![]() (round) pipe flow is ~2300 (but you have rectangular channels, could maybe pick the hydraulic diameter), and for a free jet I found a number of 1300, but take that with a grain of salt.Īll in all, you're back to gut feelings. The problem is to find the critical Reynolds number that applies to your situation, which is not exactly standard.Ĭritical Re for e.g. The width of the fume hood? (But this is only ~one width long, so hardly counts as a "channel".) Do you pick the width at the end of the small channels in your filter? (but they are triangular/have a non-constant diameter, and flow through the walls to boot). The choice of length scale is important here. With this you get the flow velocity, and you can build a Reynolds number, and if this is higher than a critical number, you'll get turbulent flow. cfm) achieved is the same.Įverything hinges on the pressure loss across the filter (i guess pretty high) and the resulting volume flux of the whole system (depending on the characteristic/power of your fan). A laminar flow glove box is the most appropriate tool to ensure that materials are protected during packaging, quality control research and production processes. My guess/gut feeling is that (due to high pressure loss and flow through a porous medium) the air leaves the filter in a laminar fashion (even if it was turbulent before), so what kind of fan you use shouldn't matter if e.g. I think that such a deep filter will eliminate the need for a screen. Would this be totally wrong? If so, is there a way to build the DIY flow hood to achieve a laminar flow using one of these inline centrifugal fans? Download scientific diagram Opentrons OT-2 unit in Spetec 56 laminar flow box Setup used for sterile cell culture work. It seems to me that so long as the plenum is air tight besides the entry point(fan location) and exit point(HEPA filter), the plenum will achieve a static pressure (based upon the cfm of air driven by the fan and the resistance of the HEPA filter) and flow smoothly out of the HEPA. The argument is that the air pushed by these fans is turbulent and so will exit the HEPA filter in a turbulent fashion. The main question is whether these inline fans will produce laminar flow. The build for a laminar flow hood using these inline fans look, generally, like the two samples at the bottom of this link ( ). Many people are interested in using inline centrifugal fans because they are cheaper than squirrel blowers, more quiet, more energy efficient, and potentially more compact. It is generally accepted that a squirrel blower is effective at creating this laminar flow using the set up in the image posted above. They are equipped with UPS to allow the equipment to operate while moving through departments and to protect the objects placed inside, in an ISO 5 environment.So for years on the mycology, plant tissue culture, and DIY laboratory websites there has been this ongoing debate on how to achieve laminar flow in a home built laminar flow hood. Mobile LAF units are self-supporting modules on wheels, comprising a container trolley and Lexan doors. Typically, PVC strips or Lexan/glass doors are used to create a compartment that protects the classified area. Optional equipment, such as cooling systems and in-line anemometers, is also available.įixed LAF units are installed on the ceiling of the departments, and can cover large areas. Air is drawn through a HEPA filter and blown in a very smooth, laminar flow towards the user. The electrical panel manages the speed of the electrical air fans. A laminar flow cabinet or tissue culture hood is a carefully enclosed bench designed to prevent contamination of semiconductor wafers, biological samples, or any particle sensitive materials. All units are equipped with a Magnehelic pressure gauge to control filter clogging, with ports for filter integrity testing, and with strip led lights on the bottom. Each filter has a mechanical lock to guarantee a perfect seal and for easy replacement. The self-ventilated units consist of an airtight stainless steel box with electrical fans installed on the top and HEPA filters on the bottom.
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