AO Performance

The following is a general guide to help select a standard Exact Exchanger for stationary oil cooling applications. The models in the catalog are for 50 to 300 HP Coolers, models are available up to 500 HP, as well as custom units. Complete unit selection is available from the factory, consult Exact Exchanger for detailed engineering.

1. Determine the heat load to be rejected in BTU/hr. As a general rule, hydraulic systems require approximately 30% of drive horsepower to be removed. 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 constant factor of 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 1 . Using the estimated hottest day of the year for the location and elevation, find the ambient correction factor (Acf) from Table 3 .

5. Find the correction factor for your acceptable system pressure loss. Using the average fluid temperature and the oil type, find the pressure correction factor (Pcf) from Table 2.

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 1, 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 too great, proceed to the next Chart until a model is found that has a higher heat rejection capacity and a lower pressure loss than the acceptable.

Selection of an Exact Exchanger under the following conditions: (Note highlighted indicators on Tables and Charts).

A hydraulic press.................250 HP
Ambient Air Temp...............110^oF
Oil Type..............................SAE-20
Oil Inlet Temp......................180 ^oF
Oil Exit Temp......................160^oF
Maximum Pressure Drop.....15 psi
Elevation..............................3000 ft

Heat Load = (equipment HP) x 0.30 x 2545
= 250 x 0.30 x 2545
= 191,000 BTU/hr
Oil Flow Rate = Heat Load / ((180-160) x 207)
= 191,000 / (20 x 207)
= 46 GPM
Ave. Fluid Temp = (180 + 160) / 2 = 170 ^oF
From Table 1 , Tcf = 0.740
From Table 2, Pcf = 0.939
From Table 3, Acf = 1.241
Corrected Heat Load = Heat Load x Tcf x Acf
= 191,000 x 0.740 x 1.241
= 175,288 BTU/hr
Corrected Pressure Drop = Pressure Drop x Pcf
= 15 x 0.939
= 14.1 psi

The heat load and the pressure drop are satisfied by the AO 150-3.

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