Do It Yourself : Desert Cooler - 6

Click Rebuilding Desert Cooler  for all related posts.

Content warning: Understanding all content of this post requires knowledge of theory of direct variation, volumetric calculations, and some thermodynamics. Reader discretion is advised ;-)

After the Shavings have been added to the cooler it was time to have water supply in place. Though a simple thing, I went a bit geeky on this just for sake of entertainment and some perfection in the system.

From past of this cooler it was known that standard pump is not enough to provide water to all the sides. It used to leave dry patches in the sides that allowed hot untreated air in. So an effective system was a requirement.

I went to the market and found that a new submersible pump was in use now instead of earlier centrifugal pump that had a shaft and impeller submerged in water with motor held above water level.

Wanted no risks so I decided to install two pumps! Sounds like overkill but with two goals in mind it seemed to be a good decision:

1. Irrigate the Shavings well to have more air molecules interact with water and after some more thermodynamics, better cooling.
2. No dry spots in the sides so that there is no untreated air entering the room.

The two water pumps had to be on separate water circulation circuits so that each one gets its own area to feed. Also, by separating the water circulation circuits, the pumps will not have to compete with themselves For example, a pump pushing water into the water pipe that is being fed by another pump at some other point in the circuit will decrease the efficiency of both..

So two circuits, because the pumps are similar, the area to feed had to be same size. A cooler has three sides. That means one and a half side per pump.

That decided, next was the design of a water drip system that will let the water onto the sides stuffed with Shavings.

The traditional coolers have a V shaped metal strip attached to each side of the cooler and hoses emanating from a distribution joint drop into these metal strips. That arrangement seemed too ad-hoc. Mainly because they are untidy and rickety. Rejected!

I decided to use PVC conduit pipes for the same and cut them according to the need of three sides:

!

One and a half side for each pump

Because each water pump will irrigate only one and a half sides, the top pipe here was cut into half. The cooler fan will be on the open side (here facing downwards).

I thought that making holes in these pipes will be enough. But then I head someone say "Houston, we have a problem!". I reckoned that there could be at least three problems with making holes:

1. If I make too many holes, water will never reach the holes on far side of the pipes. The holes closest to pump inlet will drain all the water and Shavings will go dry at the end, violating goal 2 (no dry spots).
2. Too few holes will make the pipes flood with water and reduce the efficiency of the irrigation system because while the pumps are pushing more water, the holes just cant get it to the Shavings. (goal 1: enough water)
3. Third problem was that the holes might get clogged due to dust and falling of wood-shavings over time and being sucked into the pumps. Has been happening with this cooler in its original design.

Lets address this problem by problem.

1. and 2: Holes should be just enough so that the supply-drain equilibrium is met as closely as possible.

For calculating this I set up the pump with a temporary hose to supply water at similar height as it would have to when installed finally. Approx 3'6".

Then used a stop-watch to measure the time needed to pump a fixed quantity of water to that height. Used a measuring cup that came with microwave over for this. In this case it was 250 CC in 3.5 to 4 seconds. Time averaged to 3.8 seconds and 65.8 CC per second per pump of supply was the magic number.

Now I needed to know how much water can be drained out of a 3mm hole in that PVC pipe when water is being supplied almost at the same level as the pipe. 3 mm was chosen because that seems to be a reasonable size and will not clog very often.

So I sealed a test-pipe at both ends, made a hole in the top and on the bottom side made three 3 mm holes. Poured water from the top and used the same measuring device and stopwatch to find the time that 3 holes take to drain same amount of water. It came out to be around 23 seconds, that is 10.9 CC per second and 3.62 CC per hole per second of natural, unforced flow.

[Don't complain about the numbers. You were warned in the beginning of this post ;-). BTW it is just high school mathematics!]

Thus by dividing supply per pump (65.8 CC per second) with the drain per hole (3.62 CC per second) I got the total number of holes that will be needed (per pump) to balance supply-drain equation. That comes out to be 18.15. I decided to make that 20 to compensate for some clogging due to deposits or dirt etc.

Also 20 holes are easier to make than 18.15 holes...he he

That was the total number of holes. But I have a length to distribute it upon (one and a half side of cooler). The sides are not continuous. I have one full side and one half side. So I cannot just get the separation between consecutive holes by dividing full length with 20 (and compensating for Fencepost error). So I calculated the number of holes to be made in each full and half side based on the ratio of total length (one side + half side) to the ratio of each side's length.

In the image below (click to enlarge), 94 cm is the total length (one full side of 58.5 cm + one half  side of 35.5 cm). 7.5 and 12.4 are the number of holes distributed on the basis of proportion of each side to the total length.

The holes had to be integers. Else how do you make 12.4 holes or 7.5 holes measuring 3 mm each?

Rounded up the above number of holes to obtain two set of possible combinations as follows:

1. Longer side 13 holes and shorter side 7 holes for a total of 20
2. Longer side 12 holes and shorter side 8 holes for a total of 20 again

Calculations. I never thought I will be presenting them here so did on a rough page only.

The combination that will place holes more equidistant will distribute water more evenly on the sides. By dividing each length to the number of holes to be made in it, I get the gap at which the holes should be made.

8 and 12 hole combination gave me best distribution of gap (5 cm on longer side and and 5.3 cm on half side) while 7 and 13 holes suggested that I make holes closer together on the longer side at 4.8 cm and farther away on the half side at 5.9 cm. Evidently the latter being not a very good distribution.

Rest of the things were straight forward. Make the markings and pick up the drill with a 3 mm bit. So here we go:

Standard compass to measure the gap

Start little offset from the side. Water will flow on either side of holes.

Mark the gaps. Compass helps maintain distance. Guide line helps in alignment.

At your mark(s)

 Then comes drilling. 20 holes per one and a half side. Total 40 holes for all sides!

3 mm drill, vice and concentration

All done

But then  came another question. How to cover the edge of the pipes? Water will just fall out on the edges without going through the holes. Also I did not want to seal the sides permanently because there is a fair enough chance that someday they will require cleaning.

What goes here?

I came across an idea and started collecting material for it. A piece of rubber bought from a roadside cobbler for 30 and a curtain holder.

Follow the captions below to see how it was done.

Bought this piece of rubber mat from a cobbler

This curtain rod holder was just right thing for the job

Filed the edges using a round edge file to make a cutting edge

 

wedged the curtain rod holder and the rubber sheet between two pieces of wood in a vice

 

Tighten and tighten and you have your own mini cutting press!

Perfectly round and just over-sized rings to fit snugly

That's it! Now I needed more of them for all open edges

Another challenge overcome :-)

 These round plugs are easy to remove and easy to install. I tested them and they do not allow water to escape from the edges.

Now I have pipes with just enough holes to let the water through at the same rate as pumps will pump it into them.

But where will water enter these pipes? More holes!

That, very soon but in another post!

Take care

-Tweaker

Do It Yourself : Desert Cooler - 5

Click Rebuilding Desert Cooler  for all related posts.

Paint work has cured now and the final pieces are fairly ready to receive the assemblies. Although floor got some stains. I learned from a hardware store owner that these stains can be gotten rid of with some thinner. So that is another post fabrication task on the list.

 Painted and set to receive assemblies

So it was the time for next step. Putting the wood-shavings-wool into the sides.

Now it was quite a hunt to find the wood-shavings-wool...wait a second! Let us give a better name to this 'wood-shavings-wool'. How about just Shavings? Okay then, Shavings it is.

It was quite a hunt to look for Shavings because the roadside vendors are only interested in fitting a small cooler with Shavings and earn seasonal profit. I needed some 3-4 Kgs of it for the cooler and selling that much in bulk by a roadside vendor would be a loss to him because he can manage like 3 small home coolers with that much.

After being unable to convince any of the roadside vendors for a bargain. I assigned the task to my younger brother who arranged the same while I was away at the office from a wholesale market. So I had work to do in the weekend.

Fitting that unruly mass of intertwined wooden laces into those seemed to be a difficult task but I had planned something for it during my earlier brainstorming.

3 Kg of Shavings tied up

The green stuff is what I was talking about. It is mostly used as garden fencing.

I had measured the dimensions before purchasing and that saved me a lot of wastage. First step was to cut an edge to make it straight. That was easy with the new cutter I purchased.

7, 8 Cut 'em straight.

Once you have a straight edge, it is easy to proceed with the measurements and further cuts.

The plan. Just three perfect sized rectangles are needed

The cutter helped a lot and cut like butter through this plastic. Every other option (scissors, knife, handcraft knife, wire cutter, pliers etc) seem to be more inconvenient than this tool.

Lesson: Invest in a nice tool for excellent results

I am more than happy to have purchased this tool. It just caught my eye at one of the shops where I bought sanding wheel for Grinder

The plan.

and here is the result. Three meshes for three sides.

Then came laying of the Shavings in cooler's side grills. This takes more of an artistic touch of your hand rather than just follow a recipe. The Shavings vary in density, toughness and are very unruly when dry. To make it more manageable I soaked it as I spread it on the grill.

Soak well before use

Then spread it on the steel frame and untangled with my fingers and rearranged it using movements of fingers as if I was fluffing up a pillow before sleeping.

2 min into the it

The aim was to obtain a consistent depth that will be around half an inch when I put slight pressure on it. So loose Shavings if 2-3 inch of thickness will be down to approx 1 inch when we tie them up with that green plastic mesh.

Around 5 minutes

10 minutes and done

Next came the process of tying up the Shavings by sandwiching them between the Cooler's frame and the green Mesh. That was done using simple iron wire that is available at all hardware stores. This wire is commonly used to tie up reinforcements in concrete construction and is order-able by Kilos. 250 gm was enough for me.

I cut this wire into pieces and made approx 3 inch long 'V's from it:

Tying the Shavings

Because shavings are wet as I work on them, they will settle in shape of a nice even pad when they go dry.

Sometimes breeze blew through wet Shavings while I was working on it. It cooled it down, gifting me with small cool blows in hot Sunday balcony as a reward for hard work and as a glimpse of what is about to come when all will be put together. :-)

Use standard pliers to twist the wire. Can be done by hand as well. I tied it at multiple places around 5-7 inches apart.

These custom ties are inserted from outer side and twisted at the inside for safety

More tightening and shortening

And the result:

Outer side of the grill

Inside of the grill with Shavings sandwiched between.

 

Does that qualify as photographic art? :-)

So that is a partially ready cooler with Shavings added to all three sides. The whole procedure took something like 2-3 hours and is far better than what we get in the market. More Shavings, better management and uniformly spread.

Next post will cover the water supply. I went a bit geeky on this one but it was fun as well. Stay tuned and please provide feedback.

Good night!

Do It Yourself : Desert Cooler - 4

Click Rebuilding Desert Cooler  for all related posts.

Today was the first day of this weekend and as I said in my last post, spent most of the day painting the framework. What relieves me is that after backbreaking effort, the paint is all complete and to my satisfaction. Areas that will be submerged in water got more than two coats and the rest of the portion got whatever came on the 'instructions' label of the paint.

The painted work looks somewhat like this now:

Note the ruggedness on the inch-square grill, that is from the old sediment and rust that was out of scope of cleaning. So painted over it and seems like it will work.

However, I have also been working on components for the final assembly into the cooler, like filter for the pumps, water supply etc. That I will cover later.

Now as finished paint is curing in the balcony overnight, I will be taking off because I have to be a spectator or probably a player in a cricket match organized by the Company's Cricket club.

So I should be off to the bed now. See you tomorrow with lots of more work. :-)

Good night!

Do It Yourself : Desert Cooler - 3

Click Rebuilding Desert Cooler  for all related posts.

Today you will be finally able to see at least something lustrous emerging out of the rusty frame!

It is all about cleaning so far. Things got worst when I reached the L bars that made up the frame. Rust there was metaphorically 'knee-deep'. Same was the case with insides of water reservoir where dust and salt deposits had made quite a thick layer.

Needed some Special Work And Tools here!

Hand-held grinder came to the rescue with its standard Carborundum wheel for the L bars:

 

The left side of the image above is about a couple of millimeters thick layer of rust. On the right is what Grinder did to it. Purpose was to remove most of the uneven paint and corroded metal which was served well. I had to topple the frame many times to grind all the 4 bars on all 6 sides of the frame that makes the cooler.

Then came the water reservoir, remember a small grinding pad I told I purchased? This one?:

This time grinder wheel was switched to this one and it did manual sandpapering work in fraction of a time and still lesser effort! Here is the thing at work:

Left is the side that grinder has worked upon, the paint here is not flaking much so did not made much efforts to remove all of it. The layer of grit is however completely gone. Good work Black n Decker! :-)

A note of caution here, the grinder sends the sparks and small pieces of rust flying. The spindle turns at few thousand revolutions per minute. Also the dust is very fine and caused some coughing till I used a cloth to mask myself. Also wore big goofy glasses as well to avoid debris getting into the eyes. Another nuisance is noise. Metal being ground makes so much noise that I owe sincere thanks to all neighbors who put up with the ruckus for three-four hours I was at it.

Then came painting, a thick coat of Red-Oxide primer, 4-5 hrs of curing and then a dull blue for the body and lo! Just click this image for a blown up view:

Pretty satisfying to see a sturdy, neat and shining piece coming up. Painting is going on during the moments stolen from the after office hours. 

Later will be assembling the components together. Mostly tidy work Maybe a major chunk of this weekend will go into these activities. Stay tuned. :-)

By the way, now you can have blog posts delivered to your Inbox via Feed-Burner. Link is on home page of each blog. Or just follow these links to subscribe to respective blogs:

Subscribe to Recursive Vortex

Subscribe to My Black Pearls

See you again later.

Good night.

Do It Yourself : Desert Cooler - 2

Click Rebuilding Desert Cooler  for all related posts.

What you saw in last post here was something that needed some work to fix. I came to know today that the cooler was like 8 years old! For that old piece of equipment, it is a great bargain if it gets up and running in a couple of K bucks!

But first things first. Got to plan!

So many days before I used my first tool on that junk, I had a background process running in my head all the time thinking how-tos of everything I need to fix in there.

So after a rough plan, I made out a list of material I would be needing and reserved a day for shopping for stuff in the hardware market. The list read something like:
 - Coarse  grain sandpaper
 - Fine grain sandpaper
 - Wire brush
 - Red oxide primer
 - PVC Conduit pipes
 - Lubricating oil
 - Turpentine oil
 - 3/4 inch hose
 - 4 ft x 1 ft steel wire mesh
 - Insulation tape
 - Water pump
 - Plastic gardening mesh
 - Fan brackets
 - Wiring for fan and pump
 - Paint
 - Wood shavings wool

etc etc

Some things that I figured out will be useful on the fly like this little fellow:

This is a wood workers grinding wheel made of layers of sandpaper. It can be mounted on to a (my dad's) hand-held grinder. I thought might be useful in some cases. And did it help!

So spent a few hours shopping and I came home with a couple of bags of stuff. The whole stuff cost me less than a couple of thousand rupees and that includes some new tools as well (see that yellow handled cutter in the pic?). I find that pretty fair. How about you?

My family members were not surprised as they knew I am up to something or the other all the time! :-)

The most painful task was now. Cleaning it up and preparing for assembly. That included:
 - Sanding the rust and flaking paint off
 - Cleaning
 - Priming
 - Painting


To my surprise that task was more tedious that I thought it would be. Especially when you are starting from something like this:

Ewww!

My shopping basket had sandpaper to start with but sandpapering proved less effective than scraping the flaking paint off with a used Hack-Saw blade. So this is how it was done:

1. Scrape off the paint

 2. Wipe and clean

 3. Sand off the specks of paint. Its easy because small spots are now very vulnerable

4. As good as new! Paint can protect galvanized metal over 8 years!!

That was the water reservoir by the way. 

The cleaning took much of my weekend (almost all). Now I am waiting to steal some time every now and then to act on my remaining stuff.. These days the thing is undergoing more cleaning and painting and going really well. But more on that later.

Let me know if you like the verbosity of this post.

Good night!