<body><script type="text/javascript"> function setAttributeOnload(object, attribute, val) { if(window.addEventListener) { window.addEventListener('load', function(){ object[attribute] = val; }, false); } else { window.attachEvent('onload', function(){ object[attribute] = val; }); } } </script> <div id="navbar-iframe-container"></div> <script type="text/javascript" src="https://apis.google.com/js/plusone.js"></script> <script type="text/javascript"> gapi.load("gapi.iframes:gapi.iframes.style.bubble", function() { if (gapi.iframes && gapi.iframes.getContext) { gapi.iframes.getContext().openChild({ url: 'https://www.blogger.com/navbar.g?targetBlogID\x3d8968604820003269863\x26blogName\x3dChemical+%26+Process+Technology\x26publishMode\x3dPUBLISH_MODE_BLOGSPOT\x26navbarType\x3dBLUE\x26layoutType\x3dCLASSIC\x26searchRoot\x3dhttp://webwormcpt.blogspot.com/search\x26blogLocale\x3den\x26v\x3d2\x26homepageUrl\x3dhttp://webwormcpt.blogspot.com/\x26vt\x3d6402931565399164945', where: document.getElementById("navbar-iframe-container"), id: "navbar-iframe" }); } }); </script>

Chemical Process Technology

Continue to learn tips, knowledge and experience about Chemical Process Technology...

Enter your email address:



Chemical & Process Technology

A place to share knowledge, lesson learnt...

Wednesday, August 6, 2008

Display problem ? Click HERE

Recommended :
Subscribe FREE - Chemical Processing

There was a question raised in CR4 forum related to conversion from Nm3/h to m3/h and the equation can be known by many of you. Nevertheless, the derivation and relation in between ideal gas and real gas and the derived equation could be useful and handy for some of you.

First for most important thing is the definition of Normal and actual condition. Normal condition in this case is define as 1 ATM @ 0 degC whilst actual is at P @ T.

From Universal gas law for ideal gas,

PV = (m/MW) RT [Eq.1]

P = the absolute pressure of the gas, in Pa
m = mass, in kg
MW = molecular weight, in kg-mole
V = the volume of the gas, in m3
T = the absolute temperature of the gas, in K
R = the universal gas law constant of 8.3145 m3·Pa/(mol·K)

To relate it to real gas condition, compressibility factor (z) is added.

PV = z (m/MW) RT. [Eq.2]

At condition 1 ==> P1 x V1 = z1 (m1 / MW1) R x T1 [Eq.3]
At condition 2 ==> P2 x V2 = z2 (m2 / MW2) R x T12 [Eq.4]

Same gas composition and flow or quantity
==> MW1=MW2, m1=m2,

[Eq.4] / [Eq.3]
==> (P2/P1) x (V2/V1) = (z2/z1) x (T2/T1)
==> V2 = (z2/z1) x (T2/T1) x (P1/P2) x V1

Using Volumetric rate (Q),
==> Q2 = (z2/z1) x (T2/T1) x (P1/P2) x Q1

If condition 2 is actual (act) and condition 1 is normal(N) (i.e. 1.01325 bar abs @ 0 degC)

At Normal condition Z1=Zn~1, P1 = 1.01325 bar abs

Qact = zact x QN x (Tact / 273.15) x (1.01325 / Pact)

Qact in m3/h
Pact in bar abs
QN in Nm3/h
Tact in K

Above equation with inclusion of compressibility factor to relate ideal to real gas condition,The zact factor could be range from 0.5 to 1.2 subject to composition, pressure and temperature. At low pressure, z could be closed to 1.

The relationship between ideal and real can be more complicated as derived in by Van der Waals, Redlick-Kwong, Peng-Robinson, etc.

Above equation could be useful and handy for general purpose.

Related Post


posted by Webworm, 11:46 PM


Post a Comment

Let us know your opinion !!! You can use some HTML tags, such as  <b>, <i>, <a>

Subscribe to Post Comments [Atom]

Links to this post:

Create a Link


<< Home