JP5792501B2 - Thermal storage device and method for preventing freezing thereof - Google Patents

Description

The present invention relates to, for example, a heat storage device that is used in a cogeneration system and stores exhaust heat of an engine generator or a fuel cell, and a freeze prevention method thereof.

  Cogeneration systems that store exhaust heat from engine generators and fuel cells and use them for hot water supply have become widespread. In the hot water storage device configured by this cogeneration system, when the outside air temperature decreases, the water flowing in the water supply path may freeze.

Regarding prevention of freezing of this water supply path, the following Patent Document 1 is provided with a water supply path and a bypass path connecting the hot water supply path, and the hot water supply path is provided with a flow path switching mechanism. It describes that freezing is prevented by flowing a part or all of hot water flowing through the hot water supply path from the bypass path to the water supply path to increase the temperature.

JP 2009-257656 A

  By the way, when the water heated by the combined heat and power means (Patent Document 1) is used for freezing prevention, the combined heat and power means is operated, or the combined heat and power means is operated to prevent freezing, and exhaust heat is generated. It is necessary to be in a state.

  Then, the objective of the thermal storage apparatus of this invention and its freezing prevention method is in view of the said subject, and utilizes the heat | fever of the heat medium stored in the thermal storage tank, and is preventing the freezing of a circulation circuit.

The purpose of this is to prevent the water supply path from freezing by efficiently using heat storage even when exhaust heat is not generated, such as when the operation of the combined heat and power supply means is stopped. .

  In order to solve the above problems, the heat storage device and the freeze prevention method thereof according to the present invention relate to freeze prevention of a heat storage device that stores heat in a heat storage tank by exchanging heat from a heat source to a heat medium, and freeze prevention in a circulation circuit of the heat medium. A circuit is configured, and when the outside air temperature falls to the freezing prevention temperature of the heat medium, the heat medium on the lower layer side of the heat storage tank is circulated in the circulation circuit.

In order to solve the above-mentioned problem, the present invention is a heat storage device for exchanging heat from a heat source into a heat medium to store heat in a heat storage tank, and circulating the heat medium taken out from the lower layer side of the heat storage tank to the heat source. After that, a circulation circuit that returns to the upper layer side of the heat storage tank, an auxiliary tank that is provided separately from the heat storage tank and stores a replenishment heat medium to the heat storage tank, and is connected to the lower layer side of the heat storage tank; When the temperature of the heat medium circulated to the heat source is equal to or lower than a predetermined temperature, a return path for preventing the heat medium from returning to the heat storage tank and circulating it to the circulation circuit, and the heat medium to the circulation circuit or the A pump that circulates in a return path, a bypass path that flows the heating medium that circulates in the circulation circuit to the auxiliary tank, an opening / closing means that opens and closes the bypass path, and an outside air temperature is reduced to a freezing prevention temperature of the heating medium. when, Open the serial switching means, the lower side of the heat medium and the supplementary heating medium of the heat storage tank, and the circulation circuit, and the return path, the lower layer side of the thermal storage tank via the bypass path and the auxiliary tank It is equipped with a freeze prevention circuit that circulates to the leading heat medium path .

In order to solve the above-mentioned problem , the present invention is a heat storage device for exchanging heat from a heat source into a heat medium to store heat in a heat storage tank, and circulating the heat medium taken out from the lower layer side of the heat storage tank to the heat source. After that, when the temperature of the heat medium circulated to the heat storage tank and the heat source circulated to the heat source is lower than a predetermined temperature, the heat medium is prevented from returning to the upper layer side of the heat storage tank. A return path that circulates to the circulation circuit, a pump that circulates the heat medium to the circulation circuit or the return path, and a heat storage tank that is provided separately from the heat storage tank to store the heat medium . an auxiliary tank Ru provided with a communicating pipe between a branch point of the return path provided in the communicating pipe, when the outside air temperature drops to freezing prevention temperature of the heating medium, the lower side of the heating medium of the heat storage tank The circulation circuit and the return Ru and a freeze prevention circuit for circulating a.

In order to solve the above problem, preferably in the heat storage device,
A temperature sensor that detects an outside air temperature, a switching unit that is installed at a branch point between the circulation circuit and the return path, and switches the heating medium path of the heating medium, and a detection temperature of the temperature sensor detects the freeze prevention temperature In this case, a control unit may be provided that switches the circulation path of the heat medium to the return path by the switching unit, operates the pump, and controls the operation to a continuous operation or an intermittent operation.

  In order to solve the above-described problem, preferably, in the heat storage device, the control unit preferably further includes the switching unit to switch the heating medium to the return path when the temperature sensor detects the freeze prevention temperature. The circulation path may be switched, the pump may be operated, the operation may be controlled to a continuous operation or an intermittent operation, and the opening / closing means may be opened.

In order to solve the above problems, the present invention is provided separately from the circulation circuit for circulating the heat medium taken out from the lower layer side of the heat storage tank to the heat source and then returning it to the upper layer side of the heat storage tank, and the heat storage tank. When the temperature of the auxiliary tank connected to the lower layer side of the heat storage tank and the temperature of the heat medium circulated to the heat source is equal to or lower than a predetermined temperature , the heat medium is stored in the heat storage tank. A return path for preventing return to the heat storage tank and circulating to the circulation circuit, a pump for circulating the heat medium to the circulation circuit or the return path, and the heat medium circulating to the circulation circuit to the auxiliary tank And a freezing prevention method for a heat storage device that includes a bypass passage for flowing and opening / closing means for opening and closing the bypass passage, and exchanging heat from a heat source to a heat medium to store heat in a heat storage tank, wherein an outside air temperature of the heat medium Freezing prevention temperature When lowered, open the closing means, the lower side of the heat medium and the supplementary heating medium of the heat storage tank, and the circulation circuit, and the return path, via the bypass path and the auxiliary tank said A freeze prevention circuit is formed that circulates to the heat medium path leading to the lower layer side of the heat storage tank .

In order to solve the above problems , the present invention circulates the heat medium taken out from the lower layer side of the heat storage tank to the heat source and then returns it to the upper layer side of the heat storage tank, and the temperature of the heat medium circulated to the heat source A return path for preventing the heat medium from returning to the upper layer side of the heat storage tank and circulating it to the circulation circuit when the temperature is equal to or lower than a predetermined temperature, and a pump for circulating the heat medium to the circulation circuit or the return path comprising the the auxiliary tank comprises a communicating pipe between the lower side of the heat storage tank and provided separately been reservoir is the heating medium the heat storage tank, and a branch point of the return path provided in the communicating pipe , A freezing prevention method for a heat storage device that exchanges heat of a heat source with a heat medium and stores the heat in a heat storage tank, and when the outside air temperature falls to the freeze prevention temperature of the heat medium , Heat medium through the circulation circuit and the front Forming a freeze prevention circuit for circulating the return path.

  In order to solve the above-described problem, in the method for preventing freezing of the heat storage device, preferably, the heat storage device is further installed at a branch point between a temperature sensor that detects an outside air temperature, the circulation circuit, and the return path. The heat storage device includes a switching unit that switches a medium path and a control unit, and when the detected temperature of the temperature sensor detects the freezing prevention temperature, the control unit causes the switching unit to switch the heating medium to the return path. The circulation path may be switched, the pump may be operated, and the operation may be controlled to be continuous operation or intermittent operation.

In order to solve the above-mentioned problem, preferably, in the method for preventing freezing of the heat storage device, preferably, when the temperature detected by the temperature sensor detects the freeze-preventing temperature, the control unit sets the return path to the return path. The heating medium circulation path is switched, the pump is operated, the operation is controlled to be a continuous operation or an intermittent operation, and the opening / closing means is opened to use the replenishing heat medium for freezing prevention.

  According to the heat storage device and the freeze prevention method of the present invention, any of the following effects can be obtained.

  (1) Prevention of freezing of the circulation circuit that circulates the heat medium can be performed by using the heat of the heat medium in the heat storage tank connected to the circulation circuit, and freezing can be prevented efficiently.

  (2) Freezing of the circulation circuit can be prevented regardless of whether the heat source is in an operating state or a stopped state.

(3) Since the heat medium on the lower side of the heat storage tank is used for preventing freezing of the circulation circuit, the layer state of the heat medium in the heat storage tank can be maintained without being disturbed. That is, freezing prevention can be implemented without reducing the utilization efficiency of heat storage.

It is a figure which shows an example of the thermal storage apparatus which concerns on 1st Embodiment. It is a figure which shows an example of a heat source. It is a figure which shows an example of the freeze prevention method of a thermal storage apparatus. It is a figure which shows an example of the control apparatus of a thermal storage apparatus. It is a flowchart which shows control of a thermal storage apparatus. It is a flowchart which shows the process sequence of freezing prevention control. It is a flowchart which shows the process sequence of freezing prevention control. It is a flowchart which shows the process sequence of stop time adjustment. It is a figure which shows an example of the thermal storage apparatus which concerns on 2nd Embodiment. It is a figure which shows an example of the freeze prevention method of a thermal storage apparatus. It is a figure which shows an example of the freeze prevention method of a thermal storage apparatus.

[First Embodiment]

  FIG. 1 shows a heat storage device according to the first embodiment. The configuration described in FIG. 1 is an example, and the present invention is not limited to such a configuration.

  A heat storage device 2 shown in FIG. 1 is an example of the heat storage device of the present invention and its freeze prevention method. The heat storage device 2 includes a heat storage unit 3 and a heat source 4, and is a system that collects heat by exchanging heat of the heat source 4 with a heat medium 6 to collect heat. The heat source 4 only needs to generate exhaust heat such as a power generation engine.

  For example, water is used as the heat medium 6 and is stored in an open heat storage tank 8. A circulation circuit 10 for the heat medium 6 is connected to the heat storage tank 8, and the circulation circuit 10 draws out the heat medium 6 from the lower part of the heat storage tank 8, and heats the heat medium 6 after the exhaust heat recovery to the heat storage tank 8. Closed circuit returning to the top.

  A pump 12 is installed in the circulation circuit 10, and the pump 12 is driven when the heat source 4 is in operation. The pump 12 is installed at a position higher than the installation surface 13 of the heat storage tank 8, that is, a height position of height h (> 0). When the pump 12 is driven, the heat medium 8 on the lower side of the heat storage tank 8, that is, the low-temperature heat medium 6 is guided to the heat source 4, and the heat medium 6 that absorbs the exhaust heat by heat exchange with the exhaust heat of the heat source 4 is generated. It is returned to the upper part of the heat storage tank 8.

  In the circulation circuit 10, a return path 14 </ b> B connecting the entry side and the exit side of the heat storage tank 8 is formed with respect to the storage path 14 </ b> A reaching the heat storage tank 8. A switching valve 16 is provided at the branch point of the return path 14 </ b> B, and a temperature sensor 18 is installed on the entry side of the heat storage tank 8. When the temperature of the heat medium 6 detected by the temperature sensor 18 does not reach a predetermined high temperature, the switching valve 16 switches the circulation direction of the heat medium 6 from the storage path 14A to the return path 14B, and the heat storage tank 8 side. The heating medium 6 is prevented from returning. As a result, the low-temperature heat medium 6 returns from the return path 14 </ b> B to the heat source 4 through the pump 12, and the exhaust heat is re-exchanged with the low-temperature heat medium 6.

  When the temperature detected by the temperature sensor 18 reaches a predetermined high temperature, the switching valve 16 is switched from the return path 14 </ b> B to the entry side of the heat storage tank 8, and the heated heat medium 6 is returned to the upper part of the heat storage tank 8. As a result, the heat storage tank 8 maintains the hierarchical heat storage in which the upper layer of the heat medium 6 has a high temperature and the lower layer has a low temperature.

  Such a hierarchical state is monitored by a plurality of temperature sensors 21, 22, 23, 24, 25 installed in the heat storage tank 8. The temperature sensors 21, 22, 23, 24, and 25 detect the temperature of each heat medium 6 in the heat storage tank 8 that forms a layer state by specific gravity due to a temperature difference. Here, since the temperature sensors 21, 22, 23, 24, and 25 are installed from the upper layer to the lower layer, when water is used as the heating medium 6, the detected temperature of the lower temperature sensor 25 is about 4 ° C. ] Is detected, the temperature of the entire heating medium 6 in the heat storage tank 8 has decreased to less than 4 [° C.]. That is, since the density of water becomes maximum at about 4 [° C.], the temperature of the lowermost layer of the heat storage tank 8 is usually about 4 [° C.] or higher, whereas the lowermost layer is below about 4 [° C.]. Is a case where the whole heat medium 6 in the heat storage tank 8 is lowered from about 4 [° C.].

  The heat storage tank 8 is provided with an auxiliary tank 30, and water is stored in the auxiliary tank 30 as a replenishing heat medium 6, and this heat medium 6 is used for replenishment in the heat storage tank 8. The auxiliary tank 30 is set to the same height as the heat storage tank 8 by communicating with the lower part of the heat storage tank 8 through the communication pipe 32. Therefore, the heat medium level in the auxiliary tank 30 is the same as the heat medium level of the heat storage tank 8. A level sensor 34 is installed in the auxiliary tank 30 to detect the heat medium level.

  When the heat medium 6 in the heat storage tank 8 decreases due to evaporation or the like, the heat medium level in the heat storage tank 8 is detected by the level sensor 34 in the auxiliary tank 30. When the heat medium level falls below the reference level, the on-off valve 42 in the replenishment path 41 is opened, and the auxiliary water 30 is replenished with clean water 40 used for the heat medium 6, and the heat medium level in the heat storage tank 8 is a predetermined level. Maintained.

  A bypass path 36 is connected to the bottom of the auxiliary tank 30, and the bypass path 36 is connected to the circulation circuit 10 on the outlet side of the pump 12 via an on-off valve 38. That is, the auxiliary tank 30 is connected to the bottom of the heat storage tank 8 via the communication pipe 32 and is connected to the bottom of the heat storage tank 8 via the bypass path 36 and the circulation circuit 10. The on-off valve 38 of the bypass circuit 36 is closed during normal driving, and is opened when the pump 12 installed at a position higher than the lower portion of the heat storage tank 8 for taking out the low-temperature heat medium 6 is vented.

  A load circuit 45 for utilizing the heat of the heat medium 6 is connected to the heat storage tank 8, and a pump 46 and a heat load 48 are installed in the load circuit 45. The heat load 48 is, for example, a hot water supply load or a bath water replenishment load. In the hot water supply load, the heat of the heat medium 6 is exchanged with clean water for use in hot water supply or the like. In this case, the heat medium 6 of the heat storage tank 8 receives a request for using hot water, etc., drives the pump 46, takes out the high-temperature heat medium 6 from the upper part of the heat storage tank 8, undergoes heat exchange with clean water, The low-temperature heat medium 6 is returned to the lower part of the heat storage tank 8.

  The heat source 4 connected to the heat storage unit 3 will be described with reference to FIG. FIG. 2 shows an example of a heat source.

The heat source 4 is provided with an engine unit 54 as shown in FIG. An engine 58 that drives a generator 57 is installed in the engine unit 54, and a circulation circuit 62 that circulates the heat medium 60 is formed in the engine 58. The heat medium 60 collects exhaust heat of the engine 58 by heat exchange. In the circulation circuit 62, a first heat exchanger 64 and a pump 66 are installed, and a heater 68 is installed. The heat exchanger 64 exchanges heat of the heat medium 60 with the heat medium 6. The pump 66 circulates the heat medium 60 through the circulation circuit 62.

The heater 68 is an example of an auxiliary heater that heats the heat medium 60 by electric heat. The surplus power output unit 72 or the commercial AC power supply 74 is connected to the heater 68 via a switch 70. When the generator 57 is driven, the surplus power output unit 72 outputs surplus power obtained by subtracting the load power from the power generated by the generator 57 . When the generator 57 is driven, the switch 70 is switched to the surplus power output unit 72, the heater 68 is heated by the surplus power, and the heat medium 60 is heated. When the generator 57 stops driving, the switch 70 is switched to the commercial AC power source 74 side, the heater 68 is heated by the commercial AC power source 74, and the heat medium 60 is heated.

  A second heat exchanger 78 is installed in the exhaust path 76 of the engine 58. In this heat exchanger 78, the heat of the exhaust gas is exchanged with the heat medium 6 and is recovered in the heat medium 6.

  The freeze prevention circuit 50 of the heat storage unit 3 will be described with reference to FIG. FIG. 3 shows a heat storage unit 3 having a freeze prevention circuit.

  As shown in FIG. 3, the freeze prevention circuit 50 includes a part of the circulation circuit 10 that is a target for preventing freezing, the return path 14 </ b> B, the pump 12, and the switching valve 16, and the heat medium 6 is used as the freeze prevention medium. . The freeze prevention operation is determined by the temperature condition, and the freeze prevention operation is started when the temperature sensor 52 that detects the outside air temperature detects the outside air temperature that has dropped below a predetermined temperature.

  In this freeze prevention operation, the switching valve 16 is switched to the return path 14B side, the on-off valve 38 of the bypass path 36 is opened, and the pump 12 is intermittently operated. At this time, the freeze prevention circuit 50 includes a circulation path I from the pump 12 via the heat source 4 via the switching valve 16 to the pump 12 via the return path 14B via the branch point 44 of the circulation circuit 10 and the branch point from the pump 12. A circulation path II extending from the circulation circuit 10 to the pump 12 through the bypass 56, the auxiliary tank 30, the communication pipe 32, and the heat storage tank 8 is configured. At the branch point 44, the heating medium on the return path 14 </ b> B side joins the heating medium flowing through the circulation circuit 10. At the branch point 56, the heat medium 6 flowing in the circulation circuit 10 branches to the bypass path 36 side and flows into the auxiliary tank 30. In this case, the heat medium 6 in the auxiliary tank 30 flows to the heat storage tank 8 side through the communication pipe 32.

  In this freeze prevention operation, the bypass path 36 is used for bleeding the pump 12, and a part of the heat medium 6 pushed out by the pump 12 circulates in the circulation path II that returns to the heat storage tank 8 via the auxiliary tank 30. . The heat medium 6 supplied to the pump 12 is a mixture of the heat medium 6 from the return path 14 </ b> B and the heat medium 6 in the auxiliary tank 30, and after passing through the pump 12, the circulation circuit 10 on the outlet side of the heat storage tank 8. And sent to the bypass path 36.

  With such a freeze prevention circuit 50, the heat medium 6 used for freeze prevention is taken out from the lower part of the heat storage tank 8. Even if the heat medium 6 taken out from the lower part of the heat storage tank 8 has a low temperature, the heat medium 6 has sufficient heat as compared with the outside air temperature at which freezing is expected. Thus, freezing of the heat medium 6 in the circulation circuit 10 can be prevented.

  The heat medium 6 used for freezing prevention is returned to the lower part of the heat storage tank 8. That is, since it enters the lower part of the heat storage tank 8 via the bypass path 36 and the auxiliary tank 30, the heat medium 6 of the heat storage tank 8 is used, but the hierarchical state of the heat medium 6 in the heat storage tank 8 is not disturbed. . Therefore, since the hierarchical state of the heat medium 6 is maintained, the freeze prevention operation does not adversely affect heat utilization.

  FIG. 4 is referred to for the control device 80 that performs the heat storage operation and the freeze prevention operation of the heat storage device 2. FIG. 4 shows an example of the control device. 4, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals.

  The control device 80 includes a first control unit 82 on the heat storage unit 3 side and a second control unit 84 on the heater 68 side. The control unit 82 and the control unit 84 are connected wirelessly or by wire from the communication units 86 and 88, and heat storage control or freeze prevention control is executed.

  The control unit 82 is composed of, for example, a microcomputer. The control unit 82 includes a memory 90 that stores a control program, calculation data, and the like, and an output circuit 92 that outputs various signals. A time signal is input from the timer 94 to the control unit 82, and a detected temperature is input from the temperature sensors 18, 21, 22, 23, 24, 25, 52 described above. In the control unit 82, various calculations are performed according to various preset data and control programs, and control outputs for the switching valve 16, the on-off valves 38 and 42, the pump (P1) 12, and the pump (P2) 46 are generated. The

  A switch control output for driving the heater 68 is generated from the control unit 82, the switch control output is transmitted to the control unit 84 through communication of the communication units 86 and 88, and the switch 70 is switched by the control unit 84.

  The control by the control device 80 will be described with reference to FIG. FIG. 5 shows a processing procedure of control by the control device 80.

  This processing procedure is an example of a freeze prevention method for a heat storage device according to the present invention, and is an example of a freeze prevention program included in a control program having the control units 82 and 84 as execution subjects.

  In this processing procedure, as shown in FIG. 5, initialization of the control system that controls the heat storage device 2 is executed by turning on the power (step S <b> 11). After the system initialization, it is determined whether there is heat utilization (step S12). If there is heat utilization (YES in step S12), heat utilization control processing is executed (step S13), and the presence / absence of engine operation as the heat source 4 is confirmed (step S14). Even when there is no heat utilization (NO in step S12), the process proceeds to step S14.

  If the engine 58 is operating (YES in step S14), the process proceeds to an exhaust heat recovery process (step S15), an exhaust heat recovery, that is, a heat storage process is executed, and other processes other than the exhaust heat recovery process (steps) S16) is executed, and the process returns to step S12.

  If it is determined in step S14 that the engine 58 is not operating (NO in step S14), a freeze prevention process for the heat storage device 2 is executed (step S17), and the process proceeds to step S16. That is, the freeze prevention process is executed as an interrupt process in the present control process.

  Next, with reference to FIG. 6 and FIG. 6 and 7 show a processing procedure for freezing prevention. 6 and 7, A indicates a connecting portion between the flowcharts.

  This processing procedure is an example of the method for preventing freezing of the heat storage device of the present invention, and is executed for each cycle of the control program. In the execution of this program, for example, the timer 94 counts down when time is set, and when the count value becomes “0”, the timer 94 is in a time-up state and is configured with a countdown timer that stops the countdown. It is not something.

If the heat source 4 is in operation, freezing prevention is unnecessary. Therefore, it is determined whether or not the outside air temperature is equal to or lower than a predetermined temperature T ₁ that is a start temperature for preventing freezing (outside air temperature ≦ predetermined temperature T ₁ ) (step S21). The outside air temperature is a temperature detected by the temperature sensor 52. The predetermined temperature T ₁ as an example is set to 7 ° C., for example.

If the outside air temperature ≦ predetermined temperature T ₁ (YES in step S21), it is determined whether or not the heater 68 is operating (step S22). If the heater 68 is in operation (YES in step S22), and determines whether the temperature ≧ heater operation stop temperature T ₂ of the entire heating medium 6 of the heat storage tank 8 (step S23). The heater operation stop temperature T ₂ is set to 3.5 [° C.], for example.

If the temperature ≧ heater operation stop temperature T ₂ of the entire heating medium 6 of the heat storage tank 8 (YES in step S23), the heater 68 is stopped (step S24), and switching (step a switching valve 16 in the return path 14B side S25), the on-off valve 38 is opened (step S26).

In step S21, unless the outside air temperature ≦ predetermined temperature T ₁ (NO in step S21), and stops the pump 12 (step S27), the on-off valve 38 to the closed (step S28), and stops the heater 68 (step S29 ).

Further, in step S22, if not in the heater 68 is operating (NO in step S22), and determines whether the temperature ≦ heater operation start temperature T ₃ of the whole of the heating medium 6 of the heat storage tank 8 (step S30). If the temperature of the entire heat medium 6 in the heat storage tank 8 is equal to or less than the heater operation start temperature T ₃ (YES in step S30), the heater 68 is operated (step S31), and the switching valve 16 is switched to the storage path 14A side (step S32), the process proceeds to the above-described step S26.

In step S30, (NO in step S30) Temperature ≦ heater operation start temperature T ₃ unless the whole of the heating medium 6 of the heat storage tank 8, the process proceeds to step S25. Further, in step S23, if it is not the temperature ≧ heater operation stop temperature T ₂ of the entire heating medium 6 of the heat storage tank 8 (NO in step S23) also proceeds to step S26.

After opening the on-off valve 38, it is determined whether or not the pump 12 is operating (step S33 in FIG. 7). If the pump 12 is not operating (NO in step S33), it is determined whether or not the timer 94 has expired (step S34). If the timer 94 if the time is up (YES in step S34), the pump 12 is being driven (step S35), and set to a predetermined time TM ₁ the timer 94 starts clocking (step S36), the temperature sensor The detected temperature of 18 is stored as minimum return temperature data (step S37), and the process returns to step S15 (FIG. 5).

In step S33, if the pump 12 is operating (YES in step S33), it is determined whether or not the timer 94 has expired (step S38). If the timer 94 if the time is up (YES in step S38), stops the pump 12 (step S39), to adjust the stop time (step S40), timing sets the wait time data TM ₂ timer 94 Is started (step S36), and the process returns to step S15 (FIG. 5).

  In step S38, if the timer 94 has not expired (NO in step S38), it is determined whether the detected temperature of the temperature sensor 18 is less than the minimum return temperature data (step S42). If the detected temperature of the temperature sensor 18 <the minimum return temperature data (YES in step S42), the temperature detected by the temperature sensor 18 is stored as the minimum return temperature data (step S43), and the process returns to step S15 (FIG. 5). If the detected temperature of the temperature sensor 18 is not less than the minimum return temperature data (NO in step S42), the process returns to step S15 (FIG. 5). That is, if the pump 12 is being driven (step S33) and the timer 94 is being driven (NO in step S38), since the pump 12 is intermittently operated, the pump 12 is maintained in the operating state, and the heat source 4 If the detected temperature of the temperature sensor 18 indicating the return temperature from the temperature is smaller than the value of the minimum return temperature data stored in the memory 90 (YES in step S42), the value is stored in the memory 90 as a new minimum return temperature. (Step S43).

  In this processing procedure, the processing from step S22 to step S32 is processing when the heater 68 generates heat by the heat medium temperature in the heat storage tank 8, and when the outside air temperature becomes 2.5 [° C.] or less, for example, The heater 68 is activated. At this time, the switching valve 16 is switched to the storage path 14A side, and if the temperature of the heat medium in the heat storage tank 8 becomes, for example, 3.5 [° C.] or more, the heat generation of the heater 68 is stopped, and the switching valve 16 is returned to the return path. Switching to the 14B side, the heat medium 6 in the heat storage tank 8 is circulated to the circulation circuit 10, that is, the freeze prevention circuit 50.

  At this time, the switching valve 16 switches to the return path 14B side, and the pump 12 is operated intermittently. Thereby, freezing of the circulation circuit 10 can be prevented, and energy saving can be achieved by intermittent operation of the pump 12.

  Next, FIG. 8 will be referred to regarding the adjustment of the stop time. FIG. 8 shows an example of the processing procedure of stop time adjustment.

  This processing procedure is an example of a freeze prevention method for a heat storage device according to the present invention, and is an example of a freeze prevention program included in a control program having the control units 82 and 84 as execution subjects.

  If the temperature of the heat medium in the circulation circuit 10 is high, the stop time of the pump 12 becomes long. If the temperature of the heat medium in the circulation circuit 10 is low, the stop time of the pump 12 becomes short. These times represent the relationship between the heat medium temperature and the residence time, that is, the stop time of the pump 12 becomes longer, the state in which the heat medium 6 is stagnated in the circulation circuit 10 continues, and the outside air temperature decreases. However, the time until the staying heat medium 6 is frozen is taken into consideration.

In the processing procedure shown in FIG. 8, it is determined whether or not minimum return temperature data <predetermined temperature T ₄ (step S51). The predetermined temperature T ₄ is, for example, 2 [° C.]. If the minimum return temperature data <a predetermined temperature T ₄ (YES in step S51), the waiting time data is 0 (minutes) (step S52), the case (minimum return temperature data is lower than the predetermined temperature T _4), the pump 12 Is continuous operation. Then, the process returns to step S40 (FIG. 7).

In step S51, if the minimum return temperature data <the predetermined temperature T4 is not satisfied (NO in step S51), it is determined whether the minimum return temperature data <the predetermined temperature T ₅ (> T ₄ ) (step S53). If minimum return temperature data <predetermined temperature T ₅ (> T ₄ ) (YES in step S53), standby time data = standby time data−TM ₂ (step S54), and the process returns to step S40 (FIG. 7). TM ₂ is adjustment time, for example, a 2 [min]. In this case, the minimum standby time TMmin = 0 [minutes].

If the minimum return temperature data <predetermined temperature T ₅ (> T ₄ ) is not satisfied in step S53 (NO in step S53), it is determined whether the minimum return temperature data <predetermined temperature T ₆ (> T ₅ ) (step S53). S55). If minimum return temperature data <predetermined temperature T ₆ (YES in step S55), the standby time data is maintained (step S56), and the process returns to step S40 (FIG. 7). In this case, the predetermined temperature T ₆ is, for example, 6 [° C.].

In step S55, the minimum return temperature data <unless the predetermined temperature T ₆ (NO in step S55), and the wait time data = wait time data + TM ₂ (step S57), the process returns to step S40 (FIG. 7). In this case, the maximum standby time TMmax = 10 [minutes].

Thus, if the minimum return temperature of the heat medium 6 is T ₄ (for example, 2 [° C.]) or more and less than T ₅ (for example, 3 [° C.]), the standby time data is TM ₂ (for example, 2 [minute] ], And if it is T ₅ (for example, 3 [° C.]) or more and less than T ₆ (for example, 6 [° C.]) (S110), the waiting time data is not adjusted and the state is maintained. , T ₆ (for example, 6 [° C.]) or more, the standby time data is extended by TM ₂ (for example, 2 [minute]).

  The advantages and effects of the first embodiment described above are listed below.

  (1) Freezing prevention of the circulation circuit 10 that circulates the heat medium can be performed by using the heat of the heat medium 6 in the heat storage tank connected to the circulation circuit 10. Therefore, freezing of the heat medium 6 can be prevented efficiently.

  (2) Freezing of the heat medium 6 in the circulation circuit 10 can be prevented regardless of whether the heat source 4 is in an operating state or a stopped state.

  (3) Since the heat medium 6 on the lower layer side of the heat storage tank 8 is used for preventing freezing of the circulation circuit 10, the layer state of the heat medium 6 in the heat storage tank 8 can be maintained without being disturbed. That is, it is possible to prevent freezing without reducing the utilization efficiency of heat storage.

[Second Embodiment]

  In the first embodiment, the return path 14B is connected to the branch point 44 on the circulation circuit 10 side, and the communication pipe 32 is connected to the lower part of the heat storage tank 8, but the return path 14B and the connection pipe 32 are connected. And the structure connected to the thermal storage tank 8 may be sufficient.

  The second embodiment will be described with reference to FIGS. 9, 10 and 11. FIG. 9 to 11 show a heat storage device according to the second embodiment. The configuration described in FIGS. 9 to 11 is an example, and the present invention is not limited to such a configuration. 9 to 11, the same parts as those in FIG. 1 are denoted by the same reference numerals.

In the heat storage device 2 shown in FIG. 9, the other end of the return path 14B branched from the switching valve 16 is connected to the lower part of the heat storage tank 8, and a branch point 96 is provided in the return path 14B to connect the communication pipe 32 of the auxiliary tank 30. Connected. That is, the return path 14 </ b> B and the communication pipe 32 are coupled and connected to the heat storage tank 8.

  According to such a configuration, as shown in FIG. 10, the switching valve 16 is switched to the return path 14B side and the opening / closing valve 38 is opened to circulate the heat medium 6 as in the first embodiment. Thus, the freeze prevention circuit 50 can be configured.

  Further, in this embodiment, as shown in FIG. 11, by closing the on-off valve 38, the pump 12 reaches the switching valve 16 through the heat source 4, and reaches the pump 12 from the lower layer of the heat storage tank 8 through the return path 14B. The freeze prevention circuit 50 may be configured. In such a configuration, freezing of the circulation circuit 10 can be prevented by using only the heat medium 6 in the lower layer portion of the heat storage tank 8.

[Other Embodiments]

  (1) In the second embodiment, the communication pipe 32 may be provided with an opening / closing valve, and the heating medium 6 passing through the communication pipe 32 may be controlled by opening / closing the opening / closing valve.

  (2) The heat source 4 may be a device that generates exhaust heat other than the engine unit, such as a fuel cell.

  (3) In the first embodiment, the heater 68 is caused to generate heat during the freeze prevention operation. However, the operation of the heater 68 is stopped and the freezing of the circulation circuit 10 is prevented only by the amount of heat stored in the heat medium 6. May be.

As described above, the most preferable embodiment and the like of the present invention have been described. However, the present invention is not limited to the above description, and is described in the claims or disclosed in the specification. It goes without saying that various modifications and changes can be made by those skilled in the art based on the above gist, and such modifications and changes are included in the scope of the present invention.

The present invention prevents the freezing of the circulation circuit that circulates the heat medium by connecting the heat source and the heat storage unit, can be widely used in cogeneration devices, etc., and is useful because it prevents freezing by the amount of heat that the heat storage medium has. It is.

2 Heat storage device 3 Heat storage unit 4 Heat source 6 Heat medium 8 Heat storage tank 10 Circulation circuit 12 Pump 14A Storage path 14B Return path 16 Switching valve 18 Temperature sensor 21, 22, 23, 24, 25 Temperature sensor 30 Auxiliary tank 32 Communication pipe 34 Level Sensor 36 Bypass path 38 On-off valve 44 Branch point 45 Load circuit 50 Freezing prevention circuit 52 Temperature sensor 54 Engine unit
56 branch points
57 Generator 58 Engine 60 Heating medium

Claims (8)

A heat storage device for exchanging heat from a heat source to a heat medium to store heat in a heat storage tank,
After circulating the heat medium taken out from the lower layer side of the heat storage tank to the heat source, a circulation circuit for returning to the upper layer side of the heat storage tank;
An auxiliary tank that is provided separately from the heat storage tank and stores a replenishment heat medium to the heat storage tank, and is connected to a lower layer side of the heat storage tank;
A return path for preventing the heat medium from returning to the heat storage tank and circulating to the circulation circuit when the temperature of the heat medium circulated to the heat source is equal to or lower than a predetermined temperature;
A pump for circulating the heat medium to the circulation circuit or the return path;
A bypass passage for flowing the heat medium circulating in the circulation circuit to the auxiliary tank;
Opening and closing means for opening and closing the bypass path;
When the outside air temperature drops to the freezing prevention temperature of the heat medium, the opening / closing means is opened, the heat medium on the lower layer side of the heat storage tank and the replenishment heat medium , the circulation circuit , the return path, and the A freeze prevention circuit that circulates to a heat medium path that reaches the lower layer side of the heat storage tank via a bypass path and the auxiliary tank ;
A heat storage device comprising: A heat storage device for exchanging heat from a heat source to a heat medium to store heat in a heat storage tank,
After circulating the heat medium taken out from the lower layer side of the heat storage tank to the heat source, a circulation circuit for returning to the upper layer side of the heat storage tank;
A return path for preventing the heat medium from returning to the upper layer side of the heat storage tank and circulating to the circulation circuit when the temperature of the heat medium circulated to the heat source is equal to or lower than a predetermined temperature;
A pump for circulating the heat medium to the circulation circuit or the return path;
The heat storage tank and separately the heating medium is accumulated is provided, an auxiliary tank Ru provided with a communicating pipe between the lower side of the heat storage tank,
A branch point of the return path provided in the communicating pipe,
A freezing prevention circuit that circulates the heat medium on the lower layer side of the heat storage tank to the circulation circuit and the return path when the outside air temperature decreases to the freezing prevention temperature of the heat medium;
Thermal storage device you comprising: a. Furthermore, a temperature sensor that detects the outside air temperature;
A switching means that is installed at a branch point between the circulation circuit and the return path, and switches the heating medium path of the heating medium;
When the detected temperature of the temperature sensor detects the freeze prevention temperature, the switching means switches the circulation path of the heat medium to the return path, operates the pump, and controls the operation to continuous operation or intermittent operation. A control unit;
Heat storage device according to claim 1 or 2, characterized in that it comprises a. When the temperature detected by the temperature sensor detects the anti-freezing temperature, the control unit switches the circulation path of the heating medium to the return path by the switching means, operates the pump, and continuously performs the operation. The heat storage device according to claim 3 , wherein the open / close means is opened while controlling the intermittent operation. After circulating the heat medium taken out from the lower layer side of the heat storage tank to the heat source, a circulation circuit for returning to the upper layer side of the heat storage tank;
An auxiliary tank that is provided separately from the heat storage tank and stores a replenishment heat medium to the heat storage tank, and is connected to a lower layer side of the heat storage tank;
A return path for preventing the heat medium from returning to the heat storage tank and circulating to the circulation circuit when the temperature of the heat medium circulated to the heat source is equal to or lower than a predetermined temperature;
A pump for circulating the heat medium to the circulation circuit or the return path ;
A bypass passage for flowing the heat medium circulating in the circulation circuit to the auxiliary tank;
An opening and closing means for opening and closing the bypass path, a heat storage device freezing prevention method for heat exchange of heat of a heat source to a heat medium to store heat in a heat storage tank,
When the outside air temperature drops to the freezing prevention temperature of the heat medium, the opening / closing means is opened, the heat medium on the lower layer side of the heat storage tank and the replenishment heat medium , the circulation circuit , the return path, and the A freeze prevention method for a heat storage device, characterized by forming a freeze prevention circuit that circulates to a heat medium path that reaches a lower layer side of the heat storage tank via a bypass path and the auxiliary tank . After circulating the heat medium taken out from the lower layer side of the heat storage tank to the heat source, a circulation circuit for returning to the upper layer side of the heat storage tank;
A return path for preventing the heat medium from returning to the upper layer side of the heat storage tank and circulating to the circulation circuit when the temperature of the heat medium circulated to the heat source is equal to or lower than a predetermined temperature;
A pump for circulating the heat medium to the circulation circuit or the return path;
An auxiliary tank provided separately from the heat storage tank to store the heat medium, and provided with a communication pipe between a lower layer side of the heat storage tank;
A freezing prevention method for a heat storage device comprising a branch point of the return path provided in the communication pipe, heat exchange of heat from a heat source to a heat medium, and heat storage in a heat storage tank,
An anti-freezing circuit that circulates a heat medium on a lower layer side of the heat storage tank to the circulation circuit and the return path when an outside air temperature decreases to the anti-freezing temperature of the heat medium. Freezing prevention method. Further, the heat storage device includes a temperature sensor that detects an outside air temperature, a switching unit that is installed at a branch point between the circulation circuit and the return path, and switches the heat medium path of the heat medium, and a control unit.
When the detected temperature of the temperature sensor detects the anti-freezing temperature, the control unit switches the circulation path of the heating medium to the return path by the switching means, operates the pump, and continuously performs the operation. It controls to an intermittent operation | movement, The freeze prevention method of the thermal storage apparatus of Claim 5 or 6 characterized by the above-mentioned. When the detected temperature of the temperature sensor detects the anti-freezing temperature, the control unit switches the circulation path of the heating medium to the return path by the switching means, operates the pump, and continuously performs the operation. The method for preventing freezing of a heat storage device according to claim 7 , wherein the replenishing heat medium is used for freezing prevention by controlling the intermittent operation and opening the opening / closing means.

Images