Patent Description:
The present invention generally relates to liquid delivery and dispensing processes and systems and, more particularly, to a liquid density measurement device, system and method.

Liquids that vaporize at or below ambient temperatures, such a cryogenic liquids, are used in a number of applications. Such liquids are typically stored in insulated containers and then dispensed or distributed for use by use devices or in industrial processes. Accurate metering and/or monitoring of the flow rates of the liquids as they are dispensed or delivered is important in many applications. Determining the density of the flowing liquid is necessary for accurate metering and monitoring of the liquid flow rate.

Challenges in measuring the density of flowing liquids are presented by cryogenic liquids due to the very low temperature of the liquids (cryogenic liquids boil at temperatures of -<NUM>°F/-<NUM>). For example, current technologies for measuring the density of flowing liquids include Resistance Temperature Devices (RTDs), which may encounter operational issues at liquid hydrogen temperatures. Cryogenic Platinum probes, another technology currently in use for flowing liquid density measurement, are not linear at hydrogen temperatures and require calibration. This calibration is challenging and expensive.

Additional challenges are presented if the cryogenic liquid is flammable (such as in the case of hydrogen), especially if electrical components are used for flowing liquid density measurement due to electrical code requirements.

Another technology, diode technologies, are used and very accurate but have the packaging challenges.

Furthermore, many of the prior art technologies used for flowing liquid density measurement are not robust.

<CIT> discloses a prior art system for determining a saturation pressure of a liquid.

The invention is defined by a system comprising the features of claim <NUM> and the corresponding method comprising the features of claim <NUM>. There are several aspects of the present subject matter which may be embodied separately or together in the devices and systems described and claimed below.

In one aspect, a probe assembly for determining a saturation pressure of a liquid includes a manifold having an internal passage. The probe also includes an elongated bulb defining a chamber with a distal tip portion and a proximal portion. The bulb is secured to the manifold at the proximal portion with the chamber in fluid communication with the internal passage. A charging port is selectively in fluid communication with the manifold. A pressure transmitter is configured to detect a pressure within the chamber of the elongated bulb.

In another aspect, a system for determining a saturation pressure of a liquid features a probe assembly including a manifold having an internal passage and an elongated bulb defining a chamber and including a distal tip portion and a proximal portion. The bulb is secured to the manifold by the proximal portion with the chamber containing a pressurized vapor. The chamber also is in fluid communication with the internal passage. A charging port is selectively in fluid communication with the manifold. A pressure transmitter is configured to detect a pressure within the chamber of the elongated bulb. The system also features a jacketed pipe assembly including a pipe defining a flow passage and a jacket surrounding the pipe so that a first annular space is formed, where the annular space is at least partially evacuated of air. The jacketed pipe assembly also includes a probe port to which the probe assembly is attached with the distal tip portion of the bulb positioned within the flow passage of the pipe.

In another aspect, a method for determining a saturation pressure of a liquid in a passage includes the steps of: placing an elongated bulb containing a pressurized vapor into the passage, wherein the vapor and the liquid are the same fluid, and detecting a pressure of the pressurized vapor after the bulb is placed within the passage.

An embodiment of the flowing liquid density measurement system is indicated in general at <NUM> in <FIG> and <FIG>. The system includes a probe assembly, indicated in general at <NUM> in <FIG> and <FIG>. While the embodiments are described below in terms of hydrogen as the flowing liquid, it is to be understood that embodiments of the disclosure may be used to measure the density of other flowing liquids, including both those that are cryogenic and those that are not cryogenic.

As illustrated in <FIG>, the probe <NUM> includes an elongated bulb, indicated in general at <NUM>. The bulb includes a distal tip portion <NUM> and a proximal portion <NUM>. The probe <NUM> also includes a manifold <NUM> to which the proximal portion of the bulb is attached. A vent valve <NUM> is also attached to the manifold <NUM> and, as an example only, may be a burst disk valve. A charging valve <NUM> having a charging port <NUM> is also attached to the manifold, as is a pressure transmitter <NUM>. The manifold <NUM> includes interior passages that are in fluid communication with each other as well as with the bulb <NUM>, vent valve <NUM>, charging valve <NUM> and charging port <NUM>.

A vacuum jacket pipe assembly, a portion of which is indicated in general at <NUM> in <FIG> and <FIG>, directs a stream of liquid from a source to a destination. As an example only, the source may be a vacuum storage tank and the destination may be a use device or an industrial process. The vacuum jacket pipe assembly <NUM> features an inner pipe <NUM> surrounded by a jacket <NUM>. The annular space <NUM> defined therebetween preferably contains a vacuum or is at a near vacuum pressure level. The inner pipe includes a flow passage <NUM>.

A port is formed in the vacuum jacket pipe assembly and includes an outer sleeve <NUM>, an inner sleeve <NUM> (<FIG>) and an end cap fitting <NUM> having a central opening that communicates with a port central bore (that is surrounded by inner sleeve <NUM>). The annular interior space <NUM> of the port between the inner sleeve <NUM> and the outer sleeve <NUM> is in fluid communication with the annular space <NUM> between the inner piper <NUM> and jacket <NUM>. As a result, the port interior space <NUM> is also at or near vacuum level so as to be well insulated.

The probe assembly <NUM> is installed in the vacuum jacket pipe assembly <NUM> by inserting the bulb <NUM> of the probe assembly into and through the central opening of the end cap fitting <NUM> and the central bore of the port until the distal tip portion <NUM> of the bulb is positioned within the flow passage <NUM> of the vacuum jacket pipe assembly <NUM>, as illustrated in <FIG>.

An attachment member <NUM> is provided on the manifold and engages the end cap fitting <NUM> of the port of the vacuum jacket piper assembly so that the port assembly <NUM> is removably secured to the jacket pipe assembly <NUM>. As an example only, the attachment member <NUM> of the probe assembly and the end cap fitting <NUM> of the vacuum jacket pipe assembly may include threads so that a threaded connection is formed.

In an alternative embodiment, the probe may be permanently installed with respect to the vacuum jacket pipe assembly with the distal tip portion <NUM> of the bulb positioned within the flow passage <NUM> of the vacuum jacket pipe assembly <NUM>. Such an embodiment eliminates the need for the outer and inner sleeves (<NUM> and <NUM>) as well as the end cap fitting <NUM>.

With reference to <FIG>, the bulb <NUM> includes a bulb chamber <NUM> that is pressurized. The bulb chamber <NUM> is in fluid communication with the passages of the manifold <NUM> of <FIG>. In the embodiment where hydrogen is the liquid that flows through the flow passage <NUM> of the pipe, the bulb chamber <NUM> contains hydrogen vapor. As an example only, the chamber <NUM> is pressurized to approximately <NUM> MPa (<NUM> psi). In alternative embodiments, the bulb may include an alternative vapor and pressure.

The vapor within the bulb chamber <NUM> preferably matches the liquid flowing through flow passage <NUM> (as in the illustrated embodiment, where the chamber <NUM> includes hydrogen vapor and liquid hydrogen flows through flow passage <NUM>), but embodiments may exist where different fluids may be used within the chamber <NUM> and the flow passage <NUM>.

The chamber <NUM> of the bulb <NUM> may be charged with pressurized vapor by connecting a source of pressurized hydrogen vapor to the charging port <NUM> and opening charging valve <NUM>. When the chamber <NUM> has been filled with hydrogen vapor and reaches the appropriate pressure, the valve <NUM> is closed, and the source of pressurized hydrogen is disconnected from charging port <NUM>.

If the vapor within the chamber <NUM> of bulb <NUM> is warmed and exceeds a predetermined pressure level, the safety valve <NUM> automatically opens and vents vapor from within the chamber to atmosphere.

In <FIG>, a stream of pressurized liquid hydrogen <NUM> flows through the flow passage <NUM> of the vacuum jacket pipe assembly <NUM>. The distal tip portion <NUM> of the bulb <NUM> of the probe assembly <NUM> therefore is surrounded by the cold hydrogen liquid <NUM>. With reference to <FIG>, this causes a portion of the hydrogen vapor within the chamber <NUM> of the bulb to condense so that condensed vapor <NUM> puddles or collects in the bottom of the distal tip portion <NUM>. This causes the pressure within the chamber <NUM> to drop to the saturation pressure corresponding to the temperature of the liquid hydrogen within the flow passage <NUM>. As a result, the pressure within the chamber <NUM> corresponds to the saturation pressure of the liquid hydrogen within the flow passage <NUM>.

The pressure within the chamber <NUM> is detected by the pressure transmitter <NUM> (which also includes pressure detection capability), and is transmitted to a controller (not shown), which may include a microprocessor or other computer device. As an example only, the pressure transmitter may receive power from an onboard battery or an external electrical source. Furthermore, as an example only, a suitable controller includes the FlowCom <NUM> controller available from Flow Instruments & Engineering GmbH of Monheim, Germany. The pressure transmission may take place by wireless transmission or by wire.

As is known in the art, and illustrated in <FIG>, once the saturation pressure of a fluid such as liquid hydrogen, is known, the density of the liquid may be determined using density vs. saturation data for the fluid. Upon receipt of the pressure data from the pressure transmitter <NUM>, the controller is programmed to use a combination of polynominals and lookup tables to calculate the temperature and density of the liquid hydrogen stream within the flow passage <NUM>. The controller may then display the temperature and density of the fluid to a user. Alternatively or in addition, the controller may use the received and calculated data to determine a flow rate of the liquid hydrogen within flow passage <NUM> using equations known in the art.

In some embodiments, the saturation pressure may be used by the controller to first calculate temperature (since the type of fluid is known) with the density calculation following as a second step. The density calculation may optionally be in conjunction with the line pressure within the flow passage <NUM> of the vacuum pipe assembly so as to take into account the compressibility of the fluid. Such a system requires a second pressure transmitter, such as <NUM> of <FIG> and <FIG>, to determine the pressure within flow passage <NUM>. There are several polynominals which enable the controller to calculate the fluid density based on temperature for different pressures. Interpolation is then used to determine the density based upon the exact line pressure reading. Alternatively, a lookup-table may also be used as input data for interpolation.

It is to be understood that the saturation pressure of the liquid hydrogen within the passage <NUM> of the vacuum pipe assembly <NUM> of <FIG> could also be determined if the liquid hydrogen within the passage is in a static, non-flowing condition.

As an example only, in view of the above, embodiments of the disclosure may find use in flow meter designs for hydrogen service. In addition, the above embodiments are robust and rechargeable in the field and leverage transmitter electrical classification (Class <NUM> div <NUM> or div <NUM>).

Claim 1:
A system for determining a saturation pressure of a liquid comprising:
a) a probe assembly (<NUM>) including:
i) a manifold (<NUM>) having at internal passage;
ii) an elongated bulb (<NUM>) defining a chamber and including a distal tip portion (<NUM>) and a proximal portion (<NUM>), said bulb secured to the manifold by the proximal portion with the chamber containing a pressurized vapor and in fluid communication with the internal passage;
iii) a charging port (<NUM>) selectively in fluid communication with the internal passage of the manifold; and
iv) a pressure transmitter (<NUM>) configured to detect a pressure within the chamber of the elongated bulb;
b) a jacketed pipe assembly (<NUM>) including:
i. a pipe (<NUM>) defining a flow passage (<NUM>);
ii. a jacket (<NUM>) surrounding the pipe so that a first annular space (<NUM>) is formed, said annular space being at least partially evacuated of air;
iii. a probe port to which said probe assembly is attached and configured so that the distal tip portion of the bulb is positioned within the flow passage of the pipe, said probe port including an inner sleeve (<NUM>) defining a central bore that is configured to receive the elongated bulb, an end cap fitting (<NUM>) having a central opening configured to receive the elongated bulb and an outer sleeve (<NUM>) surrounding the inner sleeve so that a second annular space (<NUM>) is defined between the inner and outer sleeves and the end cap fitting, wherein the second annular space in fluid communication with the first annular space and wherein the probe assembly is removably attached to the end cap fitting by an attachment member (<NUM>).