Transformer Radiator Design and Calculations

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Discussion Overview

The discussion revolves around the thermal prediction calculations for a transformer radiator design. Participants explore the parameters necessary for calculating the expected temperature difference (delta T) between oil entering and leaving the radiator, considering factors such as flow rates, thermal properties, and desired operating conditions.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Izak Nel outlines the parameters he can measure and seeks guidance on calculating the delta T of oil through the radiator.
  • Some participants suggest that these calculations are complex and often rely on simulations rather than manual calculations.
  • There is a suggestion that testing the system after construction may be a practical approach if overheating occurs, rather than relying solely on calculations.
  • Participants emphasize the importance of prior calculations and theoretical knowledge before designing the cooling system.
  • Izak shares his approach of assessing transformer capacity and evaluating similar designs to inform his radiator configuration.
  • Several participants recommend books on temperature calculations and transformer engineering as resources for Izak to enhance his understanding.

Areas of Agreement / Disagreement

Participants generally agree that the calculations are non-trivial and that testing the system may be a viable option. However, there is no consensus on the best approach to take, with some emphasizing the need for theoretical calculations and others suggesting practical testing.

Contextual Notes

Participants note the complexity of the calculations and the potential for dynamic fluid flow analysis to identify hot spots, indicating that there may be additional considerations not fully addressed in the discussion.

Who May Find This Useful

This discussion may be useful for engineers, technicians, and students involved in transformer design, thermal management, and fluid dynamics, particularly those seeking practical insights into cooling system design and thermal calculations.

Izak_Nel
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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
 
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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 ? ?
 
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.
 
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...
 
Windadct said:
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 ?
 
AlephZero said:
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
 
Carl Pugh said:
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.
 

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