R245fa於有機朗肯循環發電系統之動態模擬分析

Abstract

本研究以模擬方法探討改變外在環境條件對ORC系統之影響，外在環境條件例如熱源與冷源的入口溫度、質量流率、泵轉速……等，使用R245fa當作系統工作流體，熱源與冷源都使用液態水當作工作流體，而使用的元件包括蒸發器、冷凝器、泵和膨脹器，而在實際狀況中熱源與冷源會隨環境條件而變動，系統高低壓會因此而浮動，但過去ORC模擬的邊界條件使用的固定高低壓或固定過熱度無法反映此現象，因此本研究模擬以冷媒填充量來當作邊界條件，讓系統可以隨環境條件變動而浮動，以呈現更真實的ORC系統使用狀況。 模擬結果發現，在固定泵的轉速下，減少冷源入口溫度、增加冷源質量流率、蒸發器和冷凝器管長都可以增加膨脹器作功和系統熱效率，但增加熱源入口溫度和熱源質量流率並不能使系統熱效率上升；另外，在提升泵轉速下，可以使膨脹器作功增加和系統熱效率增加。

The purpose of this study is to simulate the system performance of ORC (organic Rankine cycle) system subject to changes of externally environmental conditions. The external environmental conditions includes changes of inlet temperature of heat and cold source, mass flow rate of heat and cold source, pump rotation speed. The major differences between the present study and others are that no extra constraints such as given high pressure or low pressure are imposed initially. Typical simulations from the literatures normally fix high pressure and low pressure of system or superheated temperature of refrigerant. Instead, the only constraint in this study is the amount of inventory of working fluids. With this help of the present ORC program, the associated temperature and pressure in the system will be obtained. The result shows that reducing inlet temperature of cold source, increasing the mass flow rate of cold source or increasing the tube length of evaporator and condenser at the situation of fixed pump rotation speed are proper way will improve the system performance. In addition, when the rotation speed of pump raises, the power of expander and thermal efficiency of system is also higher than the original design.