Accumulator volume problem
Accumulator volume problem
(OP)
I came across an accumulator volume problem that needs help.
I charged the an EPE AS55 accumulator from 0 to 4500 psi and turned off inlet valve. The pressure droped a little and stablized at 4000 psi. Then I opened outlet valve to collect water till pressure droped to 1600 psi.
In this case P1=1600 psi, P2=4500 psi, so accumulator precharge pressure P0=1300 psi. According to the chart, I expected the volume to be 24.5 litre, but only managed to get 17.5 litre.
Can anybody recomment on the shortage of volume. Thanks in advance.
I charged the an EPE AS55 accumulator from 0 to 4500 psi and turned off inlet valve. The pressure droped a little and stablized at 4000 psi. Then I opened outlet valve to collect water till pressure droped to 1600 psi.
In this case P1=1600 psi, P2=4500 psi, so accumulator precharge pressure P0=1300 psi. According to the chart, I expected the volume to be 24.5 litre, but only managed to get 17.5 litre.
Can anybody recomment on the shortage of volume. Thanks in advance.
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RE: Accumulator volume problem
For example, the AS55 has a 50 liter gas volume bladder and you have define P0 = 1300, P1=1600 and P2=4000.
Calculating the isothermal volume changes would be as per the equations
P0XV0=P2XV2 gives V3=(P0/P2)XV0 or (1300/4000)X50, which gives V2=16.3
Simairly P2XV2=P1XV1 gives V1=40.6. The expected fluid would be V1-V2 = 24.3
This volume agrees with your chart.
Assuming the accumulator is charges with N2 (ideal gas k=1.4). Allowing the pressure to stabilize after filling will be isothermal, thus V2 would be the same. The adiabatic expansion from P2 to P1 would be as per the equations
P2XV2^1.4=P1XV1^1.4, gives V1=V2X(P2/P1)^(1/1.4) or 16.3X(4000/1600)^0.71, which gives V1= 31.4. The expected fluid would be V1-V2=15.1 While calculated volume is less than your results, since some heat would have been absorbed by the accumulator, it agrees with what you observed.