CN114383321A - Energy-saving control system and control method for outlet water temperature of directly-heated heat pump water heater - Google Patents
Energy-saving control system and control method for outlet water temperature of directly-heated heat pump water heater Download PDFInfo
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- CN114383321A CN114383321A CN202111638579.0A CN202111638579A CN114383321A CN 114383321 A CN114383321 A CN 114383321A CN 202111638579 A CN202111638579 A CN 202111638579A CN 114383321 A CN114383321 A CN 114383321A
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 403
- 238000000034 method Methods 0.000 title claims abstract description 19
- 238000009413 insulation Methods 0.000 claims description 30
- 230000017525 heat dissipation Effects 0.000 claims description 24
- 239000007788 liquid Substances 0.000 claims description 19
- 239000011810 insulating material Substances 0.000 claims description 12
- 239000012774 insulation material Substances 0.000 claims description 12
- 238000003860 storage Methods 0.000 claims description 12
- 230000001105 regulatory effect Effects 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 abstract description 15
- 238000005265 energy consumption Methods 0.000 description 3
- 239000002351 wastewater Substances 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 229920002635 polyurethane Polymers 0.000 description 2
- 239000004814 polyurethane Substances 0.000 description 2
- 238000004321 preservation Methods 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000012795 verification Methods 0.000 description 2
- 239000002918 waste heat Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
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- 238000010586 diagram Methods 0.000 description 1
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- 238000004134 energy conservation Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H4/00—Fluid heaters characterised by the use of heat pumps
- F24H4/02—Water heaters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H9/00—Details
- F24H9/20—Arrangement or mounting of control or safety devices
- F24H9/2007—Arrangement or mounting of control or safety devices for water heaters
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Abstract
The invention discloses a directly-heated heat pump water heater water outlet temperature energy-saving control system and a control method thereof. According to the structure, the energy-saving control system and the control method for the outlet water temperature of the directly-heated heat pump water heater can obtain higher energy efficiency ratio and larger heating capacity on the premise of meeting the use requirement, and meanwhile, the heat loss of the hot water system is smaller, and the system is more energy-saving.
Description
Technical Field
The invention relates to the technical field of producing domestic hot water by a heat pump water heater, in particular to a directly-heated heat pump water heater water outlet temperature energy-saving control system and a control method thereof.
Background
The outlet water temperature of the existing directly-heated heat pump water heater is controlled in a constant temperature mode, after a user sets a temperature, the equipment can automatically (in two modes of mechanical control by adopting a condensation regulating valve and electronic control by adopting an electric valve) run at the set temperature in a constant temperature mode, and the user can only consider the set value for regulating the temperature when seasons change; although the outlet water temperature of the hot water machine is changed in the working process of the circulating heating type heat pump water heater, the temperature of the final water tank is still an artificially set constant value, and a user can consider the set value for adjusting the temperature of the water tank only when seasons change. Although the constant temperature control scheme is simple and easy to implement, the disadvantage is also obvious in a centralized hot water supply system, namely, the set temperature value is obviously higher, because the hot water pipeline is long and the heat loss is large in the centralized hot water supply system, and a user can only leave a large margin under the condition that the heat loss cannot be accurately predicted, namely, the temperature of the hot water is increased to balance the heat loss. The rising of the outlet water temperature affects the energy efficiency ratio and the heating capacity of the heat pump, particularly in winter with the most hot water demand, and in addition, because the heat loss is in direct proportion to the temperature difference, the rising of the hot water temperature increases the heat loss of the system, and in some centralized hot water supply systems, the heat loss accounts for more than 50% of the total energy consumption.
Disclosure of Invention
The invention aims to: the system and the method have the advantages that the influence of the heat loss of the system and the current water quantity and the current water temperature in the water tank is comprehensively estimated, the temperature control of the heat pump water heater is changed from constant temperature control to dynamic control according to the change of field conditions, so that the outlet water temperature of the heat pump water heater is lower when the heat pump water heater works on the premise that the terminal outlet water temperature meets the user requirements, a higher energy efficiency ratio and a larger heating capacity are obtained on the premise that the use requirements are met, meanwhile, the internal and external temperature difference is low when hot water is stored and conveyed, the heat loss of a hot water system is smaller, and the system is more energy-saving.
The technical scheme adopted by the invention is as follows:
the energy-saving control system for the outlet water temperature of the directly-heated heat pump water heater comprises the heat pump water heater which communicates a clear water pipe for heat exchange, a hot water outlet pipe of the heat pump water heater is communicated with a water inlet of a hot water storage tank, a water outlet of the hot water storage tank is respectively communicated with water pipes in pipeline wells of water using units through hot water supply pipes, the water pipes in the pipeline wells are respectively communicated with water using devices, the water pipes in the pipeline wells are communicated with a water return port of the hot water storage tank through a hot water return pipe, an electric regulating valve and a temperature sensor A for measuring the outlet water temperature of the heat pump are respectively arranged on the hot water outlet pipe, the hot water storage tank is provided with a temperature sensor B for measuring the temperature in the water tank, a liquid level sensor for measuring the liquid level in the water tank and a temperature sensor C for measuring the ambient temperature of the water tank, and a temperature sensor D for measuring the ambient temperature of the pipeline wells is also arranged in the pipeline wells, the temperature control system is characterized by further comprising an industrial personal computer and a temperature PID controller, wherein the temperature sensor B, the liquid level sensor, the temperature sensor C and the temperature sensor D are all electrically connected with the industrial personal computer, the temperature PID controller is respectively electrically connected with the industrial personal computer, the temperature sensor A and the electric regulating valve, the industrial personal computer calculates a set temperature signal according to signals measured by the temperature sensor B, the liquid level sensor, the temperature sensor C and the temperature sensor D, the temperature PID controller performs PID control on the electric regulating valve according to a set temperature value ts2 obtained by the industrial personal computer and a temperature value tc measured by the temperature sensor A, and a water supply pump is communicated with the water supply pipe.
The invention has the further improvement scheme that a sterilizer is also communicated with the hot water supply pipe.
The method for performing energy-saving control on the outlet water temperature of the direct heat type heat pump water heater by using the control system comprises the following steps:
s1, calculating the heat loss of the hot water pipeline through the formula (1):
Q1= T1 P1/1000 （1）
wherein:
Q1the hot water pipe dissipates the heat energy,
T1-the total length of the hot water circulation of the pipeline,
P1-hot water pipe heat dissipation loss rate;
s2, calculating the heat loss of the water tank through a formula (2):
wherein:
Q2-the hot water tank dissipates heat,
T2the total heat dissipation time of the hot water tank is long,
P2-hot water tank heat dissipation loss rate;
s3, firstly, calculating to obtain a set value of the temperature of the hot water tank through a formula (3):
wherein:
ts1-a set value for the temperature of the water in the hot water tank,
tz-the temperature of the outlet water is required by the terminal,
H1the upper limit of the liquid level of the water tank during the hot water production,
Sj-the cross-sectional area of the inside of the water tank,
Q1the hot water pipe dissipates the heat energy,
Q2-the hot water tank dissipates heat;
and calculating to obtain a set value of the outlet water temperature of the heat pump water heater by a formula (4):
wherein:
ts2the outlet water temperature set value of the heat pump water heater,
ts1-a set value for the temperature of the water in the hot water tank,
tn0-the temperature of the water in the water tank,
H1the upper limit of the liquid level of the water tank during the hot water production,
h1-the tank level;
s4, the industrial control computer compares ts2The value is issued to a temperature PID controller, and the temperature PID controller reads the temperature value of the temperature sensor A in a circulating way and corresponds to ts2Comparing the set values to obtain a difference value e, and according to the set KP proportional adjustment coefficient, the KI integral adjustment coefficient, the KD differential adjustment coefficient and the formula (5):
the u value is obtained after operation, the opening degree of the valve is controlled and adjusted according to the characteristic output of the electric adjusting valve, and finally the outlet water temperature of the heat pump water heater reaches ts2And (5) setting the value.
In a further improvement of the present invention, in step S1, the heat loss rate P of the hot water pipeline is1Calculated by equation (6):
wherein:
P1-the heat dissipation loss rate of the hot water pipeline,
tz-the required temperature of the outlet water of the terminal,
tw-the ambient temperature of the pipe well or the ambient temperature outside the pipe,
l is the length of the pipeline,
αq-the thermal resistivity of the rest of the pipe,
Rbthe thermal resistance of the pipeline heat-insulating material,
Rwthermal resistance from the outer surface of the pipe insulation layer to the surrounding medium.
According to a further improvement of the invention, the thermal resistance R from the outer surface of the insulating layer of the hot water pipeline to the surrounding medium iswCalculated by the public (7) is:
wherein:
Rwthe thermal resistance from the outer surface of the pipeline insulating layer to the surrounding medium,
dzthe diameter of the outer surface of the pipe insulation layer,
αwthe coefficient of heat release of the outer surface of the pipe insulation to air.
According to a further improvement of the invention, the heat release coefficient alpha of the outer surface of the insulating layer of the hot water pipeline to the airwCalculated by the public (8) is:
wherein:
αwthe heat release coefficient of the outer surface of the pipe insulation layer to the air,
v-the flow velocity of air near the outer surface of the pipe insulation.
According to a further improvement of the invention, the thermal resistance R of the thermal insulation material for the hot water pipelinebCalculated by the public display (9):
wherein:
Rbthe thermal resistance of the pipeline heat-insulating material,
dzthe diameter of the outer surface of the pipe insulation layer,
dw-the outside diameter of the pipe,
λb-thermal conductivity of the pipe insulation material.
In a further improvement of the present invention, in the step S2, the heat loss rate P of the hot water tank is2Calculated by equation (10):
wherein:
P2-the heat dissipation loss rate of the hot water tank,
tz-the required temperature of the outlet water of the terminal,
tw2-the temperature of the environment outside the water tank,
αq2-the thermal resistivity of the other parts of the tank,
Rb2the thermal resistance of the heat-insulating material of the water tank,
Rw2thermal resistance from the outer surface of the insulating layer of the water tank to the surrounding medium.
According to a further improvement of the invention, the thermal resistance R from the outer surface of the insulating layer of the water tank to the surrounding medium iswCalculated by the public display (11):
wherein:
Rw2the thermal resistance from the outer surface of the insulating layer of the water tank to the surrounding medium,
Sw-the external surface area of the water tank,
αw2the coefficient of heat release of the outer surface of the tank insulation to the air.
According to a further improvement of the invention, the heat release coefficient alpha of the outer surface of the insulating layer of the hot water tank to the airw2Calculated by the public display (12):
wherein:
αw2the heat release coefficient of the outer surface of the heat insulation layer of the water tank to the air,
v2-the flow velocity of air near the outer surface of the vertical insulation.
According to a further improvement of the invention, the thermal resistance R of the thermal insulation material of the hot water tankb2Calculated by the public (13) is:
wherein:
Rb2the thermal resistance of the heat-insulating material of the water tank,
dw2the thickness of the heat-insulating layer of the water tank,
Sz-the heat dissipation area of the heat insulation layer of the water tank,
λb2-thermal conductivity of the insulation material.
In a further improvement of the present invention, in step S4,
when t iss1When the temperature is higher than the upper limit value of the outlet water temperature of the heat pump water heater, t iss1Equal to the upper limit value of the outlet water temperature of the heat pump water heater;
when t iss2When the temperature is higher than the upper limit value of the outlet water temperature of the heat pump water heater, t iss2Equal to the upper limit value of the outlet water temperature of the heat pump water heater;
when t iss1When the temperature is lower than the lower limit value of the outlet water temperature of the heat pump water heater, t iss1Equal to the lower limit value of the outlet water temperature of the heat pump water heater;
when t iss2When the temperature is lower than the lower limit value of the outlet water temperature of the heat pump water heater, t iss2Equal to the lower limit value of the outlet water temperature of the heat pump water heater.
In a further development of the invention, t iszAt initial state, the default setting value is set, and then tz= ts1。
The invention has the beneficial effects that:
the energy-saving control system and the control method thereof comprehensively estimate the influence of the heat loss of the system and the current water quantity and the current water temperature in the water tank, change the temperature control of the heat pump water heater from constant temperature control into dynamic control according to the change of field conditions, ensure that the outlet water temperature of the heat pump water heater is lower when the heat pump water heater works on the premise that the outlet water temperature of a terminal meets the requirements of users, obtain higher energy efficiency ratio and larger heating capacity on the premise of meeting the use requirements, simultaneously have low internal and external temperature difference when storing and conveying hot water, have smaller heat loss of a hot water system and save more energy for the system.
Drawings
FIG. 1 is a schematic structural view of the present invention
FIG. 2 is a schematic diagram of a control circuit according to the present invention
FIG. 3 is a table of experimental data of the present invention at a desired temperature of 45 degrees Celsius
FIG. 4 is a table of experimental data of the present invention at a required temperature of 50 degrees Celsius
FIG. 5 is a table of experimental data of the directly-heated heat pump water heater of the prior art at a required temperature of 45 degrees Celsius
Fig. 6 is a table of experimental data of the prior art direct-heating heat pump water heater under the condition that the required temperature is 45 degrees celsius.
Detailed Description
As can be seen from fig. 1 to 2, the energy-saving control system for the outlet water temperature of the direct-heating heat pump water heater comprises a heat pump water heater 1 for communicating and exchanging a clean water pipe and a waste water pipe, respectively, a hot water outlet pipe 2 of the heat pump water heater 1 is communicated with a water inlet of a hot water storage tank 3, a water outlet of the hot water storage tank 3 is communicated with water pipes in pipe wells 5 of water units through a hot water supply pipe 4, the water pipes in the pipe wells 5 are communicated with water using devices 6, the water pipes in the pipe wells 5 are communicated with a water return port of the hot water storage tank 3 through a hot water return pipe 7, an electric control valve 9 and a temperature sensor a12 for measuring the outlet water temperature of the heat pump are arranged on the hot water outlet pipe 2, the hot water storage tank 3 is provided with a temperature sensor B13 for measuring the temperature in the water tank, a liquid level sensor 14 for measuring the liquid level in the water tank and a temperature sensor C15 for measuring the ambient temperature around the water tank, the pipe shaft 5 is also internally provided with a temperature sensor D16 for measuring the environmental temperature of the pipe shaft 5, an industrial personal computer 17 and a temperature PID controller 18, the temperature sensor B13, the liquid level sensor 14, the temperature sensor C15 and the temperature sensor D16 are all electrically connected with the industrial personal computer 17, the temperature PID controller 18 is respectively electrically connected with the industrial personal computer 17, the temperature sensor A12 and the electric regulating valve 9, the industrial personal computer 17 calculates the set temperature signal according to the signals measured by the temperature sensor B13, the liquid level sensor 14, the temperature sensor C15 and the temperature sensor D16, the temperature PID controller performs PID control on the electric control valve 9 according to a set temperature value ts2 obtained by the industrial control computer 17 and a temperature value tc measured by the temperature sensor A12, the waste water pipe is communicated with a waste water pump 8, and the hot water supply pipe 4 is communicated with a water supply pump 10.
The hot water supply pipe 4 is also communicated with a sterilizer 11.
The method for performing energy-saving control on the outlet water temperature of the direct heat type heat pump water heater by using the control system comprises the following steps:
s1, calculating the heat loss of the hot water pipeline through the formula (1):
Q1= T1 P1/1000 （1）
wherein:
Q1the hot water pipe dissipates the heat energy,
T1-the total length of the hot water circulation of the pipeline,
P1-hot water pipe heat dissipation loss rate;
s2, calculating the heat loss of the water tank through a formula (2):
wherein:
Q2-the hot water tank dissipates heat,
T2the total heat dissipation time of the hot water tank is long,
P2-hot water tank heat dissipation loss rate;
s3, firstly, calculating to obtain a set value of the temperature of the hot water tank through a formula (3):
wherein:
ts1-a set value for the temperature of the water in the hot water tank,
tz-the temperature of the outlet water is required by the terminal,
H1the upper limit of the liquid level of the water tank during the hot water production,
Sj-the cross-sectional area of the inside of the water tank,
Q1the hot water pipe dissipates the heat energy,
Q2-the hot water tank dissipates heat;
and calculating to obtain a set value of the outlet water temperature of the heat pump water heater by a formula (4):
wherein:
ts2the outlet water temperature set value of the heat pump water heater,
ts1-a set value for the temperature of the water in the hot water tank,
tn0-the temperature of the water in the water tank,
H1the upper limit of the liquid level of the water tank during the hot water production,
h1-the tank level;
s4, the industrial control computer 17 will ts2The value is sent to the temperature PID controller 18, the temperature PID controller 18-cycle reading of the temperature value of the temperature sensor A12 and corresponding ts2Comparing the set values to obtain a difference value e, and according to the set KP proportional adjustment coefficient, the KI integral adjustment coefficient, the KD differential adjustment coefficient and the formula (5):
the value u is obtained after operation, and the opening degree of the valve is controlled and adjusted according to the characteristic output of the electric adjusting valve 9, so that the outlet water temperature of the heat pump water heater 1 reaches ts2And (5) setting the value.
In the step S1, the heat loss rate P of the hot water pipe1Calculated by equation (6):
wherein:
P1-the heat dissipation loss rate of the hot water pipeline,
tz-the required temperature of the outlet water of the terminal,
tw-the ambient temperature of the pipe well or the ambient temperature outside the pipe,
l is the length of the pipeline,
αq-the thermal resistivity of the rest of the pipe,
Rbthe thermal resistance of the pipeline heat-insulating material,
Rwthermal resistance from the outer surface of the pipe insulation layer to the surrounding medium.
Thermal resistance R from the outer surface of the heat-insulating layer of the hot water pipeline to the surrounding mediumwCalculated by the public (7) is:
wherein:
Rwthe thermal resistance from the outer surface of the pipeline insulating layer to the surrounding medium,
dzthe diameter of the outer surface of the pipe insulation layer,
αwthe coefficient of heat release of the outer surface of the pipe insulation to air.
The heat release coefficient alpha of the outer surface of the insulating layer of the hot water pipeline to the airwCalculated by the public (8) is:
wherein:
αwthe heat release coefficient of the outer surface of the pipe insulation layer to the air,
v-the flow velocity of air near the outer surface of the pipe insulation.
Thermal resistance R of the thermal insulation material of the hot water pipelinebCalculated by the public display (9):
wherein:
Rbthe thermal resistance of the pipeline heat-insulating material,
dzthe diameter of the outer surface of the pipe insulation layer,
dw-the outside diameter of the pipe,
λb-thermal conductivity of the pipe insulation material.
In the step S2, the heat loss rate P of the hot water tank2Calculated by equation (10):
wherein:
P2-the heat dissipation loss rate of the hot water tank,
tz-the required temperature of the outlet water of the terminal,
tw2-the temperature of the environment outside the water tank,
αq2-the thermal resistivity of the other parts of the tank,
Rb2the thermal resistance of the heat-insulating material of the water tank,
Rw2thermal resistance from the outer surface of the insulating layer of the water tank to the surrounding medium.
Thermal resistance R from the outer surface of the water tank heat-insulating layer to the surrounding mediumwCalculated by the public display (11):
wherein:
Rw2the thermal resistance from the outer surface of the insulating layer of the water tank to the surrounding medium,
Sw-the external surface area of the water tank,
αw2the coefficient of heat release of the outer surface of the tank insulation to the air.
The heat release coefficient alpha of the outer surface of the insulating layer of the hot water tank to the airw2Calculated by the public display (12):
wherein:
αw2the heat release coefficient of the outer surface of the heat insulation layer of the water tank to the air,
v2-the flow velocity of air near the outer surface of the vertical insulation.
Thermal resistance R of the thermal insulation material of the hot water tankb2Calculated by the public (13) is:
wherein:
Rb2the thermal resistance of the heat-insulating material of the water tank,
dw2the thickness of the heat-insulating layer of the water tank,
Sz-the heat dissipation area of the heat insulation layer of the water tank,
λb2-thermal conductivity of the insulation material.
In the step S4, in the above step,
when t iss1When the temperature is higher than the upper limit value of the outlet water temperature of the heat pump water heater, t iss1Equal to the upper limit value of the outlet water temperature of the heat pump water heater;
when t iss2When the temperature is higher than the upper limit value of the outlet water temperature of the heat pump water heater, t iss2Equal to the upper limit value of the outlet water temperature of the heat pump water heater;
when t iss1When the temperature is lower than the lower limit value of the outlet water temperature of the heat pump water heater, t iss1Equal to the lower limit value of the outlet water temperature of the heat pump water heater;
when t iss2When the temperature is lower than the lower limit value of the outlet water temperature of the heat pump water heater, t iss2Equal to the lower limit value of the outlet water temperature of the heat pump water heater.
Said t iszAt initial state, the default setting value is set, and then tz= ts1。
Taking an 11-storey 5-unit 110-family residential building as an example, the project uses 430 meters of PPR32 water return pipe, 330 meters of PPR63 water supply pipe, 100 meters of PPR90 water supply pipe, the pipes are all insulated by polyurethane, and the insulation thicknesses of the PPR32, PPR63 and PPR90 pipes are respectively: 19.7mm, 21.6mm, 32.6 mm. The average temperature of the piping well over 24 hours was 15 ℃. The pipeline hot water circulation time is 12 hours. The project water distribution box is a cuboid and made of stainless steel, the volume is 15m, the length, the width and the height of the inner wall are respectively 3m, 2m and 2.5m, the heat preservation layer is made of polyurethane, and the thickness of the heat preservation layer is 0.05 m. The ambient temperature outside the tank averaged 15 ℃ over the last 24 hours. The upper limit of the liquid level of the water tank is 2.35m when the hot water is produced. The terminal required outlet water temperature is 40 ℃.
The calculation result is as follows: three kinds of pipelinesHeat loss and heat loss measuring device
=231777 kJ, heat loss from water tank
=41790 kilojoules. When the temperature t of the water in the water tankn0The reading value of (d) is 44 ℃, the liquid level h of the water tank1Is 1.2m, at which time the hot water tank water temperature set point ts1=44.6 ℃, and the outlet water temperature set value t of the heat pump water heaters2=45.7℃。
In a system for collecting heat and supplying hot water (such as a hotel, a residential district and a student dormitory), in spring and autumn when the environmental temperature is about 15 ℃, the water temperature of a heat pump water heater for constant temperature water outlet is usually set to be more than 50 ℃, and a user needs to add a certain amount of cold water for use.
The water outlet temperature of the heat pump water heater or the water temperature of the water tank is reduced by 5 ℃, and the heat loss can be reduced by about 16% when the system operates.
Meanwhile, the outlet water temperature of the heat pump water heater is reduced, and the heat pump unit can obtain higher energy efficiency ratio, larger heating capacity and more energy conservation. The waste heat cascade utilization water source heat pump water heater is used for verification, and performance tests of the outlet water temperature of 45 ℃ and the outlet water temperature of 50 ℃ are respectively carried out under the condition that other working conditions are the same, and the results are shown in fig. 3 and 4; and a common water source heat pump water heater is used for verification, and performance tests of the water outlet temperature of 45 ℃ and the water outlet temperature of 50 ℃ are respectively carried out under the condition that the conditions of other working conditions are the same, and the results are shown in fig. 5 and 6.
According to the test results, the following results are obtained:
1. the waste heat cascade utilization water source heat pump water heater (5P unit) has the heating capacity of 28.247kw, the input power of 3.785kw and the COP value of 7.464 at the temperature of 45 ℃; at 50 ℃, the heating capacity is 27.665kw, the input power is 4.11kw, and the COP value is 6.731. Compared with 50 ℃ at 45 ℃, the heating capacity is improved by 2%, the energy consumption is reduced by 7.9%, and the COP value is improved by 10.9%.
2. The normal water source heat pump water heater (10P unit) has the heating capacity of 34.961kw, the input power of 7.972kw and the COP value of 4.386 at the temperature of 45 ℃; at 50 ℃, the heating capacity is 31.651kw, the input power is 8.248kw, the COP value is 3.837, and compared with 50 ℃, the heating capacity is improved by 10.5%, the energy consumption is reduced by 3.3%, and the COP value is improved by 14.3%.
If a circulating heating type heat pump water heater is used, the industrial control computer 17 directly sends t tos1The value is sent to a temperature controller, and the temperature controller reads the temperature value of the water temperature sensor in the hot water tank in a circulating way until the water temperature in the hot water tank reaches ts1And setting a value, and sending a signal by the temperature controller to control the heat pump water heater to stop running.
In this embodiment, a water source heat pump is used, and an air source heat pump is also applicable to the present application.
Claims (10)
1. The energy-saving control system of the outlet water temperature of the directly-heated heat pump water heater is characterized in that: comprises a heat pump water heater (1) for communicating a clear water pipe for heat exchange, wherein a hot water outlet pipe (2) of the heat pump water heater (1) is communicated with a water inlet of a hot water storage tank (3), a water outlet of the hot water storage tank (3) is respectively communicated with water pipes in pipe wells (5) of all water using units through a hot water supply pipe (4), the water pipes in the pipe wells (5) are respectively communicated with all water using devices (6), the water pipes in the pipe wells (5) are communicated with a water return port of the hot water storage tank (3) through a hot water return pipe (7), an electric regulating valve (9) and a temperature sensor A (12) for measuring the outlet water temperature of a heat pump are respectively arranged on the hot water outlet pipe (2), the hot water storage tank (3) is provided with a temperature sensor B (13) for measuring the temperature in the water tank, a liquid level sensor (14) for measuring the liquid level in the water tank and a temperature sensor C (15) for measuring the ambient temperature around the water tank, still be equipped with temperature sensor D (16) of measuring piping shaft (5) ambient temperature in piping shaft (5), still include industrial control computer (17) and temperature PID controller (18), temperature sensor B (13), level sensor (14), temperature sensor C (15) and temperature sensor D (16) all with industrial controlThe computer (17) is electrically connected, the temperature PID controller (18) is respectively electrically connected with the industrial personal computer (17), the temperature sensor A (12) and the electric regulating valve (9), the industrial personal computer (17) calculates a set temperature signal according to signals measured by the temperature sensor B (13), the liquid level sensor (14), the temperature sensor C (15) and the temperature sensor D (16), and the temperature PID controller obtains a set temperature value t according to the set temperature value t obtained by the industrial personal computer (17)s2And the temperature value t measured by the temperature sensor A (12)cPID control is carried out on the electric regulating valve (9), and a water supply pump (10) is communicated with the hot water supply pipe (4).
2. A method for energy efficient control of the outlet water temperature of a direct heat pump water heater using a control system according to claim 1, comprising the steps of:
s1, calculating the heat loss of the hot water pipeline through the formula (1):
Q1= T1 P1/1000 （1）
wherein:
Q1the hot water pipe dissipates the heat energy,
T1-the total length of the hot water circulation of the pipeline,
P1-hot water pipe heat dissipation loss rate;
s2, calculating the heat loss of the water tank through a formula (2):
wherein:
Q2-the hot water tank dissipates heat,
T2the total heat dissipation time of the hot water tank is long,
P2-hot water tank heat dissipation loss rate;
s3, firstly, calculating to obtain a set value of the temperature of the hot water tank through a formula (3):
wherein:
ts1-a set value for the temperature of the water in the hot water tank,
tz-the temperature of the outlet water is required by the terminal,
H1the upper limit of the liquid level of the water tank during the hot water production,
Sj-the cross-sectional area of the inside of the water tank,
Q1the hot water pipe dissipates the heat energy,
Q2-the hot water tank dissipates heat;
and calculating to obtain a set value of the outlet water temperature of the heat pump water heater by a formula (4):
wherein:
ts2the outlet water temperature set value of the heat pump water heater,
ts1-a set value for the temperature of the water in the hot water tank,
tn0-the temperature of the water in the water tank,
H1the upper limit of the liquid level of the water tank during the hot water production,
h1-the tank level;
s4, the industrial control computer (17) sends ts2The value is sent to a temperature PID controller (18), and the temperature PID controller (18) reads the temperature value of the temperature sensor A (12) in a circulating way and corresponds to ts2Comparing the set values to obtain a difference value e, and according to the set KP proportional adjustment coefficient, the KI integral adjustment coefficient, the KD differential adjustment coefficient and the formula (5):
the u value is obtained after operation, and the opening degree of the valve is controlled and adjusted according to the characteristic output of the electric adjusting valve (9), so that the outlet water temperature of the heat pump water heater (1) reaches ts2And (5) setting the value.
3. The energy-saving control method for outlet water temperature of the directly-heated heat pump water heater as claimed in claim 2, characterized in that:
in the step S1, the heat loss rate P of the hot water pipe1Calculated by equation (6):
wherein:
P1-the heat dissipation loss rate of the hot water pipeline,
tz-the required temperature of the outlet water of the terminal,
tw-the ambient temperature of the pipe well or the ambient temperature outside the pipe,
l is the length of the pipeline,
αq-the thermal resistivity of the rest of the pipe,
Rbthe thermal resistance of the pipeline heat-insulating material,
Rwthermal resistance from the outer surface of the pipe insulation layer to the surrounding medium.
4. The energy-saving control method for outlet water temperature of the directly-heated heat pump water heater as claimed in claim 3, characterized in that:
thermal resistance R from the outer surface of the heat-insulating layer of the hot water pipeline to the surrounding mediumwCalculated by the public (7) is:
wherein:
Rwthe thermal resistance from the outer surface of the pipeline insulating layer to the surrounding medium,
dzthe diameter of the outer surface of the pipe insulation layer,
αwthe coefficient of heat release of the outer surface of the pipe insulation to the air;
the heat release coefficient alpha of the outer surface of the insulating layer of the hot water pipeline to the airwCalculated by the public (8) is:
wherein:
αwthe heat release coefficient of the outer surface of the pipe insulation layer to the air,
v-the flow velocity of air near the outer surface of the pipe insulation.
5. The energy-saving control method for outlet water temperature of the directly-heated heat pump water heater as claimed in claim 3, characterized in that:
thermal resistance R of the thermal insulation material of the hot water pipelinebCalculated by the public display (9):
wherein:
Rbthe thermal resistance of the pipeline heat-insulating material,
dzthe diameter of the outer surface of the pipe insulation layer,
dw-the outside diameter of the pipe,
λb-thermal conductivity of the pipe insulation material.
6. The energy-saving control method for outlet water temperature of the directly-heated heat pump water heater as claimed in claim 2, characterized in that:
in the step S2, the heat loss rate P of the hot water tank2Calculated by equation (10):
wherein:
P2-the heat dissipation loss rate of the hot water tank,
tz-the required temperature of the outlet water of the terminal,
tw2-the temperature of the environment outside the water tank,
αq2-the thermal resistivity of the other parts of the tank,
Rb2the thermal resistance of the heat-insulating material of the water tank,
Rw2thermal resistance from the outer surface of the insulating layer of the water tank to the surrounding medium.
7. The energy-saving control method for outlet water temperature of the directly-heated heat pump water heater as claimed in claim 6, characterized in that:
thermal resistance R from the outer surface of the water tank heat-insulating layer to the surrounding mediumwCalculated by the public display (11):
wherein:
Rw2the thermal resistance from the outer surface of the insulating layer of the water tank to the surrounding medium,
Sw-the external surface area of the water tank,
αw2the heat release coefficient of the outer surface of the insulating layer of the water tank to the air;
the hot water tank protectorCoefficient of heat release alpha of outer surface of warm layer to airw2Calculated by the public display (12):
wherein:
αw2the heat release coefficient of the outer surface of the heat insulation layer of the water tank to the air,
v2-the flow velocity of air near the outer surface of the vertical insulation.
8. The energy-saving control method for outlet water temperature of the directly-heated heat pump water heater as claimed in claim 6, characterized in that:
thermal resistance R of the thermal insulation material of the hot water tankb2Calculated by the public (13) is:
wherein:
Rb2the thermal resistance of the heat-insulating material of the water tank,
dw2the thickness of the heat-insulating layer of the water tank,
Sz-the heat dissipation area of the heat insulation layer of the water tank,
λb2-thermal conductivity of the insulation material.
9. The energy-saving control method for outlet water temperature of the directly-heated heat pump water heater as claimed in claim 2, characterized in that:
in the step S4, in the above step,
when t iss1When the temperature is higher than the upper limit value of the outlet water temperature of the heat pump water heater, t iss1Equal to the upper limit value of the outlet water temperature of the heat pump water heater;
when t iss2When the temperature is higher than the upper limit value of the outlet water temperature of the heat pump water heater, t iss2Equal to the upper limit value of the outlet water temperature of the heat pump water heater;
when t iss1When the temperature is lower than the lower limit value of the outlet water temperature of the heat pump water heater, t iss1Equal to the lower limit value of the outlet water temperature of the heat pump water heater;
when t iss2When the temperature is lower than the lower limit value of the outlet water temperature of the heat pump water heater, t iss2Equal to the lower limit value of the outlet water temperature of the heat pump water heater.
10. The energy-saving control method for the outlet water temperature of the directly-heated heat pump water heater as claimed in any one of claims 2 to 9, characterized in that: said t iszAt initial state, the default setting value is set, and then tz= ts1。
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