JP4694932B2 - Soil heat source heat pump system design method, design support system, and computer program - Google Patents

Description

  The present invention relates to a soil heat source heat pump system that uses a heat pump to circulate a heat medium to a ground heat exchanger to radiate and dissipate heat by using a heat pump to cool and heat, and supply heat or cold to the load side. The present invention relates to a design method, a design support system for supporting the design, and a computer program.

In recent years, a soil heat source heat pump system that uses a heat pump as a heat source to circulate a heat medium in a ground heat exchanger to extract and dissipate heat and supplies hot or cold to the load side has begun to be widely recognized in Japan. Unlike the atmosphere, the soil heat source heat pump system has the advantage that the underground temperature is stable throughout the year without any significant changes, so it has the advantages of energy saving, low running cost, and suppression of carbon dioxide (CO ₂ ) emissions. Therefore, further introduction is expected in the future.

Katsunori Nagano, Takao Katsura, Takashi Nogawa et al .: Soil heat source heat pump system design support tool and its applications (Part 1 to Part 3), Proceedings of the Air Conditioning and Sanitation Engineering Society Annual Conference Hikaru Fujii, Satoshi Akibayashi, Kazuo Oshima: Evaluation of heat exchange well in earth coupled heat pump-Influence of groundwater convection in heat exchange well, Journal of the Geothermal Society of Japan, No. 24 (2002), pp 329-338

  When setting up a soil heat source heat pump system, it is desirable to individually and specifically design specifications that provide high system performance and maintain low energy consumption while also maintaining high energy efficiency.

  However, at the conventional construction site, the design and construction are based on experience values with a high degree of safety without performing accurate and critical evaluation on the performance of the soil heat source heat pump system.

  For example, unlike the atmosphere, the ground tends to have a finite heat source with a thermal storage element. For this reason, if the balance between the amount of heat released to the ground in the summer and the amount of heat collected from the ground in the winter is biased during the operation of the soil heat source heat pump system, there is a concern about the rise and fall of the underground temperature over time. Long-term operation of the heat pump system becomes difficult.

  The present invention has been made in view of the above points, and predicts the temperature change on the heat source side to optimize the design of the soil heat source heat pump system, in particular, the design that realizes the long-term operation of the soil heat source heat pump system. It aims to make it possible.

The design method of the soil heat source heat pump system according to the present invention is a soil heat source heat pump system that uses a heat pump to circulate a heat medium to the ground heat exchanger using the ground as a heat source, collects and dissipates heat, and supplies hot or cold to the load side. Time series change of heat load processed by a soil heat source heat pump system calculated using conditions including a heating period and a cooling period , ground environmental conditions, and specifications of the underground heat exchanger and heat pump Set the specifications of the soil heat pump system including the specifications of the above, simulate the operation of the soil heat source heat pump system, analyze the heat balance, and obtain the time series change of the temperature on the heat source side, At the end of the cooling period of the next year and at least one of the start of the cooling period and the end of the heating period of the next year, The temperature of the heat source side is the result of simulation by析手order of repeating the simulations while changing at least one of the soil source heat pump system in the process heat load and specification of the soil source heat pump system to substantially match It has the specification determination procedure which determines the heat load processed with the said soil heat source heat pump system, and the specification of the said soil heat source heat pump system.
A design support system for a soil heat source heat pump system according to the present invention is a soil heat source heat pump system that uses a heat pump as a heat source to circulate a heat medium in a ground heat exchanger to extract and dissipate heat, and supply hot or cold to the load side. Design support system for soil heat source heat pump system to support the design of the soil, and the time series change of the heat load processed by the soil heat source heat pump system calculated using the conditions including the heating period and the cooling period , the ground environmental conditions In addition, the specifications of the soil heat pump system including the specifications of the underground heat exchanger and the heat pump are set, the operation of the soil heat source heat pump system is simulated , the heat balance is analyzed, and the temperature of the heat source side is and analysis means for determining a series change, at the end cooling period of heating period at the start and the next year, and, cooling period In Hajimeji at least one of the heating period at the end of the next year, the thermal load and the soil heat source temperature of the heat source side is a result of simulation by said analysis procedure is treated with the soil source heat pump system to substantially match A heat load to be processed by the soil heat source heat pump system by repeating the simulation while changing at least one of the specifications of the heat pump system, and specification determining means for determining the specifications of the soil heat source heat pump system .
The computer program according to the present invention uses a heat pump to support the design of a soil heat source heat pump system that circulates a heat medium in a ground heat exchanger using the ground as a heat source, extracts heat, and supplies hot or cold to the load side. Time series change of heat load processed by a soil heat source heat pump system calculated using conditions including a heating period and a cooling period , ground environmental conditions, specifications of the underground heat exchanger, and heat pump Set the specifications of the soil heat pump system including the specifications of the above , analyze the operation of the soil heat source heat pump system to analyze the heat balance, and obtain the time series change of the temperature on the heat source side, At the end of the next year's cooling period and at the start of the cooling period and at the end of the next year's heating period In the simulation while changing at least one of the specifications of the soil source heat pump system heat load and the soil source heat pump system for processing so that the temperature of the analyzing heat source side is a result of simulation by procedures substantially coincide The computer is caused to execute a specification determination process for determining the heat load to be processed by the soil heat source heat pump system and the specifications of the soil heat source heat pump system.

  According to the present invention, the operation of the soil heat source heat pump system is simulated, and the temperature change on the heat source side that affects the operation efficiency is predicted. It is possible to evaluate the economic efficiency and environment and reflect it in the system design. Moreover, the temperature on the heat source side as a result of the simulation is substantially the same at the start of the heating period and at the end of the cooling period of the next year, and at least one of the start of the cooling period and the end of the heating period of the next year. The specifications of the soil heat source heat pump system can be determined at the same time, so that the amount of heat released to the ground in the summer, the amount of heat collected from the ground in the winter, and the heat balance with the surrounding ground can be balanced, and It is possible to realize a long-term operation of the soil heat source heat pump system.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
First, in FIG. 1, the schematic structure of the whole soil heat source heat pump system used as object in this embodiment is shown. The soil heat source heat pump system includes a plurality of underground heat exchangers 101 embedded in the ground, a heat pump 102 for circulating a heat medium through the various regional heat exchangers 101 to release heat, and heating by the heat pump 102. The main component is an air conditioner 103 that heats or cools the room through a cooled heat medium.

  Here, using the foundation pile of the building as the underground heat exchanger 101 for performing heat extraction and radiation is considered as an effective means for reducing the excavation cost, and further introduction is expected. The steel pipe pile which is a hollow pipe body is one of them, but since it has a water-stopping property, the cavity can be filled with water. In particular, in the case of a steel pipe pile with a large diameter, the amount of retained water is large, so that there is ease of temperature change. In addition, since natural convection is generated inside, the thermal resistance is reduced, so that excellent heat collecting performance can be expected.

  When using a steel pipe pile as the underground heat exchanger 101, as shown in FIG. 6, a steel pipe well type (direct heat exchange type) and a U tube that is a heat exchange pipe for a steel pipe pile filled with water inside It is conceivable to use an indirect heat exchange type in which heat exchange is performed indirectly by inserting the. In particular, the indirect heat exchange type has advantages such as being able to manage water quality easily by using a sealed circuit, and obtaining heat radiation performance equivalent to that of a steel pipe well type by adjusting the number of U tubes. is there.

  By the way, the present inventors have proposed a design support tool for a soil heat source heat pump system in order to predict the performance of the soil heat source heat pump system, accurately evaluate economic efficiency and environmental performance, and reflect it in the system design. Cage (Non-Patent Document 1) shows an underground temperature calculation method for a plurality of buried pipes. As a result, the direct heat exchange type can be calculated, but the indirect thermal steel pipe type still has an unclear point in the heat transfer between the water filled inside and the U tube.

  In the present embodiment, a soil heat source heat pump system using an indirect heat exchange type heat exchanger is taken as an example, while clarifying a calculation method considering the heat transfer between the water filled in the steel pipe pile and the U tube, A method for supporting design of a soil heat source heat pump system according to the invention will be described.

  In FIG. 2, the functional structure of the design assistance system of the soil heat source heat pump system in this embodiment is shown. The design support system of the present embodiment is based on a storage device 2 that stores data (programs, various arithmetic expressions, and the like) necessary for simulating the operation of the soil heat source heat pump system, and conditions including a heating period and a cooling period. The arithmetic processing device 3 for simulating the operation of the soil heat source heat pump system by various arithmetic processing, the input device 4 for inputting data and conditions including the heating period and the cooling period, and the arithmetic processing by the arithmetic processing device 3 Working memory 5 and an output device 6 for outputting a calculation result or the like by the arithmetic processing unit 3, and are connected to each other via a bus 7 so as to be able to perform data communication.

  The arithmetic processing unit 3 includes an analysis unit 31, a system efficiency calculation unit 32, a power consumption calculation unit 33, a carbon dioxide emission calculation unit 34, a running cost calculation unit 35, and a life cycle calculation unit 36. The

The analysis unit 31 simulates the operation of the soil heat source heat pump system by an arithmetic process using an arithmetic expression described later based on conditions including a heating period and a cooling period. Then, as shown in FIG. 15 and FIG. 18 as an example, the heating period and cooling period set as conditions and the temperature on the heat source side as a result of the simulation (for example, the steel pipe pile surface temperature T _p , the steel pipe pile is filled inside temperature T _w of water, the heat pump primary side outlet temperature T _1out (= heat exchanger inlet heat medium temperature (flow temperature) T _bin), the heat pump primary inlet temperature _{T 1in (= 2T b -T 1out} ) (= The relationship with the heat exchanger outlet heat medium temperature (return water temperature) T _bout )) is presented to the designer via the output device 6.

  Accordingly, the specification of the soil heat source heat pump system can be determined by repeatedly executing the simulation while changing the condition setting until the temperature on the heat source side substantially matches at the start of the heating period and the end of the next cooling period.

Further, it is possible to determine the specifications of the soil source heat pump system so that the temperature T _w and the heat pump primary side outlet temperature T _1out of water filled inside the steel pipe pile does not exceed the set temperature.

  The system efficiency calculation unit 32 calculates a COP (Coefficient of Performance) of the heat pump 102 and calculates the output by dividing the output of the heat pump 102 by the power consumption that is an input.

  The power consumption calculation unit 33 calculates the amount of power consumption in the soil heat source heat pump system, and calculates by dividing the heat output in the air conditioner 103 by the COP of the heat pump 102 calculated by the system efficiency calculation unit 32.

The carbon dioxide emission calculating unit 34 calculates the CO ₂ emission amount per year in the soil heat source heat pump system. The power consumption calculated by the power consumption calculating unit 33 and a predetermined conversion factor (see Table 11). Reference).

  The running cost calculator 35 calculates a running cost per year in the soil heat source heat pump system, and calculates the power consumption calculated by the power consumption calculator 33 and a predetermined power charge form (see Table 11). Use to calculate.

The life cycle calculation unit 36 calculates the average annual primary energy consumption, the average annual CO ₂ emission amount, and the average annual cost of the soil heat source heat pump system within a predetermined period in consideration of the initial cost and the service life.

  Hereinafter, the calculation method of the indirect heat exchange type heat exchanger for simulating the operation of the soil heat source heat pump system will be described. The inventors of the present application have conducted extensive research and have established a calculation method in consideration of heat transfer between the water filled in the steel pipe pile and the U tube in a particularly promising indirect heat exchange type. Table 1 summarizes the symbols used in this specification.

(Experiment overview)
First, the diameter and specifications of the underground heat exchanger were changed to measure and compare the amount of heat collected. As shown in FIG. 3, the steel pipe pile used in the test has a diameter of φ400 mm assuming a combined use as a business building foundation pile, a length of 40 m, two diameters of φ165 mm assuming a residential and heat radiation-only pile, Two 40m long ones were buried. Steel pipe piles were buried at intervals of 10 m or more so that mutual interference due to heat collection of other piles did not occur during the test. In addition, the geological and groundwater surveys and water temperature measurements were conducted in the test site premises along with the heat sampling demonstration test.

  Fig. 4 shows the results of the geological survey and groundwater survey by survey boring conducted in the heat collection experiment. As a result of the survey, the geological structure is top soil, peat layer, volcanic ash fine sand layer, volcanic ash layer and sand layer mixed with gravel. The groundwater level has been confirmed at a depth of 2.6 m, and it is estimated that the water level always exists at this point. Further, when the observation hole water temperature was measured, the average temperature was about 9.3 ° C., and it can be said that this temperature is an uneasy layer temperature.

  In order to measure the temperature inside the steel pipe pile during the test, as shown in FIG. 5, the depth of the pipe inner wall and the internal heat medium (brine in the direct heat exchange type and water in the indirect heat exchange type) in the diameter φ400 mm steel pipe Each of the points 2.5, 5.0, 10.0, 20.0, 30.0, 40.0 m and the wall surface of the U tube at a depth of 20.0 m are similarly deep in the steel pipe with a diameter of 165 mm. A thermocouple was installed on each wall of 4.0, 16.0, 28.0, 40.0 m and on the wall surface of the U tube at a depth of 16.0 m. A platinum resistor temperature sensor T of Pt-100 was set at the entrance / exit point of the underground heat exchanger.

The test was conducted with water temperature (heat exchanger inlet temperature) T _bin and flow m _b to the underground heat exchanger as a constant. The specification of the steel pipe pile used as a ground heat exchanger is three types shown in FIG. Type 1 is a direct heat exchange type in which antifreeze is directly circulated in the steel pipe pile. Type 2 is a so-called indirect heat exchange type (single U tube type) in which a U tube is inserted into a steel pipe pile filled with water to indirectly exchange heat. Type 3 is used by inserting two U tubes (double U tube type). In the indirect heat exchange type, particularly when the diameter is large, the cost of the heat medium filled in the steel pipe pile can be reduced, and the water quality management is facilitated by being a sealed circuit.

  Table 2 shows the test conditions. This time, the case 1 has a diameter of 400 mm and the case 2 has a diameter of 165 mm. Among them, the use of the underground heat exchanger is changed to a direct heat exchange type and an indirect heat exchange type (single U tube and double U tube), The amount of heat collected was compared. Type 1 and type 2 tests were performed first, and type 1 was switched to type 3. If the same pile is used, the internal temperature should be restored after leaving the test period at least twice (100 days minimum) after the test so that the effect of the previous test does not remain. The following test was conducted. What indicated L after the conditions was tested by changing the heat exchanger inlet heat medium temperature from 2 ° C. to −5 ° C., and the rate of increase in the amount of heat collected thereby was compared. The circulation flow rate was about 51 l / min in case 1-1, and about 10 l / min for the others.

Figure 7 shows the change in the supply water temperature T _bin and Kaemizu temperature T _bout of up to 500 hours from the start of the test in each condition. Further, Figure 8 shows the time variation of each of the heat q _ex adopted per underground heat exchanger unit length calculated from the following equation (1).

From the test results, although the return water temperature T _bout gradually decreases with respect to the substantially constant water supply temperature T _bin , if about 240 hours (10 days) have elapsed under all test conditions, the return water temperature T _bout and the sampling temperature are collected. It can be seen that there is no significant change in the amount of heat _qex, and a state in which the amount of heat is obtained stably, that is, a so-called quasi-steady state is reached. In addition, it is thought that the slight amplitude is seen in the measurement result due to the influence of the outside air day and night.

Table 3 shows the average value q _{ex2-ave of the} heat collection amount q _ex after the elapse of 240 hours in cases 1-1 to 1-3 and the heat collection ratio q * based on case 1-1. The heat collection ratio q * of case 1-2 and case 1-3 with respect to case 1-1 after the elapse of 240 hours was 0.83 and 0.98.

Further, Table 4 shows the average value q _ex2-ave in cases 2-1 to 2-3 and the heat collection ratio q * based on case 2-1. The heat collection ratio q * of case 2-2 and case 2-3 with respect to case 2-1 after 240 hours was 0.96 and 1.27.

From these facts, it was confirmed that a steel pipe pile having a small diameter of 165 mm can secure a sufficient amount of heat collection even when only one U tube is inserted as compared with the direct heat exchange type. On the other hand, when the diameter is increased to φ400 mm, a heat collection amount substantially equal to that obtained when a double U tube is obtained with respect to the direct heat exchange type, the number of underground heat exchangers with a limited number is as large as possible. When performing heat collection, it is considered more desirable to select the double U tube type. Further, from comparison between Table 3 and Table 4, it can be seen that when the specifications of the underground heat exchanger are the same, the heat collection amount q _{ex of the} case 1 having a large diameter is larger than that of the case 2.

Further, Table 5 shows the average value q _ex2-ave of case 1-1 and case 1-1L, the temperature difference ΔT and T _bm between the initial value underground temperature T _s0 and the average value T _bm of the heat medium inlet / outlet temperature, Heat collection amount q ^~ _ex2-ave per unit length and temperature difference of intermediate heat exchanger (Note that in this specification, a ^~ means that ^~ is added to a), Case 1- The heat collection ratio q ** per length / temperature difference based on 1 is shown. q ^~ _ex2-ave is _larger in the low temperature condition case 1-1L than the case 1-1, which is the same condition except for the temperature condition, and the heat extraction ratio q ** of the case 1-1L to the case 1-1 is 1. 4.

In addition, in the _comparison of q _ex2-ave , T _bm , q ^~ _ex2-ave , q ** in case 1-2 and case _1-2L shown in Table 6, the same result is obtained. The heat collecting ratio q ** of case 1-2L was 1.3.

  From these facts, when low temperature water at −5 ° C. is circulated, freezing of the surrounding soil can be considered in the direct heat exchange type, and freezing of the filling water around the U tube can be considered in the indirect heat exchange type. It can be seen that the generation of these latent heats increases the amount of heat collected per length and temperature difference. However, it is necessary to pay attention to excessive freezing caused by circulation of a low-temperature heat medium at about -5 ° C over a long period of time.

(Calculation of internal heat resistance of underground heat exchanger)
For the indirect heat exchange type underground heat exchanger, as shown in FIG. 9, it is necessary to consider the thermal resistance due to the convection of the internal filling water. At this time, the internal thermal resistance value based on the outer surface area of the steel pipe is expressed by the following equation (2).

Here, h _uw in the above equation (2) is the convective heat transfer coefficient of water from the outer wall surface of the U tube, and h _pw is the convective heat transfer coefficient of water from the inner wall surface of the steel pipe. When calculating these, especially when the diameter of the steel pipe is small, it is necessary to consider mutual interference. Here, the technique using the equivalent radius of Fujii et al.'S kavanaugh was applied (see Non-Patent Document 2).

On the other hand, when a steel pipe of large diameter, U Grashof number for the value of the distance W between the tube outer wall and the steel pipe inner wall is increased G _r and the Rayleigh number R _a is increased. Here, given the Nusselt number N _u in equation (3), Nusselt number N _u of 30 or more, that is, when the Rayleigh number R _a is greater than about 1.23 × 10 ⁷ Fluid that point Temperature change and convection of (heat medium) are almost eliminated. Therefore, it is considered that the mutual convection interference generated on the outer wall of the U tube and the inner wall of the steel pipe does not occur. In this case, the convective heat transfer coefficient h _uw and the convective heat transfer coefficient h _pw can be calculated based on the Nusselt number N _u calculated by the above equation (3).

As a result, when the Rayleigh number _Ra is 1.0 × 10 ⁷ or less, the internal natural convection is regarded as laminar flow, and the turbulent flow is regarded as turbulent flow, and the convective heat transfer coefficient is calculated. For laminar flow, the Nusselt number N _u is possible to use Macgregor and Emery empirical formula shown in the following equation (4) (see Non-Patent Document 2). For turbulent flow, it is possible to calculate the Nusselt number N _u of each part by the above equation (3) as described above. However, in this case, the Grashof number G _r is calculated using the tube lengths L _u and L _p of the U tube and the steel tube as representative lengths.

Here, the thermal resistance value in the quasi-steady state was calculated based on the actually measured values. Calculation of thermal resistance value using average values of steel pipe inner wall temperature, steel pipe water temperature, and U tube outer wall temperature at a depth of 20 m (16 m for φ165 mm) after 240 hours considered to have reached a quasi-steady state. went. Table 7 shows the diameter of the underground heat exchanger, the state of fluid flow, the brine temperature average value T _bm-ave after the elapse of 240 hours, the U tube outer wall temperature average value _Tu-out-ave , and the steel pipe water temperature average. A value T _w-ave , a steel pipe inner wall temperature average value T _p-in-ave and a thermal resistance value R _p-out1 are shown. Table 7 also shows the thermal resistance value R _p-out2 calculated by the following equations (5) and (6) based on the actually measured values.

From Table 7, except for Case 2-3, although there is a slight error, the values of the thermal resistance value R _p-out1 and the thermal resistance value R _p-out2 are in good agreement. In particular, in an indirect heat exchange type heat exchanger having a diameter of 400 mm steel pipe, a double U tube type thermal resistance value R _p-out1 (0.108 m ² K / 0.1) in both the thermal resistance value R _p-out1 and the thermal resistance value R _p-out2. W) and ^{_{R p-out2 (0.095m 2 K}} / W) , the thermal resistance of a single U-tube ^{_{R p-out1 (0.203m 2 K}} / W) and R _p-out2 (0.167m ² K / W). For this reason, it is possible to quantitatively evaluate the internal thermal resistance value by this calculation method, except in the case where a double U tube is inserted into a thin steel pipe as in case 2-3. I was able to confirm.

(Calculation of temperature on the heat source side by internal heat transfer calculation of indirect heat exchange type heat exchanger)
In the indirect heat exchange type underground heat exchanger as well, as the diameter of the steel pipe pile is larger, the heat capacity of the water filled therein cannot be ignored as in the case of the direct heat exchange type underground heat exchanger. Therefore, a calculation method for internal heat transfer is built in consideration of the heat capacity of the water filled inside.

  By regarding the inside of the U tube as a lumped parameter system, the change in brine heat capacity is calculated as shown in the following equation (7).

By regarding the inside of the steel pipe pile as a lumped parameter system, the change in the heat capacity of the water inside the steel pipe can be expressed by the following equation (8). Incidentally, K in equation _{(8) p-out A p} -out (T p-out -T w) becomes the heat flow supplied to the endless cylindrical surface of the underground temperature calculation method.

When calculating the Grashof number G _r , it is necessary to calculate the U-tube outer wall temperature _Tu-out . The heat balance inside and outside the U tube is expressed by the following equation (9). In the equation (9), the second-stage equation on the right side and the third-stage equation must be equal. Therefore, a U-tube outer wall temperature _Tu-out that satisfies the equation (9) is derived by repeated calculation as shown in FIG. Note that the superscript represents after the lapse of time step ΔT.

Further, as shown in FIG. 10, the heat exchanger temperature T _b in the heat exchanger according to the equation (7) and further the heat exchanger outlet heat medium temperature T _{bout according} to the equation (8) are filled in the steel pipe pile according to the equation (8). The temperature T _{p-out of the} steel pipe pile is derived using the temperature T _{w of} the pipe and further the theoretical heat flow response equation (10) of the infinite cylinder, and the temperature change on the heat source side, which is the most important design index, is predicted Is possible.

That is, in the heat balance inside and outside the heat exchange pipe, the amount of heat transfer from the filling water inside the steel pipe pile to the outer surface of the U tube, the amount of heat conduction in the U tube, and the amount of heat transfer from the inner surface of the U tube to the heat medium Using the fact that the sum is equal, the U tube outer wall temperature _Tu-out and the U tube outer surface heat transfer amount are calculated from the known filling water temperature and heat medium temperature, and based on this, the heat inside and outside the U tube is calculated. The through-flow rate is calculated (steps S1001 to S1008: Formula (9)).

As a result, by considering the inside of the U tube as a lumped constant system, the heat in the U tube is calculated by the sum of the amount of heat supplied from the U tube to the heat pump and the amount of heat supplied from the filling water to the heat medium through the U tube. by utilizing the fact that changes in the heat capacity of the medium is possible to calculate, calculating the heat exchanger within the heat medium temperature T _b is the temperature of the heat source side, and further the heat exchanger outlet heat medium temperature T is the temperature of the heat-source-side _bout is calculated (step S1009: Expression (7)).

Next, by regarding the inside of the steel pipe pile as a lumped constant system, the amount of heat exchanged and supplied from the filling water to the heating medium via the U tube and the amount of heat exchanged and supplied from the soil to the filling water via the steel pipe pile By using the fact that the change in the heat capacity of the filling water can be calculated by the sum, the filling water temperature T _w which is the temperature on the heat source side is calculated (step S1010: Expression (8)).

Furthermore, the steel pipe pile outer surface temperature T _p-out is calculated using the infinite cylindrical surface heat flow response theoretical formula (10) (step S1011). If necessary, an infinite cylinder surface heat flow response theoretical equation (10) using, may be calculated underground temperature T _s.

Here, the calculated value was compared with the actually measured value, and the reproducibility of the calculated value to the actually measured value was confirmed. As calculation conditions, the specifications of the steel pipe pile were an indirect heat exchange type in which a single U tube was inserted, and the calculation was performed at a diameter of φ400 mm and φ165 mm. As an underground condition, the effective thermal conductivity λ _es was 1.5 W / m / K, which is an actual measurement value of the test ground. For the underground temperature, the initial underground temperature was set using the method described above. From the actual measurement, the steel pipe inner wall temperature T _p-in = 8.8 ° C. with a diameter of φ400 mm and the steel pipe inner wall temperature T _p-in = 9.3 ° C. with a diameter of φ165 mm are respectively 9.2. The calculation conditions were given as ° C and 9.3 ° C. Other conditions were set in the same manner as described above.

  11 and 12 show a comparison between the calculated value and the actually measured value of the indirect heat exchange type underground heat exchanger having the diameters of φ400 mm and φ165 mm. From these results, it can be seen that the calculated values reproduce the measured values well in both the diameters of φ400 mm and φ165 mm. That is, it was proved that this calculation method is effective for performing an indirect heat exchange type calculation.

  In FIG. 13, the flowchart for demonstrating the flow of the design support of the soil heat source heat pump system in this embodiment is shown. In step S101, conditions are input and set via the input device 4. Conditions include indoor load conditions including heating and cooling periods (heating method, cooling method), ground environmental conditions (improper layer temperature, thermal conductivity, soil heat capacity), soil heat source heat pump system specifications (steel pipe pile specifications, heat pumps) Performance, circulation pump, brine).

  In step S102, the operation of the soil heat source heat pump system is simulated by the analysis unit 31 of the arithmetic processing device 3 based on the conditions set in step S101.

  In step S103, the temperature on the heat source side as a result of the simulation is substantially the same at the start of the heating period and at the end of the cooling period of the next year, and at the start of the cooling period and at the end of the heating period of the next year. Determine whether to do. The determination in step S103 may be made by the designer based on the relationship between the heating period and cooling period output to the output device 4 and the temperature on the heat source side, or the arithmetic processing unit 3 may You may make it determine according to the determined rule. Note that the term “substantially coincidence” as used in the present invention means that not only the temperatures completely coincide but also a predetermined temperature difference is allowed.

  If the temperature on the heat source side does not substantially match, the process returns to step S101, and the steel pipe pile specifications and the heat pump performance are changed among the conditions, mainly the specifications of the soil heat source heat pump system. On the other hand, if the temperatures on the heat source side are substantially the same, the conditions set in step S101 are referred to, that is, the soil heat source heat pump system having the same temperature on the heat source side is considered to be optimal. It is determined as the specification of the heat source heat pump system (step S104).

Example 1
The introduction study will be described as an example of all air conditioning of a building with a soil heat source heat pump system using steel pipe piles. Target building is one-story, ceiling height is 6m, total floor area is about 2000m ^2. 7x10 (= 70) steel pipe foundation piles with a length of 37m were buried at intervals of 7m in the underground pit space of this building.

Table 8 shows the calculation conditions. The indoor conditions were set to room temperature of 22 ° C. or higher during winter heating, room temperature of 26 ° C. or lower, and humidity of 60% or lower during summer cooling. The heating and cooling load of the building was performed using the heat load calculation program SMASH. FIG. 14 shows the total heat load including latent heat and sensible heat according to time. Heating was performed by floor heating and a fan coil unit, and cooling was performed only by the fan coil unit. The heat pump secondary side (indoor side) outlet temperature T _2out was kept constant at 40 ° C., and the heat radiation amount was adjusted by adjusting the circulation flow rate with respect to the load. The compressor of the heat pump is 50 horsepower, and the heat output can be adjusted by adjusting the rotation speed of the compressor with respect to the heat load. For the COP of the heat pump, an approximate expression was given based on the performance diagram of the actual machine. Three heat collection side circulation pumps were installed, and the number control was performed according to the load. All the steel pipe piles had a diameter of 400 mm and were used as a single U tube indirect heat exchange type heat exchanger. The underground temperature was 10.0 ° C., and the effective thermal conductivity λ _es of the soil was 1.5 / m / K because most of the formation occupies the sand formation.

Based on the above-mentioned calculation conditions, an operation simulation of a soil heat source heat pump system for 5 years was performed. The temperature change of each part for every time of the operation | movement 5th year of all the steel pipe pile average is shown in FIG. In FIG. 15, T _2out is the heat pump secondary side (indoor side) outlet temperature, T _p is the steel pipe pile surface temperature, T _w is the temperature of the water filled in the steel pipe pile, and T _1out is the heat pump primary side outlet temperature ( = heat exchanger inlet heat medium temperature (flow temperature) T _bin), T _b is within the heat medium average temperature heat exchanger. In this case, the heat pump primary side outlet temperature T _1out and heat pump primary inlet temperature T _1in is _{T b = (T bin + Tb} out) / 2 of the relationship. Incidentally, the steel pipe pile surface temperature T _p in FIG. 15, almost invisible overlaps the upper end of the temperature T _w of water filled in the steel pipe pile.

Table 9 shows the total amount of heat collected during the heating and cooling periods, heat pump power consumption, circulation pump power consumption, heat pump average COP, and average system COP (SCOP) at this time. The minimum temperature of T _lout at which the temperature of the heat medium during the winter heating decreases most was 0.2 ° C., and the minimum temperature of the water temperature T _{w in} the steel pipe was 4.9 ° C.

Also, at the beginning of the heating period of the fifth year (October 1) and at the end of the next year's cooling period (September 30), the temperature on the heat collection side (steel pipe pile surface temperature T _p , filling the steel pipe pile inside temperature T _w of water, the heat pump primary side outlet temperature T _1out (= heat exchanger inlet heat medium temperature (flow temperature) T _bin), the heat pump primary inlet temperature _{T 1in (= 2T b -T 1out} ) ( = It can be seen that there is almost no change in the heat exchanger outlet heat medium temperature (return water temperature) T _bout )). These show that long-term soil heat source heat pump system operation is possible.

  As shown in Table 9, the average COP during heating was 4.5, and the average SCOP was 3.1. The total heat release during cooling was 50.6 GJ, and the SCOP at this time was 9.0. As a result, it was confirmed that high-efficiency natural cooling by the heat circulation method can be performed for all cooling loads.

Here, the air heat source heat pump (ASHP) system and the gas-fired absorption cold / hot water generator were taken up as the target methods, and the environmental performance and economic efficiency of the soil heat source heat pump system were evaluated. Based on the performance of the target method shown in Table 10, the power consumption and the gas consumption were calculated, and the annual CO ₂ emission amount and the annual running cost were calculated from the conversion coefficient shown in Table 11. As a result, a comparison of the annual CO ₂ emission amount and the annual running cost is shown in FIG. In annual CO ₂ emissions, CO ₂ emissions of soil source heat pump system is about 19800Kg, ASHP system, compared to about 36000kg absorption chiller generator, about 45% of CO ₂ emission reduction effect I found out. In comparison of running costs, it was found that the soil heat source heat pump system can be expected to save approximately 340,000 yen compared to the ASHP system and approximately 1,040,000 yen compared to the absorption cold / hot water generator. From these, it can be said that the superiority of the soil heat source heat pump system has been clarified in terms of both environmental performance and economy.

(Example 2)
The target building consists of a two-story low-rise part (approximately 2000 m ² ) and a four-story high-rise part (approximately 2800 m ² ), and 51 steel pipe piles are specified for the high-rise part. The length of the steel pipe pile to be specified is 6 to 7.5 m. Here, the effective length used as the underground heat exchanger was 4.5 to 6 m excluding the pile head 1 m for filling concrete and the tip blade portion 0.5 m. As a result, the total effective length was 239.8 m.

With the determined effective length of the underground heat exchanger, it is considered difficult to heat the entire building with the soil heat source heat pump system. Therefore, the following conditions were given, and the building-side load was set accordingly. First, in order to prevent the water in the pile from freezing, the heat pump primary side outlet temperature T _1out (pile water supply temperature) is _kept at 2 ° C. or higher, and the temperature T _{w of} the water filled in the steel pipe pile is kept at 0 ° C. or higher. Secondly, in order to prevent a long-term decrease in underground temperature, a circulation pump is operated in summer, natural cooling is performed, and recharging is performed with the exhaust heat.

  In consideration of this condition and the conditions on the heat collection side, it was decided to cover the 50 kW base load of the external air conditioning load of the building with the soil heat source heat pump system. However, since there is a possibility that the heat collection temperature may reach a dangerous area on the 50 kW base, 75 × 3 borehole type ground heat exchangers are buried in addition to the steel pipe foundation piles to make up for the shortage.

Table 12 shows the calculation conditions. At the time of heating in winter, the amount of heat for setting the air after heat exchange by the total heat exchanger to 22 ° C. was taken as the external air conditioning load. T _2out was kept constant at 40 ° C., the air volume of the water-air heat exchanger was adjusted with respect to the load, and the heat radiation was adjusted. The compressor of the heat pump is 20 horsepower, the amount of heat supplied is 50 kW, and the heat output can be adjusted when the load of the external conditioner is lower than that. For the COP of the heat pump, an approximate expression was given based on the performance diagram of the actual machine. During operation, the 50 kW base load for all external air conditioner loads including low-rise buildings was taken as the burden of the soil heat source heat pump system. As a result, the time required for all output operation of the heat pump was increased, and the efficiency of the heat pump in actual operation was improved. In addition, the amount of heat to be recharged was increased by circulating cold water to all external air conditioners in the summer. During summer cooling, when the outside air temperature exceeds the chilled water temperature, the outside air taken in is exchanged with the cold water obtained by circulating the underground heat exchanger through the water-air heat exchanger, It was supposed to blow. The circulation pump was operated only when a load was generated. All the steel pipe piles had a diameter of 500 mm, and a double U tube type was used to increase the amount of heat collected per unit length. The underground temperature was 12.1 ° C. from the water temperature measurement result of the observation hole in the site, and the effective thermal conductivity of the soil was 2.1 W / m / K based on the result of the local thermal response test.

  From these calculation conditions, the change with time of the heat load borne by the soil heat source heat pump system is as shown in FIG. 17, the total heating load was 230.1 GJ, and the total cooling load was 75.6 GJ. Calculations were performed individually assuming that there was no thermal interference due to heat collection on the steel pipe pile side and borehole side. In order to obtain the same system performance on the steel pipe pile side and the borehole side, 80% of the total load was borne by heat collection on the steel pipe pile side, and the rest was borne on the borehole side.

Based on the above-mentioned calculation conditions, an operation simulation of a soil heat source heat pump system for 5 years was performed. The temperature change of each part for every time of the operation | movement 5th year of all the steel pipe pile average is shown in FIG. Table 13 shows the total heat collection amount, heat pump power consumption, circulation pump power consumption, heat pump average COP, and average system COP (SCOP) during the heating and cooling periods at this time. The minimum temperature of T _lout at which the temperature of the heat medium during the winter heating is the lowest was −0.8 ° C., and the minimum temperature of the water temperature T _{w in} the steel pipe was 4.7 ° C.

  In addition, as in Example 1, there is almost a difference in the temperature on the heat collecting side between the start of the heating period of the fifth year (October 1) and the end of the cooling period of the next year (September 30). It was confirmed that long-term operation of the soil heat source heat pump system is possible.

  As shown in Table 13, the average COP during heating was as high as 4.4, but the average SCOP was as low as 2.7. This is because the ratio of the circulation pump power consumption to the total power consumption is large. This suggests that, in large-scale buildings, reducing transportation power will be a future challenge for improving SCOP.

Here, a gas-fired absorption-type cold / hot water generator was taken as the target method, and a comparison was made with the target method producing as much heat as the heat generated by the soil heat source heat pump system. The amount of power consumption and gas consumption was calculated in the same manner as in Example 1, and the annual CO ₂ emission amount and the annual running cost were calculated. As a result, FIG. 19 shows a comparison of the annual CO ₂ emission amount and the annual running cost with respect to the external compressor load. Compared with the case where only the soil heat source heat pump system and heating were performed in the amount of CO ₂ emission per year, the CO ₂ reduction amount was 3830 kg. Even though the soil heat source heat pump system is cooling for recharging, it can be expected to have a sufficient CO ₂ emission reduction effect compared to the case where only heating is performed with an absorption-type cold / hot water generator. I understood. Also, in the comparison of running costs, the soil heat source heat pump system is about 380,000 yen when only heating is performed and about 530,000 yen when both heating and cooling are performed, compared to the absorption-type cold / hot water generator. It turns out that cost reduction can be expected. From these, it can be said that the superiority of the soil heat source heat pump system has been clarified in terms of both environmental performance and economy.

  In the present embodiment, a soil heat source heat pump system using an indirect heat exchange type heat exchanger is taken as an example, but the present invention is not limited thereto. That is, the simulation of the operation of the soil heat source heat pump system performed in the analysis unit 31 may not use the above-described arithmetic expression.

  The soil heat source heat pump system of the embodiment described above is specifically configured by a computer system or an apparatus. Accordingly, a storage medium storing software program codes for realizing the functions described above is supplied to the system or apparatus, and a computer (or CPU or MPU) of the system or apparatus reads and executes the program codes stored in the storage medium. Needless to say, this can be achieved.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code itself and the storage medium storing the program code constitute the present invention. As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

It is a figure which shows the schematic structure of the whole soil heat-source heat pump system used as object in this embodiment. It is a figure which shows the function structure of the design assistance system of the soil heat source heat pump system in this embodiment. It is a figure which shows arrangement | positioning of the steel pipe pile for an experiment. It is a figure which shows the result of the geological survey and groundwater survey by the survey boring performed with the heat-collection experiment. It is a figure which shows the outline | summary of an experimental apparatus. It is a figure which shows the specification of an underground heat exchanger. It is a characteristic view which shows the temperature change of an underground heat exchanger entrance / exit heat medium. It is a characteristic view which shows the change of the amount of heat collection. It is a figure which shows the calculation outline | summary about an indirect heat exchange type | mold underground heat exchanger. It is a flowchart for demonstrating indirect heat exchange type heat exchanger calculation. It is a characteristic view which shows the comparison of the calculated value and actual value of the return water temperature in diameter phi400mm. It is a characteristic view which shows the comparison of the calculated value and actual value of the return water temperature in diameter 165mm. It is a flowchart for demonstrating the flow of the design support of the soil heat source heat pump system in this embodiment. It is a characteristic view which shows the heating / cooling load of the building in Example 1. FIG. It is a characteristic view which shows the temperature change of each part for every time of the driving | operation 5 years in Example 1. FIG. Annual CO ₂ emissions in Example 1, a diagram illustrating the results of a comparison of the annual running cost. It is a characteristic view which shows the heating / cooling load of the building in Example 2. FIG. It is a characteristic view which shows the temperature change of each part for every time of the driving | operation 5 years in Example 2. FIG. Annual CO ₂ emissions in Example 2, a diagram illustrating the results of a comparison of the annual running cost.

Explanation of symbols

2 Storage Device 3 Arithmetic Processing Device 4 Input Device 5 Working Memory 6 Output Device 7 Bus 31 Analysis Unit 32 System Efficiency Calculation Unit 33 Power Consumption Calculation Unit 34 Carbon Dioxide Emission Calculation Unit 35 Running Cost Calculation Unit 36 Life Cycle Calculation Unit 101 Medium heat exchanger 102 Heat pump 103 Air conditioner

Claims (9)

It is a design method of a soil heat source heat pump system that uses a heat pump as a heat source to circulate a heat medium in the underground heat exchanger and collects heat and supplies heat or cold to the load side,
Soil heat pump including time series change of heat load processed by the soil heat source heat pump system calculated using conditions including heating period and cooling period , ground environmental conditions, and specifications of the underground heat exchanger and heat pump Set the system specifications, simulate the operation of the soil heat source heat pump system, analyze the heat balance, and obtain the time series change of the temperature on the heat source side ,
The temperature on the heat source side, which is the result of the simulation according to the analysis procedure, substantially matches at the beginning of the heating period and at the end of the cooling period of the next year and / or at the start of the cooling period and at the end of the heating period of the next year. The heat load to be processed by the soil heat source heat pump system and the heat load to be processed by the soil heat source heat pump system by repeating the simulation while changing at least one of the specifications of the soil heat source heat pump system and the soil heat source heat pump A design method for a soil heat source heat pump system, comprising a specification determination procedure for determining a system specification. In the specification determination procedure, the heat load to be processed by the soil heat source heat pump system and the specifications of the soil heat source heat pump system are determined so that the temperature on the heat source side as a result of the simulation by the analysis procedure does not exceed a set temperature. The soil heat source heat pump system design method according to claim 1. 2. The underground heat exchanger is configured to indirectly perform heat exchange by inserting a heat exchange pipe for circulating a heat medium into a hollow tube body filled with water. Or the design method of the soil heat source heat pump system of 2 or 2 . The temperature on the heat source side is the underground temperature, the surface temperature of the hollow tube, the temperature of the water filled in the hollow tube, the heat medium temperature in the heat exchanger, the heat exchanger inlet heat medium temperature, the heat exchange The design method of the soil heat source heat pump system according to claim 3 , wherein the temperature is at least one of the temperature at the outlet heat medium. In the heat balance inside and outside the heat exchange pipe, the amount of heat transfer from the filling water inside the hollow tube body to the outer surface of the heat exchange pipe, the amount of heat conduction in the heat exchange pipe, and the heat exchange pipe Using the fact that the sum of heat transfer amounts from the inner surface to the heat medium is equal, the heat exchange pipe outer surface temperature and the heat exchange pipe outer surface heat transfer amount are calculated from the known filling water temperature and heat medium temperature. And a procedure for calculating the heat transmissivity inside and outside the heat exchange pipe based on this,
As a result, by regarding the inside of the heat exchange pipe as a lumped constant system, the amount of heat supplied from the heat exchange pipe to the heat pump and the heat exchange from the filling water to the heat medium are supplied through the heat exchange pipe. Using the fact that the change in the heat capacity of the heat medium in the heat exchange pipe can be calculated by the sum of the heat amounts, the heat medium temperature in the heat exchanger, which is the temperature on the heat source side, is calculated, and further on the heat source side A procedure for calculating the heat exchanger outlet heat medium temperature, which is the temperature,
Next, by regarding the inside of the hollow tube body as a lumped constant system, the amount of heat supplied by heat exchange from the filling water to the heat medium through the heat exchange pipe, and the hollow tube body from the soil to the filling water. The fact that the change in the heat capacity of the filling water can be calculated by the sum of the amount of heat exchanged and supplied through the filling water temperature, the surface temperature of the hollow tube body, The method for designing a soil heat source heat pump system according to claim 3 , further comprising: calculating a middle temperature. 6. The method for designing a soil heat source heat pump system according to claim 5 , wherein the surface temperature or underground temperature of the hollow tube body is calculated using an infinite cylindrical surface heat flow response theory. The said hollow tube body is a steel pipe pile, The design method of the soil heat source heat pump system of any one of Claims 3-6 characterized by the above-mentioned. Design of a soil heat source heat pump system to support the design of a soil heat source heat pump system that uses the heat pump as a heat source to circulate a heat medium in the underground heat exchanger and extract heat and supply heat or cold to the load side A support system,
Soil heat pump including time series change of heat load processed by the soil heat source heat pump system calculated using conditions including heating period and cooling period , ground environmental conditions, and specifications of the underground heat exchanger and heat pump Analytical means for setting the system specifications, simulating the operation of the soil heat source heat pump system to analyze the heat balance, and obtaining the time series change in temperature on the heat source side ;
The temperature on the heat source side, which is the result of the simulation according to the analysis procedure, substantially matches at the beginning of the heating period and at the end of the cooling period of the next year and / or at the start of the cooling period and at the end of the heating period of the next year. The heat load to be processed by the soil heat source heat pump system and the heat load to be processed by the soil heat source heat pump system by repeating the simulation while changing at least one of the specifications of the soil heat source heat pump system and the soil heat source heat pump A design support system for a soil heat source heat pump system, comprising a specification determining means for determining a system specification. It is a computer program for supporting the design of a soil heat source heat pump system that uses a heat pump as a heat source to circulate a heat medium in a ground heat exchanger to extract and dissipate heat and supply heat or cold to the load side,
Soil heat pump including time series change of heat load processed by the soil heat source heat pump system calculated using conditions including heating period and cooling period , ground environmental conditions, and specifications of the underground heat exchanger and heat pump Set the system specifications, simulate the operation of the soil heat source heat pump system, analyze the heat balance, and obtain the time series change of the temperature on the heat source side ,
The temperature on the heat source side, which is the result of the simulation according to the analysis procedure, substantially matches at the beginning of the heating period and at the end of the cooling period of the next year and / or at the start of the cooling period and at the end of the heating period of the next year. The heat load to be processed by the soil heat source heat pump system and the heat load to be processed by the soil heat source heat pump system by repeating the simulation while changing at least one of the specifications of the soil heat source heat pump system and the soil heat source heat pump A computer program for causing a computer to execute specification determination processing for determining system specifications.

Images