JP2016048125A - Supply water heating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently heat supply water to a desired temperature even when a temperature of a heat source fluid is low, in a supply water heating system using a heat pump.SOLUTION: A low stage-side heat pump 4 includes a low stage-side compressor 14, a low stage-side condenser 15, a cascade heat exchanger 13, a low stage-side expansion valve 16 and a low stage-side evaporator 17 in order. A high stage-side heat pump 5 includes a high stage-side compressor 18, a high stage-side condenser 19, a high stage-side expansion valve 21, a cascade heat exchanger 13, and a high stage-side evaporator 22 in order. The cascade heat exchanger 13 is a heat exchanger for a refrigerant of the low stage-side heat pump 4 and a refrigerant of the high stage-side heat pump 5. The heat source fluid is passed through a heat exchanger 25 for heating supply water, the low stage-side evaporator 17, and the high stage-side evaporator 22. The supply water to a supply water tank 3 through a water supply path 9 is successively passed through the heat exchanger 25 for heating supply water, the low stage-side condenser 15, and the high stage-side condenser 19.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, as disclosed in Patent Document 1 below, a feed water heating system using a heat pump is known. This feed water heating system (1) includes a heat pump (4) and a feed water heating heat exchanger (12), and the feed water to the feed water tank (3) via the feed water channel (8) is the feed water warming. The heat exchanger for heat (12), the supercooler (17) and the condenser (14) are passed in order. The feed water heating heat exchanger (12) is a heat exchanger for supplying water to the feed water tank (3) via the feed water channel (8) and the heat source fluid after passing through the evaporator (16). The cooler (17) is a 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). 14) is a heat exchanger for supplying water to the water supply tank (3) via the water supply channel (8) and the refrigerant from the compressor (13).

JP2013-210118A

  In the conventional configuration, when the temperature of the heat source fluid is low (for example, 30 to 40 ° C.), it is difficult to warm the hot water temperature at the outlet side of the condenser to a desired temperature.

  Therefore, the problem to be solved by the present invention is to provide a feed water heating system that can efficiently heat feed water to a desired temperature even when the temperature of the heat source fluid is low.

  The present invention has been made to solve the above problems, and the invention according to claim 1 includes a low stage compressor, a low stage condenser, a cascade heat exchanger, a low stage expansion valve, and a low stage. A low-stage heat pump in which the side evaporators are sequentially connected in an annular manner to circulate the refrigerant, a high-stage compressor, a high-stage condenser, a high-stage expansion valve, the cascade heat exchanger, and the high-stage evaporator A high-stage heat pump that is sequentially connected in a ring to circulate the refrigerant, and a heat exchanger for heating the feed water that heats the water by heat exchange with the heat source fluid, and the low-stage condenser includes the low-stage condenser It is a heat exchanger between the refrigerant of the stage side heat pump and the water flow, the low stage side evaporator is a heat exchanger between the refrigerant of the low stage side heat pump and the heat source fluid, and the high stage side condenser is The high-stage side heat pump is a heat exchanger between refrigerant and water flow, and the high-stage side evaporator is It is a heat exchanger between the refrigerant of the high stage side heat pump and the heat source fluid, and the cascade heat exchanger is a heat exchanger between the refrigerant of the low stage side heat pump and the refrigerant of the high stage side heat pump, and a water supply channel The feed water warming system is characterized in that the feed water to the feed water tank via is passed through the feed water warming heat exchanger, the low stage side condenser and the high stage side condenser in this order.

  According to invention of Claim 1, a low stage side heat pump and a high stage side heat pump are connected by a cascade heat exchanger. The cascade heat exchanger functions as a low stage side subcooler and also functions as a high stage side evaporator. The heat pumped from the heat source fluid by the low-stage heat pump is further pumped by the high-stage heat pump via the cascade heat exchanger. Moreover, in the high stage heat pump, heat is pumped up from the heat source fluid even in the high stage evaporator provided separately from the cascade heat exchanger. Therefore, even if the heat source fluid is at a relatively low temperature, the water passing through the water supply channel can be heated as desired. At this time, the feed water preheated by the feed water warming heat exchanger can be passed through the low stage side condenser and the high stage side condenser in order to be heated to a desired temperature. In the low-stage heat pump, the low-stage condenser is provided on the low-stage compressor side of the cascade heat exchanger, and the water can be heated with the high-temperature refrigerant from the low-stage compressor. Easy to raise temperature.

  According to a second aspect of the present invention, a heat source fluid is passed through the low-stage evaporator and the high-stage evaporator in series or in parallel in a set order. The feed water warming system according to claim 1, wherein the heat source fluid is passed through the feed water warming heat exchanger in parallel with the heat source fluid supply.

  According to the invention described in claim 2, since the heat source fluid is passed through the feed water heating heat exchanger in parallel with each evaporator, the heat source fluid after passing through each evaporator is passed in series. Compared with the case, the heating amount of the water flow in the heat exchanger for water supply heating can be increased.

  According to a third aspect of the present invention, the operation of the low-stage compressor is maintained while maintaining the operation of the high-stage compressor when a set condition is satisfied during water supply to the water supply tank via the water supply channel. The feed water warming system according to claim 1 or 2, wherein the water supply warming system is stopped.

  According to the third aspect of the present invention, when supplying water to the water supply tank via the water supply channel, if desired, the low-stage compressor is stopped, and only the high-stage heat pump is used to heat the supply water. it can.

  The invention according to claim 4 is characterized in that when the heat source fluid temperature to the high stage side evaporator exceeds the low stage side stop temperature, the low stage side compressor is stopped assuming that the setting condition is satisfied. The feed water warming system according to claim 3.

  According to the fourth aspect of the present invention, if the heat source fluid temperature is higher than a predetermined value, the low-stage compressor can be stopped and the water supply can be heated only by the high-stage heat pump. Thereby, power consumption can be reduced.

  The invention according to claim 5 adjusts the water flow rate so that the water temperature at the outlet side of the high-stage side condenser is maintained at a set temperature during the water supply to the water supply tank via the water supply channel, and the water flow rate 4. The low-stage compressor is stopped when the rotational speed of the pump for adjusting the valve opening or the valve opening exceeds a low-stage-side stop value, assuming that the setting condition is satisfied. 4. A water heating system according to 4.

  According to the fifth aspect of the present invention, the water supply source is adjusted by adjusting the water flow rate so as to maintain the outlet side water temperature of the high stage side condenser at the set temperature during the water supply to the water supply tank via the water supply channel. Regardless of the water temperature or the temperature of the heat source fluid, hot water having a desired temperature can be obtained. Also, if the number of rotations of the pump for adjusting the water flow rate or the opening of the valve becomes larger than a predetermined value, the adjustment of the water flow rate may be impossible, so by stopping the low-stage compressor, The hot water temperature constant control can be stably performed.

  The invention according to claim 6 is characterized in that when the water level of the water supply tank exceeds the low-stage stop water level, the low-stage compressor is stopped assuming that the setting condition is satisfied. 5. The feed water warming system according to claim 1.

  According to the invention described in claim 6, when the water level of the water supply tank becomes higher than a predetermined level, the low-stage compressor is stopped and the water supply is heated only by the high-stage heat pump. Control becomes easy.

  When the water level of the water supply tank falls below a lower limit water level, the invention according to claim 7 starts water supply to the water supply tank via the water supply path, starts the compressors, When the water level exceeds an upper limit water level, water supply to the water supply tank via the water supply channel is stopped, and the compressors are stopped. This is a water heating system.

  According to invention of Claim 7, according to the water level of a water supply tank, each heat pump can be controlled and the water supply to a water supply tank can be controlled.

  The invention according to claim 8 is characterized in that when the compressors are started from a stopped state, the high-stage compressor is first started, and then the low-stage compressor is started at a set timing. The feed water warming system according to any one of claims 1 to 7.

  If the low-stage compressor is started first and the high-stage compressor is started after a delay, the water flow temperature (the outlet-side water temperature of the high-stage condenser) becomes too high when the high-stage compressor is started. However, according to the invention described in claim 8, since the high-stage compressor is started first, and the low-stage compressor is started after a delay, the water flow temperature when the low-stage compressor is started. Is prevented from rising excessively.

  In the invention according to claim 9, the temperature difference between the heat source fluid temperature to the feed water heating heat exchanger and the outlet water temperature of the feed water heating heat exchanger is maintained at a set value. The feed water warming system according to any one of claims 1 to 8, wherein a supply flow rate of the heat source fluid to the feed water warming heat exchanger is adjusted.

  According to the ninth aspect of the present invention, the water supply water temperature is maintained so that the temperature difference between the heat source fluid temperature to the feed water heating heat exchanger and the outlet water temperature of the feed water heating heat exchanger is maintained at a set value. By controlling the supply flow rate of the heat source fluid to the heating heat exchanger, the heat exchange efficiency in the feed water heating heat exchanger can be increased. Also, when the heat source fluid temperature to the feed water heating heat exchanger is lower than the inlet side water temperature of the feed water heating heat exchanger, the supply of the heat source fluid to the feed water heating heat exchanger is regulated. Therefore, inconvenience of cooling the feed water when the heat source fluid is passed through the feed water heating heat exchanger is prevented.

  Furthermore, in the invention described in claim 10, heat source fluid is sequentially passed through the low stage side evaporator and the high stage side evaporator in a set order, and supply of the heat source fluid to each of the evaporators is in parallel. The heat source fluid is passed through the feed water heating heat exchanger, so that the heat source fluid temperature after passing through each of the evaporators is equal to the heat source fluid temperature after passing through the feed water warming heat exchanger. 10. The feed water heating system according to claim 1, wherein a distribution ratio of a heat source fluid to each of the evaporators and the feed water warming heat exchanger is adjusted. .

  According to the tenth aspect of the present invention, each evaporator is set so that the heat source fluid temperature after passing through each evaporator in the setting order is equal to the heat source fluid temperature after passing through the feed water heating heat exchanger. By adjusting the distribution ratio of the heat source fluid to the heat exchanger for heating and supplying water, heat can be distributed in a balanced manner to each heat pump and heat exchanger for heating and supplying water.

  According to the feed water heating system of the present invention, even when the temperature of the heat source fluid is low, the feed water can be efficiently heated to a desired temperature.

It is the schematic which shows the feed water heating system of one Example 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 diagram showing a feed water heating system 1 according to an embodiment of the present invention.

  The feed water warming system 1 of the present embodiment is a system that can heat feed water to the feed water tank 3 of the boiler 2 with the heat pumps 4, 5. The feed water tank 3 that stores the feed water to the boiler 2, and the feed water tank 3 A replenishment water tank 6 for storing water supply to the water, heat pumps 4 and 5 for heating water supplied from the replenishment water tank 6 to the water supply tank 3, and heat source water (for example, waste hot water) as a heat source for the heat pumps 4 and 5 The heat source water tank 7 is stored.

  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 8 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.

  The water supply tank 3 can be supplied with water from the make-up water tank 6 through the heat supply passage 9 via the heat pumps 4, 5, and can be supplied through the supply water passage 10 without going through the heat pumps 4, 5. By controlling the operation of the water supply pump 11 provided in the water supply channel 9 and the makeup water pump 12 provided in the makeup water channel 10, via either one or both of the water supply channel 9 and the makeup water channel 10, Water can be supplied from the makeup water tank 6 to the water supply tank 3.

  In this embodiment, the feed water pump 11 can control the rotation speed by an inverter. By changing the rotation speed of the water supply pump 11, the water supply flow rate to the water supply tank 3 through the water supply path 9 can be adjusted. On the other hand, the makeup water pump 12 is on / off controlled in this embodiment.

  The makeup water tank 6 stores the water supply to the water supply tank 3. In this embodiment, soft water is used as water supply to the makeup water tank 6. That is, the soft water from which the water hardness is removed by the water softener (not shown) is supplied to the makeup water tank 6 and stored. By controlling the water supply from the water softener based on the water level of the makeup water tank 6, the water level of the makeup water tank 6 is maintained as desired.

  The heat pumps 4 and 5 are vapor compression heat pumps, and are constituted by two heat pump cycles. Specifically, a low stage side heat pump (low temperature side heat pump) 4 and a high stage side heat pump (high temperature side heat pump) 5 are connected via a cascade heat exchanger 13. In addition, the refrigerant | coolants of each heat pump 4 and 5 may be the same, and may differ.

  The low-stage heat pump 4 includes a low-stage compressor 14, a low-stage condenser 15, a cascade heat exchanger 13, a low-stage expansion valve 16, and a low-stage evaporator 17 that are sequentially connected in an annular manner, Circulate. In the low stage side heat pump 4, the refrigerant takes heat from outside in the low stage side evaporator 17 and vaporizes, while in the low stage side condenser 15 and the cascade heat exchanger 13, the refrigerant dissipates heat to the outside and condenses. Supercool. Using this, the low-stage heat pump 4 pumps heat from the heat source water in the low-stage evaporator 17, warms the water in the water supply passage 9 in the low-stage condenser 15, and cascades the heat exchanger 13. The refrigerant of the high stage side heat pump 5 is heated.

  Each component of the low stage side heat pump 4 is demonstrated in order. The low stage compressor 14 compresses the gas refrigerant to a high temperature and a high pressure. The low stage side condenser 15 is an indirect heat exchanger that exchanges heat without mixing the refrigerant of the low stage side heat pump 4 and the water of the water supply path 9, and condenses the gas refrigerant from the low stage side compressor 14. The water in the water supply channel 9 is heated. The cascade heat exchanger 13 is an indirect heat exchanger that exchanges heat without mixing the refrigerant of the low-stage heat pump 4 and the refrigerant of the high-stage heat pump 5, and supercools the refrigerant from the low-stage condenser 15. On the other hand, the refrigerant of the high-stage heat pump 5 is evaporated. The low stage side expansion valve 16 allows the liquid refrigerant from the cascade heat exchanger 13 to pass therethrough, thereby reducing the pressure and temperature of the refrigerant. The low-stage evaporator 17 is an indirect heat exchanger that exchanges heat without mixing the refrigerant of the low-stage heat pump 4 and the heat source water, and evaporates the refrigerant from the low-stage side expansion valve 16 while Cooling.

  The high-stage heat pump 5 includes a high-stage compressor 18, a high-stage condenser 19, a high-stage subcooler 20, a high-stage expansion valve 21, a cascade heat exchanger 13, and a high-stage evaporator 22. It is connected in a ring and circulates the refrigerant. The high-stage heat pump 5 is vaporized by removing heat from the outside in the cascade heat exchanger 13 and the high-stage evaporator 22, while the refrigerant is removed in the high-stage condenser 19 and the high-stage subcooler 20. Radiates heat to the outside and condenses and supercools. Utilizing this, the high stage side heat pump 5 pumps heat from the refrigerant of the low stage side heat pump 4 in the cascade heat exchanger 13, and pumps heat from the heat source water in the high stage side evaporator 22. Water in the water supply passage 9 is heated in the cooler 20 and the high-stage condenser 19.

  Each component of the high stage side heat pump 5 is demonstrated in order. The high stage compressor 18 compresses the gas refrigerant to a high temperature and a high pressure. The high stage side condenser 19 is an indirect heat exchanger that exchanges heat without mixing the refrigerant of the high stage side heat pump 5 and the water of the water supply path 9, and condenses the gas refrigerant from the high stage side compressor 18. The water in the water supply channel 9 is heated. The high stage side subcooler 20 is an indirect heat exchanger that exchanges heat without mixing the refrigerant of the high stage side heat pump 5 and the water of the water supply passage 9, and supercools the refrigerant from the high stage side condenser 19. On the other hand, the water in the water supply channel 9 is heated. The high stage side expansion valve 21 reduces the pressure and temperature of the refrigerant by allowing the liquid refrigerant from the high stage side subcooler 20 to pass therethrough. The cascade heat exchanger 13 is an indirect heat exchanger that exchanges heat without mixing the refrigerant of the low-stage heat pump 4 and the refrigerant of the high-stage heat pump 5, and the refrigerant subcooler from the low-stage condenser 15. And also functions as a refrigerant evaporator from the high-stage expansion valve 21. The high stage side evaporator 22 is an indirect heat exchanger that exchanges heat without mixing the refrigerant of the high stage side heat pump 5 and the heat source water, and evaporates the refrigerant from the cascade heat exchanger 13 (and further overheats if desired). On the other hand, the heat source water is cooled.

  In each heat pump 4, 5, an accumulator is installed on the inlet side of the compressors 14, 18, an oil separator is installed on the outlet side of the compressors 14, 18, or the outlet side of the condensers 15, 19 A liquid receiver may be installed between the condensers 15 and 19 and the subcoolers 13 and 20. Also, a low-stage liquid gas heat exchanger that indirectly exchanges heat between the refrigerant from the low-stage condenser 15 to the cascade heat exchanger 13 and the refrigerant from the low-stage evaporator 17 to the low-stage compressor 14. Or high-stage liquid gas heat that indirectly exchanges heat between the refrigerant from the high-stage condenser 19 to the high-stage subcooler 20 and the refrigerant from the high-stage evaporator 22 to the high-stage compressor 18. An exchanger may be provided. In addition, in the present embodiment, the compressors 14 and 18 of the heat pumps 4 and 5 are on / off controlled, and the rotation speed is kept constant during the operation. Based on the above, the rotational speed may be changed by an inverter.

  The heat source water tank 7 stores heat source water as a heat source for the heat pumps 4 and 5. The heat source water is, for example, waste hot water (hot water discharged from a factory or the like). In the case of the feed water warming system 1 of the present embodiment, even when the heat source water temperature is relatively low (for example, about 30 to 40 ° C.), hot water having a desired temperature can be produced as described later. The heat source water tank 7 is provided with a heat source water supply path 23 and an overflow path 24 for overflowing a predetermined amount or more of water.

  The feed water heating system 1 further includes a feed water warming heat exchanger 25. The heat exchanger 25 for heating and supplying water is an indirect heat exchanger that performs heat exchange without mixing water supplied to the water supply tank 3 via the water supply passage 9 and heat source water from the heat source water tank 7.

  The water supply to the water supply tank 3 through the water supply path 9 is sequentially passed through the heat exchanger 25 for supplying water heating, the low stage side condenser 15, the high stage side subcooler 20, and the high stage side condenser 19. . On the other hand, the heat source water from the heat source water tank 7 is passed through the low-stage evaporator 17, the high-stage evaporator 22, and the feed water heating heat exchanger 25 in series in a set order, or part or all of them. The heat exchanger is passed in parallel. Preferably, the heat source water is passed through the low stage side evaporator 17 and the high stage side evaporator 22 in series or in parallel in a set order, and the heat source water to each of the evaporators 17 and 22 is passed. In parallel with the supply, the heat source water is passed through the heat exchanger 25 for heating the feed water.

  In the present embodiment, the heat source water from the heat source water tank 7 is branched into a first heat source supply path 27 and a second heat source supply path 28 via a heat source supply pump 26, and the heat source of the first heat source supply path 27. The water is sequentially passed through the high-stage evaporator 22 and the low-stage evaporator 17, while the heat source water in the second heat source supply path 28 is passed to the feed water heating heat exchanger 25. That is, in the present embodiment, the heat source water is passed through the high stage side evaporator 22 and the low stage side evaporator 17 in order, and in parallel with this, the heat source water is passed through the feed water heating heat exchanger 25. The

  The second heat source supply path 28 is provided with a flow rate adjustment valve 29 whose opening degree can be adjusted. By adjusting the opening degree of the flow rate adjustment valve 29, the supply flow rate (water flow rate) of the heat source water to the heat exchanger 25 for heating and heating the feed water can be adjusted.

  In the water supply path 9, a hot water temperature sensor 30 is provided on the outlet side of the high stage side condenser 19. The tapping temperature sensor 30 detects the water temperature after passing through the high-stage condenser 19. Based on the temperature detected by the hot water temperature sensor 30, the feed water pump 11 is controlled. Here, the feed water pump 11 is inverter-controlled so as to maintain the temperature detected by the tapping temperature sensor 30 at a set temperature (for example, 75 ° C.). That is, the flow rate of water supplied to the water supply tank 3 via the water supply path 9 is adjusted so that the temperature detected by the hot water temperature sensor 30 is maintained at the set temperature. However, in some cases, such flow rate adjustment control by the tapping temperature sensor 30 can be omitted.

  A water level detector 31 is provided in the water supply tank 3. The configuration of the water level detector 31 is not particularly limited. In the present embodiment, the water level detector 31 is an electrode type water level detector. In this case, a plurality of electrode rods 32 and 33 having different lengths are inserted and held in the water supply tank 3 with their lower end portions having different height positions. Specifically, the water supply stop electrode rod 32 and the water supply start electrode rod 33 are inserted into the water supply tank 3 with the lower end portion having a lower height in order. Furthermore, as shown by a broken line, a low-stage stop electrode rod 34 may be provided. In this case, the lower end portion of the lower end is arranged in the order of the water supply stop electrode rod 32, the low-stage stop electrode rod 34, and the water supply start electrode rod 33. The position is lowered and inserted into the water supply tank 3. In any case, each electrode rod 32 to 34 detects the presence or absence of a water level at the lower end portion depending on whether the lower end portion is immersed in water. The water level detected by the water supply stop electrode rod 32 is the water supply stop water level (upper limit water level), the water level detected by the water supply start electrode rod 33 is the water supply start water level (lower limit water level), and the water level detected by the lower stage stop electrode rod 34 is lower. The stop water level is assumed.

  A heat source supply path to the heat exchanger 25 for supplying water heating (a common path upstream from the branch section of the first heat source supply path 27 and the second heat source supply path 28 is preferable. The heat source temperature sensor 35 for detecting the heat source water temperature to the feed water heating heat exchanger 25 is provided in the second heat source supply path 28 on the downstream side. On the other hand, a water temperature sensor 36 for detecting the outlet water temperature of the feed water warming heat exchanger 25 is provided on the outlet side of the feed water warming heat exchanger 25 in the feed water channel 9.

  Each heat pump 4, 5 (particularly its compressors 14, 18), feed water pump 11, makeup water pump 12, heat source supply pump 26, flow rate adjustment valve 29, tapping temperature sensor 30, water level detector 31, heat source temperature sensor 35, and water temperature The sensor 36 and the like are connected to a controller (not shown). And a controller controls each heat pump 4,5, each pump 11,12,26, the flow regulating valve 29, etc. based on the detection signal of each sensor 30,31,35,36, etc. Execute control.

  Water supply to the water supply tank 3 via the water supply path 9 is controlled based on the water level of the water supply tank 3. Specifically, in this embodiment, control is performed as follows. Now, when the water supply stop electrode rod 32 detects the water level and the water level of the water supply tank 3 is sufficient (that is, when it exceeds the water supply stop water level), water supply to the water supply tank 3 is unnecessary, so the water supply pump 11 Has stopped. When the water level from the water supply tank 3 to the boiler 2 is lowered and the water supply start electrode rod 33 no longer detects the water level (that is, when the water level falls below the water supply start water level), the water supply pump 11 is operated. Thus, water is supplied to the water supply tank 3 through the water supply passage 9, but when the water supply stop electrode rod 32 detects the water level, the water supply pump 11 is stopped.

  Although it is possible to supply water to the water supply tank 3 via the water supply channel 9 and also to supply water via the replenishment water channel 10, it is preferable that the water supply via the water supply channel 9 be controlled so that priority is given. For example, the water supply through the water supply channel 9 is controlled as described above 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 supply water channel 10 It is preferable to supply water to the water supply tank 3 also through the In that case, the water level detector 31 of the water supply tank 3 may be configured to be able to detect the water levels for starting and stopping the makeup water pump 12 (the makeup water start water level and the makeup water stop water level).

  While supplying water to the water supply tank 3 via the water supply passage 9 (that is, during operation of the water supply pump 11), the heat source supply pump 26 is operated and the heat pumps 4 and 5 (at least the high-stage heat pump 5 as described later) are operated. Let That is, the heat source supply pump 26 and the heat pumps 4 and 5 are started and stopped so as to interlock with the water supply pump 11. However, when the heat pumps 4 and 5 are started, first, the water supply pump 11 and the heat source supply pump 26 are operated to check the supply of the water supply and heat source water to the heat pumps 4 and 5 and then the heat pumps 4 and 5 are started. preferable. The heat pumps 4 and 5 are switched between operation and stop depending on whether or not the compressors 14 and 18 are activated.

  During the water supply to the water supply tank 3 through the water supply path 9, the water supply pump 11 is preferably inverter-controlled so that the temperature detected by the tapping temperature sensor 30 is maintained at the set temperature. Hereinafter, this control is referred to as a constant tapping temperature control.

  When the heat pumps 4 and 5 are started, it is preferable to start the high stage heat pump 5 first, and then start the low stage heat pump 4 at the set timing. For example, first, the high-stage heat pump 5 is activated, and the low-stage heat pump 4 is activated after a set time (for example, 5 minutes) until the operation of the high-stage heat pump 5 is stabilized. Good. The reason is as follows.

  That is, if the low-stage heat pump 4 is activated first and the high-stage heat pump 5 is activated later, even when only the low-stage heat pump 4 is in operation, the detection of the tapping temperature sensor 30 is performed by the above-described constant tapping temperature control. Since the amount of water supply is adjusted so as to maintain the temperature at the set temperature, when the high-stage heat pump 5 on the downstream side of the water supply path 9 is further activated in this state, the temperature detected by the tapping temperature sensor 30 exceeds the set temperature. There is a fear. In addition, since relatively high-temperature water is passed through the high-stage heat pump 5, the refrigerant cannot be condensed in the high-stage condenser 19 or the high-stage subcooler 20 as desired when the high-stage heat pump 5 is started. Further, the pressure and temperature of the refrigerant in the high stage heat pump 5 may increase excessively, and the high stage heat pump 5 may be interlocked. On the other hand, if the high stage side heat pump 5 is started first, such inconvenience can be prevented.

  When the heat pumps 4 and 5 are operated to supply water from the make-up water tank 6 to the water supply tank 3 through the water supply passage 9, the water supplied from the make-up water tank 6 is supplied with the heat exchanger 25 for supplying water heating, the low-stage side condensation The heater 15, the high stage side subcooler 20, and the high stage side condenser 19 are sequentially passed through and heated. On the other hand, in this embodiment, the heat source water from the heat source water tank 7 is passed through the high stage side evaporator 22 and the low stage side evaporator 17 in order, and in parallel with this, the heat exchanger 25 for heating the feed water is used. Passed through. Compared with the case where heat source water is sequentially passed through each evaporator 22, 17 and feed water heating heat exchanger 25 in series, heat source water is fed to each evaporator 22, 17 and feed water heating heat exchanger 25. When passing in parallel, heat source water having a relatively high temperature can be passed through the heat exchanger 25 for heating the feed water. Thereby, since the heat exchange amount in the heat exchanger 25 for feed water warming can be increased and heating of the feed water in front of the heat pumps 4 and 5 is achieved, the power of each compressor 14, 18 is reduced, The efficiency of the heat pumps 4 and 5 can be improved. Further, when the heat source water is passed through the evaporators 22 and 17 and the feed water heating heat exchanger 25 in order, the evaporators 22 and 17 become pressure loss elements. When the heat source water is passed through the heat exchanger 25 for use in parallel, there is an advantage that there is no such pressure loss element.

  Moreover, according to the feed water heating system 1 of the present embodiment, the heat pumped from the heat source water by the low stage heat pump 4 is further pumped by the high stage heat pump 5 via the cascade heat exchanger 13. In the high stage heat pump 5, heat is pumped up from the heat source water also in the high stage evaporator 22 provided separately from the cascade heat exchanger 13. Therefore, even if the heat source water is at a relatively low temperature, the water passing through the water supply passage 9 can be heated as desired. Further, by supporting the high stage side evaporator 22 with the cascade heat exchanger 13, it is possible to prevent a decrease in the outlet temperature of the heat source water from the high stage side evaporator 22. Further, in the low-stage heat pump 4, the low-stage condenser 15 is provided on the low-stage compressor 14 side (that is, the refrigerant is at a higher temperature side) than the cascade heat exchanger 13. Therefore, it is easy to raise the water temperature of the water supply passage 9.

  When both heat pumps 4 and 5 are operated to supply water to the water supply tank 3 through the water supply channel 9 and the set condition is satisfied, the operation of the high stage compressor 18 is maintained and the low stage compressor 14 is maintained. The operation may be stopped. That is, water supply to the water supply tank 3 through the water supply path 9 may be achieved while operating only the high-stage heat pump 5.

  For example, when the heat source water temperature to the high stage side evaporator 22 exceeds the low stage side stop temperature, the low stage side compressor 14 may be stopped assuming that the setting condition is satisfied. Specifically, when the temperature detected by the heat source temperature sensor 35 exceeds the low-stage stop temperature, the low-stage compressor 14 may be stopped. Thereafter, on the assumption that the operation of the feed water pump 11 is continuing, if the temperature detected by the heat source temperature sensor 35 is equal to or lower than the low-stage start temperature, the low-stage compressor 14 may be started. In this way, when the heat source water is at a relatively high temperature, the water supply can be heated as desired by using only the high-stage heat pump 5, so the low-stage heat pump 4 can be stopped to reduce power consumption. it can.

  In addition, in the case where the hot water temperature constant control is performed while controlling the rotation speed of the feed water pump 11 with an inverter, the rotation speed of the feed water pump 11 exceeds a low-stage stop value (for example, the motor of the feed water pump 11 by inverter control). If the drive frequency exceeds the preset maximum frequency), the low-stage compressor 14 may be stopped assuming that the setting condition is satisfied. Thereafter, on the assumption that the operation of the feed water pump 11 is continuing, if the rotation speed of the feed water pump 11 falls below the low stage start value, the low stage compressor 14 may be started.

  During the adjustment of the rotation speed (frequency) of the feed water pump 11 by the constant tapping temperature control, the water flow rate (the rotation speed of the feed water pump 11) becomes too high, and the temperature detected by the tapping temperature sensor 30 may not be maintained at the set temperature. In such a case, such inconvenience can be prevented by stopping the low-stage heat pump 4. Moreover, it can prevent that the refrigerant | coolant pressure of the high stage side heat pump 5 becomes high too much.

  Further, in the water level detector 31 of the water supply tank 3, as described above, in addition to the water supply stop electrode rod 32 and the water supply start electrode rod 33, a low stage side stop electrode rod 34 is provided, etc. The low-stage stop water level can be detected between the water supply start water level (typically in the center) and if the water level in the water supply tank 3 exceeds the low-stage stop water level, The stage side compressor 14 may be stopped. In this case, the water supply start electrode rod 33 does not detect the water level (that is, it is below the water supply start water level), and both heat pumps 4 and 5 are operating. When detected (that is, above the low-stage stop water level), the low-stage heat pump 4 is stopped first, and when the water supply stop electrode rod 32 detects the water level (that is, above the water supply stop water level), the high-stage heat pump 5 is detected. Also stop. On the contrary, when the water level is lowered, if the low stage side stop electrode bar 34 does not detect the water level (that is, lower than the low stage side stop water level), the high stage side heat pump 5 is started first, and then the water supply start electrode bar When 33 does not detect the water level (that is, below the water supply start water level), the low-stage heat pump 4 is also started.

  By the way, the heat exchanger 25 for water supply heating is maintained so that the temperature difference between the temperature of the heat source water to the heat exchanger 25 for water supply heating and the water temperature on the outlet side of the heat exchanger 25 for water supply warming is maintained at a set value. It is good to control the supply flow rate of the heat source water. Specifically, during the operation of the water supply pump 11, the detected temperature T1 of the water temperature sensor 36 is compared with the detected temperature T2 of the heat source temperature sensor 35 so that T2-T1 becomes a constant temperature (for example, 1 ° C.). The opening degree of the flow rate adjustment valve 29 may be adjusted. Thereby, the supply flow rate of the heat source water to the heat exchanger 25 for supplying water heating can be minimized. When the heat source water temperature to the feed water heating heat exchanger 25 is lower than the inlet water temperature of the feed water heating heat exchanger 25, the heat source water is supplied to the feed water heating heat exchanger 25. Therefore, inconvenience of cooling the feed water when the heat source water is passed through the feed water heating heat exchanger 25 is prevented.

  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, in addition to the low-stage heat pump 4 and the high-stage heat pump 5 connected by the cascade heat exchanger 13, a water supply heating heat exchanger 25 is provided to supply water to the water supply tank 3 via the water supply path 9. The other configurations (including control) can be appropriately changed as long as they are passed through the feed water heating heat exchanger 25, the low-stage condenser 15 and the high-stage condenser 19 in this order. For example, in the above embodiment, the high stage subcooler 20 may be omitted depending on circumstances.

  Moreover, the flow method of the heat source water to the low-stage evaporator 17, the high-stage evaporator 22, and the feed water heating heat exchanger 25 is not limited to the configuration of the above embodiment, and can be changed as appropriate.

  Moreover, in the said Example, although the flow volume adjustment valve 29 was provided in the 2nd heat source supply path 28 to the heat exchanger 25 for feed water heating, supply flow rate of heat source water to the heat exchanger 25 for feed water heating (or As will be described later, if the heat source water supply flow rate to the first heat source supply path 27 and the second heat source supply path 28 (ie, the distribution ratio) can be adjusted, the specific configuration can be changed as appropriate.

  For example, in the embodiment described above, the flow rate adjustment valve 29 is provided in the second heat source supply path 28 after branching from the first heat source supply path 27, and the flow rate adjustment valve 29 is detected by the heat source temperature sensor 35 and the water temperature sensor 36. However, instead of providing the flow rate adjusting valve 29 in the second heat source supply path 28, three-way as shown by the broken line in FIG. 1 is provided at the branch portion of the first heat source supply path 27 and the second heat source supply path 28. A valve 37 may be provided. The three-way valve 37 adjusts the distribution ratio of the heat source water from the heat source supply pump 26 to the first heat source supply path 27 and the second heat source supply path 28. As in the above embodiment, the three-way valve 37 is set so that the temperature difference between the heat source water temperature to the feed water heating heat exchanger 25 and the outlet water temperature of the feed water heating heat exchanger 25 is maintained at a set value. The supply flow rate of the heat source water to the heat exchanger 25 for heating and supplying water may be adjusted by adjusting the distribution ratio.

  Further, when such a three-way valve 37 is provided (or when the flow rate adjustment valve 29 is provided in the same manner as in the above embodiment), the heat source water temperature to the feed water warming heat exchanger 25 and the feed water warming Instead of controlling the supply flow rate of the heat source water to the feed water heating heat exchanger 25 so as to maintain the temperature difference from the outlet water temperature of the heat exchanger 25 at the set value, the following control is performed. May be. That is, the heat source water is sequentially passed through the low-stage evaporator 17 and the high-stage evaporator 22 in the order of setting, and the supply of the heat source water to each of the evaporators 17 and 22 is in parallel with the supply water heating. In the system in which the heat source water is passed through the heat exchanger 25, the heat source water temperature after passing through each of the evaporators 17 and 22 is equal to the heat source water temperature after passing through the feed water heating heat exchanger 25. The distribution ratio of the heat source water to each of the evaporators 17 and 22 and the heat exchanger 25 for heating the feed water may be adjusted. For example, in FIG. 1, during the operation of the heat source supply pump 26, the heat source water temperature on the outlet side of the low-stage evaporator 17 (temperature at point A) and the heat source water temperature on the outlet side of the heat exchanger 25 for supplying water heating. (Temperature B) may be monitored by temperature sensors (not shown), and the three-way valve 37 and the like may be controlled so that both temperatures are equal. In this case, heat can be distributed to each of the evaporators 17 and 22 and the feed water heating heat exchanger 25 in a well-balanced manner.

  Moreover, in the said Example, although the water supply pump 11 was inverter-controlled in order to adjust the water supply flow volume to the water supply tank 3 via the water supply path 9, it provided in the water supply path 9 controlling the water supply pump 11 on / off. The opening degree of the valve may be adjusted. That is, if the flow rate of the water supply through the water supply channel 9 can be adjusted based on the temperature detected by the hot water temperature sensor 30, the flow rate adjustment method can be changed as appropriate.

  Moreover, in the said Example, when controlling the tapping water temperature constant control, controlling the rotation speed of the feed water pump 11 with an inverter, when the rotation speed (frequency) of the feed water pump 11 exceeds a low stage side stop value, it is set. Assuming that the condition was satisfied, the low-stage compressor 14 was stopped. In this regard, when the feed water flow rate of the water supply passage 9 is not adjusted by the inverter but by adjusting the opening of the valve, it may be controlled as follows. That is, when the opening degree of the valve exceeds the low-stage stop value, the low-stage compressor 14 may be stopped assuming that the set condition is satisfied. Thereafter, if the valve opening is equal to or lower than the low stage start value, the low stage compressor 14 may be started.

  Moreover, in the said Example, although the makeup water tank 6 was installed in order to store the water supply to the water supply tank 3, installation of the makeup water tank 6 may be abbreviate | omitted depending on the case, and the water supply path 9 and the replenishment directly from a water supply source. Water may be passed through the water channel 10.

  Moreover, in the said Example, although the water supply from the replenishment water tank 6 to the water supply tank 3 was enabled via the water supply path 9 and / or the replenishment water path 10, these water supply may be performed directly from a water softener. For example, in FIG. 1, the base end portions of the water supply channel 9 and the makeup water channel 10 are collectively connected to the water softener, and instead of omitting the installation of the water supply pump 11, an electric valve (motor valve) provided in the water supply channel 9 is opened. Instead of adjusting the degree and omitting the installation of the makeup water pump 12, the opening and closing of the electromagnetic valve provided in the makeup water channel 10 may be controlled.

  Moreover, although the said Example demonstrated the system which can heat the water supply to the water supply tank 3 of the boiler 2 with the heat pumps 4 and 5, the utilization place of the stored water of the water supply tank 3 is not restricted to the boiler 2, and changes suitably. Is possible. In some cases, the replenishment water tank 6 and the replenishment water channel 10 may be omitted.

  Moreover, although the said Example demonstrated the example using heat source water as a heat source of the heat pumps 4 and 5 (it is also a fluid which heats water supply in the heat exchanger 25 for water supply heating), The heat source fluid is not limited to heat source water, and various fluids such as air and exhaust gas can be used.

  Furthermore, in the said Example, although the compressors 14 and 18 of the heat pumps 4 and 5 were driven by the electric motor, the drive source of the compressors 14 and 18 is not ask | required in particular. For example, the compressors 14 and 18 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. In that case, the output of the compressors 14 and 18 can be adjusted by adjusting the amount of steam supplied to the steam motor or the amount of gas supplied to the gas engine.

DESCRIPTION OF SYMBOLS 1 Feed water heating system 3 Feed water tank 4 Low stage side heat pump 5 High stage side heat pump 6 Supplementary water tank 7 Heat source water tank 9 Water supply path 11 Feed water pump 13 Cascade heat exchanger 14 Low stage side compressor 15 Low stage side condenser 16 Low stage side expansion valve 17 Low stage side evaporator 18 High stage side compressor 19 High stage side condenser 20 High stage side subcooler 21 High stage side expansion valve 22 High stage side evaporator 25 Heat exchanger for heating water supply 26 Heat source supply pump 27 First heat source supply path 28 Second heat source supply path 29 Flow rate adjusting valve 30 Hot water temperature sensor 31 Water level detector 32 Water supply stop electrode rod 33 Water supply start electrode rod 34 Low stage stop electrode rod 35 Heat source temperature sensor 36 Water temperature Sensor

Claims (10)

A low-stage side heat pump in which a low-stage side compressor, a low-stage side condenser, a cascade heat exchanger, a low-stage side expansion valve, and a low-stage side evaporator are sequentially connected in an annular manner to circulate the refrigerant;
A high-stage heat pump for circulating a refrigerant by sequentially connecting a high-stage compressor, a high-stage condenser, a high-stage expansion valve, the cascade heat exchanger and the high-stage evaporator in an annular manner,
A heat exchanger for heating the feed water that heats the water through heat exchange with the heat source fluid,
The low-stage condenser is a heat exchanger between the refrigerant and water flow of the low-stage heat pump,
The low-stage evaporator is a heat exchanger between the refrigerant of the low-stage heat pump and the heat source fluid,
The high-stage condenser is a heat exchanger between the refrigerant and water flow of the high-stage heat pump,
The high-stage evaporator is a heat exchanger between the refrigerant of the high-stage heat pump and the heat source fluid,
The cascade heat exchanger is a heat exchanger between the refrigerant of the low stage side heat pump and the refrigerant of the high stage side heat pump,
Water supply to the water supply tank via the water supply path is sequentially passed through the water supply heating heat exchanger, the low-stage condenser, and the high-stage condenser. A heat source fluid is passed through the low-stage evaporator and the high-stage evaporator in series in a set order or in parallel.
The feed water heating system according to claim 1, wherein a heat source fluid is passed through the feed water warming heat exchanger in parallel with the supply of the heat source fluid to each of the evaporators. When the setting condition is satisfied during water supply to the water supply tank via the water supply channel, the operation of the low-stage compressor is stopped while maintaining the operation of the high-stage compressor. The feed water warming system according to claim 1 or 2. The water supply according to claim 3, wherein when the heat source fluid temperature to the high stage side evaporator exceeds a low stage side stop temperature, the low stage side compressor is stopped assuming that the setting condition is satisfied. Heating system. During the water supply to the water supply tank via the water supply path, the water flow rate is adjusted so as to maintain the outlet side water temperature of the high stage side condenser at a set temperature,
4. The low-stage compressor is stopped when the rotational speed of the pump for adjusting the water flow rate or the opening of the valve exceeds a low-stage stop value, assuming that the setting condition is satisfied. Or the feed water heating system of Claim 4. The said low stage side compressor is stopped as the said setting conditions are satisfy | filled when the water level of the said water supply tank exceeds the low stage side stop water level, The one of Claims 3-5 characterized by the above-mentioned. Water heating system. When the water level of the water supply tank is below the lower limit water level, the water supply to the water supply tank via the water supply path is started, and each compressor is started,
When the water level of the water supply tank exceeds an upper limit water level, water supply to the water supply tank via the water supply path is stopped, and the compressors are stopped. Water supply heating system according to item. 8. When starting each compressor from a stopped state, first, the high-stage compressor is started, and then the low-stage compressor is started at a set timing. The feed water heating system according to Item 1. In order to maintain the temperature difference between the heat source fluid temperature to the feed water heating heat exchanger and the outlet water temperature of the feed water warming heat exchanger at a set value, the feed water heating heat exchanger The supply water heating system according to any one of claims 1 to 8, wherein a supply flow rate of the heat source fluid is adjusted. A heat source fluid is sequentially passed through the low-stage evaporator and the high-stage evaporator in a set order,
In parallel with the supply of the heat source fluid to each of these evaporators, the heat source fluid is passed through the heat exchanger for heating the feed water,
To each evaporator and the feed water heating heat exchanger, the heat source fluid temperature after passing through each evaporator and the heat source fluid temperature after passing through the feed water heating heat exchanger are equal to each other. The feed water heating system according to any one of claims 1 to 9, wherein a distribution ratio of the heat source fluid is adjusted.

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