超臨界二氧化碳在多迴路板式熱交換器中的熱流場之數值分析

Abstract

本研究旨在開發以二氧化碳為工作流體的多通道板式熱交換器模擬程式，模擬內容包括二氧化碳在Z型以及多通道（1-2 pass）板式熱交換器中的流速分佈、壓降及熱傳等。模擬條件包括冷媒（CO2）及水側的質量流率、入口壓力、板片數量以及不同的板片等。模擬結果顯示在水對二氧化碳多通道板式熱交換器中，二氧化碳流場由於超臨界二氧化碳的物性變化相當劇烈(尤其是臨界點附近)，因此密度及黏滯係數所造成的影響將不可忽略,而水的物性隨溫度變化並不明顯。同時本研究藉由比較分析不同流動形式以及單通道與多通道之間各自熱傳特點，對熱交換器的設計及改進提供較大幫助。

In the present study, a numerical simulation program of multi-pass plate heat exchanger is developed and the pressure drop, velocity distribution and temperature of both water and supercritical carbon dioxide in a plate heat exchanger are calculated with different mass flow rate, inlet pressure, inlet velocity, inlet temperature, number of channels and different plates. As a result of simulation, the physical properties of carbon dioxide vary drastically at supercritical state in that the density and viscosity of the impact cannot be ignored. The flow distribution of water, however, did not change significantly with temperature. Besides, the heat transfer effect will be significantly improved by analysis results from some comparisons between U and Z-type, single and multi-pass during the designing process of plate heat exchanger.