Transformer Radiator Design and Calculations

[Izak_Nel]

Hey guys

I'm BRAND SPANKING new to posting anything an any forum ever...this is a last resort at the end of much research, brainstorming and desperate googling...

My problem:

We've built a transformer tank to house the core and this will be filled with oil, a radiator was built as well - I have to do thermal prediction calculations and am at a complete loss...

I now have to calculate:

At a known flow-rate of forced oil through the radiator, and a known volume of air forced over the radiator - What delta T can be expected between oil entering the radiator and oil leaving the radiator

I can measure/obtain the following parameters:

1. Surface area of radiator fins - individual and cumulative.
2. Thermal conductivity of fin material, air and oil.
3. Specific heat capacity of fin material, air and oil.
4. Ambient temperature of forced air.
5. Flow-rates of both oil and air.
6. kVA Output of the transformer
7. I²R Losses of transformer
8. Desired steady state temperature of oil therefore also the maximum allowable delta-T

Is there a way by using these parameters as well as others needed that I may not have thought of to calculate the Delta-T of oil through the radiator ?

Help would be GREATLY appreciated

Greetings from South Africa

Izak Nel

 

[Windadct]

Hello Izak: Welcome - these are not trivial calculations, in fact most suppliers use simulations exclusively - Also keep in mind a dynamic fluid flow analysis for the internals to ensure there are no unacceptable hot spots on the windings or core.

The manufacturers today have 100 years of designs, experience, knowledge and hard lessons.

The ONLY way I can see getting into this business - is to buy a business with the entrenched knowledge and tools on hand. You may want to seek out a flexible manufacturer or a consultant.

MLT ? ?

 

[AlephZero]

What Windadct said.

Also, it would have been a better idea to do the calcs before you designed the cooling system, not after you already built it.

If you have already built it, why not just test it - and if it starts to overheat, blow more air and/or pump more oil.

 

[Carl Pugh]

AlephZero is correct: If you have already built it, why not just test it - and if it starts to overheat, blow more air and/or pump more oil.

A good book on temperature calculations is
"Cooling of Electronic Equipment" by Allan W. Scott

Two good books on transformers are
"Transformer Engineering" by Blume, Boyajian, Camilli...
"Transformers for the Ellectric Power Industry" by Richard L Bean, Nicholas Chackan Jr...

 

[Izak_Nel]

Hello Izak: Welcome - these are not trivial calculations, in fact most suppliers use simulations exclusively - Also keep in mind a dynamic fluid flow analysis for the internals to ensure there are no unacceptable hot spots on the windings or core.

The manufacturers today have 100 years of designs, experience, knowledge and hard lessons.

The ONLY way I can see getting into this business - is to buy a business with the entrenched knowledge and tools on hand. You may want to seek out a flexible manufacturer or a consultant.

MLT ? ?

I had that feeling sir, was just quietly hoping that i was young, inexperienced and a bit thick and somewhere in all these parameters there must be a reasonably-simplified empirical equation to obtain a ball-park "gut-feel" figure you know ?

 

[Izak_Nel]

What Windadct said.

Also, it would have been a better idea to do the calcs before you designed the cooling system, not after you already built it.

If you have already built it, why not just test it - and if it starts to overheat, blow more air and/or pump more oil.

I would have loved to have done calculations before building sir, but i was in the same boat then as i am now - lack of theory, knowledge and experience to calculate anything substantial.

So what I did was:
1. Asses my transformer capacity - 50kVA @ 5773.5A & 5V
2. Evaluate similar transformers with ONAN cooling
3. Copy this design in terms of similar radiator surface areas
4. Re-format configuration from ONAN to OFAF

 

[Izak_Nel]

AlephZero is correct: If you have already built it, why not just test it - and if it starts to overheat, blow more air and/or pump more oil.

A good book on temperature calculations is
"Cooling of Electronic Equipment" by Allan W. Scott

Two good books on transformers are
"Transformer Engineering" by Blume, Boyajian, Camilli...
"Transformers for the Ellectric Power Industry" by Richard L Bean, Nicholas Chackan Jr...

I will go read up on those books sir, gaining as much knowledge as possible on as many topics and subjects as possible is what makes me grow as a junior technician.