6 replies to this topic

[karthick selvaraj]

Hi All,
I am designing kettle reboilers for Delayed coking unit asper the customer requirement. Shell side fluid is water to be vaporised and tube side is HCGO. Since I am designing for first time I am having some doubts.
I tried to search for previous forums on kettle type heat exchanger deisgn but unfortunately there is some problem in searching because I can able to view the first page alone search results beyond that I cannot able to view.

So i am posting the below queries in point widse even if lots of discussoin are made on the same.

1) As the bundle has to be immersed fully in the fluid for pool boiling, what shall be the difference between the liquid level and top most tube row. Say for example, if my OTL value is 1000mm what shall be my liquid level above outer most tube row.

2) How to fix my kettle diameter?. For example if my shell diameter(port dia) is 1200mm what shall be kettle diameter.

3) The weir height which is used in the kettle diameter shall be equal to the liquid level maintained or shall be greater than that. If yes what shall be the value? Is there any thumbrule or its individauls responsibility.

4) As the bundle has to be immersed fully in the fluid for pool boiling as known. In my case,water flow rate is 2000 kg/hr with such a small flow rate of fluid is it possible to immerse the bundle fully in the water?Is there any recommendation for minimum flow rate to be used in kettle rebioler type.

5) As the kettle type is used mainly for the vapor disengagment. Is there any value to be considered as minimum for disengagement. If yes, please let me know how to calculate that value.

6) Similarly as above is there any minimum value to be considered for the 'entrainment ratio' value. Also is there any standard method for calcualting the entrainmment ratio.Also please let me know the exact definition of entrainment ratio.

7) Whether the fixing of the shell length beyond weir is based on the volume of fluid pupmed from the weir portion or some other parameter. Is there any general recommendation for maintaining the liquid level or it has to be maintained in such a way that fluid beyond weir doesn't mix with the fluid in the tube bundle portion. ,

Apart from above is there any other parameter to be considred for fixing the deisgn except the general considerations such as overdesign, pressure drop, velocity (min and max),vibration.

Thanks
Karthick.S

[Atul jain]

For your first point, normally 50 MM is kept above the upper most tube row.
For kettle dia calculation, first you have to calculate entrainment ratio. Based on entrainment ratio of 0.01 (normally or less) kg liquid/kg vapor considered.

[breizh]

you may find answers to your query using the search button top right of the page , key words Kettle reboiler .

Breizh

[Atul jain]

As reule of thumb, kettle dia 1.6 times of port dia is kept.

[karthick selvaraj]

Hi Atul,
Can you please be more specific on your explanation below. Being new to kettle reboiler design I couldn't make out explanation given below by you.

For kettle dia calculation, first you have to calculate entrainment ratio. Based on entrainment ratio of 0.01 (normally or less) kg liquid/kg vapor considered.

Thanks
Karthick.S

[srfish]

Use www.gulleyassociates.com, click on engineering tips and look in the boiling section for help. This same information can also be found in the Excel download of "Process Heat Transfer" by Art Montemayer.

A very good literature source is "Process Heat Transfer" by Serth. It has a reboiler section with a subsection for kettle reboilers. There is an example for calculating the shell diameter and an example for designing the complete reboiler.

[mkarahan]

• For this diameter minimum liquid level should be minimum 60 mm. But it is also depends your level control system. on-off or propoertional
• Diameter depends your vapor volume and required free space according to design code. Vapor volume depends pressure so density.