| 摘要: | 板式熱交換器作為蒸發器時,入口處的兩兩相冷冷媒因慣性力力與重力力 的作用,造成流流道入口的冷冷媒分佈不不均,為了了降降低此現象,目前多於 入口處裝置入口分佈器。但產生單一流流道內分佈不不均勻的問題,而入 可分佈器可藉由改變不不同的開孔方向改善單一流流道中兩兩相冷冷媒流流動 分佈不不均勻的問題。本研究利利用紅外線熱像儀觀察板片之溫度度場,並 且進一步分析在板式熱交換器內設置分佈器之後對於冷冷媒蒸發溫度度 場的影響。從板片表面溫度度場觀察結果可知,接近冷冷媒側流流道入出口 處之過熱面積會小於遠離離冷冷媒側入出口處之過熱面積,而此種現象在 設置入口分佈器以後則不不明顯。若若固定過熱段與飽和段的熱傳量量比例例,冷冷媒雷雷諾諾數數越高則過熱面 積越小,原因是冷冷媒飽和段的熱傳機制主要被核沸騰主導。在相同的 熱傳量量下,同向流流動的過熱段面積較逆向流流大,原因是過熱段的兩兩側 流流體溫差較小。從局部熱傳係數數分析結果得知,設置分佈器以後熱傳 係數數較低(約減少 14%),此實驗結果歸因於冷冷媒流流經分佈器的時候所 造成的壓降降以及乾度度上升。在冷冷媒飽和段熱傳量量減少的情況下,其熱 傳係數數也相對減少。Because the inertia force and gravity is different among liquid and vapor, there is flow mal-distribution in a header of plate heat exchanger when the refrigerant is two phase fluid. In order to reduce this phenomenon, some people install distributor in the header of exchanger, but the opening direction of distributor will affect refrigerant flow distribution in a channel. In this research an experimental study to visualize temperature distribution in the plate heat exchanger that in order to observe the effect of installing the optimum distributor in the plate evaporator. From temperature visualization results, the area of superheat near the side of refrigerant port is larger than that of near the side of water. This phenomenon is not obvious in the case of installed distributor.If fix the ratio of heat among the single phase region and the two phase region, area of superheat become smaller when refrigerant rate become larger. The reason is that the main heat transfer mechanism in two phase region is nucleate boiling heat transfer. The area of superheat in counter flow case is smaller than parallel flow case. The reason is that the logarithmic mean temperature of single phase in the counter flow case is larger than the parallel case. Heat transfer coefficient in the case of installed distributor is smaller than the case of uninstalled distributor (about 14% reduced). This phenomenon is attributed to the pressure dropping and vapor quality rising when refrigerant flow through the distributor. |
