15.07.2015   EuroSun2008-7

FURTHER R&D ON ZEOLITE HEAT PUMPS

The silica gel machine is working at very low driving temperatures down to 65°C, but may not be used, when low water temperatures and high re-cooling temperatures are necessary. In order to achieve this temperature region SorTech AG is currently developing a second prototype chiller based on the same construction principles but using zeolite coated adsorbers.

A new type of coating has been developed and filed for patent application by SorTech AG, which is based on a direct crystallisation of the zeolite on the surface of the heat exchanger (Fig. 5). Compared to the epoxy resin coating which is used in ACS 08 this new technology has the following advantages:

High mechanical stability of the coated layer due to strong binding forces at the interface zeolite — metal.

Fast adsorption kinetics, because of good heat and mass transport resulting from very compact layers, which contain only the active material.

Подпись: Fig. 5. REM picture of the cross-section of an aluminium fin coated with zeolite by direct crystallisation. The overall thickness of the fin is about 500 microns.

Reduction of material synthesis and coating to a one step process.

The feasibility of the direct crystallisation method has been shown by SorTech AG on small samples of aluminium fin material and on tube and fin heat exchangers. Currently we are working on the up-scaling of the process in a pilote plant as a first step for a later industrialisation.

Due to the reaction conditions of the zeolite (200 °C at 20 bars) the chemical engineering is a rather challenging task und is currently being performed.

6. CONCLUSIONS

Small compact adsorption chillers seem to be an attractive option for thermal driven air conditioning. The results of the field test of prototypes carried out in 2007 were encouraging. Therefore since March 2008 SorTech AG has introduced a small adsorption chiller ACS 08 with a chilled water capacity of 7.5 kW and since June 2008 a larger system ACS 15 with 15 kW into the market. Currently, we are producing our products in a small series and the market response is very positive.

7. ACKNOWLEDGEMENT

The financial support from the German Federal Ministry of Economics and Technology (BMWi) is greatly acknowledged.