To go one step further in this tangent.. two stage cooling utilizing phase change.. for simple hillbilly math numbers as an example to express a concept.
Assuming.. engine fuel burn rate of 0.5lbs/hr/hp, Energy of gasoline at 18,400 btu per pound. Engine efficiency of 30%, waste heat divided equally between exhaust and cooling system.
For a 150 hp engine we get 150*0.5*18,400*0.35= 483,000 btu per hr heat rejection required. An off the shelf modern plate and frame heat exchanger rated at 570,000btu/hr is about 13”x5”x6” and under 15 pounds. The plate and frame is mounted low but close to the engine, side A of it running pressurized engine coolant, side B is connected to the remotely located radiator. Side B is operated as a hermetically sealed system, evacuated to deep vacuum and charged with a quantity of ethyl alcohol (other options if it’s flammability is a concern) that is sufficient to flood the plate and frame with a bit of excess. Connection between the radiator and plate and frame is arranged to allow gravity flow back of condensate. The entire area of the radiator receives equal heat distribution and is no longer subject to flow disruptions on the fluid side, the increase in heat carrying capacity per mass flow of the side B coolant by utalizing phase change allows much smaller (lighter) connection runs, and with most of side B operating in a gaseous state the mass of coolant is also reduced more than off setting the weight of the plate and frame.
Assuming.. engine fuel burn rate of 0.5lbs/hr/hp, Energy of gasoline at 18,400 btu per pound. Engine efficiency of 30%, waste heat divided equally between exhaust and cooling system.
For a 150 hp engine we get 150*0.5*18,400*0.35= 483,000 btu per hr heat rejection required. An off the shelf modern plate and frame heat exchanger rated at 570,000btu/hr is about 13”x5”x6” and under 15 pounds. The plate and frame is mounted low but close to the engine, side A of it running pressurized engine coolant, side B is connected to the remotely located radiator. Side B is operated as a hermetically sealed system, evacuated to deep vacuum and charged with a quantity of ethyl alcohol (other options if it’s flammability is a concern) that is sufficient to flood the plate and frame with a bit of excess. Connection between the radiator and plate and frame is arranged to allow gravity flow back of condensate. The entire area of the radiator receives equal heat distribution and is no longer subject to flow disruptions on the fluid side, the increase in heat carrying capacity per mass flow of the side B coolant by utalizing phase change allows much smaller (lighter) connection runs, and with most of side B operating in a gaseous state the mass of coolant is also reduced more than off setting the weight of the plate and frame.
