| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 88 === In the present research, technique of vacuum flash freezing has been used to purify the waste water. When upper liquid layer film of the falling wastewater solution evaporates in vacuum, it will take away a great amount of thermal energy of the remaining solution and thus freeze the remaining lower liquid layer of the solution. From a previous study, it shows that the technique has the characteristics of fast freezing and energy-saving. In the conventional purifying methods of distillation and reverse osmosis, the former one consumes too much energy and the latter one operates slowly and is quite expensive. All of those shortcomings could be improved by using the present technique. Therefore, its potential of further development is much greater.
With the result of feasibility study performed in the previous work, emphasis is placed upon the improvement of purification. Possible parameters to improve the quality of flash freezing will be studied carefully, and then the research work will try to find the way to apply the technique to industry in the future and to provide suggestive guidance for follow-up researchers.
On improving the quality of freezing, the method includes increasing of the flowing area and better design of wastewater inlet in order to make the flowing of evaporating liquid layer more smooth and uniform.
From the results obtained from the previous and the present experiments, we have found that there are some relations between precooling temperature and wastewater flow rate. No matter the precooling is too much or not enough, the location and quality of freezing can be rectified by increasing or decreasing the flow rate. Thus, when there exist a precooling temperature at which the degree of purification is optimal, there also exists an optimal flow rate at the same time.
On the relation between flow rate and inclined degree of the flowing channel, the results show that the degree of purification increases as the inclined degree of the flowing channel increased. But flow rate also has showed effects on the DOP results of freezing process. Therefore, by finding out the relationship between the optimal flowing-time and the DOP, the results can still provide useful data and reference for
different operations in industry.
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