3.0 Cryogenic Tankage

This post is a continuation of previous video clips from the short course on cryogenic fluid management (CFM) I taught at NASA's Thermal and Fluid Analysis Workshop in September, 2022. The reference report used to present the course topics can be accessed on the Training page at www.moraninnovation.com.

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.

2.0 Environments for Cryogenic Fluid Management

This post is a continuation of previous posts of video clips from the short course on cryogenic fluid management (CFM) I taught at NASA's Thermal and Fluid Analysis Workshop in September, 2022. The reference report used to present the course topics can be accessed on the Training page at www.moraninnovation.com.

Although this section on environments is tailored for the aerospace audience of the NASA short course, the approach can be applied to other applications with appropriate modifications. For example, stationary liquid hydrogen energy storage would need to address local transient solar flux (including day/night cycles), temperature, weather, and seasonal fluctuations (all in normal gravity). Likewise, mobile applications would have thermal and acceleration environments based on the the vehicle (e.g., aircraft, marine, train, truck, etc.) and associated operations.

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.

Calculations for Introduction to Cryogenic Fluid Management

My previous post provided introductory video clips from the short course on cryogenic fluid management (CFM) I taught at NASA's Thermal and Fluid Analysis Workshop in September, 2022. The reference report used to present the course topics can be accessed on the Training page at www.moraninnovation.com.

The final section in the Introduction chapter contains example calculations to demonstrate how to use the tools and equations presented in the previous sections. As an additional resource, I've created a Jupyter notebook containing Python code with the key calculations and example exercises. It is available under a permissive open source license in my public GitHub repository at: https://github.com/moranmatthewe/CryoFM

I've attempted to include sufficient descriptive information and graphics to make the notebook useful as a standalone tool. The Python coding is intentionally straightforward to facilitate interpretation and make it easy to translate to other coding languages of interest to the user (e.g., VBA, C/C++, Matlab, Fortran, etc.).

If you have Python and JupyterLab on your computer, the Introduction notebook and CryoFM™ functions library can be downloaded and used locally (subject to the Apache 2.0 license). If you don't have these applications loaded but would like to try them out, I suggest using the Anaconda distribution to set up your computer with these and other useful programming tools.

Alternatively, if you prefer not to load these programs onto your local machine (or are prohibited by your IT department from doing so), an interactive web browser instance can be invoked using Binder that requires no downloads nor software installation. To try this method, simply look at the readme file on my GitHub repository and click on the "launch binder" icon (see screenshot below).

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.

1.0 Introduction to Cryogenic Fluid Management (CFM)

In September of 2022 I taught a short course on cryogenic fluid management (CFM) at NASA's Thermal and Fluid Analysis Workshop. The course covered analysis and design of liquid hydrogen systems as well as other cryogenic fluids used in power and propulsion applications.

Although the target audience was aerospace engineers and scientists, most of the topics are directly applicable to liquid hydrogen systems in general (e.g., energy, transportation, marine, etc.). As such, the course content can be used as a resource for the development of any liquid hydrogen system.

This first video is a short introduction. Subsequent videos posted over the coming weeks will cover the other topics presented during the course. My hope is that these edited clips will be easier to digest - and later revisit as needed - rather than posting the full ~3 hour video.

The reference report used to present the course topics can be accessed on the Training page at www.moraninnovation.com. Any feedback on this material, or future topics of interest, are appreciated and can be emailed to: info@moraninnovation.com.

The example calculations for these topics are discussed in the next post.

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.

Moran Innovation 2022 Highlights

• Densified Propellant Testing: Moran Innovation was awarded a subcontract to provide subject matter expertise for densified propellant capabilities development at White Sands Test Facility.

• Short course, invited panelist, and presentation: Matt Moran taught a short course and was a panelist and presenter on the topic of cryogenic systems at NASA's 2022 Thermal and Fluids Analysis Workshop.

• NASA Cryogenic Systems Modeling: Moran Innovation is supporting additional new contract work for NASA related to validation of high fidelity modeling tools with experimental tests of liquid hydrogen, methane, oxygen, and other cryogens.

• Heavy-Lift Aircraft: Moran Innovation completed support of a design cycle for the liquid hydrogen propulsion and power system of a private sector heavy-lift cargo aircraft.

• NASA Support Contract Extensions: Moran Innovation has been awarded two contract extensions of 6 months and 18 months, respectively, related to the NASA Human Landing System program.

• Cryogenic Fluid Management: Part 1 of this report series has been published and is available online. In-house training based on the material is also available (see Training).
• Other news. See the Moran Innovation website and blog at LH2era.com for more in depth information and news on hydrogen, propulsion, and power systems.

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. He also leads the LH2 Era™ Webinar Series. More about Matt can be found on his LinkedIn page.

Receiving Liquid Hydrogen

The methods used to receive liquid hydrogen into a container impact the pressure and temperature response during a filling process. Tests conducted with tanks that are not vented during filling as shown above provide insights into which methods are best used for various applications [1].

Bottom Filling

The left top and left bottom panels of the above graphic plots the pressure and fluid temperature responses from a nonvented liquid hydrogen filling from the bottom of a tank using a dip tube diffuser. The general trends would be similar for an open discharge pipe in the same configuration.

Tank pressure slowly rises as the liquid level increases and compresses the ullage gas. The ullage gas remains thermally stratified with gas temperatures slowly rising due to compression. As the liquid level rises, it submerges each temperature sensor causing a sudden drop to liquid hydrogen temperature at that location.

This method of filling works well for tanks that will be partially filled and/or stored for extended periods of time. Liquid hydrogen is conserved by not unnecessarily cooling the container walls above the liquid level.

Upward Discharge Filling

Injecting liquid hydrogen upward from the bottom of a container as shown in the middle panels above actively mixes the liquid in the tank. This mixing enables sufficient condensation at the liquid-vapor interface to keep the pressure near saturation condition until relatively high fill levels are reached.

If the discharge jet has sufficient initial momentum to reach the upper portion of the tank, then the fluid and wall temperatures will be rapidly cooled. For lower velocity injection, the temperatures in the gas and wall will behave similar to the bottom filling configurations, while the liquid remains relatively close to saturation due to constant mixing.

For applications where a well mixed liquid and controlled tank pressure during filling are needed, this filling method works well. Ground vehicles, aircraft, and marine vessels are examples where these characteristics may be desirable.

Top Spay Filling

A top spray liquid hydrogen injection configuration is shown in the  top and bottom right panels above. The resulting droplets drive the tank pressure and ullage gas toward saturation due to the mass transfer occurring between each droplet and the hydrogen vapor.

Design of the spray cone angle will dictate how much of the tank wall is cooled by the incoming droplets. The location and number of spray nozzles are also important considerations if this method is used.

Since top spray filling directly controls the ullage gas conditions, this configuration works well for applications where tank pressure control is a driver during filling. A spray nozzle can also be used in an internal mixing system to drop tank pressure during storage and mitigate the need to vent.

[1] "Hydrogen No-Vent Fill Testing..." Moran, Nyland, and Driscoll, NASA TM-105273, 1991.

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.

Cryogenic Systems Modeling and Analysis

Cryogenic Fluid Management (CryoFM™) Interactive Calculations Notebook

Last month I participated in NASA's annual Thermal and Fluids Analysis Workshop (TFAWS) as a short course instructor, panelist, and presenter on the topic of cryogenic fluid management. This is a critical topic for launch vehicles and spacecraft. It is also becoming a very important consideration for the rapid growth in production, energy storage, ground transportation, shipping, and aviation applications of liquid hydrogen systems.

What is Cryogenic Fluid Management?

Cryogenic fluid management deals with the systems, technologies, and operations associated with the liquefaction, storage, and transfer of cryogenic liquid propellants. Hydrogen, oxygen, and methane are the most commonly used fluids for this purpose.

Appropriate modeling and analysis is vital for development of high performing cryogenic systems. There are three broad categories of software tools typically used for this purpose:

1. Computational fluid dynamics (CFD): The highest fidelity option that also generally requires the highest level of resource commitment (i.e., computational, personnel, and licensing). CFD typically uses a very fine mesh of finite volumes to model the system. Setting up the model and the appropriate parameter adjustments requires experience with the particular CFD software being used and an understanding of how to best represent the actual system of interest.
2. Multi-nodal models: A moderate fidelity and resource option that divides a cryogenic system into discrete lumped nodes. The number of nodes can be few or many, and is a key determinant of the model resolution. Similar to CFD, the modeler's experience with the software and ability to accurately represent the actual system is critical.
3. System-level and first-order analysis: The lowest fidelity option with generally the lowest resource commitment. Reduced order system models and first order analyses can be used early in the development to narrow the trade space of feasible designs. Also useful as a check on the results obtained from higher fidelity tools.

System-Level and First-Order Analyses

Generally, the development of a new cryogenic system and assessment of key operations begins with system-level and first-order analyses. These activities can be performed faster and for lower resource expenditures compared to higher fidelity modeling. They enable assessment and modification of the early design and operational options.

Commercially available general purpose system simulation software options have limited cryogenic modeling capabilities. Conversely, while many cryogenic system specific software tools have been developed over the years, most are either proprietary or inconsistently maintained and documented. And validation of model results for all of the modeling options is an ongoing challenge for applying them to new cryogenic systems.

The short course I taught at the NASA TFAWS event was an attempt to address the documentation issue by presenting a publicly available report on passive cryogenic fluid management that can be accessed online by anyone at no cost. My subsequent technical presentation outlined the status and plans for a set of calculation software tools based on that report for quickly performing first-order analyses and building system-level models.

While both the training course and technical presentation were well received, several excellent questions from workshop participants have been on my mind:

• How can all of the planned cryogenic fluid management tools best be developed and maintained?
• What about users who don't have access to the tool platforms or aren't permitted by their organization to download them (e.g., Python)?
• If other platforms are of interest to specific users (e.g. Matlab), who will modify the tools for those users?

The Open Source Option

One potential approach to addressing these questions is to make the new cryogenic fluid management software tools open source. This approach would ensure that they are accessible; and would encourage  community development, maintenance, and expansion to other platforms and new capabilities.

The screenshot shown at the top of this post represents a small first step in that direction. It uses the Jupyter platform to integrate markdown outline, text, images, and equations with interactive calculations in the Python programming language. A fully functional instance of the notebook can be invoked in a web browser without downloading anything.

By hosting these tools in a public GitHub repository, full access is granted to anyone interested in using or modifying the tools subject to the open source license. Improvements and extension to other platforms can be likewise shared among the user community. If you have any feedback on this approach, or are interested in being part of a future beta test group for the software tools, send me a message at info@moraninnovation.com.

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.