熱擠出頭之熱模擬分析

以三階段升溫，做為加熱順序的設計，並計錄其升溫過程中之電壓、電流變化。

最終達到 1300^oC 之功率需求為 187 W，電壓電流分別為 16.9 V、11.1 A，最後 在 510 s 時加熱至，可以加熱到 1300˚C，等同輸出電位 7.97 mV，如 Fig. 4.19(a) 所示，Fig. 4.19(b)則為 B-type 熱電偶之熱電動勢換算曲線圖。

在超過 700^oC 之高溫時，ME 組件多以輻射的方式傳出熱能，因此若能減少熱 輻射帶來的熱散失，相同電能需求下，即可增加中心溫度，並提高加熱速率，因 此，以橫向增加多孔材料如陶瓷纖維，耐火磚等設計，設計原理為利用纖維間分 布多為空氣，而空氣之熱傳係數非常低，為 0.026 Wm^-1K^-1，只要避免熱空氣的熱 對流，就能大幅減少熱傳導之熱散失。又過大之孔隙率容易造成強度的不足，因 而以外層支撐之澆注材，增加結構強度，因此，澆注材之煆燒密度不能太低，但 厚度也不能太厚，避免重量增加過多。最後，以熱影像儀紀錄熱擠出件在特定中 心溫度時之外圍溫度，如 Fig. 4.20(a)所示。其中，在 1300 ˚C 之中心溫度下，

擠出件外圍溫度僅有 200^oC，如 Fig. 4.20(b)所示，展現良好的熱絕緣效果，使用 之絕緣複材具有做為熱擠出件熱絕緣之潛力。

Fig. 4.14 Electrical conductivity plotted against temperature difference of three SiC heating elements.

(b)

Fig. 4.15 Schematic diagram of extrusion nozzle. (a) Assembly part and (b) exploded (a)

Table 4.5 Parameters and properties for thermal simulation

Parameter Value

Center temperature 1300 ˚C

Property Value

Thermal conductivity of SiC 126.0 𝑊𝑚⁻¹𝐾⁻¹ Thermal conductivity of ceramic fiber 0.17 𝑊𝑚⁻¹𝐾⁻¹ Thermal conductivity of castable 1.63 𝑊𝑚⁻¹𝐾⁻¹ Thermal conductivity of refractory board 0.21 𝑊𝑚⁻¹𝐾⁻¹

Fig. 4.16 Model establishment by meshing into quantitative triangle.

Fig. 4.17 Simulation results by ANSYS software. (a) Full part of previous design, (b) full part of new design, and (c) cross section of new design.

Fig. 4.18 Heating curve of extrusion nozzle.

(a)

(b)

(a)

(b)

Fig. 4.20 (a) Comparison between external temperature and center temperature of ME module, (b) thermal image of external temperature while 1300 ˚C center temperature.

4.3加熱基板組件設計

板之升溫特性與加熱均勻性，利用紅外光儀做為量測之工具。Fig. 4.22 顯示兩種

第四例為利用商用加熱基板(OVE heating plate, Solarceramic, Co.)測 試提升加熱面積的可能性，外觀如 Fig. 4.26(a)所示，最大加熱面積可達 20*12

cm²，加熱方式為利用於 Li2O-Al2O3-SiO2玻璃基板上加上兩端電極，加熱導電薄

於非接觸式之加熱，不會受到接觸電阻的影響使熱能損失。

Fig. 4.28(a)為使用之電磁加熱基板，可加熱之最大面積為直徑 18.0 cm 之圓 形面積，並以紅外線儀紀錄加熱區域及加熱溫度。不同電源供應之升溫曲線對時 間之關係圖如 Fig. 4.29 所示，此電源供應等級區別來自於磁通量變化的增加，當 磁通量變化越大，代表形成之渦電流強度越強，即可使金屬導體提升至更高溫度。

另外，鐵鎳金屬片以紅外線儀拍攝結果如 Fig. 4.28(b)所示，金屬導體本身之大小 為 10*10 cm²，然而在金屬導體中央部分之溫度較低，原因來自於受限於電磁感 應的磁通量為單一垂直方向的變化，由於電磁感應加熱基板中心並未纏繞銅線，

而使加熱區域受到限制，此為以電磁感應加熱之缺點。

Fig. 4.21 (a) Illustration of heating plate module, (b) two arrangements of heating wire.

Fig. 4.22 Equilibrium temperature plotted against various power supplying of two arrangements.

(a)

(b)

(a)

(b)

(c)

Fig. 4.24 Schematic diagrams of (a) series connection, (b) parallel connection, and (c) series/parallel connection of Ni-Cr heating wires for heating application.

(a)

(b)

(c)

(a)

(b)

Fig. 4.26 Pictures of (a) original connection, (b) new connection of OVE heating plate.

(a)

(b)

(a)

(b)

Fig. 4.28 (a) Picture of electromagnetic heating plate, (b) IR image of electromagnetic heating plate.

Fig. 4.29 Temperature of electromagnetic heating plate as a function of heating time with selected power output , which are the scale shown on control panel.

Fig. 4. 30 IR image of commercial heating plate module.

4.4 玻璃之熔融擠出 基座提供適當支撐強度與固定、一組步進馬達(TSM11Q-3RM, Applied Motion Products Inc., USA)提供固定轉速與力矩使進料量固定，其配線如 Fig. 4.32 所 示、一雙滾輪進料機構(D-Force, Taiwan)咬合玻璃胚料、以及 PLA 製作之步進 馬達支撐架定位步進馬達與進料機構位置。

一般雙滾輪機構為利用步進馬達帶動進料齒輪而與另一滾輪同時旋轉，將 ABS 及 PLA 等塑膠材料向下送入，此時因為塑膠材料相對於進料齒輪較軟，因此，

塑膠胚料得以卡入齒輪中，配合步進馬達之速度入料。然而，玻璃棒胚料無法卡 入進料齒輪，以及玻璃棒胚料本身較為平滑，因此以較少齒輪數(<20 齒)之進料

有微量鬆脫的可能。 (friction factor)[30] 。若以 Darcy Wesbach equation 計算在圓管內流體之 壓降變化，如式(4.1)所示：

之斷面圖示如 Fig. 4.36 所示，而本研究使用之氧化鋁料管可視為一尖銳邊緣之縮 0.88 kPa，此淨水壓力可克服表面張力造成之影響，然而，以長 300.0 mm、直徑 3.0 mm 計算中，剩餘之淨水壓力為 0.62 kPa，卻無法克服表面張力造成之影響，

壓降，並在一定高度中即停止流動，代表此淨水壓高度仍無法克服流體在氧化鋁

然而，目前於高溫熔融擠出中之案例顯示於 Table 4.10，其中調整之參數主

(a)

(b)

Fig. 4.31 Illustration of feeding system. (a) Assembly and (b) exploded drawing.

Fig. 4.32 Electric wiring plan of TSM11Q-3RM stepper motor.

Table 4.6 General commands of TSM11Q-3RM stepper motor

Command Full name Function

JS Jog speed Set the initial rotation speed in unit of rev/s SJ Stop jogging Stop the work

commanded by CJ CJ Commence jogging Started the command of

JS

CS Change speed As the CJ command started, CS could use for speed changing while rotating

(a)

(b)

Fig. 4.34 Schematic drawing of the extrusion tube, dimensions and notations for the pressure drop calculation.

Note：Pressure drop would endure a sharp edged contraction for a tube with a nozzle in a diameter of 0.4, 0.2, 0.1 mm at P2.

Table 4.7 Flow characteristic of water in 3 mm diameter tube

f is the same for all alumina tube, but not to plastic tube!

Note：

1. The direction of gravity was marked as negative.

2. Reynolds number was calculated by eq. 2.3.

3. Darcy friction factor was obtained from Moody Chart.

4. Pressure droplet was calculated by 𝑃₁− 𝑃₂ = 𝑓_𝑑^ℎ

0 𝜌𝑉𝑎𝑣𝑔2

2

Table 4.8 (a) Pressure drop contribution of 0.4 mm nozzle (b) Pressure drop contribution of 0.2 mm nozzle

(a)

Average velocity at P3 (cms^-1)

1. Loss coefficient was determined by geometry of sudden contraction tube.

2. Pressure droplet was calculated by 𝑃₂− 𝑃₃ = 𝐾_𝐿^𝜌𝑉₂^{𝑎𝑣𝑔2}

Fig. 4.36 Loss coefficient in sudden contraction flow.

Fig. 4.37 Flow rate with different length and nozzle diameter tested with water at 25 ˚C (a Newtonian fluid).

Fig. 4.38 Surface tension effect of discontinuity flow of three pictures tested with water at room temperature.

Fig. 4.39 Apparent viscosity plotted against of shear rate of pseudoplastic liquid in various concentrations.

(a)

(b)

Fig. 4.40 Pictures of extrusion of TN-SB 5 glass with (a) 1 mm nozzle, (b) 0.4 mm nozzle.

(a)

Fig. 4. 41 (a) Picture of Al2O3 nozzle coated by graphite paste, (b) TN-SB 5 glass strip extrusion from nozzle, and (c) picture of TN-SB 5 glass strip after cooling to room

(c)

(b)

Table 4.9 Parameters of extrusion of glass

Parameters Value

Heating element temperature 1050 ˚C

Nozzle power 120 W

Heating plate temperature 502 ˚C Heating plate power 50 W Nozzle diameter 0.4 mm Distance between nozzle and heating

plate

0.5 mm Average line rate 25 mms^-1

Table 4.10 Testing parameters and results of glass extrusion

Broken between two filaments

Case 2 1050 0.4 1.0 Motor with speed 0.2 revs^-1

Better than case 1, but still mismatching between filaments Case 3 950 0.4 1.0 Manual Viscosity was too

high to extrude Case 4 1000 0.4 1.0 Manual Viscosity was too

high to extrude Case 5 1050 0.4 1.0 Manual Not continuously

extruded while fast moving of heating plate

4.5熱電偶材料測試 Cu-85Cu15Ni、Cu-Cu9Ni6Sn 與 Cu-70Cu30Zn 之熱電動勢在在 650 ˚C 時分別為 23.93 mV、14.05 mV 以及 1.44 mV。電動勢在溫度增加時的提升代表在高溫端被 度，即在溫度變化為 1K 時之熱電動勢變化，可以看到 Cu-85Cu15Ni、Cu-Cu9Ni6Sn 與 Cu-70Cu30Zn 在 650 ˚C 時之席貝克係數分別為 60.93 μVK^-1、35.1 μVK^-1及

3.252 μVK^-1。

4.5.2 熱電偶之長時間裂化

為了解熱電偶在長時間使用下裂化的現象，以及裂化造成的熱電動勢誤差，

將三種熱電偶在 200 ˚C、400 ˚C 及 650 ˚C 持溫 30 h，分別紀錄在 0, 1, 3, 5, 10, 20 及 30 h 時之熱電動勢，藉以了解在不同溫度下長時間使用之熱電動勢變 化與誤差的發生。Fig. 4.44、Fig. 4.45、Fig. 4.46 分別長時間使用下之熱電 動勢值，其中 Fig. 4.44 中 Cu-85Cu15Ni、Cu-Cu9Ni6Sn 與 Cu-70Cu30Zn 之量測誤 差值分別為 1.5%、3.4%及 2.9%，；Fig. 4.45 中 85Cu15Ni、Cu9Ni6Sn 與 Cu-70Cu30Zn 之量測誤差值分別為 3.0%、2.3%與 6.5%；Fig. 4.46 中 Cu-85Cu15Ni、

Cu-Cu9Ni6Sn 與 Cu-70Cu30Zn 之量測誤差值分別為 5.1%、0.45%、8.8%。據文獻 [74, 75]報導，熱電偶在氣氛不變的狀況下，裂化的情形多與晶粒成長、金屬線

為玻璃熱膨脹係數匹配性之考量，以 16.5 ppmK^-1做為參考值，越接近此值時則 匹配性越高，玻璃與金屬之間在長時間使用下熱循環之剝離情形會相對減少。Fig.

4.47、Fig. 4.48 分別顯示三種熱電偶在塗佈氧化物玻璃下以 200 ˚C 與 400 ˚C 持 溫 30h 之熱電動勢。在 200 ˚C 持溫時 Cu-85Cu15Ni、Cu-Cu9Ni6Sn 與 Cu-70Cu30Zn 之量測誤差值分別為 1.4%、1.9%與 6.3%，在 400 ˚C 持溫時 Cu-85Cu15Ni、Cu-Cu9Ni6Sn 與 Cu-70Cu30Zn 之量測誤差值分別為 0.6%、10.6%與 1.2%。

Fig. 4.42 Thermopotential plotted against temperature of three thermocouples.

Fig. 4.43 Seebeck coefficient versus temperature of three thermocouples.

Fig. 4.44 Long term test of thermopotential in 30 h of three thermocouples at 200 ˚C.

Fig. 4.45 Long term test of thermopotential in 30 h of three thermocouples at 400 ˚C.

Fig. 4.46 Long term test of thermopotential in 30 h of three thermocouples at 650 ˚C.

Fig. 4.47 Long term test of thermopotential in 30 h of three thermocouples with TN-SB 5 insulation at 200 ˚C.

Fig. 4.48 Long term test of thermopotential in 30 h of three thermocouples with TN-SB 5 insulation at 400 ˚C.

Table 4.11 Percentage of thermopotential shifting of long term test of three thermocouples at specific temperature

Cu-70Cu30Zn Cu-85Cu15Ni Cu-Cu9Ni6Sn

200 ˚C 2.90% 1.50% 3.40%

400 ˚C 6.50% 3% 2.30%

650 ˚C 8.80% 5.10% 0.45%

第五章 結論

試數種電阻式及電磁感應加熱組合，最後採用電磁感應的方式加熱磁通金屬 導體，可在 90 秒以內加熱 10*10 cm²區域至 670 ˚C。

6. 玻璃擠出中熔料會因表面能作用出現堆積的現象，使擠條直徑變寬，經由減 少擠出噴頭與加熱基板間距離至 0.50 mm，可避免熔料堆積的現象，並可連 續擠出時間超過 300 s，另一例之平均擠出線速度為 25 mms^-1。

7. 量測三種 Cu-85Cu15Ni、Cu-Cu9Ni6Sn 與 Cu-70Cu30Zn 熱電偶於 650 ˚C 以下 之熱電位，最高熱電位分別為 23.93 mV、14.05 mV 以及 1.44 mV，並將熱電 位-溫度圖微分後得席貝克係數，在 650 ˚C 時分別為 60.93 μVK^-1、35.1 μ VK^-1及 3.252 μVK^-1。

8. 利用 TN-SB 5 玻璃鍍膜於三種熱電偶表面，可於 400 ˚C、30 小時之長時間測 試中得到 Cu-85Cu15Ni、Cu-Cu9Ni6Sn 與 Cu-70Cu30Zn 之量測誤差值分別為 0.6%、10.6%與 1.2%，其原因可能為銅晶粒成長，以及接點部分氧化。

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在文檔中 高熱膨脹氧化物玻璃用於熱熔擠出及電絕緣特性之應用研究 (頁 80-0)