鰭管式熱交換器空氣側的熱傳與質傳特性

Airside Heat and Mass Characteristics of Fin-And-Tube Heat Exchangers

The airside heat transfer performance of three plain-fin and four slit-fin heat exchangers under dehumidifying conditions was examined in this study. Parameters of tube row number, fin pitch, fin type, inlet cold water temperature and frontal velocity of air are considered. The total heat transfer rate, including sensible and latent heats, and sensible heat factor are obtained by experiment. The test results indicate that the heat transfer rates of the test coils increase with air inlet velocity and fin numbers. The sensible heat factors are found to increase with both Reynolds number and inlet temperature of cold water. As for the dehumidifying conditions, the condensing rate for the humid air increases with Reynolds number but decreases as the inlet temperature of cold water increases. In addition, the heat transfer rate and the ability of dehumidification for slit-fin-type heat exchangers are superior to the plain-fin-type coils. 本文使用吸入型開放式風洞測試系統，針對三種平板型和四種裂口型鰭管式熱交換器在不同的鰭片間距、管排數及鰭片型式下，分別固定冰水進口溫度及正向風速，進行濕盤管測試實驗，以了解測試系統和此類熱交換器的熱傳性能及空調特性。實驗中，固定冰水進口溫度及流量，改變空氣的正向風速；或固定正向風速時，改變冰水的進口溫度，分別來探討熱傳量、顯熱量、潛熱量、顯熱比及除濕率的變化。由實驗結果發現，濕盤管有水凝結現象的發生。由實驗數據得知濕盤管總熱傳量中，潛熱量的變化佔了大部分。濕盤管的熱傳量隨著入口風速與鰭片數目的增加而增加，顯熱比及除濕率亦隨著風速增加而增大。同時濕盤管的熱傳量及除濕率亦也隨著冰水入口溫度的降低而增加，顯熱比隨著冰水溫度的降低而減小。此外，裂口鰭片型式的熱傳量及除濕率均高於平板鰭片型式的熱交換器。