Jim Grant Forum Moderator 119 Posts
Re: What would be the best formula to calculate heat transfer from glycol to beer?22 March 2011 at 1:29pm
The overall heat transfer coefficient must be calculated as a sum of resistances of the inside, outside and wall conduction terms for heat transfer.
The inside heat transfer coefficient may be determined by using correlations for bubble columns if there is sufficient gas generation in the vessel. Alternatively one could use a natural convection coefficient calculation based on the difference between bulk and surface temperatures.
The jacket side coefficient correlations will vary depending on the style of jacket used (dimple, annular, baffled annular) and guidance can be found in "Process Heat Transfer," (1994) written by G. L. Shires , T. Reg Bott G. F. Hewitt or references within. Dimple jacket correlations have been published in "Chemical Engineering Progress" (August 2001 - J. Garvin) and include both heat transfer and pressure drop assuming that the exact geometry of the dimples are known.
The calculation you wish to undertake is a transient one and must be described as a differential equation which, with a few simplifying assumptions (constant area, constant coolant temperature) can be analytically integrated and solved for the heatup/cooldown times for any vessel. Be sure to include the thermal mass of the vessel in the calculations and be aware that the wall conduction may be a significant portion of the overall heat transfer resistance.