有鑒於全球能源逐漸匱乏，國際油價不斷上漲，如何有效節約能源並找尋新的替代能源來減少化石燃料的依賴，實為當前急需解決的問題。大量使用化石燃料背後，對環境有害之污染也隨之上升，近幾年溫室效應所帶來的衝擊遠大於我們所想像，所以此等議題已不容再忽視。其中溫室氣體部份又以〖CO〗_2與〖CH〗_4為最大宗，所以若能藉由〖CH〗_4與〖CO〗_2直接回收再利用，不但有助於溫室效應之改善，並可提供能源應用，能將廢熱有效的運用而不直接排放到環境中，那是我們想要達成的目標。

在本研究中也會介紹熱交換器的設計方法，探討文獻關於熱交換器之設計或應用，例如平行流動、逆向流或交錯流的熱交換器之差異，熱交換器種類繁多，但實驗中考慮到空間限制，而且在研究中目的是為了沼氣引擎的廢熱回收，所以使用的熱交換器遠比工業上使用的熱交換器還小許多，另外也考慮到熱傳面積的問題所以在結構方面使用的是鰭片式的熱交換器目的是為了能增加更多的熱傳面積並且流動方式為交錯流，實驗流體為空氣(高溫流體)及純水(低溫流體)的熱交換，利用鼓風機提供進氣量及加熱槍提供熱源(模擬一般引擎之排氣溫度)，並將室溫水加熱到所需的溫度(50℃~60℃)，除了溫度的考量以外進氣流量、進氣溫度、水量也是影響熱回收效率的因素，計算熱回收效率，提供的熱能與回收到的熱能比值為計算基礎，此外比較溫度、流量大小與熱效率的關係，在應用方面，目的是希望能將回收到的熱能應用在厭氣發酵的製作過程，屬於沼氣的循環系統回收利用。

In view of the lack of global energy depletion and the rising oil prices, how to effectively save energy and find new alternative energy sources to reduce the dependence on fossil fuels is an urgent issue to be solved. Behind the heavy use of fossil fuels, environmentally harmful pollution has also risen. The impact of the greenhouse effect in recent years is far greater than we imagined, so these issues can no longer be ignored. Among them, the greenhouse gas part is 〖CO〗_2 and 〖CH〗_4 is the largest, so if you can directly recycle and reuse 〖CH〗_4 and 〖CO〗_2, it will not only contribute to the improvement of the greenhouse effect, but also provide energy.

In this study, we will introduce the design method of heat exchangers, and explore the literature on the design or application of heat exchangers, such as the difference of heat exchangers of parallel flow, reverse flow or staggered flow. There are many types of heat exchangers, but in the experiment considering the space limitation, and the purpose of the research is to recover the waste heat of the biogas engine, the heat exchanger used is much smaller than the heat exchanger used in the industry, and the heat transfer area is also considered. The finned heat exchanger is used to increase the heat transfer area and the flow pattern is a staggered flow. The experimental fluid is heat exchange between air (high temperature fluid) and pure water (cryogenic fluid), which is provided by a blower. The intake air amount and the heat gun provide a heat source (simulating the exhaust temperature of the general engine), and heat the room temperature water to the required temperature (50° C -60 ° C). In addition to the temperature considerations, the intake flow rate, the intake air temperature, and the water amount are also Factors affecting heat recovery efficiency, calculate heat recovery efficiency, provide thermal energy and recovered thermal energy ratio as the basis for calculation, and compare temperature, flow rate and thermal efficiency. The relationship between the rates, in terms of application, is intended to apply the recovered thermal energy to the production process of anaerobic fermentation, which belongs to the recycling system of biogas.

[1] Bhaskor JB, Ujjwal KS, Soumya C, Vijay V. Effect of compression ratio on performance, combustion and emission characteristics of a dual fuel diesel engine run on raw biogas. Energy Conversion and Management, 2014; 87:1000–1009.

[2] Choongsoo J, Jungsoo P, Soonho S. Performance and NOx emissions of a biogas-fueled turbocharged internal combustion engine. Energy, 2015; 86:186-195.

[3] 宋柏毅,「低溫熱電廢熱回收應用」,工業技術研究院,(2015)

[4] 陳竑鋻,「高溫高壓同心圓熱交換器幾何設計與分析」,國立台北科技大學機電整合研究所碩士論文,(2013)

[5] http://www.eeoa.org.tw/download/boilers_00-4.pdf 廢熱回收節能技巧中鼎工程

[6] Van Den Buick, E., Optimal design of cross flow heat exchangers. Journal of Heat Transfer, 1991, 113, 341- 347.

[7] Egrican, N., A heat exchanger design method based on the second law of thermodynamics. Journal of Engineer and Machine, 1989, 30/354, l&16.

[8] https://zh.scribd.com/document/269536907/Thermal-Design-of-Heat-Exchangers，國立交通大學王啟川教授

[9] B. E.Launder and D. B. Spalding, Mathematical Models of Turbulence, Londn: Elsevier Inc,1972,pp.90-100

[10] Chen, Y-S., and S-W. Kim. "Computation of turbulent flows using an extended k-epsilon turbulence closure model." (1987).

[11] Wang, Ten-See, and Yen-Sen Chen. "Unified Navier-Stokes flowfield and performance analysis of liquid rocket engines." Journal of Propulsion and Power 9.5 (1993): 678-685.
[12] CFD ANALYSIS OF CROSS FLOW AIR TO AIR TUBE TYPE HEAT EXCHANGER Vikas Kumar 1* , D. Gangacharyulu2*, Parlapalli MS Rao3 and R. S. Barve 4

[13] B.Tech Thesis on SHELL AND TUBE HEAT EXCHANGER DESIGN USING CFD TOOLS For partial fulfilment of the requirements for the degree of Bachelor of Technology in Chemical Engineering Submitted by Anil Kumar Samal Roll

[14] MODELLING AND PERFORMANCE ANALYSIS OF A CROSS-FLOW TYPE PLATE HEAT EXCHANGER FOR DEHUMIDIFICATION/COOLING W. Y. SAMAN and S. ALIZADEH† Sustainable Energy Centre, The University of South Australia, School of Mechanical Engineering, Levels Campus, S.A. 5095, Australia Received 15 November 1999; revised version accepted 19 July 2000 Communicated by HANS-MARTIN HENNING

[15] Edward Chen Gustav Nyman Member, IEEE Member, IEEE TECO-Westinghouse Motor Company Heatex America 5100 North IH-35 70 Douglas Way Round Rock, TX 78681 Natural Bridge Station, VA 24579 USA ,Using plate heat exchanger (PHE) for totally enclosed air-to-air cooled (TEAAC) motor, 19-22 Sept. 2016.

[16] Fundamental of heat exchanger design/Ramesh K. Shah and Dusan P. Sekulic

[17] C. Liu, Y.D. Deng, X.Y. Wang, X. Liu, Y.P. Wang, C.Q. Su Multi-objective optimization of heat exchanger in an automotive exhaust thermoelectric generator

[18] J.C. Bass, N.B. Elsner, F.A. Leavitt, Performance of the 1 kW thermoelectric generator for diesel engines, AIP Conference Proceedings, IOP Institute of Physics Publishing LTD, 1995, p. 295.

[19] T. Wang, W. Luan, W. Wang, et al., Waste heat recovery through plate heat exchanger based thermoelectric generator system, Appl. Energy 136 (2014) 860–865.

[20] Theory and experimental validation of cross-flow micro-channel heat exchanger module with reference to high Mach aircraft gas turbine engines Robert Nacke, Brittany Northcutt, Issam Mudawar

[21] Comparison between Wet and Dry Anaerobic Digestions of Cow Dung under Mesophilic and Thermophilic Conditions. Ajay Kumar Jha, Jianzheng Li, Liguo Zhang, Qiaoying Ban and Yu Jin

[22] Effect of long residence time and high temperature over anaerobic biodegradation of Scenedesmus microalgae grown in wastewater. S. Greses a, * , N. Zamorano-Lopez , L. Borras, J. Ferrer b , A. Seco , D. Aguado

[23]http://www.cngspw.com/Doc/BBS/13/200812/200812081634492226/u70EDu4EA4u6362u5668u4F7Fu7528u6548u7387u63D0u5347u6280u672Fu624Bu518C.pdf熱交換器使用效率提升技術手冊/經濟部工業局/財團法人工業技術研究院環境與安全衛生技術發展中心/執行單位 國立清華大學.

[24] Structural size optimization on an exhaust exchanger based on the fluid heat transfer and flow resistance characteristics applied to an automotive thermoelectric generator. Wei He , Shixue Wang , Yanzhe Li , Yulong Zhao

[25] https://tw.1688.com/pic/-C1D0B9DCCABDC8C8BDBBBBBBC6F7.html

[26] http://www.tc-heat.com.tw/view_case.php?id=91

[27] http://yp.518.com.tw/product-prod_info.html?rid=2&a=1822396&sr=7036