What Is Conductance And Why Does It Matter?

Any liquid will flow to fill any container with sufficient room. Fluids move everywhere, and things can’t stop them. The speed at which a liquid shifts from one container to another is often compared to the rate at which water would flow through a maze as if a go-through-the-maze or follow-the-trail game. This movement of fluid is measured by conductance — how easily the fluid forms and follows pathways through the maze.

Since all liquids are mazes of varying sizes, conductance is crucial for designing vacuum systems. It allows technicians to determine how quickly a fluid will react to changes in pressure and assist them in determining what other factors affect the flow rate and which vacuum pumps need to be used for which systems.

Why it Matters

Devices such as the rotor pump can create vacuums quickly but create such low pressures that they are useless. Robert Boyle invented the rotor pump in 1660. It is used in many industrial applications and is the only pump that can create a vacuum in a non-scientific environment. Because of its simple design, it can fit into small spaces, easily creating vacuums. In addition to this, it’s also able to perform at extremely low pressures and can reach very high vacuum levels.

On the other end of the spectrum, piston pumps create larger pressures but take longer to reach high levels – making them too slow for many applications and, in some cases, impossible with low-pressure systems. Piston pumps also operate at a constant speed, so they can’t change the rate they operate to reach specific pressures. Vacuum systems need to be designed with each pump in mind. High Vac Depot is the leading source for Turbine, Rotor, & Piston Pumps for scientific and industrial applications.

Conditions

Temperature

In order to understand it, it’s important to understand that changes in temperature can greatly affect how easily fluids flow. For example, heat up a fluid and it will be easier to move than another fluid at the same temperature that isn’t heated. The important takeaway here is that temperature affects how easily a fluid will turn from one container to another.

Pressure

Although having higher pressure doesn’t affect conductance itself, it does affect the speed with which a liquid will fill one space or another. As you raise the pressure of an enclosed space, you reduce the conductance of the fluid in that space.

Concentration

Conductance is directly related to the concentration of the fluid. Since concentration is a balancing act between the amount of fluid (volume) and pressure, it is affected by both. If you increase the volume but don’t change the pressure, you can move more fluid easily — resulting in it being higher.

Solutions

Conductance is an essential determining factor in designing the most efficient vacuum systems. If you’re working with high or low pressures, it will determine the speed at which your system fills or evacuates. To get the most efficient results out of your system, you must understand how it affects your system and how you can use this information to design better, more stable systems that are more easily filled and evacuated.

Differences Between Instantaneous and Steady-State

In a steady-state situation, all factors remain constant except one: pressure. When you remove pressure from a fluid, it condenses. This makes it more difficult for the fluid to flow and slows down the process of condensation. Think of a balloon being squeezed: it becomes more challenging to fill with air. When that squeeze is released, the air rushes back in — and so does the fluid in our example. As you increase pressure on a fluid, it increases as well. If you remove the pressure from a fluid too quickly, it decreases. Imagine that you take out all of the air in an enclosed space in a vacuum without allowing it to re-fill with the same amount of air. The pressure around the space drops, and because nothing is pushing it back in like before, this causes the conductor to slow down and make it flow more slowly than its initial speed when pressure is added. As you increase pressure back to the original level, it returns to the same speed when pressure was initially applied.

Instantaneous vs. Steady-State

The difference between steady-state and instantaneous is important because they can provide different results and require different calculations to determine how the fluid will react and flow.

If, for example, you want to calculate the amount of water that will fill one container with a certain amount of space, you must first determine the steady-state conductance of the solution. This is calculated by taking your initial volume and dividing it by the final volume. This gives you an indication of how fast it can fill a container. If, however, you’re trying to move water through one container into another with a specific distance between them, then it plays an important role. This is calculated by taking the initial volume and dividing it by the final volume but then raising the final volume from zero to the original constant pressure. This indicates how fast water will fill in between containers. In other words, this is how fast a fluid will fill and move through a maze. Whereas it was once measured in centimeters per second (cps), it is now measured in micromhos (μhos).

Conclusion

Conductance is an incredibly important factor for technicians to understand to create efficient vacuum systems. A lack of knowledge about it can be the difference between a successful application and not. It can be broken down into two easy to comprehend parts: instantaneous and steady-state. Understanding how each affects a system can give you the edge you need to create well-balanced vacuums and high-performing pumps.

High Vac Depot has a vast selection of vacuum systems, including piston pumps, rotary vane pumps, and turbo pumps. All of these are available at competitive prices for all your applications. Turbine vacuum pumps are designed for maximum pumping performance with high reliability and long life spans. They are available with inlet connection options such as flange, bellows, quick connect and sight feed.