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% and 30%. The heat dissipated is measured in BTU/hr:

BTU/hr: Horsepower * 0.3 * 2542
Horsepower: Total Horsepower * 0.3
KW: Horsepower * 0.3 * 0.735

Here are some calculations for OSE engines:

Engine hp	HP Formula	Horsepower	BTU Formula	BTU/hr	KW Formula	KW
28	28 * 0.25, 28 * 0.3	7 - 8.4	28 * 0.25 * 2542, 28 * 0.3 * 2542	17794 - 21352	28 * 0.25 * 0.735, 28 * 0.3 * 0.735	5.145 - 6.174
50	50 * 0.25, 50 * 0.3	12.5 - 15	50 * 0.25 * 2542, 50 * 0.3 * 2542	31775 - 38130	50 * 0.25 * 0.735, 50 * 0.3 * 0.735	9.1875 - 11.025

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. Vendors list cooler specs by either hp or by BTU/hr.

Thermal Transfer Mobile MA series coolers:

http://www.industrialheattransfer.com/Air-Cooled/MA%20Series.pdf

The "MA-18" core has the proper heat transfer specs, the "MA-18-4" has a 12v electric fan.

AKG Mobile oil coolers:

http://www.akgts.com/fileadmin/_akgts/pdf/Cool_LineD_en.pdf

Bailey lists products using both hp and BTU/hr, has bare coolers or coolers with fans and also lists the GPM rating of the coolers:

https://baileynet.com/hydraulics/bailey_hydraulics_other_products/?productcategory=1000053

Note that some of their fan motors are hydraulic, others electric. These are bare coolers and coolers with 12V fans meeting our requirements (28.5 GPM, 12.5 - 15 hp or 31k - 38k BTU/hr):

AKG: 258-311, 258-318 Thermal Transfer: 258-329, 258-339

Hayden Auto lists coolers by BTU/hr 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.