Investigation of Thermoelectric Module with Applications on Waste Heat Recovery from Automobile Engine

超過三分之二的汽車燃料被消耗後將排放到環境中成為廢熱。利用熱電發電器(TEG)使熱能轉換成電能可以使燃料的使用更有效率。本研究將TEG結合排氣管及冷卻水箱作為熱電模組以提高內燃機的效率。為了預測熱電模組的性能，藉由使用一維熱組模型，數值模擬和實驗分析TEG冷熱端溫差，輸出功率及熱效率。影響系統效率之控制參數為引擎轉速，冷卻水溫及熱沉鰭片的長度。 實驗結果顯示，HZ-2在290℃時所輸出的最大功率為51.13 mWcm-2，熱電模組應用在排氣管的性能比在冷卻水箱佳。隨著引擎轉速的增快及冷卻水溫的增加，TEG冷熱端的溫差、輸出功率和熱效率也隨之增加。最大輸出功率分別在引擎轉速2000rpm和冷卻水溫90℃時。由熱電模組結合不同熱沉鰭片長度的模擬中顯示，在引擎轉速2000rpm時，熱沉鰭片為75%原熱沉鰭片長度可使TEG冷熱兩端產生最大溫差102 ℃。Over two-thirds energy of fuel consumed by an automobile is discharged to the surroundings as waste heat. The fuel usage can be more efficient if thermoelectric generators (TEG) are used to convert heat energy into electricity. In this study, a thermoelectric module composed of thermoelectric generators with an exhaust pipe and radiator is developed to improve the efficiency of an IC engine. In order to predict the performance of this module, by using a one dimensional thermal resistance model, numerical simulation and experiment to analyze the temperature difference between cold and hot sides, output power and thermal efficiency of TEG. The engine speed, the temperature of cooling water and the fin length of heat sink are examined as three variables affecting the efficiency of this system. The experimental results show that, the maximum power produced from HZ-2 is 51.13 mWcm-2 at 290℃ temperature difference. TE module presents better performance on the exhaust pipe than on the radiator. The temperature difference between the hot and cold sides of TEG increases with the increasing of engine speed and coolant temperature. The output voltage, output power and thermal efficiency will also increase. The maximum output power occurs at the highest engine test speed 2000 rpm and cooling temperature 90℃. As for the simulation of the TEG module with different fin length of heat sinks indicates, at 2000 rpm engine speed, the highest temperature difference 102 ℃ between both sides of TEG occurs when using a heat sink with fins only 75% base length long