In hydraulic power units, a system with a pump pushes the hydraulic oil under pressure inside the servomechanisms and pistons. The oil thus increase its temperature, and requires to be cooled in order to maintain its characteristics and proper operating conditions.
How to calculate the amount of heat to be dissipated from the hydraulic oil circuit?
First of all, the hydraulic oil must be regulated at a suitable temperature between 40 and 50° C, in order to properly feed pumps, cylinders and hydraulic motors. The thermal heat to dissipate is then calculated considering the power of the motor engine of the pump, that provides the circulation under pressure of the lubricating oil within the hydraulic machinery. This is indeed the element that transfers thermal power to the hydraulic oil.
The exact amount is obtained by calculating the 30 or 40%, at maximum 50%, of the power of the pump’s motor. This will be the amount of thermal energy to be dissipated from the hydraulic oil, to cool it and maintain it at the correct temperature to preserve its functions.
This is an empirical method, because there are other factors to consider such as the yield and efficiency of the pump and the electric motor. But usually this method is employed to simply determine the amount of thermal power to dissipate from the hydraulic oil. To make an example, if we have a pump with a 100 kW motor, the amount of thermal energy to remove from the hydraulic oil circuit is between 30 and 50 kW.
There is another essential factor to be considered, being the viscosity of the oil, and we’ll soon dedicate to this important topic another video.