AOC Performance

The following is a general guide to selecting a standard Exact Exchanger for mobile oil cooling applications. Complete unit selection is available from the factory as well as custom units, consult Exact Exchanger for detailed engineering.

1. Determine the heat load to be rejected in BTU/hr. As a general rule, automatic transmissions require 30% of the drive horsepower to be removed. While engines require approximately 10% of the engine horsepower to be removed. Multiply the horsepower by 2545 to obtain the heat load in BTU/hr.

2. Determine the oil flow rate through the cooler in Gallons Per Minute. If unknown, the flow rate can be estimated by dividing the heat load in BTU/hr by the oil inlet temperature minus the oil exit temperature in degrees Fahrenheit, which is multiplied by a factor 207.

4. Find the correction factors for fluid temperature and ambient temperature. Using the average fluid temperature and the oil type, find the temperature correction factor (Tcf) from Table 5. Using the estimated hottest day of the year and the estimated air flow velocity, find the ambient correction factor (Acf) from Table 6.

5. Find the correction factor for your acceptable system pressure drop. Using the average fluid temperature and the oil type, find the pressure correction factor (Pcf) from Table 7.

6. Determine the corrected heat load and oil pressure drop. Multiply the heat load by the Tcf and Acf. Multiply the maximum pressure drop by the Pcf.

7. Beginning with Chart 8, find the intersection of the fluid flow rate and the heat load. If the intersection is below one of the curves check the oil pressure drop on that curve, if it is below the acceptable system pressure loss choose that model. If the heat load or the pressure loss was greater than the models on Chart 8, proceed to Chart 9. If none of the models meet the heat load or pressure drop criteria, consult the factory for custom units.

Selection of an Exact Exchanger for the following conditions:

(Note highlighted indicators on the Tables and Charts).

Engine Horsepower........... 200 HP
Ambient Air Temp............. 90^oF
Air Flow Rate.................... 500 FPM
Oil Type............................ SAE-10
Oil Inlet Temperature......... 170^oF
Oil Exit Temperature.......... 150ºF
Allowable Pressure Drop.... 20 psi

Heat Load = (equipment HP) x 0.10 x 2545
= 200 x 0.10 x 2545
= 50,900 BTU/hr
Oil Flow Rate = Heat Load / ((170 - 150) x 207)
= 50,900 / ((20) x 207)
= 12.3 GPM
Avg. Fluid Temp. = (170 + 150) / 2 = 160^oF
From Table 5, Tcf = 0.841
From Table 6, Acf = 0.925
From Table 7, Pcf = 1.024
Corrected Heat Load = Heat Load x Tcf x Acf
= 50,900 x 0.841 x 0.925
= 40,000 BTU/hr
Corrected Pressure Drop = Pressure Drop x Pcf
= 20 x 1.024
= 20.5 psi

The heat load and the pressure drop are satisfied by the AOC 45.