Test of Capacity of Adsorption, Water/Silica Gel

Here is a short summery of this technology.
This is a closed system.
The Silica Gel/Water chiller uses water as it’s cooling agent. Water evaporates in a vacuum at room temperature and thereby extracts heat from its surroundings (evaporation energy). Through this process, a cooling takes place in the circuit. See Solar Air Conditioning
Solar Desiccant Adsorption TestSolar Desiccant Adsorption Test
The adsorption chiller utilizes the following properties:
a) the reversible adsorption and desorption process of water on silica-gel
b) the spontaneous evaporation of water on silica-gel
c) the easy condensation
-Advantages- There is no danger of crystallization and thus no limitation in temperatures. There is no internal solution pump and electricity consumption is reduced to a minimum.
Examples of H20/Silica gel are SorTech ACS 08, SorTech ACS 15, SJTU SWAC-10
Example of H2O/Zeolith are InvenSor HTC 10

Today we wanted to check out the absorption ability of silica gel desiccant. Several authorities say silica gel can hold 35% to 40% of its weight in H2O. So 100 grams of Silica gel can soak up 35 grams of water in 5 hours at 77°F and atmospheric pressure or 15% in 1 hour. Then normally to dry out the desiccant, it must be heated to 212°F or 100°C. If the desiccant tank is under a vacuum of say 20 inches of mercury, then water boils at 161°F or 70°C. Now 161°F is within the normal heat range of our solar tube collector.

Desiccant Bag Weight: Weighting in of the desiccant bag that is rated at 224 grams. It shows 225 grams on our mini scale.Desiccant Bag Weight: Weighting in of the desiccant bag that is rated at 224 grams. It shows 225 grams on our mini scale.Desiccant Weight: Weighing in the desiccant 9.6 grams, after zeroing in the container.Desiccant Weight: Weighing in the desiccant 9.6 grams, after zeroing in the container.Weight of Water, 3 gramsWeight of Water, 3 grams

As you can see in the images we are using 9.6 grams of silca-gel in one test tube and 3.0 grams of water in the other. We connected a tube between the two test tubes and applied a vacuum to the whole test. The vacuum is probably not secure and was slowly bleeding down but was reading 12 inches when we left. The experiment started at 4:45 pm on April 2, 2011. The ambient temperature in that room was 78°F at that time. We will return the next day and measure how much water we have left.
Desiccant in Test TubeDesiccant in Test TubeWater in Test TubeWater in Test Tube

After 24 hours the silica gel adsorbed no noticeable amount of water with the above setup with the water in one test tube and the silica gel in another with a looped hose connecting the tops to the tubes. The vacuum pump did not hold any vacuum by the way. So we poured the water from one tube into the other. Within minutes the silica gel balls adsorbed all of the water. Measured a 10°F rise in temperature in the tube with the just added water on the silica gel.
Later that day we heated the silica gel with an alcohol burner with no reliable way of measuring the heat of the tube, but we were looking for 212°F to dry out the silica gel. After 45 minutes of heating the tube to 175° to 250°F we measured only a .6 grams of weight loss. So 2.4 grams of water was still in the silicone. Some water could be seen in the other tube.
Heating the Desiccant with an Denatured alcohol (methylated spirits) (ethanol) lamp.Heating the Desiccant with an Denatured alcohol (methylated spirits) (ethanol) lamp.