Fog Density Meter<

Current State<

Project Description<

My ongoing PhD thesis is about understanding fog droplets motion around obstacles and more specifically trying to use these understandings to improve fog harvester. To conduct these research, our team is using a test bench that was built in the lab allowing one to simulate real conditions and test their prototypes.

It is composed of a fog generator, a laminar air flow generator, two concentric plastic cylinders and two weighing scales. The fog created by the generator is carried away by the laminar air flow and passes around a hanging obstacle. The top weighing scale measures the mass of the fog water deposited on the obstacle while the bottom one measures the mass of the water drained and hence harvested.

A fog harvester efficiency is computed as the ratio between the incoming fog water mass rate and the harvested water mass rate. We easily measure the harvested water mass rate with a scale under the harvester however we can not yet measure the incoming fog water mass rate, at least not directly. For now we simply estimate it by measuring the water tank mass before and after our measurements and averaging the mass rate.

This measurement method is an issue for two main reasons. First, the efficiency of the nebulizer that creates fog depends on the water level and the fog generation process obviously uses water and make the water level decrease. The incoming water mass rate is hence not constant and the method we use to estimate its value is not accurate for large duration measurements. Second, the water mass rate leaving the tank is not the incoming fog water mass rate. Indeed there is loss on the way hence we overestimate it.

My Fab Academy final project goal is to solve at least one of these problem :

Make the incoming water mass rate more constant
Have a direct measurement of the incoming fog water mass rate

At first I started working on the water level control part with a water level sensor and a pump. However, at the beginning of the Week 9 I realised it would way simpler to use a purely mechanical system which would not work for a Fab Academy final project. I then started to work on the fog density measurement.