JP6090568B2 - Water heating system - Google Patents

Description

  The present invention relates to a feed water heating system using a heat pump.

  Conventionally, as disclosed in Patent Document 1 below, a system capable of heating water supplied to a water supply tank (23) of a boiler (24) using a heat pump (12) is known. In addition, the applicant has proposed a feed water warming system in which the efficiency of the heat pump is further improved as compared with this prior art, and has already filed a patent application (Japanese Patent Application No. 2012-79191).

  The pending water supply warming system includes a heat pump and a water supply tank. The water supply tank can be supplied with water via a heat pump, and can be supplied with a replenishment water channel without using a heat pump. Water supply to the water supply tank via the water supply path is sequentially passed through the waste heat recovery heat exchanger, the subcooler, and the condenser. The waste heat recovery heat exchanger is an indirect heat exchanger between the water supply to the water supply tank via the water supply channel and the heat source fluid after passing through the evaporator, and the supercooler to the water supply tank via the water supply channel Indirect heat exchanger between the water supply and the refrigerant from the condenser to the expansion valve. It is preferable to adjust the amount of water flow to the condenser so that the heat pump is operated during water supply to the water supply tank via the water supply path, and the outlet water temperature of the condenser of the heat pump is maintained at the set temperature.

JP 2010-25431 A (FIGS. 2 and 3)

  A problem to be solved by the present invention is a feed water heating system that can continuously change the amount of hot water discharged from the heat pump based on the water level in the feed water tank and quickly follow the usage load of the hot water in the feed water tank to produce hot water. Is to provide.

  The present invention has been made to solve the above problems, and the invention according to claim 1 is capable of supplying water through a water supply path via a vapor compression heat pump capable of changing output and a condenser of the heat pump. And a water supply tank capable of supplying water through a replenishment water channel without passing through the condenser, and controlling the output of the heat pump so as to maintain the water level in the water supply tank at a set water level. This is a water heating system.

  According to the first aspect of the present invention, the output of the heat pump is controlled so that the water level in the water supply tank is maintained at the set water level. Specifically, the lower the set water level, the higher the output of the heat pump, while the higher the set water level, the lower the output of the heat pump, thereby continuously changing the amount of hot water discharged from the heat pump. In this way, the hot water can be manufactured by quickly following the usage load of the hot water in the water supply tank.

  Furthermore, the invention according to claim 2 controls the presence or absence of water supply to the water supply tank via the water supply path and the output of the heat pump based on the water level of the water supply tank, and the output via the water supply path. During the water supply to the water supply tank, the amount of water flow is adjusted so as to maintain the water temperature on the outlet side of the condenser at a set temperature, and the compressor of the heat pump is adjusted so as to maintain the water level in the water supply tank at the set water level. The feed water heating system according to claim 1, wherein inverter control is performed.

  According to the second aspect of the present invention, water supply to the water supply tank via the water supply channel is set in the water supply tank by adjusting the water flow rate so that the water temperature on the outlet side of the condenser is maintained at the set temperature. Hot water of temperature can be supplied. In this case, the water supply flow rate to the water supply tank via the water supply path is increased or decreased in accordance with the increase or decrease of the output of the heat pump. Therefore, the lower the water level in the water supply tank, the higher the output of the heat pump can be increased, and the amount of hot water can be increased. On the other hand, the higher the water level in the water supply tank, the lower the output of the heat pump can be reduced. . In this way, the hot water can be manufactured by quickly following the usage load of the hot water in the water supply tank.

  ADVANTAGE OF THE INVENTION According to this invention, the amount of hot water discharged from a heat pump can be changed continuously based on the water level in a water supply tank, and hot water can be manufactured rapidly following the usage load of the hot water in a water supply tank.

It is the schematic which shows one Example of the feed water heating system of this invention. It is a figure which shows an example of the control method of the feed water heating system based on the water level of a feed water tank.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view showing an embodiment of a feed water warming system 1 of the present invention.

  The feed water warming system 1 of the present embodiment is a system that can heat the feed water to the feed water tank 3 of the boiler 2 with the heat pump 4. The feed water tank 3 that stores the feed water to the boiler 2, and the feed water tank 3 A replenishment water tank 5 for storing water supply, a heat pump 4 for heating water supplied from the replenishment water tank 5 to the water supply tank 3, and a heat source water tank for storing heat source water (for example, waste hot water) as a heat source of the heat pump 4. 6.

  The boiler 2 is a steam boiler, and heats the feed water from the feed water tank 3 into steam. The boiler 2 is typically adjusted in combustion quantity so as to maintain the desired steam pressure. Further, the boiler 2 is controlled by a pump 7 provided in the water supply path from the water supply tank 3 to the boiler 2 or in the boiler so as to maintain the water level in the can as desired. The steam from the boiler 2 is sent to various steam use facilities (not shown), but drain (condensed water of steam) from the steam use facility may be returned to the water supply tank 3.

  The water supply tank 3 can be supplied with water from the make-up water tank 5 via the heat pump 4 through the water supply path 8 and can be supplied through the make-up water path 9 without going through the heat pump 4. By controlling the operation of the water supply pump 10 provided in the water supply path 8 and the makeup water pump 11 provided in the makeup water path 9, via either one or both of the water supply path 8 and the makeup water path 9, Water can be supplied from the makeup water tank 5 to the water supply tank 3.

  In the present embodiment, the feed water pump 10 can control the rotation speed by an inverter. By changing the rotation speed of the water supply pump 10, the water supply flow rate to the water supply tank 3 through the water supply path 8 can be adjusted. On the other hand, the makeup water pump 11 is on / off controlled in this embodiment.

  The makeup water tank 5 stores water supplied to the water supply tank 3. In this embodiment, soft water is used as the water supply to the makeup water tank 5. That is, the soft water from which the water hardness has been removed by the water softener (not shown) is supplied to the makeup water tank 5 and stored. By controlling the water supply from the water softener based on the water level of the makeup water tank 5, the water level of the makeup water tank 5 is maintained as desired.

  The heat pump 4 is a vapor compression heat pump, and includes a compressor 12, a condenser 13, an expansion valve 14, and an evaporator 15 that are sequentially connected in an annular shape. The compressor 12 compresses the gas refrigerant to a high temperature and a high pressure. The condenser 13 condenses and liquefies the gas refrigerant from the compressor 12. Furthermore, the expansion valve 14 allows the liquid refrigerant from the condenser 13 to pass therethrough, thereby reducing the pressure and temperature of the refrigerant. The evaporator 15 evaporates the refrigerant from the expansion valve 14.

  Therefore, in the heat pump 4, the refrigerant takes heat from the outside and vaporizes in the evaporator 15, while the refrigerant dissipates heat to the outside and condenses in the condenser 13. In this embodiment, the heat pump 4 draws heat from the heat source water in the evaporator 15 and heats the water in the water supply channel 8 in the condenser 13.

  It is preferable that the heat pump 4 further includes a supercooler 16 between the condenser 13 and the expansion valve 14. The subcooler 16 is an indirect heat exchanger between the refrigerant from the condenser 13 to the expansion valve 14 and the feed water to the condenser 13. The subcooler 16 can supercool the refrigerant from the condenser 13 to the expansion valve 14 by supplying water to the condenser 13, and can supply the refrigerant to the condenser 13 by the refrigerant from the condenser 13 to the expansion valve 14. The water supply can be heated. The refrigerant of the heat pump 4 preferably releases latent heat in the condenser 13 and releases sensible heat in the subcooler 16.

  That is, in the condenser 13, the gas refrigerant is condensed into a liquid refrigerant, and the liquid refrigerant is supplied to the subcooler 16, and the liquid refrigerant is further cooled (supercooled) in the subcooler 16. By separating heat exchangers for refrigerant condensation and supercooling, the heat exchanger can be easily designed, the heat exchanger can be reduced in size with a simple structure, and costs can be reduced. In addition, a general-purpose heat exchanger can be used.

  In addition, in the heat pump 4, an accumulator is installed on the inlet side of the compressor 12, an oil separator is installed on the outlet side of the compressor 12, or the outlet side of the condenser 13 (the condenser 13 and the subcooler 16 A receiver may be installed between the two).

  By the way, the output of the heat pump 4 can be changed. For example, the output of the heat pump 4 can be changed by changing the power supply frequency of the motor of the compressor 12 and thus the rotational speed by an inverter.

  It is preferable that the feed water heating system 1 further includes a waste heat recovery heat exchanger 17. The waste heat recovery heat exchanger 17 is an indirect heat exchanger for supplying water to the subcooler 16 and heat source water after passing through the evaporator 15. Therefore, the water in the water supply channel 8 is passed through the waste heat recovery heat exchanger 17, the subcooler 16, and the condenser 13 in order. On the other hand, the heat source water in the heat source water tank 6 is passed through the evaporator 15 via the heat source supply path 18 and then passed to the waste heat recovery heat exchanger 17.

  The heat source water tank 6 stores heat source water as a heat source of the heat pump 4. The heat source water is, for example, waste hot water (hot water discharged from a factory or the like). The heat source water tank 6 is provided with a heat source water supply path 19 and an overflow path 20 for overflowing a predetermined amount or more of water.

  The heat source water in the heat source water tank 6 is passed through the evaporator 15 of the heat pump 4 via the heat source supply path 18 and then passed through the waste heat recovery heat exchanger 17. The heat source supply path 18 is provided with a heat source supply pump 21 on the upstream side of the evaporator 15. By operating the heat source supply pump 21, the heat source water from the heat source water tank 6 is discarded with the evaporator 15. The heat recovery heat exchanger 17 can be sequentially passed.

  By passing the heat source water through the waste heat recovery heat exchanger 17 after passing the evaporator 15 first, compared with the case where the heat source water is passed through the evaporator 15 after passing the waste heat recovery heat exchanger 17 first. In addition, the evaporation temperature (that is, the evaporation pressure) of the refrigerant in the evaporator 15 can be increased, the pressure ratio of the compressor 12 can be reduced, and energy can be saved.

  In the water supply path 8, a tapping temperature sensor 22 is provided on the outlet side of the condenser 13. The tapping temperature sensor 22 detects the water temperature after passing through the condenser 13. The feed water pump 10 is controlled based on the temperature detected by the hot water temperature sensor 22. Here, the feed water pump 10 is inverter-controlled so that the temperature detected by the tapping temperature sensor 22 is maintained at a set temperature (tapping temperature setting value). That is, the flow rate of water supplied to the water supply tank 3 through the water supply path 8 is adjusted so that the temperature detected by the tapping temperature sensor 22 is maintained at the set temperature.

  The water supply tank 3 is provided with a water level detector 23. The configuration of the water level detector 23 is not particularly limited. In the present embodiment, the water level detector 23 is an analog water level detector that can obtain an output corresponding to the water level. That is, the water level detector 23 continuously detects the water level in the water supply tank 3. Specifically, a water pressure type water level detector using the fact that the water pressure changes according to the water level in the water supply tank 3 can be used, but a pressure sensor can be used instead. Alternatively, a capacitive water level detector can be used.

  The heat source water tank 6 is provided with a water level detector 24 in order to confirm the presence or absence of the heat source water. The configuration of the water level detector 24 is not particularly limited, but is an electrode type water level detector in the present embodiment. In this case, the low water level detection electrode rod 25 is inserted into the heat source water tank 6 to monitor whether the water level of the heat source water is below the setting.

  The heat source water tank 6 is provided with a heat source temperature sensor 26 that detects the temperature of the heat source water. However, the heat source temperature sensor 26 may be provided in the heat source supply path 18 from the heat source water tank 6 to the evaporator 15.

  Next, control (operation method) of the feed water heating system 1 of the present embodiment will be described. A series of control described below is automatically performed using a controller (not shown).

  FIG. 2 is a diagram illustrating an example of a control method of the feed water heating system 1 based on the water level of the feed water tank 3. As shown in this figure, based on the water level of the water supply tank 3, the heat pump 4 (especially its compressor 12), the water supply pump 10, and the makeup water pump 11 are controlled.

  The water supply tank 3 can be supplied with water through the water supply channel 8 and can also be supplied through the replenishment water channel 9, but is usually controlled so that water supply through the water supply channel 8 is given priority. Is preferred. That is, the water supply through the water supply channel 8 is controlled so as to maintain the water level of the water supply tank 3 within the set range. However, if the water level of the water supply tank 3 cannot maintain the set range, the water supply through the supply water channel 9 It is preferable to supply water to the water supply tank 3.

  Specifically, in this embodiment, control is performed as follows. First, when the water level in the water supply tank 3 is lower than the lower limit water level, the water supply pump 10 is operated, whereas when the water level is higher than the upper limit water level, the water supply pump 10 is stopped. During the operation of the water supply pump 10, the output of the heat pump 4 is adjusted so that the water level in the water supply tank 3 falls within the set range (between the upper limit water level and the lower limit water level).

  If the water level of the water supply tank 3 cannot be recovered even if the water supply pump 10 is operated and falls below a predetermined lower supply water start level, the water supply pump 11 is operated to supply water via the supply water channel 9. Supply water to tank 3. Thereby, when the water level of the water supply tank 3 recovers and the water level of the water supply tank 3 exceeds the makeup water stop water level, the makeup water pump 11 is stopped and the water supply via the makeup water channel 9 is stopped. In the illustrated example, the makeup water stop water level is the same as the lower limit water level, but may be a water level different from the lower limit water level.

  During the water supply through the water supply path 8, the heat pump 4 is operated and the heat source supply pump 21 is operated. The heat pump 4 is switched between operation and stop depending on whether or not the compressor 12 is activated. The output of the heat pump 4 is controlled based on the water level of the water supply tank 3. In the present embodiment, the output of the heat pump 4 is adjusted so that the water in the water supply tank 3 is maintained at a set water level (target water level). The lower the set water level, the higher the output of the heat pump 4, while the higher the set water level, the lower the output of the heat pump 4. Below the lower limit water level, the heat pump 4 operates at full load (100% output), and the output of the heat pump 4 gradually decreases as it goes from the lower limit water level to the upper limit water level, and at above the upper limit water level, the heat pump 4 stops (0% output) ) Such control may be performed by inverter control of the motor of the compressor 12 based on the detection signal of the water level detector 23.

  During the water supply through the water supply path 8, the water supply pump 10 is inverter-controlled in rotation speed so that the temperature detected by the tapping temperature sensor 22 is maintained at the set temperature. As a result, the water supply flow rate to the water supply tank 3 through the water supply path 8 is increased or decreased according to the increase or decrease of the output of the heat pump 4. That is, as the water level in the water supply tank 3 is lower, the output of the heat pump 4 can be increased and the amount of hot water discharged can be increased. On the other hand, as the water level in the water supply tank 3 is higher, the output of the heat pump 4 is decreased. Can be reduced. In this way, the hot water can be manufactured by quickly following the usage load of the hot water in the water supply tank 3.

  When the heat pump 4 is operated to supply water from the make-up water tank 5 to the water supply tank 3 via the water supply path 8, the water supplied from the make-up water tank 5 is used as the waste heat recovery heat exchanger 17, the supercooler 16, and the condenser. 13 is gradually heated and supplied to the water supply tank 3 at a set temperature. Compared with the case where water is circulated between the water supply tank 3 and the heat pump 4 (condenser 13), the water supply is heated by a single pass (once through) from the makeup water tank 5 to the water supply tank 3. The temperature difference of the feed water before and after passing through the heat pump 4 can be secured, and the coefficient of performance (COP) of the heat pump 4 can be improved. Moreover, each heat exchanger can also be comprised compactly.

  Further, during operation of the heat pump 4, that is, water supply to the water supply tank 3 through the water supply path 8, the water temperature of the heat source water tank 6 is monitored by the heat source temperature sensor 26, and the output of the heat pump 4 is adjusted based on the temperature. May be. The higher the temperature of the heat source water as the heat source of the heat pump 4, the lower the output of the heat pump 4. By adjusting the output of the heat pump 4 in consideration of the temperature of the heat source water, the water supply flow rate to the water supply tank 3 via the water supply path 8 can be stabilized regardless of the temperature change of the heat source water.

  Further, when the water level of the heat source water tank 6 falls during the operation of the heat pump 4 and the low water level detection electrode rod 25 does not detect the water level, the operation of the heat pump 4 is stopped, and the heat source supply pump 21 is stopped and the evaporator The supply of heat source water to 15 may be stopped. This prevents the heat pump 4 from being wasted. Similarly, during operation of the heat pump 4 (that is, during water supply control to the water supply tank 3 through the water supply path 8), if the amount of water supplied through the water supply path 8 falls below the setting, the operation of the heat pump 4 is stopped. While stopping, it is preferable to stop the heat source supply pump 21 to stop the supply of the heat source water to the evaporator 15.

  The feed water warming system 1 of the present invention is not limited to the configuration of the above embodiment, and can be changed as appropriate. In particular, if the output of the heat pump 4 is controlled so as to maintain the water level in the water supply tank 3 at a set water level (within the set range), other configurations can be changed as appropriate.

  Moreover, in the said Example, in order to adjust the water supply flow volume to the water supply tank 3 via the water supply path 8, the water supply pump 10 was inverter-controlled, However, The water supply pump 10 was provided in the water supply path 8 while performing on-off control. The opening degree of the valve may be adjusted. That is, as long as the flow rate of the water supply through the water supply path 8 can be adjusted based on the temperature detected by the hot water temperature sensor 22, the flow rate adjustment method can be changed as appropriate.

  Further, the heat pump 4 is not limited to a single stage, and may be a plurality of stages. When the heat pump 4 has a plurality of stages, adjacent stage heat pumps may be connected using an indirect heat exchanger, or may be connected using a direct heat exchanger (intercooler). In the latter case, an intermediate cooler that receives the refrigerant from the compressor of the lower heat pump and the refrigerant from the expansion valve of the upper heat pump and directly exchanges heat between the two refrigerants is provided. And the evaporator of the upper heat pump. As described above, the multi-stage (multi-stage) heat pump includes a single-stage multi-stage heat pump, a multi-element (multi-element) heat pump, or a combination thereof.

  In addition, if water can be supplied to the water supply tank 3 through the water supply path 8 via the condenser 13 and water can be supplied through the replenishment water path 9 without going through the condenser 13, the specifics of the water supply path 8 and the replenishment water path 9 are specified. The configuration is not limited to the configuration of the above embodiment and can be changed as appropriate. For example, in the above-described embodiment, the water supply channel 8 and the supply water channel 9 are provided in parallel so as to connect the supply water tank 5 and the water supply tank 3, respectively, but one end portion of the water supply channel 8 and the supply water channel 9 ( One or both of the end portion on the make-up water tank 5 side and the other end portion (the end portion on the water supply tank 3 side) may be a common conduit. In other words, one end of the makeup water channel 9 may be provided so as to branch from the water supply channel 8 instead of being connected to the makeup water tank 5, and the other end of the makeup water channel 9 is connected to the water supply tank 3. Instead, it may be provided so as to join the water supply path 8 before the water supply tank 3. When one end portion of the replenishment water channel 9 is provided so as to branch from the water supply channel 8 instead of being connected to the replenishment water tank 5, the water supply pump 10 is provided in the water supply channel 8 downstream from the branching unit, while the replenishment water channel 9 may be provided with a supplementary water pump 11, but a pump is provided only in the common pipe upstream of the branching portion, and the valves provided in the water supply passage 8 and / or the supplementary waterway 9 downstream of the branching portion are opened. By adjusting the degree, the flow rate through the water supply channel 8 and the replenishment channel 9 may be adjusted.

  Moreover, in the said Example, although the supplementary water tank 5 was installed in order to store the water supply to the water supply tank 3, installation of the supplementary water tank 5 may be abbreviate | omitted by the case, and the water supply path 8 and the supplement may be directly from a water supply source. Water may be passed through the water channel 9.

  Moreover, in the said Example, although it was made possible to supply water from the makeup water tank 5 to the water supply tank 3 via the water supply channel 8 and / or the makeup water channel 9, these water supply may be performed directly from a water softener. For example, in FIG. 1, instead of omitting the installation of the water supply pump 10 by connecting the base ends of the water supply channel 8 and the makeup water channel 9 together to the water softener, the opening of an electric valve (motor valve) provided in the water supply channel 8 Instead of adjusting the degree and omitting the installation of the makeup water pump 11, the opening and closing of the electromagnetic valve provided in the makeup water channel 9 may be controlled.

  Moreover, although the said Example demonstrated the system which can heat the water supply to the feed water tank 3 of the boiler 2 with the heat pump 4, the utilization place of the stored water of the feed water tank 3 is not restricted to the boiler 2, and can be changed suitably. is there. In some cases, the replenishment water tank 5 and the replenishment water channel 9 may be omitted.

  Moreover, although the said Example demonstrated the example using heat-source water as a heat source of the heat pump 4, as a heat-source fluid of the heat pump 4, not only heat-source water but various fluids, such as air and waste gas, can be used. However, while the heat source fluid gives heat (sensible heat) to the refrigerant of the heat pump 4 in the evaporator 15, the heat source fluid itself falls in temperature, and then gives heat (sensible heat) to the feed water in the waste heat recovery heat exchanger 17. The fluid itself with a temperature drop is preferable.

  Furthermore, in the said Example, although the compressor 12 of the heat pump 4 was driven by the electric motor, the drive source of the compressor 12 is not ask | required in particular. For example, the compressor 12 may be driven by a steam motor (steam engine) that generates power using steam instead of or in addition to the electric motor, or may be driven by a gas engine.

DESCRIPTION OF SYMBOLS 1 Supply water heating system 2 Boiler 3 Supply water tank 4 Heat pump 5 Supply water tank 6 Heat source water tank 8 Supply water path 9 Supply water path 10 Supply water pump 11 Supply water pump 12 Compressor 13 Condenser 14 Expansion valve 15 Evaporator 16 Supercooler 17 Waste heat recovery heat exchanger 18 Heat source supply path 22 Hot water temperature sensor 23 Water level detector

Claims (2)

A vapor compression heat pump with variable output,
A water supply tank capable of supplying water by a water supply path via a condenser of the heat pump, and having a water supply tank capable of supplying water by a replenishment water path without passing through the condenser,
An output of the heat pump is controlled so as to maintain a water level in the water supply tank at a set water level. Based on the water level of the water supply tank, the presence or absence of water supply to the water supply tank via the water supply path, and the output of the heat pump are controlled,
During water supply to the water supply tank via the water supply path, the water flow rate is adjusted so as to maintain the water temperature on the outlet side of the condenser at a set temperature, and the water level in the water supply tank is maintained at the set water level. The feed water heating system according to claim 1, wherein the compressor of the heat pump is inverter-controlled.

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