JPH0146007B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a flowmeter.

According to the invention, a meter for measuring the flow rate of a fluid is located between an inlet and an outlet for said fluid; along the surface of which the fluid flows as it passes from the inlet to the outlet; a first surface; a temperature bridge connecting the first surface to a second surface; means associated with the second surface for maintaining a temperature difference between the first and second surfaces; a temperature measuring device adapted to be sensitive to the temperature at an intermediate point of the relatively conductive portion of the bridge; and a temperature measuring device adapted to measure the temperature of the fluid flowing along the first surface and the temperature of the second surface, respectively. ; the temperature bridge has a relatively good thermal conductivity that is thermally connected to the first surface and a thermal conductivity between the relatively good thermal conductivity and the second surface. the temperature bridge has a relatively poor portion of the temperature bridge; the heat flow is formed by the first and second temperature bridge;
Insulated so that passage between surfaces is effectively restricted.

As the fluid flows along the first surface, viscous movement between the fluid and the surface creates a boundary layer. The thickness of the boundary layer is determined by the velocity of the fluid, and the boundary becomes thinner as the velocity of the fluid increases. This boundary layer acts as a thermal insulation layer between the first surface and the bulk of the fluid, the degree of insulation being determined by the thickness of the boundary layer and thus the velocity of the fluid. This variable resistance to heat flow at the first surface affects the heat flow of the temperature bridge and thus the temperature at the midpoint of that temperature bridge. The ratio of the temperature drop between the midpoint (Tm) and the second surface (Tc) to the temperature drop between the fluid flowing along the first surface (Th) and the midpoint (Tm) relative to the fluid flow rate (i.e., Tm -Tc/Th-Tm) gives a suitable curve for meter calibration. However, other ratios could be used for this purpose, such as eg Tm-Tc/Th-Tc.

Preferably, the more thermally conductive portion of the temperature bridge has a conductivity that is at least 10 times greater than that of the less thermally conductive portion. This can be achieved by choosing a material with suitable conductivity and/or by adjusting the size of the part. For example, the relatively poorly conductive portion may be made from a relatively thin layer of thermal insulation material, or the bridge may otherwise be of homogeneous construction to reduce the width of the relatively poorly conductive portion.

Where the temperature of the fluid flowing along the first surface changes, even if the second surface can be kept at a constant temperature above the operating range,
Conveniently, the temperature of the second surface is varied.

The temperature of the second surface can be maintained at a different temperature than the first surface by the secondary fluid flow. This type of meter is particularly suitable for use in closed systems, such as, for example, heating systems where fluid is supplied at one temperature and returned at a different temperature. In that case, a meter is used to measure the flow rate of the fluid flowing through the system, so that the incoming fluid flows along the first surface while the outgoing fluid flows along the first surface to create the necessary temperature difference. It is made to flow along two surfaces. In such devices, the flowmeter can be made to function as a calorimeter, and the temperature used in the system is determined by the flow rate and the temperature at the inlet and outlet from the system, which can be calculated by a suitable processor. It is a function of the temperature difference. If a secondary flow of fluid is used to maintain the second surface at a different temperature than the first surface, this surface must be provided with means to overcome the insulating effect of the boundary layer. By providing a thermally insulating body with a large surface area in contact with the second surface along which the secondary fluid flows and heat is transferred, the second surface is substantially at the temperature of the secondary fluid flow. can be maintained at a constant temperature without appreciable temperature changes due to changes in the rate of secondary fluid flow.

The present invention will be explained with reference to the drawings.

The flow meter schematically shown in Figure 1 has a straight flow path 1.
The flow path has an inlet 10 and an outlet 11 interconnected by a nylon washer 1.
3 and the inner diameter of a cylinder in which copper washers 14 are arranged alternately. The washers are clamped together in a nylon housing 15. The nylon sheath 16 is the nylon sheath 13,
14 and a copper sheath 17 surrounds the nylon sheath 16. Washiya 1
The cylinders 3 and 14 are surrounded by a fluid-tight chamber 18 in which an inlet 19 and an outlet 20 are provided. The chamber 18 is divided into two by a copper buttful 21, and a hole 22 is provided through the buttful 21 at a point remote from the inlet 19 and the outlet 20, thereby providing a connection from the inlet 19 to the outlet. Fluid passing through chamber 18 to 20 will flow around the outside diameter of the barrels of washers 13,14.

A temperature measuring device, for example a thermocouple 27, is connected to the washer 1.
It is provided at a position midway between the inner diameter and outer diameter of the copper washer 23 in the center of the cylinders 3 and 14. Further temperature measuring devices (not shown) are provided at the inlets 10 and 19 to determine the temperature difference between the midpoint (Tm) of the copper washer 23 and the inlet 19 (Tc) The temperature difference at the midpoint (Tm) of (Th) can be measured.

The meter described above is connected to a closed system, for example a heating system, in which hot fluid flows into the system and relatively cool fluid is returned from the system. An inlet pipe 25 to the system is connected across the inlet 10 and outlet 11 of the meter, and the connections between the inlet pipe 25 and the inlet 10 and outlet 11 are made of a thermally insulating material such as nylon, so that Heat will not be transferred through the pipe 25 to the tubes of the nylon and copper washers 13,14. A return pipe 26 from the system connects across the inlet 19 and outlet 20 of the chamber 18.
In this manner, the hot fluid entering the closed system would flow through the channel 12 along the inner diameter of the tube of the nylon and copper washers 13, 14 and the copper washer 23. The relatively cool fluid exiting the closed system will then pass through chamber 18 surrounding the outside diameter of the cylinder of washers 13, 14 and copper washer 23. Since the system is closed, the incoming fluid flow rate will be equal to the outgoing fluid flow rate.

In operation, the inner surfaces of the cylinders of washers 13, 14 are warmed by hot fluid, and the outer surfaces are cooled by relatively cold fluid, thereby causing both sides of the cylinders of washers 13, 14 and copper washer 23 to be cooled. are kept at different temperatures. The copper washers 14 on both sides of the copper washers 23 are the copper washers 23 in the middle.
acts as a guard ring to ensure that the heat flow through the copper washer 23 flows radially, resulting in a smooth temperature gradient between its inner and outer surfaces. Will.
As a result, the temperature (Tm) midway between the inner and outer surfaces of washer 23 will be a function of the temperatures of the inner and outer surfaces and the temperature gradient across washer 23.

The fluid is washers 13, 14 and copper washers 23.
flows along the inner surface of the fluid, creating a boundary layer whose thickness is a function of the velocity of the fluid. This boundary layer creates an insulating layer between the bulk of the fluid and the inner surface of the washer 23, so that the temperature of this surface of the washer 23 will be lower than the temperature of the bulk of the fluid (Th). Therefore fluid and washer 23
The temperature difference on the surface of the fluid determines the thickness of the boundary layer and, as a result, the velocity of the fluid. Since the temperature (Tm) intermediate the outer surface of the inner surface of the copper washer 23 varies with the inner surface of the washer 23, it will also vary with the velocity of the fluid flowing along the inner surface. A plot of Tm-Tc/Th-Tm versus fluid flow rate results in a curve as shown in Figure 2, which can be used to calibrate a flow meter.

The nylon sheath 16 around the tubes of the washers 13, 14, 23 reduces the temperature difference across the copper washers 23, thereby increasing the temperature difference between the inner and outer diameters of the copper washers 23 with respect to temperature changes on the inner surface of the copper washers 23. Increases the sensitivity of the intermediate temperature (Tm) and increases the sensitivity of the meter. In the device described above, the temperature of the outer surface of the nylon sheath 16 and the copper sheath 17 around the washer 23 should be equal to the temperature of the fluid flowing through the chamber 18. As the fluid flows along the inside surface of washer 23, a boundary layer will exist between the fluid flowing through chamber 18 and copper sheath 17. However, heat transfer between the copper sheath 17, which has a relatively large surface area, and the copper buffer 21, which is in thermal contact with the fluid flowing through the chamber 18, is
is maintained at substantially the same temperature as the fluid flowing through chamber 18, ensuring that there is no appreciable change in temperature with changes in flow rate. This function need not necessarily be performed by a buffer 21, which has a large and thermally conductive surface area exposed to the secondary fluid flow and in thermal contact with the outer surface of the temperature bridge. It can be achieved by any body made of good material. For example, the copper sheath 17 may be provided with fins for heat exchange.

By using the calibration curve shown in FIG. 2 and appropriate electronic process circuitry, the meter can be adapted to read fluid flow rates. Otherwise, the heat supplied by the closed circuit is the difference between the flow rate and the inlet and return temperature from the system (Th
−Tc) so that electronic circuit components can read the heat dissipated by the system.

In another embodiment shown in FIG. 3, the temperature bridge has a copper washer 23 with a stainless steel washer 30 whose inner surface is exposed to the fluid flowing from the inlet 10 to the outlet 11. It is press-fitted around the washer 23. Copper/stainless steel assembly washer 2
3, 30 are arranged in chamber 18 such that the baffle 21 is in thermal contact with the outer surface of the stainless steel washer 30 in the manner described above, and that the surface is maintained at the temperature Tc of the fluid flowing through the chamber 18. It is located inside. Corresponding holes in the copper washer 23 to form a passageway between the inlet 10 and the outlet 11 and also to ensure that heat flows radially through the copper/stainless steel assembly washers 23, 30. Two blocks 31 of perforated insulation are positioned on either side of a copper/stainless steel assembly washer. A temperature measuring device 27 is connected to the copper washer 23 as described with respect to FIG.

This embodiment of the temperature bridge functions in exactly the same way as the bridge described with respect to FIG. The stainless steel washer 30 forms a relatively poor thermal conductor to reduce the temperature differential of the copper washer 23, thereby allowing it to maintain an intermediate temperature Tm similar to the sheath 16 described with respect to FIG. Increase sensitivity. In yet another embodiment, the temperature bridge can be of similar construction, with the outer section reduced in cross-section to make that section relatively less conductive. With the thick insulating block in the embodiment shown in FIG. 3, the guard ring 14 described in connection with FIG. 1 is not necessary.

The sensitivity of the meter can be further increased by measuring the temperature Tm midway through the shunt between the first surface and the temperature bridge. This can be done in the manner described with respect to FIG. In this embodiment the temperature bridge has a main ring 40 made of brass.
The ring 40 has an inner portion 41 whose inner surface is exposed to the fluid flowing from the inlet 10 to the outlet 11. Inner portion 41 of ring 40
is connected to the outer portion 43 by a relatively thin central portion 42 forming a relatively poorly conducting portion of the bridge. The main ring 40 is mounted within the chamber 18 such that the buffle 21 is in thermal contact with the outer portion 43 for the reasons discussed above.

A secondary copper ring 44 is positioned coaxially with the main ring 40 but spaced therefrom in the exit direction. The inner surface of this sub-ring 44 also includes the inlet 1
0 to outlet 11.
The secondary ring 44 is connected to the inner part 41 of the main ring 40 by a thin brass sleeve 45.
This brass sleeve 45 is separated from the fluid flowing from the inlet 10 to the outlet 11 by an insulating sleeve 46. The temperature measuring device 47 is located at one of the sub-rings 44.
located at the point. Main ring and sub ring 4
0,44 form a passage from the inlet 10 to the outlet 11 through the inner surfaces of the rings 40,44 and also ensure that heat flows between the inner and outer surfaces of the main ring 40 through the central portion 42. It is also surrounded by an insulating block 48 which serves to ensure flow through the sleeve 45 and central portion 42 between the inner surface of the secondary ring 44 and the outer surface of the main ring 40.

In this embodiment, the inner surfaces of both the primary ring 40 and the secondary ring 44 are placed in boundary layer conditions, such that the heat transferred across those surfaces will be a function of their area and fluid flow rate. . Heat across the inner surface of the main ring will raise the temperature gradient in the main ring 40 in the same manner as in the bridge described in FIGS. 1 and 3. Changes in the surface heat transfer caused by changes in flow rate will change the temperature at the point in the inner portion 41 of the main ring 40 where it communicates with the sleeve 45. The shunt formed by the secondary ring 44 and sleeve 45 between the inner surface of the secondary ring 44 and the inner portion 41 of the primary ring 40 will create a varying temperature difference at each end as the flow rate changes. As a result, the intermediate temperature Tm measured at secondary ring 44 by temperature measuring device 47 will be a quadratic function of the flow rate of fluid flowing along the inner surfaces of rings 40 and 44. The increased sensitivity thus achieved can be adjusted by varying the surface area of the primary ring 40 and secondary ring 44 that are exposed to the fluid flowing from the inlet 10 to the outlet 11. In this manner, the sensitivity beyond the meter's operating range can be improved and signal flooding, particularly at high flow rates, can be reduced to the meter's operating range.

Various modifications may be made to the embodiments described above within the scope of the invention. For example, alternative thermally conductive and thermally insulating materials can be used for the various components. Surfaces of components exposed to fluid flow may be coated with a thin layer of thermally conductive, corrosion-resistant material where necessary. Alternatively, the components themselves can be made of corrosion-resistant materials by selecting an appropriate combination of materials.

The operating range or performance of the meter of the present invention depends on the surface area of the surface exposed to the fluid flowing from the inlet 10 to the outlet 11. The meter can then be designed for specific purposes simply by changing its surface area, for example by changing the thickness or internal diameter of the washer 23.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a flowmeter according to the present invention, and FIG. 2 is a scale measurement curve of the flowmeter shown in FIG.
The figure is a sectional view of a modification of the temperature bridge used in the embodiment shown in FIG. 1, and FIG. 4 is a sectional view of yet another form of the bridge. 10,19...Entrance, 11,20...Exit, 1
6, 17, 23...temperature bridge, 13, 14,
23...Watsusha, 18...Chamber, 21...Batsuful, 27,47...Temperature measuring device.

Claims (1)

Claims: 1. An inlet 10 and an outlet 11 for a fluid; a first surface intermediate the inlet 10 and the outlet 11 along which the fluid flows as it passes from the inlet 10 to the outlet 11; a temperature bridge 16, 17, 23 connecting said first surface to a second surface; means associated with said second surface for maintaining a temperature difference between said first and second surfaces; a temperature measuring device 27 adapted to be sensitive to the temperature at the midpoint of the relatively conductive portion 23 of the bridge; and a temperature measuring device 27 for measuring the temperature of the fluid flowing along the first surface and the temperature of the second surface, respectively. a measuring device; the temperature bridge is formed between a portion 23 of relatively good thermal conductivity that is thermally connected to the first surface and the portion 23 of relatively good thermal conductivity and the second surface. the temperature bridge has a relatively poor thermal conductivity portion 16; the temperature bridge is insulated such that heat flow is effectively confined to the path between the first surface and the second surface formed by the temperature bridge. A meter for measuring the flow rate of a fluid, characterized in that: 2 The curve of the ratio of the temperature drop between the midpoint (Tm) and the second surface (Tc) for the fluid flow to the temperature drop between the fluid flowing along the first surface (Th) and the midpoint (Tm) is The meter according to claim 1, characterized in that it is used for setting the scale of a meter. 3. A second surface is maintained at a different temperature than the first surface by means of a secondary fluid flow, the means controlling the second surface to maintain the surface at substantially the same temperature as the secondary fluid flow. The meter according to claim 1 or 2, characterized in that it is provided in conjunction with. 4. The first by means of closed system inlet and return channels 25, 26 through which heat is transferred in the system to or from the fluid flowing through the system.
4. A meter according to claim 3, characterized in that a main fluid flow and a secondary fluid flow are provided passing along the surface. 5 A body 21 having a relatively good thermal conductivity and a large surface area is in thermal contact with the second surface to maintain the second surface at substantially the same temperature as the secondary fluid flow temperature. 5. A meter according to claim 3 or 4, characterized in that the fluid flow is adapted to flow along the body. 6. Any one of claims 1 to 5, characterized in that the portion 23 of the bridge with relatively good thermal conductivity has a conductivity at least 10 times that of the portion 16 with relatively poor thermal conductivity. The meter listed in. 7 The first and second surfaces and the temperature bridge are formed by an annular disk; the disk has a relatively good thermal conductivity section 23 surrounded by a relatively poor thermal conductivity section 16. has;
A disk is disposed between the inlet 10 and the outlet 11 of the meter, and the fluid passing through the meter passes along the inner cylindrical surface of the relatively poorly conductive portion 23 of the disk 23; It is located in a chamber 18 defining a secondary fluid flow path that runs along the outer cylindrical surface of the disk, which outer surface extends along the second surface. 7. A meter according to any one of claims 3 to 6, characterized in that: 8 an annular disk or sheath 16 in which the outer part of the temperature bridge is made of a material with poor thermal conductivity compared to the material from which the inner part 23 of the disk is made;
8. A meter according to claim 7, characterized in that it is formed of 30. 9. A meter according to claim 7, characterized in that the disk 40 has a homogeneous structure, and the relatively poorly conductive portion 42 has a small cross section. 10 Large plate 21 with relatively good thermal conductivity
extends into the chamber 18 surrounding the annular disc and is in thermal contact with the outer cylindrical surface of the annular disc. or 1 term meter. 11. A meter according to claim 10, characterized in that the plate (21) forms a baffle for directing the secondary fluid flow through the chamber (18) and around the outer cylindrical surface of the annular disc. 12 The temperature measurement device 27 measures the temperature (Tm) at one point in the portion 23 of the disk with relatively good thermal conductivity.
12. A meter according to any one of claims 7 to 11, characterized in that it is arranged to measure. 13 that the temperature measuring device 47 is arranged to measure the temperature at a point on the temperature shunt 44, 45 extending between the first surface and the midpoint of the relatively conductive portion 41 of the temperature bridge; 12. A meter according to any one of claims 7 to 11. 14 A second annular disk 44 of relatively good thermal conductivity is positioned close to but remote from the temperature bridge 40, the inner cylindrical surface of the second disk 44 extending from the inlet 10 to the outlet 11. a second annular disk 44 is connected by a relatively thermally conductive link 45 to the midpoint of the relatively conductive portion 41 of the bridge; The measuring device 47 measures the temperature (Tm) at one point on the second disk 44.
14. The meter of claim 13, wherein the meter is arranged to measure. 15 The annular disks 23, 30 are made of a thermally insulating material to ensure that heat flows substantially radially from one circumferential surface to the other.
15. The meter according to claim 7, wherein the meter is provided on both sides of the meter. 16 One or more guard rings 14 are provided on both sides of the temperature bridge, alternating with insulating rings 13, which guard rings 14 at their inner cylindrical surface prevent the flow from the inlet 10 to the outlet 11. Claim 1 characterized in that they are exposed to fluid flow and are thermally connected at their outer cylindrical surface to sheaths 17 made of a material with relatively good thermal conductivity. 15 item meter. 17 Any one of claims 1 to 16
meter, which is constructed to be connected across the inlet and return channels 25, 26 of the closed system, so that a fluid at one temperature flows along the first surface and a fluid at a different temperature flows along the first surface. fluid is second
flow meter along the surface and processing means for calculating the heat received or transferred by the fluid flowing through the system from the measured flow rate and the temperature difference between the inlet and return channels 25, 26; Calorimeter for measuring the amount of heat supplied by or to a fluid flowing through a closed system, characterized in that it has: