Add more detailed pressure exchanger #1264
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| # Performance equations | ||
| @self.Constraint(self.flowsheet().config.time, doc="Pressure transfer") | ||
| def eq_pressure_transfer(b, t): | ||
| return ( | ||
| b.low_pressure_side.deltaP[t] | ||
| == b.efficiency_pressure_exchanger[t] * -b.high_pressure_side.deltaP[t] | ||
| b.feed_side.deltaP[t] |
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I suggest implementing a more precise efficiency calculation method for PressureExchangeType.high_pressure_difference option, defining efficiency as the ratio of energy output to energy input. This approach effectively incorporates the effects of HPD and leakage into efficiency
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@ElmiraShamlou the current definition of efficiency in eq_pressure_transfer is exactly same as ratio of energy output to energy input. I've tried to directly define the efficiency based on the energy output/energy input and get exact same results. Though, it is not so evident, ΔP_FS=-ηΔP_BS is same as energy output/ energy input
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Thanks @luohezhiming . The current definition of efficiency is equivalent to energy ratios only when there's no leakage and the flow rates on both the feed and brine sides are the same. You got the same results from both methods because the leakage was either very small or zero. But if leakage increases, it will have a bigger effect on efficiency. We can include the leakage inefficiency in a complete energy equation that incorporates both pressure and flow rates.
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I redefine the efficiency as the ratio of energy_in over energy_out, but I find the solution results will change for the no_mass_transfer case. Since a lot of flowsheet use this basic pressure exchanger without mass transfer, @TimBartholomew , I want to confirm with you should we change this efficiency equation? If we do, then all flowsheets using the pressure exchanger will have different results.
| > 1e-4 | ||
| and not self.config.has_mass_transfer | ||
| and not self.config.has_mixing |
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I'm not sure if this error message actually helps with initialization. If we need to keep it, maybe we should change self.config.has_mixing to self.config.has_leakage.
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@ElmiraShamlou I agree we also have to add has_leakage for this check, but we also need to include has_mixing because we introduce mass_transfer_term into the control volume when add mixing even though it might not affect the volumetric flowrate if there is no leakage, but the introduced mass_transfer_term might cause some minor errors. Note that in most cases without transfer, after initialization, we should have Q_FS_in=Q_BS_out and deactivate the equal_flow_vol constraint to make initialization work.
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@luohezhiming please tag this in the issue for tracking any potential updates we may (or may not) want to make in in a future PR. For now, I think we can merge what you have for the March release and refine later, if needed.
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LGTM - @luohezhiming please make an issue to track any potential improvements we might want to consider later for the detailed presssure exchanger. I have on or two that come to mind, so I will add after you start the issue.
Fixes/Resolves:
replace this with the issue #1262 fixed or resolved,
Summary/Motivation:
Add more details for the pressure exchanger that accounts for leakage, mixing, and the pressure differential
Changes proposed in this PR:
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