JP6021954B2 - Liquid level detection device and refrigeration air conditioner - Google Patents

Description

The present invention relates to a liquid level detection device and a refrigeration air conditioner that specify a liquid level position in a container.

  2. Description of the Related Art Conventionally, there is a liquid level detection device that can detect the position of a liquid level inside a container by attaching a sensor to the outer surface of the container containing liquid (for example, see Patent Document 1).

  The liquid level detection device described in Patent Document 1 has a strip-shaped sensor body configured by laminating a temperature measurement layer for measuring the temperature of the container surface and a heating layer for heating the container. . The sensor body is used by being attached to the outer surface of the container such that the longitudinal direction is the vertical direction of the container and the temperature measurement layer is on the container side.

  The heat of the heating layer reaches the surface of the container through the temperature measurement layer, and the portion of the temperature measurement layer facing the liquid in the container and the container due to the difference in the heat transfer coefficient of the gas / liquid inside the container There is a temperature difference between the portion facing the gas inside. In other words, the container surface temperature of the part where the liquid with a high heat transfer coefficient is located is close to the temperature of the liquid refrigerant inside the container, but the container surface temperature of the part where the gas with a low heat transfer coefficient is located is outside the container. It becomes close to the temperature (heating temperature of the heating layer).

  Therefore, in Patent Document 1, using this temperature difference, that is, comparing the temperatures in the vertical direction of the temperature measurement layer when heated from the outside, the gas part is compared to a relatively high temperature, and the liquid temperature if relatively low. The liquid level is detected as a part.

JP 2008-39726 A (first page, FIG. 1)

  However, when the liquid level inside the container is flowing due to the fluid flowing into and out of the container, the heat transfer coefficient inside the container changes compared to the case where the liquid inside the container is stationary. . Since the change in the heat transfer coefficient inside the container also affects the container surface temperature, the method of Patent Document 1 for specifying the liquid level position without considering the change in the heat transfer coefficient inside the container specifies the liquid level position. There was a problem that I could not.

This invention is made in view of such a point, and provides the liquid level detection apparatus and refrigeration air conditioning apparatus which can pinpoint the liquid level position of the liquid currently flowing in the container from the container exterior. Objective.

Fluid level sensing apparatus according to the present invention, in height from each other located on the surface of the container liquid level detection object is placed in the different, a plurality of sensors for measuring the temperature of the installation place by a temperature measuring element, the container The liquid level detection part which specifies the liquid level position in the container in the state where the fluid flows in / out as the position of the sensor with the lowest measured value among the plurality of sensors is provided.

  According to the liquid level detection device of the present invention, the liquid level position of the liquid flowing in the container can be specified from the outside of the container.

It is the schematic which shows the state which installed 1 A of liquid level detection apparatuses which concern on one embodiment of this invention in the container 9 which is an element apparatus of a refrigerating air conditioning apparatus. It is the schematic which shows schematic structure of 1 A of liquid level detection apparatuses of FIG. It is a block diagram which shows roughly the electric structure of the control measuring device 20 which comprises the liquid level detection apparatus 1A of FIG. It is a figure which shows the relationship between the fluid velocity and heat transfer rate of air, water, a liquid refrigerant (R410A, 20 degreeC), and a gas refrigerant (R410A, 20 degreeC). It is a figure which shows the measured value (container surface temperature) of each sensor 10 after the heating body 102 heating of the liquid level detection apparatus 1A in case the refrigeration air conditioner has stopped. It is the figure which estimated the flow of the fluid inside a container in the state of FIG. It is a figure which shows the measured value (container surface temperature) of each sensor 10 after the heating of each sensor 10 of the liquid level detection apparatus 1A when the refrigeration air conditioner is operating. It is the figure which estimated the flow of the fluid inside a container in the state of FIG. It is a figure which shows the relationship between a liquid fluid velocity and height. It is a figure which shows the relationship between the sensor measured value (container surface temperature) after the heating by the heating body 102 of each sensor 10 in case the refrigeration air conditioner is operating, and the container height. It is a figure which shows the relationship between the measured value after the heating body 102 of each sensor 10 when the refrigerating and air-conditioning apparatus is operating, and the container height. It is the flowchart which showed the flow of the process in the case of the liquid level detection of 1 A of liquid level detection apparatuses which concern on one embodiment of this invention.

  Hereinafter, the configuration, installation method, liquid level detection principle, and gas-liquid determination method of a liquid level detection device according to an embodiment of the present invention will be described based on the drawings. In the following embodiments, a description will be given based on an example in which a container that is provided on the low pressure side and stores a refrigerant is used as a measurement target as an element part in a refrigeration air conditioner. In addition, in the following drawings including FIG. 1, the relationship of the size of each component may be different from the actual one. Further, in the following drawings including FIG. 1, the same reference numerals denote the same or equivalent parts, and this is common throughout the entire specification. Furthermore, the forms of the constituent elements shown in the entire specification are merely examples, and are not limited to these descriptions.

  FIG. 1 is a schematic diagram showing a state in which a liquid level detection device 1A according to an embodiment of the present invention is installed in a container 9 which is an element device of a refrigeration air conditioner. FIG. 2 is a schematic diagram showing a schematic configuration of the liquid level detection device 1A of FIG. 1A of liquid level detection apparatuses are demonstrated based on FIG. 1, FIG. In addition, the arrow in FIG. 1 has shown the flow direction of the refrigerant | coolant.

<Container for liquid level detection>
First, the container 9 as a liquid level detection target will be described with reference to FIG. As described above, the container 9 is one component part of the refrigeration air conditioner. The refrigerating and air-conditioning apparatus is an apparatus that includes at least a compressor, a condenser (radiator), a throttling device, and an evaporator (all not shown) in addition to the container 9, and a refrigerant circuit in which the refrigerant circulates sequentially. is there. The container 9 is installed on the low pressure side of the refrigeration air conditioner (portion from the throttle device to the compressor through the evaporator). There are two purposes for installing the container 9.

  First, the first point of the purpose of installing the container 9 is to store lubricating oil for compressor lubrication. This is because a compressor is installed downstream of the container 9, and a lubricating oil is necessary for the operation of the compressor, so that a certain amount of lubricating oil is returned to the compressor by accumulating oil in the container 9 on the upstream side of the compressor. It is.

  The second purpose of the installation of the container 9 is to store the excess liquid refrigerant of the refrigeration air conditioner. In the refrigeration air conditioner, the amount of refrigerant required for the refrigeration air conditioner varies depending on the operating state and the control state. For this reason, normally, the amount of refrigerant when it is most needed is filled in the refrigeration air conditioner. For this reason, when the amount of refrigerant required is reduced depending on the operation state and the control state, the liquid refrigerant is left. This surplus refrigerant is called surplus liquid refrigerant, and the container 9 has a role of storing this surplus liquid refrigerant.

  Further, the container 9 is made of iron for pressure resistance, and has a wall thickness of 3 to 4 mm, for example, and the internal liquid level cannot be visualized from the outside. Furthermore, the container 9 is generally provided with a cylindrical main body. That is, the outer surface of the container 9 is a cylindrical surface.

  As shown in FIG. 1, the container 9 is provided with two pipes, an inlet pipe 9a and an outlet pipe 9b. The inlet pipe 9a and the outlet pipe 9b are arranged in the upper part of the container 9 so as to penetrate the inside and outside of the container 9 in the vertical direction. The inlet pipe 9 a allows the refrigerant to flow into the container 9. The outlet pipe 9 b allows the refrigerant to flow out of the container 9.

  The outlet pipe 9b as a whole has a substantially J shape when viewed from the front, and an oil return hole 9c is formed at the lowermost portion of the curved portion of the J shape, and the upper end protrudes from the upper portion of the container 9 and is connected to the compressor. . Moreover, the front-end | tip located in the inside of the container 9 of the exit piping 9b becomes the suction port 9d which attracts | sucks the refrigerant | coolant which exists in the container 9. FIG. This structure is because a certain amount of lubricating oil needs to be returned to the compressor. In the container 9 configured in this way, the pressure inside the outlet pipe 9b decreases due to the suction flow rate of the gas refrigerant sucked from the suction port 9d, and the oil is sucked from the oil return hole 9c and returned to the compressor. It has become so.

<Configuration of Liquid Level Detection Device 1A>
Next, the configuration of the liquid level detection device 1A will be described with reference to FIGS.

  The liquid level detection device 1A includes a plurality of sensors 10a to 10d installed on the surface of the container 9 (collectively referred to as sensors 10 when there is no need to distinguish each of the sensors 10a to 10d), and the sensor 10 And a control measuring device 20 that controls and measures a sensor signal from the sensor 10.

  Each of the sensors 10 a to 10 d has the same configuration, and includes a heating body 102 that heats the container 9 and a temperature measurement element 103 that functions as a temperature measurement layer, and the periphery thereof is covered with a heat insulating material 16. In this state, it is installed on the surface of the container 9. Further, the sensors 10a to 10d are connected to the control measurement device 20 through a power supply line and a signal line. And the sensors 10a-10d are installed in the outer surface of the container 9 so that a height position may mutually differ, as shown in FIG.

  Hereinafter, each member which comprises sensor 10a-10d, the heat insulating material 16, and the control measuring device 20 are demonstrated in order.

(Heating body 102)
The heating element 102 generates heat by being fed from an electric wire. In order to eliminate variations in sensor measurement values between the sensors 10, the heating element 102 is configured to have the same resistance value and heat generation amount between the sensors 10. Moreover, the heating body 102 is, for example, a rectangular resistor. Since the outer surface of the container 9 is a curved surface, a small resistor is desirable in consideration of easy adhesion. Further, the heating element 102 itself may be a resistor, or the resistor may be protected with ceramic or the like.

(Temperature measuring element 103)
The temperature measuring element 103 uses a thermoelectric conversion element typified by a thermocouple or a temperature measuring resistor typified by a thermistor, and is connected to the control measuring device 20 by a signal line. The temperature measuring element 103 is preferably as small as possible and has a small heat capacity in order to suppress variations in sensor measurement values among the sensors 10.

(Insulation material 16)
The heat insulating material 16 prevents heat from entering from the outside of the sensor. For example, a foam heat insulating material obtained by foaming a synthetic resin such as polystyrene foam, phenol foam, urethane foam, or a fiber heat insulating material represented by glass wool. Materials etc. are used.

  The sensor 10 configured as described above is arranged in the order of the heating body 102 and the temperature measuring element 103 from the container 9 side, covers the periphery thereof with a heat insulating material 16, and causes the heating body 102 to generate a temperature difference inside and outside the container 9. It has a structure. With such a configuration, the heat insulating material 16 can prevent heat from entering and exiting from the outside of the container, and can be limited to only the flow of heat from the heating body 102 toward the container 9.

(Control measurement device 20)
FIG. 3 is a block diagram schematically showing an electrical configuration of the control measurement device 20 constituting the liquid level detection device 1A of FIG.
The control measurement device 20 is a device that controls the entire liquid level detection device 1A based on a program stored in the storage unit 203 described later, and includes a heating body control unit 201, a sensor measurement unit 202, a storage unit 203, and a liquid level detection. The input unit 205 and the output unit 206 are connected.

  The heating body control unit 201 is a part that controls the plurality of heating bodies 102 constituting the plurality of sensors 10 to be turned ON / OFF simultaneously. The sensor measurement unit 202 is a part that simultaneously measures a plurality of temperature measurement elements 103 constituting the plurality of sensors 10. The storage unit 203 is a part that stores a control program and a program corresponding to the flowchart of FIG. 12 to be described later, and stores each measurement value measured by the sensor measurement unit 202. The liquid level detection unit 204 is a part that analyzes each measurement value measured by the sensor measurement unit 202 and the data stored in the storage unit 203 to identify the liquid level position of the container 9.

  The input unit 205 is a part for inputting information from the outside, and is used, for example, when inputting sensor information of the refrigeration air conditioner. The output unit 206 is used to output information processed by the control measurement device 20, for example, the liquid level position to the outside. By providing the output unit 206, a remote monitoring function such as transmitting information remotely is added. be able to.

<Installation Method of Liquid Level Detection Device 1A>
Next, an installation method of the liquid level detection device 1A will be described. This liquid level detection device 1A is a method of checking the liquid level position with the liquid level detection device 1A alone, outputting the information by the output unit 206, using it in a device such as a refrigerating air-conditioning apparatus, or the like. It can be used by using a method such as a method of incorporating in a form connected to existing equipment.

  The specific installation method of the liquid level detection device 1A is installed in a portion where there is no unevenness or corrosion on the surface of the container 9. The sensors 10 may be individually installed one by one, or a plurality of sensors may be collectively attached using a jig.

  In addition, it is desirable to install the plurality of sensors 10 at regular intervals. This is because if the distance is equal, the association between the position of the sensor 10 and the liquid level can be facilitated. However, when the fluctuating liquid level position is limited, or when the range of the liquid level position to be detected is limited, the installation positions of the sensors 10 are not set at regular intervals, and the intervals are changed according to the required resolution. Also good. That is, the interval measured at a high resolution may be narrowed, and the interval measured at a low resolution may be widened. In addition, the number of sensors 10 may be reduced by installing as many as necessary in necessary places.

  Next, the relationship between the fluid velocity and the heat transfer coefficient that affects the container surface temperature when the container in which the internal fluid is flowing is heated from the outside will be described.

<Relationship between fluid velocity and heat transfer coefficient>
FIG. 4 is a diagram showing the relationship between the fluid velocity and the heat transfer coefficient of air, water, liquid refrigerant (R410A, 20 ° C.), and gas refrigerant (R410A, 20 ° C.). A is air, B is water, C is a gas refrigerant, D is a liquid refrigerant, and the relationship between the fluid velocity and the heat transfer coefficient. In C and D, the part where the heat transfer coefficient greatly changes with the increase in flow velocity is the part where the fluid flow state changes from laminar flow to turbulent flow.

  In FIG. 4, in any fluid of A to D, the heat transfer rate increases as the fluid velocity increases. Further, when comparing the gas refrigerant C and the liquid refrigerant D, the liquid refrigerant has a higher heat transfer rate than the gas refrigerant at the same flow rate, and the rate of increase in the heat transfer rate due to the increase in flow rate, that is, the slope of the liquid refrigerant is also greater. It is getting bigger.

  Further, the difference in heat transfer coefficient between the gas refrigerant C and the liquid refrigerant D is small with respect to the difference in heat transfer coefficient between the air A and the water B. It can be seen that the heat transfer coefficient is the same as that of the refrigerant, or that the gas refrigerant may exhibit a higher heat transfer coefficient than the liquid refrigerant. Specifically, when the speed of the liquid refrigerant is 0.4 m / s as shown by the dotted line a, the gas refrigerant shows the same heat transfer coefficient at 0.7 m / s as shown by the dotted line b. Further, when the gas refrigerant is 0.7 m / s or more as shown by the dotted line b, the heat transfer coefficient is higher than that of the liquid refrigerant when the gas refrigerant is 0.4 m / s.

<Container surface temperature measurement principle of sensor 10 in liquid level detection device 1A>
Next, the temperature measurement principle of the sensor 10 in the liquid level detection device 1A will be described. In the sensor 10, as described above, the temperature measuring element 103 is installed outside by the heating body 102, that is, at a position farther from the container surface than the heating body 102. And since the heating amount (heat generation amount) of each heating element 102 of each sensor 10 is the same, if it thinks simply, it will seem that the temperature measurement element 103 of each sensor 10 detects the same temperature. However, in actuality, the temperature of the heating element 102 itself is different due to the influence of the container surface temperature (in other words, depending on the state of the fluid inside the container). The measured values are also different.

  That is, the temperature of the surface portion of the container that easily radiates heat due to the influence of the inner fluid is lower than the temperature of the surface portion of the container that hardly radiates heat. Therefore, when the heating body 102 is installed on the surface portion of the container that easily dissipates heat, the temperature of the heating body 102 becomes lower than when it is installed on the surface portion of the container that does not easily dissipate heat. Therefore, the measured value of the temperature measuring element 103 provided in the heating body 102 is also lowered.

  On the other hand, the temperature of the container surface portion that is difficult to dissipate heat due to the influence of the inner fluid is higher than the temperature of the container surface portion that easily dissipates heat. The measured value also increases.

  As described above, the temperature of the heating element 102 varies depending on whether the part where the heating element 102 is installed is easy to radiate heat or is difficult to radiate heat. It becomes.

<Measured value of sensor 10 when container 9 is heated and predicted phenomenon inside container>
The measured value of the sensor 10 when the container 9 is heated and the phenomenon inside the container, which are predicted, are divided into a state where the refrigeration air conditioner is stopped and a state where it is operating, with reference to FIGS. explain.

(When the refrigeration air conditioner is stopped)
FIG. 5 is a diagram showing measured values (container surface temperature) of each sensor 10 after heating the heating body 102 of the liquid level detection device 1A when the refrigeration air-conditioning apparatus is stopped. The container height. (1) in FIG. 5 is a line connecting plot points of the respective measured temperatures, that is, after heating by the heating element 102 when the refrigeration air conditioner is stopped and the liquid fluid is stored up to the container height Z. The measured value of each sensor 10 is shown. FIG. 6 is a diagram in which the flow of fluid inside the container is estimated in the state of FIG.

  As shown in FIG. 5, when the container 9 at the time of stopping is heated by the heating body 102, the measured value is substantially constant at the upper part of the gas part (α), and the measured value becomes closer to a certain amount on the liquid surface Z. The temperature starts to decrease relative to the upper part of the gas part, and the lower part (β) than the liquid level Z shows a relatively lower temperature than the upper part. That is, the gas part surface temperature is relatively higher than the liquid part surface.

  This is presumed as follows. As shown in FIG. 6, the fluid inside the container when the refrigeration and air-conditioning apparatus is stopped is in a stationary state (natural convection) for both gas and liquid. When the heat transfer coefficient of the fluid is compared in FIG. 4, the heat transfer coefficient of the gas part is lower than that of the liquid part (that is, it is difficult to dissipate heat from the container wall surface to the gas part). It becomes close to (heating temperature by the heating body 102).

  Further, when the gas part is close to the liquid level, the heat conduction to the inside of the container increases due to the heat conduction of the metal container 9 and the high heat transfer coefficient of the liquid part. For this reason, as it approaches the liquid level, the heat of the heating element 102 is radiated into the container through the surface of the container, and the measured value decreases.

(When the refrigeration air conditioner is operating)
FIG. 7 is a diagram showing measured values (container surface temperature) of each sensor 10 after heating of each sensor 10 of the liquid level detection device 1A when the refrigeration air conditioner is in operation. Is the container height. (2) in FIG. 7 is a line connecting plot points of each measured temperature, that is, by the heating element 102 when the refrigeration air conditioner is operating and the liquid fluid is stored up to the container height Z. The measured value of each sensor 10 after heating is shown. (1) in FIG. 7 shows (1) in FIG. 5 with a dotted line for comparison. FIG. 8 is a diagram in which the flow of fluid inside the container is estimated in the state of FIG.

  As shown in FIG. 7, when the container surface is heated by the heating body 102 of the sensor 10, the measured value of each sensor 10 is a substantially constant temperature above the gas part (α ′) and is constant at the liquid level Z. As the amount approaches, the measured value starts to decrease, and the lowest measured value at the liquid level Z is shown. And a measured value rises relatively as it becomes the container lower part from the liquid level Z. Comparing the measured value (line (1)) when the refrigeration air conditioner is stopped with the measured value (line (2)) during operation, the gas part (α ′) and the upper part of liquid (β ′) are more Also, the measured value at the time of operation is relatively lower, and at the lower part of liquid (γ ′), the measured value at the time of stop and at the time of operation is substantially equal or equal.

  This is because the fluid flows in from the upper part of the container 9 when the refrigeration air conditioner is in operation because the container 9 has an inlet at the upper part. In other words, it is considered to be due to the following phenomenon. As shown in FIG. 8, forced convection occurs in the gas part and the liquid part at the upper part of the container due to the influence of the inflowing fluid, and the speed of the fluid increases as compared to when it stops. However, as the liquid becomes lower, the flow rate becomes slower because it is less affected by the inflowing fluid (the speed close to the stop time).

  That is, FIG. 9 shows the relationship between the liquid fluid velocity and the height. As shown in FIG. 9, it is considered that the velocity distribution is generated in the vertical direction in the liquid portion. From the above, during operation, the flow velocity of the gas part and the upper part of the liquid becomes faster than when stopped, and this increases the overall heat transfer coefficient during operation than when stopped. Therefore, the measured value is lower during operation than when it is stopped. However, it is considered that the heat transfer rate does not change at the lower part of the liquid because the flow rate is not different from that at the stop, and the measured value is not different from that at the stop. Further, with reference to FIG. 4, the flow velocity at the lower part of the working liquid is the same as when stopped, for example, 0.4 [m / s], and in the gas section, the flow velocity increases, for example, 1.0 [m / s]. If the flow rate on the gas part side increases, the heat transfer coefficient on the gas part side approaches the liquid part side and becomes higher. As a result, the measured value of the sensor 10d is lower than when the sensor is stopped. It can be said that the situation is difficult to distinguish from the measured value of 10a.

<Principle of liquid level detection>
The temperature of the fluid inside the container is basically the same in both the liquid part and the gas part, and there is no temperature difference. When there is no temperature difference between the inside and outside of the container, or when the temperature difference is small, there is no difference between the liquid part and the gas part, or the difference cannot be determined. However, by forcibly applying heat from the outside of the container, a temperature difference is generated in which the temperature outside the container becomes higher than the inside temperature as necessary for detecting the liquid level. Thereby, the difference in heat dissipation on the surface of the container is made remarkable, the difference (temperature) is measured, and the liquid level is specified.

  Based on the phenomenon inside the container described above, the principle of liquid level detection in the liquid level detection apparatus 1A will be described.

  The conventional liquid level detection method detects the liquid level using the principle that the temperature of the surface portion of the container 9 corresponding to the gas portion and the liquid portion in the container 9 is different. It was. Specifically, a temperature threshold value is set, a portion above the threshold value is a gas portion, and a low portion below the threshold value is a liquid portion, and the liquid level is detected.

  However, in this method, since the temperature of the lower part of the liquid becomes relatively higher than that of other parts, the lower part of the liquid is erroneously detected as a gas part, and accurate liquid level detection cannot be performed. Specifically, referring to FIG. 7, when the operating threshold is set to T0, the sensor 10a is determined to be a gas part, and 10a: gas part, 10b: liquid part when considered from the sensor at the bottom of the container. Measurement results of 10c: liquid part, 10d: gas part are obtained, and the liquid surface position cannot be accurately specified.

  Therefore, when the fluid inside the container flows, it is necessary to detect the liquid level in consideration of the phenomenon inside the container. That is, it is necessary to detect the heat transfer coefficient distribution in the flowing part. When the fluid inside the container flows, the heat transfer coefficient in the upper part of the container, that is, in the vicinity of the liquid surface, is relatively higher than in the other gas part and the lower part of the liquid. This is due to the following reason.

  That is, when the inflow speed is increased and the flow velocity of the gas part is increased, the flow speed is increased in proportion to the increase of the inflow speed in the upper part of the liquid as well as the gas part. As shown in FIG. 4, the liquid refrigerant generally has a higher heat transfer coefficient than the gas refrigerant, and the change width (inclination) of the heat transfer coefficient with respect to the change in the inflow speed is also large. For this reason, the highest heat transfer coefficient in the entire inside of the container is the upper part of the liquid (near the liquid level).

  From the above, the measured value of the sensor 10 in the upper part of the liquid (near the liquid level) (in this example, the temperature of the sensor 10c) is the lowest relative to the sensor 10 installed in the other part.

<Liquid level detection method 1>
From the above, as the liquid level detection method 1, the liquid level is determined as follows. That is, in order to detect the liquid level without erroneous detection, the position of the sensor 10 having the lowest measured value among the plurality of sensors 10 installed in the vertical direction on the outer surface of the container is specified as the liquid level. The liquid level position can be detected without detection.

<Liquid level detection method 2>
Further, as the liquid level detection method 2, the liquid level can also be determined as follows. The liquid level detection method 2 is a method capable of specifying a position close to the liquid level as the liquid level even when the sensor measurement values vary. The outline of the liquid level detection method 2 will be briefly described first. A threshold value is set by a method described later, and the position of the sensor 10 installed at the highest position among the sensors 10 in which measured values less than the threshold value are measured is defined as a liquid level. This is a method of specifying the liquid level as the surface position.

  Here, the variation in the sensor measurement value is caused by the sensor installation method, for example, the pressing force of the sensor 10 is different for each sensor 10, the temperature of the surface of the heating body 102 varies, or the thermal resistance between the sensor 10 and the container 9. May be different for each sensor 10 or the like. In addition, variations in sensor measurement values also occur due to sensor errors of the temperature measurement element 103, aging degradation, and the like.

  Hereinafter, the point that the liquid level can be detected with high accuracy even if the sensor measurement values vary will be described using a specific image.

  FIG. 10 is a diagram showing the relationship between the sensor measurement value (container surface temperature) after heating by the heating body 102 of each sensor 10 and the container height when the refrigeration air conditioner is in operation. The axis is the container height. Z indicates the liquid level in the container 9. Further, (a) shows the measurement values in the normal state in which the sensor measurement values are not varied and the container surface temperature is accurately detected, and (b) and (c) are the measurement values with respect to the normal state in (a). The measured value when the variation is only ± α is shown. Further, (d) shows a threshold value.

Hereinafter, the reason why the determination method of the liquid level detection method 2 is effective when the sensor measurement values of the respective sensors (10a, 10b, 10c from the bottom) arranged below the liquid level position Z are varied will be described. A description will be given in comparison with Method 1. Here, in order to make the difference between the liquid level detection method 1 and the liquid level detection method 2 most prominent, the measured value of the sensor 10a varies to the −α side (a ′), Ta is measured, and the sensor 10b is normal. An example will be described in which a measured value is obtained (b ′), Tb is measured, the sensor 10c varies toward the + α side (c ′), and Tc is measured.

  In the liquid level detection method 1, since the sensor position with the lowest measured value is specified as the liquid level, here, since Ta <Tb <Tc, the sensor position of the sensor 10a is determined as the liquid level position.

  On the other hand, in the liquid level detection method 2, a threshold value is provided, and the sensor installed at the highest position among the sensors that are less than the threshold value is determined as the liquid level position. , C ′ are all less than the threshold value, the sensor position of the sensor 10c is determined as the liquid level position.

  Thus, in the liquid level detection method 1, the sensor 10a is determined as the liquid level position, and in the liquid level detection method 2, the sensor 10c is determined as the liquid level position. Since the actual liquid level position is the position indicated by Z in FIG. 10, when the measured value of the sensor 10 varies, the liquid level detection method 2 sets the position closer to the actual liquid level. It can be seen that the position can be accurately determined, that is, the accuracy is high.

  In addition, although the liquid level detection method in 1 A of liquid level detection apparatus was demonstrated above, 1 A of liquid level detection apparatuses can also detect that the liquid fluid was lost from the inside of a container based on a sensor measured value. This will be described below.

  When there is no liquid from the inside of the container and the gas is filled, the measured values of all the sensors 10 tend to be uniformly higher than the container surface temperature of the liquid part when there is liquid. Therefore, if the temperature is lower than the container surface temperature of the gas part and can be clearly distinguished from the container surface temperature of the liquid part as a threshold value, when the measured values of all the sensors 10 are higher than the threshold value, It can be detected that the liquid fluid has disappeared from the inside of the container.

  Therefore, as a specific detection method on the apparatus, first, at least one of the plurality of sensors 10 is set to a height position where the liquid is not stored (that is, a portion that necessarily becomes a gas part (upper part of the container)). ) And set the sensor as the reference sensor. Then, a temperature that is lower by a preset temperature Ts than the measured value by the reference sensor is set as a threshold value. And the position of the sensor 10 installed in the highest position among the sensors 10 whose measured values are less than the threshold value is determined as the liquid level and output.

  When there is no liquid from the inside of the container, the measured values of all the sensors 10 are equal to or greater than the threshold value. Therefore, none of the sensors 10 corresponds to the sensor 10 installed at the highest position among the sensors whose measured values are less than the threshold value. Therefore, the fact that none of the sensors 10 correspond is output as the liquid level position, so that the user can determine that there is no liquid fluid inside the container.

  As described above, the liquid level detection device 1A according to the present embodiment can detect not only the liquid level but also the liquid fluid from the inside of the container. As described above, the threshold for enabling these is set to a temperature that is lower than the measured value of the reference sensor by a preset temperature Ts. The set temperature Ts is determined in consideration of the temperature difference in the container surface temperature between the gas part and the liquid upper part and the measurement value variation of the sensor 10.

  For example, when the temperature difference of the container surface temperature between the gas part and the liquid upper part is 5 ° C. and the measured value variation of the sensor 10 is ± 1 ° C., the set temperature Ts is set to 2 to 3 ° C. to prevent erroneous determination. . The reason will be described below.

FIG. 11 is a diagram showing the relationship between the measured value after heating by the heating body 102 of each sensor 10 and the container height when the refrigeration air conditioner is in operation, with the horizontal axis representing the temperature and the vertical axis representing the container height. is there. ZZ indicates the height of the liquid level in the container 9. Further, (i i ) represents a measured value (normal value) in a normal state in which there is no variation in sensor measured values, and ( i ) and (iii) have a temperature variation of ± 1 with respect to the normal value of (i i ). The measured value when there was only ℃.

  It is assumed that the sensor 10 is installed at each of the container heights aa, bb, and cc, the position of the container height aa is the liquid part, and the positions of the container heights bb and cc are the gas parts. Then, the sensor 10 at the container height cc is used as a reference sensor, and a liquid level position is determined by determining a threshold value based on the measurement value of the reference sensor. Consider a threshold value that will not be misjudged.

  First, consider a threshold value that does not misdetermine a gas part as a liquid part. When the reference sensor (the sensor at the container height cc) has a measured value that is 1 ° C. lower than the normal value (that is, 84 ° C.), the sensor 10 at the container height bb is not erroneously determined to be at the liquid part position. In order to do so, the threshold value may be less than the measured value (that is, less than 84 ° C.). By making the threshold value less than the measured value (that is, less than 84 ° C.), even if the measured value of the sensor 10 at the container height bb shows a measured value that is 1 ° C. lower than the normal value (that is, 84 ° C.), Get higher. For this reason, the position of the container height bb is not erroneously determined as the liquid part, and can be normally determined as the gas part.

  In order to prevent a sensor having a container height bb in the gas part from being erroneously determined as a liquid part when the measurement value of the reference sensor is a measurement value that is 1 ° C. higher than the normal value (that is, 86 ° C.), a threshold value is used. Is less than 84 ° C., which is less than the variation range temperature (the variation range is 2 ° C. because the variation range is ± 1 ° C.) from the measured value (86 ° C.) of the reference sensor. That is, the threshold value may be a temperature that is less than a value that is 2 ° C. lower than the measured value of the reference sensor. By setting the threshold value in this way, even if the sensor measurement value of the container height bb shows a measurement value that is 1 ° C. lower than the normal value (that is, 84 ° C.), it becomes higher than the threshold value. For this reason, the position of the container height bb is not erroneously determined as the liquid part.

  Next, a threshold value that does not erroneously determine the liquid part as a gas part is considered. Since the measured value of the sensor 10 at the container height aa varies between 79 ° C. and 81 ° C., in order to prevent the sensor 10 having such variation from being erroneously determined to be in the gas portion position, In order to ensure that the measurement value of the sensor 10 at the container height aa is always equal to or less than the threshold value, the threshold value may be set as follows. That is, the threshold value may be greater than or equal to the upper limit value of the variation range (that is, 79 ° C. to 81 ° C.). That is, if it is 81 degreeC or more, since the sensor measured value of the sensor 10 in container height aa will be below a threshold value, it will not misjudge with a gas part. Therefore, if it sees from the measured value of a reference | standard sensor, a liquid part will not be misidentified as a gas part if there exists a threshold more than the lower limit (namely, 84 degreeC) 3 degreeC lower than the lower limit of the measured value dispersion | variation range.

  To summarize the above, if the temperature difference between the container surface temperature of the gas part and the upper part of the liquid is 5 ° C and the variation of the sensor measurement value is ± 1 ° C, the set temperature Ts should be determined in the range of 2 to 3 ° C. That's fine. Which temperature in the range of 2 to 3 ° C. is arbitrarily set by the manufacturer of the liquid level detection device 1A. Here, assuming that the temperature is set to 3 ° C., the liquid level detection device 1A dynamically sets a temperature 3 ° C. lower than the reference sensor measurement value as a threshold value at the time of liquid level detection, and the measurement value less than the threshold value. As a result, the position of the sensor 10 installed at the highest position among the sensors 10 that measured the value is output as the liquid level position. The setting of the threshold is not limited to a method of dynamically setting based on the measurement value of the reference sensor at the time of liquid level detection, but as a fixed value determined in advance according to the operating state of the refrigeration air conditioner, that is, the temperature of the refrigerant flowing inside You may set it. However, when the liquid level is detected, it is better to set the value dynamically based on the measured value of the reference sensor, taking into account multiple factors such as installation conditions, ambient environment such as outside wind and outside air temperature, and refrigerant temperature inside the container. Therefore, it is possible to eliminate misjudgment and to detect the liquid level with higher accuracy.

  In addition, it is possible to grasp in advance how much the temperature difference of the container surface temperature between the gas part and the upper part of the liquid is, and how much the sensor measurement value variation is about ± ° C. Therefore, what is necessary is just to determine how many degrees C lower than the measured value of a reference | standard sensor should be made into a threshold value based on such information.

  Here, an example has been described in which the threshold value is set in consideration of both the temperature difference between the container surface temperature between the gas part and the upper part of the liquid and the measured value variation of the sensor 10, but at least the measured value variation of the sensor 10 May be set in consideration of. That is, a temperature that is lower than the measured value of the reference sensor by a set temperature set in consideration of variations in measured values of the sensor 10 may be set as the threshold value.

  Now that the liquid level detection method 2 has been clarified, the flow of processing when the liquid level detection apparatus 1A detects the liquid level will be described.

<Liquid level detection flow>
FIG. 12 is a flowchart showing the flow of processing when the liquid level is detected by the liquid level detection apparatus 1A according to the embodiment of the present invention. Next, the flow of liquid level detection will be described with reference to FIG.

  First, the control measurement device 20 performs data measurement with all the sensors 10 (S101). The measurement value here (that is, the measurement value before heating of the heating element 102) is used for detecting an abnormality of the temperature measurement element 103. Next, the control measurement device 20 checks whether or not all the measured values measured in S101 are equal to each other (S102). When a different measurement value is measured (S102; No), the control measurement device 20 issues a notification to that effect because the sensor 10 may be disconnected or disconnected. (S104).

  On the other hand, if all the measured values are equal to each other (S102; Yes), the control measurement device 20 heats the heating body 102 of each sensor 10 (S103). Then, after heating of the heating body 102 is started, it is determined whether or not a certain time (for example, 2 minutes) has elapsed (S105). If the certain time has not elapsed, the process returns to S103, and if the certain time has elapsed, Is stopped (S106). And after stopping the heating of the heating body 102, the control measurement apparatus 20 measures data again by all the sensors 10 (S107). The temperature is measured at this timing because the temperature difference between the inside and outside of the container 9 is the largest immediately after the heating of the heating element 102 is stopped, and the difference in heat flux between the gas part and the liquid part appears most prominently. This is because the temperature change of the body 102 appears remarkably.

  Then, the liquid level is determined by the above-described liquid level detection method 1 or liquid level detection method 2 using the measurement value measured in S107 (S108), and the liquid level detection is completed.

  As described above, according to the present embodiment, since the liquid level position is detected by the liquid level detection method 1 or the liquid level detection method 2 described above, the fluid flows into and out of the container. The liquid level position can also be specified when the fluid inside the container is flowing. Further, in the liquid level detection method 2, the liquid level can be detected even if the sensor measurement value varies, and the liquid level can be detected with high accuracy.

  The liquid level detection device 1A may be modified as follows in addition to the configuration shown in FIG. In this case, the same effect can be obtained. Hereinafter, modifications will be sequentially described.

  In the flowchart of FIG. 12, an example is described in which the temperature is measured after heating of the heating body 102 is stopped. However, the present invention is not limited to this, and the temperature may be measured before the heating of the heating body 102 is stopped. This is because the temperature at the time when the heating body 102 is heated sufficiently, in other words, at the time when sufficient heating is performed by the heating body 102, and at the time when the influence of the outside air temperature is small immediately after that, the heat flow in the gas-liquid phase. This is because it is a time zone in which a difference in bundles tends to appear remarkably.

Moreover, although the method of determining the liquid level by the above-described liquid level detection method 1 or liquid level detection method 2 using the measured value was described, the present invention is not limited to this, and there is a measurement value of the temperature measurement element 103. The liquid level may be determined by comparing the time until the temperature is reached (an index related to the measurement value by the temperature measurement element 103). This is because when the heating body 102 is heated, the measured values of the sensor 10 corresponding to the gas part and the lower part of the liquid level tend to be high, whereas the measured value of the sensor 10 corresponding to the upper part of the liquid (near the liquid level) increases. The gas-liquid determination is performed by utilizing the difficulty.

  Although all the sensors 10 are installed on the side surface of the container 9 here, the invention is not limited to this. The reference sensor 10 is installed on the upper side of the container 9 and the other sensors are installed on the side surface of the container 9. Then, using the measured value of the reference sensor and the measured value of the sensor other than the upper part of the container 9, the upper part of the liquid (near the liquid level) is determined by the liquid level detection method 1 or the liquid level detection method 2 described above. May be.

  As for heating of the heating element 102, the heating element 102 may be constantly heated, or the heating element 102 is heated only during the time period during which the liquid level is detected using the control measurement device 20, and the heating is stopped otherwise. May be. When the heating element 102 is heated only during the time period in which the liquid level detection is performed, unnecessary heating in the time period in which the liquid level detection is not performed can be prevented.

  Further, as described above, a thermoelectric conversion element or a resistance thermometer is used for the temperature measuring element 103 used in the sensor 10, but a self-heating thermistor that is a self-heating resistor may be used. When the self-heating thermistor is used, it is not necessary to separately provide the heating body 102 in addition to the temperature measuring element 103. Further, by using a self-heating thermistor, the signal line can be eliminated, and a smaller sensor can be manufactured. Moreover, since there are few wirings, the operation | work of sensor installation can be made efficient.

Further, the container 9 is heated by the heating body 102, but the present invention is not limited to this. For example, in the case of the following (A) or (B), the heating body 102 does not need to be provided.
(A) When the temperature difference between the inside of the container and the outside of the container is large (B) When the fluid outside the container is at a different temperature from the inside of the container and the flow rate of the fluid is high

  Even in such cases (A) and (B), if the internal fluid is flowing, the container surface temperature in the vicinity of the liquid level becomes the lowest. Therefore, the sensor position indicating the lowest temperature is set as the liquid level position. The liquid level position can be specified.

  In addition, although the container 9 is heated by the heating body 102, the present invention is not limited to this, and the container 9 may be cooled by the cooling body. When the container 9 is cooled, the container surface temperature in the vicinity of the liquid level becomes the highest. For this reason, when determining a liquid level position by the said liquid level detection method 1, a liquid level position can be specified by making the position of the sensor 10 which shows the highest temperature into a liquid level position.

  In addition, when the container 9 is configured to be cooled by the cooling body, in order to determine the liquid level position by the liquid level detection method 2, a sensor that is always installed in the gas part (upper part of the container) is used in the same manner as described above. As a reference sensor, a temperature that is higher than a measured value of the reference sensor by a preset temperature is determined as a threshold value. The set temperature is determined in consideration of at least the measurement value variation of the sensor 10 as described above. And what is necessary is just to determine the sensor position of the highest position among the sensors 10 which show temperature higher than the threshold value as a liquid level position.

  Moreover, although the container 9 installed on the low pressure side of the refrigeration air conditioner has been described as an example of the liquid level detection target by the liquid level detection device 1A, it is not limited to this and is installed on the high pressure side of the refrigeration air conditioner. It may be a container. Even in the case of a container installed on the high pressure side, the liquid level can be detected by the same method as described above.

  In the container installed on the high pressure side of the refrigeration air conditioner, the liquid fluid basically flows in and out, so that the liquid part flows more than in the case where it is installed on the low pressure side where the gas fluid flows in and out. growing. And the point that the container surface temperature of a liquid part becomes lower than a gas part is the same as that of the case of the container installed in the low voltage | pressure side.

  In addition, the container installed on the high-pressure side of the refrigeration air-conditioning apparatus is heated to heat the container from the outside as in the past, depending on the structure or size of the container, as in the case of the liquid level detection of the container installed on the low-pressure side. There is a problem that the liquid level cannot be detected only by the difference in the container surface temperature. The case where the liquid level cannot be detected only by the difference in the container surface temperature at the time of heating is, for example, a structure where the container is vertically long and the upper part is affected by the inflowing fluid, while the lower part is not affected by the inflowing fluid In other words, that is, the case where the fluid flow state is different between the upper and lower sides of the container.

  The container surface temperature is also affected by the physical properties of the internal fluid. For example, when a highly viscous liquid is stored in the container, the lower part of the container is less likely to be affected by the flowing fluid. For this reason, the flow rate increases in the gas part and the heat transfer coefficient tends to increase, whereas the flow rate does not change in the lower part of the liquid and the heat transfer rate does not change. The temperature difference becomes smaller or the temperature of the gas part becomes lower than the temperature of the lower part of the liquid.

  As described above, the container installed on the high pressure side of the refrigeration air conditioner has the same problem as the liquid level detection of the container installed on the low pressure side, and this problem is solved by the same method as described above. It can be solved by detecting.

  Moreover, in the said embodiment, although the container used for a refrigerating and air-conditioning apparatus and storing a refrigerant | coolant was demonstrated as a liquid level detection object, it is not restricted to this, What is necessary is just a container which stores a liquid. . The liquid level detection device 1A of the present embodiment is particularly effective when used for liquid level detection when the internal liquid is flowing.

  1A Liquid level detection device, 9 container, 9a inlet piping, 9b outlet piping, 9c oil return hole, 9d suction port, 10 all sensors, 10 (10a to 10d) sensor, 16 heat insulating material, 20 control measuring device, 102 heating element , 103 temperature measurement element, 201 heating body control unit, 202 sensor measurement unit, 203 storage unit, 204 liquid level detection unit, 205 input unit, 206 output unit.

Claims (13)

A plurality of sensors that are installed on the surface of the container for liquid level detection so that the height positions are different from each other, and measure the temperature of the installation location by a temperature measuring element,
A liquid level detection unit that identifies a liquid level position in the container in a state where fluid flows into and out of the container as a position of a sensor having the lowest measured value among the plurality of sensors. Liquid level detection device. The liquid level detection unit is configured such that the measurement values of the plurality of sensors are higher than the measurement values of a reference sensor installed at a height position where the fluid is not stored in the container. the set temperature as low temperature set in advance in consideration of the variation range, the liquid level detecting apparatus according to claim 1, wherein a setting of the threshold value. A plurality of sensors that are installed on the surface of the container for liquid level detection so that the height positions are different from each other, and measure the temperature of the installation location by a temperature measuring element,
When the liquid level position in the container in a state where fluid flows into and out of the container is measured at a measurement value lower than a set threshold, the liquid level position is the position of the sensor installed at the highest place. A liquid level detection unit to be identified,
The liquid level detection unit acquires a measurement value of a reference sensor installed at a height position where the fluid is not stored in the container among the plurality of sensors at the time of liquid level detection, and the measurement value The liquid level detection device , wherein a temperature that is lower than a preset temperature in consideration of a variation range of measurement values of the plurality of sensors is set as the threshold value . Each of the plurality of sensors has a heating body provided between the temperature measuring element and the surface of the container, and the temperature difference is generated inside and outside of the container by heat generation of the heating body. The liquid level detection device according to any one of claims 1 to 3. The temperature measuring element is a temperature measuring element having a self-heating resistor, and the temperature difference is generated inside and outside the container by heat generation of the resistor. The liquid level detection apparatus according to claim 1. A plurality of sensors that are installed on the surface of the container for liquid level detection so that the height positions are different from each other, and measure the temperature of the installation location by a temperature measuring element,
A liquid level detection unit that identifies a liquid level position in the container in a state where fluid flows into and out of the container as a position of a sensor having the highest measured value among the plurality of sensors. Liquid level detection device. The liquid level detection unit is configured such that the measurement values of the plurality of sensors are higher than the measurement values of a reference sensor installed at a height position where the fluid is not stored in the container. The liquid level detection device according to claim 6 , wherein a temperature that is higher by a preset temperature in consideration of a variation range is set as the threshold value. A plurality of sensors that are installed on the surface of the container for liquid level detection so that the height positions are different from each other, and measure the temperature of the installation location by a temperature measuring element,
When the liquid level position in the container in a state where the fluid flows into and out of the container is measured with a measured value higher than a set threshold, the liquid level position is the position of the sensor installed at the highest place. A liquid level detection unit to be identified,
The liquid level detection unit acquires a measurement value of a reference sensor installed at a height position where the fluid is not stored in the container among the plurality of sensors at the time of liquid level detection, and the measurement value The liquid level detection device , wherein a temperature higher than a preset temperature in consideration of a variation range of measurement values of the plurality of sensors is set as the threshold value . Each of the plurality of sensors has a cooling body provided between the temperature measuring element and the surface of the container, and the temperature difference is generated inside and outside the container by cooling the cooling body. The liquid level detection device according to claim 6, wherein the liquid level detection device is a liquid level detection device. The fluid is a refrigerant;
The liquid level detection device according to any one of claims 1 to 9, wherein the liquid level detection unit specifies a liquid level position of the liquid refrigerant in the container. The liquid level detection device according to any one of claims 1 to 10, wherein a fluid inlet is provided at an upper portion of the container. The liquid level detection device according to claim 1, wherein a fluid outlet is provided at an upper portion of the container. The liquid level detection device according to any one of claims 1 to 12,
A liquid level detection target container whose liquid level is detected by the liquid level detection device;
A compressor,
A condenser,
An aperture device;
An evaporator,
The refrigerating and air-conditioning apparatus according to claim 1, wherein the container is installed in a portion from the throttling device to the compressor through the evaporator.

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