Recent content by cjc0117

  1. C

    Error Propagation in Mass Flow Rates

    I tried posting this question in this forum a couple of weeks ago, but didn't get an answer to my question. I'm going to try posting it again using the formatting template so that it is hopefully clearer. I am also not sure if this is the right forum to be posting this in. It is a problem I ran...
  2. C

    Error Propagation - Reconciling Two Approaches

    Thanks for the reply, and for the compliment! It was certainly painful to type all of it out...Also, no, there are ##N## streams and ##N## separate containers with which to collect liquid from each stream. So for each stream ##i##, the mass of liquid, ##m_{i}##, is calculated by subtracting the...
  3. C

    Error Propagation - Reconciling Two Approaches

    Just want to rewrite all my work using LaTeX and clarify a few things... Objective: Show that if \sum^n_{i=1}\dot{m}_i=\frac{\sum^n_{i=1}m_{i}}{t} then \delta{\left(\sum^n_{i=1}\dot{m}_{i}\right)}=\delta{\left(\frac{\sum^n_{i=1}m_{i}}{t}\right)} Define: M_{1,i}\ \mbox{and}\ M_{2,i}\ \mbox{are...
  4. C

    Error Propagation - Reconciling Two Approaches

    I have calculated the mass, ##m_{i}##, of liquid exiting the outlet of stream ##i## for ##n## number of streams over a measured time period of ##t##, by measuring the mass of liquid + container, ##M_{1,i}##, and subtracting from that the measurement for the mass of the container, ##M_{2,i}##...
  5. C

    Error Propagation - Reconciling Two Approaches

    Hi, I am trying to find the error propagated by calculating the sum of a set of mass flow rates collected over the same length of time. The sum of mass flow rates can be calculated with two approaches, since the collection time is the same for all of them. Approach (1) is adding up all of the...
  6. C

    How Do You Solve a Differential Equation Using the Frobenius Method?

    Thanks for the replies. I had found the two s values to be s_{1}=3 and s_{2}=0. s_{1}-s_{2} is equal to a positive integer. I thought in this case, there are two independent solutions: y_{1}=\sum^{∞}_{m=0}a_{m}x^{m+s_{1}}(Eqn. 1) y_{2}=ky_{1}ln(x)+\sum^{∞}_{m=0}b_{m}x^{m+s_{2}} (Eqn. 2) I...
  7. C

    How Do You Solve a Differential Equation Using the Frobenius Method?

    Homework Statement Solve x(1-x)\frac{d^{2}y}{dx^{2}}-2\frac{dy}{dx}+2y=0 using the Frobenius Method. Homework Equations R(x)\frac{d^{2}y}{dx^{2}}+\frac{1}{x}P(x)\frac{dy}{dx}+\frac{1}{x^{2}}V(x)y=0 R_{0}s(s-1)+P_{0}s+V_{0}=0 y=\sum^{∞}_{m=0}a_{m}x^{m+s}...
  8. C

    Calculating equivalent length of expansion/contraction from K value

    If you know the resistance coefficient, K, for a sudden expansion or contraction in a pipe, how can you calculate the equivalent length, Le from the K value? I know that for fittings, Le=KD/f, where D is the diameter and f is the Darcy friction factor. But when considering a contraction or...
  9. C

    Ideal Gas Heat Capacity Regression Coefficients

    I'm trying to find a comprehensive list of the empirical coefficients to be used in the following equation for calculating ideal gas constant pressure heat capacities: \frac{c^{IG}_P}{R}=A+BT+CT^{2}+DT^{-2}+ET^{3}(Eqn. 1) cPIG is the ideal gas constant pressure specific heat capacity; R is...
  10. C

    Deriving Peng-Robinson Entropy Departure Function

    EDIT: Nevermind. I figured it out. The two expressions are, in fact, equal. An excerpt from a book at this link, http://webpages.sdsmt.edu/~ddixon/Departure_Fxns.pdf, states that the entropy departure function for any equation of state is equal to the following (Eqn. 4.4-28)...
  11. C

    Can the Peng-Robinson EOS be solved explicitly for T?

    Okay, I figured it out. Thank you gneill!
  12. C

    Can the Peng-Robinson EOS be solved explicitly for T?

    I'm not sure if this is the right forum to ask this question, but it arose as part of an engineering problem, so here goes. The Peng-Robinson EOS is as follows: P=\frac{RT}{v-b}-\frac{a[1+k(1-\sqrt{\frac{T}{T_{c}}}]^{2}}{v(v+b)+b(v-b)} I'm just wondering if this equation can be solved...
  13. C

    Understanding Gibbs' Phase Rule Basics

    Thanks for the reply David. You're right; my post wasn't really structured well. Just a mess of questions. Anyways, I originally asked these questions because I was trying to solve a bigger problem that required me to get two-phase properties for a single component system. I was hoping against...
  14. C

    Understanding Gibbs' Phase Rule Basics

    I am having some trouble fully understanding the basics and I just wanted to see if somebody would please clarify this for me. First, say you have a one component system in two phases: vapor and liquid. Gibbs' phase rule restricts the system to one independent, intensive variable that may be...
  15. C

    Calculating Enthelpy of Vaporization using Clapeyron Equation

    Perfect, that's exactly what I did wrong. I left the Tsat in the denominator in °C because the Antoine coefficients are for temperatures in °C, but I converted the other Tsat to Kelvin and now I'm getting 136.6 BTU/lb. Thanks a lot. It didn't make sense to me at first that I should convert to...
Back
Top