8 replies to this topic

[haseeb00718]

I am working on the design of a solvent purification system under vacuum. The system comprises of ethyl alcohol solvent to be purified. I have attached the link to the excel sheet with the key dimensions & physical properties. I am struggling to determine the oil circuit temperature requirements, number of passes needed etc., 

 

Internally, the vessel has an agitator though it is just used to scrap the surface and doesn't contribute significantly to go to the forced convection side. In that case, i have assumed natural convection. However, i cannot understand well from literature how to account for the internal heat transfer coefficient. 

 

Externally, the oil is moving in the channels. The length, velocity, number of passes etc., have to be developed by us. Considering that i have to account for both sensible heat and heat of vaporization overall, i don't understand well how to account for that. 

 

Can someone please recommend a proper pathway to approach the problem ? any specific literature to support that or similar examples will help. According to my research so far, i didn't find anything specifically applicable to my case. 

 

waiting for your comments.

 

[breizh]

Hi,
No link.
Breizh

[haseeb00718]

Hi,
No link.
Breizh

https://docs.google....of=true&sd=true

[breizh]

A drawing will help.

Breizh 

[haseeb00718]

A drawing will help.

Breizh 

https://drive.google...iew?usp=sharing

More detail about the unit. It's a evaporating unit. The channel will have a thermal oil passing through while the solvent will be heated first to it's boiling point. Afterwards, the solvent will be evaporated. the aim is to determine the geometry of the channels, velocity, temperature inlet required to meet the duty. I have considered the following assumptions so far:

- steady state.
- No Fouling. 
- No heat loss against environment (there is an insulation layer supporting our argument). 
- Impeller is non-standard and rotates at appx. 8 RPM. Thus, we can say that it's simply used to scrap the solids from the surfaces and not for heat transfer improvemnet. Infact, the shape is non-standard and not designed for enhancing heat transfer.
- The jacket is considered in the form of rectangular geometry. 
Forced convection in the jacket (missing the correlations to obtain the heat transfer coefficient) 

Overall, i am in the process of establishing a proper methodology to determine the heat transfer coefficients ensuring  rather accurate scenario. As boiling is involved, i am not sure how to proceed and what type of correlations can support. 


Thank you for your time and support.  

[breizh]

Hi,

Let you consider the documents attached to support your work.

Good luck

Breizh

Attached Files

•  overall heat transfer coefficient jacketed vessel.pdf   639.27KB   227 downloads
•  evaporation of difficult products.pdf   2.5MB   159 downloads
•  agitated film evaporator.pdf   1.55MB   622 downloads

[haseeb00718]

Hi, 

 

Thank you for the material. i was able to execute most of the calculations but only part left is nucleate boiling correlation to determine the heat transfer coefficient. However, my case is unique. i..e, we have a boiling liquid inside a tank. Liquid can be ethyl acetate or other industrial solvents used in printing industry. Tank is made up of SS316. 

 

I used Rohsenow correlation but that is highly dependent on the surfaces involved and literature has some constant values only for specific cases. 

 

Can you provide a correlation that can be considered usable in the current scenario? 

 

Thanks,

Haseeb Ali 

[breizh]

Hi,

Consider this resource.

Note : It seems this is an existing vessel, you should be able to find out the calculation note attached to this design. 

Good luck,

Breizh 

Attached Files

•  wolverine boiling heat transfer on external surfaces.pdf   15.42MB   168 downloads

[breizh]

Hi,

Consider this resource for jacketed vessels.

Breizh

Attached Files

•  heat transfer coefficient in agitated vessel.pdf   792.67KB   570 downloads