工業冷卻水塔節水設計之研究

開放性冷卻水因環境易遭污染，若忽略水質管理則容易產生碳酸鈣、累積污垢及膠狀(gel)物質，促使冷卻水塔本身及冷凍機的熱傳效率降低，並造成管線及設備腐蝕，故冷卻水質的提升將是主機節能的重點。這種污垢若以人力清洗維護，不僅浪費人力資源且未必能確實完善執行，因此一般大都利用外加之設備或藥劑來改善與維護水質。本文以節省水資源為設計概念，應用過濾系統及紫外線燈作為改善設備。經實驗測試後得知：(1)在循環水量13.63m3/hr下，利用UV-C (波長:253.7nm)、功率:50Wx3之紫外線殺菌燈，照度設定0.3707mW/cm2 (距離:78.7cm)，然後檢驗其總落菌數，發現與用氯錠的殺菌效果相當，故不僅可取代氯錠殺菌，且降低設備腐蝕的風險；(2)過濾徑度若設定為6μm，不僅使淤泥指數SDI15降至3~5、也可降低水硬度、減少結垢去除大量淤泥；(3)加裝UV及過濾設備，及導電度計控制排水量，讓省水率達15~25%。基於上述之結論來設計一套簡易之流程及操作程序，不僅可改善傳統使用殺菌劑及除垢劑的辦法，對防止環境之污染及設備的破壞與節約用水也有時實質上的收益。

關鍵字

節省水資源；水質管理；冷卻水省水設計

並列摘要

Generally, the open style of cooling water is very easy to be affected by the polluted environment. The negligence of water quality management will not only lead to fouling, the precipitation of calcium carbonate (CaCO3) and the accumulation of some gel substances, but also corrode the pipelines and equipment. These would result in the loss of heat transfer efficiency in the cooling tower and freezer, so raising the quality of cooling water has become one of the key factors about energy conservation in designing the cooling tower. Although the fouling and precipitates can be cleaned by the labor, it is time consuming and the effectiveness may not be so good as expected, so adding an external facility or using chemicals for sterilization is the popular practice in maintaining the water quality nowadays. This paper is discussing a new design of cooling tower by adding a UV light to the filtering system for saving the water resources. Experimental data had shown that: (1) the resultant total bacteria count was equivalent to the use of chlorine, when a UV-C light (253.7 nm of wavelength) with the power of 50W x 3, light strength: 0.3707mW/cm2 (Range:78.7cm) and the circulating water flux of 13.63 m3/hr were applied, (2) SDI15 was reduced to 3-5; the water hardness was lowered; the scale was also reduced and most of the mud was removed when 6μm of sieve was used in the filtering system, (3) water saving rate could be up to 15~25% by adding a UV light to the filtering system and using the electrical conductivity to control the water flux. Since no chemical, such as germicide, was used in this cooling tower, it would not pollute the environment and also reduce the risk of damaging the equipment.