JP2015055461A - Feed water heating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feed water heating system that enables heating of feed water in an optimal condition in accordance with a temperature of a heat source fluid while protecting a compressor.SOLUTION: A heat pump 4 pumps up heat from heat source fluid passing through an evaporator 15, and heats water passing through a condenser 13. Water can be supplied to a feed water tank 3 through a feed water passage 8 via the condenser 13. A waste heat recovery heat exchanger 17 exchanges heat between water in the feed water passage 8 on the upstream side of the condenser 13 and the heat source fluid that has passed through the evaporator 15. At cold start, after supply of the heat source fluid to the evaporator 15 is started, if a temperature of the heat source fluid to the evaporator 15 is lower than a lower limit temperature, the heat pump 4 is stopped. When the temperature of the heat source fluid reaches the lower limit temperature or higher, the heat pump 4 is started.

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 (3) of a boiler (2) using a heat pump (4) is known. In this system, water supplied to the water supply tank (3) via the water supply channel (8) is passed through the waste heat recovery heat exchanger (12), the supercooler (17), and the condenser (14) in this order. The waste heat recovery heat exchanger (12) is an indirect heat exchanger for supplying water to the water supply tank (3) through the water supply channel (8) and the heat source fluid after passing through the evaporator (16). The cooler (17) is an indirect heat exchanger for supplying water to the water supply tank (3) via the water supply channel (8) and refrigerant from the condenser (14) to the expansion valve (15). While supplying water to the water supply tank (3) through the water supply channel (8), operating the heat pump (4), and maintaining the outlet side water temperature of the condenser (14) of the heat pump (4) at the target temperature, The feed water flow rate to the feed water tank (3) through the feed water channel (8) is adjusted by inverter control of the feed water pump (10).

Japanese Patent No. 5263421

  However, especially during cold start, the heat pump refrigerant is not heated, and the temperature of the heat source fluid may be lowered to room temperature (particularly in winter). In such a case, if the heat pump is operated due to the condensation of the refrigerant in the evaporator, the compressor may be damaged.

  On the other hand, if the temperature of the heat source fluid is high, depending on the temperature of the heat source fluid, it may be sufficient to exchange heat between the water supply and the heat source fluid in the waste heat recovery heat exchanger, and there is a case where it is not necessary to operate the heat pump.

  Further, when the temperature of the heat source fluid increases, the compressor may be damaged unless the heat pump is stopped. However, in such a case, if the entire feed water heating system is always stopped, heat recovery from the high-temperature heat source fluid cannot be achieved.

  Furthermore, when adjusting the feed water flow rate to the feed water tank via the feed water path so that the outlet water temperature of the condenser is maintained at the target temperature, regardless of whether the heat pump is stopped or not, While the heat pump is stopped, the water supply flow rate to the water supply tank via the water supply channel is reduced, and the amount of heat recovered from the heat source fluid is also reduced.

  Therefore, the problem to be solved by the present invention is to provide a feed water heating system capable of heating feed water under optimum conditions according to the temperature of the heat source fluid while protecting the compressor. It is also an object of the present invention to provide a feed water heating system that can secure a feed water flow rate to a feed water tank through a feed water channel to a certain level or more and can recover heat from a heat source fluid.

  The present invention has been made to solve the above problems, and the invention according to claim 1 is characterized in that a compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in an annular manner to circulate a refrigerant, and the evaporation. A heat pump that draws heat from the heat source fluid that is passed through the condenser and heats the water that is passed through the condenser; a water supply tank that is capable of supplying water through the condenser through a water supply path; and an upstream side of the condenser A waste heat recovery heat exchanger for exchanging heat between the water in the water supply channel and the heat source fluid after passing through the evaporator, and after starting the supply of the heat source fluid to the evaporator at the time of cold start, When the heat source fluid temperature to the evaporator is lower than the lower limit temperature, the heat pump is stopped, and when the temperature becomes equal to or higher than the lower limit temperature, the heat pump is started.

  According to the first aspect of the present invention, the compressor can be protected by stopping the heat pump until the temperature of the heat source fluid to the evaporator becomes equal to or higher than the lower limit temperature at the time of cold start.

  According to a second aspect of the present invention, once the heat pump is started, the heat pump is supplied even when the heat source fluid temperature to the evaporator becomes lower than the lower limit temperature during the water supply to the water supply tank via the water supply channel. The feed water heating system according to claim 1, wherein the operation is continued.

  According to the second aspect of the present invention, once the heat pump is started, the system can be operated stably by continuing the operation of the heat pump even if the heat source fluid temperature to the evaporator becomes lower than the lower limit temperature. Hot water can be obtained. Note that once the heat pump is started, the refrigerant of the heat pump is warmed more than when the heat pump is started, so there is no risk of damaging the compressor even if the operation of the heat pump is continued.

  According to a third aspect of the present invention, if the heat source fluid temperature to the evaporator is lower than a set temperature that is higher than the lower limit temperature during water supply to the water supply tank via the water supply channel, the heat pump The water supply flow rate to the water supply tank via the water supply path is adjusted so that the outlet side water temperature of the condenser is maintained at the first target temperature in a state where the water supply is operated, and the water supply via the water supply path is adjusted. When the temperature of the heat source fluid to the evaporator becomes equal to or higher than a set temperature during the water supply to the tank, the outlet water temperature of the condenser is lower than the first target temperature with the heat pump stopped. The feed water warming system according to claim 1 or 2, wherein a feed water flow rate to the feed water tank via the feed water channel is adjusted so as to be maintained at the same time.

  According to the third aspect of the present invention, when the heat source fluid temperature to the evaporator is lower than the set temperature, the outlet water temperature of the condenser is maintained at the first target temperature while the heat pump is operated. Regardless of the water temperature of the water supply source or the temperature of the heat source fluid, hot water having a desired temperature can be obtained by adjusting the flow rate of the water supply to the water supply tank via the water supply channel. On the other hand, when the heat source fluid temperature to the evaporator is equal to or higher than the set temperature, the heat pump is stopped, so that the compressor can be protected. However, even in that case, heat recovery from the heat source fluid can be achieved by exchanging heat between the water supply and the heat source fluid in the waste heat recovery heat exchanger. In addition, by switching the control target temperature of the outlet water temperature of the condenser to the second target temperature lower than the first target temperature, the water supply flow rate to the water supply tank via the water supply channel is ensured to some extent, and the heat source Heat recovery from the fluid can be effectively achieved.

  According to a fourth aspect of the present invention, during adjustment of the feed water flow rate to the feed water tank via the feed water channel so as to maintain the outlet side water temperature of the condenser at the second target temperature, When the heat source fluid temperature is less than the set temperature for a set time, the water supply via the water supply path is operated so as to maintain the outlet side water temperature of the condenser at the first target temperature by operating the heat pump. 4. The feed water heating system according to claim 3, wherein the feed water heating system is switched to control for adjusting a feed water flow rate to the tank.

  According to the fourth aspect of the present invention, when the heat source fluid temperature to the evaporator is lowered to a predetermined level, it is possible to return from the hot water temperature constant control in which the heat pump is stopped to the hot water temperature constant control in which the heat pump is operated.

  According to a fifth aspect of the present invention, while adjusting the feed water flow rate to the feed water tank via the feed water channel so as to maintain the outlet side water temperature of the condenser at the second target temperature, When the heat source fluid temperature becomes lower than a predetermined temperature lower than a set temperature, the heat pump is operated to pass the water supply path so as to maintain the outlet side water temperature of the condenser at the first target temperature. The feed water heating system according to claim 3, wherein the control is switched to control for adjusting a feed water flow rate to the feed water tank.

  According to the fifth aspect of the present invention, when the heat source fluid temperature to the evaporator is lowered to a predetermined level, it is possible to return from the hot water temperature constant control in which the heat pump is stopped to the hot water temperature constant control in which the heat pump is operated.

  According to a sixth aspect of the present invention, when the heat source fluid temperature to the evaporator becomes equal to or higher than the upper limit temperature higher than the set temperature during water supply to the water supply tank via the water supply channel, the heat pump is stopped. The supply water heating system according to any one of claims 3 to 5, wherein the supply of the heat source fluid to the evaporator is also stopped.

  According to the sixth aspect of the present invention, when the heat source fluid temperature to the evaporator becomes equal to or higher than the upper limit temperature, the heat pump is stopped and the supply of the heat source fluid to the evaporator is also stopped. Protection can be achieved.

  Furthermore, in the invention described in claim 7, the presence or absence of water supply to the water supply tank via the water supply path is switched based on the water level of the water supply tank. It is a water supply heating system as described in an item.

  According to invention of Claim 7, the water level in a water supply tank can be maintained as desired by controlling the water supply to a water supply tank via a water supply path based on the water level of a water supply tank.

  ADVANTAGE OF THE INVENTION According to this invention, the feed water heating system which can heat feed water on optimal conditions according to the temperature of a heat source fluid is achieved, protecting a compressor. In addition, it is possible to secure a water supply flow rate to the water supply tank via the water supply channel to a certain level or more to recover heat from the heat source fluid.

It is the schematic which shows one Example of the feed water heating system of this invention.

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. Moreover, the pump 7 provided in the inside of the water supply path from the water supply tank 3 to the boiler 2, or the boiler 2 is controlled so that the boiler 2 may maintain the water level in a can body 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. Alternatively, drain from the steam using facility may be supplied to the heat source water tank 6.

  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 channel 8 and the makeup water pump 11 provided in the makeup water channel 9, makeup water is supplied via one or both of the water supply channel 8 and the makeup water channel 9. Water can be supplied from the 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 supercooler 16 is an indirect heat exchanger between the water in the water supply channel 8 upstream from the condenser 13 and the refrigerant from the condenser 13 to the expansion valve 14. 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 heat pump 4 may be capable of changing its output. 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. However, in the following, an example in which the heat pump 4 is operated at a constant output while the power frequency of the motor of the compressor 12 is maintained constant will be described.

  The feed water heating system 1 of the present embodiment further includes a waste heat recovery heat exchanger 17. This waste heat recovery heat exchanger 17 is an indirect heat exchanger between the water in the water supply channel 8 upstream of the subcooler 16 and the 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 through the heat source supply path 18 and then passed to 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.

  The water supply tank 3 is provided with a water level detector 22. The configuration of the water level detector 22 is not particularly limited, but is an electrode type water level detector in the present embodiment. In this case, a plurality of electrode rods 23 to 26 having different lengths are inserted and held in the water supply tank 3 with their lower end portions having different height positions. In this embodiment, in addition to the water supply start electrode rod 23 and the water supply stop electrode rod 24 for controlling the water supply pump 10, the makeup water start electrode rod 25 and the makeup water stop electrode rod 26 for controlling the makeup water pump 11 are provided in the water supply tank 3. Has been inserted. At this time, although the details will be described later, the water supply tank is made by lowering the height position of the lower end portion in the order of the water supply stop electrode rod 24, the makeup water stop electrode rod 26, the water supply start electrode rod 23, and the makeup water start electrode rod 25. 3 is inserted.

  Each electrode rod 23-26 detects the presence or absence of the water level in a lower end part by whether the lower end part is immersed in water. In the following, the water level detected by the water supply start electrode rod 23 is the water supply start water level H1, the water level detected by the water supply stop electrode rod 24 is the water supply stop water level H2, the water level detected by the makeup water start electrode rod 25 is the makeup water start water level H3, The water level detected by the makeup water stop electrode rod 26 is referred to as a makeup water stop water level H4.

  The heat source water tank 6 is provided with a water level detector 27 for confirming the presence or absence of the heat source water. The configuration of the water level detector 27 is not particularly limited. In the present embodiment, the water level detector 27 is an electrode type water level detector. In this case, the low water level detection electrode rod 28 is inserted into the heat source water tank 6 to monitor whether the water level of the heat source water is lower than the setting.

  In the water supply path 8, a hot water temperature sensor 29 is provided on the outlet side of the condenser 13. The hot water temperature sensor 29 detects the water temperature after passing through the condenser 13. Based on the temperature detected by the hot water temperature sensor 29, the feed water pump 10 is controlled. Here, the feed water pump 10 is inverter-controlled so that the temperature detected by the tapping temperature sensor 29 is maintained at the target temperature. Thereby, the flow rate of water supplied to the water supply tank 3 via the water supply path 8 is adjusted so that the temperature detected by the tapping temperature sensor 29 is maintained at the target temperature.

  A heat source temperature sensor 30 is provided in the heat source supply path 18 on the inlet side of the evaporator 15. The heat source temperature sensor 30 detects the temperature of the heat source water supplied to the evaporator 15. However, the heat source temperature sensor 30 may be provided in the heat source water tank 6 according to circumstances. Although details will be described later, based on the temperature detected by the heat source temperature sensor 30, the heat pump 4 (more specifically, the compressor 12) can be started and stopped and the target temperature can be changed.

  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).

  Water supply to the water supply tank 3 is performed by controlling the water supply pump 10 and the makeup water pump 11 based on the detection signal of the water level detector 22 provided in the water supply tank 3. That is, the water supply to the water supply tank 3 through the water supply path 8 starts when the water level in the water supply tank 3 falls below the water supply start water level H1, and stops when the water level exceeds the water supply stop water level H2 higher than the water supply start water level H1. . Further, the water supply to the water supply tank 3 via the makeup water channel 9 starts when the water level in the water supply tank 3 falls below the makeup water start water level H3, and exceeds the makeup water stop water level H4 higher than the makeup water start water level H3. And stop. Here, the makeup water start water level H3 is set lower than the feed water start water level H1, and the makeup water stop water level H4 is set higher than the feed water start water level H1 but lower than the feed water stop water level H2.

  With this configuration, if the water supply stop electrode rod 24 detects the water level, the water supply pump 10 is stopped and the makeup water pump 11 is also stopped, assuming that the water level in the water supply tank 3 is sufficient. doing. When the water level in the water supply tank 3 drops due to the water supply from the water supply tank 3 to the boiler 2 and the water supply start electrode rod 23 no longer detects the water level, the water supply pump 10 is operated. Thus, water is supplied to the water supply tank 3 through the water supply path 8, but when the water supply stop electrode rod 24 detects the water level, the water supply pump 10 is stopped. On the other hand, when the water supply pump 10 is operated, the water level of the water supply tank 3 cannot be recovered, the water level of the water supply tank 3 is further lowered, and the makeup water start electrode rod 25 no longer detects the water level, the makeup water pump 11 is also activated. Let As a result, water is supplied to the water supply tank 3 also through the supply water channel 9, but when the water level in the water supply tank 3 recovers and the supply water stop electrode rod 26 detects the water level, the supply water pump 11 is stopped, When the water level recovers and the water supply stop electrode rod 24 detects the water level, the water supply pump 10 is stopped. In addition, the water supply pump 10 is operated and the water supply to the water supply tank 3 through the water supply path 8 and the heat source supply pump 21 are also operated.

  In this embodiment, the makeup water stop water level H4 is set higher than the feed water start water level H1 but lower than the feed water stop water level H2. As a result, the water level region between the water supply start water level H1 and the water supply stop water level H2 and the water level region between the makeup water start water level H3 and the makeup water stop water level H4 partially overlap each other. Therefore, it is easy to ensure the water level difference between the water supply start water level H1 and the water supply stop water level H2, and the water level difference between the makeup water start water level H3 and the makeup water stop water level H4. In connection with this, the frequency | count of start / stop of the feed water pump 10 and the makeup water pump 11 can be decreased compared with a prior art. Furthermore, since the makeup water stop water level H4 is relatively high as compared with the prior art, the water supply speed to the water supply tank 3 can be increased, and a relatively large amount of water can be stored in the water supply tank 3. Therefore, there is no fear that the amount of water stored in the water supply tank 3 will be insufficient, and priority can be given to the operation of the most important boiler 2 and its steam using equipment. Moreover, the time until the water supply tank 3 is filled with water from an empty state can be shortened.

  By the way, it is preferable to set the water level difference between the water supply start water level H1 and the makeup water start water level H3 smaller than the water level difference between the water supply start water level H1 and the water supply stop water level H2. By bringing the water supply start water level H1 and the makeup water start water level H3 close to each other, both the water supply through the water supply channel 8 and the water supply through the makeup water channel 9 can be easily performed. Thereby, the water supply speed to the water supply tank 3 can be increased.

  As will be described later, the heat pump 4 operates in a predetermined case. The heat pump 4 is switched between operation and stop depending on whether or not the compressor 12 is activated. During the operation of the heat pump 4, the compressor 12 is maintained at a constant power output frequency and a constant power output.

  During operation, the feed water pump 10 is inverter-controlled for rotation speed so as to maintain the temperature detected by the tapping temperature sensor 29 at the target temperature. As will be described later, the target temperature is changed according to the situation.

  As described above, in the feed water warming system 1 of the present embodiment, water supply to the water supply tank 3 through the water supply path 8 is controlled based on the water level in the water supply tank 3. During the water supply to the tank 3, the heat source fluid temperature to the evaporator 15 is monitored by the heat source temperature sensor 30, and when the temperature becomes equal to or higher than the set temperature, the heat pump 4 is preferably stopped. Even in that case, as long as the water supply condition based on the water level in the water supply tank 3 is satisfied, water is supplied to the water supply tank 3 through the water supply path 8.

  More specifically, in the present embodiment, control is performed as follows. That is, if the temperature detected by the heat source temperature sensor 30 is lower than a set temperature (for example, 60 ° C.) during water supply to the water supply tank 3 via the water supply path 8, The feedwater pump 10 is inverter-controlled to maintain the detected temperature at the first target temperature (for example, 75 ° C.), and the feedwater flow rate to the feedwater tank 3 through the feedwater channel 8 is adjusted (first control). Here, the first target temperature is higher than the set temperature.

  During the first control, when the detected temperature of the heat source temperature sensor 30 becomes a set temperature (for example, 60 ° C.) or higher, the control is switched to the second control. In the second control, the heat pump 4 is stopped. Even in such a case, as long as the water supply condition based on the water level in the water supply tank 3 is satisfied, the water is supplied to the water supply tank 3 through the water supply path 8, but it is preferable to lower the control target temperature of the outlet side water temperature of the condenser 13. . That is, the feed water pump 3 is controlled by the inverter so that the temperature detected by the tapping temperature sensor 29 is maintained at a second target temperature (for example, 60 ° C.) lower than the first target temperature. Adjust the water supply flow rate to. Here, the second target temperature is the same temperature as the set temperature, but may be a temperature lower than the set temperature in some cases.

  Thus, if the heat source fluid temperature to the evaporator 15 is lower than the set temperature, the water supply path 8 is maintained so that the outlet side water temperature of the condenser 13 is maintained at the first target temperature while the heat pump 4 is operated. Regardless of the water temperature of the water supply source or the temperature of the heat source fluid, hot water having a desired temperature can be obtained by adjusting the flow rate of the water supply to the water supply tank 3 via the. On the other hand, when the heat source fluid temperature to the evaporator 15 becomes equal to or higher than the set temperature, the heat pump 4 is stopped, so that the compressor 12 can be protected. However, even in that case, the waste heat recovery heat exchanger 17 can exchange heat between the water supply and the heat source fluid to recover the heat from the heat source fluid. In addition, by switching the control target temperature of the outlet side water temperature of the condenser 13 to the second target temperature lower than the first target temperature, the water supply flow rate to the water supply tank 3 via the water supply path 8 is ensured to some extent. Thus, heat recovery from the heat source fluid can be effectively achieved.

  Switching from the second control to the first control is performed as follows. That is, while the heat pump 4 is stopped, the feed water flow rate to the feed water tank 3 via the feed water channel 8 is being adjusted so that the temperature detected by the hot water temperature sensor 29 is maintained at the second target temperature (that is, during the second control). ), When the detected temperature of the heat source temperature sensor 30 continues below the set temperature for a set time (for example, 60 seconds), the process returns to the first control. In other words, the heat pump 4 may be restarted to switch to control for adjusting the feed water flow rate to the feed water tank 3 via the feed water path 8 so that the temperature detected by the hot water temperature sensor 29 is maintained at the first target temperature.

  However, switching from the second control to the first control may be performed as follows. That is, while the heat pump 4 is stopped, the feed water flow rate to the feed water tank 3 via the feed water channel 8 is being adjusted so that the temperature detected by the hot water temperature sensor 29 is maintained at the second target temperature (that is, during the second control). ) When the temperature detected by the heat source temperature sensor 30 is lower than a predetermined temperature (for example, 58 ° C.) lower than the set temperature, the first control is returned to. In other words, the heat pump 4 may be restarted to switch to control for adjusting the feed water flow rate to the feed water tank 3 via the feed water path 8 so that the temperature detected by the hot water temperature sensor 29 is maintained at the first target temperature.

  In any case, when the heat source fluid temperature to the evaporator 15 is lowered to a predetermined level, the second control in which the heat pump 4 is stopped can be returned to the first control in which the heat pump 4 is operated. In this way, switching between the first control and the second control is performed according to the heat source fluid temperature to the evaporator 15.

  However, when the temperature detected by the heat source temperature sensor 30 becomes higher than the upper limit temperature (for example, 65 ° C.) higher than the set temperature during water supply to the water supply tank 3 through the water supply path 8, the operation of the water supply heating system 1 is stopped. It is good to do. Specifically, the heat pump 4 is stopped, the heat source supply pump 21 is stopped, and the supply of the heat source fluid to the evaporator 15 is also stopped. Furthermore, the water supply pump 10 is also preferably stopped. Thus, when the heat source fluid temperature to the evaporator 15 rises excessively, the operation of the feed water warming system 1 is stopped, so that the feed water warming system 1 can be protected. Here, the upper limit temperature is higher than the set temperature but lower than the first target temperature.

  In addition, 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 28 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, when the amount of water supplied to the water supply tank 3 via the water supply path 8 is below the setting, the operation of the heat pump 4 is stopped and the heat source supply pump 21 is turned on. It is preferable to stop the supply of heat source water to the evaporator 15.

  By the way, when the feed water warming system 1 is cold-started (for example, when the pause time of the feed water warming system 1 is longer than a predetermined time or when the heat source water in the heat source water tank 6 is cooled to about room temperature) When water supply via the water supply path 8 is started based on the water level in the tank 3 and supply of the heat source fluid to the evaporator 15 is started by the operation of the heat source supply pump 21, the following control is performed. Is preferred. That is, if the temperature detected by the heat source temperature sensor 30 is lower than the lower limit temperature (for example, 35 ° C.), the heat pump 4 is stopped, and if the temperature is equal to or higher than the lower limit temperature, the heat pump 4 is started and the first control is executed. To do. At the time of cold start, the compressor 12 can be protected by stopping the heat pump 4 until the heat source fluid temperature to the evaporator 15 becomes equal to or higher than the lower limit temperature. The lower limit temperature is set to a temperature lower than the set temperature or each target temperature.

  Once the heat pump 4 is activated, even when the temperature detected by the heat source temperature sensor 30 is lower than the lower limit temperature during water supply to the water supply tank 3 via the water supply path 8, the water pump 3 is supplied to the water supply tank 3 via the water supply path 8. As long as the water supply continues, the operation of the heat pump 4 is preferably continued. Once the heat pump 4 is started, the refrigerant of the heat pump 4 is warmed more than at the time of cold start, so there is no possibility of damaging the compressor 12 even if the operation of the heat pump 4 is continued. Note that the controller preferably notifies the user by outputting to the display means or the like that the detected temperature of the heat source temperature sensor 30 has become lower than the lower limit temperature.

  The feed water heating system of the present invention is not limited to the configuration of the above embodiment, and can be changed as appropriate. In particular, in the feed water heating system 1 including the heat pump 4, the feed water tank 3, and the waste heat recovery heat exchanger 17, after starting the supply of the heat source fluid to the evaporator 15 during the cold start, the evaporator 15 If the heat source fluid temperature is less than the lower limit temperature, the heat pump 4 is stopped. If the heat source fluid temperature is equal to or higher than the lower limit temperature, the other configuration and control can be appropriately changed. For example, in the embodiment, the installation of the supercooler 16 may be omitted. Moreover, the supplementary water channel 9 provided with the supplementary water pump 11 is omissible depending on the case.

  Further, in the embodiment, the water supply pump 10 is inverter-controlled in order to adjust the water supply flow rate to the water supply tank 3 via the water supply path 8, but a valve provided in the water supply path 8 while controlling the water supply pump 10 on and off. The degree of opening 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 29, the flow rate adjustment method can be changed as appropriate.

  In the case of the above embodiment, if the water supply tank 3 can be supplied with water by the water supply path 8 through the condenser 13 and can be supplied by the replenishment water path 9 without through the condenser 13, the water supply path 8 or The specific configuration of the replenishment water channel 9 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 branch part, and the valves provided in the water supply path 8 and / or the supplementary water path 9 downstream of the branch part 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.

  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.

  Moreover, in the said Example, when operating the heat pump 4, although the power supply frequency of the motor of the compressor 12 was maintained constant, you may control so that the discharge pressure of the compressor 12 may be maintained predetermined depending on the case. . Alternatively, the output of the compressor 12 may be adjusted based on the water level in the water supply tank 3 or the heat source fluid temperature to the evaporator 15.

  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 low stage heat pump and the refrigerant from the expansion valve of the high stage heat pump and exchanges heat by directly contacting both refrigerants is provided. It is a low-stage heat pump condenser and a high-stage heat pump evaporator. 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.

  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 7 Pump 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 Supercooling Equipment 17 Waste heat recovery heat exchanger 18 Heat source supply path 19 Heat source water supply path 20 Overflow path 21 Heat source supply pump 22 Water level detector 23 Water supply start electrode rod 24 Water supply stop electrode rod 25 Supply water start electrode rod 26 Supply water stop electrode Rod 27 Water level detector 28 Low water level detection electrode rod 29 Hot water temperature sensor 30 Heat source temperature sensor H1 Water supply start water level H2 Water supply stop water level H3 Supply water start water level H4 Supply water stop water level

Claims (7)

A compressor, a condenser, an expansion valve, and an evaporator are sequentially connected in an annular manner to circulate the refrigerant, draw up heat from a heat source fluid that passes through the evaporator, and heat water that passes through the condenser When,
A water supply tank capable of supplying water by a water supply channel via the condenser;
A waste heat recovery heat exchanger for exchanging heat between the water in the water supply channel upstream of the condenser and the heat source fluid after passing through the evaporator;
At the time of cold start, after starting the supply of the heat source fluid to the evaporator, if the heat source fluid temperature to the evaporator is less than the lower limit temperature, the heat pump is stopped, A feed water heating system characterized by starting a heat pump. Once the heat pump is started, the operation of the heat pump is continued even when the temperature of the heat source fluid to the evaporator becomes lower than the lower limit temperature during the water supply to the water supply tank via the water supply channel. The feed water heating system according to claim 1. If the heat source fluid temperature to the evaporator is lower than a set temperature that is higher than the lower limit temperature during water supply to the water supply tank via the water supply channel, the condensation is performed while the heat pump is operated. Adjusting the water supply flow rate to the water supply tank via the water supply path so as to maintain the outlet water temperature of the vessel at the first target temperature,
When the heat source fluid temperature to the evaporator is equal to or higher than a set temperature during water supply to the water supply tank via the water supply channel, the water temperature on the outlet side of the condenser is set to the first target with the heat pump stopped. The feed water heating system according to claim 1 or 2, wherein a feed water flow rate to the feed water tank via the feed water channel is adjusted so as to maintain a second target temperature lower than a temperature. While adjusting the feed water flow rate to the feed water tank via the feed water channel so that the outlet water temperature of the condenser is maintained at the second target temperature, the heat source fluid temperature to the evaporator is set to be lower than a set temperature. Control that adjusts the feed water flow rate to the feed water tank via the feed water path so that the heat pump is operated and the outlet side water temperature of the condenser is maintained at the first target temperature when the time continues. The feed water warming system according to claim 3, wherein the feed water warming system is switched to. While adjusting the feed water flow rate to the feed water tank via the feed water channel so that the outlet water temperature of the condenser is maintained at the second target temperature, the heat source fluid temperature to the evaporator is lower than the set temperature When the temperature is lower than a predetermined temperature, the heat pump is operated, and the water supply flow rate to the water supply tank via the water supply path is adjusted so that the outlet water temperature of the condenser is maintained at the first target temperature. It switches to the control to adjust. The feed water heating system of Claim 3 characterized by the above-mentioned. When the heat source fluid temperature to the evaporator becomes equal to or higher than the upper limit temperature higher than the set temperature during water supply to the water supply tank via the water supply channel, the heat pump is stopped and the heat source fluid to the evaporator Supply also stops. The feed water heating system of any one of Claims 3-5 characterized by the above-mentioned. The water supply / warming system according to any one of claims 1 to 6, wherein the presence or absence of water supply to the water supply tank via the water supply path is switched based on a water level of the water supply tank.

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