JP2019100638A - Expansion valve control sensor and refrigeration system using the same - Google Patents

Abstract

To save energy for a refrigeration system by optimally controlling an expansion valve, in a refrigeration system having limitation in refrigerant amount and heat radiation capability of a condenser.SOLUTION: An expansion valve control sensor includes: a micro resistance 20; an upstream temperature sensor 21 for detecting piping temperature on an upstream side of the micro resistance 20; a downstream temperature sensor 22 for detecting piping temperature on a downstream side of the micro resistance 20. An expansion valve 14 is controlled so as to maintain a state of an outlet of a condenser 12 substantially constant using the expansion valve control sensor 23 for detecting a temperature difference between the upstream temperature sensor 21 and the downstream temperature sensor 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sensor for controlling an expansion valve that varies a throttle amount, and a refrigeration system equipped with the same.

  From the viewpoint of energy saving, there is a refrigeration system equipped with an expansion valve that can change the throttle amount.

  Hereinafter, a conventional refrigeration system will be described with reference to the drawings.

  FIG. 4 is a schematic view of a conventional refrigeration system, and FIG. 5 is a view showing a control method of an expansion valve of the conventional refrigeration system.

  In FIG. 4, the refrigeration system 40 includes a compressor 41, a condenser 42, a receiver 43, an expansion valve 44, a capillary tube 45, an evaporator 46, a suction pipe 47, an internal heat exchange unit 48, and a suction pipe temperature sensor 49.

  Here, the receiver 43 stores the refrigerant circulating in the refrigeration system 40 in a liquid state, and when the throttling of the expansion valve 44 is changed, the amount of liquid refrigerant in the receiver 43 fluctuates. And the function of maintaining the degree of subcooling of the refrigerant flowing into the expansion valve 44 substantially constant while maintaining the amount of refrigerant inside the evaporator 46 properly.

  Further, by arranging the expansion valve 44 and the capillary tube 45 in series to constitute the throttling of the refrigeration system 40, it is possible to realize the internal heat exchange section 48 which exchanges heat between the capillary tube 45 and the suction pipe 47. The enthalpy of the low temperature refrigerant circulating in the suction pipe 47 can be recovered to improve the efficiency of the refrigeration system 40.

  Further, the suction pipe temperature sensor 49 detects the temperature of the suction pipe 47 after passing through the internal heat exchange unit 48, and based on the temperature detected by the suction pipe temperature sensor 49, the throttling amount of the expansion valve 44 is detected. It can be variable.

  The operation of the conventional refrigeration system configured as described above will be described below.

  When the refrigeration system 40 is operated and the cooling operation is performed, the compressor 41 is operated. The refrigerant compressed by the compressor 41 dissipates heat by the condenser 42 and is condensed and stored in the receiver 43. Then, the liquid refrigerant remaining in the receiver 43 is depressurized by the expansion valve 44 and the capillary tube 45, and is then supplied to the evaporator 46 for evaporation, and is returned to the compressor 41 via the suction pipe 47. At this time, cooling is performed using cold heat generated by the evaporator 46.

  Here, when the temperature of an object (not shown) to be cooled using the refrigeration system 40 decreases and approaches a stable state, cold heat supplied from the evaporator 46 becomes excessive and can not evaporate in the suction pipe 47 The liquid refrigerant mixes, and the temperature of the suction pipe 47 decreases. At this time, even after passing through the internal heat exchange section 48 which recovers the enthalpy of the low temperature refrigerant flowing back in the suction pipe 47, the temperature of the suction pipe 47 does not rise sufficiently and approaches the temperature of the evaporator 46.

  As a result, the cold heat generated by the evaporator 46 which is not utilized is returned to the compressor 41, whereby the efficiency of the refrigeration system 40 is reduced, and when this state continues, the liquid refrigerant is returned and the compressor 41 is There is a concern that durability may be reduced. Therefore, in order to avoid the efficiency decrease of the refrigeration system 40 and the durability decrease of the compressor 41, the throttling amount of the expansion valve 44 is controlled based on the temperature detected by the suction pipe temperature sensor 49.

  Next, a control method of the expansion valve of the conventional refrigeration system will be described based on FIG.

  The horizontal axis in FIG. 5 is the pressure loss generated in accordance with the amount of throttling of the expansion valve 44, and the vertical axis is the temperature R of the suction pipe 47 detected by the suction pipe temperature sensor 49. As described above, the temperature of the object (not shown) to be cooled using the refrigeration system 40 decreases and approaches a stable state, and the cold heat supplied from the evaporator 46 becomes excessive and the temperature of the suction pipe 47 decreases. When the pressure falls below R1, the throttling amount of the expansion valve 44 is increased by a predetermined amount. As a result, the evaporation temperature of the evaporator 46 decreases, the refrigerant circulation amount is reduced, and the refrigeration capacity supplied from the evaporator 46 is reduced, and the liquid refrigerant flowing out to the suction pipe 47 is recovered as surplus refrigerant in the receiver 43 By doing this, the temperature of the suction pipe 47 is raised.

  On the other hand, when the temperature of the suction pipe 47 rises and exceeds R2, the throttling amount of the expansion valve 44 is decreased by a predetermined amount. As a result, the evaporation temperature of the evaporator 46 rises, the refrigerant circulation amount is increased, and the refrigeration capacity supplied from the evaporator 46 is increased, and the surplus refrigerant collected in the receiver 43 is supplied to the evaporator 46. The temperature of the suction pipe 47 is lowered.

  Thus, by controlling the throttling amount of the expansion valve 44, the temperature R of the suction pipe 47 can be maintained between R1 and R2, and the efficiency reduction of the refrigeration system 40 and the durability reduction of the compressor 41 are avoided. can do.

JP-A-5-196321

  However, in the configuration of the conventional refrigeration system, in order to control the throttling amount of the expansion valve 44 based on the output of the suction pipe temperature sensor 49, a receiver that automatically adjusts the surplus refrigerant amount that fluctuates with the throttling amount of the expansion valve 44 43 were required. As a result, the amount of refrigerant necessary to hold the surplus refrigerant is always required in the receiver 43, and a condenser 42 having a heat dissipating ability to keep the receiver 43 at a predetermined amount of subcooling is required. Therefore, it has been difficult to use the expansion valve in a refrigeration system having a limited amount of refrigerant such as a household refrigerator using a flammable refrigerant.

  In addition, in a refrigeration system whose heat dissipation capacity changes significantly depending on the environmental conditions, such as a household refrigerator that uses a condenser that dissipates heat by natural convection from the outer shell of the casing, the condenser outlet can not be maintained at a predetermined degree of subcooling. It was difficult to use the expansion valve.

  Therefore, an object of the present invention is to achieve energy saving of the refrigeration system by optimum control of the expansion valve using the expansion valve even in the refrigeration system having a restriction on the amount of refrigerant and the heat radiation capacity of the condenser.

  In order to achieve this object, the present invention comprises a minute resistance, an upstream temperature sensor for detecting a piping temperature upstream of the small resistance, and a downstream temperature sensor for detecting a piping temperature downstream of the small resistance. And detecting a temperature difference between the upstream temperature sensor and the downstream temperature sensor.

  The refrigeration system equipped with the expansion valve control sensor of the present invention can achieve energy saving of the refrigeration system by the optimum control of the expansion valve.

Schematic diagram of the refrigeration system in the first embodiment of the present invention The figure which showed the control method of the expansion valve of the refrigeration system in Embodiment 1 of this invention. The figure which showed the correlation of the output of the expansion valve control sensor of the refrigeration system in Embodiment 1 of this invention, and a refrigerant | coolant flow velocity Schematic of conventional refrigeration system Diagram showing control method of expansion valve of conventional refrigeration system

  The first invention has a minute resistance, an upstream temperature sensor for detecting a piping temperature upstream of the small resistance, and a downstream temperature sensor for detecting a piping temperature downstream of the small resistance, the upstream temperature The expansion valve control sensor detects a temperature difference between the sensor and the downstream temperature sensor.

  As a result, it is possible to relatively detect changes in the flow rate and dryness of the refrigerant passing through the minute resistance, and as a result, energy saving of the refrigeration system can be achieved.

  A second invention has at least a condenser and an expansion valve, and the expansion valve control sensor of the first invention is disposed downstream of the condenser, and the expansion valve is downstream of the expansion valve control sensor. A refrigeration system characterized in that

  As a result, the expansion valve can be controlled to keep the state of the condenser outlet substantially constant, and energy saving of the refrigeration system can be achieved.

  A third invention according to the second invention comprises at least a compressor, a condenser, an expansion valve, and a capillary tube, and a capillary tube is disposed downstream of the expansion valve, and the expansion valve is throttled. After activating the compressor with the amount minimized, the expansion valve is controlled to be gradually narrowed so as to bring the temperature difference obtained from the expansion valve control sensor close to a predetermined value.

  As a result, the target value of the temperature difference obtained from the expansion valve control sensor can be relatively determined based on the state of the condenser outlet predicted when the expansion valve throttle amount is minimized, and more optimally The expansion valve can be controlled, and as a result, energy saving of the refrigeration system can be achieved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals are given to the same components as those of the conventional example, and the detailed description thereof will be omitted. The present invention is not limited by the embodiment.

Embodiment 1
FIG. 1 is a schematic view of a refrigeration system according to a first embodiment of the present invention, FIG. 2 is a view showing a method of controlling an expansion valve of the refrigeration system according to the first embodiment, and FIG. 3 is a refrigeration system according to the first embodiment It is the figure which showed the correlation of the output of the expansion valve control sensor of 1, and a refrigerant | coolant flow velocity.

  In FIG. 1, the refrigeration system 10 includes a compressor 11, a condenser 12, a dryer 13, an expansion valve 14, a capillary tube 15, an evaporator 16, an accumulator 17, a suction pipe 18, and an internal heat exchange unit 19. In addition, the refrigeration system 10 includes an expansion valve control sensor 23 including a minute resistor 20, an upstream temperature sensor 21 and a downstream temperature sensor 22.

  Here, the dryer 13 is for drying the refrigerant circulating in the refrigeration system 10, and is disposed downstream of the condenser 12 in order to contact the liquid refrigerant efficiently.

  In addition, the accumulator 17 stores surplus refrigerant in a stable state, and is disposed downstream of the evaporator 16 in order to maintain the temperature substantially the same as that of the evaporator 16. When the temperature of an object (not shown) to be cooled using the refrigeration system 10 rises, the amount of surplus refrigerant stored in the accumulator 17 decreases and the amount of refrigerant circulating in the refrigeration system 10 increases, thereby increasing the refrigeration capacity. increase. Generally, in a refrigeration system whose heat dissipation capacity changes significantly depending on the environmental conditions, such as a household refrigerator that dissipates heat from the enclosure of the casing by natural convection, excess receiver can not be stored on the high pressure side of the refrigeration system. As in the first embodiment, surplus refrigerant is stored on the low pressure side of the refrigeration system using an accumulator. Moreover, since the surplus refrigerant amount stored in the accumulator is about 10 to 30% of the total refrigerant amount in the refrigeration system, and the function of adjusting the refrigeration capacity can be obtained with a relatively small amount, it is effective to suppress the total refrigerant amount. It is.

  Further, by arranging the expansion valve 14 and the capillary tube 15 in series to constitute the throttling of the refrigeration system 10, it is possible to realize the internal heat exchange unit 19 which exchanges heat between the capillary tube 15 and the suction pipe 18 The enthalpy of the low temperature refrigerant flowing back in the suction pipe 18 can be recovered to improve the efficiency of the refrigeration system 10.

  The minute resistance 20 constituting the expansion valve control sensor 23 is a small diameter tube having a length of 250 mm, and the resistance equivalent to about 5% of the total resistance of the minute resistance 20, the expansion valve 14 and the capillary tube 15 arranged in series. Have. The ratio of the minute resistance 20 to the total resistance is desirably 1 to 20%. If it is less than 1%, it becomes difficult to detect a change in the state of the refrigerant flowing inside. If it exceeds 20%, the heat exchange of the internal heat exchange 19 is insufficient, and the efficiency of the refrigeration system is reduced. Here, the ratio of the minute resistance 20 to the total resistance is shown by the ratio of the length when each resistance is replaced with a capillary tube of the same inner diameter.

  Further, the upstream temperature sensor 21 and the downstream temperature sensor 22 constituting the expansion valve control sensor 23 detect the pipe temperature on the upstream side and the pipe temperature on the downstream side of the minute resistor 20, respectively. The difference between the temperatures detected by the upstream temperature sensor 21 and the downstream temperature sensor 22 changes in accordance with the state change of the flowing refrigerant. Therefore, the refrigeration system 10 can be controlled to a predetermined state by varying the throttling amount of the expansion valve 14 based on the difference between the temperatures detected by the upstream temperature sensor 21 and the downstream temperature sensor 22.

  The operation of the refrigeration system according to the first embodiment of the present invention configured as described above will be described below.

  When the refrigeration system 10 is operated to perform the cooling operation, the compressor 11 is operated with the throttling amount of the expansion valve 14 minimized. The refrigerant compressed by the compressor 11 dissipates heat by the condenser 12 and is then condensed by the dryer 13. Then, after passing through the expansion valve control sensor 23, the pressure is reduced by the expansion valve 14 and the capillary tube 15, and then supplied to the evaporator 16 for evaporation and refluxing to the compressor 11 through the suction pipe 18. At this time, cooling is performed using cold heat generated by the evaporator 16.

  Here, in a state where the expansion amount of expansion valve 14 is minimized and compressor 11 is operated, when the temperature of an object (not shown) decreases and approaches a stable state, the refrigerant at the outlet of condenser 12 is in a two-phase state (Desirably, the dryness is 3 to 10% by weight). This is because the temperature of the object to be cooled (not shown) rises, the amount of surplus refrigerant stored in the accumulator 17 decreases, and the amount of refrigerant circulation in the refrigeration system 10 increases, the outlet of the condenser 12 This is because the total resistance of the minute resistor 20, the expansion valve 14 and the capillary tube 15 arranged in series and the total amount of refrigerant in the refrigeration system 10 are designed so that the refrigerant does not become subcooled. Generally, in a refrigeration system whose heat dissipation capacity changes significantly depending on the environmental conditions such as a household refrigerator that dissipates heat from the outer shell of the casing by natural convection, if the refrigerant at the outlet of the condenser is designed to be supercooled, the heat dissipation capacity is When it increases, almost all the refrigerant in the refrigeration system stays in the condenser, causing a concern that the refrigerant circulation amount may be abnormally reduced. In addition, there is a concern that the durability of the compressor may be reduced by the excess refrigerant which could not be condensed by the condenser when the heat radiation capacity is reduced due to environmental conditions, because the accumulator can not be stored enough and recirculated from the suction pipe to the compressor. It occurs.

  Then, the temperature difference of the small resistance 20 detected by the expansion valve control sensor 23 changes a predetermined value or a predetermined amount as compared with the stable state in which the expansion amount of the expansion valve 14 is kept at a minimum. Control the amount of aperture. As a result, the dryness of the refrigerant at the outlet of the condenser 12 is reduced, so that the refrigeration effect can be increased and the efficiency of the refrigeration system 10 can be improved.

  Next, a method of controlling the expansion valve of the refrigeration system according to the first embodiment of the present invention will be described based on FIGS. 2 and 3.

  The horizontal axis of FIG. 2 is a pressure loss generated according to the amount of restriction of the expansion valve 14, and the vertical axis is a temperature difference S before and after the minute resistance 20 detected by the expansion valve control sensor 23. As described above, when the temperature of an object (not shown) to be cooled using the refrigeration system 10 decreases and approaches a stable state while the compressor 11 is operated with the amount of throttling of the expansion valve 14 minimized. The refrigerant at the outlet of the condenser 12 is in a two-phase state. At this time, the output of the expansion valve control sensor 23 indicates S0. Then, the throttling amount of the expansion valve 14 is increased so that the output of the expansion valve control sensor 23 falls below S2. As a result, the dryness of the refrigerant at the outlet of the condenser 12 is reduced, so that the refrigeration effect can be increased and the efficiency of the refrigeration system 10 can be improved.

  On the other hand, when the dryness of the refrigerant at the outlet of the condenser 12 continues to decrease and the output of the expansion valve control sensor 23 falls below S1, the throttling amount of the expansion valve 14 is reduced. As a result, the output of the expansion valve control sensor 23 can be stabilized in the state of S1 to S2. The lower limit value S1 is provided for the output of the expansion valve control sensor 23 because if the expansion valve 14 is throttled too much, the refrigerant at the outlet of the condenser 12 becomes supercooled and almost all the refrigerant in the refrigeration system 10 It is because there is a concern that the refrigerant circulation amount is abnormally reduced due to stagnation.

  The horizontal axis in FIG. 3 is the temperature difference S before and after the minute resistance 20 detected by the expansion valve control sensor 23 which is the same as the vertical axis in FIG. 2. The vertical axis in FIG. It is the flow velocity V. As described above, when the throttling amount of the expansion valve 14 is increased from the state where the output of the expansion valve control sensor 23 indicates S0, the dryness of the refrigerant at the outlet of the condenser 12 decreases and passes through the minute resistance 20 As a result, the output of the expansion valve control sensor 23 decreases from S0 to S2. Similarly, when the expansion amount of the expansion valve 14 is adjusted to stabilize the output of the expansion valve control sensor 23 in the state of S1 to S2, the dryness of the refrigerant at the outlet of the condenser 12 is near zero (desirably, the dryness is desirable It is stable at 0 to 1% by weight, and the flow velocity V of the refrigerant stabilizes near the minimum value. This is because the refrigerant circulation amount is substantially constant when the refrigeration system 10 is in a stable state, and therefore, when the refrigerant at the outlet of the condenser 12 is in the liquid phase, the flow velocity V of the refrigerant passing through the minute resistance 20 is substantially minimized As the dryness of the refrigerant at the outlet of the vessel 12 increases, the flow velocity V of the refrigerant passing through the minute resistance 20 increases. Generally, the specific volume of the gas phase to the liquid phase is as large as about 50 times, so the amount of change in the flow velocity V of the refrigerant passing through the minute resistance 20 with a dryness of 0 to 10% by weight is large. It can be said that it is easy to detect the state of the outlet refrigerant of the condenser 12 by the valve control sensor 23.

  Thus, by controlling the throttling amount of the expansion valve 14 according to the output of the expansion valve control sensor 23, the dryness of the refrigerant at the outlet of the condenser 12 is near zero (desirably, the dryness is 0 to 1% by weight). The stability can be enhanced and the refrigeration effect can be increased to improve the efficiency of the refrigeration system 10.

  As described above, the refrigeration system according to the first embodiment uses the expansion valve control sensor including the minute resistance and the temperature sensor for detecting the temperature difference between the small resistance and the expansion so as to keep the state of the condenser outlet substantially constant. By controlling the valve, optimum control of the expansion valve can be performed in the refrigeration system having no receiver at the condenser outlet, energy saving of the refrigeration system can be achieved, and deterioration in the durability of the compressor can be avoided. .

  In the first embodiment, the throttling amount of the expansion valve 14 is adjusted so that the output of the expansion valve control sensor 23 becomes a predetermined value from S1 to S2. The throttling amount of the expansion valve 14 may be adjusted so as to change by a predetermined amount as compared with. The dryness of the refrigerant at the outlet of the condenser 12 in the stable state and the output of the expansion valve control sensor 23 are assumed in advance from environmental conditions such as the ambient temperature of the refrigeration system 10 and operating conditions of the compressor 11 such as condensing temperature and evaporation temperature. If it is possible, it is possible to estimate the optimum dryness of the refrigerant at the outlet of the condenser 12 and the output of the expansion valve control sensor 23 under the conditions, and adjust the expansion valve 14 more accurately. In general, the refrigeration system is designed so that the total resistance and the total refrigerant quantity of the refrigeration system are designed so that the refrigerant at the outlet of the condenser does not become supercooled under the environmental conditions and operating conditions assumed in advance. It is possible to assume the dryness of the refrigerant at the outlet of the condenser if it is in a stable state kept to a minimum.

  In the first embodiment, although the minute resistance 20 consisting of a small diameter tube having a length of 250 mm is used, the minute resistance 20 which is approximately 5% of the total resistance of the minute resistance 20, the expansion valve 14 and the capillary tube 15 arranged in series is used. If the ratio of the minute resistance 20 to the total resistance is 1 to 20%, the same effect can be obtained even if the minute resistance 20 is configured by a small diameter tube or a minute orifice.

  As described above, the refrigeration system according to the present invention includes a refrigeration system whose heat dissipating capacity changes greatly depending on the environmental conditions such as a household refrigerator which dissipates heat by natural convection from the outer shell of the casing, and a flammable refrigerant which has a limited amount of refrigerant The expansion valve can also be used in a refrigeration system using the above, and the expansion valve can be optimally controlled, so that it can be applied to refrigeration and refrigeration applied goods.

DESCRIPTION OF SYMBOLS 10 Refrigeration system 11 Compressor 12 Condenser 13 Dryer 14 Expansion valve 15 Capillary tube 16 Evaporator 18 Intake pipe 19 Internal heat exchange part 20 Small resistance 21 Upstream temperature sensor 22 Downstream temperature sensor 23 Expansion valve control sensor

Claims (3)

The upstream temperature sensor and the downstream temperature sensor, comprising: a minute resistance; an upstream temperature sensor for detecting a pipe temperature upstream of the minute resistance; and a downstream temperature sensor for detecting a pipe temperature downstream of the minute resistance An expansion valve control sensor characterized by detecting a temperature difference between the two. It has at least a condenser and an expansion valve, and the expansion valve control sensor according to claim 1 is disposed downstream of the condenser, and the expansion valve is disposed downstream of the expansion valve control sensor. Characteristic refrigeration system. At least a compressor, a condenser, an expansion valve, and a capillary tube, and a capillary tube is disposed downstream of the expansion valve, and the expansion valve is fully opened to start the compressor, and then the expansion valve The refrigeration system according to claim 2, wherein the expansion valve is controlled to be gradually narrowed so that a temperature difference obtained from a control sensor approaches a predetermined value.

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