Consider a plastic funnel with tape to seal the leaks. This may not be very efficient, but the main issue is that the fan has a low power. The power relates to pressure and flow. The pressure is built up because of restrictions to flow. However the pressure build up is limited because the fan blades limit what pressure can be developed.

http://www.usplastic.com/catalog/item.as...

What you need is flow. Pressure allows smaller tubes to be used for a given flow (within reason). You cannot expect much air to flow down the tubes for this small setup, so it will be disappointing. It will nevertheless be a good learning/understanding exercise. Try to measure the flow by how long it takes to fill a balloon, or to move a low friction piston in a cylinder (i.e known volumes). There will be errors due to pressure changes. Try to measure static pressure (pressure with no flow is static pressure) using a U tube to see the height of water that can be lifted.

http://glossary.periodni.com/glossary.ph...

A vacuum cleaner is an example of how much is required. While one side of its fan is reduced pressure, the other side is increased. These often have a motor power like 1kW driving them, and are very noisy and not very efficient at moving air. A different type of air pump is suggested, perhaps using a piston, which can provide a high pressure, or a barrel fan (from a car heater) which can provide a moderate pressure. These will require more power to drive though. The power involved will determine the flow.

Here is a ducted fan for a model plane:

http://www.hobbyking.com/hobbyking/store...

It would be very noisy though. Here are some 12V air pumps that have more power using a centrifugal fan. Still noisy I think:

http://www.bunnings.com.au/lion-12v-air-...

http://www.bcf.com.au/online-store/campi...

Agree with the previous answers, axial fans (like most computer fans) can only produce small static pressure; if you want to get higher static pressures, get a centrifugal fan (and one that has a backward-facing blade is better).

Also, do note that while the aerodynamics of the fins can improve performance,. noise is still going to be an issue.

Fans don't generate very much pressure, inches of water at the most. What sort of pressures are you looking at?

You would need to collect the air and then smoothly reduce their velocity so the kinetic energy is converted into static pressure.

PC cooling fan has the worst rotating power to suck air. Wrong parts that you selected for your project.

Yu will be better off with a shop vacuum which can also blow. it has a multi stage comressor inside which will pump lots of air.

HI, i need ideas on how i can build up air pressure using a pc fan. Example using a plastic to collect air from the pc fan. I need to build up air pressure because the air that is collected will be moving through a tube and the tube will have holes to exhaust air to keep our body temperature low. Yes this is a project. I hope you guys can give me ideas on how to build up air pressure.