淺層溫能應用於養液薄膜技術之熱傳分析與最佳化設計

The Thermal Analysis and Optimization of Nutrient Film Technique with Shallow Geothermal Energy

張皓崴(Hao-Wei Chang)

指導教授 ： 陳希立

國立臺灣大學/工學院/機械工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201703032

摘要

養液薄膜技術為水培種植的一種，相對於其它水培法其可進行溫度控制。本研究目的為用熱傳分析推導出數學模型，且可以利用模型來預測不同操作條件下與不同環境負載下的溫度變化情形。本研究使用MATLAB模擬計算養液薄膜技術在夏季極端氣候的溫升情況，分析基於二維、穩態、不可壓縮流之質量、動量方程式以及熱阻分析模擬計算植栽管熱傳溫升現象；環境溫度在35 (°C)、植栽管頂部40 (°C)條件下，計算結果顯示只改變導入水溫度以及水流率，植栽管內水溫可以介於植栽管內目標溫度15~24 (°C)，但植栽管內氣溫無法到達目標溫度且差距不小。因此必須更改硬體設備參數進行多參數最佳化設計，本文應用實驗設計法中的田口法結合灰關聯分析，設計因子為熱泵之散熱源溫度、水流量、植栽管寬度、植栽管入口水溫度以及植栽管斜度，綜合探討植栽管內氣溫與耗能考慮情況之最佳參數組合。數值模擬結果顯示植栽管內氣溫與耗能最佳參數配置為地下水散熱之熱泵、水流量2 (L/min)、植栽管寬度0.06 (m)、植栽管入口水溫度16 (°C)以及植栽管斜度4 %，植栽管最高水溫由21.66 (°C)減少至17.87 (°C)，植栽管最高氣溫由30.65 (°C)減少至25.14 (°C)，植栽管總耗能減少53%，其中淺層溫能在節能量中佔了43 %相當高之貢獻度，從模擬運轉情況得知使用淺層溫能取代傳統冷卻水塔之建製費用回收年限大約5個月，且每個月能減少約1,000 (kg)的碳排放量。

關鍵字

淺層溫能 ； 養液薄膜技術 ； 最佳化設計 ； 田口法 ； 灰關聯分析

並列摘要

Temperature of Nutrient Film Technique(NFT) is one of the types of Hydroponics. As compared to other Hydroponics, it can be controlled by temperature. The purpose of this study is to derive the mathematical model by heat transfer analysis, and the model can be used to predict the changes of the temperature with different operating and environmental conditions. This study used MATLAB to simulate the changes of the temperature of NFT during the summer time based on Steady State, Incompressible Flow, Navier-Stokes equations, and Thermal Resistance Analysis. According to the results of numerical analysis, with 35 °C ambient temperature and 40 °C the top of the planting tube, if we only change the input water temperature and its flow rate, the temperature of the water in the planting tube can reach the target temperature (15 ~ 24 °C), but the temperature of the air in the planting tube cannot reach the target temperature. Therefore, we need to change the parameters of hardware to optimize the design. This study used Taguchi Method and Gray Relation Analysis to approach the optimum parametric combination, with the considering of the temperature of NFT and the power consumption. The parameters include cooling method of heat pump, volume flow rate of water, wide of planting tube, temperature of inlet water of planting tube, and slope of planting tube. The result show, cooling method of heat pump with Shallow Geothermal Energy, volume flow rate of water of 2 (L/min), wide of planting tube of 0.06 (m), temperature of inlet water of planting tube of 16 (°C), and slope of planting tube of 4 % is the best in all level for system. According to the results of optimization, the highest temperature of water of inside planting tube of 21.66 (°C) can be reduced to 17.87 (°C), the highest temperature of air of inside planting tube of 30.65 (°C) can be reduced to 25.14 (°C), and power consumption of planting tube can save 53%. Shallow Geothermal Energy accounts for 43% of the contribution in the saving energy. According to the results of simulating operation, it's payback period is 5 months, and it can reduce carbon emission by 1,000 (kg) monthly.

並列關鍵字

shallow geothermal energy ； Nutrient Film Technique ； Optimization ； Taguchi Method ； Gray Relation Analysis.

參考文獻

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