GB2308192A - Liquid-sensing apparatus - Google Patents

Liquid-sensing apparatus Download PDF

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Publication number
GB2308192A
GB2308192A GB9525488A GB9525488A GB2308192A GB 2308192 A GB2308192 A GB 2308192A GB 9525488 A GB9525488 A GB 9525488A GB 9525488 A GB9525488 A GB 9525488A GB 2308192 A GB2308192 A GB 2308192A
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GB
United Kingdom
Prior art keywords
liquid
sensing apparatus
apparatus according
tube
tube wall
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.)
Withdrawn
Application number
GB9525488A
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GB9525488D0 (en
Inventor
John Michael Walmsley Lawrence
John Frederick Harkness
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.)
JTL Systems Ltd
Original Assignee
JTL Systems 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 JTL Systems Ltd filed Critical JTL Systems Ltd
Priority to GB9525488A priority Critical patent/GB2308192A/en
Publication of GB9525488D0 publication Critical patent/GB9525488D0/en
Priority claimed from US08/673,723 external-priority patent/US5691466A/en
Publication of GB2308192A publication Critical patent/GB2308192A/en
Application status is Withdrawn legal-status Critical

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00Investigating or analysing materials by the use of electric, electro-chemical, or magnetic means
    • G01N27/02Investigating or analysing materials by the use of electric, electro-chemical, or magnetic means by investigating the impedance of the material
    • G01N27/04Investigating or analysing materials by the use of electric, electro-chemical, or magnetic means by investigating the impedance of the material by investigating resistance
    • G01N27/14Investigating or analysing materials by the use of electric, electro-chemical, or magnetic means by investigating the impedance of the material by investigating resistance of an electrically-heated body in dependence upon change of temperature
    • G01N27/18Investigating or analysing materials by the use of electric, electro-chemical, or magnetic means by investigating the impedance of the material by investigating resistance of an electrically-heated body in dependence upon change of temperature caused by changes in the thermal conductivity of a surrounding material to be tested

Description

LIOUID-SENSING APPARATUS This invention relates to a liquid-sensing apparatus, suitable in particular, although not exclusively, for detecting a liquid component in the fluid output of an evaporator.

Commercial refrigeration systems use the vapour compression cycle, in which the removal of heat relies on evaporation. A liquid refrigerant turns into gas in an evaporator, and in the process of doing so absorbs heat. The gas turns back into liquid in a condenser, and in the process of doing so releases heat in a location removed from that of the evaporator. The refrigerant fluid is pumped around a circuit connecting the evaporator and the condenser by a motor-driven pump or compressor. An expansion valve serves to control or meter the rate at which the liquid refrigerant enters the evaporator. The system has a low pressure side and a high pressure side. The gas coming out of the evaporator and entering the compressor is at a relatively low pressure, whereas the gas coming out of the compressor and entering the condenser is at a relatively high pressure.The liquid coming out of the condenser is at the same high pressure. Thus, a pressure difference exists across the compressor and also across the expansion valve.

The efficiency of the system is dependent upon the amount of work done by the compressor, which itself is related to the size of the pressure difference between the high pressure side and the low pressure side of the system. In order to optimize the efficiency, the condensing pressure should be as low as possible and the evaporating pressure should be as high as possible. This is because the smaller is the pressure difference across the compressor, the greater is the amount of fluid pumped by the compressor per unit time. Thus, the difference in pressure between the high pressure side and the low pressure side of the system should be minimized.

For effective use of the evaporator, the proportion of the total length of the evaporator pipe in which the liquid is present so that evaporation can occur, should be as large as possible. However, the refrigerant at the outlet normally needs to be kept totally gaseous, since if liquid or mist enters the compressor damage is likely to result. The amount by which the fluid output of the evaporator is hotter than necessary to be gaseous is known as the superheat. This can be defined as the temperature of the gas at the evaporator outlet minus the saturated vapour temperature corresponding to the gas pressure at the outlet. In other words, the superheat is the amount by which the temperature of the gas exceeds the boiling point of the liquid at the particular pressure.

Ideally, the superheat should be maintained at practically zero degrees, but normally it is controlled within a small range of values having a predetermined minimum level a few degrees above zero.

The superheat is controlled by means of the expansion valve at the evaporator inlet. If there is no superheat, the rate of liquid flow into the evaporator should be reduced. If there is too much superheat, the rate can be increased.

For the type of commercial refrigeration cabinets found in supermarkets and other stores, a thermostatic expansion valve has been traditionally used as the control device at the inlet of the evaporator. One significant disadvantage of using a thermostatic expansion valve is that the operation of the valve relies on the pressure of the liquid from the condenser. Thus, for this type of expansion valve to work a relatively high pressure difference across the valve is required. This makes greater the amount of work that needs to be done by the compressor, thereby reducing the efficiency.

More recently, it has been proposed to replace the traditional thermostatic expansion valve with an electrically-controlled one. The use of such an electrically-actuated expansion valve has a number of attractions. Perhaps the greatest is the potential for energy saving. As compared with the thermostatic version, the electric expansion valve requires only a small pressure drop across it to operate. This means that a lower condensing pressure and temperature can be adopted, enabling the compressor to pump a greater quantity of refrigerant per unit of electricity used, and thereby operate more efficiently.

Despite this potential benefit, refrigeration systems incorporating electronic control of the refrigerant flow have gained only a limited share of the market to date. One of the key reasons is that many of the proposed designs cannot satisfactorily detect an absence of superheat, and are therefore prone to malfunction or failure due to the resultant flooding and damage of the compressor.

Accordingly, there is a need for a liquid-sensing apparatus capable of reliably and speedily detecting the onset of liquid in a fluid which is normally in the gas state. Needless to say, such a liquid-sensing apparatus will find useful application in a wide variety of situations other than that specifically described above by way of illustration, in which maintaining a gaseous environment is important.

The present invention provides a liquid-sensing apparatus for sensing liquid in a flow of fluid, the apparatus comprising a tube through which, in use, the fluid flows, a first temperature sensor and a heating means each mounted on a first portion of the tube wall, a second temperature sensor mounted on a second portion of the tube wall, and means thermally isolating the two portions of the tube wall from each other.

According to the invention, the presence of liquid in the fluid flowing through the tube is detected using two temperature sensors mounted on the tube wall. One of the temperature sensors is deliberately heated above the surrounding gas temperature, while the other temperature sensor serves to provide a reference measurement. A difference in the temperatures sensed by the two temperature sensors is monitored. When liquid appears and makes contact with the heated wall portion, the heat supplied by the heating means is consumed as the latent heat of evaporation in converting the liquid to gas, thus causing a detectable fall in the monitored temperature difference between the two sensors. The provision of means for thermally isolating the respective tube wall portions on which the two sensors are mounted ensures that a fast and reliable response to the detection of liquid is achieved.

In a preferred application, the apparatus is connected to the outlet of an evaporator in a heat exchange system such as a refrigeration or air conditioning equipment. For example, the tube of the apparatus may replace or be connected in series with the suction pipe connecting the evaporator output to a compressor. This arrangement offers a simple, yet highly effective way of preventing a wet fluid output from damaging the compressor. Moreover, the size of the temperature change is dependent on the amount of liquid. This provides the advantage of being able to determine not just the absence of superheat in the fluid output but also its degree of wetness. A small amount of liquid at the evaporator outlet may be tolerable by virtue of the length of the suction pipe.

Thus, a threshold may be set for taking action when the amount of liquid exceeds the tolerable or a desirable upper limit.

In a preferred implementation of the invention, at least one of the two tube wall portions is thermally isolated from the main portion of the tube by means of a surrounding plurality of apertures, preferably in the form of elongate slots. The two tube wall portions may be disposed adjacent each other with one or more apertures or slots providing thermal isolation therebetween. Alternatively, the two portions are disposed on opposing sides of the tube, for example in diametrically opposing positions on a circular pipe. In each case, all of the apertures or slots are sealed so as to maintain the fluid-tight environment of the tube. The sealing means is suitably a plastic moulding which surrounds the pipe.

Thermally isolating the heated wall portion is especially advantageous in removing any heat-sinking effect of the surrounding wall. This means that a small, low power heating resistor, for example 1W, may be used. Moreover, the speed of response in liquid detection and of recovery thereafter becomes higher.

In a preferred arrangement, one or both of the sensor portions is arranged to project inwardly of the tube. More preferably, the or each portion is inclined with respect to the longitudinal axis of the tube so as to face the oncoming fluid flow. These arrangements further improve the speed and effectiveness of the response, although they are not essential to achieving the object of the invention.

The invention is more fully explained and illustrated, although not limited, by the following description with reference to the accompanying drawings, in which: Figures 1 to 3 are schematic, simplified views of a liquid-sensing apparatus according to a first embodiment of the invention, in which Figure 2 is a plan view, Figure 1 is a sectional view on line A-A of Figure 2 and Figure 3 is a sectional view on line B-B of Figure 1; Figures 4 to 6 are schematic, simplified views of a liquid-sensing apparatus according to a second embodiment of the invention, in which Figure 5 is a plan view, Figure 4 is a sectional view on line C-C of Figure 5 and Figure 6 is a sectional view on line D-D of Figure 4;; Figures 7 and 8 are schematic simplified drawings of a liquid-sensing apparatus according to a third embodiment of the invention, in which Figure 7 is a side sectional view and Figure 8 is a transverse sectional view on line E-E of Figure 7.

Referring to Figures 1 to 3, a first embodiment will be described.

The apparatus comprises principally a tube 10 and a number of components 14 to 16 mounted on the tube, externally thereof. The components consist of a first temperature sensor 15, an electrical heating element 16 mounted adjacent the sensor 15, and a second temperature sensor 14. In this embodiment the two temperature sensors 14, 15 are each temperature dependent resistors or thermistors, whereas the heating element 16 is an electrical resistor. The thermistor 15 and heating resistor 16 are mounted side-by-side on a first portion or member 13 of the tube wall. The other thermistor 14 is mounted on a second portion or member 12 of the tube wall, diametrically opposing the first portion. The tube 10 is made of a material having a good thermal conductivity, preferably a metal or metal alloy. In this embodiment a copper tube is used.

In operation, a fluid which is normally in the gas state flows through the tube 10 in a direction indicated generally by the arrows 11 in Figure 1.

Both of the thermistors 14, 15 are responsive to the temperature of the fluid flowing past the members 12, 13. In a wholly gaseous fluid, the member 12 will acquire substantially the gas temperature and this temperature is sensed by the thermistor 14. On the other hand, the member 13 will acquire a temperature higher than the gas temperature due to the heating effect of the resistor 16, and this higher temperature is sensed by the thermistor 15.

Thus, when the fluid is gas only and contains no liquid component, there will exist a definite temperature difference between the temperatures sensed by the sensors 14, 15, the difference being determined practically by the magnitude of the current supplied to the heating resistor 16. The difference between the two sensed temperatures is of the order of a few degrees Celsius. In this embodiment, the temperature difference is monitored by a detection means comprising a comparator (not shown). The comparator may be incorporated in the apparatus itself, but it is conveniently provided in external circuitry. The detection means is readily implemented using electronic components with which the skilled person is familiar.

When liquid appears in the fluid flowing through the tube, the liquid comes into contact with the heated wall portion 13 of a temperature exceeding that of the fluid. The effect of this contact is that the liquid immediately vaporises, the heated portion 13 providing the necessary latent heat for the change of state. The vaporisation of the liquid is manifest by a rapid or sudden lowering of the temperature of the portion 13, which is detected by the thermistor 15.

Thus, by monitoring the difference between the temperatures sensed by the thermistors 14 and 15, the occurrence of liquid in the fluid flow can be quickly and reliably established by detecting the corresponding lowering of the temperature difference.

For example, the detection may be achieved by setting a threshold for the output of the comparator: if the output level, corresponding to the temperature difference, falls below the threshold (for example, instantaneously or for a predetermined period), an output signal indicating liquid detection is generated.

The size of the temperature difference is dependent on the amount of liquid, i.e. the ratio of liquid to gas in the fluid being monitored. Thus, it is possible to set the threshold for detection at a level which corresponds to a particular degree of wetness which needs to be checked. This is an advantageous development.

In accordance with a feature of this invention, the two portions 12, 13 of the tube wall on which the sensing components 14 to 16 are mounted, are substantially thermally isolated from each other.

That is to say the apparatus includes means deliberately provided for substantially hindering the transmission of heat from the heated portion to the unheated portion, of the tube wall. The manner in which this thermal isolation is achieved in the present embodiment will now be described.

Each of the sensor-mounting portions 12, 13 consist of a generally rectangular portion of the tube wall which is isolated from the rest of the tube by a surrounding plurality of apertures in the tube wall, here in the form of four elongate slots 17. These slots 17 are best seen in Figure 2 in respect of the heated wall portion 13. The unheated wall portion 12 is similarly formed. This arrangement results in the portion 12, 13 being attached to the remainder of the tube merely at its corners in a structure which resembles a web. The form or shape, number and extent of the apertures or slots may be varied in many ways.

Indeed, there may even be just one slot, for example extending around three sides of the sensor portion in a substantially U-shaped configuration. The overall amount of the tube wall which is removed naturally determines the degree of thermal isolation of the sensor portion.

In this embodiment, in addition to having the isolating slots 17, the two sensor portions 12, 13 are arranged so as to project into the body of the tube, as seen in Figure 1. This projection is done by forming two bends 18, 19 in the tube, before and after each sensor portion as seen in the general fluid flow direction 11.

Preferably, the second bend 19 is made more shallow than the first bend 18, whereby the sensor portion is inclined toward the oncoming fluid flow (to the left in Figure 1). This will improve the detection sensitivity, although the same effect may be achieved by creating some turbulence in the fluid flow adjacent the sensor portion.

The above-described structure of the tube 10 is conveniently realised by first punching the slots 17, and then performing a pressing operation to form the bends 18, 19. A ductile material such as copper for the tube wall makes these operations practical.

In order to maintain the tube fluid-tight, the apertures must all be carefully sealed by means of a suitable sealant. The choice of material for the sealant will depend on a number of factors, including the range of operating pressure, the chemical nature of the fluid and the material of the tube itself. In this embodiment, the slots 17 are sealed by means of a moulding of plastics material, which is moulded in situ so as to surround the pipe. The moulding material, for example nylon, is injected externally through the slots 17 and sets to form sealing lips 22, 23 internally of the pipe.

The moulding 20 has a secondary function of strengthening the pipe, which is inevitably weakened by the presence of the slots 17 and the bends 18, 19.

Thus, the pipe is strengthened, the sensor portions supported and the slots 17 sealed, all by means of the moulding 20. Additionally, the moulding 20 includes cavities 21 in which the sensor portions of the tube wall are exposed for mounting of the components 14 to 16. Once these components have been fitted, the cavities 21 may be filled with potting compound and set, the wiring to the components (not shown) being extracted through the potting compound at the opening of the cavity 21. Before the cavity is potted, the components and the wall portions should be coated with heat-sinking compound to improve the thermal transmission performance.

A second embodiment of the invention will now be described with reference to Figures 4 to 6. In these drawings, like reference numerals denote parts which are the same as or corresponding to those of the first embodiment. Such components will not be described again in detail.

The second embodiment differs principally from the first embodiment in that the two wall portions 25, 27 on which the sensor components are mounted are arranged side-by-side, as compared with the opposing wall portions 12, 13 of the first embodiment. This simplifies the fabrication in terms of the structures of the pipe 10 and the moulding 20, and in that the wiring to the three components 14 to 16 may be extracted at a single location. As in the first embodiment, each sensor portion 25, 27 is bounded by a plurality of elongate slots 17. However, in this embodiment, the two portions share a common dividing slot 26 extending generally in the fluid flow direction. Again, the arrangement of the slots may be varied in many ways.However, it is preferable that the one or more slots 26 which separate the two sensor portions 25, 27 cover substantially the full length of the portions, in view of their mutual proximity.

Additionally, the moulding 22 may include a partitioning wall 24 within the cavity 21, the low thermal conductivity of the moulding improving the thermal isolation.

In the second embodiment, as seen in Figure 5, the two sensor portions 25, 27 of the tube wall are separated by a slot 26 extending in the direction of the tube axis. Although this is a preferred arrangement, the two portions 25, 27 may alternatively be separated by a dividing slot or slots extending in another direction such as transverse the tube, in which case the sensor components 14 to 16 may be mounted in the orientation shown in the first embodiment.

In the above-described embodiments, each of the wall portions 12, 13, 25, 27 is arranged so as to project into the body of the tube 10, and moreover is inclined so as to face the incoming fluid flow.

However, although preferred, none of these features is essential, since mutually isolated portions of the basic tube wall would still be disposed in and responsive to the passing fluid flow. Furthermore, it is possible to omit the slots 17 which isolate the portion 12 or 27 having the unheated sensor 14. The isolation of the heated portion 13 or 25 is the more significant, since it serves to alleviate the local heat-sinking effect of the surrounding tube, thereby allowing the use of a lower power heating resistor 16 and ensuring the availability of heat for rapid supply of the latent heat of evaporation when liquid contacts the heated portion. In the case of the second embodiment, if the surrounding slots 17 are omitted, the one or more slots 26 which thermally isolate the unheated portion 27 from the heated portion 25 should be maintained.

Figures 7 and 8 illustrate a third embodiment of the invention. In these drawings, like reference numerals denote parts which are the same as or corresponding to those of the first and second embodiments. Such components will not be described again in detail.

This embodiment differs from the previous two embodiments in that the sensing components 14 to 16 are mounted inside the pipe 10 so as to be disposed in the fluid flow 11. Specifically, the thermistor 15 and resistor 16 are housed together in a first cylindrical housing 29 and the thermistor 14 is housed in a second cylindrical housing 30. The two members 29, 30 should be made of a material offering good thermal conductivity. In this embodiment, the housings, like the tube 10, are made of copper.

The cylindrical housings 29, 30 extend into the tube 10 through a hole 34 in the tube wall, thereby enabling the lead wirings 32 to be extracted. In order to thermally isolate the two cylinders from the pipe wall, the cylinders are mounted in a moulding 28 of plastics material, for example nylon, contained within the pipe. The moulding provides respective holes for the entry of the cylinders, the surrounding aperture 34 in the pipe wall being larger so as to avoid thermal contact between each cylinder and the wall. The structure is potted or sealed at the entrance in order to maintain the pipe fluid-tight.

The moulding 28 contains an optional partitioning wall 31 between the cylinders 29, 30 for improving the thermal isolation. The thermal contact between each cylinder and the sensing component(s) housed therein is enhanced by the application of heat-sinking compound.

The moulding 28 may be inserted longitudinally into the pipe 10 in fabrication of the apparatus.

Preferably, however, the pipe is formed in situ around the moulding 28, suitably by a spinning process. This makes for a greater pressure tolerance of the final structure, which is advantageous in a refrigeration application. The moulding 28 may be flat-walled at the top or bottom as shown in Figure 8, in which case the pipe 10 has a similar conforming flat section 33 (Figure 7).

The operation of the apparatus is the same as for the first and second embodiments. The cylinder 29 acquires a higher temperature than the cylinder 30 by virtue of the heating resistor 16. The thermal isolation of the heated cylinder 29 from the pipe wall provides for quick evaporation of liquid upon its arrival, and thus a good speed of response. The thermal isolation of the unheated cylinder 30 from the pipe wall is less important, as in the earlier embodiments. Thus, if desired, the unheated cylinder 30 may be in thermal contact with the pipe 10.

The above embodiments utilize the difference between the temperatures sensed by two temperature sensors, the heating means associated with one of the sensors. However, it will be appreciated that the principle on which the liquid-detection operation is based relies essentially on the fall in the temperature detected by the heated sensor. Thus, the unheated sensor 14 may be dispensed with in a modification of the above embodiments. In this case, the wall portion, housing or member on which the heated sensor 15 is mounted should be thermally isolated from the tube wall. In this modification, the presence of liquid is detected by differentiating the output of the one temperature sensor with respect to time.If the value of the differential exceeds a predetermined threshold, indicating a fall in temperature sufficiently rapid to be due to the consumption of the latent heat of evaporation, it is established that liquid is present and a control signal to that effect may be generated.

The apparatus employing two temperature sensors, however, has the advantage that it is comparatively easy to monitor a difference in two temperatures, and the difference is virtually immune to external influences, which are cancelled out.

The invention may be embodied in other specific forms and manners without departure from the scope thereof. It is preferable, though not essential that the components 15, 16 be mounted adjacent each other.

Alternatively, the heater and the associated temperature sensor may be integrated or consist of a single component such as a self-heating thermistor.

The cross-sectional shape of the tube 10 is immaterial to the operation of the apparatus.

Thus, the invention provides an apparatus for speedily and reliably detecting the onset of a liquid component in a gas flow. In the context of a heat exchange system, the apparatus may be fitted so as to monitor the fluid flow from the output of an evaporator. The apparatus may then be used as a safety device for generating a warning that liquid is emerging from the evaporator (whether a thermostatic or electronic expansion valve is employed at the evaporator inlet). Alternatively, the apparatus may be used to operate a control regime in which substantially zero superheat is maintained at the evaporator outlet. Furthermore, it is possible to monitor the degree of wetness of the fluid output.

Claims (20)

1. A liquid-sensing apparatus for sensing liquid in a flow of fluid, the apparatus comprising a tube through which, in use, the fluid flows, a first temperature sensor and a heating means each mounted on a first portion of the tube wall, a second temperature sensor mounted on a second portion of the tube wall, and means thermally isolating said two portions of the tube wall from each other.
2. A liquid-sensing apparatus according to claim 1, wherein said isolating means comprises at least one aperture formed in the tube wall around the first portion.
3. A liquid-sensing apparatus according to claim 1 or claim 2, wherein said isolating means comprises at least one aperture formed in the tube wall around the second portion.
4. A liquid-sensing apparatus according to claim 2 or claim 3, wherein said at least one aperture comprises a plurality of elongate slots.
5. A liquid-sensing apparatus according to any one of claims 2 to 4, further comprising means sealing the tube at the or each said aperture.
6. A liquid-sensing apparatus according to claim 5, wherein said sealing means is a moulding formed around the tube.
7. A liquid-sensing apparatus according to any one of claims 1 to 6, wherein said first and second portions of the tube wall are formed opposing each other.
8. A liquid-sensing apparatus according to any one of claims 1 to 6, wherein said first and second portions of the tube wall are formed adjacent each other.
9. A liquid-sensing apparatus according to any one of the preceding claims, wherein at least one of said first and second portions of the tube wall comprises a substantially rectangular portion of the tube wall.
10. A liquid-sensing apparatus according to any one of the preceding claims, wherein at least one of said first and second portions is arranged to project into the body of the tube.
11. A liquid-sensing apparatus according to claim 10, wherein the projecting said portion is inclined with respect to the fluid flow direction through the tube.
12. A liquid-sensing apparatus according to claim 1, wherein said isolating means comprises at least one aperture in the tube wall, separating said first and second portions.
13. A liquid-sensing apparatus for sensing liquid in a flow of fluid, the apparatus comprising a tube through which, in use, the fluid flows, a first temperature sensor and a heating means each mounted on a first thermally-conductive member, and a second temperature sensor mounted on a second thermallyconductive member, said two members arranged so as to be disposed in the fluid flow, wherein said first member is thermally isolated from the tube wall.
14. A liquid-sensing apparatus according to claim 13, wherein said second member is thermally isolated from the tube wall.
15. A liquid-sensing apparatus according to claim 13 or claim 14, wherein said first and second members are disposed within a moulding contained within the tube.
16. A liquid-sensing apparatus according to claim 15, wherein the tube is formed in situ around the moulding.
17. A liquid-sensing apparatus according to any one of the preceding claims, further comprising detection means responsive to change in a difference in the temperatures sensed by the two temperature sensors.
18. A liquid-sensing apparatus according to claim 17, wherein the detection means is arranged to generate a signal when the temperature difference falls below a predetermined threshold value.
19. A liquid-sensing apparatus substantially as hereinbefore described with reference to Figures 1 to 3 or Figures 4 to 6, of the accompanying drawings.
20. A liquid-sensing apparatus substantially as hereinbefore described with reference to Figures 7 and 8 of the accompanying drawings.
GB9525488A 1995-12-14 1995-12-14 Liquid-sensing apparatus Withdrawn GB2308192A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9525488A GB2308192A (en) 1995-12-14 1995-12-14 Liquid-sensing apparatus

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9525488A GB2308192A (en) 1995-12-14 1995-12-14 Liquid-sensing apparatus
US08/673,723 US5691466A (en) 1995-06-28 1996-06-26 Liquid-sensing apparatus and method
EP96304788A EP0751391A1 (en) 1995-06-28 1996-06-28 Liquid-sensing apparatus and method

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Publication Number Publication Date
GB9525488D0 GB9525488D0 (en) 1996-02-14
GB2308192A true GB2308192A (en) 1997-06-18

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0816783A2 (en) 1996-07-05 1998-01-07 J T L Systems Ltd. Defrost control method and apparatus
DE102008022363A1 (en) * 2008-05-06 2009-12-03 Areva Np Gmbh Method and device for monitoring the level of a liquid in a liquid container

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Publication number Priority date Publication date Assignee Title
US4167858A (en) * 1976-10-27 1979-09-18 Nippondenso Co., Ltd. Refrigerant deficiency detecting apparatus
GB2143950A (en) * 1981-06-29 1985-02-20 Malcolm M Mcqueen Fluid vessel sensor
EP0210509A1 (en) * 1985-08-02 1987-02-04 Schmidt Feintechnik Gmbh Method for measuring the properties of a fluid, and sensor element for carrying out this method
GB2181257A (en) * 1983-10-08 1987-04-15 Plessey Co Plc A probe for use in a device for measuring the liquid content of a gas
US5044764A (en) * 1989-03-08 1991-09-03 Snow Brand Milk Products Co., Ltd. Method and apparatus for fluid state determination
EP0485185A1 (en) * 1990-11-09 1992-05-13 Sanden Corporation Sensor and control system for an automotive air conditioning system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4167858A (en) * 1976-10-27 1979-09-18 Nippondenso Co., Ltd. Refrigerant deficiency detecting apparatus
GB2143950A (en) * 1981-06-29 1985-02-20 Malcolm M Mcqueen Fluid vessel sensor
GB2181257A (en) * 1983-10-08 1987-04-15 Plessey Co Plc A probe for use in a device for measuring the liquid content of a gas
EP0210509A1 (en) * 1985-08-02 1987-02-04 Schmidt Feintechnik Gmbh Method for measuring the properties of a fluid, and sensor element for carrying out this method
US5044764A (en) * 1989-03-08 1991-09-03 Snow Brand Milk Products Co., Ltd. Method and apparatus for fluid state determination
EP0485185A1 (en) * 1990-11-09 1992-05-13 Sanden Corporation Sensor and control system for an automotive air conditioning system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0816783A2 (en) 1996-07-05 1998-01-07 J T L Systems Ltd. Defrost control method and apparatus
US5813242A (en) * 1996-07-05 1998-09-29 Jtl Systems Limited Defrost control method and apparatus
DE102008022363A1 (en) * 2008-05-06 2009-12-03 Areva Np Gmbh Method and device for monitoring the level of a liquid in a liquid container
DE102008022363B4 (en) * 2008-05-06 2012-01-19 Areva Np Gmbh Method and device for monitoring the level of a liquid in a liquid container
US8616053B2 (en) 2008-05-06 2013-12-31 Areva Gmbh Method and device for monitoring the fill level of a liquid in a liquid container

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