# Air Oil Cooler Selection---Heat Calculation

Calculate the heat loss per unit time of the hydraulic system, that is, the heating power Pv of the system, and then combine the oil temperature expectation value T1 you need, and compare the equivalent cooling power P1 graph of the air cooler to select the CHANCE model. This is a commonly used calculation method.

Attention that when measuring the temperature rise of the oil per unit time of the system, it is necessary to distinguish whether there is a cooler at work. The working condition referred to in this article is the temperature rise of the oil when the system does not have an air oil cooler.

Calculation formula: Pv = ρ oil × V × C oil × ΔT / H, where:

Pv: heating power (W)

ρ oil: the density of oil (usually 0.85Kg / L) V: volume of oil (L) C oil: the specific heat capacity of hydraulic oil, often taking 2.15Kj/Kg °C

ΔT: temperature rise of oil in a certain period of time H: temperature rise time (s)

For example: In a hydraulic system (without air cooler), the oil temperature rises from 30 °C to 45 °C in 10 minutes, and the volume of hydraulic oil is 80L. The heating power is calculated as follows:

Pv=0.85×80×2.15×(45-30)/(10×60)=3.655Kw

Knowing that the ambient temperature is T2=30°C and the optimum oil temperature is expected to be 55°C, the equivalent cooling power is calculated as follows:   P1=Pv×η/(T1-T2), where:   P1: equivalent cooling power (w/°C)   η: safety factor, generally taken 1.1   T1: oil temperature expectation (°C)   T2: ambient temperature (°C)   Therefore: P1=3.655×1.1/(55-30)=0.161Kw/°C=161w/°C   Corresponding to the main pump flow, according to the equivalent cooling power of 161w / °C check the graph, select the matching air cooler.   The most convenient heat dissipation calculation method is the heating power estimation method: generally take 1/3~1/2 of the total power of the system as the cooling power of the cooler, if the working condition is a long-term pressure holding state (such as clamping operation) ), then the maximum value of the coefficient is recommended 2/3.