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<!DOCTYPE html>
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<title>The concept - Vortex Core</title>
<meta name="description" content="How the Vortex Core concept works: spending a building's waste head pressure on centrifugal separation, with a waste-heat evaporation loop finishing the reject stream.">
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<meta property="og:description" content="Spending a building's wasted head pressure on centrifugal separation, then finishing the reject stream with waste heat.">
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<header class="site-header">
  <div class="wrap">
    <a class="brand" href="index.html">
      <span class="brand-text">
        <strong>Vortex Core</strong>
        <span>A FifeCIC research project</span>
      </span>
    </a>
    <nav class="site-nav" aria-label="Main">
      <a href="index.html">Overview</a>
      <a href="technology.html" aria-current="page">The concept</a>
      <a href="feasibility.html">Feasibility</a>
      <a href="interest.html">Get involved</a>
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<div class="page-head">
  <div class="wrap">
    <p class="eyebrow">Design intent &mdash; not a specification</p>
    <h1>The concept</h1>
    <p class="lead">
      A pressure-reducing valve is a component that exists only to destroy energy. Vortex Core
      asks whether that energy can be put to work instead, and whether the result is enough to
      separate microplastics from the water passing through it.
    </p>
  </div>
</div>

<main id="main">
  <div class="wrap">

    <div class="callout callout-warn">
      <h2>How to read this page</h2>
      <p>
        Everything below is <strong>design intent</strong>. No part of it has been built or
        measured. Figures are either calculated requirements, design targets, or stated
        assumptions &mdash; and each one is labelled as such. Nothing here is a test result.
      </p>
    </div>

    <section>
      <h2 class="section-title">1. The pressure budget</h2>
      <p class="section-sub">
        The starting point is not a new energy source. It is an existing one that is currently
        spent on nothing.
      </p>
      <div class="prose">
        <p>
          A twenty-storey building pumps water to a roof tank. By the time that water reaches the
          lower floors, the column above it has produced something in the region of
          80&ndash;100&nbsp;PSI at the base of the riser. Domestic fixtures and fittings are rated for a
          fraction of that, so a pressure-reducing valve dissipates the surplus as friction and
          heat. It is deliberate, universal, and it wastes a genuinely useful quantity of energy.
        </p>
        <p>
          Vortex Core replaces that valve with a tangential inlet. The water is not allowed to lose
          its pressure quietly &mdash; it is injected tangentially into a conical chamber at
          2&ndash;5&nbsp;m/s and forced into a tight spiral. Head pressure becomes rotational velocity.
          The device still delivers the pressure reduction the building required; it simply takes
          payment for it in useful work.
        </p>
      </div>
      <div class="formula">
        pressure energy in &rarr; tangential velocity &rarr; rotational acceleration (G) &rarr; particle migration &rarr; reduced pressure at outlet
      </div>
      <p class="section-sub" style="margin-bottom:0">
        Design target: 2,500&ndash;3,000&nbsp;G sustained at roughly 80&nbsp;PSI inlet and design flow.
        Whether that is reachable in a compact device is one of the questions we cannot yet answer.
      </p>

      <figure class="figure" style="margin-top:26px">
        <img src="assets/img/building-comparison.svg" width="760" height="500"
             alt="Two riser schematics. On the left, labelled Today, a pressure-reducing valve destroys the surplus head pressure as heat, shown leaving the valve as wavy arrows. On the right, labelled With Vortex Core, a separation chamber spends the same pressure on rotation, and the separated fraction leaves to one side.">
        <figcaption>
          <strong>The whole point, in one picture.</strong> Both buildings have the same water, the
          same head and the same pressure to shed. The only difference is whether that pressure is
          destroyed by friction or spent on rotation.
        </figcaption>
      </figure>
    </section>

    <section>
      <h2 class="section-title">2. Three stages, each using a different property</h2>
      <p class="section-sub">
        A single separator cannot resolve particles that behave in opposite ways. The concept
        therefore uses three stages in series, each targeting a different physical difference.
      </p>

      <div class="figure">
        <div class="stack-diagram" role="img" aria-label="Flow diagram: roof tank, heavy cyclone, light-fraction skimmer, polishing stage, then distribution to floors.">
          <div class="node"><strong>Roof tank</strong><span>gravity head, approx. 80&ndash;100 PSI at the base</span></div>
          <div class="arrow">&darr;</div>
          <div class="node"><strong>Stage 1 &mdash; Centrifugal cyclone</strong><span>heavy fraction: PET, PVC, sand and sediment &mdash; thrown outward and collected</span></div>
          <div class="arrow">&darr;</div>
          <div class="node node-alt"><strong>Stage 2 &mdash; Vortex finder</strong><span>light fraction: PE and PP drawn into the low-pressure core and skimmed</span></div>
          <div class="arrow">&darr;</div>
          <div class="node node-green"><strong>Stage 3 &mdash; Polishing</strong><span>UV-C for biological safety, optional carbon for taste and odour</span></div>
          <div class="arrow">&darr;</div>
          <div class="node"><strong>Distribution to floors</strong><span>at the pressure the building needed in the first place</span></div>
        </div>
        <figcaption>
          Indicative flow path. Each stage consumes a small amount of pressure
          (roughly 2&nbsp;PSI in the concept), so the arrangement needs enough head to drive all three.
        </figcaption>
      </div>

      <div class="cards">
        <div class="card card-accent">
          <h3>Stage 1 &mdash; heavy fraction</h3>
          <p>
            Water enters tangentially and forms a tight vortex. Particles denser than water
            &mdash; PET and PVC at 1.3&ndash;1.5&nbsp;g/cm&sup3;, along with sand and sediment &mdash; are slung
            to the outer wall and fall through an apex valve. Design target: removal of particles
            above 20&nbsp;&micro;m.
          </p>
        </div>
        <div class="card card-accent-green">
          <h3>Stage 2 &mdash; light fraction</h3>
          <p>
            The centre of a vortex is a low-pressure eye. Polymers lighter than water
            &mdash; polyethylene and polypropylene at 0.85&ndash;0.95&nbsp;g/cm&sup3; &mdash; migrate inward
            rather than outward, and can be skimmed from that core instead of being left in the
            product water. This is the stage with the hardest physics in it.
          </p>
        </div>
        <div class="card card-accent-tan">
          <h3>Stage 3 &mdash; polishing</h3>
          <p>
            A UV-C chamber for biological safety, and optionally a carbon block for taste and
            odour. This stage is conventional water treatment, included because a separator is not
            a disinfectant and should not be presented as one.
          </p>
        </div>
      </div>
    </section>

    <section>
      <h2 class="section-title">3. What the device would look like</h2>
      <p class="section-sub">
        A cross-section of the intended arrangement. Two things in it are easy to misread: the water
        changes direction, and the particles do not.
      </p>

      <figure class="figure">
        <img src="assets/img/device-cross-section-v3.svg" width="880" height="780"
             alt="Cross-section of a hydrocyclone showing both outlets and the sorting mechanism. Feed enters tangentially at the upper left. Two radial arrows in the cylindrical section show denser particles drifting outward and buoyant particles drifting inward. Water spirals down the outer wall, reverses at the cone and climbs the core, leaving through the vortex finder at the top carrying water and the light fraction; particles denser than water continue to the apex and leave as the underflow. A note explains that the particles do not swim upstream, and that whether buoyant particles drift inward fast enough to be captured is the least certain part of the concept.">
        <figcaption>
          <strong>Illustration of intended behaviour &mdash; diagram v3.</strong> Particles orbit the
          vessel, so they sweep side to side across the section and change size as they pass nearer
          and further from the viewer. The two radial drift arrows are the actual sorting step. A real
          flow path is helical; this is a section through it, so the spiral is shown by the sweep
          rather than drawn as a helix. Not an engineering drawing, and not a fabrication reference.
        </figcaption>
      </figure>

      <h3>Why the particles are not swimming upstream</h3>
      <div class="prose">
        <p>
          A drawing like this invites an obvious objection: water only travels down, so how can
          anything travel up it? The answer is that <strong>the water itself changes direction, and
          most of it leaves by the top.</strong> In a hydrocyclone the flow splits into two co-axial
          vortices &mdash; an outer one descending the wall, and an inner one climbing the core to
          the overflow. That is what the vortex finder is for, and it is why the device has two
          outlets.
        </p>
        <p>
          The particles are <em>carried</em> by that water. They do not push upward against the
          current. The separation actually happens <em>sideways</em>: in the centrifugal field,
          material denser than water drifts outward while material less dense drifts inward, and each
          is then transported by whichever vortex takes it. The two drift arrows on the diagram are
          the whole mechanism; the vertical movement is only the transport afterwards.
        </p>
        <p>
          The flow split does have a consequence for how the thing would be plumbed in, and it is
          worth stating because it is easy to miss: the product water leaves by the <em>top</em>
          outlet, so it has to be piped back down the riser to reach the floors below. That is an
          additional run of pipe, and it is the reason this is not a like-for-like swap for a
          pressure-reducing valve.
        </p>
      </div>

      <div class="callout callout-warn">
        <h2>The weak point, stated plainly</h2>
        <p>
          Radial drift is well proven for dense solids. It is far less proven for <em>buoyant</em>
          particles, which is the case this concept depends on. Three things make buoyant capture
          harder: the density difference driving the drift is small; the central core of a
          hydrocyclone is typically an air core rather than water, so a floating particle may sit at
          a free surface rather than being skimmed; and the argument depends on the inward drift
          being fast enough to reach the core before the water carrying it leaves the bottom.
        </p>
        <p>
          That is why <a href="feasibility.html">feasibility</a> treats light-fraction capture as an
          open question rather than a design feature, and why the next step is a numerical model
          rather than a nicer drawing. It is also entirely possible that
          <strong>a hydrocyclone is simply the wrong device for buoyant material</strong>, and that
          this needs a different separation principle altogether. A model should be able to tell us
          that &mdash; and if it does, that is a useful answer, not a failure.
        </p>
      </div>
    </section>

    <section>
      <h2 class="section-title">4. Where each stream goes</h2>
      <p class="section-sub">
        The chamber produces two streams rather than one clean and one dirty. Where they go is a
        separate question from how the separation works, so it is drawn separately.
      </p>

      <figure class="figure">
        <img src="assets/img/flow-pathways.svg" width="1000" height="620"
             alt="Flow schematic of four stages. Stage 1 is the Vortex Core separation chamber. Its underflow, carrying the heavy fraction, runs to stage 4, the evaporation loop. Its overflow, carrying water and the light fraction, runs to stage 2, a light-fraction skimmer, whose own reject also runs to stage 4. The water then goes to stage 3, polishing, and on to the floors below. Stage 4 leaves dry plastic residue for a collection tray and recycling, and condensed water returned to the clean side.">
        <figcaption>
          <strong>Design intent, stage by stage.</strong> Nothing here has been built, and no stage
          has been tested. Note that the evaporation loop takes <em>both</em> reject streams &mdash;
          which makes it the part of the concept with the least engineering behind it.
        </figcaption>
      </figure>

      <div class="prose">
        <p>
          The concept routes both reject streams &mdash; the underflow, estimated at
          5&ndash;10% of total flow, plus the smaller skimmed light fraction &mdash; through a heat
          exchanger fed by the building&rsquo;s own waste heat: chiller returns, server room exhaust,
          or solar gain. The water evaporates; the plastic does not. What is condensed back is clean
          water, and what remains is a dry residue that can be collected in a tray and sent for
          recycling rather than discharged as liquid waste.
        </p>
        <p>
          Two honest caveats. First, the energy balance of this loop has not been calculated in
          detail; &ldquo;waste&rdquo; heat is not the same as <em>available</em> heat, and it may not
          be available when the loop needs to run. Second, a system that removes particles above
          roughly 15&nbsp;&micro;m is a pre-treatment step, not a complete potable water treatment
          train, and should not be described as one.
        </p>
      </div>
    </section>

    <section>
      <h2 class="section-title">5. The physics question, stated plainly</h2>
      <p class="section-sub">
        This is the part that decides whether the concept is viable. It is also the part most
        easily glossed over, so here it is in full.
      </p>
      <div class="prose">
        <p>
          The rate at which a suspended particle migrates under centrifugal force follows a form of
          Stokes&rsquo; law:
        </p>
      </div>
      <div class="formula">
        v = (d&sup2; &times; |&rho;p &minus; &rho;f| &times; a<sub>c</sub>) &divide; (18 &times; &eta;)
      </div>
      <p class="section-sub">
        where <em>d</em> is particle diameter, <em>&rho;p</em> and <em>&rho;f</em> are the densities of
        particle and fluid, <em>a<sub>c</sub></em> is centrifugal acceleration, and <em>&eta;</em> is
        viscosity.
        Two things follow immediately: separation gets harder as the square of particle size, and
        harder as the density difference shrinks.
      </p>

      <div class="table-scroll">
        <table>
          <caption>Calculated G-force required at 50&nbsp;&micro;m and 5&nbsp;&micro;m, by polymer density. These are requirements derived from the relationship above &mdash; not measured results.</caption>
          <thead>
            <tr>
              <th scope="col">Particle size</th>
              <th scope="col">Polymer</th>
              <th scope="col">Behaviour</th>
              <th scope="col">G-force required</th>
              <th scope="col">Within our 2,500&ndash;3,000&nbsp;G design point?</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td>50&nbsp;&micro;m</td>
              <td>PET</td>
              <td>Denser than water</td>
              <td>19&nbsp;G</td>
              <td><span class="tag tag-yes">Comfortably</span></td>
            </tr>
            <tr>
              <td>50&nbsp;&micro;m</td>
              <td>Polyethylene</td>
              <td>Buoyant</td>
              <td>147&nbsp;G</td>
              <td><span class="tag tag-yes">Comfortably</span></td>
            </tr>
            <tr>
              <td>5&nbsp;&micro;m</td>
              <td>PET</td>
              <td>Denser than water</td>
              <td>1,931&nbsp;G</td>
              <td><span class="tag tag-yes">Yes</span></td>
            </tr>
            <tr>
              <td>5&nbsp;&micro;m</td>
              <td>Polyethylene</td>
              <td>Buoyant</td>
              <td>14,679&nbsp;G</td>
              <td><span class="tag tag-no">No &mdash; order of magnitude short</span></td>
            </tr>
          </tbody>
        </table>
      </div>

      <figure class="figure" style="margin-top:26px">
        <img src="assets/img/gravity-requirement-chart.svg" width="1000" height="560"
             alt="Log-log chart of the centrifugal force required to separate microplastics. The horizontal axis is particle diameter from 1 to 100 micrometres. The vertical axis is required force from 10 to 1,000,000 G. Three straight lines show PET and PVC, polypropylene, and polyethylene. A green band across the plot at 2,500 to 3,000 G marks the design point, and the shaded area above it is where the design point is not enough. PET crosses the band at 4.4 micrometres, polypropylene at 8.9, and polyethylene at 12.">
        <figcaption>
          <strong>The same relationship, drawn.</strong> Each line is a polymer family. Where a line
          sits below the green band the design point is sufficient; where it rises above, it is not.
          The three markers give the answer directly: <strong>4.4&nbsp;&micro;m for PET</strong>,
          <strong>8.9&nbsp;&micro;m for polypropylene</strong>, and only
          <strong>12&nbsp;&micro;m for polyethylene</strong>. Below those sizes, for each polymer,
          particles would pass straight through. The chart is generated from the same relationship as
          the table above, so the two cannot drift apart.
        </figcaption>
      </figure>

      <div class="callout callout-warn" style="margin-top:24px">
        <h2>The gap, named</h2>
        <p>
          At 5&nbsp;&micro;m, buoyant polymers need three to six times our design point &mdash;
          8,000&nbsp;G for polypropylene and 15,200&nbsp;G for polyethylene. Kinetic energy scales with
          the square of velocity, so reaching those numbers by spinning faster is not an adjustment
          to the same machine; it is a different machine, with different pressures and different wear.
        </p>
        <p>
          There is a second risk that matters as much as the first: a single chamber tuned to eject
          heavy PET can concentrate light polypropylene in the stream it declares clean. Any design
          must demonstrate that it does not simply move a problem from one species to another.
          <a href="feasibility.html">How we plan to test both &rarr;</a>
        </p>
      </div>
    </section>

    <section>
      <h2 class="section-title">6. Where it could go</h2>
      <p class="section-sub">
        The intended deployment is one device per riser, at or near where the pressure-reducing
        valve already sits.
      </p>
      <div class="cards">
        <div class="card card-accent">
          <h3>Retrofit</h3>
          <p>
            In an existing building, the device occupies a plant-room position adjacent to
            existing pressure control. No new energy supply is required, which is the single
            biggest practical advantage of the concept.
          </p>
        </div>
        <div class="card card-accent-green">
          <h3>New build</h3>
          <p>
            Designed in from the start, the pressure budget, riser layout and waste-heat access can
            all be arranged to suit. This is where the concept is most likely to work well.
          </p>
        </div>
        <div class="card card-accent-tan">
          <h3>A visible installation</h3>
          <p>
            The chamber is a glass-and-steel object with water visible inside it. That is an
            opportunity but also a commitment: a public-facing installation has to work, and has to
            be honest about what it is doing.
          </p>
        </div>
      </div>
    </section>

    <section>
      <div class="cta">
        <div>
          <h2>Next: what we can actually prove</h2>
          <p>
            The concept is not the hard part. Knowing whether it is real is. Here is what exists,
            what does not, and the order we intend to work in.
          </p>
        </div>
        <a class="btn" href="feasibility.html">Read the feasibility plan</a>
      </div>
    </section>

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          <li><a href="mailto:queries@fifecic.scot">queries@fifecic.scot</a></li>
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        Vortex Core is a research concept. No performance figures on this site are validated by
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        target, a calculated requirement, or a stated assumption.
      </p>
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