Hydraulic Cooler Sizing

This page describes how to size a hydraulic oil cooler for a hydraulic system. Hydraulic coolers are often specified by their ability to dissipate heat - usually measured in BTU/hr.

1. The power in the hydraulic system:

Horsepower = Pressure * Flow / 1714

2. The heat dissipated in a hydraulic system can be determined by summing the inefficiencies of all components in the system, but is usually between 25% adn 30%. The heat dissipated is measured in BTU/hr:

Heat dissipated = Horsepower * 0.3 * 2542

Here are some calculations for OSE engines:

Engine hp	HP Formula	Horsepower	BTU Formula	BTU/hr
28	28 * 0.25, 28 * 0.3	7 - 8.4	28 * 0.25 * 2542, 28 * 0.3 * 2542	17794 - 21352
50	50 * 0.25, 50 * 0.3	12.5 - 15	50 * 0.25 * 2542, 50 * 0.3 * 2542	31775 - 38130

3. Select a cooler based on the BTU/hr derived in step 1 above. For the case of the 50 hp Power Cube, search for coolers that dissipate between 31775 and 38130 BTU/hr. One resource for choosing a cooler is the following page from HaydenAuto.com - in the section "Heavy Duty Oil Coolers":

http://www.haydenauto.com/upload/HaydenAuto/Documents/Cat_Hayden/2007-hayden-trans-oil-coolers.pdf

Note: The "COOLING BTU / HR" ratings is with 2500 cubic-ft/min airflow and 100°F differential in oil and air temperatures. So, this requires a fan to move the air to meet these requirements.