Heat source unit and refrigeration system

Abstract

To provide a heat source unit that suppresses deterioration of efficiency of a refrigeration device.SOLUTION: A heat source unit includes a compressor (22) and a radiator (23) constituting a refrigerant circuit (R) that executes a refrigeration cycle and connected to the refrigerant circuit (R). The refrigerant circuit (R) has an evaporator (33) connected thereto and includes a control section (100) that varies a frequency of the compressor (22) so that when pressure loss of suction piping (12) connecting the evaporator (33) and the compressor (22) during execution of the refrigeration cycle is defined as ΔP1, suction pressure of the compressor (22) becomes a value obtained by subtracting ΔP1 from preset suction pressure. ΔP1 is calculated on the basis of pressure loss ΔP0 of the suction piping (12) calculated beforehand and rotational frequency of the compressor (22).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a heat source unit and a refrigeration system. [Background technology]

[0002] The compressor provided in the air conditioner disclosed in Patent Document 1 compresses a low-pressure refrigerant in a refrigeration cycle until it reaches a high pressure. The compressor's capacity is controlled so that the evaporation temperature of the refrigerant approaches a target temperature during cooling operation, for example. The compressor's capacity is controlled by controlling the rotation speed (frequency) of the motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-172986 Summary of the Invention [Problem to be solved by the invention]

[0004] In a refrigeration system equipped with a utilization unit and a heat source unit, when compressor capacity control is performed based on a preset refrigerant intake temperature, a difference occurs between the intake temperature and the evaporation temperature due to pressure loss in the intake pipe between the evaporator and the compressor. The preset intake temperature can be maintained at a predetermined temperature by controlling the compressor capacity, but the evaporation temperature fluctuates depending on the compressor's rotation speed. When the compressor's rotation speed is relatively high, the evaporation temperature rises due to increased pressure loss in the intake pipe, while when the compressor's rotation speed is relatively low, the evaporation temperature falls due to decreased pressure loss in the intake pipe. Because the evaporation temperature is thus related to fluctuations in the cooling state in the utilization unit, conventionally, a predetermined evaporation temperature could be maintained by setting the intake temperature low even when the compressor's rotation speed was high, but this reduced the efficiency of the refrigeration system.

[0005] An object of the present disclosure is to provide a heat source unit that suppresses a decrease in the efficiency of a refrigeration device. [Means for solving the problem]

[0006] The first aspect is A heat source unit that configures a refrigerant circuit (R) that performs a refrigeration cycle, and includes a compressor (22) and a radiator (23) connected to the refrigerant circuit (R), An evaporator (33) is connected to the refrigerant circuit (R), When the refrigeration cycle is performed, the pressure loss in the intake pipe (12) connecting the evaporator (33) and the compressor (22) is represented by ΔP1. a control unit (100) that varies the frequency of the compressor (22) so that the suction pressure of the compressor (22) becomes a value obtained by subtracting ΔP1 from a preset suction pressure, The pressure loss ΔP1 is calculated based on a pre-calculated pressure loss ΔP0 in the suction pipe (12) and the rotation speed of the compressor (22). It is a heat source unit.

[0007] In the first mode, the suction pressure is variably set based on the pressure loss in the suction pipe (12), thereby stabilizing the evaporation temperature of the evaporator (33).

[0008] The second aspect is the first aspect, The ΔP0 is the pressure loss when the rotation speed of the compressor (22) is at its maximum.

[0009] In the second aspect, the evaporation temperature of the evaporator (33) can be controlled more accurately based on the pressure loss in the suction pipe (12) when the rotation speed of the compressor (22) is at its maximum.

[0010] A third aspect is a refrigeration system having a utilization unit (30) including the heat source unit (20) of the first or second aspect and the evaporator (33).

[0011] In a third aspect, a refrigeration system can be provided that includes the heat source unit (20) and the utilization unit (30) of the first or second aspect. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic piping diagram of an air conditioning apparatus according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the relationship between the control unit and various devices. [Figure 3] FIG. 3 is a flowchart showing the operation of the control unit. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or its uses. Furthermore, each configuration of the embodiments, modifications, other examples, etc. described below can be combined or partially substituted within the scope of the present invention.

[0014] (1) Refrigeration system The refrigeration system (10) of the present disclosure is applied to an air conditioner (10) that conditions a target space (S).

[0015] As shown in FIG. 1, the air conditioner (10) has a heat source unit (20) and a utilization unit (30). The heat source unit (20) and the utilization unit (30) are connected to each other via two connection pipes (a liquid connection pipe (11) and a gas connection pipe (12)). This forms a refrigerant circuit (R) in the air conditioner (10). The refrigerant circuit (R) is filled with a refrigerant. The refrigerant circuit (R) performs a refrigeration cycle by circulating the refrigerant. The gas connection pipe is a refrigerant pipe that connects the suction end of a compressor (22) (described later) with a utilization heat exchanger (33), and is an example of the suction pipe (12) of the present application.

[0016] (1-1) Heat source unit The heat source unit (20) is an outdoor unit arranged in the outdoor space (O). The heat source unit (20) constitutes a refrigerant circuit (R) that executes a refrigeration cycle. The heat source unit (20) has a heat source fan (21). The heat source unit (20) has, as elements connected to the refrigerant circuit (R), a compressor (22), a heat source heat exchanger (23), a switching mechanism (24), and an expansion mechanism (25). As will be described in detail later, the heat source heat exchanger (23) functions as a radiator when the refrigerant circuit (R) executes a cooling operation.

[0017] The compressor (22) compresses the drawn refrigerant. The compressor (22) discharges the compressed refrigerant. The compressor (22) is a rotary compressor such as a swing piston type. The compressor (22) is an inverter type. The rotation speed (operating frequency) of a first motor (M1) of the compressor (22) is adjusted by an inverter device. The compressor (22) is connected to a suction pipe (12) communicating with a utilization heat exchanger (33) described later. The refrigerant drawn into the compressor (22) flows through the suction pipe (12).

[0018] The heat source heat exchanger (23) is a fin-and-tube air heat exchanger, and serves as an outdoor heat exchanger for exchanging heat between the refrigerant flowing therethrough and outdoor air.

[0019] The heat source fan (21) is disposed near the heat source heat exchanger (23). In this example, the heat source fan (21) is a propeller fan. The heat source fan (21) transports air passing through the heat source heat exchanger (23).

[0020] The switching mechanism (24) changes the flow path of the refrigerant circuit (R) so as to switch between a first refrigeration cycle, which is a cooling cycle, and a second refrigeration cycle, which is a heating cycle. The switching mechanism (24) is a four-way switching valve. The switching mechanism (24) has a first port (P1), a second port (P2), a third port (P3), and a fourth port (P4). The first port (P1) of the switching mechanism (24) is connected to the discharge port of the compressor (22). The second port (P2) of the switching mechanism (24) is connected to the suction port of the compressor (22). The third port (P3) of the switching mechanism (24) is connected to the gas side end of the utilization heat exchanger (33) via the gas connection pipe (12). The fourth port (P4) of the switching mechanism (24) is connected to the gas side end of the heat source heat exchanger (23).

[0021] The switching mechanism 24 switches between a first state and a second state. In the first state (shown by the solid line in FIG. 2), the switching mechanism 24 connects the first port P1 to the fourth port P4 and connects the second port P2 to the third port P3. In the second state (shown by the dashed line in FIG. 2), the switching mechanism 24 connects the first port P1 to the third port P3 and connects the second port P2 to the fourth port P4.

[0022] The expansion mechanism (25) has one end connected to the liquid side end of the heat source heat exchanger (23) and the other end connected to the liquid side end of the utilization heat exchanger (33) via the liquid connection pipe (11). The expansion mechanism (25) is an expansion valve. The expansion mechanism (25) is an electronic expansion valve whose opening is adjustable.

[0023] (1-2) Usage unit The utilization unit (30) is installed in the target space (S). The utilization unit (30) has a utilization heat exchanger (33) as an element connected to the refrigerant circuit (R).

[0024] The utilization heat exchanger (33) is a fin-and-tube air heat exchanger. The utilization heat exchanger (33) exchanges heat between the air flowing therethrough and the refrigerant. As will be described in detail later, the utilization heat exchanger (33) functions as an evaporator when the refrigerant circuit (R) performs a cooling cycle.

[0025] The rotation speed of the second motor (M2) of the utilization fan (32) is variable. In other words, the air volume of the utilization fan (32) is variable. The utilization fan (32) transports air passing through the utilization heat exchanger (33).

[0026] (1-3) Sensor 2 and 3, the air conditioner (10) has a plurality of sensors. The plurality of sensors are, for example, temperature sensors such as an indoor air temperature sensor that detects the indoor air temperature and an outdoor air temperature sensor that detects the outdoor air temperature. The plurality of sensors are refrigerant sensors that detect the high-pressure pressure, low-pressure pressure, condensation temperature, evaporation temperature, etc. of the refrigerant circuit (R). The pressure sensor (41) that detects the low-pressure pressure of the refrigerant detects, for example, the suction pressure of the refrigerant sucked into the compressor (22).

[0027] (1-4) Control unit As shown in FIG. 2, the air conditioner (10) has a control unit (100). The control unit (100) controls the operation of various devices in the air conditioner (10). The control unit (100) is connected to the various devices in the air conditioner (10) so as to be able to communicate with them via wired or wireless communication. The control unit (100) includes an MCU (Micro Control Unit), an electric circuit, and an electronic circuit. The MCU includes a CPU (Central Processing Unit), a memory, and a communication interface. The memory stores various programs to be executed by the CPU.

[0028] (2) Driving behavior The air conditioner (10) performs cooling operation and heating operation.

[0029] (2-1) Cooling operation During cooling operation, the air conditioner (10) performs a refrigeration cycle (cooling cycle) in which the heat source heat exchanger (23) functions as a radiator and the utilization heat exchanger (33) functions as an evaporator. Specifically, the refrigerant compressed by the compressor (22) radiates heat in the heat source heat exchanger (23) and is decompressed by the expansion mechanism (25). The refrigerant decompressed by the expansion mechanism (25) evaporates in the utilization heat exchanger (33) and is drawn into the compressor (22).

[0030] In the utilization unit (30), the utilization fan (32) is put into operation. Air from the target space (S) is drawn into the intake port of the utilization unit (30), cooled by the utilization heat exchanger (33), and then supplied to the target space (S) through the outlet port.

[0031] (2-2) Heating operation During heating operation, the air conditioner (10) performs a refrigeration cycle (heating cycle) in which the utilization heat exchanger (33) functions as a radiator and the heat source heat exchanger (23) functions as an evaporator. Specifically, the refrigerant compressed by the compressor (22) radiates heat in the utilization heat exchanger (33) and is decompressed by the expansion mechanism (25). The refrigerant decompressed by the expansion mechanism (25) evaporates in the heat source heat exchanger (23) and is drawn into the compressor (22).

[0032] In the utilization unit (30), the utilization fan (32) is in operation. Air from the target space (S) is drawn into the intake port of the utilization unit (30), heated by the utilization heat exchanger (33), and then supplied to the target space (S) through the outlet port (30b).

[0033] (3) Issues In a refrigeration device such as a condensing unit in which the utilization unit is not packaged, when the compressor capacity is controlled at a preset refrigerant intake temperature, for example during refrigeration operation, the refrigerant flow rate associated with the compressor capacity control increases or decreases the pressure loss in the intake piping connected between the indoor heat exchanger functioning as an evaporator and the compressor, causing fluctuations in the difference between the intake temperature and the evaporation temperature.

[0034] In other words, the preset intake temperature can be maintained by controlling the compressor capacity, but the evaporation temperature varies depending on the compressor load. Therefore, when the compressor load is relatively high, the evaporation temperature increases due to the increase in pressure loss in the intake pipe, while when the compressor load is low, the evaporation temperature decreases due to the decrease in pressure loss in the intake pipe.

[0035] Such fluctuations in evaporation temperature lead to fluctuations in the cooling state of the air in the utilization unit, so in the past this was addressed by setting the intake temperature low so that the specified evaporation temperature could be ensured even when the compressor load was high, which resulted in a decrease in the efficiency of the refrigeration unit.

[0036] Furthermore, in refrigeration systems where the evaporation temperature is close to 0°C and evaporator frost is not possible, simply setting the refrigerant intake temperature to the compressor can result in the intake temperature and evaporation temperature becoming close to each other when the cooling load on the evaporator is reduced. As a result, depending on the intake temperature setting, the evaporation temperature can fall below 0°C, causing frost to form on the evaporator. This has led to the need to add a device to control the evaporation temperature, such as an evaporation pressure control valve, to the intake piping between the evaporator and the compressor. However, adding such an evaporation pressure control valve further increases pressure loss in the intake piping system, further reducing the efficiency of the refrigeration system.

[0037] In contrast, when the pressure loss in the intake pipe (12) connecting the utilization heat exchanger (33) functioning as an evaporator and the compressor (22) is ΔP1, the control unit (100) of the refrigeration system of the present disclosure varies the frequency of the compressor so that the intake pressure of the compressor (22) becomes a value obtained by subtracting ΔP1 from a preset intake pressure, when the pressure loss in the intake pipe (12) connecting the utilization heat exchanger (33) functioning as an evaporator and the compressor (22) is ΔP1.

[0038] Specifically, the control unit (100) calculates ΔP1 based on a pre-calculated pressure loss ΔP0 in the suction pipe (12) and the rotation speed of the compressor (22). In this embodiment, the pressure loss ΔP0 is the pressure loss when the rotation speed of the compressor (22) is at its maximum. That is, the control unit (100) stores the pressure loss when the load of the compressor (22) is 100% as ΔP0.

[0039] (4) Operation of the control device With reference to FIG. 3, the suction pressure control by the control section (100) of this embodiment will be described.

[0040] In step S11, the control section (100) detects the suction pressure PV of the refrigerant from the pressure sensor (41).

[0041] In step S12, the control section (100) corrects the set value SV of the refrigerant suction pressure based on the current rotation speed of the compressor (22) and the stored ΔP0. When the set value of the suction pressure after the correction is the corrected SV, the corrected SV can be expressed as: Corrected SV=SV−ΔP1. ΔP1 is calculated using the following equation: ΔP1=ΔP0×H 2 (H: Ratio of the current rotation speed of the compressor (22) to the maximum rotation speed of the compressor) In step S13, the control section (100) controls the frequency of the compressor (22) based on the corrected SV so that the suction pressure PV is equal to the corrected SV.

[0042] In step S14, the control unit (100) determines whether a signal to stop the operation of the air conditioner (10) has been input. If it is determined that a signal to stop the operation of the air conditioner (10) has been input (YES in step S14), the control flow ends. If it is determined that a signal to stop the operation of the air conditioner (10) has not been input (NO in step S14), step S11 is executed again.

[0043] In this way, according to the control flow of this embodiment, ΔP1 can be regarded as the pressure loss of the refrigerant in the suction pipe (12). As a result, the set value of the suction pressure of the compressor (22) can be controlled to the evaporation pressure P of the evaporator by operating the compressor (22) so as to be equal to the pressure (corrected SV) obtained by subtracting ΔP1 from the current suction pressure SV.

[0044] (5) Features (5-1) Feature 1 In the air conditioner (10) of this embodiment, when the cooling cycle is performed, the control unit (100) varies the frequency of the compressor (22) so that the suction pressure of the compressor (22) becomes a value obtained by subtracting ΔP1 from a preset suction pressure, where ΔP1 is a pressure loss in the suction pipe (12) connecting the evaporator (33) and the compressor (22). ΔP1 is calculated based on a previously calculated pressure loss ΔP0 in the suction pipe (12) and the rotation speed of the compressor (22).

[0045] In this way, by variably setting the suction pressure based on the pressure loss in the suction pipe (12), it is possible to stabilize the evaporation temperature of the utilization heat exchanger (33) functioning as an evaporator. In addition, since it is not necessary to determine the evaporation pressure of the utilization heat exchanger (33) functioning as an evaporator, it is possible to easily control the frequency of the compressor (22).

[0046] (5-2) Feature 2 In the air conditioner (10) of this embodiment, ΔP0 is the pressure loss when the rotation speed of the compressor (22) is at its maximum. By using the pressure loss in the suction pipe (12) when the rotation speed of the compressor is at its maximum, the evaporation temperature of the evaporator (33) can be controlled more accurately.

[0047] (5-3) Feature 3 In the air conditioner (10) of this embodiment, the compressor (22) and the heat-source heat exchanger (23) functioning as a radiator are provided in the heat source unit (20). In this manner, this embodiment can also utilize a condensing unit (heat source unit) that is not packaged with the refrigeration system (10). That is, there is no need to detect the evaporation pressure from the utilization heat exchanger (33) of the utilization unit (30), and the condensing unit alone can easily control the rotation speed of the compressor (22) so as to maintain the evaporation pressure at a predetermined pressure. Because the condensing unit alone can control the compressor (22), the number of parts can be reduced, and the complexity of controlling the evaporation pressure of the utilization heat exchanger (33) can be reduced.

[0048] (6) Other embodiments The air conditioner of the above embodiment does not have to be configured to be able to switch between cooling and heating, and may be an air conditioner having a refrigerant circuit that can perform only cooling operation.

[0049] The refrigeration system (10) of the above embodiment may be applied to refrigeration devices other than the air conditioner (10).

[0050] The control unit (100) that executes the control flow of the above embodiment may be configured as a separate entity from the heat source unit (20). For example, the control unit (100) may be provided in a communication device that controls the air conditioner via a predetermined server. The control unit (100) may also be a program that executes the control flow of the above embodiment.

[0051] Although the embodiments and modifications have been described above, it will be understood that various modifications in form and detail are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments and modifications may be combined or substituted as appropriate as long as the functionality of the subject matter of this disclosure is not impaired. The terms "first," "second," etc., described above, are used to distinguish the terms to which these terms are attached, and do not limit the number or order of the terms. [Industrial Applicability]

[0052] INDUSTRIAL APPLICABILITY As described above, the present disclosure is useful for heat source units and refrigeration systems. [Explanation of symbols]

[0053] 10 Air conditioning equipment (refrigeration system) 12 Intake piping 20 Heat source unit 22 Compressor 23 Heat source heat exchanger (radiator) 30 usage units 33 Utilization heat exchanger (evaporator) 100 control section R Refrigerant circuit

Claims

1. A heat source unit that forms a refrigerant circuit (R) that performs a refrigeration cycle, and includes a compressor (22) and a radiator (23) connected to the refrigerant circuit (R), An evaporator (33) is connected to the refrigerant circuit (R), When the refrigeration cycle is performed, the pressure loss in the intake pipe (12) connecting the evaporator (33) and the compressor (22) is ΔP 1 When The suction pressure of the compressor (22) is increased by ΔP from a preset suction pressure. 1 a control unit (100) that varies the frequency of the compressor (22) so that the value obtained by subtracting Said ΔP 1 is the pressure loss ΔP of the suction pipe (12) calculated in advance. ０ and the rotation speed of the compressor (22). Heat source unit.

2. Said ΔP ０ is the pressure loss when the rotation speed of the compressor (22) is at its maximum. The heat source unit according to claim 1 .

3. A refrigeration system comprising a utilization unit (30) including the heat source unit (20) according to claim 1 or 2 and the evaporator (33).

Images