Hydraulic Cooler Sizing

This page describes how to size a hydraulic oil cooler for a hydraulic system.

Formulas

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%. In this document, we will use the range of 25% - 30%.

Heat dissipated is units of BTU/hr, horsepower or kW. This document will show heat dissipation in all three units (only 30% inefficiency shown):

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

Heat to Dissipate

Hydraulic coolers are often specified by their ability to dissipate heat - usually measured in BTU/hr, horsepower or watts

Here are some calculations for OSE engines:

Engine hp	HP Formula	Horsepower	BTU Formula	BTU/hr	KW Formula	KW
16				11000		3
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
65	65 * 0.25, 65 * 0.3	16.25 - 19.5	65 * 0.25 * 2542, 65 * 0.3 * 2542	41307 - 49569	65 * 0.25 * 0.735, 65 * 0.3 * 0.735	11.943 - 14.3325

Selecting a Cooler

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 with heat dissipation and Gallons/Min or Liters/Min.

AKG Mobile oil coolers:

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

The AKG "D11" cooler seems to meet our requirements.

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

Hayden model 1284 meets the requirements and is 16-3/4" x 24" x 1-1/2" in size.

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.

Thermal Transfer Mobile MA series coolers:

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

The "MA-20" (13.78" x 14.33") and "MA-18" (11.81" x 11.81") cores have the proper heat transfer specs
The "MA-18-4" is the "MA-18" core with a 12v electric fan, the MA-20 has no fan option

Of the three models listed above, the MA-18 and MA-20 from Thermal Transfer are the only ones whose cooling area are square. This shape is best suited for a circular fan. If all other factors are the same, one of these would be the obvious choice.

Summary

We have seen how to assess the heat dissipation of a hydraulic system and how to select an oil cooler for dissipating this heat.