How to design a radiator to dissipate heat generated by a 39 KW rotary engine?

[Somanna]

No separate coolant is used, instead lubricating oil to be used for both lubrication and cooling of engine. How to calculate radiator size, coolant flow rate?

 

[Nugatory]

Roughly how efficient is your engine? That will tell you how much waste heat will have to be dissipated by the radiator per unit time. Why are you designing a radiator instead of using an off-the-shelf component?

 

[jack action]

Very complicated task. As a first approximation, for every kW you produce, you will lose another kW through cooling and another one through heat exhaust. Knowing that, you can use these equations to size your radiator and flow rates. The hardest part is to determine the overall heat transfer coefficient. Here are some references:

• http://www.engineeringtoolbox.com/overall-heat-transfer-coefficient-d_434.html
• http://www.maplesoft.com/applications/view.aspx?SID=6403&view=html
• http://fr.scribd.com/doc/35669547/Heat-Transfer-in-Radiators
• https://en.wikipedia.org/wiki/Heat_transfer_coefficient
• http://www.energy.kth.se/%5Ccourses%5C4A1607%5Cfiles%5CSEU-LAB4.pdf

 

[Somanna]

Roughly how efficient is your engine? That will tell you how much waste heat will have to be dissipated by the radiator per unit time. Why are you designing a radiator instead of using an off-the-shelf component?

Efficiency of the engine is calculated as 90% and BSFC is 300 g/KWH. I am using 5W40 oil for this purpose. So that the lubrication can be more efficient even during low temperature.

What do you mean by off-the shelf-component?

 

[SteamKing]

Efficiency of the engine is calculated as 90% and BSFC is 300 g/KWH. I am using 5W40 oil for this purpose. So that the lubrication can be more efficient even during low temperature.

IC combustion engines are never 90% efficient, thermally. You are lucky if a small engine is 30% efficient. Are you sure this figure doesn't refer to the volumetric efficiency of the engine, i.e., how well air flows into it?

What do you mean by off-the shelf-component?

You can purchase this item by going into a store and picking it up off the stock shelf, i.e., it's ready made.

 

[Somanna]

IC combustion engines are never 90% efficient, thermally. You are lucky if a small engine is 30% efficient. Are you sure this figure doesn't refer to the volumetric efficiency of the engine, i.e., how well air flows into it?
You can purchase this item by going into a store and picking it up off the stock shelf, i.e., it's ready made.

Yes, its volumetric efficiency.but then its assumed value. No, I don't want a off the shelf component. I am in a situation where i need to understand the concept and apply the same in design part.

 

[SteamKing]

Yes, its volumetric efficiency.but then its assumed value. No, I don't want a off the shelf component. I am in a situation where i need to understand the concept and apply the same in design part.

The volumetric efficiency of this engine is not going to tell you a lot about the heat rejection rate which your oil cooler needs to handle. You also need to identify the max. temperature your engine oil can be in order to prevent lubrication breakdown and damage to the engine.

If you are not already enrolled in a mechanical engineering program, you probably need to be, in order to get the knowledge necessary to design a cooler for this engine.