The following summary refers to a paper presented during the 11th Phase-Change Materials and Slurries for Refrigeration and Air Conditioning (PCM2016) conference which took place on May 18-20 in Karlsruhe, Germany.
To store cold energy in the field of refrigeration, ice slurry is a technology with great potential. The cold energy is stored in latent form in a suspension consisting of ice particles and a carrier fluid, using either water or an aqueous solution.
For ice slurry generation, the supercooled water method is a promising technique. Contrary to ordinary ice slurry generators, this method does not need auxiliary power to drive scrapers. Furthermore, the heat exchange area can be designed on a large scale, resulting in a high evaporation temperature and a high coefficient of performance of the refrigeration unit. However, the stability of the process depends on successful avoidance of ice blockage. At first, the flowing fluid is refrigerated in a heat exchanger below freezing temperature but still remains in a metastable, liquid state. In a second step, nucleation is initialized to create the ice particles. This is usually done outside the heat exchanger to avoid ice blockage.
In the present study, the influence of wall surface roughness of a heat exchanger on the supercooling degree of flowing water was investigated. Numerous supercooling experiments using heat exchanger walls with four different surface roughness values were performed.
A significant influence of the surface roughness on the maximum supercooling degree is demonstrated. The smoother the surface, the higher the maximum supercooling degree. Ice blockage in the subsequent flow path behind the supercooling heat exchanger was successfully avoided.
Ernst G, Kauffeld M. Influence of the wall surface roughness on the supercooling degree of water flowing inside a heat exchanger.