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    ENTC 370-Lab 6-EES The First Law

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    Davorin Ivić
    This document provides instructions and examples for analyzing polytropic processes in thermodynamics laboratory experiments. Students will use measured temperature and pressure data from the expansion of compressed air through valves to calculate specific volume and determine the polytropic exponent n through linear regression. They will also use energy balance equations to analyze the performance of a steam turbine, calculating kinetic energy change, inlet area, and power output as exit pressure varies. Students are asked to document their results and conclusions in an individual lab report.

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    ENTC 370-Lab 6-EES The First Law

    Uploaded by

    Davorin Ivić
    76 views10 pages
    This document provides instructions and examples for analyzing polytropic processes in thermodynamics laboratory experiments. Students will use measured temperature and pressure data from the expansion of compressed air through valves to calculate specific volume and determine the polytropic exponent n through linear regression. They will also use energy balance equations to analyze the performance of a steam turbine, calculating kinetic energy change, inlet area, and power output as exit pressure varies. Students are asked to document their results and conclusions in an individual lab report.

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    This document provides instructions and examples for analyzing polytropic processes in thermodynamics laboratory experiments. Students will use measured temperature and pressure data from the expansion of compressed air through valves to calculate specific volume and determine the polytropic exponent n through linear regression. They will also use energy balance equations to analyze the performance of a steam turbine, calculating kinetic energy change, inlet area, and power output as exit pressure varies. Students are asked to document their results and conclusions in an individual lab report.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    76 views10 pages

    ENTC 370-Lab 6-EES The First Law

    Uploaded by

    Davorin Ivić
    This document provides instructions and examples for analyzing polytropic processes in thermodynamics laboratory experiments. Students will use measured temperature and pressure data from the expansion of compressed air through valves to calculate specific volume and determine the polytropic exponent n through linear regression. They will also use energy balance equations to analyze the performance of a steam turbine, calculating kinetic energy change, inlet area, and power output as exit pressure varies. Students are asked to document their results and conclusions in an individual lab report.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    of 10

    THERMODYNAMICS LAB

    Mass and Energy Analysis of


    Control Volumes
    Polytropic Processes
    ENTC - 370

    ENTC 370

    PROF. ALVARADO

    Polytropic Process(1)
    During expansion and compression processes
    of gases, the following relationship holds:
    PV n C1
    If m is constant, m n is also constant
    Vn
    P n C2
    m
    n
    Pv C2

    Equation_ 1

    For a Process from state 1 to state 2:


    P1v1n P2 v2n

    The coefficient n depends on the process.


    2

    Polytropic Process(2)
    During expansion and compression processes
    of gases, the following relationship holds:
    Taking natural log_ of_ Equation_ 1 :
    ln(P) n ln( v) C
    Y ln(P); X ln( v)
    Y -n X C
    If we measure T and P, we can_ obtain_ v_ from_ Ideal_ gas_ equation :
    PV mRT

    V RT
    RT

    v
    m
    P
    P

    The coefficient n depends on the process.


    3

    Polytropic Process
    The coefficient n depends on the process:
    n=0 , Isobaric process (constant pressure) 5-1 in graph.
    n=, Isometric process (constant volume) 2-6 in graph.
    n=1, Isothermal process (constant temperature) 4-8 in
    graph.
    n=k, Adiabatic process (no heat transfer) 3-7 in the
    graph. k=cp/cv=1.4 for air.

    Graph from www.taftan.com


    ENTC 370

    PROF. ALVARADO

    Polytropic Process
    Boundary work:

    mR (T2 T1 )
    Wb
    1 n
    V2
    Wb PV ln
    V1

    ENTC 370

    PROF. ALVARADO

    n 1
    n=1

    Problem 1: Polytropic Process (Excel)


    Pressurized air inside a pressure vessel is expanded in a polytropic
    process using three discharge valves with small, medium and large
    orifices. The measured temperature and pressure for the process
    are posted.
    1. Use the ideal gas law, Pv = RT, to compute v for each
    corresponding P. Use SI units: m3/kg for v, kPa for P and K for T.
    -

    Conversion factor: 6.894 kPa=1 PSI


    K
    = C+273.15
    R= 0.286 KJ/(kg K) for
    air

    2. Plot ln(P) versus ln(v) and find n:


    a. For each run, on a separate graph, plot ln(P) [on the ordinate
    (vertical) axis] versus ln(v) [on the abscissa (horizontal) axis].
    b. Determine the polytropic exponent n by using a linear model of
    each run. Also find the correlation coefficient R2.
    3. Discuss the meaning of your n values, that is, how do the n values
    compare with n values for other, known processes (see previous
    slide)?
    ENTC 370

    PROF. ALVARADO

    Turbines and Compressors


    Analysis for steady state systems, Energy
    balance:

    For Adiabatic Turbines :


    E E
    in

    out
    2

    v1
    v2

    m (h1
    gz1 ) Wout m (h2
    gz 2 )
    2
    2
    v12 v22
    ke
    2
    ENTC 370

    PROF. ALVARADO

    Problem 2: Steam Turbine (EES)


    Steam flows steadily (8 kg/sec, mass flow
    rate) through an adiabatic turbine. The inlet
    conditions of the steam are 10 MPa, 350 C,
    and 65 m/sec. The exit conditions are 85%
    quality, and 40 m/sec. The exit pressure
    varies from 10 kPa to 200 kPa.
    P1,T1,V1
    Determine:
    -Change in Kinetic Energy (ke)
    -Turbine inlet area
    P2,x2,V2
    -Plot the power output against the outlet
    pressure
    ENTC 370

    PROF. ALVARADO

    Problem 2: Steam Turbine (EES)


    V v A
    m

    where,
    m mass _ flow _ rate
    V Volume _ flow _ rate
    v velocity
    specific _ volume
    A cross _ sec tional _ area
    ENTC 370

    PROF. ALVARADO

    Individual Lab Report


    Introduction: Briefly explain the objectives of the
    assigned tasks
    Data: Present data in tabulated form (use Excel)
    Findings or Results: Include plots (EES and
    Excel) for each data set and the corresponding
    correlation equations and correlation values
    Conclusions: Comment on the tasks performed
    and provide concluding remarks

    ENTC 370

    PROF. ALVARADO

    10

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