Week 3: Jumping Hurdles!

Taara S -

Hello! This week I did more trial experiments to make sure my dehumidifier setup has no issues.

On Wednesday, I created three Excel line graphs based on the trial experiments from Tuesday and discussed the trends with my Professor. For every graph, there were issues with the humidity in the top chamber. This chamber’s humidity was always much higher than the bottom and increased when it should have decreased (i.e. when the heater was on). Initially, no changes were made to the setup since we wanted to test a desiccant. 

I then experimented with zeolite’s mesh size. After crushing the beaded zeolite into powder using a mortar and pestle, we ran the powder through the No. 60 mesh sieve and saw that it didn’t pass through. The mesh inside the dehumidifier is roughly a 40-60 mesh size, so this size of powder seemed it would work. I loaded the zeolite into the desiccant chamber and ran a 45-minute experiment. The fan was running at a constant voltage, and after 12 minutes, I turned on the humidifier. After another 15 minutes, I turned the humidifier off and turned the heater on. 

On Thursday, I plotted an Excel graph of the zeolite experiment. The trends at the beginning were normal: the humidity of both chambers increased at the same rate and stabilized when the humidifier was on. But when the heater was on, the humidity of the bottom chamber decreased, while the humidity of the top chamber decreased a tiny bit and then increased again! 

The master’s student and I then wrote down potential issues with the setup and met to brainstorm solutions with our Professor. He noticed a space around the hole of the heater, causing an air leak, so he added cardboard to seal the gap. One of our hypotheses was that the mesh in the top chamber was causing a pressure loss, so he installed a pressure gauge. Also, when I connected the airflow tube to the bottom chamber without the humidifier on, the humidity increased rapidly. So, he moved the temperature and humidity sensors for this chamber higher up.

On Friday, I planned to perform a final set of trial experiments before formally testing my desiccants, since I thought all necessary changes had been made. But when I was waiting for the humidities of both chambers to equalize when nothing was turned on, the top chamber stayed around 80% while the bottom one was around 25% (the ambient humidity). Confused as to why the humidity was so high in the top chamber, I unscrewed the cap and noticed a fair bit of water from when we were cleaning the chamber earlier. I quickly dried the water with a paper towel and measured again, but the humidity only decreased by about 20%. I then used the air flow tube to purge out the system, but again the humidity only decreased slightly. I analyzed the chamber and noticed minuscule water droplets in the crevices, so I thoroughly purged the system and then put the cylinder and chamber in the oven to dry. I tested it again and the humidity dropped to match the top chamber’s humidity! 

But there are always two sides to one coin. While I finally fixed the humidity issue in the top chamber, the bottom chamber had issues. The sensors were moved up too close to the heater, so the Elitech couldn’t register the temperature (above 100 degrees Celsius), and the humidity was therefore too low. So, I discussed with my professor that the sensors may need to be lowered again for more accurate readings. 

All experiments have trial-and-error periods, and I am definitely learning how to navigate these difficulties! Stay tuned for next week as I start testing different desiccants!

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Comments:

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    Payton Miller
    Sounds like this project is giving you great hands-on lab experience! Good luck with testing the different desiccants next week!
    wendysandor
    Hi Taara! Does your lab bench have the availability of air at the gas valve? If so, you could attach tubing to blow out your chamber!
    taara_s
    Hi Ms. Sandor, yep! I have been using an air tube connected to a gas valve between every experiment to purge the air out of the system since it brings the humidity of both chambers back to the ambient very quickly.
    bhuvi_m
    It is interesting how you had to adapt the machine for each problem! Could you elaborate more on zeolite? I can't wait to see your results next week!
    taara_s
    Hi Bhuvi, zeolite is one of the desiccants I'm testing. Zeolite is a microporous, crystalline compound that is structured to adsorb moisture and humidity in the air, making it good for AWC. But zeolite specifically requires high temperatures to operate optimally, so I will also be testing other materials such as hydrogel in order to compare their sorption kinetics and efficiency.

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