Heat Exchanger for Toluene not Performing

How long did you let it run, are the readings static? Improving? getting worse? Maybe it just needs to run for a while to sort itself out...

http://www.dekkervacuum.com/static4/operation.asp

I let it run twice for half an hour.

The situation improved in the first ten minutes and then it started getting worse with time. we are not able to understand why it is reducing first and then increasing.

Sometimes it reduces to -1 degree celsius from 31 degree celsius and sometimes to 21 degree celsius from 29 degree celsius. the trend of heat increase or decrease is not similar.

the only heat input is pump discharge. By the way its Nash Pump.

Can water or any other additive in the toluene might make it behave differently in the heat exchanger.

If the toluene is undergoing evaporation, its temperature does not change as it absorbs heat. (I haven't looked anything up to see if this pertains to your situation.)

Is it "water" or "brine" that you find traces of in the toluene? Sounds like you have a leak in the heat exchanger between your fluids.

hi.. no there is no leak in the heat exchanger. The process of toluene collection in the plant involves distillation and water is separated from it. water was present from the start.

The amount of miscibility of water in toluene is as less as 0.05 percent.

So the water is present as part of the process? Is your separator operating properly?

The separator is designed as a collection tank of the vacuum pump where the heated liquid will go and it will again come back to the pump through the heat exchanger.

The height of the process is that , the heat exchanger first cools and then heat up the toluene.

Sometimes it cools upto -1 degree and some times to 21 drgree before taking its trend to heat up again.

What is bringing down the heat exchanging capacity of the heat exchanger. This is my question.

Just offhand I would say check the toluene quantity, it sounds like it is low level...

Trace water in the toluene is of no consequence to the the problem at hand. At 80 millibar water will flash off solution and dissipate on the feed tank overhead space.

Problem gotta be on the coolant loop.

I have to agree with Mikerho that a diagram would be helpful in attempting to analyze the situation.

Excuse my confusion, but based on your description:

"...pump is initially half filled,heat exchanger is completely filled, and tank is half filled with toluene which will be recirculated by pressure difference."

and

"...pump starts creating vacuum, toluene is recirculated to tank and to heat exchanger which comes to pump again..."

it appears that you are describing a closed system that does nothing but circulate and cool toluene, and I highly doubt that a company would waste engineering talent on this.

The diagram showing any other equipment connected to the loop you describe may provide that "quantum leap" noted by Mikerho. Please also indicate any joints or connections, as they may be contributing to the lack of performance.

Working for http://domyhomeworkonline.net/do-my-chemistry-homework.php I learned that the heat isn't prevented from escaping and may actually move faster (narrowing the flow increases velocity) through the channeled areas, but the increase in surface with channels exposed to heat makes net heat collection more efficient. In reality any surface increasing would accomplish the same and perhaps other shapes - that slow or temporarily trap the heat may be even more efficient.