13B heat analysis- Rough numbers (long)

[Aaron]

I have some rough numbers for a 13B running at 300HP (turbo) and 200 HP, which may be of use, or at least a topic of discussion. These numbers are all theory, I have no experimental data to back them up, yet.

 

I ran some simulations on the 13b engine, the goal being to quantify heat loads, heat exchanger area, required air flows, etc.

 

i started with a 13gph fuel flow,and mixed in air at a 15:1 ratio (highest theoretical heat production), after combusting it and removing 200 HP of shaft work, I come up with a heat load (oil and water combined) of .54 MMBTU/hr.

 

Running at 18 gph fuel and 300 HP brings the heat load to .69MMBTU/hr.

 

These numbers seem reasonable, as an old rule of thumb for 4-cycle engines is 1/3 energy to work, 1/3 out the exhaust, 1/3 to cooling.

 

Many people make the assumption that 2/3 cooling goes to water, 1/3 to oil, but since I have no numbers to back that up, I'm going to assume all the heat goes to water for now.

 

Cooling water flow:

Assuming our water exits the radiator at 160F, and the max temp we want is 185F, our cooling flowrate is 67 gpm for 300HP, 52 gpm for 200HP .

 

Cooling air flow:

The amount of air needed, assuming air enters at 100F and leaves at 150F, is 13,400 cfm (actual) for 300HP; 10,500 cfm for 200HP

 

Assuming the duct inlet velocity is 90 mph, you need a duct inlet area around 1.7 sq feet for 300HP, 1.3 for 200HP

 

Cooling area requirements:

I'm still looking for good info on heat transfer coefficient and area for radiators, I'll probably have to run experiments to confirm anyways.

 

Again, the numbers posted here are for discussion and entertainment only.

 

Does anyone have any realworld info they could contribute here?

 

oh yeah, one last thing, these numbers should be good for any engine with similar fuel burn and HP.

[Aaron]

Neglected the effect of air density in calculating the air requirements- for a 300 HP engine at 10,000 feet, the cooling air needed is nearly 20,000 cfm, giving a duct inlet of 2.5 sq feet @ 90 mph inlet velocity.

 

EDIT: arrgh, forgot to account for the temp at altitude. If the inlet air is at 10000 feet (10.2 psia) and 50F the area requirements work ouy to 1.11 sq feet (8820 cubic feet/min) this is for the 300HP case.

 

How big is the Naca Inlet on the Cozy anyway?