CN111723533B - Energy-saving calculation method for variable-frequency water pump of ground source heat pump system - Google Patents
Energy-saving calculation method for variable-frequency water pump of ground source heat pump system Download PDFInfo
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- 238000005265 energy consumption Methods 0.000 claims abstract description 78
- 238000013461 design Methods 0.000 claims abstract description 19
- 230000001932 seasonal effect Effects 0.000 claims abstract description 18
- 238000001816 cooling Methods 0.000 claims abstract description 9
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- 239000002689 soil Substances 0.000 claims description 17
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- 238000005057 refrigeration Methods 0.000 claims description 5
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- 238000004378 air conditioning Methods 0.000 description 5
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- G06F30/28—Design optimisation, verification or simulation using fluid dynamics, e.g. using Navier-Stokes equations or computational fluid dynamics [CFD]
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
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Abstract
The invention relates to a variable frequency water pump energy-saving calculation method of a ground source heat pump system, which comprises the following steps: step 1: simulating the annual dynamic cold and hot loads of a building by establishing a load model of a typical building, and dividing the dynamic loads in the cooling and heating seasons according to different load rate intervals; step 2: calculating the energy consumption of the corresponding water pump and the host machine set under the dynamic load according to different ground source side water pump operation modes; and 3, step 3: overlapping the energy consumption under each load rate to obtain the seasonal total energy consumption; and 4, step 4: and obtaining the optimal energy-saving design mode by comparing the seasonal total energy consumption under different source side water pump operation modes. The invention has the following effects: on the basis of annual hourly load calculation which is commonly used in the current engineering design, an equipment model is established, the energy consumption of a main machine and a water pump is calculated and predicted through a simple formula, the energy-saving effect of variable flow is analyzed, the operation is simple and easy, and the data are accurate.
Description
Technical Field
The invention relates to the technical field of ground source heat pumps, in particular to an energy-saving calculation method for a variable-frequency water pump of a ground source heat pump system.
Background
The ground source heat pump system exchanges heat with shallow soil through the buried pipe heat exchanger, extracts or releases heat from the surrounding soil, and realizes building refrigeration and heating. Because the soil temperature is basically constant at about the annual average temperature, the ground source heat pump unit has higher coefficient of performance by utilizing the heat exchanger of the ground pipe to exchange heat with the soil. Ground source heat pump systems have been widely used in China, and have also been implemented in cooling and heating energy source station projects in partial areas in recent years.
In general, in an air conditioning system, the installed power of a circulating water pump is obviously lower than that of a refrigeration main machine, but in actual use, the annual energy consumption proportion of the water pump is higher. According to an ASHRAE investigation, the energy consumption of a water pump of a conventional air-conditioning system accounts for 15% -48% of the total energy consumption (including the energy consumption of a host and the energy consumption of the water pump) of the system. In a special research on a ground source heat pump system, the energy consumption of a water pump accounts for 45 percent of the total energy consumption of the system; in another research on the centralized ground source heat pump system, the annual energy consumption of the water pump is 32% -130% of that of the heat pump host. Compared with a conventional air conditioning system, the ground source side pipeline of the ground source heat pump system, namely the ground heat exchanger and the connecting pipe pipeline, is long in pipe pass, large in flow resistance and large in power of the circulating water pump. Therefore, the operation control of the water pump has a great influence on the total energy consumption of the centralized ground source heat pump system.
The cooling and heating requirements of buildings have the characteristic of changing from time to time, and the air conditioning system operates under partial load most of the year. In a conventional centralized air-conditioning system, the variable-flow operation of a circulating pump of a chilled water system on the user side is a common energy-saving means, but there are still some disputes and different viewpoints about the variable-flow problem of a cooling water system on the source side. For the ground source heat pump system, the relevant specifications clearly provide that the circulating water system at the ground source side is suitable for adopting the variable flow design. However, the specifications do not specifically specify or suggest implementation details of the variable flow rate mode, the operation strategy and the like.
The energy-conservation of water pump can be realized in the variable flow operation, can bring adverse effect to other parts in the ground source heat pump system simultaneously: the flow rate of the ground heat exchanger is reduced due to the reduction of the circulating flow, so that the heat exchange quantity of the ground heat exchanger can be reduced; the reduced flow on the ground source side changes the inlet temperature of the heat pump main engine, and reduces the energy efficiency of the main engine. Therefore, the variable flow technology of the ground source side water system is complex, and the performances of the water pump, the ground heat exchanger and the heat pump host need to be considered integrally.
For the ground source side water circulation variable flow technology of the ground source heat pump system, some researches have been carried out and some calculation methods have been proposed, for example: a calculation method based on load BIN statistical data; for another example, the TRNSYS software is adopted to simulate and calculate the time-by-time system energy consumption. These existing calculation methods either use complex algorithms for coupling simulations of the whole system or use rough models that only consider a single device. The overall coupling simulation method is too complicated to use in engineering; the rough model error considering only a single equipment water pump is large.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an energy-saving calculation method for a variable-frequency water pump of a ground source heat pump system.
The above object of the present invention is achieved by the following technical solutions: a method for calculating energy conservation of a variable frequency water pump of a ground source heat pump system comprises the following steps:
step 1: simulating the annual dynamic cold and hot loads of a building by establishing a load model of a typical building, and dividing the dynamic loads in the cooling and heating seasons according to different load rate intervals;
step 2: calculating the energy consumption of the corresponding water pump and the host machine set under the dynamic load according to different ground source side water pump operation modes;
and step 3: overlapping the energy consumption under each load rate to obtain the seasonal total energy consumption;
and 4, step 4: obtaining an optimal energy-saving design mode by comparing the seasonal total energy consumption under different source side water pump operation modes;
wherein the seasonal total energy consumption calculation formula of the step 3 is as follows:
in the formula: n is a radical of General (1) Total energy consumption in system seasons; n is a radical of hydrogen Host computer i The energy consumption of the host when the load rate is i; n is a radical of Water pump i The energy consumption of the water pump is when the load factor is i; t is i The time length when the load factor is i.
The present invention in a preferred example may be further configured to: the operation mode of the ground source side water pump in the step 4 comprises two operation modes of a fixed-frequency water pump and a variable-frequency water pump, and the seasonal total energy consumption is the sum of the operation energy consumption of the heat pump main unit corresponding to different load rate intervals plus the sum of the smaller value of the energy consumption of the variable-frequency water pump in the different load rate intervals and the energy consumption of the fixed-frequency water pump.
By adopting the technical scheme, the performances of the buried pipe, the water pump and the host under dynamic load and variable flow are comprehensively considered, the seasonal energy can be accurately analyzed, and a basis can be provided for selecting the variable flow energy-saving design scheme of the ground source side circulating water pump.
The invention in a preferred example may be further configured to: the calculation formula of the heat pump host operation energy consumption P with different flow rates under different load rates is as follows:
④CAPFT＝a 1 +b 1 T cw，l +C 1 T cw，l 2 +d 1 T cond，e +e 1 T cond，e 2 +f 1 T cw，l T cond，e
⑤EIRFT＝a 2 +b 2 T cw，I +c 2 T cw，l 2 +d 2 T cond，e +e 2 T cond，e 2 +f 2 T cw，l T cond，e
⑥EIRFPLR＝a 3 +b 3 PLR+c 3 PLR 2
⑦PLR＝Q/(Q ref CAPFT)
⑧P＝P ref ×CAPFT×EIRFT×EIRFPLR
in the formula: CAPFT is a refrigeration capacity coefficient influenced by temperature; t is a unit of cw.l Is the chilled water outlet temperature; t is cond.e Is the cooling water inlet temperature; EIRFT is the energy consumption-to-cooling ratio influenced by temperature; EIRFPLR is the energy consumption-to-cold ratio under partial load rate; a, b, c, d, e and f are regression coefficients; PLR is part load rate; q ref Designing cold quantity for the host; p ref Energy consumption is designed for the host.
By adopting the technical scheme, the host performance is predicted by adopting a cold machine model. In this model, the host power consumption and COP are mainly determined by the inlet water temperature on the cold and hot source side and the Partial Load Ratio (PLR). The model fits with the performance data given by the host sample to obtain the relevant parameters according to the three polynomial curves under the variable working condition. And calculating the performance of the main engine under the actual operation condition by using the three polynomials, and obtaining the performance coefficients under different temperatures and partial load rates by combining the calculation mode in the step (c), thereby calculating the energy consumption of the unit.
The invention in a preferred example may be further configured to: cooling water inlet temperature T of different flow under different load rates cond.e The calculation formula of (a) is as follows:
①R＝Q ref /(T f，mean，ref -T soil)
②T f，mean ＝Q real /R+T soil
③T out ＝T f，mean -0.5Q real /m real C
in the formula: r is total heat transfer resistance of the buried pipe; q ref The heat dissipation capacity of the buried pipe under the design working condition is improved; t is f.mean.ref Average water temperature of an inlet and an outlet of a buried pipe under a design working condition; t is soil Is the soil temperature; t is f.mean The average water temperature of the outlet of the buried pipe under the operating condition is adopted; q real The heat dissipation capacity of the buried pipe under the operation condition is ensured; t is out The water temperature at the outlet of the buried pipe under the operating condition; m is real The flow rate is measured by the buried pipe under the operating condition; c is specific heat of water and inlet temperature T of cooling water cond.e The temperature T of water at the outlet of the buried pipe under the working condition of operation out Are equal.
By adopting the technical scheme, when the host computer consumes time, the temperature of the ground source side inlet of the host computer, namely the temperature of the outlet of the buried pipe, needs to be determined. Calculating the temperature of the outlet of the buried pipe through a heat transfer model of the heat exchanger of the buried pipe; the calculation process is as follows: 1) under the design condition, calculating the total thermal resistance of the buried pipe under the full-load rate and full-flow according to the average water temperature of an inlet and an outlet of the buried pipe; 2) assuming that the heat resistance of the buried pipe is irrelevant to the flow, calculating the heat transfer temperature difference under the partial load rate according to the total heat resistance of the buried pipe in the step 1; 3) under the working condition of variable flow, obtaining a circulating temperature difference according to the load rate; 4) the outlet temperature of the buried pipe is obtained by the heat transfer temperature difference and the circulation temperature difference, and then the outlet temperature of the buried pipe can be calculated by combining the formula.
The invention in a preferred example may be further configured to: the total energy consumption of the variable-frequency water pump with different flow rates under different load rates is the total efficiency of the variable-frequency water pump multiplied by the effective power multiplied by the running time, the effective power is the product of the flow rate and the lift of the variable-frequency water pump, and the specific calculation formula is as follows:
⑨η＝η vfd *η m *η p
⑩η vfd ＝50.87+1.283*X-0.0142*X^2+5.842*10^(-5)*X^3
in the formula: eta is the total efficiency (%) of the variable-frequency water pump; eta vfd Is the frequency converter efficiency (%); eta m Motor efficiency (%); eta p Water pump efficiency (%); x is the relative number (%) of revolutions of the motor.
The present invention in a preferred example may be further configured to: the total energy consumption of the fixed-frequency water pumps with different flow rates under different load rates is the product of the power of the fixed-frequency water pumps and the running time.
By adopting the technical scheme, under the control of the number of the fixed-frequency water pumps, the energy consumption is calculated according to the power and the operation hours of the fixed-frequency pumps. For the variable-frequency water pump, the variable-frequency efficiency is considered, namely the efficiency changes of the frequency converter, the motor and the water pump under different frequencies are considered, and the running energy consumption of the water pump is calculated by combining the effective power (namely the product of the flow and the lift) and the running hours.
In conclusion, the invention has the following beneficial technical effects: the performances of the buried pipe, the water pump and the host under dynamic load and variable flow are comprehensively considered, the seasonal energy can be accurately analyzed, and a basis can be provided for selecting an energy-saving design scheme of variable flow of the ground source side circulating water pump.
Drawings
Fig. 1 is a schematic diagram of a ground source heat pump energy station system in an embodiment of the invention.
FIG. 2 is a decoupling implementation flow of a method for predicting the energy saving rate of a variable-frequency water pump of a ground source heat pump system.
FIG. 3 shows the power of the water pump adjusted by the number of fixed frequency and variable frequency units under the Partial Load Ratio (PLR) in the embodiment of the invention.
FIG. 4 is a host energy efficiency ratio EER at Partial Load Rate (PLR) according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
Referring to fig. 1, the invention discloses a method for calculating energy conservation of a variable frequency water pump of a ground source heat pump system, which comprises the following steps:
step 1: the method is characterized in that the annual dynamic cold and hot loads of a typical building are simulated by establishing a load model of the typical building, and the dynamic loads in the cooling and heating seasons are divided according to different load rate intervals.
Step 2: according to different operation strategies of the ground source side water pump, such as: and adjusting the number of fixed frequency stations and the number of variable frequency stations, and calculating the corresponding buried pipe performance under the dynamic load and the energy consumption of a water pump and a host by using an equipment model.
Under the control of the number of the fixed-frequency water pumps, the total energy consumption of the fixed-frequency water pumps with different flow rates under different load rates is the product of the power of the fixed-frequency water pumps and the running time. To the frequency conversion water pump, consider frequency conversion efficiency, converter, motor and the efficiency change of water pump under the different frequencies promptly, the total efficiency of frequency conversion water pump as follows: ninthly eta ═ eta vfd *η m *η p
In the formula, eta represents the total efficiency (%) of the variable-frequency water pump; eta vfd -frequency converter efficiency (%); eta m -motor efficiency (%); eta p -water pump efficiency (%).
Typical electric machine eta vfd Eta of m And the calculation is as follows:
⑩η vfd ＝50.87+1.283*X-0.0142*X^2+5.842*10^(-5)*X^3
in the formula, the relative revolution (%) of the X-motor, and the frequency conversion/power frequency.
Efficiency η of water pump p And obtaining the actual performance curve of the water pump. For the variable-frequency water pump, the total efficiency is obtained according to the formula, and then the total efficiency is multiplied by the effective power (namely the product of the flow and the lift) and the operation hour to calculate the operation energy consumption of the water pump.
And the host performance prediction is calculated by adopting a cold machine model. In this model, the host power consumption and COP are mainly determined by the inlet water temperature on the cold and hot source side and the Partial Load Ratio (PLR). The model fits 3 polynomial curves under variable working conditions according to performance data given by a host sample to obtain related parameters. Using these 3 polynomials, the host performance under actual operating conditions is calculated. The 3 polynomials are as follows:
④CAPFT＝a 1 +b 1 T cw，l +C 1 Tc w，l 2 +d 1 T cond，e +e 1 T cond，e 2 +f 1 T cw，l T cond，e
⑤EIRFT＝a 2 +b 2 T cw，l +c 2 T cw，l 2 +d 2 T cond，e +e 2 T cond，e 2 +f 2 T cw，l T cond，e
⑥EIRFPLR＝a 3 +b 3 PLR+c 3 PLR 2
in the formula, CAPFT represents the refrigeration capacity coefficient affected by temperature;
T cw . l -chilled water outlet temperature (° c);
T condd . e -cooling water inlet temperature (° c);
EIRFT-ratio of energy consumption to cold energy affected by temperature;
EIRFPLR-energy consumption and cold quantity ratio under partial load rate;
a, b, c, d, e, f-regression coefficients.
Wherein (PLR) Q/(Q) ref CAPFT)
In the formula, Q ref For the unit design (data plate) cold volume (kW).
According to the regression curve, the performance coefficients under different temperatures and partial load rates can be obtained, and further the unit energy consumption can be calculated as follows: (viii) plectrum P ═ Pref × CAPFT × EIRFT × EIRFPLR
In the formula, Pref is the unit design (nameplate) energy consumption (kW).
When the host computer is in time consumption, the temperature of the ground source side inlet of the host computer, namely the temperature of the outlet of the buried pipe, needs to be determined. Calculating the temperature of the outlet of the buried pipe through a heat transfer model of the heat exchanger of the buried pipe; the calculation process is as follows: 1) under the design condition, calculating the total thermal resistance of the buried pipe under the full-load rate and full-flow according to the average water temperature of an inlet and an outlet of the buried pipe; 2) assuming that the heat resistance of the buried pipe is irrelevant to the flow, calculating the heat transfer temperature difference under partial load rate according to the total heat resistance of the buried pipe in the step 1; 3) under the working condition of variable flow, obtaining a circulating temperature difference according to the load rate; 4) and obtaining the outlet temperature of the buried pipe by the heat transfer temperature difference and the circulation temperature difference.
The total heat transfer resistance of the buried pipe, namely the heat resistance between circulating water in the buried pipe and soil, comprises 4 parts: the heat resistance of the circulating water and the inner wall of the buried pipe by convective heat transfer, the heat resistance of the pipe wall from the inner wall of the buried pipe to the outer wall of the buried pipe, the heat resistance of the outer wall of the buried pipe in the hole of the drill hole and the heat resistance of the heat transfer outside the hole of the buried pipe. The variable flow working condition only affects the first part of the convective heat transfer thermal resistance, the proportion of the convective heat transfer thermal resistance in the total thermal resistance is very small, the variable flow influence can be approximately ignored, and the thermal resistance is assumed to be unchanged. The total heat transfer resistance of the buried pipe is calculated as follows:
①R＝Q ref /(T f，mean，ref -T soil )(kW)
in the formula, R is total heat transfer resistance of the buried pipe; q ref In order to dissipate heat of the buried pipe under the design working condition, the subscript ref represents the design working condition; t is f . mean . ref The average water temperature of the inlet and the outlet of the buried pipe under the design working condition is the average temperature T of the inlet and the outlet of the condenser f.mean.ref ＝(T in.ref +T out.ref )/2；T soil Is the soil temperature.
②T f，mean ＝Q real /R+T soil
In the formula, Q real The subscript real represents the operating condition for the heat dissipation capacity of the buried pipe under the operating condition; t is f.mean The average water temperature of the outlet of the buried pipe under the operating condition is adopted.
The temperature of the water at the outlet of the buried pipe under the operating condition, namely T of the heat pump main machine cond.e The cooling water inlet temperature is as follows:
③T out ＝T f，mean -0.5Q real /m real C
in the formula, m real The flow rate is measured by the buried pipe under the operation condition; c is the specific heat of water; t is f.mean Is the average water temperature of the inlet and the outlet of the buried pipe under the operating condition.
And step 3: and overlapping the energy consumption corresponding to each load rate interval to obtain the seasonal total energy consumption.
And 4, step 4: the seasonal total energy consumption is the sum of the running energy consumption of the heat pump main unit corresponding to different load rate intervals and the sum of the smaller value of the energy consumption of the variable-frequency water pump and the energy consumption of the fixed-frequency water pump in different load rate intervals, and the optimal energy-saving design mode is obtained by comparing the seasonal total energy consumption of the fixed-frequency water pump and the variable-frequency water pump on the ground source side in two running modes.
Specifically, the above calculation method is used to predict the system energy consumption for an engineering example, and the decoupling calculation process is shown in fig. 2. Fig. 2 shows a decoupling calculation process of the variable frequency water pump energy saving rate prediction method of the ground source heat pump system: and the energy consumption of the unit and the energy consumption of the water pump are calculated separately. Meanwhile, under different load rates, the energy consumption change of the main engine caused by the water temperature change of the buried pipe under the variable flow rate is considered.
The main process is as follows:
step 1: the method comprises the steps of simulating annual dynamic cold and hot loads of a building by establishing a load model of a typical building, and dividing the dynamic loads in cooling and heating seasons according to a load rate DEST.
And (3) adopting Dest software to model a typical building, and calculating the time-by-time building cold and heat load by adopting a typical meteorological year. According to the simulation results, the summer time-by-time load simulation results are shown in table 1.
TABLE 1 summer load factor distribution
| Load rate | Duration (h) | Ratio of the |
| 0～10％ | 96 | 7％ |
| 10～20％ | 79 | 6％ |
| 20～30％ | 107 | 8％ |
| 30～40％ | 174 | 13％ |
| 40～50％ | 257 | 19％ |
| 50～60％ | 206 | 15％ |
| 60～70％ | 186 | 14％ |
| 70～80％ | 153 | 11％ |
| 80～90％ | 84 | 6％ |
| 90～100％ | 24 | 2％ |
| Total of | 1366 | 100％ |
Step 2: two ground source side water pump operation strategies are selected: and adjusting the number of fixed frequency stations and the number of variable frequency stations, and calculating the performance of the buried pipe under the dynamic load and the energy consumption of a water pump and a host according to the equipment model.
When the regional building load changes, the cooling water flow and the cooling water temperature change along with the change, the condensation temperature of the heat pump unit is directly influenced, and the energy efficiency ratio of the heat pump unit is changed. In order to reasonably predict the energy consumption change of the host caused by the change of the cooling water flow, the actual host sample data is fitted to respectively obtain 3 individual performance curves of the host. The host energy consumption calculation process under different load rates is as follows: 1) in table 1, the temperature difference between the inlet and outlet of the cooling water is maintained at 5 ℃ under different load factors, the corresponding flow is calculated, and the flow of the cooling water is not lower than 50% of the designed flow under the variable flow working condition. 2) And calculating the outlet temperature of the buried pipe, namely the inlet water temperature of the condenser according to the buried pipe heat transfer model. 3) Obtaining the host power under the corresponding load rate according to the side flow of the host condenser and the water temperature at the inlet of the condenser, and obtaining the host energy consumption corresponding to the load rate by multiplying the host power by the accumulated duration of the load rate.
Fig. 3 shows the energy consumption of the water pump at Part Load Rate (PLR). The example system comprises two water pumps with the same model, and when the load rate of the system is in a range of 50-100%, the two cooling water pumps run at fixed frequency or variable frequency; when the load factor of the system is between 0 and 50 percent, one cooling water pump operates in a fixed frequency or variable frequency mode.
Fig. 4 shows the host energy efficiency ratio EER at Part Load Rate (PLR). The example system comprises two ground source heat pump hosts of the same type, and when the load rate of the system is within a range of 50-100%, the two hosts run simultaneously; when the load factor of the system is between 0% and 50%, one host operates.
And step 3: and overlapping the energy consumption under each load rate to obtain the seasonal total energy consumption.
Table 2 shows the comparison of water pump, main unit and total energy consumption for different operation modes. In the table, the energy saving rate is based on the fixed frequency number adjustment, and the relative energy saving rate of the variable frequency number adjustment is 11.1%.
TABLE 2 comparison of summer energy consumption for different control modes
In summary, the invention provides a simplified calculation method for predicting the energy-saving potential of the variable flow. The method comprehensively considers three key equipment performances of the system: the variable-frequency efficiency of the water pump, the variable-flow performance of the main engine and the heat transfer performance of the buried pipe radiator. The method is used for accurately analyzing the seasonal energy of the ground source heat pump system of the regional ground source heat pump energy station, and provides a basis for designing the scheme selection of the variable flow rate.
The embodiments of the present invention are preferred embodiments of the present invention, and the scope of the present invention is not limited by these embodiments, so: all equivalent changes made according to the structure, shape and principle of the invention are covered by the protection scope of the invention.
Claims (3)
1. A method for calculating energy conservation of a variable frequency water pump of a ground source heat pump system is characterized by comprising the following steps:
step 1: simulating the annual dynamic cold and hot loads of a building by establishing a load model of a typical building, and dividing the dynamic loads in the cooling and heating seasons according to different load rate intervals;
and 2, step: calculating the energy consumption of the corresponding water pump and the host machine set under the dynamic load according to different ground source side water pump operation modes;
and step 3: overlapping the energy consumption under each load rate to obtain the seasonal total energy consumption;
and 4, step 4: obtaining an optimal energy-saving design mode by comparing the seasonal total energy consumption under different source side water pump operation modes;
wherein the seasonal total energy consumption calculation formula of the step 3 is as follows:
in the formula: n is a radical of General assembly The system is seasonal total energy consumption; n is a radical of Host computer i The energy consumption of the host when the load rate is i; n is a radical of Water pump i The energy consumption of the water pump is when the load factor is i; t is i The time length when the load factor is i;
the calculation formula of the heat pump main engine operation energy consumption P with different flow rates under different load rates is as follows:
④CAPFT＝a 1 +b 1 T cw，l +c 1 T cw，l 2 +d 1 T cond，e +e 1 T cond，e 2 +f 1 T cw，l T cond，e
⑤EIRFT＝a 2 +b 2 T cw，l +c 2 T cw，l 2 +d 2 T cond，e +e 2 T cond，e 2 +f 2 T cw，l T cond，e
⑥EIRFPLR＝a 3 +b 3 PLR+c 3 PLR 2
⑦PLR＝Q/(Q ref CAPFT)
⑧P＝P ref ×CAPFT×EIRFT×EIRFPLR
in the formula: CAPFT is a refrigeration capacity coefficient influenced by temperature; t is cw.l Is the chilled water outlet temperature; t is cond.e Is the cooling water inlet temperature; the EIRFT is the energy consumption and cooling capacity ratio influenced by temperature; EIRFPLR is partial load rateThe lower energy consumption and cold quantity ratio; a, b, c, d, e and f are regression coefficients; PLR is part load rate; q ref Designing cold quantity for the host; p is ref Designing energy consumption for the host;
cooling water inlet temperature T of different flow under different load rates cond.e The calculation formula of (c) is as follows:
①R＝Q ref /(T f，mean，ref -T soil )
②T f，mean ＝Q real /R+T soil
③T out ＝T f，mean -0.5Q real /m real C
in the formula: r is total heat transfer resistance of the buried pipe; q ref The heat dissipation capacity of the buried pipe under the design working condition is improved;
T f.mean.ref the average water temperature of an inlet and an outlet of the buried pipe under the design working condition; t is soil Is the soil temperature; t is a unit of f.mean The average water temperature of the outlet of the buried pipe under the operating condition is adopted; q real The heat dissipation capacity of the buried pipe under the operation condition is ensured; t is a unit of out The water temperature at the outlet of the buried pipe under the operating condition; m is a unit of real The flow rate is measured by the buried pipe under the operation condition; c is specific heat of water and cooling water inlet temperature T cond.e The temperature T of water at the outlet of the buried pipe under the working condition of operation out Equal;
the total energy consumption of the variable-frequency water pump with different flow rates under different load rates is the total efficiency of the variable-frequency water pump multiplied by the effective power multiplied by the running time, the effective power is the product of the flow rate and the lift of the variable-frequency water pump, and the specific calculation formula is as follows:
⑨η＝η vfd *η m *η p
⑩η vfd ＝50.87+1.283*X-0.0142*X^2+5.842*10^(-5)*X^3
in the formula: eta is the total efficiency (%) of the variable-frequency water pump; eta vfd Is the frequency converter efficiency (%); eta m Motor efficiency (%); eta p Water pump efficiency (%); x is the relative number (%) of revolutions of the motor.
2. The energy-saving calculation method for the variable-frequency water pump of the ground source heat pump system according to claim 1, wherein the operation modes of the ground source side water pump in the step 4 include a fixed-frequency water pump operation mode and a variable-frequency water pump operation mode, and the seasonal total energy consumption is the sum of the operation energy consumptions of the heat pump host units corresponding to different load rate intervals and the sum of the smaller value of the energy consumptions of the variable-frequency water pump and the fixed-frequency water pump in the different load rate intervals.
3. The energy-saving calculation method for the variable-frequency water pump of the ground source heat pump system according to claim 2, characterized in that the total energy consumption of the fixed-frequency water pumps with different flow rates under different load rates is the product of the power of the fixed-frequency water pumps and the running time.
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