在本篇研究中，為了減少 ORC 廢熱回收系統在輸入熱源不穩定時所導致之大程度效能銳減，本計畫設計出新型的 ORC 蒸發器，其中加入了嶄新的相變熱儲材料之相關技術；試圖利用相變熱儲材料蘊含之大量潛熱，在熱源輸入不連續之情況時，仍有效的維持住蒸發器的平均溫度，進而達成出口溫度之恆定性。本文中，將以計算流體力學之方法來驗證擁有相變熱儲材料之蒸發器，是否具有吻合最初設計(解決輸入熱源不穩定)之有效性；在此，我們將與傳統之無相變熱儲材料之蒸發器做比較，並再以一簡易之 ORC 數學模型來預測新型與傳統蒸發器對 ORC 之實際影響。由初步結果可知，相變熱儲材料可有效的減少蒸發器出口端的最大溫降；在長達 60 秒的熱源間斷下，可以減少 26.45%的最大溫度差值；而經由 ORC 數學模型之後續計算後，本研究估計上述之改善可使循環增加 9.07%的總輸出功。

The prediction of the consequences of the intermittent heat supply from the hot engine oil used inside the waste heat recovery (WHR) of an organic Rankine cycle (ORC) is of great interest to industry. While there exist a number of steady-state simulations made for a general heat exchanger, there is a lack of transient numerical studies with the heat exchanger embedded with phase change material (PCM). In the present study, we initiate a new WHR-ORC evaporator with the addition of embedded PCM and serpentine flow channels. Validated with the experimental data, this study is intended to deal with a WHR-ORC situation, where the hot engine oil stops providing enough energy into the carbon dioxide (the cold fluid, CO2) by lowering the inlet temperature of the hot oil, albeit with the PCM continuing to supply additional heat into the CO2 before the heated supercritical CO2 enters the turbomachinery with compensation for the loss of the energy supplied normally from the hot engine oil. A CFD tool is utilized for the performance of evaluation of the PCM-embedded evaporator. A 26.45% reduction in the temperature drop of the CO2 is achieved in the case of the intermittent heat supply for a period of the downtime of 60 sec of the hot engine oil inlet temperature. It is reported that the overall dynamic responses of heat transfer change consistently and physically with the variation in the hot oil inlet temperatures. At the end, a simple mathematical model according to thermodynamic principle is made for evaluating the ORC efficiency, carrying out the result which shows a 9.07% increase in ORC work production with the installation of PCMs. This suggests the PCM design is beneficial to improving the ORC efficiency, resulting in a positive gain factor.

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