Heat trace application on recirculation line

[twr]

We have a silo that we will be using to store syrup. The silo heat transfer was designed for edible oil, so that the agitator is undersized, steam jacket over part of the vessel won't work since the thick syrup won't be agitated, concerned that the jacket will give a hot spot and burn the syrup. We are looking for alternatives, and I am exploring an option to run a heat-traced recirculation line.

The estimated heat loss on the silo, based on product temp of 120º F, insulated tank (3.5" walls, 12' diameter), 12' Nitrogen blanket (24' overall height, estimated 50% full) and 3" top shell (air filled), with ambient temp at 60º F, is ~750 Watts.

Viscosity of the syrup is 7000 cps at 120ºF. It needs to be maintained
Thanks much.

 

[pmover]

ok, please read your posting again and then state your question so people may offer their suggestion. be certain that people are able to understand the system configuration and ultimate requirements.

-pmover

 

[twr]

Let me try this again:
The insulated silo holds a viscous product that needs to be maintained around 110ºF - 120ºF, and not higher than 130ºF. The silo has a small jacket around a quarter of the circumference for steam or hot water. The silo is 12 foot diameter by 24 foot high.
Product is 7000 cps at 120º F. Product comes in at 110º F.

Estimated heat loss out the silo 750 Watts.

What is the best way to keep this product at 120º F?
Would heat trace on a recirculation line work?
Should I use the existing jacket and throttle the steam supply to avoid hot spots?
I hope this makes more sense.

 

[rmw]

Heat trace is generally intended and designed to compensate for heat loss through the pipe insulation. If your heat trace is designed for some low temperature freezing for example and the ambient is 20 degrees above freezing, then in theory the heat given off by the heat trace exceeds the actual losses and the product in the line picks up heat.

That said, often heat tracing is for static lines and in your situation the syrup is flowing (assuming at a velocity above laminar flow) so heat transfer is occurring and the product is picking up heat.

So therefore you would have to do the calculations to determine what your insulation losses to atmosphere at lowest design temperature is and do the heat transfer calculations to see what the heat transfer would be from the heat trace to the pipe at your flow rates and see if you can specify a heat trace with that much heating capacity in it.

Frankly, I have my doubts, but I might still try it if the numbers even looked promising. Remember, however, in order to get a heat trace that operated hot enough to give you enough heat transfer, you might return to a potential scorch problem with your syrup.

rmw