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Microhidráulica Industrial

Bulk Modulus (Actual)

The previous examples used a constant bulk modulus for simplicity. In actual use, the bulk modulus is affected by the working pressure, temperature and percent of entrained air. Use the next 3 graphs to find the effect of these variables, and you will get a close approximation of actual conditions. The actual bulk modulus, B, of a fluid is the value in the table here as Bref. modified for the effect of pressure, temperature and percent of entrained air.

The actual bulk modulus B    =    EP    x    ET    x    EA    x    Bref.

EXAMPLE:

500 psi, 60°F, 2% entrained air, MIL-H-83282.
Actual B = 0.91 x 1.10 x 0.8 x 300,000 = 240,000 psi

EXAMPLE:

2000 psi, 160°F, 2% entrained air, MIL-H-83282.
Actual B = 0.98 x 0.86 x 0.98 x 300,000 = 248,000 psi

With the corrected bulk moduli for the two end points of a thermal problem, an average bulk modulus can be selected for calculation purposes. We would use 244,000 psi for B.

The previous examples used a constant bulk modulus for simplicity. In actual use, the bulk modulus is affected by the working pressure, temperature and percent of entrained air. Use the next 3 graphs to find the effect of these variables, and you will get a close approximation of actual conditions. The actual bulk modulus, B, of a fluid is the value in the table here as Bref. modified for the effect of pressure, temperature and percent of entrained air.

The actual bulk modulus B    =    EP    x    ET    x    EA    x    Bref.

EXAMPLE:

500 psi, 60°F, 2% entrained air, MIL-H-83282.
Actual B = 0.91 x 1.10 x 0.8 x 300,000 = 240,000 psi

EXAMPLE:

2000 psi, 160°F, 2% entrained air, MIL-H-83282.
Actual B = 0.98 x 0.86 x 0.98 x 300,000 = 248,000 psi

With the corrected bulk moduli for the two end points of a thermal problem, an average bulk modulus can be selected for calculation purposes. We would use 244,000 psi for B.