# Time Dependent Gas Release Through A Hole From A Pressurized Container

Dear All,

One of the very important books related to process safety is popularly known as the "Yellow Book" published from the Netherlands and having the full title as:

"Methods for the calculation of physical effects - due to releases of hazardous materials (liquids and gases)" - 'Yellow Book' - CPR14E

The best part of this book is that it is absolutely free to download from the internet. The units used in the book are purely SI units which might prove somewhat of a dampener fro those quite used to engineering units and English units. In its treatment of the physical phenomena of gaseous and liquid releases it is an absolute delight to read. The coverage is extensive and wherever possible numerical methods to enunciate the physics involved in releases is provided.

It also encompasses other safety related topics such as vapor cloud dispersion, vapor cloud explosion, heat flux from fires etc.

http://content.publi...cal-effects.pdf

The title of my blog entry does not suggest anything about the book but I wanted to make it clear that the topic I have chosen  i.e. 'Time Dependent Gas Release through a hole from a pressurized container' is basically picked up from the 'Yellow Book'.

I have prepared a spreadsheet based on the theory and equations provided in the 'Yellow Book' for the subject with an example. A few relevant pages of the 'Yellow Book' with certain sections highlighted have also been provided in the spreadsheet.

Those process engineers who have access to HYSYS or any other similar process simulation software where vessel depressurization dynamic utility is available, may find that  the results are not closely matching with the spreadsheet that has been presented along with this blog entry. The reason is that a few simplified assumptions have been done which the book also follows to arrive at the results. Some of these are as follows:
1. The process of the vessel depressurization is considered to be an adiabatic process only.
2. The specific heat or heat capacity at constant volume (Cv) is considered to be constant along the depressurization path although the dynamic change in pressure and temperature during the depressurization will have some effect on the specific heat value. In other words, there will be minor changes in the specific heat value at different dynamic values of pressure and temperature.
3. The specific heat ratio (Cp/Cv) is also considered to be constant along the depressurization path based on the same premise presented above in point number 2.

Again the idea of presenting a spreadsheet is to ensure that those process engineers who do not have access to expensive simulation software are not left out.

Hope all of you enjoy this blog post and the accompanying spreadsheet. I look forward to your comments and definitely look forward to comparisons of the example given in the spreadsheet with the results obtained form a "Dynamic Depressuring Utility" from a simulation software such as HYSYS or similar.

Regards,
Ankur.

http://www.cheresour...through-a-hole/

breizh

thanks for Sharing ,

Breizh

Sharma Varun

thanks for one more chapter in your vast endeavour of knowledge sharing

nahmed

dear Ankur sir,

thanks for sharing this sheet.

is this applicable for liquid also ? in that case Cd (coeff of discharge ) is still between .595 to 0.8 depend uopn type of taps. what will value of Cv then can we consider 1. Critcal flow (chocked flow) is not dependednt on hole size ?

ankur2061

dear Ankur sir,

thanks for sharing this sheet.

is this applicable for liquid also ? in that case Cd (coeff of discharge ) is still between .595 to 0.8 depend uopn type of taps. what will value of Cv then can we consider 1. Critcal flow (chocked flow) is not dependednt on hole size ?

nahmed,

It certainly is not applicable to liquids. I have already posted a spreadsheet for liquid drain due to gravity from cylinders (horizontal / vertical with flat ends) at the following link:

http://www.cheresour...ime-calculator/

Regards,

Ankur.

nahmed

thank you sir ji,

do you have any information about  spreadesheet used for pressureized vessel containing liquid.

ankur2061

thank you sir ji,

do you have any information about  spreadesheet used for pressureized vessel containing liquid.

nahmed

thank you

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