Friday, October 22, 2010

The Waterjet Meeting in Graz

I was not planning on writing about the Conference that I have been at this week. It deals with the uses of high-pressure (typically about 55,000 psi) water jets. However there were a couple or three papers that had some relevance to the topic of energy, so I thought I would craft these into a small post.

The first one was a paper by Professor Soyama of Tohoko University in Japan, who has been looking at the events that occur during a cavitation cloud collapse. For those not familiar with what this is, when you adjust the flow pattern of a fluid so that forces try to stretch the fluid, the fluid ruptures into small bubbles. Instantaneously the bubbles have nothing in them, but they fill with vapor from the walls, over time. However there is rarely much time since, as the bubbles move into an area where there is a positive pressure in the water they collapse. But when they collapse it is not totally symmetrical. As a result tiny micro-jets (known in some circles as Munroe Jets) are formed, and these can generate impact pressures of up to a million psi (we proved this theoretical estimation, made originally by Al Ellis at UCSD). At the same time, as Professor Soyama notes, the temperatures that are locally generated can be very high, to the point where light can be generated in the 300 to 700 nm wavelength range. The combination of the two creates an condition where carbon dioxide, injected into the flow, can be (and in his laboratory was) converted into methane. This is a relatively new discovery, and at a scale that may likely be impractical to put to large-scale commercial development, but on the other hand . . . . . . .

The second paper was by Franz Trieb of BHDT GmbH who talked about the use of high pressure jets in helping the construction of prefabricated brick walls. At the rate of 400 sq. m. per day, for 3 workers. It uses the Redbloc system which glues well-formed brick courses together and gives the high quality wall. The water jets cut and trim shapes (such as door entries or windows) in the wall, which is then delivered to the construction site as a finished assembly, and can be rapidly assembled. The resulting house has a number of other benefits including lower cost.

The third item of interest was the description by attendees from KMT high-pressure systems who talked about the transition to gher pressures (up to 90,000 psi) where individual pieces can be cut about 50% faster rates than with conventional pressure. The overall result is a reduction in cutting costs, and lowering of the energy required to cut a part, and the water needed for the process.

Overall it has been a very interesting meeting, though likely my last. There was a mild incredulity when I brought up the subject of peak oil.


  1. A commercial process to transform CO2 to methane would be almost as good as finding the Philosopher's Stone. Of course, one could then burn the methane to recover the CO2, which would make me wonder about the energy going into the water.

  2. The implication is that at very high pressure and temperature, CO2 can react with water. Presumably, the reaction would be something like:

    CO2 + 2H2O -> CH4 + 2O2

    As temperature & pressure decline away from the heart of the Munroe Jets, presumably the hot methane and oxygen would react in a "normal" oxidation reaction. Separation of the methane & oxygen would be an issue. And Porsena is undoubtedly right -- energy has to be conserved (outside of nuclear reactions).

    I'm intrigued as to why Prof. Soyama dissolved CO2 in the water in the first place? Presumably, the methane reaction was not his primary purpose?

    The big thing, though, is that this is a reminder -- a world facing the limits of fossil fuels needs research & creativity, not passive Doomerism. Who knows what new power sources could be made possible with advancing technology?

  3. The methane formation reaction is highly endothermic - this was a side reaction only.

    The amount of energy that went into the water jet process at the pressures mentioned would be huge.

  4. The energy input was not huge. We generate the phenomenon with a pressure washer at the low end. The question is how much is changed. Which is what we might look at.

  5. "huge" is relative to the amount of methane generated.

    Unless something very strange is going on, the amount of the energy input to each converted molecule of CO2 has to be about equal to the amount of energy that would be released by combustion of the resulting CH4 molecule (with any difference explainable by the energy tied up in co-products). And that energy is probably small compared to the pressure/temperature energy dissipated in the water jet.

    Understanding the mechanism for CO2 conversion would be very useful. But why dissolve CO2 in the water in the first place? An attempt to acidify the cutting fluid?

  6. A number of us working in the cavitation field have wondered, for some time, whether we could use the intense conditions generated during bubble collapse to carry out surface chemistry changes that are inhibited in normal circumstances.

    In this case, re-reading the paper, the intent was meant to be demonstrative of the potential of using intensified cavitation to develop chemical reactions, their lab had previously used the process to generate hydrogen. As with some of our work, the cavitation has apparently to be intensified in order for the process to occur. And you are correct that volumes produced are quite small, at this stage.