以ε-NTU法分析間接蒸發冷卻性能之研究

Performance Analysis of Indirect Evaporatively-cooled Device by ε-NTU Method

游純榮(CHUN-JUNG YU)

指導教授 ： 柯明村

國立臺北科技大學/機電學院/冷凍與低溫科技研究所/碩士(2012年)

摘要

本研究經由空氣與水的熱質傳分析並以ε-NTU分析間接蒸發式冷卻模組材料之性能計算，間接蒸發式冷卻為採用絲瓜纖維模組，利用不同厚度5公分、10公分及15公分來分析其性能。
利用絲瓜纖維模組將吸水附在其表面，使其表面常保持濕潤狀態，其目的在使空氣經過間接蒸發冷卻模組時因水分子壓差與溫度差，而造成熱傳遞與質傳遞現象。
本模組實際安裝於氣冷式為實驗改善目標，於冷凝器前加裝間接蒸發式冷卻系統，利用水噴灑在不同厚度之材料，經由空氣通過，而造成蒸發冷卻，產生熱傳與質傳現象，使空氣溫度降低，緊接進入後方鱨管式冷凝器，使冷凝器性能提高，降低空調耗電量。
依所測所得之數據顯示，顯示其中以15cm厚絲瓜纖維模組有較好之性能，當日最大有2.95℃溫差效果，ε有效性（冷卻效率）為55％、NTU傳遞單位數為0.8％；其次為10cm厚絲瓜纖維模組。
經現場實際量測與ε-NTU之計算，求出熱傳遞係數h_C、質傳遞係數h_m、材料濕總面積A_s及各種熱傳數據，並經由現場實際量測，來分析絲瓜纖維模組不同厚度之性能差異，以求得最佳設計與尺寸。

關鍵字

間接蒸發式冷卻 ； 熱傳 ； 質傳 ； ε-NTU法

並列摘要

In this study, heat and mass transfer analysis by air and water, and ε-NTU method were used to analyze the performance of the loofah fiber modules applied to indirect evaporatively cooled device. The thickness of respectively, the modules were 5, 10 and 15 cm.
Because the loofah fiber module can absorb water and keep its surface moist, it can cause heat and mass transfer phenomenon by the pressure of water molecules and the temperature difference as air flow through the indirect evaporatively-cooled device.
The module was installed in front of an air-cooled condenser for energy improvement experiment. Water was sprayed on different thickness of materials. As air flow though it, the module caused evaporative cooling, and heat and mass transfer phenomenon, so that the air temperature decreased. As the air entered the fin tube condenser immediately, the condenser performance was improved, and air conditioning power consumption was reduced.
In the measurement results, 15 cm thick of loofah fiber module had better performance, with maximum temperature difference of 2.95 ℃ in a day, effectiveness of ε (cooling efficiency) of 55%, and number of transfer(NTU) of 0.8%; the next was 10 cm thick loofah fiber module.
In actual measurement and ε-NTU calculation, the heat transfer coefficient(h_C), mass transfer coefficient(h_m), the total area of the material wet (A_s)and all kinds of heat transfer data was obtained. By analyzing the actual measurement to analyze the performance of the different thickness of loofah fiber module, the best design and size were obtained in this study.

並列關鍵字

Indirect Evaporatively-cooled Device ； Heat transfer ； mass transfer

參考文獻

[1] Hsu, S.T. and Lavan, Z.” OPTIMIZATION OF WET -SURFACE HEAT EXCHANGERS”, Energy Vol. 14, No. 11, pp.757-770, 1989.

[2] Camargoa, J.R. Ebinumab C.D. and Silveirab J.L. “Experimental performance of a direct evaporative cooler operating during summer in a Brazilian city” ,Int. J. of Refrigeration,Vol.28,pp. 1124–1132,2005.

[3] Wu, J.M., Huang, X.,Zhang, H., “ Numerical investigation on the heat and mass transfer in a direct evaporative cooler”, Applied Energy,Vol.29, No. 1, pp. 195-201, 2009.

[4] Ala, H., “Going below the wet-bulb temperature by indirect evaporative cooling: Analysis using a modified ε-NTU method”, Applied Energy,Vol.89, No. 1,pp. 237–245,2012.

[6] Jain, J.K., Hindoliya D.A., “Experimental performance of new evaporative cooling pad materials”, Sustainable Cities and Society ,Vol.1, No. 4,pp. 252–256,2011.