JP6069910B2 - Heat pump system - Google Patents

Description

    The present invention relates to a heat pump system, and more particularly to a device including an auxiliary heating unit.

    2. Description of the Related Art Conventionally, a first heat exchanger and a second heat exchanger are connected to each other, and a heat medium circuit in which a heat medium circulates is provided. A heat pump system in which the heat medium radiates heat to a target fluid in the second heat exchanger is known. Some of these heat pump systems include a heater for heating the heat medium of the heat medium circuit, as disclosed in Patent Document 1.

    The heater is connected between the first heat exchanger and the second heat exchanger of the heat medium circuit. Thereby, the heat medium heated by the first heat exchanger can be further heated by the heater, and the heat radiation amount from the heat medium to the target fluid in the second heat exchanger can be increased. For example, by operating the heater together with the refrigerant circuit during the initial operation of the heat pump system, the temperature of the target fluid can be brought closer to the target temperature more quickly than when the heater is not used.

JP 2004-132612 A

    However, if the heating amount of the auxiliary heating unit constituting the heater is excessive, the temperature of the heat medium may exceed the temperature of the refrigerant in the first heat exchanger. Since the heat cannot be released, the refrigerant circuit does not operate. In order to avoid such a situation, it is necessary to forcibly reduce the heating amount of the auxiliary heating unit, and there is a problem that the temperature of the target fluid cannot be quickly brought close to the target temperature.

    The present invention has been made in view of this point, and an object of the present invention is to quickly bring the temperature of the target fluid close to the target temperature by operating the auxiliary heating unit while continuing the operation of the refrigeration cycle of the refrigerant circuit. .

    According to a first aspect of the present invention, there is provided a refrigerant circuit (50) of a vapor compression refrigeration cycle to which a primary flow path (12a) of a first heat exchanger (12) functioning as a radiator is connected, and the first heat exchange. The secondary side flow path (12b) of the heat exchanger (12) and the second heat exchanger (22) are connected and between the first heat exchanger (12) and the second heat exchanger (22). A heat medium circuit (20) in which a heat medium circulates and the heat medium heats a target fluid in the second heat exchanger (22), and the first heat exchanger (12) includes the heat medium circuit A heat pump system that heats the heat medium of (20) to 100 ° C. or higher by the refrigerant of the refrigerant circuit (50).

    And this heat pump system sets the threshold value smaller than the target value of the auxiliary | assistant heating part (1) which heats the said target fluid, and the said target fluid temperature, and when the temperature of the said target fluid is smaller than the said threshold value An operation control unit (40) that performs a first operation that permits the operation of the auxiliary heating unit (1) and prohibits the operation of the auxiliary heating unit (1) when the temperature of the target fluid is equal to or higher than the threshold value; I have.

Further, the operation control unit (40) stores an arrival time (t1) from the prohibition of the operation of the auxiliary heating unit (1) until the temperature of the target fluid reaches a target value. When (t1) is longer than the target arrival time (t0), the threshold value is brought close to the target value of the temperature of the target fluid, and when the arrival time (t1) is shorter than the target arrival time (t0), the threshold value is set. A third operation of moving away from the target temperature of the target fluid is performed.

    In the first invention, the target fluid is heated by both the auxiliary heating unit (1) and the heat medium circuit (20). Unlike the prior art, the heat of the auxiliary heating unit (1) is directly released to the target fluid without passing through the heat medium of the heat medium circuit (20).

    When the target fluid is heated toward a predetermined target value, the refrigerant circuit (50) and the auxiliary heating unit (1) operate until the temperature of the target fluid reaches a threshold value. Thereafter, when the temperature of the target fluid reaches a threshold value, only the auxiliary heating unit (1) stops. When the auxiliary heating unit (1) stops, only the refrigerant circuit (50) is operated, so that the amount of heating from the heat medium to the target fluid is reduced, and the temperature rise of the target fluid is moderated. Temperature approaches the target value.

Further, when the arrival time (t1) is longer than the target arrival time (t0), the threshold value is increased, and the stop of the auxiliary heating unit (1) is delayed later than the previous time. On the other hand, when the arrival time (t1) is shorter than the target arrival time (t0), the threshold value becomes small, and the auxiliary heating unit (1) stops earlier than the previous time.

The second invention according to the first invention, the operation control unit (40), when you allow the operation of the auxiliary heating unit (1), so that the temperature of the target fluid approaches the threshold A second operation for adjusting the heating capacity of the auxiliary heating unit (1) is performed.

In the second invention, as the temperature of the target fluid approaches the threshold, the heating capacity of the auxiliary heating unit (1) gradually decreases, and when the temperature of the target fluid reaches the threshold, the auxiliary heating unit ( 1) stops. Here, since the heating capacity of the auxiliary heating unit (1) when the auxiliary heating unit (1) is stopped is lower than when the heating capacity is not reduced by the operation control unit (40), the auxiliary heating is performed. The residual heat of the part (1) is small, and the temperature of the target fluid approaches the target value without overshooting .

    According to the present invention, since the target fluid is directly heated by the auxiliary heating unit (1), unlike the conventional case, in the first heat exchanger (12), the first heat exchanger (12) 12) There is no problem that the temperature of the heat medium flowing into the refrigerant exceeds the temperature of the refrigerant. Therefore, it is possible to operate the auxiliary heating unit (1) while continuing the operation of the refrigerant circuit (50), and the temperature of the target fluid can be quickly brought close to the target temperature.

    When the temperature difference between the target fluid and the target value becomes small, the auxiliary heating unit (1) is stopped and only the refrigerant circuit (50) and the heat medium circuit (20) are operated. Thus, by stopping the auxiliary heating unit (1) before the temperature of the target fluid reaches the target value, overshoot of the temperature of the target fluid can be suppressed.

Furthermore, every time the auxiliary heating unit (1) is activated, the previous arrival time (t1) is memorized, and the arrival time (t1) is compared with the target arrival time (t0) to obtain the target temperature (Tobj). Since the allowable error (Terr) is changed, the arrival time (t1) can be made closer to the target arrival time (t0).

Further, according to the second invention, as the temperature of the target fluid approaches the threshold value, the operation control unit (40) gradually decreases the heating capacity of the auxiliary heating unit (1). The heating capacity of the auxiliary heating unit (1) when the auxiliary heating unit (1) is stopped can be kept lower than when the heating capacity is not reduced by the operation control unit (40). Thereby, the residual heat at the time of the stop of the auxiliary heating unit (1) is reduced, and the temperature of the target fluid can be brought close to the target value without further overshooting .

It is a refrigerant circuit figure of the heat pump system concerning this embodiment. It is a control flowchart of the rapid heating control which the controller of a heat pump system performs. It is a control flow figure of the controller of the heat pump system of other embodiments. It is a graph which shows the relationship between the operation time of a heat pump system, and the water temperature of a thermostat.

    Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

    The heat pump system (10) of this embodiment is used for industrial purposes, and heats the heat medium to 100 ° C. or higher. As shown in FIG. 1, the heat pump system (10) includes a refrigerant circuit (50), a heat medium circuit (20), a controller (operation control unit) (40), and a heater (auxiliary heating unit) (1). Yes.

    The refrigerant circuit (50) performs a two-stage compression refrigeration cycle by circulating the refrigerant. The refrigerant circuit (50) includes a low-stage compressor (11a) and a high-stage compressor (11b), a radiator (first heat exchanger) (12), an expansion valve (13), an evaporator ( 14) are connected in order by refrigerant piping. In the present embodiment, R245fa is used as the refrigerant.

    Although not shown, the low-stage compressor (11a) and the high-stage compressor (11b) are configured as a completely sealed type, and the inside of the casing that houses the compression section and the motor that rotationally drives the compression section is the suction pressure. It has a so-called low-pressure dome shape. That is, in each compressor (11a, 11b), the suction refrigerant flows into the casing, and the refrigerant compressed by the compression unit is directly discharged out of the casing without flowing out into the casing. Each compressor (11a, 11b) is configured to have a variable operating rotational speed. Both compressors (11a, 11b) are connected in series to compress the refrigerant in two stages, and constitute a refrigerant compression mechanism.

    The radiator (12) has a refrigerant channel (primary side channel) (12a) and a heat medium channel (secondary side channel) (12b). The refrigerant flow path (12a) has an inflow end connected to the discharge side of the high stage compressor (11b) and an outflow end connected to a subcooling heat exchanger (15) described later.

    The expansion valve (13) is an electronic expansion valve whose opening degree can be adjusted.

    The evaporator (14) has a cold water channel (14a) and a refrigerant channel (14b). The refrigerant flow path (14b) has an inflow end connected to the expansion valve (13) and an outflow end connected to the suction side of the low-stage compressor (11a). On the other hand, the cold water flow path (14a) of the evaporator (14) is connected to the cold water circuit (30). In the evaporator (14), the water in the cold water circuit (30) flowing through the cold water flow path (14a) exchanges heat with the refrigerant flowing through the refrigerant flow path (14b) to cool the water.

    The refrigerant circuit (50) is provided with a supercooling heat exchanger (15) and an injection passage (19). The supercooling heat exchanger (15) is connected between the radiator (12) and the expansion valve (13), and has a high temperature channel (15b) and a low temperature channel (15a). The injection passage (19) has an inflow end connected between the radiator (12) and the supercooling heat exchanger (15), and an outflow end connected to the low stage compressor (11a) and the high stage compressor (11b). ) Is connected between. A flow rate adjusting valve (16) is provided in the injection passage (19). The flow rate adjusting valve (16) also has an action of depressurizing the refrigerant passing therethrough.

    The high temperature channel (15b) of the supercooling heat exchanger (15) has an inflow end connected to the radiator (12) and an outflow end connected to the expansion valve (13). The low-temperature flow path (15a) of the supercooling heat exchanger (15) is connected to the downstream side of the flow rate adjustment valve (16) in the injection path (19). In the supercooling heat exchanger (15), the outlet refrigerant of the radiator (12) flowing through the high-temperature channel (15b) and the branch refrigerant of the outlet refrigerant flowing through the low-temperature channel (15a) exchange heat, and the high-temperature channel While the outlet refrigerant of (15b) is supercooled, the branch refrigerant of the low temperature channel (15a) evaporates. The injection passage (19) is an intermediate pressure refrigerant between the low-stage compressor (11a) and the high-stage compressor (11b), that is, a compression mechanism. The refrigerant is joined with the refrigerant in the middle of compression.

    The heat medium circuit (20) is a closed circuit in which the pump (21), the heating heat exchanger (second heat exchanger) (22), and the heat medium flow path (12b) of the radiator (12) are connected in order. It is configured. A heat medium (for example, water or oil) is enclosed in the heat medium circuit (20). A heat medium circulates in the heat medium circuit (20) by the pump (21). In the radiator (12), the high-pressure refrigerant in the refrigerant circuit (50) flowing through the refrigerant flow path (12a) and the heat medium in the heat medium circuit (20) flowing through the heat medium flow path (12b) exchange heat, and the heat medium Is heated. The heating heat exchanger (22) is provided in a constant temperature bath (23) for storing hot water. This hot water is the target fluid of the present invention. In addition, this target fluid is not limited to water, For example, oil and air may be sufficient.

    In this heating heat exchanger (22), the heat medium heated by the radiator (12) exchanges heat with water in the thermostat (23), and the water in the thermostat (23) is heated to a constant temperature. . Further, a water temperature sensor (43) for detecting the water temperature of the constant temperature bath (23) is provided in the constant temperature bath (23). The detection value of the water temperature sensor (43) is input to the controller (40).

    The heater (1) is composed of, for example, a sheathed heater. The heater (1) is disposed in the thermostat (23) and heats the water in the thermostat (23).

    The controller (40) controls operations of the refrigerant circuit (50), the heat medium circuit (20), and the heater (1). One of the control operations of the controller (40) is rapid heating control. This rapid heating control is a control for efficiently heating the water temperature (To) of the thermostat (23) to the target temperature (Tobj) in a short time. This operation is the first operation of the operation control unit (40) of the present invention.

    The controller (40) includes a first target setting unit (45), a second target setting unit (48), a threshold setting unit (46), a control unit (47), and an adjustment unit (49) for performing this rapid heating control. It has.

    A 1st target setting part (45) sets the target temperature (Tobj) of the water of a thermostat (23). The target temperature (Tobj) is input by the user to the first target setting unit (45). The second target setting unit (48) sets an allowable error (Terr) of the target temperature (Tobj). The allowable error (Terr) is input to the second target setting unit (48) by the user. The threshold setting unit (46) sets a value obtained by subtracting the allowable error (Terr) of the second target setting unit (48) from the target temperature (Tobj) of the first target setting unit (45) as the threshold (Tobj-Terr). To do. The control unit (47) compares the water temperature (To) of the water temperature sensor (43) with the threshold value (Tobj-Terr) of the threshold setting unit (46) and performs ON / OFF control of the heater (1). The adjustment unit (49) changes the allowable error (Terr) set by the second target setting unit (48) by a so-called learning function.

-Driving action-
<Operation of refrigerant circuit and heat medium circuit>
When both compressors (11a, 11b) are driven, the refrigerant compressed by the low-stage compressor (11a) is further compressed by the high-stage compressor (11b) to become a high-pressure refrigerant. The high-pressure refrigerant discharged from the high-stage compressor (11b) is condensed by exchanging heat with the heat medium of the heat medium circuit (20) in the radiator (12), and the heat medium is 100 ° C. or higher (for example, 120 ° C. ). A part of the high-pressure refrigerant condensed in the radiator (12) flows into the injection passage (19), and the rest flows into the high-temperature channel (15b) of the supercooling heat exchanger (15). The high-pressure refrigerant that has flowed into the injection passage (19) is depressurized by the flow control valve (16), and then flows into the low-temperature flow path (15a) of the supercooling heat exchanger (15), and the high-pressure refrigerant in the high-temperature flow path (15b). Exchange heat with refrigerant. As a result, the high-pressure refrigerant in the high-temperature channel (15b) is supercooled, while the refrigerant in the low-temperature channel (15a) evaporates to become a superheated gas refrigerant having intermediate pressure. The high-pressure refrigerant in the high-temperature channel (15b) decreases the enthalpy of the refrigerant by being supercooled.

    The high-pressure refrigerant supercooled by the supercooling heat exchanger (15) is decompressed by the expansion valve (13) to become a low-pressure refrigerant. The low-pressure refrigerant flows into the evaporator (14), exchanges heat with the heat source water of the cold water circuit (30) and evaporates, and the heat source water is cooled to become cold water. Since the enthalpy of the low-pressure refrigerant flowing through the evaporator (14) is reduced by the amount of supercooling as described above, the evaporation capacity (cooling capacity) of the evaporator (14) increases. The refrigerant flowing out of the evaporator (14) is sucked into the low stage compressor (11a) and compressed again. The refrigerant discharged from the low-stage compressor (11a) joins the intermediate-pressure superheated gas refrigerant from the injection passage (19) and is sucked into the high-stage compressor (11b).

    In the heat medium circuit (20), the heat medium heated by the radiator (12) flows into the heating heat exchanger (22) and exchanges heat with the water in the thermostat (23), and the water is heated to become hot water. .

<Controller rapid heating control>
This rapid heating control is mainly performed when the water in the thermostatic bath (23) is heated from room temperature, or when the water in the thermostatic bath (23) falls rapidly and cannot be handled by the capacity control of the heat pump. . This rapid heating control will be described based on the control flow chart of FIG.

    First, in step ST1, it is determined whether or not the heater (1) is turned on. This determination is made based on the water temperature of the thermostatic chamber (23). If the heater (1) is not turned on, the process proceeds to step ST2. Then, the processing from step ST1 to step ST2 is repeated until it is determined that the heater (1) is turned on. On the other hand, if it is determined in step ST1 that the heater (1) is turned on, the process proceeds to step ST3. The process of step ST3 is performed by the control unit (47) of the controller (40).

    In step ST3, the current water temperature (To) is compared with a threshold value (Tobj-Terr). If the current water temperature (To) is lower than the threshold value (Tobj-Terr), the process proceeds to step ST4. On the other hand, if the current water temperature (To) is equal to or higher than the threshold value (Tobj-Terr), the process returns to step ST2, and the heater (1) is turned off. The heater (1) is turned off while the current water temperature (To) is continuously higher than the threshold value (Tobj-Terr).

    In step ST4, a process for keeping the heater (1) ON is performed. Then, it returns to step ST1 and the process from step 1 to step 4 is repeated.

    As shown in FIG. 4, the refrigerant circuit (50) and the heater (1) operate until the water temperature (To) of the thermostatic bath (23) reaches a threshold value (Tobj-Terr) (see FIG. 4). B section). In addition, the first B section of FIG. 4 is a section which heats the water of a thermostat (23) from normal temperature, and when the next B section falls rapidly, of the thermostat (23) This is the section where water is heated.

    Thereafter, when the temperature of the target fluid reaches a threshold value, only the heater (1) stops (section A in FIG. 4). When the heater (1) is stopped, only the refrigerant circuit (50) is operated. Therefore, the amount of heating from the heat medium to the hot water in the constant temperature bath (23) is reduced, and the water temperature (To) of the constant temperature bath (23) is reduced. ) Approaches the target temperature (Tobj) while the rise is slow.

<Control of learning function of controller>
Next, learning function control performed by the adjustment unit (49) of the controller (40) will be described. This learning function control is the second operation of the operation control unit (40) of the present invention.

    The adjustment unit (49) stores the previous arrival time (t1) from when the heater (1) is stopped until the water temperature (To) of the thermostatic chamber (23) reaches the target temperature (Tobj). The adjustment unit (49) has a target arrival time (t0) set in advance. Then, an allowable error (Terr) is calculated by the following equation (1). Note that Terr (n-1) is the previous allowable error.

Terr (n) = (1+ (t0 / t1)) × (Terr (n−1) / 2) (1)
Here, if the previous arrival time (t1) is twice the target arrival time (t0), the allowable error (Terr) can be increased by 0.5 times. Considering the disturbance, the allowable error (Terr) is increased by 0.75 times. If the allowable error (Terr) decreases, the threshold value (Tobj-Terr) increases, and the stop of the heater (1) is delayed compared to the previous time. If the previous arrival time (t1) is 0.5 times the target arrival time (t0), the error (Terr) may be doubled to prevent overshoot. In Expression (1), the allowable error (Terr) is 1.5 times in consideration of disturbance. If the allowable error (Terr) increases, the threshold value (Tobj-Terr) decreases, and the heater (1) stops earlier than the previous time.

    The adjustment unit (49) of the controller (40) stores the previous arrival time (t1) each time the heater (1) is started, and changes the allowable error (Terr) based on the equation (1). Thereby, the arrival time (t1) approaches the target arrival time (t0). If the arrival time (t1) matches the target arrival time (t0), the allowable error (Terr) is not changed.

-Effect of the embodiment-
According to the present embodiment, since the target fluid is directly heated by the heater (1), unlike the conventional case, in the radiator (12) of the refrigerant circuit (50), the radiator (12) 12) There is no problem that the temperature of the heat medium flowing into the refrigerant exceeds the temperature of the refrigerant. Therefore, it is possible to operate the heater (1) while continuing the operation of the refrigerant circuit (50), and the water temperature (To) of the thermostatic chamber (23) can be quickly brought close to the target temperature (Tobj).

    When the temperature difference between the water temperature (To) and the target temperature (Tobj) in the thermostatic chamber (23) becomes small, the heater (1) is stopped and only the refrigerant circuit (50) and the heat medium circuit (20) To work. Thus, by stopping the heater (1) before the temperature of the target fluid reaches the target value, it is possible to suppress the overshoot of the water temperature (To) of the thermostat (23). In addition, comparing the heating efficiency of the heater (1) and the refrigerant circuit (50), the refrigerant circuit (50) has higher heating efficiency, so the operation efficiency of the heat pump system can be improved by operating only the refrigerant circuit (50). Can be increased.

<< Other Embodiments >>
About the said embodiment, it is good also as following structures.

    In the embodiment, the heater (1) is stopped when the water temperature (To) of the thermostatic chamber (23) becomes equal to or higher than the threshold value (Tobj-Terr). However, as shown in the control flow diagram of FIG. The heating capacity of the heater (1) may be adjusted by PI control or PID control as the input voltage value so that To) approaches the threshold value (Tobj-Terr). The control flow diagram of FIG. 3 will be described. The processing from step ST5 to step ST7 in FIG. 3 is the same as the processing from step ST1 to step ST3 in FIG.

    In step ST8 of FIG. 3, the change value (α) of the heater (1) is calculated so that the subtraction value of the threshold value (Tobj-Terr) becomes zero from the current water temperature (To). In step ST9, a value obtained by adding the change value (α) to the input voltage value of the heater (1) is input to the heater (1).

    As a result, as the water temperature (To) of the thermostat (23) approaches the threshold (Tobj-Terr), the input voltage of the heater (1) gradually decreases, and the water temperature (To) of the thermostat (23) ) Reaches the threshold value, the heater (1) stops. Here, since the input voltage of the heater (1) when the heater (1) is stopped is lower than that in the case where the input voltage is not reduced by the adjustment unit (49), the heater (1) Therefore, the water temperature (To) of the thermostatic chamber (23) can be brought closer to the target temperature (Tobj) without further overshooting.

    The auxiliary heating unit (1) can be constituted by an electric heater, an IH heater, a steam heat source, a gas cooking heat source, or the like.

    As described above, the present invention relates to a heat pump system, and is particularly useful for a device including an auxiliary heating unit.

1 Heater (auxiliary heating part)
10 heat pump system 12 radiator (first heat exchanger)
22 Heating heat exchanger (second heat exchanger)
23 constant temperature bath
20 Heat medium circuit 40 Controller (Operation control unit)
50 Refrigerant circuit

Claims (2)

A refrigerant circuit (50) of a vapor compression refrigeration cycle to which a primary flow path (12a) of a first heat exchanger (12) functioning as a radiator is connected;
The secondary side flow path (12b) of the first heat exchanger (12) and the second heat exchanger (22) are connected, and the first heat exchanger (12) and the second heat exchanger (22 And a heat medium circuit (20) in which the heat medium heats the target fluid in the second heat exchanger (22).
The first heat exchanger (12) is a heat pump system that heats the heat medium of the heat medium circuit (20) to 100 ° C. or higher by the refrigerant of the refrigerant circuit (50),
An auxiliary heating unit (1) for heating the target fluid;
A threshold value smaller than a target value of the target fluid temperature is set, and the operation of the auxiliary heating unit (1) is permitted when the temperature of the target fluid is lower than the threshold value, and the temperature of the target fluid is the threshold value An operation control unit (40) for performing a first operation for prohibiting the operation of the auxiliary heating unit (1) at the time described above;
Equipped with a,
The operation control unit (40) stores an arrival time (t1) from the prohibition of the operation of the auxiliary heating unit (1) until the temperature of the target fluid reaches a target value, and the arrival time (t1 ) Is longer than the target arrival time (t0), the threshold is brought closer to the target value of the target fluid temperature, and when the arrival time (t1) is shorter than the target arrival time (t0), the threshold is A heat pump system that performs a third operation of moving away from a target value of the temperature of the fluid . In claim 1,
The operation control unit (40), when that allow the operation of the auxiliary heating unit (1), the heating capacity of the auxiliary heating unit such that the temperature of the target fluid approaches the threshold value (1) PI A heat pump system characterized by performing a second operation adjusted by control or PID control.

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