Optimization Design Of Scraped Surface Slurry Ice Making Machine

Slurry ice is composed of ice particles and solution,which can be transported by pump and it has good heat transfer characteristics.Slurry ice contains large latent heat as well.With all of the advantages,slurry ice is considered as a promising technology.This paper introduced the characteristics of slurry ice and its important applications.This article used CFD simulation to analysis the scraped surface heat exchanger,the purpose was to increase the heat transfer efficiency of the heat exchanger.Firstly,this paper introduced the scraped surface heat exchanger,built the physical model of two-dimensional heat exchanger.Two kinds of scrapers commonly used in chemical industry were simulated to understand the basic process of the influence of scraper shape on the convection field,summarized the rules and redesigned the scraper structure for slurry ice making process.Two-dimensional simulation of different shape of scrapers and different contact angles between scraper and wall was carried out.The simulation analysis showed that the newly designed scraper can significantly improve the flow of ice making solution after scraping.Secondly,on the basis of two dimensional simulation,the scraper with better performance was selected and the 3D model of the scraped surface heat exchanger is established.Two different kinds of ice making solutions were adopted in the three dimensional simulation.Moreover,the heat transfer inside the heat exchanger and the temperature distribution inside the heat exchanger at different speed of scraper were compared respectively as well as different contact angles between the scraper and the wall.At the same time,the effect of the scraper that with or without hole was analyzed.Finally,this paper analyzed the theoretical cycle of the traditional slurry ice making machine,it is found that there are many differences between the chilling mode of the solution and the ice making mode,for example,the evaporation temperature of the two modes are different,and the heat transfer coefficient between the ice making solution and the refrigerant is different.It is found that the traditional single evaporator(ice slurry generator)based on the ice making mode couldn't match the performance of the compressor,etc.,resulting in lower efficiency of chilling mode,so dual evaporators were proposed to optimize the fluidized ice making machine.The cooling rate of the ice making solution,the evaporation and condensation temperature and the coefficient of performance of the ice making machine under different ice making solution flow rate of single evaporator or dual evaporator were compared.The result showed that the dual evaporator can increase the coefficient of performance of the ice making system when compared with single evaporator,and it can reduce the solution pre cooling time.It is proved that dual evaporator can better match the slurry ice making system,so the ice making system keeps higher efficiency than before in the whole process of ice making.This paper focused on the slurry ice making machine and scraped surface heat exchanger.The CFD simulation was used to analysis the scraped surface heat exchanger to find out which type of the scraper was good for the flow and heat transfer of the heat exchanger.While the experimental analysis was used to optimize the slurry ice making machine.The results showed that the two measures can improve the coefficient of performance of the slurry ice making system and can increase the heat transfer coefficient of the scraped surface heat exchanger.