石墨烯奈米冷卻液應用於熱交換模擬平台與機車引擎性能之研究

Abstract

使用市售用改質親水性石墨烯添加到機車原廠冷卻液製備成不同重量百分濃度之石墨烯奈米冷卻液(GrNC)，並加入羧甲基纖維素(CMC)作為流體分散劑增加穩定性。分別進行沉降、黏度、比熱、導熱與磨潤等基礎性質實驗，依據實驗數據進行綜合性能分析評比並選出最佳濃度之GrNC後續進行熱交換模擬平台與實車性能之實驗。以原廠冷卻液為對照組與GrNC進行比較，沉降試驗為0.01 wt.%與0.07 wt.% GrNC表現較佳，可穩定至10天；黏度試驗0.09 wt.% GrNC改善了20.93 %；比熱試驗0.01 wt.% 與0.07 wt.% GrNC增加1.2 %與3.1 %；導熱試驗GrNC導熱值優於原廠冷卻液，0.01 wt.% 和0.09 wt.% GrNC導熱係數增加28.22 %和36.18 %；磨潤試驗結果GrNC可以減少磨耗量，0.01 wt.%和0.07 wt.% GrNC為最佳，分別改善6.89 %和7.34 %。由前述基礎實驗數據結果進行綜合分數評比，最終選定0.01 wt.%和0.07 wt.% GrNC作為後續熱交換模擬平台與實車性能實驗流體。使用GrNC為熱交換模擬平台工作流體來試驗水箱散熱性能與引擎暖車試驗中，與原廠冷卻液進行比較。得到在60 ℃時0.01 wt.%與0.07 wt.% GrNC散熱量提升5.19 %和8.01 %；80 ℃時散熱量分別改善8.42 %與19.51 %。且GrNC能加速流體加熱時間，0.01 wt.%與0.07 wt.% GrNC在60 ℃分別改善6.12 % 和8.74 %；80 ℃時改善7.56 %與8.68 %。而在實車性能ECE-40、定速、平路與爬坡試驗中，GrNC與原廠冷卻液比較，在溫度、扭矩、廢氣與PM排放各方面均有改善趨勢。0.01 wt.%與0.07 wt.% GrNC在散熱水溫差平均改善7 % 和16.18 %；機油溫度平均提升5.35 % 和3.52 %；齒輪油溫度平均提升7.8 % 和17 %；平路與爬坡瞬間扭矩GrNC平均提升87 % 和122 %。廢氣排放實驗，與原廠冷卻液比較0.01 wt.%與0.07 wt.% GrNC在HC排放中分別減少15.64 % 和14.46 %；CO減少53.9 % 與50.6 %；CO2增加23.59 % 與34.8 %。在PM總量排放方面，定速時分別減少31.45 % 和8.22 %；平路時分別減少29.76 % 和49.37 %；爬坡時分別減少38.57 % 和45.96 %。In the present work, commercial modified hydrophilic graphene was added to a conventional automotive coolant to prepare different weight-percentage concentrations of graphene nano-coolant (GrNC). Carboxymethyl cellulose (CMC) was also added to act as a fluid dispersant for increased stability. Standard property tests were conducted to measure sedimentation, viscosity, specific heat capacity, heat conduction, and tribology. A comprehensive performance evaluation was then carried out based on the collected data in order to select the most optimal GrNC concentrations for further testing through heat transfer simulation platforms and on-road vehicle performance tests.A conventional automotive coolant was designated as the control group to compare with the various concentrations of GrNC. Sedimentation testing indicated that GrNC concentrations of 0.01 wt.% and 0.07 wt.% performed better than the control group and were stable for up to 10 days. Viscosity testing indicated 0.09 wt.% GrNC yielded a 20.93 % improvement. Specific heat testing indicated 0.01 wt.% GrNC showed a 1.2 % improvement, while 0.07 wt.% GrNC showed an improvement by 3.1 %. Thermal conductivity tests indicated the thermal conductivity of GrNC was superior to the control group coolant. 0.01 wt.% GrNC showed a 28.22 % increase, while 0.09 wt.% GrNC showed an increase of 36.18 %. Tribological testing indicated 0.01 wt.% and 0.07 wt.% GrNC were the most optimal concentrations for reducing wear, yielding an improvement by 6.89 % and 7.34 %, respectively. The aforementioned test results were evaluated through comprehensive performance analyses, and 0.01 wt.% and 0.07 wt.% GrNC were selected for further studying through heat exchange simulations and on-road vehicle tests.GrNC was used as the working fluid in a series of heat exchange simulations to measure both radiator heat dissipation performance and engine warm-up performance. A conventional automotive coolant was designated as the control group. At 60 ℃, the heat dissipation capacity of 0.01 wt.% GrNC was higher by 5.19 %, while 0.07 wt.% GrNC was higher by 8.01 %. At 80 ℃, heat dissipation capacity was higher by 8.42 % and 19.51 %, respectively. Both concentrations were also shown to effectively shorten the time taken for GrNC to reach operating temperatures. At 60 ℃, 0.01 wt.% GrNC showed an improvement by 6.12 %, while 0.07 wt.% GrNC showed an improvement by 8.74 %. At 80 ℃, both yielded an improvement by 7.56 % and 8.68 %, respectively.Drive cycle testing ECE-40 under constant speed, on a flat road, and hill climbing were conducted to measure the performance of GrNC and the control group coolant. The results for GrNC revealed that there was an improvement in temperature, torque, exhaust gas, and PM emissions for both concentrations over the control group. On average, 0.01 wt.% GrNC showed a 7 % improvement in heat dissipation water temperature difference, while 0.07 wt.% GrNC showed a 16.18 % improvement. Engine oil temperature for 0.01 wt.% GrNC was on average 5.35 % higher, while 0.07 wt.% was 3.52 % higher. Gear oil temperature for 0.01 wt.% GrNC was higher by an average of 7.8 %, while 0.07 wt.% was higher by an average of 17 %. The instant torque on flat roads and climbing for both 0.01 wt.% and 0.07 wt.% GrNC was higher by an average of 87 % and 122 %, respectively. Exhaust gas emission testing indicated that HC emissions for 0.01 wt.% GrNC were 15.64 % lower than the control group, while 0.07 wt.% GrNC were 14.46 % lower; CO emissions were lower by 53.9 % and 50.6 %; and CO2 emissions were higher by 23.59 % and 34.8 %, all respectively. Total PM emissions were reduced by 31.45 % and 8.22 % at constant speed; 29.76 % and 49.37 % on flat roads; and 38.57 % and 45.96 % while climbing, respectively.