Simultaneous Heat & Mass Transfer rate

[sharjeel]

Can any body guide me to a correlation that enables me to calculate simultaneous heat and mass transfer rate between steam and condensate, where condensate is in sub-cooled phase and steam is in superheated phase.

[Ali]

Is this possible? There is always an equilibrium line (the saturated one). The condensate first of all goes from sub-cooled liquid to the saturated liquid sate, then, it will pass through a "phase change" process from partially liquid to complete vapor state (saturated vapor state). After that, the super heated state happens.
Would you like to explain your system further to understand what is the exact question.

[ibrahim]

sharjeel, will you please explain the process further. Ali is right, in any case the super heated steam have to move thru saturation dome, if both medium are in direct contact.

[sharjeel]

Yes dear forum members, you are right that superheated steam has to get saturated first and then it will be condensed. This is exactly my question. That how much time would it take to a superheated steam to get condensed when it is brought into contact with a sub-cooled liquid. For example I want to heat a stream of sub-cooled water(water below its saturation temperature) by mixing a stream of superheated steam to bring the sub-cooled liquid to its saturation temperature (the opposite of steam desuperheating process where injected water is converted to steam, here desuperheated steam should convert to condensate). Now my question was
1. Is there any relation that can predict the time taken for such heat and mass transfer? This will help me to provide sufficient length of pipe to get these streams mixed properly. I am planning to use a converging nozzle to inject superheated steam in a pipe of sub-cooled water.
2. is it better to use steam sparger in a tank of subcooled water? Or the scheme that I have in my mind & mentioned above. Please share your experience.
3. What are the chances of water hammering in case we inject superheated steam at a high velocity (say at 52 m/s) in a liquid steam flowing at 1m/s?
4. What are the chances of water hammering in case we inject the same superheated steam in a tank full of same sub-cooled liquid?

Regards,
Sharjeel

[Ali]

So, you wanna heat water by direct steam injection. I could suggest you an atricle on the subject in "Chemical Engineering Progress" May 2010 with the title "Producing Hot Water by Direct Steam Injection" by Sutter, Philip.
I am afraid I don't have this one; otherwise, i will attach it for you. This article has commented on pros and cons of different available Direct Steam Injection ways including the sparger as well. I hope it will give you a fair idea of proceeding in right direction.

[ibrahim]

check the attachment, its a good literature upon "direct steam injection heating".

[sharjeel]

Thanks Ibrahim, the article was really very useful.