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A Tesla valve, called a valvular conduit by its inventor, is a fixed-geometry passive check valve. It allows a fluid to flow preferentially in one direction, without moving parts. The device is named after
Nikola Tesla Nikola Tesla ( ; ,"Tesla"
''
The interior of the conduit is provided with enlargements, recesses, projections, baffles, or buckets which, while offering virtually no resistance to the passage of the fluid in one direction, other than surface friction, constitute an almost impassable barrier to its flow in the opposite direction.
Tesla illustrated this with the drawing, showing one possible construction with a series of eleven flow-control segments, although any other number of such segments could be used as desired to increase or decrease the flow regulation effect. With no moving parts, Tesla valves are much more resistant to wear and fatigue, especially in applications with frequent pressure reversal such as a
pulsejet 300px, Diagram of a pulsejet A pulsejet engine (or pulse jet) is a type of jet engine in which combustion occurs in pulses. A pulsejet engine can be made with few or no moving parts, and is capable of running statically (i.e. it does not need t ...
. The Tesla valve is used in
microfluidic Microfluidics refers to the behavior, precise control, and manipulation of fluids that are geometrically constrained to a small scale (typically sub-millimeter) at which surface forces dominate volumetric forces. It is a multidisciplinary field tha ...
applications and offers advantages such as scalability, durability, and ease of fabrication in a variety of materials. It is also used in macrofluidic applications. One
computational fluid dynamics Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid flows. Computers are used to perform the calculations required to simulate th ...
simulation of Tesla valves with two and four segments showed that the flow resistance in the blocking (or reverse) direction was about 15 and 40 times greater, respectively, than the unimpeded (or forward) direction. This lends support to Tesla's patent assertion that in the valvular conduit in his diagram, a pressure ratio "approximating 200 can be obtained so that the device acts as a slightly leaking valve". Steady flow experiments, including with the original design, however, show smaller ratios of the two resistances in the range of 2 to 4. It has also been shown that the device works better with pulsatile flows.


Diodicity

The valves are structures that have a higher pressure drop for the flow in one direction (reverse) than the other (forward). This difference in flow resistance causes a net directional flow rate in the forward direction in oscillating flows. The efficiency is often expressed in diodicity \mathrm, being the ratio of directional resistances. The flow resistance is defined, analogously to Ohm's law for electrical resistance, as the ratio of applied pressure drop and resulted flow rate: R = \frac where \Delta p is the applied pressure difference between two ends of the conduit, and Q the flow rate. The diodicity is then the ratio of the reversed flow resistance to the forward flow resistance: \mathrm = \frac . If \mathrm >1 , the conduit in question has diodic behavior. Thus diodicity is also the ratio of pressure drops for identical flow rates: : \mathrm = \left( \frac \right)_Q, where \Delta p_ is the reverse flow pressure drop, and \Delta p_ the forward flow pressure drop for flow rate Q. Equivalently, diodicity could also be defined as ratio of dimensionless
Hagen number The Hagen number (Hg) is a dimensionless number used in forced flow calculations. It is the forced flow equivalent of the Grashof number and was named after the German hydraulic engineer G. H. L. Hagen. It is defined as: : \mathrm = -\frac\fra ...
or
Darcy friction factor Darcy, Darci or Darcey may refer to: Science * Darcy's law, which describes the flow of a fluid through porous material * Darcy (unit), a unit of permeability of fluids in porous material * Darcy friction factor in the field of fluid mechanics ...
at the same Reynolds number.


See also

* Coandă effect * Check valve * Diode *
Labyrinth seal A labyrinth seal is a type of mechanical seal that provides a tortuous path to help prevent leakage. An example of such a seal is sometimes found within an axle's bearing to help prevent the leakage of the oil lubricating the bearing. A labyr ...
*
Static mixer A static mixer is a precision engineered device for the continuous mixing of fluid materials, without moving components. Normally the fluids to be mixed are liquid, but static mixers can also be used to mix gas streams, disperse gas into liquid o ...
*
Valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fitting ...


References


External links

* * {{Nikola Tesla Plumbing valves Inventions by Nikola Tesla 1920 introductions