世鵬 asked in 科學化學 · 1 decade ago

單操題目 單效蒸發器

請專家幫我解答 {急}!!

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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  • 1 decade ago
    Favorite 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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