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# 單操題目 單效蒸發器

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題目:

有一單效(Single-effect)蒸發器被用來濃縮氫氧化鈉水溶液，使其濃度由

10wt%變為50wt%，進料之質量流率為4796 Kg/h，進料溫度為313K，蒸氣

空間之壓力為49 kpa，用以加熱的飽和水蒸汽之壓力為125 kpa，假設總熱傳係數U=4257 W／m2k，試計算此爭發器所需之加熱面積及水蒸汽的經濟價值

。

麻煩了!!

### 1 Answer

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- ＤＤ博士Lv 51 decade agoFavorite Answer
mass balance

F = L + V

F*x(F) = L*x(L)

-->

4796 = L + V

4796*0.1 = L*0.5

-->

可得L = 959.2 , V = 3836.8

heat balance

S*λ1 = F*Cp*(Tb-Tf) + V*λ2

-->

S * 2306 = 4796 * 4.14 *( 354 - 313 ) + 3836.8 * 2240

-->

可得S = 4080

∵Q = S*λ1 = UA(Ta -Tf )

-->

4080 * 2306 = 4257 *A *( 380 - 313)

-->

可得A = 33 (m^2) ......加熱面積

經濟價值 = V/S = 3836.8 / 4080 = 0.94

where,

F: feed

L: concentrated liquid

V: concentrated vapor

λ1, λ2: leatent heat of steam(題目沒給自己查蒸氣表資料)

Ta: 蒸發器內溫度

Tb: 飽和蒸汽溫度(這兩個溫度也要查蒸氣表,可以由題目所給的壓力)

Source(s): 化工人

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