Abstract
Two hydraulic transmissions are tested for determination of the efficiency by two methods, the basic one by hydraulic measurements and the other by thermodynamic measurements. The hydraulic method is giving the total efficiency of the transmission on the base of hydraulic power input to the motor and hydraulic power output from the pump. By the thermodynamic method the efficiency is determined for each one of the units, the motor and the pump. The results from these tests show an agreementbetween these two methods within 2-3% when temperature difference Δt between the oil and the environment is approximately zero. A model function is suggested for reducing the deviation Δη between the two methods for correcting the thermodynamic evaluations to agree with the hydraulic evaluations of the efficiency.
