The system according to claim 9, wherein the heat exchanger is
one of a water-refrigerant heat exchanger and air-refrigerant heat
exchanger.
18. The system according to claim 17, wherein the water tank
comprises a water-water heat exchanger connected to the
water-refrigerant heat exchanger via a circulating water pump.
19. A heat pump water heater, comprising a system for controlling
frequency of a variable-frequency compressor in a heat pump water
heater according to claim 9.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a U.S. national phase application of
International Application No. PCT/CN2015/084252, filed with the
State Intellectual Property Office of P. R. China on Jul. 16, 2015,
which claims priority to and benefits of Chinese Patent Application
Serial No. 201510268372.7, entitled "Method and system for
controlling frequency of variable-frequency compressor in heat pump
water heater", filed with the State Intellectual Property Office of
P. R. China on May. 22, 2015, the entire content of which is
incorporated herein by reference.
FIELD
[0002] The present disclosure relates to heat pump water heater
technology, and more particularly relates to a method and a system
for controlling frequency of a variable-frequency compressor in a
heat pump water heater.
BACKGROUND
[0003] In recent years, as an effective energy-saving and
environment-friendly equipment, the heat pump water heater has been
used increasingly around the world. With the development of
variable-frequency technology, the variable-frequency heat pump
water heater is emerging. A heating capacity and an energy
efficiency of the variable-frequency heat pump water heater are
higher than those of the fixed-frequency heat pump water heater,
especially under low environment temperature.
[0004] At present, in the frequency control method used for the
variable-frequency compressor in the heat pump water heater, a
difference between target temperature of a water tank and current
temperature of the water tank is regarded as a feedback, i.e., when
the difference is greater than a certain value, the
variable-frequency compressor is working at a high frequency as far
as possible to produce more heat and shorten a heating time; and
when the difference is smaller than the certain value, the
frequency of the variable-frequency compressor is adjusted
dynamically, and in order to ensure that temperature of the water
tank is maintained within a target temperature range, the
variable-frequency compressor is working at a lower frequency
generally.
[0005] In general, heat produced by the variable-frequency heat
pump water heater may increase with an increase of the frequency of
the variable-frequency compressor thereof. However, an energy
efficiency ratio of the heat pump water heater changes in shape of
a parabola, which means that the energy efficiency ratio may
decrease with an increase of the frequency of the
variable-frequency compressor when the frequency is higher than a
certain frequency, and the energy efficiency ratio may decrease
with a decrease of the frequency of the variable-frequency
compressor when the frequency is lower than the certain frequency.
Thus, with an existing method for controlling the frequency of the
variable-frequency compressor in the heat pump water heater by
controlling the temperature in the water tank, the energy-saving
advantage of the variable-frequency heat pump water heater cannot
be exploited sufficiently and reliability of the variable-frequency
compressor cannot be guaranteed. Additionally, a maximum pressure
of the variable-frequency compressor may increase firstly and
decrease subsequently with an increase of the frequency.
SUMMARY
[0006] Embodiments of the present disclosure seek to solve at least
one of the problems existing in the related art to at least some
extent.
[0007] Accordingly, a first objective of the present disclosure is
to provide a method for controlling frequency of a
variable-frequency compressor in a heat pump water heater.
[0008] A second objective of the present disclosure is to provide a
system for controlling frequency of a variable-frequency compressor
in a heat pump water heater.
[0009] In order to achieve the above objectives, the method for
controlling frequency of the variable-frequency compressor in the
heat pump water heater according to embodiments of a first aspect
of the present disclosure includes: detecting a water temperature
of water flowing out from a heat exchanger and a water tank
temperature of a water tank; determining a preset water temperature
of the water flowing out from the heat exchanger according to the
water tank temperature; and controlling the frequency of the
variable-frequency compressor according to the water temperature
and the preset water temperature.
[0010] In order to achieve the above objectives, the system for
controlling frequency of the variable-frequency compressor in the
heat pump water heater according to embodiments of a second aspect
of the present disclosure includes: the variable-frequency
compressor; a heat exchanger connected to the variable-frequency
compressor; a first temperature sensor disposed at a water outlet
of the heat exchanger, configured to detect a water temperature of
water flowing out from the heat exchanger; a water tank connected
to the heat exchanger; a second temperature sensor disposed in the
water tank, configured to detect a water tank temperature; and a
controller, configured to acquire the water temperature from the
first temperature sensor and the water tank temperature from the
second temperature sensor, and to determine a preset water
temperature of the water flowing out from the heat exchanger
according to the water tank temperature, and to control the
frequency of the variable-frequency compressor according to the
water temperature and the preset water temperature.
[0011] Additional aspects and advantages of embodiments of present
disclosure will be given in part in the following descriptions,
become apparent in part from the following descriptions, or be
learned from the practice of the embodiments of the present
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] These and other aspects and advantages of embodiments of the
present disclosure will become apparent and more readily
appreciated from the following descriptions made with reference to
the drawings, in which:
[0013] FIG. 1 is a flow chart of a method for controlling frequency
of a variable-frequency compressor in a heat pump water heater
according to an embodiment of the present disclosure;
[0014] FIG. 2 is a schematic diagram of a system for controlling
frequency of a variable-frequency compressor in a heat pump water
heater according to an embodiment of the present disclosure;
[0015] FIG. 3 is a schematic diagram of a system for controlling
frequency of a variable-frequency compressor in a heat pump water
heater according to an embodiment of the present disclosure.
REFERENCE NUMERALS
[0016] Variable-frequency compressor 10, heat exchanger 20, first
temperature sensor 30, water tank 40, second temperature sensor 50,
controller 60, throttle 70, circulating water pump 80, water-water
heat exchanger 90 in the water tank and water-refrigerant heat
exchanger 21.
DETAILED DESCRIPTION
[0017] Reference will be made in detail to embodiments of the
present disclosure, where the same or similar elements and the
elements having same or similar functions are denoted by like
reference numerals throughout the descriptions. The embodiments
described herein with reference to drawings are explanatory, and
used to generally understand the present disclosure. The
embodiments shall not be construed to limit the present
disclosure.
[0018] A method and a system for controlling frequency of a
variable-frequency compressor in a heat pump water heater according
to embodiments of the present disclosure will be further described
with reference to drawings.
[0019] FIG. 1 is a flow chart of the method for controlling
frequency of the variable-frequency compressor in the heat pump
water heater according to an embodiment of the present
disclosure.
[0020] As shown in FIG. 1, the method for controlling frequency of
the variable-frequency compressor in the heat pump water heater may
include following acts.
[0021] In act S101, water temperature of water flowing out from a
heat exchanger and water tank temperature of a water tank are
detected.
[0022] Specifically, when the variable-frequency heat pump water
heater is working, a first temperature sensor disposed at a water
outlet of the heat exchanger may detect the water temperature of
the water flowing out from the heat exchanger, and a second
temperature sensor disposed in the water tank may detect the water
tank temperature.
[0023] In act S102, preset water temperature of the water flowing
out from the heat exchanger is determined according to the water
tank temperature.
[0024] After the water tank temperature is acquired, the preset
water temperature T1S may be determined according to:
T1S=f(T5)
where T5 is the water tank temperature.
[0025] For example, T1S=a1*a2*a3*T5+b, where a1 is a first
correction factor for a water-water heat exchanger in the water
tank, a2 is a second correction factor for a capacity of a heat
pump group, a3 is a third correction factor, and b is a temperature
difference correction factor.
[0026] It should be noted that the first correction factor for the
water-water heat exchanger in the water tank, the second correction
factor for a capacity of a heat pump group, the third correction
factor and the temperature difference correction factor may be set
according to a practical operating condition, which means that
different values may be assigned to each of the water-water heat
exchanger in the water tank, the second correction factor for a
capacity of a heat pump group, the third correction factor and the
temperature difference correction factor in different operating
conditions.
[0027] In act S103, the frequency of the variable-frequency
compressor is controlled according to the water temperature and the
preset water temperature.
[0028] In an embodiment of the present disclosure, after the preset
water temperature of the water flowing out from the heat exchanger
is determined according to the water tank temperature, a
temperature difference between the water temperature and the preset
water temperature may be acquired firstly, and then a temperature
range including the temperature difference may be determined, and a
correction value may be acquired according to the temperature
range, and a target frequency of the variable-frequency compressor
may be determined according to the current frequency of the
variable-frequency compressor and the correction value.
[0029] A corresponding relationship between the temperature range
including the temperature difference and the correction value for
the frequency of the variable-frequency compressor may be
pre-stored in a frequency controlling system of the
variable-frequency compressor, and the temperature difference is a
result obtained by subtracting the preset water temperature from
the water temperature.
[0030] For example, a table of the pre-stored corresponding
relationship between the temperature range and the correction value
is shown in Table. 1.
TABLE-US-00001 TABLE 1 Table of the corresponding relationship
temperature range (.degree. C.) correction value (Hz) (2, 3] -8 Hz
(1, 2] -4 Hz [-1, 1] 0 Hz (-1, -2] 4 Hz (-2, -3] 8 Hz
[0031] It should be noted that Table. 1 only shows an example or a
part of the corresponding relationship.
[0032] For example, assume that the corresponding relationship is
shown in Table. 1, the preset water temperature measured by a
thermometer in the water tank is 14.degree. C., the water
temperature of the water flowing out from the heat exchanger
acquired by the second temperature sensor is 15.6.degree. C., and
the current frequency of the variable-frequency compressor is 18
Hz, then the temperature difference between the water temperature
and the preset water temperature is computed as 1.6.degree. C.
which falls into the temperature range (1, 2] according to Table.
1, and the temperature range (1, 2] corresponds the correction
value -4 Hz. Thus, the target frequency of the variable-frequency
compressor is acquired by adding the correction value to the
current frequency of the variable-frequency compressor, i.e., the
target frequency is 12 Hz.
[0033] Additionally, in this embodiment, after the target frequency
is determined according to the current frequency of the
variable-frequency compressor and the correction value, the target
frequency can also be adjusted according to a working frequency of
the heat pump group.
[0034] Specifically, the working frequency closest to the target
frequency may be acquired by comparing the target frequency with
the working frequency of the heat pump group in a set of working
frequencies.
[0035] Generally, the heat pump group works at different
frequencies belong to different working frequency ranges under
different water tank temperatures. After the working frequency
closest to the target frequency is acquired, a minimum working
frequency and a maximum working frequency of the heat pump group
may be acquired firstly under the current water tank temperature,
and the working frequency may be compared with the minimum working
frequency and the maximum working frequency respectively. The
working frequency may be determined as the target frequency if the
working frequency is between the minimum working frequency and the
maximum working frequency, and the maximum working frequency may be
determined as the target frequency if the working frequency is
greater than the maximum working frequency, and the minimum working
frequency may be determined as the target frequency if the working
frequency is smaller than the minimum working frequency.
[0036] In an embodiment of the present disclosure, the minimum
working frequency and the maximum working frequency may be
determined according to outdoor temperature T4 and the water tank
temperature T5. Specifically, a working frequency range of the
variable-frequency compressor relates to the outdoor temperature T4
and the water tank temperature T5. Specifically, if the outdoor
temperature T4 is smaller than or equal to a first preset
temperature threshold and the water tank temperature T5 is greater
than or equal to a second preset temperature threshold, or if the
outdoor temperature T4 is greater than a third preset temperature
threshold and the water tank temperature T5 is greater than or
equal to the second preset temperature threshold, the
variable-frequency compressor is working at a frequency in a first
preset frequency range, the minimum working frequency and the
maximum working frequency may be determined according to the first
preset frequency range; and if the outdoor temperature T4 is in a
first preset temperature range and the water tank temperature T5 is
in a second preset temperature range, the variable-frequency
compressor is working at a frequency in a second preset frequency
range, the minimum working frequency and the maximum working
frequency may be determined according to the second preset
frequency range.
[0037] It should be noted that the first preset temperature
threshold is smaller than the third preset temperature threshold
and the first preset frequency range is narrower than the second
preset frequency range.
[0038] For example, assume that the first temperature threshold is
-5.degree. C., the second temperature threshold is 50.degree. C.,
the third temperature threshold is 30.degree. C., the second
temperature threshold is 50.degree. C., the first temperature range
is 5.degree. C.-20.degree. C. and the second temperature range is
20.degree. C.-40.degree. C. If the outdoor temperature T4 is
smaller than or equal to -5.degree. C. and the water tank
temperature T5 is greater than or equal to 50.degree. C., or if the
outdoor temperature T4 is greater than 30.degree. C. and the water
tank temperature T5 is greater than or equal to 50.degree. C., the
variable-frequency compressor is working at a frequency in a range
of 42-60 Hz, and the minimum working frequency may be determined as
42 Hz and the maximum working frequency may be determined as 60 Hz;
and if the outdoor temperature T4 is in 5.degree. C.-20.degree. C.
and the water tank temperature T5 is in 20.degree. C.-40.degree.
C., the variable-frequency compressor is working at a frequency in
a range of 10-92 Hz, and the minimum working frequency may be
determined as 10 Hz and the maximum working frequency may be
determined as 92 Hz. For example, assume that the target frequency
Fs of the variable-frequency compressor computed according to the
water temperature and the preset water temperature is 15 Hz, the
set of working frequencies of the heat pump group includes a first
working frequency F1 equal to 10 Hz, a second working frequency F2
equal to 14 Hz, a third working frequency F3 equal to 18 Hz and a
fourth working frequency F4 equal to 22 Hz. If the maximum working
frequency F.sub.max of the heat pump group under the current water
tank temperature is 17 Hz and the minimum working frequency
F.sub.min of the heat pump group under the current water tank
temperature is 11 Hz, after the target frequency Fs is acquired,
the working frequency closest to the target frequency Fs is the
second working frequency F2 by comparing the target frequency Fs
with each of the set of working frequencies, and because 14 Hz is
between 11 Hz and 17 Hz, the second working frequency F2 is
determined as the target frequency, such that the
variable-frequency compressor works at 14 Hz.
[0039] Thus, by using the water temperature of the water flowing
out from the heat exchanger to control the frequency of the
variable-frequency compressor, the working frequency of the
variable-frequency compressor may be reduced and the working energy
efficiency of the heat pump group may be improved effectively. The
minimum frequency of the heat pump group may be limited when the
water temperature is high, such that the reliability of the
variable-frequency compressor may be guaranteed.
[0040] With the method according to embodiments of the present
disclosure, the water temperature of the water flowing out from the
heat exchanger and the water tank temperature of the water tank are
firstly detected, and then the preset water temperature of the
water flowing out from the heat exchanger is determined according
to the water tank temperature; and the frequency of the
variable-frequency compressor is controlled according to the water
temperature and the preset water temperature. The embodiments of
the present disclosure provide a method for controlling the
frequency of the variable-frequency compressor based on the water
temperature of the water flowing out from the heat exchanger. When
temperature in a water tank is low, working frequency of the
variable-frequency compressor may be reduced effectively, such that
working energy efficiency of a heat pump group may be improved.
Meanwhile, in case of ensuring constant water temperature, working
minimum frequency of the variable-frequency compressor may be
controlled effectively and thus reliability of the
variable-frequency compressor may be guaranteed.
[0041] In order to achieve the above objectives, embodiments of the
present disclosure also provide a system for controlling frequency
of a variable-frequency compressor in a heat pump water heater.
[0042] FIG. 2 is a schematic diagram of a system for controlling
frequency of a variable-frequency compressor in a heat pump water
heater according to an embodiment of the present disclosure.
[0043] As shown in FIG. 2, the system for controlling the frequency
of the variable-frequency compressor in the heat pump water heater
includes the variable-frequency compressor 10, a heat exchanger 20
connected to the variable-frequency compressor 10, a first
temperature sensor 30 disposed at a water outlet of the heat
exchanger 20, a water tank 40 connected to the heat exchanger 20, a
second temperature sensor 50 disposed in the water tank 40 and a
controller 60.
[0044] The first temperature sensor 30 is configured to detect
water temperature of water flowing out from the heat exchanger 20;
the second temperature sensor 50 is configured to detect water tank
temperature of the water tank 40; and the controller is configured
to acquire the water temperature of the water flowing out from the
heat exchanger 20 from the first temperature sensor 30 and the
water tank temperature of the water tank 40 from the second
temperature sensor 50, and to determine preset water temperature of
the water flowing out from the heat exchanger 20 according to the
water tank temperature, and to control the frequency of the
variable-frequency compressor 10 according to the water temperature
and the preset water temperature of the water flowing out from the
heat exchanger 20.
[0045] The controller 60 may determine the preset water temperature
T1S according to:
T1S=f(T5),
in which T5 is the water tank temperature.
[0046] For example, T1S=a1*a2*a3*T5+b, in which a1 is a first
correction factor for a water-water heat exchanger in the water
tank, a2 is a second correction factor for a capacity of a heat
pump group, a3 is a third correction factor, and b is a temperature
difference correction factor.
[0047] It should be noted that the first correction factor for the
water-water heat exchanger in the water tank, the second correction
factor for a capacity of a heat pump group, the third correction
factor and the temperature difference correction factor may be set
according to a practical operating condition, which means that each
of the water-water heat exchanger in the water tank, the second
correction factor for a capacity of a heat pump group, the third
correction factor and the temperature difference correction factor
may be have different values in different operating conditions.
[0048] After the controller 60 determines the preset water
temperature of the water flowing out from the heat exchanger 20
according to the water tank temperature, the controller 60 may
acquire a temperature difference between the water temperature of
the water flowing out from the heat exchanger 20 and the preset
water temperature firstly, determine a temperature range including
the temperature difference and acquire a correction value according
to the temperature range, and determine a target frequency of the
variable-frequency compressor 10 according to the current frequency
of the variable-frequency compressor 10 and the correction
value.
[0049] For example, a table of the pre-stored corresponding
relationship between the temperature range and the correction value
is shown in Table. 1.
TABLE-US-00002 TABLE 1 Table of the corresponding relationship
temperature range (.degree. C.) correction value (Hz) (2, 3] -8 Hz
(1, 2] -4 Hz [-1, 1] 0 Hz (-1, -2] 4 Hz (-2, -3] 8 Hz
[0050] It should be noted that Table. 1 only shows an example or a
part of the corresponding relationship.
[0051] For example, assume that the corresponding relationship is
shown in Table. 1, the preset water temperature of the water
flowing out from the heat exchanger 20 computed according to the
water tank temporary is 14.degree. C., the water temperature of the
water flowing out from the heat exchanger acquired by the second
temperature sensor 50 is 15.6.degree. C., and the current frequency
of the variable-frequency compressor 10 is 18 Hz. The temperature
difference between the water temperature and the preset water
temperature is computed as 1.6.degree. C. which falls into the
temperature range (1, 2] according to Table. 1, and the temperature
range (1, 2] corresponds the correction value -4 Hz. Thus, the
target frequency of the variable-frequency compressor is acquired
by adding the correction value to the current frequency of the
variable-frequency compressor, i.e., the target frequency is 12
Hz.
[0052] Additionally, in this embodiment, after the controller 60
determines the target frequency of the variable-frequency
compressor 10 according to the current frequency of the
variable-frequency compressor 10 and the correction value, the
controller 60 may also adjust the target frequency according to a
working frequency of the heat pump group.
[0053] Specifically, the controller 60 may acquire the working
frequency closest to the target frequency of the variable-frequency
compressor 10 by comparing the target frequency with a working
frequency of the heat pump group in a set of working
frequencies.
[0054] Generally, working frequency ranges of the heat pump group
are different in different water tank temperatures. After the
controller 60 acquires the working frequency closest to the target
frequency, a minimum working frequency and a maximum working
frequency of the heat pump group may be acquired firstly under the
current water tank temperature, and the working frequency closest
to the target frequency may be compared with the minimum working
frequency and the maximum working frequency respectively. The
working frequency closest to the target frequency may be determined
as the target frequency if the working frequency closest to the
target frequency is between the minimum working frequency and the
maximum working frequency, and the maximum working frequency may be
determined as the target frequency if the working frequency closest
to the target frequency is greater than the maximum working
frequency, and the minimum working frequency may be determined as
the target frequency if the working frequency closest to the target
frequency is smaller than the minimum working frequency.
[0055] In an embodiment of the present disclosure, the controller
60 may determine the minimum working frequency and the maximum
working frequency according to outdoor temperature T4 and the water
tank temperature T5. Specifically, a working frequency range of the
variable-frequency compressor relates to the outdoor temperature T4
and the water tank temperature T5. Specifically, if the outdoor
temperature T4 is smaller than or equal to a first preset
temperature threshold and the water tank temperature T5 is greater
than or equal to a second preset temperature threshold, or if the
outdoor temperature T4 is greater than a third preset temperature
threshold and the water tank temperature T5 is greater than or
equal to the second preset temperature threshold, the
variable-frequency compressor is working at a frequency in a first
preset frequency range, and the minimum working frequency and the
maximum working frequency may be determined according to the first
preset frequency range; and if the outdoor temperature T4 is in a
first preset temperature range and the water tank temperature T5 is
in a second preset temperature range, the variable-frequency
compressor is working at a frequency in a second preset frequency
range, and the minimum working frequency and the maximum working
frequency may be determined according to the second preset
frequency range.
[0056] It should be noted that the first preset temperature
threshold is smaller than the third preset temperature threshold
and the first preset frequency range is narrower than the second
preset frequency range.
[0057] For example, assume that the first temperature threshold is
-5.degree. C., the second temperature threshold is 50.degree. C.,
the third temperature threshold is 30.degree. C., the first
temperature range is 5.degree. C.-20.degree. C. and the second
temperature range is 20.degree. C.-40.degree. C. If the outdoor
temperature T4 is smaller than or equal to -5.degree. C. and the
water tank temperature T5 is greater than or equal to 50.degree.
C., or if the outdoor temperature T4 is greater than 30.degree. C.
and the water tank temperature T5 is greater than or equal to
50.degree. C., the working frequency range of the
variable-frequency compressor is 42-60 Hz and then the control 60
may determine the minimum working frequency as 42 Hz and the
maximum working frequency as 60 Hz; and if the outdoor temperature
T4 is in 5.degree. C.-20.degree. C., the water tank temperature T5
is in 20.degree. C.-40.degree. C., the working frequency range of
the variable-frequency compressor is 10-92 Hz and then the
controller 60 may determine that the minimum working frequency is
10 Hz and the maximum working frequency is 92 Hz.
[0058] For example, assume that the target frequency Fs of the
variable-frequency compressor 10 computed according to the water
temperature and the preset water temperature is 15 Hz, the set of
working frequencies of the heat pump group includes a first working
frequency F1 equal to 10 Hz, a second working frequency F2 equal to
14 Hz, a third working frequency F3 equal to 18 Hz and a fourth
working frequency F4 equal to 22 Hz. If the maximum working
frequency F.sub.max of the heat pump group under the current water
tank temperature is 17 Hz and the minimum working frequency
F.sub.min of the heat pump group under the current water tank
temperature is 11 Hz, after the target frequency Fs is acquired, it
may be determined that the working frequency closest to the target
frequency Fs is the second working frequency F2 by comparing the
target frequency Fs with each of the set of working frequencies,
and because 14 Hz is between 11 Hz and 17 Hz, the controller 60 may
determine that the second working frequency F2 is the target
frequency of the variable-frequency compressor 10 and enables the
variable-frequency compressor 10 to work at 14 Hz.
[0059] FIG. 3 illustrates a schematic diagram of a system for
controlling frequency of a variable-frequency compressor in a heat
pump water heater. The heat exchanger 20 between variable-frequency
compressor 10 and the throttle 70 may be a water- refrigerant heat
exchanger or an air-refrigerant heat exchanger. The water tank 40
includes a second temperature sensor 50 and a water-water heat
exchanger 90, and the water-water heat exchanger 90 in the water
tank is connected to the water-refrigerant heat exchanger 21 via a
circulating water pump 80.
[0060] With the system according to embodiments of the present
disclosure, the controller acquires the water temperature from the
first temperature sensor and the water tank temperature from the
second temperature sensor, and then determines preset water
temperature according to the water tank temperature, and controls
the frequency of the variable-frequency compressor according to the
water temperature and the preset water temperature. The embodiments
of the present disclosure provide a method for controlling the
frequency of the variable-frequency compressor based on the water
temperature of the water flowing out from the heat exchanger. When
temperature in a water tank is low, working frequency of the
variable-frequency compressor may be reduced effectively, such that
working energy efficiency may be improved. Meanwhile, in case of
ensuring the water temperature is constant, working minimum
frequency of the variable-frequency compressor may be controlled
effectively and thus reliability of the variable-frequency
compressor may be ensured.
[0061] In the description of embodiments of the present disclosure,
reference throughout this specification to "one embodiment", "some
embodiments," "an embodiment" , "a specific example," or "some
examples," means that a particular feature, structure, material, or
characteristic described in connection with the embodiment or
example is included in at least one embodiment or example of the
present disclosure. In this specification, the appearances of the
phrases in various places throughout this specification are not
necessarily referring to the same embodiment or example of the
present disclosure. Furthermore, the particular features,
structures, materials, or characteristics may be combined in any
suitable manner in one or more embodiments or examples. In
addition, in a case without contradictions, different embodiments
or examples or features of different embodiments or examples may be
combined by those skilled in the art.
[0062] Those skilled in the art shall understand that terms such as
"first" and "second" are used herein for purposes of description
and are not intended to indicate or imply relative importance or
significance. Thus, the feature defined with "first" and "second"
may comprise one or more this feature. In the description of the
present disclosure, "a plurality of" means two or more than two,
unless specified otherwise.
[0063] It will be understood that, the flow chart or any process or
method described herein in other manners may represent a module,
segment, or portion of code that comprises one or more executable
instructions to implement the specified logic function(s) or that
comprises one or more executable instructions of the steps of the
progress. And the scope of a preferred embodiment of the present
disclosure includes other implementations in which the order of
execution may differ from that which is depicted in the flow chart,
which should be understood by those skilled in the art.
[0064] The logic and/or step described in other manners herein or
shown in the flow chart, for example, a particular sequence table
of executable instructions for realizing the logical function, may
be specifically achieved in any computer readable medium to be used
by the instruction execution system, device or equipment (such as
the system based on computers, the system comprising processors or
other systems capable of obtaining the instruction from the
instruction execution system, device and equipment and executing
the instruction), or to be used in combination with the instruction
execution system, device and equipment. As to the specification,
"the computer readable medium" may be any device adaptive for
including, storing, communicating, propagating or transferring
programs to be used by or in combination with the instruction
execution system, device or equipment. More specific examples of
the computer readable medium comprise but are not limited to: an
electronic connection (an electronic device) with one or more
wires, a portable computer enclosure (a magnetic device), a random
access memory (RAM), a read only memory (ROM), an erasable
programmable read-only memory (EPROM or a flash memory), an optical
fiber device and a portable compact disk read-only memory (CDROM).
In addition, the computer readable medium may even be a paper or
other appropriate medium capable of printing programs thereon, this
is because, for example, the paper or other appropriate medium may
be optically scanned and then edited, decrypted or processed with
other appropriate methods when necessary to obtain the programs in
an electric manner, and then the programs may be stored in the
computer memories.
[0065] It should be understood that the various parts of the
present disclosure may be realized by hardware, software, firmware
or combinations thereof. In the above embodiments, a plurality of
steps or methods may be stored in a memory and achieved by software
or firmware executed by a suitable instruction executing system.
For example, if it is realized by the hardware, likewise in another
embodiment, the steps or methods may be realized by one or a
combination of the following techniques known in the art: a
discrete logic circuit having a logic gate circuit for realizing a
logic function of a data signal, an application-specific integrated
circuit having an appropriate combination logic gate circuit, a
programmable gate array (PGA), a field programmable gate array
(FPGA), etc.
[0066] Those skilled in the art shall understand that all or parts
of the steps in the above exemplifying method of the present
disclosure may be achieved by commanding the related hardware with
programs. The programs may be stored in a computer readable memory
medium, and the programs comprise one or a combination of the steps
in the method embodiments of the present disclosure when run on a
computer.
[0067] In addition, each function cell of the embodiments of the
present disclosure may be integrated in a processing module, or
these cells may be separate physical existence, or two or more
cells are integrated in a processing module. The integrated module
may be realized in a form of hardware or in a form of software
function modules. When the integrated module is realized in a form
of software function module and is sold or used as a standalone
product, the integrated module may be stored in a computer readable
memory medium.
[0068] The above-mentioned memory medium may be a read-only memory,
a magnetic disc, an optical disc, etc. Although explanatory
embodiments have been shown and described, it would be appreciated
that the above embodiments are explanatory and cannot be construed
to limit the present disclosure, and changes, alternatives, and
modifications can be made in the embodiments without departing from
scope of the present disclosure by those skilled in the art.
* * * * *