# Transformer Radiator Design and Calculations

• Izak_Nel
In summary, Izak is a new user of posting on forums and is having difficulty calculating the delta-T of oil through a radiator. He would appreciate any advice on how to do this.
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

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 ? ?

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...

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:

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
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.

## 1. What is the purpose of a transformer radiator?

A transformer radiator is used to dissipate heat generated by the transformer to prevent overheating and damage to the transformer. It helps to maintain the transformer's optimal operating temperature.

## 2. How is the size of a transformer radiator determined?

The size of a transformer radiator is determined by the transformer's power rating and the required heat dissipation rate. A larger transformer or one that operates at a higher power will require a larger radiator to effectively dissipate heat.

## 3. What factors affect the design of a transformer radiator?

The design of a transformer radiator is affected by various factors such as the transformer's power rating, ambient temperature, cooling medium, and the required heat dissipation rate. The type and size of the transformer also play a role in the design.

## 4. How is the cooling capacity of a transformer radiator calculated?

The cooling capacity of a transformer radiator is calculated using the heat dissipation rate and the thermal resistance of the radiator. The thermal resistance is determined by the material and design of the radiator, and the heat dissipation rate is based on the transformer's power rating and operating conditions.

## 5. What are the different types of transformer radiators?

The most common types of transformer radiators are air-cooled, oil-cooled, and forced oil-cooled radiators. Other types include water-cooled and fan-cooled radiators. The type of radiator used depends on the transformer's design and operating conditions.

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