3 replies to this topic

[ramnathsharma]

Dear Friends / Colleagues,

We have purchased a old thermic fluid system .

We dont have a manual .

My question is HOW TO CALCULATE THE HEAT DUTY OF THERMIC FLUID HEATER ie., BACK CALCULATIONS ???

Any suggestions / ideas pls.

Thanks & Regards

Ramnathsharma

[ankur2061]

Ramnath,

There is no easy way to do this. However, if it is a package item it will have a model number and manufacturer nameplate. You can contact the package vendor who supplied this and ask all the relevant details, albeit with some monetary considerations.

Another way is that if you know the mass flow circulation rate through the heater and the supply and return temperatures for the heater it is simply a heat load calculation based on

Q = m* Cp*(T2-T1)

Q = heat load, kcal/h

Cp = Sp. heat @ Avg. temperature

T2 = supply temperature

T1 = return temperature

The difficult part is to calculate the mass flow rate and return temperatures. But suppose if you have the individual mass flow circulation of all the heat consumers (exchangers, jacketed/coiled reactors) you can just add it up to get the mass flow rate.

You can also do a heat balance for individual consumers and arrive at the return temperatures from each heat transfer equipment. Then use the individual return temperatures from each equipment to find the average temperature of the combined return flow. Also consider a heat loss from the entire system and arrive at some sub-cooled return temperature and thus be able to estimate the heat balance for your process plant.

The above mentioned exercise, i.e. a heat balance for your process plant would enable you to calculate the heater duty.

Hope this helps.

Regards,
Ankur.

[Art Montemayor]

Ram:

You have a difficult and risky problem when you purchase used, engineered equipment without the necessary and required detailed calculations or full specifications on the unit and its installation. In my professional opinion, you should not try to employ this used heater without full identification from the manufacturer - perhaps even obtaining the manufacturer's help and engineering service to check and assist in its installation and future use.

You are taking full technical responsibility for the ultimate results of using this piece of equipment in the future and will have to answer should an accident or hazardous situation develop because of its use. You don't have the detailed calculations nor do you know how the type of burner, blower, instrumentation or heating surface was designed as to allowable temperature and pressures. And I haven't even gone into the metallurgy yet.

Any unqualified or uncertified calculations made on this unit will, in my opinion, be deemed worthless and of no use. You simply know little or nothing about the unit and certainly are not a recognized designer or fabricator of these units. Any engineer doing what you are attempting to do has to take on full responsibility of the consequences and I would advise against doing that.

[kuldeepd]

http://www.processca..._Exchanger.aspx

hope this helps.

regards
KD