ASPEN 学习笔记13 : 流体输送单元 压缩机

ASPEN 学习笔记13 : 流体输送单元 压缩机

流程

image-20220524205635985

规定

规定内容 Compr 计算内容
出口压力 需要的功或对外做的功
需要的功,或者做功(对透平) 出口压力
压头曲线 功率 排出压力 压力比 压力变化或压头系数 需要的功或出口压力
泄压和压头曲线或功率或压头系数 需要的功 排出压力和轴速度
需要的功和排放曲线 压力比或压力变化 排出压力和轴速度

模拟多变压缩机用GPSA或者ASME方法都可以,模拟等熵压缩机可以用GPSA,ASME或者Mollier-based方法

参考如下

image-20220524210305306

基本概念

Variable Description
Compressor model Compressor model used in the block
Phase calculations Phase equilibrium type for flash calculation
Indicated horsepower
指示功
Indicated horsepower (IHP) is the total enthalpy change in the stream, defined as:

    \[IHP = Fdh\]

Where:F=Molar flow rate dh=Enthalpy change per mole
F为摩尔流量, dh 为每摩尔变化

Brake horsepower
功耗
The brake horsepower (BHP) requirement or total work is indicated horsepower (IHP) corrected for mechanical efficiency (Meff) 机械效率

    \[BHP= \frac{IHP}{Meff}\]

Net work required Difference between the sum of inlet work streams and brake horsepower required by the compressor; if there is no user-specified work stream, the net work is the brake horsepower 要求的净功,在没有其他功流的情况下,就是BHP
Efficiency 效率 多变效率 For Polytropic and Positive Displacement compressors: [polytropic efficiency]
等熵效率 For Isentropic compressors: [isentropic efficiency]
Outlet pressure 出口压力 Specified or calculated pressure at the compressor outlet
Outlet temperature 出口温度 Specified or calculated temperature at the compressor outlet
Isentropic outlet temperature 等熵出口温度 Temperature for which the compressor outlet stream (at discharge pressure) has the same entropy as the inlet stream, at suction pressure and temperature
Vapor fraction Molar vapor fraction of the compressor outlet stream
Displacement Displacement (Dis) required for positive displacement compressors is calculated as:

    \[Dis = \frac{V_1F}{Veff}\]

Where
V1=Inlet molar volume
F=Molar flow rate
Veff=Volumetric efficiency

Volumetric Efficiency The volumetric efficiency (Veff) is computed as:

    \[Veff = 1 - 0.01(\frac{P_0}{P_o})+C_f(1-\frac{V_i}{V_o})\]

Where:
Cf=Clearance fraction
Pi, Po=Inlet and outlet pressures
Vi, Vo=Inlet and outlet molar volumes

  • polytropic efficiency

    \[\eta_p = \frac{\frac{k-1}{k}}{\frac{n-1}{n}}\]

相应的压缩焓变为

    \[\Delta h = \frac{P<em>{in}V</em>{in}}{\eta<em>p \frac{n-1}{n}}[(\frac{P</em>{out}}{P_{in}})^\frac{n-1}{n}-1]\]

其中

n = Polytropic coefficient 多变指数
k = Heat capacity ratio Cp/Cv 比热容
η_p = Polytropic efficiency 多变效率
Δh = Enthalpy change per mole 每摩尔焓变
P = Pressure 压力
V = Molar volume 摩尔体积

得到\Delta h 后,进一步得到IHP,和BHP

  • isentropic Efficiency

    \[\eta<em>s = \frac{h^s</em>{out} - h<em>{in}}{h</em>{out} - h_{in}}\]

for compression

    \[\eta<em>s = \frac{h</em>{out} - h<em>{in}}{h^s</em>{out} - h_{in}}\]

for expansion

这里,

h = 摩尔焓值

h_{out}^s 假设压缩和膨胀为等熵过程后的出口焓

  • Power loss

Power Loss = BHP - IHP

  • Specified Speed 比速

        \[SpSpd = \frac{ShSpd (Vfl_{in})^{0.5}}{(Head)^{0.75}}\]

其中 ShSpd 为轴转速

Vfl_{in} 为入口体积流率

Head为 压头

  • Specific Diameter

        \[SpDiam = \frac{ImpDiam (Head)^{0.25}}{Vf_{in}^{0.5}}\]

其中 ImpDiam 为压缩机叶轮直径

Head 压头

Vfl_in 为入口条件下的体积流率

  • Head coefficient 压头系数

        \[Hc=\frac{Head}{(\pi<em> ShSpd </em>ImpDiam)^2}\]

其中 head 为压头

Shspd 为轴承转速

ImpDiam为 压缩机叶轮直径

  • Flow coefficient 流量系数

        \[Fc= \frac{Vfl_{in}}{ShSpd* (ImpDiam)^3}\]

例题5.3

物流的温度 100℃ ,压力 690kPa ,进料组分为31kmol/hr丁烷。现用多变压缩机将该物流压
缩至 3450kPa ,压缩机的多变效率 80% ,驱动机的机械效率 95% 。计算产品物流的温度和
体积流量,压缩机的指示功率、轴功率以及损失的功率。物性方法采用 PENG-ROB 。

  • 组分
    • image-20220525221737632
  • 方法
    • image-20220525221754555
  • 流程
    • image-20220525221808866
  • 流股和Block
    • image-20220525221821410
    • image-20220525221902743
  • Run
    • image-20220525221927945

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