大管徑波浪型鰭管式熱交換器空氣側性能研究

Abstract

熱交換器（蒸發器或冷凝器）是冷凍系統中最重要的熱量傳送元件，其主要 工作是將室內側的熱負荷排放至室外側環境中。熱交換器熱傳效率的好壞， 對整個系統設備整體性能會有大的影響。過去以來，學術界及工業界一直致 力於研究如何增強熱交換器的熱傳性能，提高整個系統設備的能源效率；另 外也要求熱交換器的尺寸縮小，以降低成本，增加競爭力。空調系統的基本 原理作用包括了四個基本元件，冷媒壓縮機、冷凝器、膨脹設備、蒸發器等。 而其中蒸發與冷凝的過程，都必須使用熱交換器，因此鰭管式熱交換器性能 的好與壞，與整個空調系統有著密切關係。以氣冷式熱交換器而言，其熱交 換的主要目的在於對空氣的冷卻或加熱，而由於空氣的熱傳導係數相當的 小，因此要達到較好的熱傳效果，經常要增加熱交換器的鰭片面積，來解決 熱傳問題，因此熱交換器鰭片依其形狀大致可分成，平板型（plain fin）、百 葉窗型（louver fin）、波浪型（wavy fin）、及裂口型（slit fin）等，這些型 態的鰭片均可用於蒸發器（濕盤管）或冷凝器（乾盤管），在中大型熱交換 器中，由於考量長期運轉的信賴性，幾乎都不會選用有開孔的百葉窗與裂口 型鰭片，平板型與波浪是最常使用的鰭片，而且由於較大的能力需求，最常 使用橫向間距為38.1 mm、縱向間距為33 mm、管俓為5/8”（俗稱5 分管） 的鰭管式熱交換器。雖然此類熱交換器使用量相當的大，文獻上對於此類熱 交換器的性能研究卻是非常的少，應用上多藉由經驗設計，然而如果操作條 件有改變時，經常會出現設計過大或不足的現象，造成能源與材料的雙重浪 費。因此本計畫預期進行大管徑波浪鰭片的測試分析，讓設計者得以設計此 類熱交換器，本計畫第一年將進行乾盤管(如冷凝器、加熱盤管)的測試資料庫 的建立與相關分析，第二年則進行濕盤管(如蒸發器、送風盤管)的熱交換器的 測試資料庫的建立與相關分析(含高濕度85%與正常濕度50%)。

Heat exchanger is the major heat transport device applicable to heating/ventilation/air-conditioning and refrigeration systems (HVAC&R). Performance of heat exchanger is directly in connection to the overall performance of the whole system. Efforts were made in either academic or in industry to improve the performance of the system, especially in improving the energy efficiency and in reducing the material cost. There are four major components in HVAC&R system, namely compressor, condenser, evaporator, and expansion device. The process of condensing or evaporating requires heat exchanger. Hence, better design heat exchanger gives rise to higher system performance. One of the major types of heat exchangers uses air-cooling and normally in the form of fin-and-tube type. For practical application, the air side resistance plays the essential role and enhanced surface like wavy, louver, and slit were used to reduce the airside resistance. However, for commercial and industrious applications, louver or slit are generally not applicable due to concerns of reliability and fouling. Yet larger diameter tube such as 5/8” with Pt = 38 mm and Pl = 33 mm were often exploited due to needs of higher capacity. Unfortunately, the existing database for the performance of this kind of heat exchanger is simply unavailable. This is true for both dry coil (condenser) and wet coil (evaporator). In this regard, it is the objective of this project to provide sufficient information for this kind of heat exchanger using wind tunnel testing. The first year’s project aims to obtain the dry coil performance whereas the second year will conduct wet coil experiments with a normal humidity 50% and with a high humidity conditions (85%).