My 2 evercools were way too loud, so I retrofitted in a single 120mm maddog from Compusa that pushes 100cfm.

With the top off the box, the thing pushes plenty of air straight out. With the top on, it is starved for air and probably pushes half of what it did with top off. I also noticed with the top on the box, the fan pushes air diagonally from its 4 sides instead of straight out.

I thought plenty of people used 120mm fans, even the maddogs from Compusa. What is the problem?
Do I need to cut an intake vent into the light chamber to feed it more air? I'm using the standard LL design for airflow. The way it is, I don't think I can get rid of the heat fast enough.

The only opening should be between the rear fresnel and the LCD (assuming split design). By making another intake vent, you're taking the cooling air away from the LCD.

Make the opening above the LCD as big as possible. Keep the seals tight to maximize the airflow across the LCD, fresnel, heat shield and back over the lamp. Use a piece of tempered glass if you don't have one in your PJ.

Add more capacity with an additional fan. I have 3, 80mm fans in my first standard PJ and the temp at the LCD is 85F. I'm using 2, 120mm 12VDC fans on my second vertical build which will include tempered glass and Lexan. I expect similar results. Good luck.

What is the width of your box ?
What is the width of your cooling slot ?

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edit: to explain....

the opening on a 120cm fan is approximately 11.5cm, meaning the intake area is (11.5/2)^*pi ; which gives 104cm^2 of intake area.

if your box/cooling slot is 14" wide (14*2.54 = 35.6cm); then the intake cooling gap should be 104/36.5 = 2.85cm (2.85cm/2.54 = 1.22" ... or 1-1/8"). These gaps should be big enough for both the intake slot and the slot beneath the heat shield...

I believe most people make their cooling slots too narrow compared to the intake area's for the fans they use... this is not necessarily a bad thing, but you can certainly expect an increased load on the fan, and therefore more noise...

the slot area is also not the only consideration when considering the load on the fan as every corner (or twists or turns) produces more load on the fan... since you are using the basic cooling circuit you shouldn't have to worry about any detrimental effects... I would simply try to increase the width of you cooling slots....

gs.

My intake opening is about 13.5" wide and the gap is 1.5". Also, I am using the usual glass heat shield.

Last night I got a chance to run the projector for 4 hours. I completely expected the 90 degree thermocouple to trip, and shut off the light. It never did, and 4 hours later when I checked the temperature, at the bottom of the rear fresnel/UV shield it read 72!!! With the 2 Evercools at full blast, it was around 76.
(At ambiant, the room is 62)

Putting my hand by the 120mm it seems like it not pushing nearly the air of 2 Evercools, but apparently it is.
It is still starving for air though....is this bad on the fan?

Cool.

... no problem with the fan, they are designed to run with some load on them...

How do you know that it is starving for air? Does the noise increase when it is starved for air? Does it sound different than when it is running in free space? I ask these questions because I need to make mine as quiet as possible. Could you get by with a lower CFM fan with less noise if this 100 CFM fan is keeping the temps down and it is starved for air?

I know my fans make very distinctive sounds when starved, running in free space, and running in my lightgate. I put in two fans hoping to throttle them down because I suspect two fans running at 1/2 speed would make perhaps less perceived noise than one running at full speed. Of course, there was also redundancy, symmetry, and other considerations. The frequencies of the noise should be important as well as the magnitude of the noise. And the acoustical characteristics of the build will make, perhaps, a big difference as well.

If you haven't seen this you may find it useful.

http://www.lumenlab.com/forums/index.php?s...ndpost&p=128013

Hmmm...

The panflow is rated as follows:
Airflow: 24.0 CFM
Noise: 21.0 dBA
Cost: $6.99 each

I came across this yesterday, via PUN15her:

The Scythe S-FLEX SFF21D 120mm Silent Fan - 800 RPM
http://www.heatsinkfactory.com/Scythe-S-FL...PM-p-16393.html
Air Flow: 33.5 CFM
Noise Level: 8.7 dBA
Cost: $14.99

A little more costly, but the air flow is higher and with less noise. Also, if you want to get the air flow up to around 100 cfm, you could use three fans. The dBA output for each fan is 8.7 dBA. Using 3 fans increases the SPL (sound pressure level) to a total 13.5 dBA which is still much lower than one panflow fan at 21 dBA.

I'm an engineer who works with air flow virtually everyday. As such I have to agree with several points that Brain has made in the various threads and plogs. I believe that Brain has a good handle on air flow.

With that being said, I would like to mention 3 brief points that reinforces a couple of Brain's claims, and hopefully help feed those starving fans.

As I can't provide any copyrighted materials, any information will be strictly from the world wide web (however, that has proven to be a little difficult, as info is limited):

This article is one of the better ones on the net. It discusses inlet geometry, noise, and flow effiecencies.

1) It is more efficient to pull air than to push air:
On the 2nd page under the heading "Air Flow Direction", it states that pulling air is more efficient that pushing air. Table 1 shows difference in between these two directions in reference to fan tip clearances. Pulling air was always better.
Click to view attachment

2) Air should be pulled in near the LCD screen, and exited at the rear the projector:
Sorry, I didn't find any internet material, but I thought this was common sense. I'll start by asking what is the most valuable / temperature sensitive part of the projector? The LCD right? Then it should make sense to pull in the coolest air available right next to the LCD. Why would anyone want to push cold air into the hottest part of the box, mix it, and then get warm air, at best, moving next to the LCD? Also for those who are using the pro lens, your box is hopefully sitting behind you. So personally, I would want the noisy fan(s) as far away from me as possible... at the rear of the projector.

3) Add a Bell Mouth to the Inlet & the Outlet Opening Geometries:
I have not read anything related to this in the forums, but to get the best air flow, with the least amount of air restriction, a "bell mouth" (sometimes called a venturi), should be added to the front enterance of the hole openings. This goes for both the long slot opening near the LCD, as well as for the fan exit opening (fans mounted outside the box).

The web page listed above briefly mentions this and toutes 20% improvement* (meaning if your fan is rated at 100 cfm, you may only be pulling 70% of that when fastened to your project box, with the best inlet geometry the efficiency could improve to 84%. the remaining, missing, 16% would be caused by other ineffiecencies (ie twists and turns in the air flow path)).

The "Rule of Thumb" is the Radius should be 20% of the opening diameter / or slot width. So for a fan opening of 120 mm, the bell mouth radius should be (120 X 0.2 = 24 mm) 24 mm which is approx 1 inch. But as your projector is housed with wood or MDF that is 12.5mm to 19mm thick (1/2 inch to 3/4 inch thick), the radius should match this thickness and span the entire thickness of the wood; on the inside surface of the projector. The 3/8 inch (10mm) slot opening by the LCD should have a radius of 2 mm on the outside surface.

You will notice that the 120mm plastic fans do have small bell mouths already molded into their housing. However, these are insufficient. The manufacturer does not provide a larger bell mouth since these fans were designed to fit into computers, and as the bell mouth grows, the fan size shrinks causing less air flow. However, this should not stop you from adding a full sized bell mouth to your wood housing to help the air exit (less restriction). I hope the pictures below help to describe this concept

Click to view attachment
Click to view attachment

Note: The article toutes 20% but your more likely to get 5% to 10% less restriction / better air flow.

Cheers,

Fulcrum

Here is a picture of "Table 1" that was accidently deleted from my note above:

Click to view attachment

Cheers,

Fulcrum