GB2309786A - Measuring temperature and pressure of a fluid across a valve - Google Patents

Measuring temperature and pressure of a fluid across a valve Download PDF

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Publication number
GB2309786A
GB2309786A GB9602023A GB9602023A GB2309786A GB 2309786 A GB2309786 A GB 2309786A GB 9602023 A GB9602023 A GB 9602023A GB 9602023 A GB9602023 A GB 9602023A GB 2309786 A GB2309786 A GB 2309786A
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GB
United Kingdom
Prior art keywords
valve
temperature
pressure
valve stem
fluid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9602023A
Other versions
GB9602023D0 (en
GB2309786B (en
Inventor
Russell Benstead
William George Cowen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EA Technology Ltd
Original Assignee
EA Technology Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by EA Technology Ltd filed Critical EA Technology Ltd
Priority to GB9602023A priority Critical patent/GB2309786B/en
Publication of GB9602023D0 publication Critical patent/GB9602023D0/en
Publication of GB2309786A publication Critical patent/GB2309786A/en
Application granted granted Critical
Publication of GB2309786B publication Critical patent/GB2309786B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L19/00—Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or accessories are not special to particular types of pressure gauges
    • G01L19/0092—Pressure sensor associated with other sensors, e.g. for measuring acceleration or temperature
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D21/00—Measuring or testing not otherwise provided for
    • G01D21/02—Measuring two or more variables by means not covered by a single other subclass
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K13/00—Thermometers specially adapted for specific purposes
    • G01K13/02—Thermometers specially adapted for specific purposes for measuring temperature of moving fluids or granular materials capable of flow

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Indication Of The Valve Opening Or Closing Status (AREA)

Abstract

An instrument 10 designed to be coupled to a Schraeder valve 1 (e.g. in a refrigeration system) to measure the pressure of fluid within the system and having a contact part 12 to depress the stem 4 of the Schraeder valve when the coupling is effected, thus allowing the system fluid to reach a pressure transducer 14, is additionally provided with means to measure the temperature of the Schraeder valve stem 4, which equates to the temperature of the system fluid. As shown a temperature transducer is provided on the contact part 12 but an alternative arrangement is described in which a thermocouple (41, Fig. 3) is fitted at the inner end of the Schraeder valve stem 4. The instrument can include a calculator to calculate the superheat or sub-cooling of the fluid from the measured temperature and pressure values.

Description

A METHOD AND SENSOR FOR MEASURING TEMPERATURE AND PRESSURE OF A FLUID ACROSS A VALVE The present invention generally relates to a method and sensor for measuring the temperature and pressure of a fluid across a valve and more particularly to a method and sensor which is able to simultaneously measure the temperature and pressure of a fluid across a valve which has a valve stem extending therethrough.
To measure if a refrigeration system is operating satisfactorily, one usually needs to know both the temperature and pressure of the refrigerant. This will then allow one to calculate the level of superheating (which is the amount that the refrigerant temperature is above the saturation, or dew point, temperature corresponding to the refrigerant pressure) or to calculate the level of sub cooling (which is the amount which the refrigerant temperature is below the saturation, or bubble point, temperature corresponding to the refrigerant pressure).
Typically the measurement of the temperature and pressure of the refrigerant is achieved using a separate pressure gauge and a pipe surface temperature measurement. The operator then needs to use a set of tables to convert these readings into a superheat level or sub cooling level. As the number of refrigerants in use increases, due to the phasing out of CFCs and HCFCs, more and more sets of tables are required. It is therefore desirable to reduce the skill level required and allow staff other than refrigeration engineers and technicians to take readings and interpret them.
Another problem is the control of superheat at the exit from the condenser. This is achieved in electronically controlled valves by measuring the temperature at each side of the evaporator and controlling the difference between the two readings.
However, an allowance has to be made for the pressure drop through the evaporator and this leads to imperfect control.
It is therefore an object of the present invention to provide a more accurate method of simultaneously measuring temperature and pressure of a fluid across a valve.
The present invention provides a method of measuring the temperature and pressure of a fluid across a valve having a valve stem extending therethrough, comprising the steps of fitting a pressure transducer arrangement to said valve, depressing said valve stem and simultaneously measuring the pressure of the fluid and the temperature of said valve stem.
In one embodiment the valve stem has a temperature sensing arrangement incorporated therein and when the valve stem is depressed, electrical contact is made between the sensor and the temperature sensing arrangement. This arrangement has the advantage that the temperature sensing is made closer to the fluid on the inside of the valve. The disadvantage of this arrangement is however that electrical contacts are required between the valve stem and the sensor head to enable the temperature to be measured and displayed.
In an alternative embodiment of the present invention a valve stem contact face includes the temperature transducer arrangement such that when it contacts the valve stem to depress it, thermal contact is made to allow the measurement of the temperature of the valve stem which can be considered to be almost identical to the temperature of the fluid.
Thus in accordance with one embodiment of the present invention there is provided sensor for measuring the temperature and pressure of a fluid across a valve having a thermally conductive valve stem extending therethrough, the sensor comprising a pressure resistant housing having an opening for coupling said housing to said valve and a sealing arrangement arranged at said opening for sealing the interface between said valve and said housing when coupled, a valve stem contact arranged within said housing for contacting and depressing said valve stem when said housing is coupled to said valve, pressure transducer means for measuring the pressure of the fluid within said housing, and temperature transducer means arranged in said valve stem contact for measuring the temperature of the fluid by measuring the temperature of said valve stem In accordance with a second embodiment of the present invention there is provided a sensing arrangement for measuring the temperature and pressure of a fluid, the sensor comprising a valve having a valve stem extending therethrough, a temperature transducer arrangement in said valve stem for measuring the temperature of the fluid by measuring the temperature of said valve stem, a housing having an opening for coupling said housing to said valve and a sealing arrangement arranged at said opening for sealing the interface between said valve and said housing when coupled, a valve stem contact arranged within said housing for contacting and depressing said valve stem when said housing is coupled to said valve and for making electrical contact with said temperature transducer arrangement, and pressure transducer means for measuring the pressure of the fluid within said housing.
In order to provide automatic calculation and display of the level of superheat or sub cooling, preferably the present invention includes calculator means and display means. Conveniently a sensor includes at least one look-up table used in the calculation of the number of superheat or sub cooling.
The look-up tables can be the saturation table or for zeotropic refrigerants the bubble and dew point tables.
The present invention is particularly suited for use with Schraeder or similar valves and is not restricted to refrigeration systems.
Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a part sectional view through a Schraeder valve and a sensor head in accordance with one embodiment of the present invention before they are coupled together; Figure 2 is a part sectional view through the embodiment of Figure 1 after the Schraeder valve and the sensor head have been coupled together; and Figure 3 is a part sectional view through a modified Schraeder valve and sensor head in accordance with a second embodiment of the present invention with the two coupled together.
Referring now to the drawings, Figures 1 to 3 illustrate a combined pressure and temperature sensing head for a refrigeration system. In such systems the pressure measurement is usually taken from a Schraeder valve which comprises an access port on the refrigerant pipework. Such a valve 1 comprises a tubular body 2 having a male threaded portion 3 to allow gauges and other couplings to be coupled to the Schraeder valve 1. Within the Schraeder valve 1 there is an axial valve stem 4 extending from outside the opening 5 to within the housing 2. The valve stem 4 carries the valve seal 6 which seals with the valve face 7 when the valve is closed under the pressure of the refrigerant within the body 2 of the Schraeder valve 1. As can be seen in Figure 2, when the valve stem 4 is depressed to a position within the opening 5, the valve seal 6 moves away from the seal face 7 thus opening the valve and allowing the refrigerant to flow out coaxially with the valve stem 4 through a cylindrical channel through the valve face 7.
Thus conventionally in order to measure the temperature and pressure of the refrigerant within the Schraeder valve 1, a pressure gauge is attached to the opening 5 of the Schraeder valve 1 such that the valve stem 4 is depressed allowing the refrigerant to couple with the pressure gauge. The temperature is then measured simply by measuring the temperature of the pipe surface. This is however inaccurate and the present inventors have realised that a far more accurate method of measuring the temperature is to measure the temperature of the valve stem 4 simultaneously with measuring the pressure of the refrigerant gas.
In embodiments of Figures 1 and 2 this is achieved by providing a sensor 10 which couples with the Schraeder valve 1 such that a female threaded portion 11 couples with the male threaded portion 3 of the Schraeder valve 1. When the coupling is complete a valve stem contact 12 depresses the valve stem 4 thus opening the valve. The refrigerant gas is then free to flow down an annular cylindrical channel 13 into the pressure transducer cell 14. The pressure transducer cell 14 can then measure the pressure of the refrigerant and electrical signals are passed via connections 15a, 15b, 15c and 15d to an instrument for calculating the level of superheat or sub cooling or to display if the refrigerant is in the saturation region.
The valve stem contact 12 in this embodiment includes therein a temperature sensor such as a thermocouple such that when the valve stem contact 12 comes into thermal contact with the valve stem 4, the thermocouple or other sensor within the valve stem contact 12 measures the temperature of the valve stem.
The temperature of the valve stem has been found to be almost identical to the temperature of the refrigerant measured in the flow (+ 0.1K), which is far more accurate than the temperature obtained from measuring the surface temperature of the refrigerant pipework.
The thermocouple within the valve stem contact 12 is provided with electrical connections 16a and 16b which pass out of the sensor head 10 to the instrument where the temperature measurements can be used in the calculation of the level of superheat or sub cooling or to determine if the refrigerant is in the saturation region.
The measured temperature and pressure values provided by wires 15a, 15b, 15c, 15d, 16a and 16b can be passed to an instrument which contains the saturation table or zeotropic refrigerants the bubble and dew point tables. The instrument can use the tables to calculate the display the level of superheat or sub cooling or to indicate if the refrigerant is in the saturation region.
The sensor head 10 has the standard female thread portion 11 enabling it to be coupled to a conventional service valve. In such an arrangement the thermocouple in the valve stem contact 12 lies directly in the refrigerant gas stream and it is thus still able to measure the correct temperature.
The output of the sensor head 10 could be used to feed the controller for a valve regulating the flow of refrigerant into the controller for a valve regulating the flow of refrigerant into the evaporator of the refrigeration system. This avoids the problem of allowing for the refrigerant pressure drop in the evaporator when controlling an expansion valve from temperature readings. In this case, and in others when the temperature reading is required continuously, an alternative arrangement would be to use a temperature sensing element within the valve stem to measure the temperature of the refrigerant more directly. Such an arrangement is illustrated in Figure 3.
In Figure 3 like components to the embodiment of Figures 1 and 2 are referred to by like reference numerals. This embodiment differs from the embodiment illustrated in Figures 1 and 2 in that the valve stem 40 has arranged therein a temperature sensor such as a thermocouple 41. In this embodiment the thermocouple or other sensor is arranged at the end which extends directly into the refrigerant to provide the most accurate and rapidly responding temperature measurement. At the other end 42 of the valve stem 40 the electrical signal from the thermocouple 41 is fed from the valve stem 40 to electrical conductors 16a and 16b in the valve stem contact 12. These connections may be provided by spade connectors mounted on the end 42 of the valve stem 40, to which couplings on the conductors 16a and 16b are connected before the sensor 10 is coupled to the Schraeder valve. Other forms of connection, such as small coaxial plug contacts, can be envisaged.
This arrangement has the advantage that the temperature from the thermocouple 41 responds quicker to changes in the temperature of the refrigerant within the valve 1.
Although the present invention has been described hereinabove with reference to specific embodiments, it would be clear to a skilled person in the art that modifications can be made which fall within the scope of the claims. In particular, the present invention is not limited to the use of Schraeder valves, nor is it limited to use within refrigeration systems.

Claims (19)

1. A method of measuring the temperature and pressure of a fluid across a valve having a valve stem extending therethrough, comprising the steps of fitting a pressure transducer arrangement to said valve, depressing said valve stem and simultaneously measuring the pressure of the fluid and the temperature of said valve stem.
2. A method as claimed in Claim 1 wherein said valve stem has a temperature sensing arrangement arranged therein, and said step of depressing said valve stem includes the step of making electrical contact with said temperature sensing arrangement.
3. A method as claimed in Claim 2, wherein said temperature sensing arrangement comprises a thermocouple, and said step of making electrical contact comprises the step of making electrical contact with said thermocouple.
4. A method as claimed in Claim 1, including the step of fitting a temperature transducer arrangement to said valve such that said temperature transducer arrangement makes thermal contact with said valve stem.
5. A method as claimed in any preceding claim, including the step of calculating the level of superheat, or sub cooling, of the fluid from said measured temperature and pressure.
6. A method as claimed in Claim 5, wherein the level of superheat is calculated using look-up tables.
7. A method as claimed in any preceding claim, wherein said valve is a Schraeder valve.
8. A sensor for measuring the temperature and pressure of a fluid across a valve having a thermally conductive valve stem extending therethrough, the sensor comprising a pressure resistant housing having an opening for coupling said housing to said valve and a sealing arrangement arranged at said opening for sealing the interface between said valve and said housing when coupled, a valve stem contact arranged within said housing for contacting and depressing said valve stem when said housing is coupled to said valve, pressure transducer means for measuring the pressure of the fluid within said housing, and temperature transducer means arranged in said valve stem contact for measuring the temperature of the fluid by measuring the temperature of said valve stem
9. A sensor as claimed in Claim 8, wherein said temperature transducer means comprises a thermocouple.
10. A sensor as claimed in Claim 8 or Claim 9, wherein said valve is a Schraeder valve and said housing has a female threaded portion at said opening for coupling to a male threaded portion of said Schraeder valve.
11. A sensor as claimed in any one of Claims 8 to 10, including calculator means for receiving said measured temperature and pressure and for calculating the level of superheat or sub cooling of the fluid, and display means for displaying the calculated level of superheat or sub cooling.
12. A sensor as claimed in Claim 11, including at least one look-up table, said calculator means being adapted to use said measured temperature and pressure and a said look-up table to calculate the level of superheat or sub cooling.
13. A sensing arrangement for measuring the temperature and pressure of a fluid, the sensor comprising a valve having a valve stem extending therethrough, a temperature transducer arrangement in said valve stem for measuring the temperature of the fluid by measuring the temperature of said valve stem, a housing having an opening for coupling said housing to said valve and a sealing arrangement arranged at said opening for sealing the interface between said valve and said housing when coupled, a valve stem contact arranged within said housing for contacting and depressing said valve stem when said housing is coupled to said valve and for making electrical contact with said temperature transducer arrangement, and pressure transducer means for measuring the pressure of the fluid within said housing.
14. A sensing arrangement as claimed in Claim 13, wherein said transducer means comprises a thermocouple.
15. A sensing arrangement as claimed in Claim 13 or Claim 14, wherein said valve is a Schraeder valve and said housing has a female threaded portion at said opening for coupling to a male threaded portion of said Schraeder valve.
16. A sensing arrangement as claimed in any one of Claims 13 to 15, including calculator means for receiving said measured temperature and pressure and for calculating the level of superheat or sub cooling of the fluid, and display means for displaying the calculated level of superheat or sub cooling.
17. A sensing arrangement as claimed in Claim 16, including at least one look-up table, said calculator means being adapted to use said measured temperature and pressure and a said look-up table to calculate the level of superheat or sub cooling.
18. A sensor substantially as hereinbefore described with reference to and as illustrated in any of the accompanying drawings.
19. A method of measuring the temperature and pressure of a fluid substantially as hereinbefore described with reference to any of the accompanying drawings.
GB9602023A 1996-02-01 1996-02-01 A method and sensor for measuring temperature and pressure of a fluid across a valve Expired - Fee Related GB2309786B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9602023A GB2309786B (en) 1996-02-01 1996-02-01 A method and sensor for measuring temperature and pressure of a fluid across a valve

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9602023A GB2309786B (en) 1996-02-01 1996-02-01 A method and sensor for measuring temperature and pressure of a fluid across a valve

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GB9602023D0 GB9602023D0 (en) 1996-04-03
GB2309786A true GB2309786A (en) 1997-08-06
GB2309786B GB2309786B (en) 1999-10-13

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10232315A1 (en) * 2001-11-12 2003-05-22 Temperaturmestechnik Geraberg Combined temperature and pressure sensor for fluid systems has a rotationally symmetric base body, which is detachable for cleaning and maintenance, with central pressure and eccentric temperature measurement channels
GB2528175A (en) * 2014-07-07 2016-01-13 Idq Operating Inc Coupler and methods of use for assessment of refrigeration systems
EP4130699A1 (en) * 2021-08-05 2023-02-08 Automaatio-Center AC OY A pressure sensor for monitoring an expansion vessel

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0338101A1 (en) * 1988-04-19 1989-10-25 Kistler Instrumente AG Connector for recording apparatus
US5070706A (en) * 1990-07-10 1991-12-10 Sundstrand Corporation Superheat sensor with single coupling to fluid line
GB2250348A (en) * 1990-04-06 1992-06-03 Vetco Gray Inc Abb Integrated sensor-transducer device and pressure sensor-transducer

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0338101A1 (en) * 1988-04-19 1989-10-25 Kistler Instrumente AG Connector for recording apparatus
GB2250348A (en) * 1990-04-06 1992-06-03 Vetco Gray Inc Abb Integrated sensor-transducer device and pressure sensor-transducer
US5070706A (en) * 1990-07-10 1991-12-10 Sundstrand Corporation Superheat sensor with single coupling to fluid line

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10232315A1 (en) * 2001-11-12 2003-05-22 Temperaturmestechnik Geraberg Combined temperature and pressure sensor for fluid systems has a rotationally symmetric base body, which is detachable for cleaning and maintenance, with central pressure and eccentric temperature measurement channels
DE10232315B4 (en) * 2001-11-12 2009-05-28 Temperaturmeßtechnik Geraberg GmbH Combined temperature and pressure sensor and method for the determination of physical characteristics
GB2528175A (en) * 2014-07-07 2016-01-13 Idq Operating Inc Coupler and methods of use for assessment of refrigeration systems
GB2528175B (en) * 2014-07-07 2021-02-17 Energizer Auto Inc Coupler and methods of use for assessment of refrigeration systems
GB2587731A (en) * 2014-07-07 2021-04-07 Energizer Auto Inc Coupler and methods of use for assessment of refrigeration systems
GB2587731B (en) * 2014-07-07 2021-07-28 Energizer Auto Inc Coupler and methods of use for assessment of refrigeration systems
US11460366B2 (en) 2014-07-07 2022-10-04 Energizer Auto, Inc. Coupler and methods of use for assessment of refrigeration systems
EP4130699A1 (en) * 2021-08-05 2023-02-08 Automaatio-Center AC OY A pressure sensor for monitoring an expansion vessel

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Publication number Publication date
GB9602023D0 (en) 1996-04-03
GB2309786B (en) 1999-10-13

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 20010201