Progress Updates 11.15.17

Progress Updates

Date: 11.15.17
Location: Logan HS
Goal: Research adhesive material to hold thermistors in place and packing material for the humidifier.


We needed an adhesive which would hold our thermistors in place to monitor temperature. The adhesive would need to adhere to both metal and PVC in a wet environment. We contacted Mr. Ed Johnson at NECAL Corporation and described what we needed. Mr. Johnson replied back the same day with the solution you see below and sent out some samples for us to try. Special thanks to NECAL!

Sample sheets of pressure sensitive adhesive

We need to start looking at the packing material to use in the brine tank where heated water will be sprayed. We need something that will allow water to slowly trickle down and collect on the packing material. It also has to allow the warm vapor to rise up and over to the other tank. We are thinking about separate units that can be taken out and replaced. A range hood filter would provide the support surface on the top and bottom of each unit with  humidifier filter material in between.

Sketch of  a packed bed tower unit. Notice how one is stacked on top of the other.

Andy K. had some additional thoughts on how to create a greater temperature difference using the Peltiers.

"Possibly lowering the water flow rate through the block could have an impact on the temperature, and we could also try thermal paste.

In our experiment (if I remember correctly, I might be wrong), I think we were trying to cool the water and remove the heat with the fans.  Maybe we should try heating the water rather than cooling it, or redo the experiment with a smaller, stationary volume of water.

To get condensation to form in the dehumidifying chamber of the HDH, the coil needs to be cooler than the surrounding humid air.  Unless the intake water is fairly cold (which would then mean that we would not have to use a peltier to create a cool condensation surface), I don't think we should bother cooling it down for the condensation coil when it needs to be almost immediately reheated for humidification.

Instead, we could intake water straight into the heating part of the HDH and skip running it through the coil. We could cool the coil as is (empty) or cool a coil filled with stationary water which would not be used in the desalination process.  This would probably end up cooling faster and stay cooler for longer.

To do this, a peltier would have the cold side attached to the coil filled with stationary water, and the hot side on the intake water piping.  This would allow for heat to be transferred away from the cooling coil quickly by the water flowing into the system, and at the same time it would begin assisting in heating the intake water for the humidification tank."

Peltier, Heat Sink and Pump Test

Peltier, Heat Sink and Pump Test

Date:11.2.17
Location: Logan HS
Time: 4:15 PM -6:30 PM
Goal: Connect hoses to test pump, peltiers and temperature difference in water with the peltiers.
Students: Andy, Court and Ben

We wanted to begin connecting the peltier, heat sink, hoses, cooling blocks together to test the system. Overall we wanted to see if we could cool the water coming from a source bucket through the cooling blocks and then back into a different bucket.

Problems occurred right away. The second bucket had a leak in it and when we wired our potentiometer to the pump it worked varying the pump speed for a while and then "smoked" the potentiometer.  We will have to look up the wiring configuration again and the ratings on the potentiometer.  Additionally, we could not get the cooling block to cool down the water significantly but we think we have determined the problem which is in our flow rate. For this test we wanted to keep a constant flow rate and not vary it. If we slow down the flow rate we can hopefully improve the cooling properties.

We also started with a warm water temp (about 82 degrees F.) to simulate the water temp in the Indian Ocean. We can improve our delta temp. if we use cold water from a water tap.

The good news is the small pump works well...in fact too well. It really pumps out the water (4 ft. up in the air) so the flow rate will need to be controlled because it was much to fast. We could not get the blocks to cool fast enough. We will  also need to research a device which will allow us to monitor the flow rate of the water.  the Pentium 2 heat sink we purchased on e-Bay works great at keeping the peltiers from overheating. Our tests indicate we can get the peltiers down to 43 degrees F using only 1.72 amps. I think we can get it lower  by adding another peltier to the cooling block (3 instead of 2) with time and experimentation.

Base line test measurements:
Starting water temp = 85 degrees F. (to simulate the Indian Ocean temp)
Starting temp of cooling block -= 75 degrees F.

The test data below indicate to what degree we can cool the water cooling block without water running through it. Note that we seem to stabilize at around 44 degrees F.
Initial Temp of Cooling Block- 71.5 degrees F
Peltiers amperage draw - 1.72 A
Time and Degrees F.
1 min = 53.8
2 min. 49.5
3 min = 46.7
4 min = 46.8
5 min. = 46.0
6 min. = 44.5
7 min. = 44.6
8 min. = 43.8

Questions that need to be answered:
1. If we increase current to the peltiers will it lower the cooling temp?
2. How do we vary the water flow rate?
3. How do we monitor the water flow rate?
4. Can we insulate the plastic tubing to prevent heat/cooling loss?
5. Would a different (flatter) cooling block that disperses the water out more make a difference?
6. Three peltiers vs two on the cooling block?
7. Does hooking the peltiers in series vs parallel make a difference?

Short video on how we conducted our tests. This was our first try at it so our testing procedures will improve with experimentation.

Image of our blue water cooling block and black heat sink with the white peltiers sandwiched in between. The hot side of the peltiers face the heat sink.

Andy is making great progress with the thermistors , LCD and Arduino program.

Andy at work on the temperature monitoring program.

Ben heat shrinking some wires.

Court soldering some extension wires on the peltiers.

Snap shot of how low we can get the peltiers without cooling block attached. The peltiers were hooked in series and drawing under 2 amps.

We created a chart to keep track of our temp data.