Refrigeration cycle device

Abstract

Provided is a refrigeration cycle device (300) comprising: a refrigeration cycle circuit (100) that includes at least a compressor (1), a condenser (3), and an evaporator (2) and that is filled with a refrigerant; at least two temperature sensors (2a, 2b) that are attached to the evaporator (2) and that measure the temperature of the refrigerant passing through the evaporator (2); and a control device (200) that, on the basis of the temperatures measured by the at least two temperature sensors (2a, 2b), determines whether or not to start or end a defrosting operation of the evaporator (2) or determines whether or not to change a frost formation location of the evaporator (2) by changing the discharge amount of the compressor (1). The refrigerant has a temperature glide characteristic in which the temperature changes under a constant pressure in a two-phase state.

Description

Refrigeration cycle device

[0001] The present disclosure relates to a refrigeration cycle device.

[0002] In recent years, from the perspective of reducing the environmental load of refrigeration cycle devices, it has been required to apply refrigerants with a low GWP (Global Warming Potential) to the refrigerants used in refrigeration cycle devices. For example, it has been proposed to apply a mixed refrigerant containing low-GWP refrigerants such as HFO-1123 and HFO-1132(E) to a refrigeration cycle device.

[0003] Among mixed refrigerants, there exist non-azeotropic mixed refrigerants in which refrigerants having different boiling points are mixed. Unlike a single refrigerant and a pseudo-azeotropic refrigerant, a non-azeotropic mixed refrigerant has the property that in a two-phase state, even under a constant pressure, the temperature changes due to the transfer of thermal energy. This property that the temperature changes under a constant pressure in the two-phase state is generally called temperature glide.

[0004] When a refrigerant having temperature glide is applied to a refrigeration cycle device, the temperature distribution of the refrigerant in the evaporator is affected by the refrigerant pressure and the transfer of thermal energy. For this reason, when the evaporator exchanges heat with air and frosting occurs, the frosting distribution greatly changes depending on the operating conditions.

[0005] Japanese Unexamined Patent Application Publication No. 2020-165581 (Patent Document 1) proposes a technique related to defrosting operation that addresses uneven frosting distribution when a refrigerant having temperature glide is applied to a refrigeration cycle device.

[0006] Japanese Unexamined Patent Application Publication No. 2020-165581

[0007] However, the frosting distribution of a refrigerant having temperature glide changes depending on factors such as the pressure loss of the refrigerant flowing inside the evaporator and the distribution of the heat exchange amount. For this reason, when the operating condition changes, the frosting distribution changes greatly, so the problem is that it is necessary to grasp or predict the frosting distribution during operation in order to perform an appropriate defrosting operation and maintain the heat exchange performance of the evaporator.

[0008] This disclosure was made to solve the problems described above. The purpose of this disclosure is to provide a technology that enables the understanding or prediction of frost distribution during operation in a refrigeration cycle system using a refrigerant with temperature glide, and to maintain the heat exchange performance of the evaporator through appropriate defrosting operation.

[0009] This disclosure relates to a refrigeration cycle device. The refrigeration cycle device includes at least a compressor, a condenser, and an evaporator, a refrigeration cycle circuit filled with a refrigerant, at least two temperature sensors attached to the evaporator for measuring the temperature of the refrigerant passing through the evaporator, and a control device that determines whether to start or end a defrosting operation of the evaporator or to change the location of frost on the evaporator by changing the discharge rate of the compressor, based on the temperatures measured by the at least two temperature sensors. The refrigerant has the characteristic of temperature glide, which changes temperature under constant pressure in a two-phase state.

[0010] According to the refrigeration cycle device of this disclosure, when a refrigerant having a temperature glide is applied, it is possible to understand or predict the frost distribution during operation and maintain the heat exchange performance of the evaporator through appropriate defrosting operation.

[0011] This is a schematic refrigerant circuit diagram showing an example of a refrigeration cycle device according to Embodiment 1. This figure shows the state in which the circulation direction of the refrigerant is changed by switching a four-way valve. This is a schematic diagram showing the positional relationship between the heat source side heat exchanger 2 according to Embodiment 1, the refrigerant piping of the heat source side heat exchanger 2, and the temperature sensor. This is a schematic graph showing the change in refrigerant temperature when the circulation amount of refrigerant passing through the heat source side heat exchanger 2 according to Embodiment 1 is low, and the temperature detected by the temperature sensor shown in Figure 3. This is a schematic graph showing the change in refrigerant temperature when the circulation amount of refrigerant passing through the heat source side heat exchanger 2 according to Embodiment 1 is high, and the temperature detected by the temperature sensor shown in Figure 3. This is a diagram summarizing the relationship between pressure loss due to the evaporator and the temperature change of the refrigerant in a two-phase state. This is a flowchart for explaining the determination process executed by the control device 200 in Embodiment 1. This is a schematic diagram showing the positional relationship between the heat source side heat exchanger 2 according to Embodiment 2, in which the number of passes of the refrigerant piping changes midway, and the refrigerant piping of the heat source side heat exchanger 2 and the temperature sensor. This is a schematic diagram showing the positional relationship between the heat source side heat exchanger 2 having a branch to a bypass circuit according to Embodiment 2, the refrigerant piping of the heat source side heat exchanger 2, and the temperature sensor. This is a schematic graph showing the change in refrigerant temperature when the circulation rate of refrigerant passing through the heat source side heat exchanger 2 according to Embodiment 2 is low, and the temperature detected by the temperature sensor shown in Figure 8 or Figure 9. This is a schematic graph showing the change in refrigerant temperature when the circulation rate of refrigerant passing through the heat source side heat exchanger 2 according to Embodiment 2 is high, and the temperature detected by the temperature sensor shown in Figure 8 or Figure 9. This is a schematic graph showing the change in refrigerant temperature when the circulation rate of refrigerant passing through the heat source side heat exchanger 2 according to Embodiment 2 is moderate, and the temperature detected by the temperature sensor shown in Figure 8 or Figure 9. This is a flowchart for explaining the determination process executed by the control device 200 in Embodiment 2. This is a schematic refrigerant circuit diagram showing the promotion of defrosting at frost-covered areas by changing the direction of refrigerant flow using a bridge circuit according to Embodiment 3. This is a flowchart for explaining the determination process executed by the control device 200 in Embodiment 3. This is a schematic refrigerant circuit diagram illustrating the defrosting promotion at frost-covered locations using a bypass path according to Embodiment 4. This diagram shows the refrigerant flow during defrosting operation of the heat source side heat exchanger 2 in Embodiment 4.This is a flowchart illustrating the determination process performed by the control device 200 in Embodiment 4.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. While multiple embodiments will be described below, it has been intended from the outset that the configurations described in each embodiment can be appropriately combined. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0013] Embodiment 1. An overview of the refrigeration cycle circuit and refrigeration cycle device of this embodiment will be described. Figure 1 is a schematic refrigerant circuit diagram showing an example of a refrigeration cycle device according to Embodiment 1.

[0014] Referring to Figure 1, the refrigeration cycle device 300 comprises a compressor 1, a heat source side heat exchanger 2, a utilization side heat exchanger 3, an expansion mechanism 4, and a four-way valve 5. The refrigeration cycle circuit 100 is composed of the components of the refrigeration cycle device 300 and the piping connecting these components. The refrigeration cycle device 300 of Embodiment 1 may comprise multiple sets of the refrigeration cycle circuit 100 and their components.

[0015] A refrigerant having a temperature glide is sealed inside the refrigeration cycle circuit 100. In this embodiment, this refrigerant is generally a non-azeotropic mixed refrigerant. For example, when the user-side heat exchanger 3 functions as a condenser, such as in heating operation during air conditioning, the refrigerant circulates in the following order, as shown in Figure 1: compressor 1, four-way valve 5, user-side heat exchanger 3, expansion mechanism 4, heat source-side heat exchanger 2, four-way valve 5, and compressor 1.

[0016] Figure 2 shows the state in which the circulation direction of the refrigerant is changed by switching the four-way valve. For example, when the user-side heat exchanger 3 functions as an evaporator, such as in cooling operation or defrosting operation during air conditioning, the refrigerant circulates in the following order, as shown in Figure 2: compressor 1, four-way valve 5, heat source-side heat exchanger 2, expansion mechanism 4, user-side heat exchanger 3, four-way valve 5, and compressor 1.

[0017] The refrigeration cycle device 300 includes a control device 200. The control device 200 is, for example, a microcomputer. The control device 200 is connected to each actuator and sensor provided in the refrigeration cycle device 300.

[0018] The switching of the refrigerant flow direction shown in Figures 1 and 2 is also achieved by switching the flow path of the four-way valve 5 based on a command from the control device 200.

[0019] The control device 200 comprises a CPU (Central Processing Unit) 201, memory 202 (ROM (Read Only Memory) and RAM (Random Access Memory)), and input / output buffers (not shown) for inputting and outputting various signals. The CPU 201 loads the program stored in the ROM into the RAM and executes it. The program stored in the ROM is a program that describes the processing procedure of the control device 200. The control device 200 controls each device in the refrigeration cycle device 300 according to these programs. This control is not limited to software processing; it can also be processed by dedicated hardware (electronic circuits).

[0020] Next, regarding the flow of refrigerant in the refrigeration cycle circuit 100, we will explain using an example where the heat exchanger 3 on the user side functions as a condenser, as in the heating system of an air conditioning system.

[0021] As shown by the arrow in Figure 1, the compressor 1 draws in refrigerant, compresses it, and discharges it as a high-temperature, high-pressure gas. The rotational speed of the compressor 1 is controlled by, for example, an inverter circuit. The amount of refrigerant discharged is adjusted by controlling the rotational speed. However, the compressor 1 does not necessarily have an inverter circuit and may be controlled by a fixed rotational speed.

[0022] The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 1 flows into the utilization-side heat exchanger 3 after passing through the four-way valve 5.

[0023] The user-side heat exchanger 3 performs heat exchange between the refrigerant and a medium outside the refrigeration cycle circuit 100 to cool the refrigerant to a low-temperature, high-pressure liquid state. Examples of the medium outside the refrigeration cycle circuit 100 include air, water, brine, etc. To facilitate heat exchange in the user-side heat exchanger 3, a blower and pump that can adjust the flow rate of the medium may be provided.

[0024] The expansion mechanism 4 receives refrigerant in a low-temperature, high-pressure liquid state, cooled by the user-side heat exchanger 3. The expansion mechanism 4 depressurizes and expands the refrigerant into a low-temperature, low-pressure two-phase state. The expansion mechanism 4 is composed of, for example, a capillary tube, an electronic expansion valve, a temperature-sensitive expansion mechanism, or a differential pressure expansion mechanism, as well as other means for controlling the refrigerant flow rate.

[0025] In the case shown in Figure 1 (for example, during heating operation), the refrigerant flows into the heat source side heat exchanger 2 from port P1 and flows out from port P2.

[0026] A low-temperature, low-pressure, two-phase refrigerant, which has been depressurized and expanded by the expansion mechanism 4, flows into the heat source side heat exchanger 2 from port P1. The heat source side heat exchanger 2 performs heat exchange between the refrigerant and a medium outside the refrigeration cycle circuit 100, heating the refrigerant to a high-temperature, low-pressure gaseous state. Examples of the medium include air, water, brine, etc. In the example of Embodiment 1, air is used as the external medium for heat exchange in the heat source side heat exchanger 2. To promote heat exchange in the heat source side heat exchanger 2, the heat source side heat exchanger 2 may be equipped with a blower that can adjust the airflow rate.

[0027] The refrigerant, which has become a high-temperature, low-pressure gas in the heat source side heat exchanger 2, flows out from port P2, passes through the four-way valve 5 again, and is then drawn into the compressor 1 and compressed again. As a result, the refrigerant circulates within the refrigeration cycle circuit 100, transferring heat from the external medium from the heat source side heat exchanger 2 to the utilization side heat exchanger 3.

[0028] The refrigeration cycle device 300 can be used, for example, for air conditioning, and by making the user-side heat exchanger 3 function as a condenser, it can perform heating operation to warm the room.

[0029] If the user-side heat exchanger 3 is functioning as a condenser, the heat source-side heat exchanger 2 is functioning as an evaporator. The heat source-side heat exchanger 2 is exchanging heat with air, and if the surface temperature of the heat source-side heat exchanger 2 is below freezing, frost may form on the surface of the heat source-side heat exchanger 2 due to the solidification of moisture in the air.

[0030] If frost accumulates on the surface of the heat source side heat exchanger 2, the resulting frost creates thermal resistance, hindering heat exchange between the heat source side heat exchanger 2 and the air. This can lead to a decrease in the performance of the heat source side heat exchanger 2, making it difficult to maintain heating operation, for example.

[0031] One way to remove frost from the surface of the heat source side heat exchanger 2 is, for example, to interrupt the heating operation and change the direction of the refrigerant flow by switching the flow path of the four-way valve 5, as shown in Figure 2. This introduces high-temperature, high-pressure refrigerant discharged from the compressor 1 into the heat source side heat exchanger 2, raising the surface temperature of the heat source side heat exchanger 2 and melting and removing the frost. This operation is generally called defrosting operation.

[0032] As shown in Figure 2, during defrosting, refrigerant flows into the heat source side heat exchanger 2 from port P2 and flows out from port P1. In Figure 2, the direction of refrigerant flow during defrosting is schematically shown by the direction of the arrows.

[0033] However, during the defrosting operation period, it is difficult to make the user-side heat exchanger 3 function as a condenser. For example, since heating operation is interrupted during the defrosting operation period, the refrigeration cycle device 300 cannot provide the functions that are originally required of it.

[0034] Therefore, defrosting operations should not be performed unnecessarily frequently or for extended periods; they should be started and stopped at appropriate times.

[0035] The control device 200 controls the switching to defrosting operation and determines the start and end of the defrosting operation. Therefore, it is necessary to understand the frost formation state on the surface of the heat source side heat exchanger 2 based on information from temperature sensors and other devices connected to the control device 200.

[0036] Figure 3 is a schematic diagram of the heat source side heat exchanger 2. Figures 4 and 5 show the temperature change of the refrigerant when a refrigerant with thermal glide passes through the heat exchanger shown in Figure 3 while absorbing heat.

[0037] When the circulating amount Gr of refrigerant passing through the heat source side heat exchanger 2 is smaller than the judgment value Gr1, the pressure loss occurring inside the refrigerant piping of the heat source side heat exchanger 2 is small, and the pressure change of the refrigerant from the inlet to the outlet of the heat source side heat exchanger 2 is small.

[0038] When the pressure change of the refrigerant from the inlet to the outlet of the heat source side heat exchanger 2 is small, as shown in Figure 4, the temperature of the heat-absorbing refrigerant rises from the inlet to the outlet of the heat source side heat exchanger 2 due to thermal glide.

[0039] On the other hand, if the circulating amount Gr of refrigerant passing through the heat source side heat exchanger 2 is greater than the judgment value Gr1, the pressure loss occurring inside the refrigerant piping of the heat source side heat exchanger 2 will be large, and the pressure of the refrigerant will decrease from the inlet to the outlet of the heat source side heat exchanger 2.

[0040] When the refrigerant pressure from the inlet to the outlet of the heat source side heat exchanger 2 drops significantly, as shown in Figure 5, the temperature of the flowing refrigerant decreases from the inlet to the outlet of the heat source side heat exchanger 2 in accordance with the pressure drop.

[0041] Frost formation occurs in the heat source side heat exchanger 2 in areas where the refrigerant temperature falls below the frost formation temperature, which is a specific temperature determined by the heat exchanger's specifications. As shown in Figure 4, when the refrigerant temperature rises from the inlet to the outlet of the heat source side heat exchanger 2, frost formation occurs near the inlet of the heat source side heat exchanger 2. Also, as shown in Figure 5, when the refrigerant temperature decreases from the inlet to the outlet of the heat source side heat exchanger 2, frost formation occurs near the outlet of the heat source side heat exchanger 2.

[0042] Figure 6 is a diagram that summarizes the relationship between pressure loss due to the evaporator and the temperature change of the refrigerant in a two-phase state.

[0043] First, if the pressure loss in the evaporator shown in the upper part of Figure 6 is negligible, for example, if the refrigerant circulation rate Gr is less than the judgment value Gr0, then in the case of a pure refrigerant (single refrigerant), the refrigerant temperature inside the evaporator is constant in the two-phase state. On the other hand, in the case of a refrigerant that has a thermal glide, such as a non-azeotropic mixed refrigerant, the refrigerant temperature rises due to the absorption of heat by the refrigerant as it moves from the refrigerant inlet to the refrigerant outlet of the evaporator.

[0044] In contrast, if the pressure loss in the evaporator shown in the lower part of Figure 6 is not negligible, for example, if the refrigerant circulation rate Gr is greater than the judgment value Gr0, then in the case of a pure refrigerant (single refrigerant), the pressure loss increases in the two-phase state, and the refrigerant temperature inside the evaporator decreases as it moves from the refrigerant inlet to the refrigerant outlet.

[0045] On the other hand, in the case of refrigerants that have a temperature glide, such as non-azeotropic mixed refrigerants, when the refrigerant circulation rate is greater than the judgment value Gr1 (>Gr0), the refrigerant temperature decreases as it moves from the refrigerant inlet to the refrigerant outlet of the evaporator, and when the refrigerant circulation rate is less than the judgment value Gr1 (>Gr0), the refrigerant temperature increases as it moves from the refrigerant inlet to the refrigerant outlet of the evaporator.

[0046] The refrigerant circulation rate determination value Gr1, which is the threshold value for whether the temperature of a refrigerant with thermal glide rises or falls from the inlet to the outlet of the heat source side heat exchanger 2, changes depending on the specifications and operating conditions of the heat source side heat exchanger 2. Therefore, estimating the determination value Gr1 requires numerous tests using actual equipment, which involves considerable effort.

[0047] In this embodiment, as shown in Figure 3, multiple temperature sensors, such as temperature sensors 2a and 2b, are provided. When the refrigerant is flowing as shown in Figure 3, temperature sensor 2a is positioned upstream of temperature sensor 2b. This makes it possible to grasp the temperature change of the refrigerant without estimating the judgment value Gr1. The control device 200 can determine from the measured temperatures of temperature sensors 2a and 2b whether or not the heat source side heat exchanger 2 is in a state where frost may form.

[0048] Figure 7 is a flowchart illustrating the determination process performed by the control device 200 in Embodiment 1.

[0049] First, in step S1, the control device 200 detects the temperature T detected by the temperature sensor 2a ２ａ is the frost formation determination temperature T ｆｒｏ Determine whether it is lower than. If T ２ａ is T ｆｒｏ If it is lower (YES in S1), in step S3, the control device 200 determines that defrosting is required and starts the defrosting operation. On the other hand, if T ２ａ is T ｆｒｏ If it is equal to or higher than (NO in S1), in step S2, the control device 200 detects the temperature T detected by the temperature sensor 2b ２ｂ is the frost formation determination temperature T ｆｒｏ Determine whether it is lower than. If T ２ｂ is T ｆｒｏ If it is lower (YES in S2), in step S3, the control device 200 determines that defrosting is required and starts the defrosting operation. Note that if T ２ｂ is T ｆｒｏ If it is equal to or higher than (NO in S2), the control device 200 returns the process to step S1 again and continues monitoring whether defrosting is required.

[0050] By performing the process shown in FIG. 7, even if the temperature distribution of the evaporator is as shown in FIG. 4 or as shown in FIG. 5, it is not necessary to estimate the refrigerant circulation amount, and the frost formation determination temperature T in the evaporator ｆｒｏ When a portion lower than the above occurs, the defrosting operation can be started at an appropriate timing.

[0051] As described above, by more reliably determining the frost formation state of the heat-source-side heat exchanger 2 from the temperatures measured by the temperature sensors 2a and 2b, the control device 200 can appropriately determine the start and end of the defrosting operation.

[0052] Further, when the compressor 1 has an inverter circuit and can change the discharge amount, the following is further possible.

[0053] The control device 200 is configured to control the refrigerant discharge rate of the compressor 1 so that the temperatures of at least two temperature sensors 2a and 2b do not fall below the frosting temperature. That is, based on the temperatures measured by the temperature sensors 2a and 2b, the control device 200 changes the refrigerant discharge rate of the compressor 1, and for example, by matching the refrigerant circulation rate Gr to a determination value Gr1, it is possible to control the refrigerant temperature of the heat source side heat exchanger 2 so that it does not fall below the frosting temperature. In addition, by gradually changing the refrigerant circulation rate Gr, the start of the defrosting operation until frost forms on the entire surface of the heat source side heat exchanger 2 can be delayed.

[0054] Furthermore, in the heat source side heat exchanger 2, for example, by narrowing the fin pitch to improve heat exchange performance and raise the fin surface temperature to suppress frost formation, or conversely, by widening the fin pitch to suppress airflow blockage due to frost formation, it is possible to create a section of the heat source side heat exchanger 2 with improved frost resistance, and adjust the refrigerant discharge rate so that the section where the refrigerant temperature is lowest coincides with the section with improved frost resistance.

[0055] In this embodiment, the frost formation phenomenon on the heat source side heat exchanger 2 was used as an example for explanation, but this technology can also be applied when the frost formation phenomenon occurs on the utilization side heat exchanger 3. Furthermore, in the case of a heat exchanger where the external medium that exchanges heat with the refrigerant is water, the frost formation phenomenon may be replaced with a freeze-puncture phenomenon and the control described in this embodiment may be applied.

[0056] Furthermore, although we have described an example with one evaporator, the evaporator system may also consist of multiple evaporators. In this case, the section from the refrigerant inlet of the first evaporator the refrigerant passes through after being discharged from the compressor to the refrigerant outlet of the last evaporator the refrigerant passes through will be called the evaporator refrigerant flow path. At this time, if we consider the points in the evaporator refrigerant flow path where the number of passes in the refrigerant piping changes, where the diameter of the refrigerant piping changes, where the pressure of the flowing refrigerant changes due to changes in the amount of bending in the refrigerant piping or the width of the flow path, or where it branches off to a bypass circuit, as observation points, then we can configure the system to have temperature sensors at least at two locations among the evaporator inlet, the evaporator outlet, and the observation points, and perform similar control.

[0057] Embodiment 2. The only difference between Embodiment 2 and Embodiment 1 is the specification of the evaporator; the other components of the refrigeration cycle circuit 100 are the same. Therefore, the operation of the refrigerant in the refrigeration cycle circuit 100 is the same as in Embodiment 1, and will not be explained. In addition, as with Embodiment 1, only the heat source side heat exchanger 2, which functions as an evaporator, will be described as an example in Embodiment 2.

[0058] Figures 8 and 9 are schematic diagrams showing the heat source side heat exchanger 2 according to Embodiment 2. Figures 10, 11, and 12 are diagrams showing the distribution of refrigerant temperature in the evaporator in Embodiment 2.

[0059] In Figure 8, there is a point C0 in the heat source side heat exchanger 2, where the refrigerant flows from port P1 to port P2, where the number of refrigerant piping passes changes from 1 to 2. In Figure 8, the refrigerant flow velocity changes at the heat exchange points in the heat source side heat exchanger 2 before and after point C0, and the refrigerant pressure loss changes.

[0060] In Figure 9, point C1 is located in the heat source side heat exchanger 2, where the refrigerant flows from port P1 to port P2, and is a point where it branches off to a bypass path. In Figure 9, the refrigerant flow velocity changes at the heat exchange points in the heat source side heat exchanger 2 before and after point C1, and the refrigerant pressure loss changes as a result.

[0061] Figure 10 is a schematic graph showing the change in refrigerant temperature when the circulation rate of refrigerant passing through the heat source side heat exchanger 2 according to Embodiment 2 is low, and the temperature detected by the temperature sensor shown in Figure 8 or Figure 9. Figure 11 is a schematic graph showing the change in refrigerant temperature when the circulation rate of refrigerant passing through the heat source side heat exchanger 2 according to Embodiment 2 is high, and the temperature detected by the temperature sensor shown in Figure 8 or Figure 9. Figure 12 is a schematic graph showing the change in refrigerant temperature when the circulation rate of refrigerant passing through the heat source side heat exchanger 2 according to Embodiment 2 is moderate, and the temperature detected by the temperature sensor shown in Figure 8 or Figure 9.

[0062] Due to pressure loss in the heat source side heat exchanger 2, differences in the temperature distribution in the evaporator may occur, as shown in Figures 10 to 12.

[0063] If the circulation rate Gr of the refrigerant passing through the heat source side heat exchanger 2 is less than the judgment value Gr1, as shown in Figure 10, the temperature of the heat-absorbing refrigerant rises from the inlet P1 to the outlet P2 of the heat source side heat exchanger 2 due to thermal glide.

[0064] If the circulating amount Gr of refrigerant passing through the heat source side heat exchanger 2 is greater than the judgment value Gr2, as shown in Figure 11, the temperature of the flowing refrigerant decreases from the inlet P1 to the outlet P2 of the heat source side heat exchanger 2 as the pressure decreases.

[0065] When the refrigerant circulation rate Gr passing through the heat source side heat exchanger 2 is between the judgment values ​​Gr1 and Gr2, as shown in Figure 12, upstream of point C0 (or C1) where the temperature is measured by the temperature sensor 2b, the refrigerant temperature decreases due to the pressure drop. Downstream of point C0 (or C1), the refrigerant temperature increases due to temperature glide. In this case, the phenomenon occurs where the refrigerant temperature is lowest at point C0 (or C1).

[0066] Figure 13 is a flowchart illustrating the determination process performed by the control device 200 in Embodiment 2.

[0067] First, in step S21, the control device 200 determines that the measured temperature is T ２ａ <T ２ｂ Determine whether or not the measurement temperature is T. ２ａ <T ２ｂ If (YES in S21), in step S22, the control device 200 determines that the measured temperature is T ２ａ <T ｆｒｏ Determine whether or not it is true.

[0068] The measured temperature is T ２ａ <T ｆｒｏ If the result is not positive (NO in S22), the process returns to step S21, and the determination of whether defrosting is necessary continues.

[0069] On the other hand, the measured temperature is T ２ａ <T ｆｒｏ If this is the case (YES in S22), in step S23, the control device 200 will determine that the measured temperature is T ２ｂ <T ｆｒｏ Or the compressor operating frequency is FＣ > F Ｃｍａｘ We determine whether or not this is the case. Here, F Ｃｍａｘ This indicates the predetermined upper limit of the compressor's operating frequency.

[0070] T ２ｂ <T ｆｒｏ or F Ｃ > F Ｃｍａｘ If this condition is met (YES in S23), the process proceeds to step S28. On the other hand, T ２ｂ <T ｆｒｏ F Ｃ > F Ｃｍａｘ If none of the above conditions are met (NO in S23), in step S24, the control device 200 operates the compressor at an operating frequency F for a period of time TFmax. Ｃｍａｘ After the operation, the process proceeds to step S28.

[0071] On the other hand, in step S21, T ２ａ <T ２ｂ If not (NO in S21), in step S25, the control device 200 will ２ｂ <T ｆｒｏ Determine whether or not it is true.

[0072] T ２ｂ <T ｆｒｏ If the result is not positive (NO in S25), the process returns to step S21, and the determination of whether defrosting is necessary continues.

[0073] Meanwhile, T ２ｂ <T ｆｒｏ If this is the case (YES in S25), in step S26, the control device 200 will Ｃ <F Ｃｍｉｎ We determine whether or not this is the case. Here, F Ｃｍｉｎ This indicates the predetermined lower limit of the compressor's operating frequency.

[0074] F Ｃ <F Ｃｍｉｎ If this condition is met (YES in S26), the process proceeds to step S28. On the other hand, F Ｃ <F Ｃｍｉｎ If the condition is not met (NO in S26), in step S27, the control device 200 will measure the temperature T ２ｂ The operating frequency F of the compressor increasesＣ The value is lowered, and the process returns to step S21.

[0075] In the above process, when the process proceeds to step S28, it is determined that defrosting is required, and the defrosting operation is started.

[0076] In Embodiment 2, a temperature sensor 2b is provided to measure the temperature of point C0 (or C1), and the control device 200 uses the measured temperature T to determine whether to perform defrosting. ２ｂ By using this method, the same effects as in Embodiment 1 can be obtained without directly estimating Gr1 and Gr2, which are the refrigerant circulation amounts at the transition point between each refrigerant temperature distribution pattern.

[0077] However, if it is structurally difficult to place the temperature sensor 2b right next to point C0 (or C1), the temperature sensor 2b can be placed at a location where the temperature difference of the refrigerant from point C0 (or C1) is within 10% of the saturation temperature fluctuation range of the refrigerant in the heat source side heat exchanger 2. By placing the temperature sensor in such a position, the temperature difference becomes negligible compared to the resolution and measurement error of the temperature sensor, making it possible to use it for control in the same way as when the temperature sensor is placed at point C0 (or C1).

[0078] Embodiment 3. Embodiment 3 is a configuration for efficiently performing the defrosting operation in Embodiment 1. For this reason, the operation of the refrigerant in the refrigeration cycle circuit 100 is the same as in Embodiment 1, so its explanation will be omitted, and the examples of Embodiment 3 will also be described only for the heat source side heat exchanger 2, similar to Embodiment 1.

[0079] Figure 14 is a schematic diagram showing a refrigerant circuit according to Embodiment 3. The refrigerant circuit shown in Figure 14 further includes a bridge circuit 6 in addition to the configuration of the refrigerant circuit shown in Figure 1. The bridge circuit 6 includes on-off valves 6A to 6D. The bridge circuit 6 is inserted between the ports P1 and P2, which are the two refrigerant inlets and outlets of the heat source side heat exchanger 2, and the expansion mechanism 4 and the four-way valve 5. By changing the settings of the bridge circuit 6, the direction in which the refrigerant flows to the heat source side heat exchanger 2 can be reversed.

[0080] The rest of the refrigerant circuit is the same as in Figure 1, so we will not repeat the explanation. In the bridge circuit 6, when the on-off valves 6A and 6B are open and the on-off valves 6C and 6D are closed, the refrigerant flow in the heat source side heat exchanger 2 is in the direction indicated by arrow F1, which points from port P1 to port P2. Also, in the bridge circuit 6, when the on-off valves 6A and 6B are closed and the on-off valves 6C and 6D are open, the refrigerant flow in the heat source side heat exchanger 2 is in the direction indicated by arrow F2, which points from port P2 to port P1. Figure 14 shows the four-way valve 5 and the bridge circuit 6 in a state where the refrigerant flows in the direction indicated by arrow F1.

[0081] As described in Embodiment 1, when a refrigerant having thermal glide is applied to a refrigeration cycle system, the location of frost formation in the heat source side heat exchanger 2, whether near the inlet or outlet, changes depending on the operating conditions.

[0082] If high-temperature refrigerant discharged from compressor 1 can be introduced into the frost-accumulating areas of heat exchanger 2 on the heat source side, the temperature difference between the frost and the refrigerant will increase, enabling efficient defrosting.

[0083] Figure 15 is a flowchart illustrating the determination process performed by the control device 200 in Embodiment 3.

[0084] First, in step S31, the control device 200 controls the temperature T detected by the temperature sensor 2a. ２ａ is the frosting judgment temperature T ｆｒｏ Determine whether it is lower than or equal to T. ２ａ ga T ｆｒｏ If it is lower than (YES in S31), the process proceeds to step S33.

[0085] Meanwhile, T ２ａ ga T ｆｒｏ In the above case (NO in S31), in step S32 the control device 200 will determine the temperature T detected by the temperature sensor 2b. ２ｂ is the frosting judgment temperature T ｆｒｏ Determine whether it is lower than or equal to T. ２ｂ ga T ｆｒｏ If it is lower than (YES in S32), the process proceeds to step S33.

[0086] Note, -２ｂ ga T ｆｒｏ If the above conditions are met (NO in S32), the control device 200 returns to step S31 and continues monitoring whether defrosting is necessary.

[0087] If the process proceeds to step S33, the control device 200 determines that defrosting is required, and in step S34, the temperature T ２ａ is temperature T ２ｂ Determine whether it is lower than or equal to.

[0088] Temperature T ２ａ is temperature T ２ｂ If the value is lower than (YES in S34), the control device 200 sets the bridge circuit 6 to have a refrigerant flow direction F1. Specifically, as shown in Figure 14, the control device 200 sets the on-off valves 6A and 6B to the open state and the on-off valves 6C and 6D to the closed state.

[0089] Also, temperature T ２ａ is temperature T ２ｂ If the above conditions are met (NO in S34), the control device 200 sets the bridge circuit 6 to the refrigerant flow direction F2. Specifically, contrary to Figure 14, the control device 200 sets the on-off valves 6C and 6D to the open state and the on-off valves 6A and 6B to the closed state.

[0090] After the refrigerant flow direction is determined in step S35 or S36, the control device 200 starts the defrosting operation.

[0091] According to Embodiment 3, the control device 200 determines the frost accumulation location from the temperatures measured by the temperature sensors 2a and 2b, and controls the bridge circuit to introduce the high-temperature refrigerant discharged from the compressor 1 to the location closest to the frost accumulation location, thereby shortening the defrosting operation time.

[0092] Embodiment 4. Embodiment 4 is a configuration for efficiently performing the defrosting operation in Embodiment 1. Since the operation of the refrigerant in the refrigeration cycle circuit 100 is the same as in Embodiment 1, the explanation will be omitted. The example of Embodiment 3 will also be explained only with respect to the heat source side heat exchanger 2, similar to Embodiment 1.

[0093] Figure 16 is a schematic diagram showing a refrigerant circuit according to Embodiment 4. The refrigerant circuit shown in Figure 16 further includes a solenoid valve 7 that opens and closes a bypass path, in addition to the configuration of the refrigerant circuit shown in Figure 1. By connecting the solenoid valve 7, the flow rate of the refrigerant in the heat source side heat exchanger 2 during defrosting operation can be partially changed.

[0094] As described in Embodiment 1, when a refrigerant having thermal glide is applied to a refrigeration cycle system, the location of frost formation in the heat source side heat exchanger 2—whether near the inlet or outlet—varies depending on the operating conditions. For example, the area near point C1 between the inlet and outlet may be a place where frost is likely to form.

[0095] Figure 17 shows the flow of refrigerant in the heat source side heat exchanger 2 of Embodiment 4 during defrosting operation. During defrosting operation, the refrigerant flows in the opposite direction to that shown in Figure 9.

[0096] By opening the solenoid valve 7 during defrosting operation, high-temperature refrigerant discharged from the compressor 1 can be allowed to flow into the frost-covered areas of the heat source side heat exchanger 2 from point C1, thereby increasing the temperature difference between the frost and the refrigerant, and enabling efficient defrosting operation.

[0097] Figure 18 is a flowchart illustrating the determination process performed by the control device 200 in Embodiment 4.

[0098] First, in step S41, the control device 200 controls the temperature T detected by the temperature sensor 2a. ２ａ is the frosting judgment temperature T ｆｒｏ Determine whether it is lower than or equal to T. ２ａ ga T ｆｒｏ If the result is lower than (YES in S41), the process proceeds to step S43.

[0099] Meanwhile, T ２ａ ga T ｆｒｏ In the above case (NO in S41), in step S42 the control device 200 will determine the temperature T detected by the temperature sensor 2b. ２ｂ is the frosting judgment temperature T ｆｒｏ Determine whether it is lower than or equal to T. ２ｂ ga T ｆｒｏ If the result is lower than (YES in S42), the process proceeds to step S43.

[0100] Furthermore, T ２ｂ is T ｆｒｏ If the temperature is equal to or higher than the above (NO in S42), the control device 200 returns the process to step S41 again and continues to monitor whether defrosting is necessary.

[0101] When the process proceeds to step S43, the control device 200 determines that defrosting is required, and in step S44, the temperature T ２ａ is the temperature T ２ｂ to determine whether it is lower than the temperature T

[0102] Temperature T ２ａ is the temperature T ２ｂ When the temperature is lower than the above (YES in S44), the control device 200 opens the electromagnetic valve 7. Further, when the temperature T ２ａ is the temperature T ２ｂ When the temperature is equal to or higher than the above (NO in S44), the control device 200 closes the electromagnetic valve 7.

[0103] After the state of the electromagnetic valve 7 is determined in step S45 or S46, the control device 200 starts the defrosting operation.

[0104] As described above, the control device 200 determines the frost formation location from the temperatures measured by the temperature sensors 2a and 2b, and when it determines that the frost formation location is not between port P2 and point C1, it opens the electromagnetic valve 7 in the bypass path. As a result, the high-temperature refrigerant discharged from the compressor 1 is directly introduced to the frost formation location, so the defrosting operation time can be shortened.

[0105] [Summary] The present disclosure will be summarized with reference to the drawings again.

[0106] (Section 1) This disclosure relates to a refrigeration cycle device 300. The refrigeration cycle device 300 includes at least a compressor 1, a condenser (3), and an evaporator (2), a refrigeration cycle circuit (100) filled with refrigerant, at least two temperature sensors 2a, 2b attached to the evaporator (2) for measuring the temperature of the refrigerant passing through the evaporator (2), and a control device 200 that determines whether to start or end a defrosting operation of the evaporator (2) or to change the frost location of the evaporator (2) by changing the discharge amount of the compressor 1, based on the temperatures measured by the at least two temperature sensors 2a, 2b. The refrigerant has the characteristic of temperature glide, which changes temperature under constant pressure in a two-phase state.

[0107] (Section 2) In the refrigeration cycle device 300 described in Section 1, when the refrigeration cycle circuit (100) is defined as the evaporator refrigerant flow path between the refrigerant inlet and refrigerant outlet of the evaporator (2), at least two temperature sensors 2a and 2b are arranged at least two locations among the refrigerant inlet of the evaporator (2), the refrigerant outlet of the evaporator (2), and the observation points, where the observation points are defined as locations in the evaporator refrigerant flow path where the number of passes of the refrigerant piping changes, locations where the diameter of the refrigerant piping changes, locations where the pressure of the flowing refrigerant changes due to the amount of bending or flow path width of the refrigerant piping, or locations where the device branches to a bypass circuit.

[0108] (Clause 3) In the refrigeration cycle device 300 described in paragraph 2, at least one of the two temperature sensors 2a and 2b is placed at the observation point.

[0109] (Section 4) The refrigeration cycle device 300 described in any one of Sections 1 to 3 further comprises a flow path switching device (6) arranged in the refrigeration cycle circuit (100) and configured to reverse the direction of refrigerant flow in the evaporator (2). When defrosting the frosted heat exchanger, which is the evaporator (2), the control device 200 is configured to change the direction of refrigerant flow in the evaporator (2) by the flow path switching device (6) based on the measured temperatures of at least two temperature sensors 2a and 2b.

[0110] (Article 5) In the refrigeration cycle device 300 described in any one of paragraphs 1 to 3, the control device 200 is configured to control the amount of refrigerant discharged from the compressor 1 such that the temperatures of at least two temperature sensors 2a and 2b do not both fall below the frosting temperature.

[0111] (Section 6) The refrigeration cycle device 300 described in any one of Sections 1 to 3 further comprises a bypass passage arranged in the refrigeration cycle circuit (100) and configured to inject refrigerant from the compressor 1 into the intermediate portion of the refrigerant flow path of the evaporator (2), and an on-off valve (7) provided in the bypass passage. When defrosting the frosted heat exchanger, which is the evaporator (2), the control device 200 is configured to control the on-off valve (7) based on the measured temperatures of at least two temperature sensors 2a and 2b.

[0112] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope of the claims are intended to be included.

[0113] 1 Compressor, 2 Heat source side heat exchanger, 2a, 2b Temperature sensors, 3 Utilization side heat exchanger, 4 Expansion mechanism, 5 Four-way valve, 6 Bridge circuit, 6A, 6B, 6C, 6D On / off valves, 7 Solenoid valve, 100 Refrigeration cycle circuit, 200 Control device, 201 CPU, 202 Memory, 300 Refrigeration cycle device, P1, P2 Ports.

Claims

1. A refrigeration cycle device comprising: a refrigeration cycle circuit filled with a refrigerant, including at least a compressor, a condenser, and an evaporator; at least two temperature sensors attached to the evaporator for measuring the temperature of the refrigerant passing through the evaporator; and a control device that determines, based on the temperatures measured by the at least two temperature sensors, whether to start or end a defrosting operation of the evaporator or to change the location of frost on the evaporator by changing the discharge amount of the compressor, wherein the refrigerant has the characteristic of temperature glide, where the temperature changes under constant pressure in a two-phase state.

2. In the refrigeration cycle circuit, when the section between the refrigerant inlet and refrigerant outlet of the evaporator is defined as the evaporator refrigerant flow path, observation points are defined as locations in the evaporator refrigerant flow path where the number of passes of the refrigerant piping changes, locations where the diameter of the refrigerant piping changes, locations where the pressure of the flowing refrigerant changes due to the amount of bending or flow path width of the refrigerant piping, or locations where a bypass circuit is branched, and at least two temperature sensors are respectively arranged at at least two locations among the refrigerant inlet of the evaporator, the refrigerant outlet of the evaporator, and the observation points.

3. The refrigeration cycle apparatus according to claim 2, wherein one of the at least two temperature sensors is located at the observation point.

4. The refrigeration cycle apparatus according to any one of claims 1 to 3, further comprising a flow path switching device arranged in the refrigeration cycle circuit and configured to reverse the flow direction of the refrigerant in the evaporator, wherein when defrosting a frosted heat exchanger which is the evaporator, the control device is configured to change the flow direction of the refrigerant in the evaporator using the flow path switching device based on the temperatures measured by the at least two temperature sensors.

5. The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein the control device is configured to control the amount of refrigerant discharged from the compressor so that the temperatures of at least two temperature sensors do not both fall below the frost temperature.

6. The refrigeration cycle apparatus according to any one of claims 1 to 3, further comprising: a bypass passage arranged in the refrigeration cycle circuit and configured to inject refrigerant from the compressor into an intermediate portion of the refrigerant passage of the evaporator; and an on-off valve provided in the bypass passage, wherein when defrosting the frosted heat exchanger which is the evaporator, the control device is configured to control the on-off valve based on the measured temperatures of the at least two temperature sensors.

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