融冰式空調裝置開發及性能分析

Abstract

本研究開發了兩種融冰式空調裝置，分別是自然對流融冰空調裝置和強制對流融冰空調裝置，並以數學建模和實驗驗證進行系統分析。 在自然對流融冰空調裝置的研究中，主要探討了鰭片厚度、流道寬高比(α)及空氣流速對鰭片溫度分佈、熱傳率及鰭片效率的影響。結果顯示，固定鰭片厚度與流道寬高比的條件下，隨著空氣流速的增加，鰭片溫度明顯上升。固定空氣流速與流道寬高比時，增加鰭片厚度可有效降低鰭片整體溫度，提升溫度分佈均勻性。當鰭片厚度固定為3mm時，且風速保持不變時，α之提高，相同位置下之鰭片溫度將下降。若鰭片厚度固定為3mm時，隨風速的提升，所有流道寬高比之溫度分佈曲線趨於重疊；熱傳率的表現上，於α=2/15時，無論鰭片厚度為何，鰭片熱傳率均隨風速提高而增加。然而，在高風速區（V=3.0~4.0 m/s），熱傳率有趨於飽和的現象，當風速為5m/s時，鰭片厚度從1mm增加至2mm，熱傳率提升41.6%；但鰭片厚度從4mm增加至5mm，熱傳率僅提升8.5%。在固定空氣流速和流道寬高比的條件下，熱傳率隨鰭片厚度提高而增加，但隨著鰭片厚度增加，熱傳率增幅逐漸減少。當鰭片厚度固定為3mm時，定風速下，熱傳率隨α增加而下降；鰭片效率方面，當α=2/15且空氣流速1.0 m/s時，鰭片厚度從1mm增加至5mm，鰭片效率提升了30.6%。然而，鰭片厚度從1mm增加至5mm，鰭片效率僅提升了5.2%。另外，鰭片厚度3mm時，任何風速下改變流道寬高比對於鰭片效率的影響並不顯著。 在強制對流融冰空調裝置的研究中，分析了冰堆厚度和出水溫度隨時間的變化，以及各操作時間下冰粒粒徑和滲透水溫隨深度之變化。結果顯示，在系統操作的前30分鐘內，冰堆厚度幾乎沒有變化。隨著時間推移，冰堆厚度逐漸減少，至180分鐘時冰層厚度由初始之60公分縮減至約13公分，頂層冰粒幾乎完全融化。操作至250分鐘時，100%融冰。在出水溫度的表現上，系統操作初期，冰水溫度易受到槽體底部冰粒聚集於水泵抽吸口的影響，出現不穩定現象。當操作時間達到60分鐘後，隨著槽體底部水的量體增加，供水溫度趨於穩定，在槽體內有冰的情況下，系統可持續供應約2°C的冰水。至250分鐘後，槽體內的冰完全融化，潛熱已全部釋放，因此水溫開始上升；冰粒粒徑在深度變化表現上，在時間30分鐘時，冰粒在深度方向上的粒徑幾乎保持不變。隨著時間之推進，各深度下之冰粒粒徑則不斷下降；至於滲透水在各操作時間下，其水溫在深度方向上的變化，由數據可以得知，滲透水溫度隨著深度的增加而逐步降低。隨著系統操作時間增加，冰堆深度減少，導致回滲透水的冷卻流路縮短，在操作時間150分鐘內，冰堆厚度約25公分，底層滲透水溫度約為2°C。但180分鐘後，冰堆厚度不足以充分冷卻滲透水，底層水溫度升至2.5°C。 此外，本研究還建立了示範系統，利用實際操作評估其性能和節能效果。結果表明，在示範案例中，使用太陽光電+製冰機+融冰空調裝置的空調模式，相較於傳統分離式空調系統，節電率達到88.4%。示範系統中，製冰機主要依賴太陽光電供電，僅在太陽光電不足時才使用市電，顯著降低了市電耗量。

This study developed two types of ice-melting air conditioning systems: a natural convection ice-melting air conditioning system and a forced convection ice-melting air conditioning system. Systematic analyses were conducted through mathematical modeling and experimental validation. In the study of the natural convection ice-melting air conditioning system, the effects of fin thickness, channel aspect ratio (α), and air velocity on fin temperature distribution, heat transfer rate, and fin efficiency were investigated. The results showed that, under fixed conditions of fin thickness and channel aspect ratio, fin temperature significantly increased with the increase in air velocity. When air velocity and channel aspect ratio were fixed, increasing the fin thickness effectively reduced the overall fin temperature and improved the uniformity of temperature distribution. When the fin thickness was fixed at 3 mm and the air velocity was constant, an increase in α led to a decrease in fin temperature at the same location. If the fin thickness was fixed at 3 mm, the temperature distribution curves for all channel aspect ratios tended to overlap as air velocity increased. Regarding heat transfer rate, under α=2/15, the heat transfer rate of the fin increased with increasing air velocity, regardless of fin thickness. However, in the high-velocity range (V=3.0~4.0 m/s), the heat transfer rate tended to saturate. When the air velocity was 5 m/s, increasing the fin thickness from 1 mm to 2 mm enhanced the heat transfer rate by 41.6%, but increasing the fin thickness from 4 mm to 5 mm only increased the heat transfer rate by 8.5%. Under fixed air velocity and channel aspect ratio conditions, the heat transfer rate increased with increasing fin thickness, but the rate of increase gradually decreased with thicker fins. When the fin thickness was fixed at 3 mm, the heat transfer rate decreased as α increased under constant air velocity. In terms of fin efficiency, when α=2/15 and air velocity was 1.0 m/s, increasing the fin thickness from 1 mm to 5 mm improved fin efficiency by 30.6%. However, increasing the fin thickness from 1 mm to 5 mm only improved fin efficiency by 5.2%. Additionally, when the fin thickness was 3 mm, changing the channel aspect ratio had no significant effect on fin efficiency at any air velocity. In the study of the forced convection ice-melting air conditioning system, the changes in ice heap thickness and outlet water temperature over time, as well as the variations in ice particle size and permeating water temperature with depth at different operation times, were analyzed. The results indicated that the ice heap thickness remained almost unchanged within the first 30 minutes of system operation. As time progressed, the ice heap thickness gradually decreased, reducing to about 13 cm at 180 minutes, with the top layer of ice particles almost completely melted. By 250 minutes, the ice in the storage tank was entirely melted. Regarding outlet water temperature, the ice water temperature was initially unstable due to the accumulation of ice particles at the suction port of the pump at the bottom of the tank. After 60 minutes of operation, as the water volume at the bottom of the tank increased, the supply water temperature stabilized. When there was ice in the tank, the system could continuously supply ice water at approximately 2°C. After 250 minutes, all the ice in the tank melted, the latent heat was fully released, and the water temperature began to rise. In terms of ice particle size variation with depth, at 30 minutes, the ice particle size remained almost constant in the depth direction. Over time, the ice particle size at each depth decreased continuously. For permeating water, its temperature gradually decreased with depth at different operation times. As system operation time increased, the depth of the ice heap decreased, shortening the cooling path of the returning permeating water. Within 150 minutes of operation, the ice heap thickness was about 25 cm, and the bottom layer permeating water temperature was around 2°C. However, after 180 minutes, the ice heap thickness was insufficient to adequately cool the permeating water, raising the bottom layer water temperature to 2.5°C. Additionally, this study established a demonstration system to evaluate its performance and energy-saving effects through actual operation. The results showed that in the demonstration case, the air conditioning mode using solar photovoltaic (PV) + ice maker + ice-melting air conditioning system achieved an electricity saving rate of 88.4% compared to the traditional split air conditioning system. In the demonstration system, the ice maker primarily relied on solar PV power, using grid electricity only when solar PV was insufficient, significantly reducing grid electricity consumption.