TO APPLY THE APPROACH to air purification that we used in the Chapel also to the kitchen, how many units would be needed, and where would they be placed?
This post documents a study of the situation.…
Executive Summary
To achieve the design goal of more than 6 air changes per hour in the kitchen, I recommend upgrading 2 of the existing DIY filtration units via the following simple steps: using a more efficient filter, binding the assembly together with clear packaging tape, and adding neoprene rubber foot pads. The total outlay would be $60.
Suggested placement is as shown in the diagram below; see also photos at the end. (A gray box represents a fan, while an arrow shows the direction of air flow.)
 |
| (As usual, click/tap on an image to enlarge it.) |
Room Dimensions and Methodology
According to the architectural drawings supplied in the 2003 Historic Structure Report, the relevant Social Hall dimensions are as follows: 26 ft long and 23 ft wide, less a 4x7 closet. And I measure the ceiling as 8 ft high.
ROOM VOLUME = [(26 x 23) – 28] x 8 = 570 x 8 = 4,560 cubic feet
Contribution of each purifying unit (given its Clean Air Delivery Rate) in that space:
CADR divided by ROOM VOLUME = air change rate (ACH)
DIY Filtration Unit: Characteristics
The DIY air filtration unit that I assembled is discussed HERE. Its noise level (roughly 54 dBA, judging from Srikrishna’s tests, which is twice as loud as a typical refrigerator) is probably acceptable for the kitchen.
When the urgent call came in September for me to build the first DIY units for the Chapel, I had to use off-the-shelf 1"-thick hospital-grade MERV-13 filters from Home Depot. Since then, I have found sources for 2"-thick filters. Other things being equal, thicker filters perform significantly better because they don’t restrict the air flow as much.
Based on Srikrishna’s test of the impact of adding a dust filter (personal communication), I will assume a 10% penalty for one of those.
Contribution of each air cleaner with a 1" MERV-13 filter and dust filter:
200 cu ft/min * 1 AC / 4,560 cu ft. * 60 min/hr = 2.6 ACH
Contribution of each air cleaner with a 2" MERV-13 filter and dust filter:
264 cu ft/min * 1 AC / 4,560 cu ft. * 60 min/hr = 3.5 ACH
Contribution of each air cleaner with a 2" MERV-13 filter and no dust filter:
293 cu ft/min * 1 AC / 4,560 cu ft. * 60 min/hr = 3.8 ACH
Application to the Kitchen
With a 2" filter, 2 units would produce more than 6 ACH. Alternatively, it could be all 3 of the existing units that use 1" MERV-13 filters plus a dust filter. For the sake of noise control, it seems best to aim for 2 units rather than 3.
With Nordic Pure filters (as in the published test): $36 for a box of 3 => $13 ea. (incl. tax). With FilterBuy filters: $17.80 each for 3. Performance difference unknown.
Cost per unit is $44: $30 for the box fan (incl. tax); $13 for the filter (including tax); 40¢ for 184" = 15.4' of clear packaging tape (Scotch storage tape at Office Depot: 2.6¢/ft incl. tax). However, in reality the components are not purchased on a per-unit basis.
NOISE CONTROL: The available flat kitchen surfaces are liable to resonate with the fan vibration and thus amplify the noise. Therefore a pair of vibration-absorbing neoprene rubber pads should be placed between the fan and the surface. I suggest a $7 computer mouse pad (such as from Office Depot), cut into 4 pieces (2 per fan).
TOTAL OUTLAY to simply improve the existing fans by swapping out the 1" filter for the 2" kind: $36 for filters; $17 for tape; and $7 for mouse pad = $60. With that we get not only the 2 upgraded fans but also a spare MERV-13 filter and lots of packaging tape.
Placement
The kitchen offers very few places with access to an electrical outlet where a box fan can stand and blow in a productive direction (and as little as possible directly where people may be standing). We only need two places. I suggest the configuration shown in the diagram above, and in the photos below. (Below, a red rectangle represents a fan, while the blue arrows show the direction of air flow.) This placement should mix the air well in the main part of the room, by creating something of a circulating pattern.
 |
| See next photo for electrical outlet. |
No comments:
Post a Comment