Double Pinch Criterion for Regenerative Rankine Cycle Optimization
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Solution Overview
Problem
Rankine cycles, despite their widespread use in electricity production, face challenges in achieving optimal efficiency due to limitations in existing designs and operating conditions, necessitating improvements to enhance economic and environmental performance.
Innovation Solution
Implementing a double pinch criterion in regenerative Rankine cycles by optimizing bleed extraction pressure and flow rate to achieve a double pinch in the feedwater heater, which involves a first pinch point at the onset of condensation and a second pinch point at the exit of the bleed, allowing for improved heat transfer efficiency without the need for spatial discretization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional single pinch criterion is used in feedwater heater design, then design simplicity is maintained, but heat transfer efficiency is insufficient
Solution Approach 1:
The patent divides the heat transfer process in the feedwater heater into two distinct pinch point regions: the first pinch point at the condensation onset and the second pinch point at the bleed exit. This segmentation allows independent optimization of heat transfer efficiency at each region, resolving the contradiction by achieving superior thermal efficiency without requiring complex multi-parameter optimization across the entire heat exchanger.
Solution Approach 2:
The invention changes the optimization parameter from a single temperature difference constraint to two separate temperature difference constraints at two different locations. By specifying minimal approach temperatures at both the first pinch point (condensation onset) and second pinch point (bleed exit), the system achieves enhanced heat transfer efficiency while maintaining manageable design complexity through clear parameter specifications.
2Productivity
If bleed extraction pressure and flow rate are optimized for maximum efficiency, then power generation increases, but turbine output decreases due to bleed losses
Solution Approach 1:
The patent optimizes the bleed extraction parameters (pressure and flow rate) by establishing temperature difference constraints at two pinch points rather than using conventional single-point optimization. This dual-constraint approach identifies optimal operating conditions that maximize cycle efficiency and power generation while minimizing the negative impact on turbine output, achieving a better balance between productivity and power.
Solution Approach 2:
The optimization method uses temperature difference measurements at both pinch points as feedback to determine optimal bleed extraction conditions. By monitoring and adjusting based on temperature differences at the condensation onset and bleed exit, the system achieves improved power generation while compensating for turbine output losses through precise parameter control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the overall efficiency of Rankine cycles by minimizing temperature differences at both pinch points, leading to significant economic and environmental benefits, including increased power generation and reduced energy losses.
Implementation Method 1
The feed is healed in a feedwater heater configured to exchange heat between a first flow path through which the feed flows and a second flow path through which the bleed flows
Implementation Method 2
a first pinch point at the onset of condensation of the bleed
Data Source
AI summary
Systems and methods axe disclosed herein that generally involve a double pinch criterion for optimization of regenerative Rankine cycles. In some embodiments, operating variables such as bleed extraction pressure and bleed flow rate are selected such that a double pinch is obtained in a feedwater heater, thereby improving the efficiency of the Rankine cycle. In particular, a first pinch point is obtained at the onset of condensation of the bleed and a second pinch point is obtained at the exit of the bleed from the feedwater heater. The minimal approach temperature at the first pinch point can be approximately equal to the minimal approach temperature at the second pinch point. Systems that employ regenerative Rankine cycles, methods of operating such systems, and methods of optimizing the operation of such systems are disclosed herein in connection with the double pinch criterion.