同軸噴霧裝置應用於複合式熱交換器之熱傳分析

Abstract

隨著各地平均氣溫逐漸升高，在冷凍空調系統的使用頻率也提高，如何有效提升整個系統的熱傳效率為大家所重視。在此將噴霧裝置應用於複合式熱交換器上，結合了噴霧顆粒發生相變化蒸發冷卻以及部分的熱交換管因噴霧所產生液膜而有水冷作用，再加上風扇的強制對流散熱作用，希望因而有效提升整個熱交換器的熱傳效率。本研究探討各種不同操作條件下，如噴霧液體溫度、熱水熱源溫度、熱交換器型式以及是否噴霧等，找出最佳化設計並且整理出可應用之噴霧熱傳係數的經驗公式。研究結果可知，當噴霧液體直接接觸熱交換器溫度最高之處可以有最好的熱傳效率。經由本研究測試不同熱交換器可證實，具較小熱交換面積的裸管區域較有大熱交換面積的鳍片區具有較高之總熱傳係數，可見噴霧蒸發的效果在裸管區發揮相當大的作用。而使用噴霧裝置後，在不同熱交換器下其總熱傳量增加了8%至33%之間的量。

Heat transfer efficiency has being an emergency issue with the increase of average temperature and refrigeration/ air conditioning usage. The original thoughts of applying Co-axial Spray Devices on Composite Heat Exchanger is to combine the phase change evaporation cooling and the water film cooling effects generated from spray. Furthermore, it will greatly improve the heat transfer efficiency of the heat exchanger with the forced convection heat radiate function of fan. The study is conducted under different operational conditions, such as spray water temperature, heat source temperature, types of heat exchanger and spray availability, trying to find out the best and most feasible heat transfer coefficient formula. According to the research conducted by different heat exchangers, it’s been proved that the plain tubes with smaller heat transfer area presents higher heat transfer coefficient than plain-finned tubes with larger heat transfer area, which shows that spray evaporation will function greatly in plain tube area. After the application of Co-axial Spray Devices, the total heat transfer volume between different heat exchanger has an 8% to 33% increase.