Time taken for pressure equalization between two tanks

  • Thread starter Thread starter Raghav Seetharamu
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The discussion focuses on calculating the time required for pressure equalization between two tanks containing air. The rough equilibrium pressure is determined using the equation Ptot = (P1V1 + P2V2) / Vtot, with exponential equations proposed for modeling pressure changes over time. The assumption that the exponential constant B is the same for both tanks is questioned, highlighting the need for additional information regarding the transport dynamics between the tanks. The pressure difference and flow resistance through the connecting pipes significantly influence the rate of pressure change. Understanding these factors is crucial for accurately determining the time taken for pressure equalization.
Raghav Seetharamu
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Homework Statement


How to calculate time taken (rough approximation) for pressure equalization between two tanks.
Both the tanks have same fluid (Air).

Homework Equations


Rough equilibrium pressure can be achieved by using equations Ptot = (P1V1+P2V2)/Vtot.
Thought of using exponential equation P=Ae^(Bt) for calculating time required for pressure equalization.
A and B are constants.
P=A1e^(-Bt) for tank with decreasing pressure;
P=A2e^(Bt) for tank with increasing pressure;

Exponential constant B, is assumed to be same for the tanks. Am I correct with this assumption?

The Attempt at a Solution


P1 = 1000mbar; P2 = 0.1mbar, V1=6m3, V2 = 1m3,
Ptot = 860 mbar

P=1000*e^(-Bt) for tank with decreasing pressure ;
P=0.1*e^(Bt) for tank with increasing pressure;

How to obtain the exponential constant and hence the time taken for pressure equalization using these equations?
 
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Hello Rahghav, ##\qquad##:welcome: ##\qquad## !

To settle this somewhat, you need more information: a certain amount of material has to be transported from one vessel to the other. The rate depends on the pressure difference and on the resistance in that transport: is it a thin and very long tube or a big short pipe ?
 
BvU said:
Hello Rahghav, ##\qquad##:welcome: ##\qquad## !

To settle this somewhat, you need more information: a certain amount of material has to be transported from one vessel to the other. The rate depends on the pressure difference and on the resistance in that transport: is it a thin and very long tube or a big short pipe ?
Thanks for reverting:)
They are connected through relatively big and short pipes.
 
Suppose the pressures at time t are P1(t), Ppipe(t), P2(t). A= cross-sectional area of pipe, L=length.
Mass velocity in pipe = v(t).
Can you write some equations for how the pressure differences result in acceleration of air into, through and out of the pipe, and for how the rate of flow affects P1 and P2?
Bear in mind that density depends on pressure. You should probably assume adiabatic compression/decompression.
 
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