CN113294910A

CN113294910A - Water supply heating system

Info

Publication number: CN113294910A
Application number: CN202011555887.2A
Authority: CN
Inventors: 伊佐一马; 大下悟; 大谷和之; 大泽智也; 金丸真嘉
Original assignee: Miura Industries Co ltd
Current assignee: Miura Industries Co ltd
Priority date: 2020-02-21
Filing date: 2020-12-24
Publication date: 2021-08-24
Also published as: JP7547741B2; JP2024083505A; KR20210106878A; JP2021134933A; US20210262655A1

Abstract

The invention provides a feed water heating system. Further improvement in efficiency is sought in a feed water heating system using both a heat pump circuit and a heat recovery heat exchanger. A feed water heating system is provided with: a vapor compression heat pump circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in an annular shape by a refrigerant circulation line, and heat is taken out of the condenser by driving of the compressor; a heat exchanger for heat recovery; a heat source fluid line through which a heat source fluid flows in the order of the heat recovery heat exchanger and the evaporator; a water supply line for circulating water in the order of the heat recovery heat exchanger and the condenser; a refrigerant flow rate adjusting unit for adjusting the refrigerant flow rate by controlling the superheat degree of the gas refrigerant flowing into the compressor; a supply water flow rate adjusting unit which is controlled based on the temperature of the hot water flowing out from the condenser and adjusts the supply water flow rate; and a control unit for controlling the refrigerant flow rate adjustment unit and the water supply flow rate adjustment unit.

Description

Water supply heating system

Technical Field

The present invention relates to a feed water heating system.

Background

In recent years, in an operation site such as a factory, a mechanism for effectively utilizing unused heat discarded in various facilities has been advanced for the purpose of reducing the emission of carbon dioxide, which is a greenhouse gas. Therefore, as shown in patent documents 1 and 2, an efficient unused heat utilization system (feed water heating system) has been proposed in which the amount of fuel used in a boiler is reduced by heating boiler feed water in a heat pump circuit using waste hot water as a heat source.

Prior art documents

Patent document

Patent document 1: JP 2013-Ascherson 210118 publication

Patent document 2: JP-A2014-169819

Disclosure of Invention

The feed water heating systems described in patent documents 1 and 2 are applicable not only to heating of boiler feed water but also to heating of water used in various production processes. The system according to patent document 1 is configured to circulate a heat source fluid (waste hot water) in the order of an evaporator and a heat recovery heat exchanger, and to circulate a feed water (cold water) in the order of a heat recovery heat exchanger, a subcooler, and a condenser. With this configuration, the system according to patent document 1 has succeeded in achieving a very high COP (coefficient of performance: energy consumption efficiency) as compared with a conventional heat pump system that does not include a heat recovery heat exchanger and a subcooler. On the other hand, the system has the following problems: if the temperature of the heat source fluid becomes relatively low (for example, 40 ℃ or lower), the heat recovery heat exchanger becomes ineffective.

In contrast, the system according to patent document 2 is configured to circulate a heat source fluid (waste hot water) in the order of a heat recovery heat exchanger and an evaporator. With this configuration, in the system according to patent document 2, if the temperature of the heat source fluid is higher than that of the feed water, the effect of the heat exchanger for heat recovery cannot be exhibited to the maximum. The system according to patent document 2 can recover heat with a high COP for a heat source fluid in a wide temperature range, but is expected to be more efficient in the event of an operation that aims to reduce the amount of carbon dioxide emission to a high standard.

The present invention has been made in view of the above problems, and an object thereof is to achieve further high efficiency in a feed water heating system using both a heat pump circuit and a heat recovery heat exchanger.

Means for solving the problems

The present invention relates to a feed water heating system, comprising: a vapor compression heat pump circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in an annular manner by a refrigerant circulation line, and heat is taken out of the condenser by driving of the compressor; a heat exchanger for heat recovery; a heat source fluid line through which a heat source fluid flows in the order of the heat recovery heat exchanger and the evaporator; a water supply line for circulating water in the heat recovery heat exchanger and the condenser in this order; a refrigerant flow rate adjusting unit which is controlled based on the superheat degree of the gas refrigerant flowing into the compressor and adjusts the refrigerant flow rate; a supply water flow rate adjusting unit which is controlled based on the temperature of the hot water flowing out from the condenser and adjusts the supply water flow rate; and a control unit for controlling the refrigerant flow rate adjustment unit and the water supply flow rate adjustment unit.

Further, preferably, the heat source fluid line is a connection structure of: the heat recovery heat exchanger exchanges heat between the heat source fluid and the water supply by means of the reverse flow, and then exchanges heat between the heat source fluid and the liquid refrigerant by means of the reverse flow in the evaporator.

Further, it is preferable to provide: a suction temperature sensor for detecting a suction temperature of a gas refrigerant flowing into the compressor; a vapor pressure sensor for detecting vapor pressure of the gas refrigerant flowing out of the evaporator; and a hot water outlet temperature sensor for detecting a hot water outlet temperature of the water supplied from the condenser, wherein the control unit calculates an evaporation temperature of the liquid refrigerant based on a detection pressure of the vapor pressure sensor, calculates a degree of superheat of the gas refrigerant by subtracting the evaporation temperature from a detection temperature of the suction temperature sensor, controls the refrigerant flow rate adjustment unit so that the calculated degree of superheat becomes a target degree of superheat, and controls the water supply flow rate adjustment unit so that the detection temperature of the hot water outlet temperature sensor becomes the target hot water outlet temperature.

Further, it is preferable to provide: and a heat source temperature sensor that detects a temperature of the heat source fluid before flowing into the evaporator, the control unit setting the target superheat degree corresponding to the detected temperature of the heat source temperature sensor.

Further, it is preferable that the control means increases the target superheat degree when it is determined that the variation in the detected temperature of the heat source temperature sensor is large.

Further, it is preferable that the control unit decreases the target superheat degree when it is determined that the detected temperature of the heat source temperature sensor is stable.

Further, it is preferable to provide: a supply water temperature sensor that detects a temperature of the supply water before flowing into the condenser, the control unit setting the target hot water temperature corresponding to the detected temperature of the supply water temperature sensor.

Further, it is preferable to provide: and a feed water temperature sensor that detects a temperature of feed water before flowing into the condenser, wherein the target hot water temperature is set to a value between an upper limit value and a lower limit value, the lower limit value being a value obtained by adding a predetermined value to a detected temperature of the feed water temperature sensor and being a value that increases as the detected temperature of the feed water temperature sensor increases.

Further, it is preferable to provide: 1 or 2 bypass lines for bypassing the water supply with respect to the heat recovery heat exchanger and/or bypassing the heat source fluid with respect to the heat recovery heat exchanger; and a preheating mode switching unit that switches between a supply water preheating mode in which the supply water and the heat source fluid are simultaneously circulated to the heat recovery heat exchanger and a preheating stop mode in which at least one of the supply water and the heat source fluid is circulated to the bypass line.

Further, it is preferable to provide: a heat exchanger pre-inflow water supply temperature sensor that detects a temperature of the water supply before flowing into the heat recovery heat exchanger; and a heat exchanger inflow front heat source temperature sensor that detects a temperature of the heat source fluid before flowing into the heat recovery heat exchanger, wherein the control unit compares a 1 st detected temperature of the heat exchanger inflow front water supply temperature sensor with a 2 nd detected temperature of the heat exchanger inflow front heat source temperature sensor, controls the warm-up mode switching unit so that the supply water warm-up mode is performed in a case where the 1 st detected temperature is lower than the 2 nd detected temperature, and controls the warm-up mode switching unit so that the warm-up stop mode is performed in a case where the 1 st detected temperature is higher than the 2 nd detected temperature.

Further, it is preferable that the control unit includes: a signal input unit that receives a warm-up mode designation signal for designating a type of the supply water warm-up mode or the warm-up stop mode; and a preheating mode switching control part which controls the preheating mode switching unit according to the preheating mode designation signal inputted to the signal input part so that the water supply preheating mode or the preheating stop mode is executed.

Effects of the invention

According to the present invention, in a feed water heating system using both a heat pump circuit and a heat recovery heat exchanger, further high efficiency can be achieved.

Drawings

Fig. 1 is a diagram schematically showing a feed water heating system according to an embodiment of the present invention.

Fig. 2 is a block diagram showing the control unit of the above embodiment.

Fig. 3 is a graph showing the variation of the detected temperature of the heat source temperature sensor.

Fig. 4 is a diagram showing the settable range of the target hot water temperature in the above embodiment.

Fig. 5 is a mollier diagram for explaining a heat pump cycle.

Fig. 6A is a state transition diagram of the water passage mode switching control in the above embodiment.

Fig. 6B is a flowchart showing the flow of the target superheat setting process in the above embodiment.

Fig. 6C is a flowchart showing a flow of the warm-up mode switching control in the above embodiment.

Fig. 7 is a diagram schematically showing a feed water heating system according to a modification of the above embodiment.

Description of the reference numerals

1 Water supply heating System

10 Heat Pump Circuit

11 compressor

12 condenser

12A condenser

12B subcooler

13 expansion valve (refrigerant flow adjusting unit)

14 evaporator

17 inhalation temperature sensor

18 steam pressure sensor

21 Water supply pump (supply water flow adjusting unit, water-passing mode switching unit)

24 the 1 st water supply temperature sensor (water supply temperature sensor before heat exchanger inflow)

25 three-way valve (preheating mode switching unit)

26 nd 2 supply water temperature sensor (supply water temperature sensor)

27 hot water temperature sensor

31 reflux pump (supply water flow adjusting unit, water-passing mode switching unit)

40 Heat exchanger for heat recovery

50 heat source water tank

53 heat source supply pump

54 heat source temperature sensor 1 st (heat source temperature sensor before heat exchanger inflow)

55 nd 2 heat source temperature sensor (heat source temperature sensor)

60 hot water pot

61 hot water temperature sensor

62 water level detecting part

63 Hot water supply pump

70 make-up water tank

100 control part

111 target superheat setting unit

112 degree of superheat calculation unit

113 refrigerant flow control part

Determination unit for setting range of 121 target hot water temperature

122 target outlet hot water temperature setting unit

123 feed water flow control part

130 water-flowing mode switching control part

140 preheating mode switching control part

150 signal input part

151 st signal input part

152 nd signal input part

L1 Water supply line

L2 Return line

L3 bypass line

L4 hot water supply line

L5 Heat Source fluid line

L9 refrigerant circulating pipeline

R refrigerant (gas refrigerant, liquid refrigerant)

W make-up water

W1 water supply

W2 Hot Water

W5 Heat source water (Heat source fluid)

Detailed Description

Hereinafter, a preferred embodiment of the feed water heating system 1 according to the present invention will be described with reference to the drawings. In the present specification, the term "line" refers to a general term for a line through which a fluid such as a channel, a passage, or a pipe can flow.

Fig. 1 is a diagram schematically showing the configuration of a feed water heating system 1 according to the present embodiment. As shown in fig. 1, the feed water heating system 1 is a system in which the feed water W1 heated by the heat recovery heat exchanger 40 and the heat pump circuit 10 is supplied as hot water W2 to a hot water-requiring site.

More specifically, the feed water heating system 1 of the present embodiment includes: a makeup water tank 70 for storing makeup water W used as supply water W1; a heat recovery heat exchanger 40 and a heat pump circuit 10 that heat the feed water W1; a hot water tank 60 for storing the heated feed water W1 as hot water W2; and a heat source water tank 50 for storing heat source water W5 as a heat source fluid.

The feed water heating system 1 of the present embodiment further includes: a water supply line L1 that circulates the water supply W1 in the order of the heat recovery heat exchanger 40 and the condenser 12 of the heat pump circuit 10; a return line L2 that returns the hot water W2 in the hot water tank 60 to the upstream side of the heat recovery heat exchanger 40; a bypass line L3 that bypasses the feed water W1 to the heat recovery heat exchanger 40; a hot water supply line L4 for supplying hot water W2 in the hot water tank 60 to a hot water-requiring portion; and a heat source fluid line L5 that allows heat source water W5 as a heat source fluid to flow through the heat recovery heat exchanger 40 and the evaporator 14 of the heat pump circuit 10.

The makeup water tank 70 is a tank that stores makeup water W used as supply water W1 heated by the heat recovery heat exchanger 40 and the heat pump circuit 10, and is connected to a water supply line L1.

The heat recovery heat exchanger 40 is an indirect heat exchanger that performs indirect heat exchange between the supply water W1 flowing in the supply water line L1 and the heat source water W5 flowing in the heat source fluid line L5. More specifically, the heat recovery heat exchanger 40 exchanges heat between the feed water W1 before passing through the condenser 12 of the heat pump circuit 10 and the heat source water W5 before passing through the evaporator 14 of the heat pump circuit 10.

The feed water W1 of the water supply line L1 passes through the heat recovery heat exchanger 40 and the condenser 12 in this order, and the heat source water W5 of the heat source fluid line L5 passes through the heat recovery heat exchanger 40 and the evaporator 14 in this order.

The heat pump circuit 10 is a vapor compression type heat pump circuit, and is configured such that a compressor 11, a condenser 12, an expansion valve 13, and an evaporator 14 are annularly connected by a refrigerant circulation line L9, and heat is extracted from the condenser 12 by driving the compressor 11. The refrigerant R flows through the refrigerant circulation line L9.

The compressor 11 has an electric motor 15 as a drive source, and compresses a gaseous refrigerant R such as freon gas to a high-temperature high-pressure refrigerant R. The condenser 12 radiates heat to the feed water W1 fed through the feed water line L1, and condenses and liquefies the refrigerant R from the compressor 11. The expansion valve 13 reduces the pressure and temperature of the refrigerant R by passing the refrigerant R sent from the condenser 12. The evaporator 14 absorbs heat from the heat source water W5 sent through the heat source fluid line L5, and evaporates the refrigerant R sent from the expansion valve 13.

As described above, in the heat pump circuit 10, the refrigerant R takes heat from the outside and evaporates in the evaporator 14, while the refrigerant R releases heat to the outside and condenses in the condenser 12. By utilizing such a principle, in the heat pump circuit 10, heat is drawn from the heat source water W5 in the evaporator 14, and the feed water W1 of the feed water line L1 is heated in the condenser 12.

The refrigerant circulation line L9 of the heat pump circuit includes: a suction temperature sensor 17 for detecting a suction temperature of the gas refrigerant R flowing into the compressor 11; and a vapor pressure sensor 18 for detecting a vapor pressure of the gas refrigerant R flowing out of the evaporator 14.

Here, the expansion valve 13 constitutes refrigerant flow rate adjusting means for adjusting the flow rate of the refrigerant R flowing through the refrigerant circulation line L9 of the heat pump circuit 10. Specifically, the expansion valve 13 is configured as a proportional control type needle valve, and the stroke of the needle valve can be changed by controlling the rotational speed of the drive stepping motor, and the flow rate of the refrigerant R can be adjusted by adjusting the opening degree of the valve.

The hot water tank 60 is a tank that stores the supply water W1 heated by the heat recovery heat exchanger 40 and the heat pump circuit 10 as hot water W2.

The hot water W2 stored in the hot water tank 60 can be circulated for heating. Specifically, the hot water W2 in the hot water tank 60 can merge with the water supply line L1 through the return line L2, and can be heated by passing through the heat recovery heat exchanger 40 and the condenser 12 again through the water supply line L1, and returned to the hot water tank 60.

The hot water tank 60 is provided with a hot water temperature sensor 61 that detects the temperature of the hot water W2 in the hot water tank 60. The hot water tank 60 is provided with a water level detector 62 for detecting the water level in the hot water tank 60. In the present embodiment, the water level detector 62 includes an electrode type water level detector including a plurality of electrode rods. Specifically, 2

electrode rods

621 and 622 having different lengths are inserted and held at different height positions of the lower end portions thereof. In the present embodiment, the

electrode rods

621 and 622 are inserted into the hot water tank 60 in order with the lower end portions lowered in height. Each of the

electrode rods

621 and 622 detects the presence or absence of water level at the lower end portion by whether or not the lower end portion is immersed in water.

In the present embodiment, the control unit 100 performs switching control of the water flow mode, which will be described later, using the detection results of the hot water temperature sensor 61 and the water level detection unit 62. The control content will be described in detail later.

The heat source water tank 50 stores heat source water W5 as a heat source fluid of the heat pump circuit 10. As the heat source water W5, for example, waste hot water from a factory is used. An overflow line, not shown, for overflowing the heat source water of a predetermined level or more is provided in the heat source water tank 50. The heat source water tank 50 is provided with a water level detector, not shown, for monitoring that the heat source water is not lower than a predetermined low water level.

The water supply line L1 has its upstream side connected to the makeup water tank 70 and its downstream side connected to the hot water tank 60. Further, the water supply line L1 includes, in order from the upstream side, a water supply pump 21, a 1 st check valve 23, a 1 st water supply temperature sensor 24, a three-way valve 25 disposed at a bypass line branching portion, a heat recovery heat exchanger 40, a 2 nd water supply temperature sensor 26, a condenser 12, and a hot water discharge temperature sensor 27.

The water supply pump 21 can control the rotation speed by an inverter. By changing the rotational speed of the water supply pump 21, the flow rate of the supplied water to the hot water tank 60 via the water supply line L1 can be adjusted in the case of the one-pass water supply mode described later. That is, the feed pump 21 constitutes a feed water flow rate adjusting means in the water passing mode.

The 1 st check valve 23 is provided upstream of the junction of the return line L2 described later. This prevents the hot water W2 from flowing into the makeup water tank 70 in the circulation water flow mode described later.

The 1 st feed water temperature sensor 24 is a heat exchanger pre-inflow feed water temperature sensor that detects the temperature of the feed water W1 before flowing into the heat recovery heat exchanger 40. The 1 st feed water temperature sensor 24 is provided upstream of the branch portion of the bypass line L3.

The three-way valve 25 is disposed at the branch portion of the bypass line L3. The three-way valve 25 is a means for switching whether or not the feed water W1 is bypassed with respect to the heat recovery heat exchanger 40, and constitutes a warm-up mode switching means. The bypass line L3 is a bypass line that bypasses the feed water W1 with respect to the heat recovery heat exchanger 40.

The 2 nd feed water temperature sensor 26 is a feed water temperature sensor that detects the temperature of the feed water W1 before flowing into the condenser 12 of the heat pump circuit 10. The 2 nd feed water temperature sensor 26 is disposed upstream of the condenser 12, and in the present embodiment, downstream of the heat recovery heat exchanger 40.

The hot water temperature sensor 27 detects the hot water temperature of the heated supply water W1 flowing out of the condenser 12.

The return line L2 has its upstream side connected to the hot water tank 60 and its downstream side connected to the water supply line L1. The reflux pump 31 (circulation pump 31) and the 2 nd check valve 33 are disposed in this order from the upstream side in the reflux line L2.

The reflux pump 31 can control the rotation speed by an inverter. By changing the rotational speed of the return pump 31, the feed water flow rate that circulates through the return line L2 and the feed water line L1 and returns to the hot water tank 60 can be adjusted in the circulation water flow pattern described later. That is, the reflux pump 31 constitutes a feed water flow rate adjusting means in the circulation water passing mode.

The 2 nd check valve 33 is provided in the return line L2 on the upstream side of the junction of the water supply line L1 and the return line L2. This prevents the makeup water W from the makeup water tank 70 from flowing into the hot water tank 60 in the first water passage mode described later.

By providing the water supply line L1 and the return line L2 as described above, when the water supply pump 21 is operated with the return pump 31 stopped, the makeup water W from the makeup water tank 70 can be supplied to the hot water tank 60 as the water supply W1 while passing through and heating the heat recovery heat exchanger 40 and the condenser 12 in this order. This is referred to as a through water mode. On the other hand, when the return pump 31 is operated in a state where the water supply pump 21 is stopped, the hot water W2 in the hot water tank 60 can be returned to the hot water tank 60 as the feed water W1 while passing through the heat recovery heat exchanger 40 and the condenser 12 in this order and reheating the water, thereby circulating the stored water in the hot water tank 60. This is referred to as a circulation water mode. When both the water supply pump 21 and the return pump 31 are stopped, the water supply to the heat exchanger 40 for heat recovery and the condenser 12 can be stopped. This is referred to as a water-passage stop mode.

That is, in the present embodiment, the water supply pump 21 and the return pump 31 constitute water passage mode switching means for switching: a water passing mode in which the hot water W2 is passed through the condenser 12 without passing through the return line L2; a circulation water passing mode in which hot water W2 is passed through the return line L2 and water is passed through the condenser 12; and a water supply stop mode in which the water supply to the condenser 12 is stopped.

The hot water W2 in the hot water tank 60 is supplied to a hot water-requiring portion through the hot water supply line L4.

A hot water supply pump 63 is provided in the hot water supply line L4. As an example of the hot water demand site, water supply utilization of a steam boiler is given. However, the destination of use of the hot water W2 is not limited to the steam boiler. For example, the hot water W2 produced by the water supply heating system 1 of the present embodiment can be used for container cleaning for food, beverage, and medicine, pasteurization (bottle sterilization), and the like. In this case, the supply of the hot water W2 in the high temperature range of about 60 to 80 ℃ may be always required. According to the feed water heating system 1 of the present embodiment, in an application requiring the supply of hot water having a temperature within such a predetermined temperature range, for example, in a system in which only the heated feed water W1 is supplied into the hot water tank 60 (a system in which unheated makeup water is not directly supplied into the hot water tank 60), it is possible to efficiently heat hot water particularly suitably and supply the heated makeup water while maintaining the temperature.

The heat source supply pump 53, the 1 st heat source temperature sensor 54, the heat recovery heat exchanger 40, the 2 nd heat source temperature sensor 55, and the evaporator 14 are arranged in this order from the upstream side in the heat source fluid line L5.

By operating the heat source supply pump 53, the heat source water W5 from the heat source water tank 50 can be circulated in the order of the heat recovery heat exchanger 40 and the evaporator 14.

The 1 st heat source temperature sensor 54 is a heat exchanger inflow pre-heat source temperature sensor that detects the temperature of the heat source water W5 before flowing into the heat recovery heat exchanger. In the present embodiment, the 1 st heat source temperature sensor 54 is provided in the heat source fluid line L5, but this sensor may be provided in the heat source water tank 50.

The 2 nd heat source temperature sensor 55 is a heat source temperature sensor that detects the temperature of the heat source fluid that exchanges heat with the refrigerant R in the evaporator 14. In the present embodiment, the temperature of the heat source water W5 before flowing into the evaporator 14 is detected. The 2 nd heat source temperature sensor 55 is disposed upstream of the evaporator 14, and in the present embodiment, downstream of the heat recovery heat exchanger 40.

As described above, the heat source fluid line L5 has a connection structure in which the heat source water W5 flows in the order of the heat recovery heat exchanger 40 and the evaporator 14.

In this way, by making the heat source water W5 flow to the heat recovery heat exchanger 40 first, the amount of preheating of the feed water W1 can be increased, and the heat output of the heat recovery heat exchanger 40 can be improved. The higher the temperature of the heat source water W5, the greater the effect of increasing the heat output.

Further, as shown in fig. 1, the heat source fluid line L5 becomes the following connection structure: after heat exchange is performed between heat source water W5 and feed water W1 by Counter flow in heat recovery heat exchanger 40, heat exchange is performed between heat source water W5 and liquid cooling medium R by Counter flow in evaporator 14.

In this way, the heat recovery amount can be maximized by causing the heat source water W5 to flow in the order of the heat recovery heat exchanger 40 and the evaporator 14 and causing the heat recovery heat exchanger 40 and the evaporator 14 to flow in a counter-flow manner with respect to the flow direction of the feed water W1.

Next, the control unit 100 of the feed water heating system 1 according to the embodiment will be described. Fig. 2 is a block diagram of the control unit 100 as the control means of the feed water heating system 1 of the present embodiment. The control unit 100 includes: a target superheat setting unit 111, a superheat calculation unit 112, a refrigerant flow rate control unit 113, a target outlet hot water settable range determination unit 121, a target outlet hot water setting unit 122, a feed water flow rate control unit 123, a water feed mode switching control unit 130, a warm-up mode switching control unit 140, a signal input unit 150, and a storage unit 160.

The target superheat setting unit 111 obtains the temperature of the heat source water W5 as the heat source fluid detected by the 2 nd heat source temperature sensor 55 as the heat source temperature sensor, sets the target superheat in accordance with the detected temperature of the 2 nd heat source temperature sensor 55, and sets the target superheat to be low when the temperature of the heat source water W5 as the heat source fluid is low. This increases the circulation flow rate of the refrigerant R, and increases the heat recovery amount even when the temperature of the heat source water W5 is low.

By setting an appropriate target superheat degree in accordance with the temperature of the heat source water W5 serving as the heat source fluid in this way, it is possible to increase the heat recovery amount in the evaporator 14 while preventing damage to the compressor 11 due to liquid compression and lubrication failure.

Further, the target superheat setting unit 111 may perform control to increase the target superheat degree when it is determined that the variation in the detected temperature of the 2 nd heat source temperature sensor 55 is large.

Fig. 3 is a graph in which the vertical axis represents the detected temperature T of the 2 nd heat-source temperature sensor 55 and the horizontal axis represents time T, and the graph shows the variation in the detected temperature of the 2 nd heat-source temperature sensor 55. For example, as shown in fig. 3, when the amount of change Δ T per unit time T0 in the detected temperature T of the 2 nd heat-source temperature sensor 55 is higher than a predetermined threshold value Δ T0, it is determined that the variation in the detected temperature T of the 2 nd heat-source temperature sensor 55 is large, and control is performed to increase the target degree of superheat. For example, when Δ T0 is 5 ℃ and T0 is 1min, the control is performed to increase the target superheat degree when there is a fluctuation larger than 5 ℃/min. In this case, for example, when the target degree of superheat up to this point is set to 5 ℃, the target degree of superheat is set to, for example, 10 ℃. In the example of fig. 3, the decrease amount Δ T of the detected temperature T per unit time T0 is larger than a given threshold value Δ T0. Then, since it is considered that the temperature of the heat source water W5 is suddenly changed, the target superheat degree is changed to, for example, 10 ℃.

Thus, even when a situation in which the temperature of the heat source water W5 as the heat source fluid is rapidly changed is confirmed, the heat pump circuit 10 can be stably driven.

For example, even when the temperature of the heat source water W5 rapidly decreases due to a rapid change in temperature, the refrigerant R can be reliably vaporized in the evaporator 14 by setting the target superheat degree to a high value, and thus damage to the compressor 11 due to liquid compression can be prevented.

Further, the target superheat setting unit 111 may perform control to reduce the target superheat degree when it is determined that the temperature detected by the 2 nd heat source temperature sensor 55 is stable.

For example, when the detected temperature T of the 2 nd heat-source temperature sensor 55 is within a range of a given temperature for a given time, it is determined that the detected temperature of the 2 nd heat-source temperature sensor 55 is stable. Further, it may be determined that the detected temperature of the 2 nd heat source temperature sensor 55 is stable when the amount of change Δ T of the detected temperature T per unit time T0 in a given time is lower than a given threshold value Δ T0. At this time, control is performed to reduce the target superheat degree. For example, when the target degree of superheat up to this point is set to 10 ℃, the target degree of superheat is changed to, for example, 5 ℃.

Further, by setting the lower limit of the target degree of superheat to, for example, 5 ℃, it is possible to prevent the compressor 11 from being damaged by liquid compression. Further, by setting the upper limit value of the target degree of superheat to, for example, 10 ℃, the circulation flow rate of the refrigerant R can be maintained at a predetermined flow rate or more, and a decrease in the heat recovery amount can be prevented.

In this way, when the temperature of the heat source water W5 as the heat source fluid is stable, the target superheat degree is set to a low value, whereby the circulation flow rate of the refrigerant R can be increased, and the heat recovery amount in the evaporator 14 can be increased.

In the present embodiment, the temperature detected by the 2 nd heat source temperature sensor 55 is used as the heat source temperature sensor for setting the target degree of superheat, but the 1 st heat source temperature sensor 54 may be used as the heat source temperature sensor for detecting the temperature of the heat source water W5 before flowing into the evaporator 14 (the evaporator inflow front heat source temperature). The 1 st heat source temperature sensor 54 may indirectly detect the temperature of the heat source fluid that exchanges heat with the refrigerant R in the evaporator 14, and may check that the temperature of the heat source water W5 has suddenly changed, although not just before the heat source fluid flows into the evaporator 14. Among these, the 2 nd heat source temperature sensor 55 is more preferably used to measure the temperature of the heat source water W5 immediately before flowing into the evaporator 14.

The superheat calculation unit 112 calculates the degree of superheat of the refrigerant R flowing into the compressor 11.

Specifically, the superheat degree calculation unit 112 calculates the degree of superheat of the gas refrigerant R by calculating the evaporation temperature of the liquid refrigerant R from the detection pressure of the vapor pressure sensor 18 and subtracting the evaporation temperature from the detection temperature of the suction temperature sensor 17.

The refrigerant flow rate control unit 113 controls the refrigerant flow rate control means to adjust the flow rate of the refrigerant R so that the calculated superheat (the calculated value by the superheat calculation unit 112) becomes the target superheat (the set value by the target superheat setting unit 111).

As a specific control, for example, the following feedback control is preferably employed: the valve opening degree of the expansion valve 13 is adjusted so that the calculated superheat degree is converged to the target superheat degree, using the calculated superheat degree calculated in real time by the superheat degree calculation unit 112 as a feedback value. In addition to the proportional control (P control), the feedback control may employ an arithmetic algorithm combining the operation amounts of the integral control (I control) and/or the derivative control (D control).

In this way, the superheat degree of the gas refrigerant R is accurately calculated by the superheat degree calculating unit 112, and the refrigerant flow rate controlling unit 113 controls the calculated value so as to be constant, whereby the heat output of the condenser 12 to the feed water W1 is stabilized. This reduces the fluctuation in the flow rate of the feed water W1 to be heated and supplied as hot water.

The target hot water temperature settable range determining unit 121 obtains the temperature of the feed water W1 before flowing into the condenser 12, which is detected by the feed water temperature sensor 2, and determines the settable range of the target hot water temperature according to the temperature detected by the feed water temperature sensor 2.

Fig. 4 is a diagram showing a settable range of the target hot water temperature determined in accordance with the detected temperature of the 2 nd feed water temperature sensor 26. The abscissa of fig. 4 represents the detected temperature (condenser inflow water temperature) of the 2 nd feed water temperature sensor 26, and the ordinate represents the target hot water temperature corresponding thereto.

The settable range of the target hot water temperature in the present embodiment is a triangular region indicated by the settable range a. That is, in the present embodiment, the target hot water temperature can be set to a value between the upper limit value and the lower limit value, the lower limit value being a value obtained by adding a predetermined value to the temperature detected by the 2 nd feed water temperature sensor 26 and being a value that is higher as the temperature detected by the 2 nd feed water temperature sensor 26 is higher. More specifically, the lower limit is a value obtained by adding 15 ℃ to the temperature detected by the 2 nd feed water temperature sensor 26, and the upper limit is a fixed temperature, in this embodiment, 75 ℃.

In addition, a predetermined value (for example, 15 ℃) for setting the lower limit value is stored in a storage section 160 described later. In this case, the given value can be preferably set by an external input or the like. Alternatively, a lower limit value based on the given value may be stored in the storage unit 160.

In this way, by setting the region indicated by the settable range a as the settable range of the target hot water temperature, the system is controlled so that the temperature difference between the inlet side and the outlet side of the condenser 12 of the feed water W1 is sufficiently large, and therefore, the refrigerant R flowing through the heat pump circuit 10 can be prevented from being insufficiently supercooled, and the feed water W1 can be suppressed from being excessively supplied with the feed water flow rate adjusting means under control by the feed water flow rate control unit 123 described later.

Even when the settable range of the target hot water temperature is a rectangular region in which both the upper limit value and the lower limit value are fixed values, that is, even when the lower limit value is fixed, if the settable range B shown in fig. 4 is set, for example, the supercooled state of the refrigerant R can be prevented and the feed water W1 can be prevented from flowing excessively. However, in this case, the allowable range of the heat source water temperature and the settable range of the target hot water temperature become narrow.

In addition, when the target hot water temperature is set to a temperature lower than the lower limit value indicated by the energy setting range a, for example, when the temperature detected by the 2 nd feed water temperature sensor 26 does not change much, the supercooling shortage of the refrigerant R may occur.

This will be described with reference to a mollier diagram (p-h diagram) shown in fig. 5.

The ordinate of the mollier diagram indicates the pressure (p) of the refrigerant, and the abscissa indicates the specific enthalpy (h) of the refrigerant. In the mollier diagram, a saturated liquid line Y1 and a saturated vapor line Y2 are shown. Such a mollier diagram can represent a change in the state of the refrigerant R in the heat pump cycle. The refrigerant R is in a supercooled liquid state (state of the liquid refrigerant R) on the left side of the saturated liquid line Y1, in a wet vapor state, which is a gas-liquid mixed state, between the saturated liquid line Y1 and the saturated vapor line Y2, and in a superheated vapor state (state of the gas refrigerant R) on the right side of the saturated vapor line Y2.

In fig. 5, a solid line indicated by R (a → b → c → d) indicates a transition of the state of the refrigerant R in the heat pump cycle in an appropriate state.

The gas refrigerant R in the superheated vapor state sucked by the compressor 11 is adiabatically compressed in the compressor 11 to become the gas refrigerant R in the superheated vapor state of high temperature and high pressure (a → b), then passes through the liquid refrigerant R in the supercooled liquid state (b → c) condensed/supercooled in the condenser 12, and further passes through the expansion valve 13 to adiabatically expand, thereby becoming the refrigerant R in the wet vapor state (c → d). Then, the refrigerant R in the wet vapor state is evaporated and heated in the evaporator 14, and becomes a gas refrigerant R in a superheated vapor state (d → a). In such a cycle, the refrigerant R circulates. In addition, describing the process of (b → c) in fig. 5 in detail, the condenser 12 releases latent heat and sensible heat of the gas refrigerant R, changes the gas refrigerant R into the liquid refrigerant R, and supercools the liquid refrigerant R.

Here, when the target hot water temperature is set to a temperature lower than the lower limit value indicated by the energy setting range a, the refrigerant R may not be sufficiently condensed/supercooled in the condenser 12 because the temperature difference between the inlet-side and outlet-side feed water W1 of the condenser 12 is small (b → c'). As a result, the position of "c'" indicating the state of the refrigerant R after passing through the condenser 12 is shifted to the right side from the proper position. That is, the refrigerant R in the state of "c" is insufficiently supercooled. Further, the liquid refrigerant R may not be sufficiently in a state. In this case, it cannot be said that the operation can be performed by an appropriate heat pump cycle.

However, in the present embodiment, since the lower limit value is set to a value obtained by adding a predetermined value to the temperature detected by the 2 nd feed water temperature sensor 26, the system is controlled so that the temperature difference between the feed water W1 on the inlet side and the outlet side of the condenser 12 is larger than at least the predetermined value, and the above-described problem does not occur. That is, the heat pump cycle can be operated in an appropriate state.

The target hot water temperature setting unit 122 sets the target hot water temperature within the above-described target hot water temperature settable range in accordance with the detected temperature of the 2 nd feed water temperature sensor 26. For example, an arbitrary target hot water outlet temperature can be set within the above-described settable range a based on a request of a hot water required portion or the like.

That is, the target outlet hot water temperature setting unit 122 can acquire the detected temperature of the 2 nd supply water temperature sensor 26, and set the target outlet hot water temperature by setting a value obtained by adding a predetermined value to the acquired detected temperature of the 2 nd supply water temperature sensor 26 and a value that increases as the detected temperature of the 2 nd supply water temperature sensor 26 increases, as the lower limit value. This makes it possible to operate the heat pump cycle in an appropriate state and to widen the setting range of the target outlet hot water temperature.

Further, a value obtained by adding a predetermined value to the temperature detected by the 2 nd feed water temperature sensor 26 may be automatically set as the target hot water temperature.

The feed water flow rate control unit 123 controls the feed water flow rate adjusting means to adjust the flow rate of the feed water W1 so that the temperature detected by the hot water temperature sensor 27 becomes the target hot water temperature (the set value of the target hot water temperature setting unit 122).

As a specific control, for example, the following feedback control is preferably employed: the hot water temperature detected in real time by the hot water temperature sensor 27 is used as a feedback value, and the driving frequency of the water supply pump 21 or the return pump 31 is adjusted so that the hot water temperature converges to the target hot water temperature. In addition to the proportional control (P control), the feedback control may employ an arithmetic algorithm combining the operation amounts of the integral control (I control) and/or the derivative control (D control).

In the one-pass water mode described later, the water supply pump 21 capable of performing the inverter control constitutes supply water flow rate adjusting means, and in the circulation water-pass mode, the return pump 31 capable of performing the inverter control constitutes supply water flow rate adjusting means.

The supply water flow rate adjusting means may be configured in other forms. For example, when the water supply pump 21 and the return pump 31 are constituted by pumps capable of on/off control only, flow rate adjustment valves capable of proportional control may be provided downstream of the respective pumps, and these may be used as supply water flow rate adjustment means. Further, a flow rate adjusting valve capable of proportional control may be provided downstream of the junction of the water supply line L1 and the return line L2 as the supply water flow rate adjusting means.

Further, as an alternative configuration to the water supply pump 21 and the return pump 31, a pump capable of performing inversion control may be provided as the supply water flow rate adjusting means on the downstream side of the junction of the water supply line L1 and the return line L2 in addition to the provision of an on-off valve in the water supply line L1 and the return line L2 or in addition to the provision of a three-way valve in the junction of the water supply line L1 and the return line L2.

By setting an appropriate target hot water outlet temperature in accordance with the temperature of the feed water W1 before flowing into the condenser 12 in this way, it is possible to prevent the occurrence of an overcooling deficiency in the condenser 12, an excessive feed water flow rate, and the like.

Further, by setting the lower limit value of the range of the target hot water outlet temperature that can be set in accordance with the temperature of the feed water W1 before flowing into the condenser 12, it is possible to reliably prevent the supercooling shortage in the condenser 12 and stabilize the heat recovery amount in the evaporator 14. Further, the flow rate of the feed water W1 can be prevented from being excessive, and deterioration due to an overload of the feed water pump 21 and the like can be suppressed.

In the present embodiment, the temperature detected by the 2 nd feed water temperature sensor 26 is used for setting the target hot water temperature, but the 1 st feed water temperature sensor 24 may be used as a feed water temperature sensor that indirectly detects the temperature of the feed water W1 before flowing into the condenser 12 (the feed water temperature before flowing into the condenser). In order to perform more stable control, it is preferable to measure the temperature of the feed water W1 immediately before flowing into the condenser 12 using the 2 nd feed water temperature sensor 26.

As described above, in the feed water heating system 1 of the present embodiment, the heat source water W5 flows in the order of the heat recovery heat exchanger 40 and the evaporator 14. The feedwater heating system 1 of the present embodiment includes a refrigerant flow rate adjusting unit that adjusts the refrigerant flow rate while being controlled based on the degree of superheat of the gas refrigerant R flowing into the compressor 11. The water supply flow rate adjusting means is also provided that adjusts the water supply flow rate by being controlled based on the hot water temperature of the water supply W1 flowing out of the condenser 12. The control unit 100 further includes: a refrigerant flow control part 113 for controlling the refrigerant flow adjusting unit; and a water supply flow rate control part 123 for controlling the water supply flow rate adjusting unit.

Accordingly, the heat output of the heat recovery heat exchanger 40 is increased and the preheating amount of the feed water W1 is increased by causing the heat source water W5 to flow to the heat recovery heat exchanger 40 first. In addition, the higher the temperature of the heat source water, the greater the effect of increasing the heat output. If the heat recovery amount of the heat recovery heat exchanger 40 increases, the heat recovery amount of the heat pump circuit 10 can be relatively reduced. That is, when the same system heat output as that in the case where the heat source water W5 is caused to flow in the order of the evaporator 14 and the heat recovery heat exchanger 40 is obtained, the output of the compressor can be reduced, and the power consumption of the heat pump circuit 10 can be reduced.

At this time, although the temperature of the heat source water W5 flowing into the evaporator 14 is lowered by causing the heat source water W5 to flow first into the heat recovery heat exchanger 40, in the structure in which the heat source water W5 flows first into the heat recovery heat exchanger 40 by the multiple effect of adding further control, that is, the multiple effect of the combination of the adjustment of the refrigerant flow rate based on the degree of superheat and the adjustment of the feed water flow rate based on the hot water temperature, for example, the multiple effect of the further increase of the heat output of the heat recovery heat exchanger 40 and the increase of the heat output of the evaporator 14 by the adjustment of the refrigerant flow rate corresponding to the setting of a low degree of superheat and the adjustment of the feed water flow rate corresponding to the setting of a low hot water temperature, the COP of the system can be greatly improved.

The water passage mode switching control unit 130 performs water passage mode switching control for switching the one-pass water passage mode, the circulation water passage mode, and the water passage stop mode. More specifically, the water supply mode switching control unit 130 controls the water supply pump 21 and the return pump 31 as the water supply mode switching means to switch between a water passing mode in which the hot water W2 is passed to the condenser 12 without passing through the return line L2, a circulation water passing mode in which the hot water W2 is passed to the return line L2 and the water is passed to the condenser 12, and a water passage stop mode in which the water passage to the condenser 12 is stopped.

In the water passing mode, the drive of the reflux pump 31 is stopped, and the water supply pump 21 is driven to drive the heat source supply pump 53 and the compressor 11 of the heat pump circuit 10. In the circulation water supply mode, the drive of the water supply pump 21 is stopped, and the heat source supply pump 53 and the compressor 11 of the heat pump circuit 10 are driven by driving the reflux pump 31. In the water flow stop mode, the drive of the water supply pump 21 and the return pump 31 is stopped, and the drive of the compressor 11 of the heat pump circuit 10 is also stopped. It is preferable to stop the driving of the heat source supply pump 53.

In the present embodiment, the water supply pump 21 and the return pump 31 constitute the water passage mode switching means, but the water passage mode switching means may be constituted by another form. For example, the water passage mode switching unit may be constituted by a three-way valve provided at the junction of the water supply line L1 and the return line L2, and a water supply pump provided downstream of the junction of the water supply line L1 and the return line L2. In this case, the water passage mode is switched by switching the three-way valve and turning the water supply pump on and off.

In this way, by enabling the operation in the circulation water supply mode in addition to the one-pass water supply mode, the hot water tank 60 can be heated cyclically as needed to maintain the hot water storage temperature. In the circulation water flow mode, since the water stored in the hot water tank 60 is caused to flow into the heat recovery heat exchanger 40 through the return line L2, when the temperature of the heat source water W5 is higher than the temperature of the hot water W2 stored in the hot water tank 60, the hot water W2 flowing as the feed water W1 is heated not only by the condenser 12 but also by the heat recovery heat exchanger 40 before. Thus, the heating can be efficiently performed.

Here, the water passage mode switching control unit 130 may perform the water supply control of the hot water tank 60 and the switching control of the water passage mode based on the temperature of the hot water W2 in the hot water tank 60.

Specifically, the water flow mode switching control unit 130 controls the water flow mode switching means so that the one-pass water flow mode is executed and the new water supply to the merging point is stopped when the new water supply is executed to the merging point of the return line L2, and controls the water flow mode switching means so that the circulation water flow mode is executed and the new water supply to the merging point is stopped when the detected temperature of the hot water temperature sensor 61 is lower than a predetermined set temperature, and controls the water flow mode switching means so that the water flow stop mode is executed when the detected temperature of the hot water temperature sensor 61 is higher than the predetermined set temperature.

The water flow mode switching control will be described in detail with reference to a state transition diagram shown in fig. 6A.

The water passage mode switching control unit 130 monitors the water level of the hot water W2 in the hot water tank 60 by the water level detection unit 62 and monitors the temperature of the hot water W2 in the hot water tank 60 by the hot water temperature sensor 61 while each water passage mode is being executed. When the detected position of the electrode rod 622 of the water level detection unit 62 is exceeded and the detected temperature of the hot water temperature sensor 61 is higher than the 1 st set temperature (for example, a temperature 2 to 3 ℃ lower than the target hot water temperature) while the water flow stop mode is being executed, the water flow mode switching control unit 130 continues the water flow stop mode.

< event E1>

When the water level in the hot water tank 60 drops below the detection position of the electrode rod 622 of the water level detection unit 62 during execution of the water supply stop mode, the water supply mode switching control unit 130 drives the water supply pump 21 while maintaining the stop of the return pump 31. Since the supply of the new makeup water W is performed to the merging point of the return line L2 by driving the water supply pump 21, the water passage mode switching control unit 130 drives the heat source supply pump 53 and the compressor 11 to shift to the single water passage mode. In a water passing mode, hot water W2 adjusted to a given target outlet hot water temperature is supplied to the hot water tank 60.

< event E2>

When the water level in the hot water tank 60 rises and exceeds the detection position of the electrode 621 of the water level detection unit 62 during the execution of the one-pass water supply mode, the water supply mode switching control unit 130 stops the water supply pump 21 while maintaining the stop of the return pump 31. Since the supply of the new makeup water W to the merging point of the return line L2 is stopped by stopping the water supply pump 21, the water flow mode switching control unit 130 stops the heat source supply pump 53 and the compressor 11 and shifts to the water flow stop mode. In the water flow stop mode, the supply of the hot water W2 to the hot water tank 60 is stopped.

< event E3>

When the temperature detected by the hot water temperature sensor 61 is lower than the set temperature during execution of the water supply stop mode, the reflux pump 31 is driven while the water supply pump 21 is kept stopped. Since the circulation of the stored water is performed with the supply of the new makeup water W stopped at the merging point of the return line L2 by the drive of the return pump 31, the water flow mode switching control unit 130 drives the heat source supply pump 53 and the compressor 11 to shift to the circulation water flow mode. In the circulation water passing mode, hot water W2 reheated to a given target hot water outlet temperature is supplied to the hot water tank 60.

< event E4>

When the temperature detected by the hot water temperature sensor 61 is higher than the set temperature during the circulation water supply mode, the water supply mode switching control unit 130 stops the reflux pump 31 while maintaining the stop of the water supply pump 21. Then, the heat source supply pump 53 and the compressor 11 are stopped, and the mode shifts to the water flow stop mode. In the water flow stop mode, the circulation of the hot water W2 to the hot water tank 60 is stopped.

< event E5>

When the water level in the hot water tank 60 drops below the detection position of the electrode rod 622 of the water level detection unit 62 during the execution of the circulation/water supply mode, the water supply mode switching control unit 130 stops the reflux pump 31 and drives the water supply pump 21. Since the supply of the new makeup water W is performed to the merging point of the return line L2 by the driving of the water supply pump 21, the water passage mode switching control unit 130 keeps driving the heat source supply pump 53 and the compressor 11 without changing to the single water passage mode. In a water passing mode, hot water W2 adjusted to a given target outlet hot water temperature is supplied to the hot water tank 60.

In the present embodiment, the transition from the first water passage mode to the circulation water passage mode is not performed. This is because, since the mode is shifted to the one-pass mode when the hot water demand is large, the water level is quickly restored by preferentially supplementing the supply of the water W to the hot water tank 60. In addition, since the hot water temperature in the one-pass water mode is higher than the hot water storage temperature of the hot water tank 60, the hot water storage temperature can be increased in a short time.

The set temperature for continuing the determination of the water flow stop mode and the set temperature for making the determination of the transition from the water flow stop mode to the circulation water flow mode may be the same temperature or different temperatures. When the temperature is different, the set temperature of the latter is lower than the set temperature of the former.

In addition, in the above-described control of switching the water passage mode, it is possible to determine whether or not to supply new water such as the makeup water W to the merging point of the return line L2 based on the driving state (the driving command signal or the driving feedback signal) of the water supply pump 21.

Further, a flow rate sensor, not shown, may be disposed upstream of the junction of the water supply line L1 and the return line L2, and the determination may be made based on the detection result of the flow rate sensor.

According to the mode switching control following the state transition diagram of fig. 6A, when the hot water is required sufficiently and the supply of the makeup water W is required, the operation can be performed in the one-pass water flow mode in which the system COP is maximized. When the hot water is required to be small and the supply of the makeup water W is not required, the temperature of the accumulated water can be raised in the circulation water supply mode when the temperature of the accumulated water in the hot water tank 60 decreases. When the hot water is required to be small and the supply of the makeup water W is not necessary, the hot water tank 60 can stand by in the water supply stop mode as long as the temperature of the accumulated water does not substantially decrease.

With the above-described configuration, the hot water W2 having a temperature equal to or higher than the set temperature can be always kept in the hot water tank 60. Further, the circulation water supply mode is executed only when the temperature of the water stored in the hot water tank 60 decreases, and therefore, unnecessary power consumption does not occur due to excessive water circulation.

The preheating mode switching control unit 140 performs preheating mode switching control for switching between the supply water preheating mode and the preheating stop mode. More specifically, the preheating mode switching controller 140 controls the three-way valve 25 as the preheating mode switching means to switch between the supply water preheating mode in which the supply water W1 and the heat source water W5 are simultaneously supplied to the heat recovery heat exchanger 40 and the preheating stop mode in which the supply water W1 is supplied to the bypass line L3.

In the present embodiment, the three-way valve 25 constitutes the preheating mode switching means, but the preheating mode switching means may be constructed in another form. For example, two-way valves may be provided on the upstream side of the water supply line L1 at the junction with the bypass line L3, the bypass line L3, and the preheating mode switching means may be constituted by these two-way valves.

The bypass line is not limited to the bypass of the feed water W1 with respect to the heat recovery heat exchanger 40, and may be the bypass of the heat source water W5 with respect to the heat recovery heat exchanger 40. In this case, in the warm-up stop mode, the heat source water W5 is circulated to the bypass line.

That is, the preheating mode switching means may be provided with 1 or 2 bypass lines for bypassing the feed water W1 with respect to the heat recovery heat exchanger 40 and/or bypassing the heat source water W5 with respect to the heat recovery heat exchanger 40, and may be configured to switch between a feed water preheating mode for causing the feed water W1 and the heat source water W5 to flow to the heat recovery heat exchanger 40 at the same time and a preheating stop mode for causing at least one of the feed water W1 and the heat source water W5 to flow to the bypass line.

This enables the heat recovery heat exchanger 40 to be selectively used according to the situation.

Here, the warm-up mode switching control unit 140 obtains the 1 st detected temperature (heat exchanger inflow front water supply temperature) of the 1 st feed water temperature sensor 24 (heat exchanger inflow front water supply temperature sensor 24) that detects the temperature of the feed water W1 before flowing into the heat recovery heat exchanger 40 and the 2 nd detected temperature (heat exchanger inflow front heat source temperature) of the 1 st heat source temperature sensor 54 (heat exchanger inflow front heat source temperature sensor 54) that detects the temperature of the heat source water W5 before flowing into the heat recovery heat exchanger 40, and can perform the warm-up mode switching control based on the 1 st detected temperature and the 2 nd detected temperature.

Specifically, the preheating mode switching control part 140 compares the 1 st detected temperature of the 1 st water supply temperature sensor 24 with the 2 nd detected temperature of the 1 st heat source temperature sensor 54, controls the preheating mode switching unit so that the water supply preheating mode is performed in the case that the 1 st detected temperature is lower than the 2 nd detected temperature, and controls the preheating mode switching unit so that the preheating stop mode is performed in the case that the 1 st detected temperature is higher than the 2 nd detected temperature.

By such automatic warm-up mode switching according to the feed water temperature and the heat source water temperature, the COP of the system can be maximized.

The preheating mode switching control unit 140 can switch the preheating mode switching means between the respective preheating modes at least when the water flow mode is the circulation water flow mode. In this case, the preheating mode switching control unit 140 may set the preheating mode switching means to the preheating mode when the water passage mode is the water passage through mode, and may set the preheating mode switching means to the preheating stop mode when the water passage stop mode is the water passage through mode.

Thus, for example, in the single pass mode in which the makeup water W having a relatively low temperature is used as the supply water W1, the heat recovery heat exchanger can be actively and effectively used, while in the circulation pass mode in which the stored water in the hot water tank 60 having a relatively high temperature is used as the supply water W1, the heat recovery heat exchanger can be selectively and effectively used in accordance with the relationship between the temperatures of the supply water W1 and the heat source water W5.

In order to perform efficient heating even in the situation of various supply water temperatures and heat source water temperatures, the preheating mode switching control unit 140 may be configured to switch the preheating mode switching means between the preheating modes when the water passage mode is the circulation water passage mode or the once-through water passage mode.

The signal input unit 150 includes a 1 st signal input unit 151 that receives a water flow mode designation signal for designating any one of a one-pass water flow mode, a circulation water flow mode, and a water flow stop mode.

The water passage mode switching control unit 130 controls the water passage mode switching means so as to execute a one-pass water passage mode, a circulation water passage mode, or a water passage stop mode in accordance with the water passage mode designation signal input to the 1 st signal input unit 151. When the circulation water flow mode or the water flow stop mode is executed, the water flow mode switching control unit 130 controls the water supply pump 21 and the like to stop the supply of new water to the junction of the return line L2.

Thus, for example, the operation can be performed in the water passing mode in which the system COP is maximized by using an external signal with makeup water. In addition, the heat preservation of the stored water can be performed in the circulating water supply mode by using an external signal without the supply water.

The signal input unit 150 further includes a 2 nd signal input unit 152 that receives a warm-up mode designation signal designating either the feed water warm-up mode or the warm-up stop mode.

The preheating mode switching control part 140 controls the preheating mode switching unit according to the preheating mode designation signal input to the 2 nd signal input part 152 so that the water supply preheating mode or the preheating stop mode is performed.

Thus, the system COP can be maximized by switching the passive warm-up mode in accordance with the external signal.

The storage unit 160 stores various information necessary for control such as various thresholds.

Next, an example of the flow of control performed by the control unit 100 of the present embodiment will be described.

Fig. 6B is a flowchart showing an example of the flow of the target superheat setting process performed by the target superheat setting unit 111 of the control unit 100.

First, when the system is started, the target superheat setting unit 111 sets the target superheat to a high temperature, for example, 10 ℃.

Next, in step S2, it is determined whether or not the detected temperature of the 2 nd heat source temperature sensor 55 is stable and equal to or lower than a predetermined heat source temperature threshold (for example, 60 ℃). When it is determined that the detected temperature of the 2 nd heat source temperature sensor 55 is stable (Δ T ≦ Δ T0, see fig. 3) and equal to or less than the predetermined heat source temperature threshold value (step S2: yes), the target superheat degree is set to a small value, for example, 5 ℃. On the other hand, when it is determined that the temperature detected by the 2 nd heat-source temperature sensor 55 is unstable or when it is determined that the detected temperature exceeds the predetermined heat-source temperature threshold (NO at step S2), the process returns to step S1 to continue to maintain the target superheat at 10 ℃.

After the target superheat degree is set to 5 ℃ in step S3, it is determined whether the variation in the detected temperature of the 2 nd heat source temperature sensor 55 is large or exceeds a predetermined heat source temperature threshold value or the like in step S4. When it is determined that the variation in the detected temperature of the 2 nd heat-source temperature sensor 55 is large (Δ T > Δ T0, see fig. 3), or when it is determined that the detected temperature exceeds a predetermined heat-source temperature threshold value (yes in step S4), the target superheat degree is increased, for example, set to 10 ℃. On the other hand, when it is determined that the variation in the detected temperature of the 2 nd heat-source temperature sensor 55 is not large and is equal to or smaller than the predetermined heat-source temperature threshold value (no in step S4), the process returns to step S3 to continue to maintain the target superheat at 5 ℃.

Next, the warm-up mode switching control will be described. The water flow mode switching control is performed as described above (see fig. 6A).

Fig. 6C is a flowchart showing an example of the flow of the warm-up mode switching control for switching the feed water warm-up mode and the warm-up stop mode by the warm-up mode switching control unit 140 of the control unit 100. In this example, the warm-up mode switching control unit 140 performs the switching control of the warm-up mode based on the detection results of the 1 st detected temperature (heat exchanger inflow front water supply temperature) of the 1 st feed water temperature sensor 24 (heat exchanger inflow front water supply temperature sensor) and the 2 nd detected temperature (heat exchanger inflow front heat source temperature) of the 1 st heat source temperature sensor 54 (heat exchanger inflow front heat source temperature sensor).

The warm-up mode switching control unit 140 determines in step S11 whether or not the circulation water supply mode is being executed. When the circulation water passing mode is being executed (YES in step S21), in step S12, the detection results of the 1 st detected temperature of the 1 st feed water temperature sensor 24 and the 2 nd detected temperature of the 1 st heat source temperature sensor 54 are compared. And, in case that the 1 st detected temperature is lower than the 2 nd detected temperature (step S12: YES), in step S13, the supplied water preheating mode is executed. On the other hand, in the case where the 1 st detected temperature is not lower than the 2 nd detected temperature (NO in step S12), in step S14, the warm-up stop mode is executed.

In step S11, it is determined whether the one-time water passage mode or the circulation water passage mode is being executed, and when the one-time water passage mode or the circulation water passage mode is being executed, the control may be shifted to step S12.

Fig. 7 is a diagram schematically showing a modification of feed water heating system 1 according to embodiment 1.

The condenser 12 of the heat pump circuit 10 in the present embodiment has functions of condensing and supercooling the refrigerant R. However, as shown in the present modification, the condenser of the heat pump circuit 10 may be divided into a condenser 12A that mainly performs the function of condensing the refrigerant R and a subcooler 12B that mainly performs the function of subcooling the refrigerant R. In this case, the refrigerant R of the heat pump circuit 10 desirably releases latent heat in the condenser 12A and releases sensible heat in the subcooler 12B. That is, the gas refrigerant R is condensed in the condenser 12A to become the liquid refrigerant R, the liquid refrigerant R is supplied to the subcooler 12B, and the liquid refrigerant R is further cooled (subcooled) in the subcooler 12B.

The subcooler 12B is an indirect heat exchanger that exchanges heat between the feed water W1 fed to the condenser 12A and the refrigerant R flowing from the condenser 12A to the expansion valve 13. The subcooler 12B can subcool the refrigerant R from the condenser 12A to the expansion valve 13 using the feed water W1 to the condenser 12A, and can heat the feed water W1 to the condenser 12A using the refrigerant R from the condenser 12A to the expansion valve 13.

By thus separating the heat exchanger according to the condensing and subcooling of the refrigerant R, the heat exchanger can be easily designed, and cost reduction can be achieved. In addition, a general-purpose heat exchanger can be used.

In the present modification, it is preferable that the 2 nd feed water temperature sensor 26 as a feed water temperature sensor for detecting the temperature of the feed water W1 before flowing into the condenser 12 of the heat pump circuit 10 be disposed on the upstream side of the subcooler 12B.

In the case where a certain reduction in the temperature of the hot water W2 in the hot water tank 60 is permitted, such as when the hot water demand site is a steam boiler, a supplementary water line, not shown, may be provided to allow the water to be supplied directly from the supplementary water tank 70 to the hot water tank 60 without passing through the heat recovery heat exchanger 40 and the heat pump circuit 10. In this case, when the level of the hot water W2 in the hot water tank 60 is lower than the detection position of the electrode rod longer than the electrode rod 622, the makeup water W can be directly supplied from the makeup water tank 70 to the hot water tank 60 by driving a makeup water pump provided in a makeup water line.

In the present embodiment, the heat source water W5 is used as the heat source fluid of the heat pump circuit 10, but the heat source fluid is not limited to the heat source water W5, and various fluids such as air and exhaust gas can be used. The heat source fluid is preferably set to be the following fluid: the heat recovery heat exchanger 40 lowers its own temperature while giving heat (sensible heat) to the feed water W1, and the evaporator 14 lowers its own temperature while giving heat (sensible heat) to the refrigerant R of the heat pump circuit 10.

The drive source of the compressor 11 of the heat pump circuit 10 is not limited to the electric motor. For example, the compressor 11 may be driven by a steam motor using steam-induced power, or may be driven by an internal combustion engine. In this case, the output of the compressor 11 can be adjusted by adjusting the amount of steam supplied to the steam motor, the amount of gas supplied to the internal combustion engine, and the like, and the flow rate of the refrigerant can be adjusted.

According to the feed water heating system 1 of embodiment 1 described above, the following effects (1A) to (11A) can be obtained.

(1A) The feed water heating system 1 of the present embodiment includes: a vapor compression heat pump circuit 10 in which a compressor 11, a condenser 12, an expansion valve 13, and an evaporator 14 are annularly connected by a refrigerant circulation line L9, and heat is taken out from the condenser 12 by driving the compressor 11; a heat recovery heat exchanger 40; a heat source fluid line L5 through which a heat source fluid flows in the order of the heat recovery heat exchanger 40 and the evaporator 14; a water supply line L1 through which a water supply W1 flows in the order of the heat recovery heat exchanger 40 and the condenser 12; a refrigerant flow rate adjusting unit that adjusts the refrigerant flow rate by being controlled based on the degree of superheat of the gas refrigerant R flowing into the compressor 11; a feed water flow rate adjusting means for adjusting the feed water flow rate by being controlled based on the hot water temperature of the feed water W1 flowing out from the condenser 12; and a control unit for controlling the refrigerant flow rate adjustment unit and the water supply flow rate adjustment unit.

As described above, by causing the heat source water W5 as the heat source fluid to flow to the heat recovery heat exchanger 40 first, the heat output of the heat recovery heat exchanger 40 is increased, and the amount of warm-up of the feed water W1 is increased. The higher the temperature of the heat source water, the greater the effect of increasing the heat output. Since the heat recovery amount of the heat recovery heat exchanger 40 is increased, the heat recovery amount of the heat pump circuit 10 can be relatively reduced. When the same system heat output as that in the case where the heat source water W5 flows in this order through the evaporator 14 and the heat recovery heat exchanger 40, the output of the compressor 11 can be reduced, and the power consumption of the heat pump circuit 10 can be reduced.

At this time, the temperature of the heat source water W5 flowing into the evaporator 14 is lowered by causing the heat source water W5 to flow first into the heat recovery heat exchanger 40, but in the configuration in which the heat source water W5 flows first into the heat recovery heat exchanger 40 by utilizing the multiple effect of adding further control, that is, the multiple effect of the combination of the adjustment of the refrigerant flow rate based on the degree of superheat and the adjustment of the feed water flow rate based on the hot water temperature, for example, the multiple effect of the further increase of the heat input of the evaporator 14 by the adjustment of the refrigerant flow rate according to the setting of a low degree of superheat and the adjustment of the feed water flow rate according to the setting of a low hot water temperature and the further increase of the heat output of the heat recovery heat exchanger 40 and the increase of the heat output of the evaporator 14, the COP of the system can be greatly improved.

(2A) The heat source fluid line L5 of the feedwater heating system 1 of the present embodiment has the following connection structure: after the heat source fluid and the feed water W1 are heat-exchanged by the counterflow in the heat recovery heat exchanger 40, the heat source fluid and the liquid refrigerant R are heat-exchanged by the counterflow in the evaporator 14.

(3A) The feed water heating system 1 of the present embodiment includes: a suction temperature sensor 17 for detecting a suction temperature of the gas refrigerant R flowing into the compressor 11; a vapor pressure sensor 18 for detecting vapor pressure of the gas refrigerant R flowing out of the evaporator 14; and a hot water outlet temperature sensor 27 for detecting a hot water outlet temperature of the feed water W1 flowing out of the condenser 12, wherein the control unit calculates an evaporation temperature of the liquid refrigerant R based on a detection pressure of the steam pressure sensor 18, calculates a degree of superheat of the gas refrigerant R by subtracting the evaporation temperature from a detection temperature of the suction temperature sensor 17, controls the refrigerant flow rate adjustment unit so that the calculated degree of superheat becomes a target degree of superheat, and controls the feed water flow rate adjustment unit so that the detection temperature of the hot water outlet temperature sensor 27 becomes the target hot water outlet temperature.

By accurately calculating the degree of superheat of the gas refrigerant R in this way and keeping the value constant, the heat output of the condenser 12 to the preheated feed water W1 is stabilized. This reduces the fluctuation of the hot water flow rate. Further, for example, by appropriately increasing the supply water flow rate using the set value of the target hot water temperature and maintaining the flow rate in a fixed range, it is possible to maintain a high heat output.

(4A) The feed water heating system 1 of the present embodiment includes: a heat source temperature sensor that detects the temperature of the heat source fluid before flowing into the evaporator 14, and the control unit sets a target superheat degree in accordance with the detected temperature of the heat source temperature sensor.

In this way, by setting an appropriate target superheat degree in accordance with the temperature of the heat source fluid, it is possible to increase the heat recovery amount in the evaporator 14 while preventing damage to the compressor 11 due to hydraulic compression.

For example, when the temperature of the heat source water is low, the refrigerant circulation flow rate is increased by setting the target superheat degree to be low. This can increase the heat recovery amount even with the low-temperature heat source water W5. By setting the lower limit of the target degree of superheat to, for example, 5 ℃, it is possible to prevent the compressor 11 from being damaged by liquid compression. Further, by setting the upper limit value of the target superheat degree to, for example, 10 ℃, the refrigerant circulation flow rate can be maintained at a predetermined flow rate or more, and a decrease in the heat recovery amount can be prevented.

(5A) The control unit of the feed water heating system 1 according to the present embodiment increases the target superheat degree when it is determined that the variation in the detected temperature of the heat source temperature sensor is large.

Thus, even when a situation in which the temperature of the heat source fluid changes rapidly is confirmed, the heat pump circuit 10 can be stably driven.

For example, even when the temperature of the heat source fluid is rapidly decreased, the target superheat degree can be set to a high value, and the refrigerant can be reliably vaporized in the evaporator 14, so that damage to the compressor 11 due to liquid compression can be prevented.

(6A) The control unit of the feed water heating system 1 according to the present embodiment reduces the target superheat degree when it is determined that the temperature detected by the heat source temperature sensor is stable.

Thus, when the temperature of the heat source fluid is stable, the target superheat degree is set to a low value, and the refrigerant circulation flow rate can be increased, thereby increasing the heat recovery amount in the evaporator 14.

(7A) The feed water heating system 1 of the present embodiment includes: a feed water temperature sensor for detecting the temperature of the feed water before flowing into the condenser 12, and the control unit sets the target hot water temperature in correspondence to the detected temperature of the feed water temperature sensor.

By setting an appropriate target hot water temperature in accordance with the temperature of the supplied water in this manner, it is possible to prevent the occurrence of insufficient supercooling, an excessive supply water flow rate, and the like in the condenser 12.

(8A) The feed water heating system 1 of the present embodiment includes: the target hot water temperature can be set to a value between an upper limit value and a lower limit value by a feed water temperature sensor for detecting the temperature of feed water before flowing into the condenser 12, the lower limit value being a value obtained by adding a predetermined value to the detected temperature of the feed water temperature sensor and being a value which becomes higher as the detected temperature of the feed water temperature sensor becomes higher.

By setting the lower limit of the range of the target hot water outlet temperature that can be set in accordance with the feed water temperature in this way, it is possible to reliably prevent the supercooling shortage in the condenser 12 and stabilize the heat recovery amount in the evaporator 14. Further, the supply water flow rate can be prevented from becoming excessive, thereby suppressing deterioration due to overload of the water supply pump 21.

(9A) The feed water heating system 1 of the present embodiment includes: 1 or 2 bypass lines for bypassing the feed water W1 with respect to the heat recovery heat exchanger 40 and/or bypassing the heat source fluid with respect to the heat recovery heat exchanger 40; and a preheating mode switching unit that switches between a feed water preheating mode in which the feed water W1 and the heat source fluid are simultaneously circulated to the heat recovery heat exchanger 40 and a preheating stop mode in which at least one of the feed water W1 and the heat source fluid is circulated to the bypass line.

Thus, by bypassing the heat recovery heat exchanger 40 under the condition where the efficiency of the heat recovery heat exchanger 40 cannot be exhibited, the pressure loss of the feed water W1 and/or the heat source water W5 can be reduced, and the system COP including the water feed pump 21 and the heat source feed pump 53 can be improved.

(10A) The feed water heating system 1 of the present embodiment includes: a heat exchanger inflow water supply temperature sensor 24 that detects the temperature of the supply water W1 before flowing into the heat recovery heat exchanger 40; and a heat exchanger inflow front heat source temperature sensor 54 that detects a temperature of the heat source fluid before flowing into the heat recovery heat exchanger 40, the control unit compares a 1 st detected temperature of the heat exchanger inflow front water supply temperature sensor 24 with a 2 nd detected temperature of the heat exchanger inflow front heat source temperature sensor 54, controls the warm-up mode switching unit so that the water supply warm-up mode is performed in a case where the 1 st detected temperature is lower than the 2 nd detected temperature, and controls the warm-up mode switching unit so that the warm-up stop mode is performed in a case where the 1 st detected temperature is higher than the 2 nd detected temperature.

(11A) The control unit of the feed water heating system 1 of the present embodiment includes: a signal input unit 150 for receiving a preheating mode designation signal for designating a type of a water supply preheating mode or a preheating stop mode; and a preheating mode switching control part 140 controlling the preheating mode switching unit according to the preheating mode designation signal inputted to the signal input part 150 so that the water supply preheating mode or the preheating stop mode is performed.

By switching the passive warm-up mode in accordance with such an external signal, the system COP can be maximized.

Further, according to the feed water heating system 1 of embodiment 1 described above, the following effects (1B) to (8B) can be obtained.

(1B) The feed water heating system 1 of the present embodiment includes: a vapor compression heat pump circuit 10 in which a compressor 11, a condenser 12, an expansion valve 13, and an evaporator 14 are annularly connected by a refrigerant circulation line L9, and heat is taken out from the condenser 12 by driving the compressor 11; a heat recovery heat exchanger 40; a heat source fluid line L5 for passing a heat source fluid to the heat recovery heat exchanger 40 and the evaporator 14; a water supply line L1 through which a water supply W1 flows in the order of the heat recovery heat exchanger 40 and the condenser 12; a hot water tank 60 for storing the hot water W2 generated in the condenser 12; a return line L2 for returning hot water W2 in the hot water tank 60 to the upstream side of the heat recovery heat exchanger 40; water passage mode switching means for switching a one-pass water passage mode in which the hot water W2 is passed to the condenser 12 without passing through the return line L2, a circulation water passage mode in which the hot water W2 is passed to the return line L2 and the water is passed to the condenser 12, and a water passage stop mode in which the water passage to the condenser 12 is stopped; and a control unit for controlling the water-passing mode switching unit.

In this way, by enabling the operation in the circulation water supply mode in addition to the one-pass water supply mode, the hot water tank 60 can be heated cyclically as needed to maintain the hot water storage temperature. In the circulation water supply mode, since the stored water flows into the heat recovery heat exchanger 40 immediately before, efficient heating can be performed when the stored water temperature is less than the heat source water temperature.

(2B) The feed water heating system 1 of the present embodiment includes: 1 or 2 bypass lines for bypassing the feed water W1 with respect to the heat recovery heat exchanger 40 and/or bypassing the heat source fluid with respect to the heat recovery heat exchanger 40; and a preheating mode switching unit that switches between a feed water preheating mode in which the feed water W1 and the heat source fluid are simultaneously circulated to the heat recovery heat exchanger 40 and a preheating stop mode in which at least one of the feed water W1 and the heat source fluid is circulated to the bypass line.

(3B) The control means of the feed water heating system 1 of the present embodiment can switch the preheating mode switching means to the feed water preheating mode and the preheating stop mode at least in the circulation water passing mode.

Thus, for example, the heat recovery heat exchanger 40 can be actively and effectively used in the once-through water flow mode, and the heat recovery heat exchanger 40 can be selectively and effectively used in the circulation water flow mode.

(4B) The heat source fluid line L5 of the feedwater heating system 1 of the present embodiment is a connection structure that allows the heat source fluid to flow through the heat recovery heat exchanger 40 and the evaporator 14 in this order.

Thus, the heat source water W5 as the heat source fluid is first caused to flow into the heat recovery heat exchanger 40, whereby the amount of preheating of the feed water W1 can be increased, and the heat output of the heat recovery heat exchanger 40 can be improved. The higher the temperature of the heat source water, the greater the effect of increasing the heat output.

(5B) The feed water heating system 1 of the present embodiment includes: and a hot water temperature sensor 61 for detecting the temperature of the hot water W2 in the hot water tank 60, wherein the control means controls the water passage mode switching means so that the one-pass water passage mode is executed when new water supply is executed to the junction of the return line L2, controls the water passage mode switching means so that the circulation water passage mode is executed when new water supply to the junction is stopped and the detected temperature of the hot water temperature sensor 61 is lower than a set temperature, and controls the water passage mode switching means so that the water passage stop mode is executed when new water supply to the junction is stopped and the detected temperature of the hot water temperature sensor 61 is higher than the set temperature.

Thus, when the hot water is required to be sufficient and the supply of the makeup water W is required, the operation can be performed in the first water passing mode in which the system COP is maximized. When the hot water is required to be small and the supply of the makeup water W is not required, the temperature of the accumulated water can be raised in the circulation water supply mode when the temperature of the accumulated water in the hot water tank 60 decreases.

(6B) The feed water heating system 1 of the present embodiment includes: a heat exchanger inflow water supply temperature sensor 24 that detects the temperature of the supply water W1 before flowing into the heat recovery heat exchanger 40; and a heat exchanger inflow front heat source temperature sensor 54 that detects a temperature of the heat source fluid before flowing into the heat recovery heat exchanger 40, the control unit compares a 1 st detected temperature of the heat exchanger inflow front water supply temperature sensor 24 with a 2 nd detected temperature of the heat exchanger inflow front heat source temperature sensor 54, controls the warm-up mode switching unit so that the water supply warm-up mode is performed in a case where the 1 st detected temperature is lower than the 2 nd detected temperature, and controls the warm-up mode switching unit so that the warm-up stop mode is performed in a case where the 1 st detected temperature is higher than the 2 nd detected temperature.

(7B) The control unit of the feed water heating system 1 of the present embodiment includes: a 1 st signal input unit 151 that receives a water flow mode designation signal for designating any one of a water flow through mode, a circulation water flow through mode, and a water flow stop mode; and a water passage mode switching control unit 130 for controlling the water passage mode switching means so as to execute a one-pass water passage mode, a circulation water passage mode, or a water passage stop mode in accordance with the water passage mode designation signal input to the 1 st signal input unit 151, wherein the water passage mode switching control unit 130 stops new water supply to a merging portion of the return line L2 when the circulation water passage mode or the water passage stop mode is executed.

Thus, for example, the operation can be performed in the one-pass mode in which the system COP is maximum, using an external signal to which the supply of makeup water is applied. In addition, the heat of the stored water can be maintained in the circulation mode by an external signal without the supply of the makeup water.

(8B) The control unit of the feed water heating system 1 of the present embodiment includes: the 2 nd signal input unit 152 receives a warm-up mode designation signal for designating either of the feed water warm-up mode and the warm-up stop mode: and a preheating mode switching control part 140 for controlling the preheating mode switching unit so that the water supply preheating mode or the preheating stop mode is performed according to the preheating mode designation signal inputted to the 2 nd signal input part 152.

This also enables, for example, passive warm-up mode switching in accordance with an external signal, thereby maximizing the system COP.

Further, according to the feed water heating system 1 of embodiment 1 described above, the following effects (1C) to (7C) can be obtained.

(1C) The feed water heating system 1 of the present embodiment includes: a vapor compression heat pump circuit 10 in which a compressor 11, a condenser 12, an expansion valve 13, and an evaporator 14 are annularly connected by a refrigerant circulation line L9, and heat is taken out from the condenser 12 by driving the compressor 11; a refrigerant flow rate adjusting unit that adjusts a flow rate of the refrigerant R flowing through the heat pump circuit 10; a heat source temperature sensor for detecting a temperature of a heat source fluid that exchanges heat with the refrigerant R in the evaporator 14; and a control unit for controlling the refrigerant flow rate adjustment unit, wherein the control unit sets a target superheat degree corresponding to the detection temperature of the heat source temperature sensor, and controls the refrigerant flow rate adjustment unit so that the superheat degree of the refrigerant R flowing into the compressor 11 becomes the target superheat degree.

By setting an appropriate target superheat degree in accordance with the temperature of the heat source fluid in this way, it is possible to increase the heat recovery amount in the evaporator 14 while preventing damage to the compressor 11 due to hydraulic compression.

For example, when the temperature of the heat source water is low, the refrigerant circulation flow rate is increased by setting the target superheat degree to be low. This increases the amount of heat recovery even with the low-temperature heat source fluid, i.e., the heat source water W5. By setting the lower limit of the target degree of superheat to, for example, 5 ℃, it is possible to prevent the compressor 11 from being damaged by liquid compression. Further, by setting the upper limit value of the target superheat degree to, for example, 10 ℃, the refrigerant circulation flow rate can be maintained at a predetermined flow rate or more, and a decrease in the heat recovery amount can be prevented.

(2C) The control unit of the feed water heating system 1 according to the present embodiment increases the target superheat degree when it is determined that the variation in the detected temperature of the heat source temperature sensor is large.

As a result, the heat pump circuit 10 can be stably driven even when a situation in which a sudden change in the temperature of the heat source fluid is observed.

(3C) The control unit of the feed water heating system 1 according to the present embodiment reduces the target superheat degree when it is determined that the temperature detected by the heat source temperature sensor is stable.

Thus, when the temperature of the heat source fluid is stable, the target superheat degree is set to a low value, whereby the refrigerant circulation flow rate can be increased, and the heat recovery amount in the evaporator 14 can be increased.

(4C) The feed water heating system 1 of the present embodiment includes: a suction temperature sensor 17 for detecting a suction temperature of the gas refrigerant R flowing into the compressor 11; and a vapor pressure sensor 18 for detecting vapor pressure of the gas refrigerant R flowing out of the evaporator 14, the control unit calculates an evaporation temperature of the liquid refrigerant R from the detection pressure of the vapor pressure sensor 18, calculates a degree of superheat of the gas refrigerant R by subtracting the evaporation temperature from the detection temperature of the suction temperature sensor 17, and controls the refrigerant flow rate adjusting unit so that the calculated degree of superheat becomes a target degree of superheat

By accurately calculating the degree of superheat of the gas refrigerant R in this way and keeping the value constant, the heat output of the condenser 12 to the preheated feed water W1 is stabilized. This reduces the fluctuation of the hot water flow rate.

(5C) The feed water heating system 1 of the present embodiment includes: a supply water flow rate adjusting unit that adjusts a supply water flow rate flowing through the condenser 12; and a hot water outlet temperature sensor 27 that detects the hot water outlet temperature of the supply water W1 flowing out of the condenser 12, and the control unit controls the supply water flow rate adjustment unit so that the temperature detected by the hot water outlet temperature sensor 27 becomes the target hot water outlet temperature.

This allows the feed water W1 to be heated to a desired temperature at all times to discharge hot water.

(6C) The feed water heating system 1 of the present embodiment includes: a feed water temperature sensor that detects the temperature of the feed water W1 before flowing into the condenser 12, and the control unit sets the target hot water temperature in correspondence with the detected temperature of the feed water temperature sensor.

By setting an appropriate target hot water outlet temperature in accordance with the temperature of the feed water W1 in this way, it is possible to prevent the occurrence of an overcooling deficiency in the condenser 12, an excessive feed water flow rate, and the like.

(7C) The feed water heating system 1 of the present embodiment includes: the feed water temperature sensor that detects the temperature of the feed water W1 before flowing into the condenser 12 can set the target hot water temperature to a value between an upper limit value and a lower limit value, the lower limit value being a value obtained by adding a given value to the detected temperature of the feed water temperature sensor and being a value that is higher as the detected temperature of the feed water temperature sensor is higher.

By setting the lower limit of the range of the target hot water outlet temperature that can be set in accordance with the feed water temperature in this way, it is possible to reliably prevent the supercooling shortage in the condenser 12 and stabilize the heat recovery amount in the evaporator 14. Further, the feed water flow rate can be prevented from being excessive, thereby suppressing deterioration due to overload of the feed water pump 21.

Although the preferred embodiments of the feed water heating system according to the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be modified as appropriate.

Claims

1. A feed water heating system is provided with:

a vapor compression heat pump circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in an annular manner by a refrigerant circulation line, and heat is taken out of the condenser by driving of the compressor;

a heat exchanger for heat recovery;

a heat source fluid line through which a heat source fluid flows in the order of the heat recovery heat exchanger and the evaporator;

a water supply line for circulating water in the heat recovery heat exchanger and the condenser in this order;

a refrigerant flow rate adjusting unit which is controlled based on the superheat degree of the gas refrigerant flowing into the compressor and adjusts the refrigerant flow rate;

a supply water flow rate adjusting unit which is controlled based on the temperature of the hot water flowing out from the condenser and adjusts the supply water flow rate; and

and the control unit is used for controlling the refrigerant flow adjusting unit and the water supply flow adjusting unit.

2. The water supply heating system according to claim 1,

the heat source fluid line is connected with the following structure: the heat recovery heat exchanger exchanges heat between the heat source fluid and the water supply by means of the reverse flow, and then exchanges heat between the heat source fluid and the liquid refrigerant by means of the reverse flow in the evaporator.

3. The supplied water heating system according to claim 1 or 2,

the feed water heating system is provided with:

a suction temperature sensor for detecting a suction temperature of a gas refrigerant flowing into the compressor;

a vapor pressure sensor for detecting vapor pressure of the gas refrigerant flowing out of the evaporator; and

a hot water outlet temperature sensor for detecting a hot water outlet temperature of the supply water flowing out from the condenser,

the control unit obtains an evaporation temperature of a liquid refrigerant according to a detection pressure of the steam pressure sensor, calculates a superheat degree of a gas refrigerant by subtracting the evaporation temperature from a detection temperature of the suction temperature sensor, controls the refrigerant flow rate adjustment unit so that the calculated superheat degree becomes a target superheat degree, and controls the supply water flow rate adjustment unit so that a detection temperature of the hot water temperature sensor becomes a target hot water temperature.

4. The water supply heating system according to claim 3,

the feed water heating system is provided with:

a heat source temperature sensor which detects a temperature of the heat source fluid before flowing into the evaporator,

the control unit sets the target superheat degree in correspondence to the detected temperature of the heat source temperature sensor.

5. The water supply heating system according to claim 4,

the control means increases the target superheat degree when it is determined that the variation in the detected temperature of the heat source temperature sensor is large.

6. The water supply heating system according to claim 4,

the control unit reduces the target superheat degree when it is determined that the detected temperature of the heat source temperature sensor is stable.

7. The water supply heating system according to claim 3,

the feed water heating system is provided with:

a feed water temperature sensor for detecting a temperature of feed water before flowing into the condenser,

the control unit sets the target hot water outlet temperature corresponding to a detected temperature of the supply water temperature sensor.

8. The water supply heating system according to claim 3,

the feed water heating system is provided with:

the target hot water temperature may be set to a value between an upper limit value and a lower limit value, the lower limit value being a value obtained by adding a given value to the detected temperature of the feed water temperature sensor and being a value that is higher as the detected temperature of the feed water temperature sensor is higher.

9. The supplied water heating system according to claim 1 or 2,

the feed water heating system is provided with:

1 or 2 bypass lines for bypassing the water supply with respect to the heat recovery heat exchanger and/or bypassing the heat source fluid with respect to the heat recovery heat exchanger; and

and a preheating mode switching unit that switches between a supply water preheating mode in which supply water and a heat source fluid are simultaneously circulated to the heat recovery heat exchanger and a preheating stop mode in which at least one of the supply water and the heat source fluid is circulated to the bypass line.

10. The water supply heating system according to claim 9,

the feed water heating system is provided with:

a heat exchanger pre-inflow water supply temperature sensor that detects a temperature of the water supply before flowing into the heat recovery heat exchanger; and

a heat exchanger inflow front heat source temperature sensor for detecting the temperature of the heat source fluid before flowing into the heat recovery heat exchanger,

the control unit compares a 1 st detected temperature of the heat exchanger pre-inflow water supply temperature sensor with a 2 nd detected temperature of the heat exchanger pre-inflow heat source temperature sensor, controls the preheating mode switching unit so that the water supply preheating mode is performed in a case where the 1 st detected temperature is lower than the 2 nd detected temperature, and controls the preheating mode switching unit so that the preheating stop mode is performed in a case where the 1 st detected temperature is higher than the 2 nd detected temperature.

11. The water supply heating system according to claim 9,

the control unit has:

a signal input unit that receives a warm-up mode designation signal for designating a type of the supply water warm-up mode or the warm-up stop mode; and

a preheating mode switching control part which controls the preheating mode switching unit according to the preheating mode designation signal inputted to the signal input part so that the water supply preheating mode or the preheating stop mode is executed.