Compound Closed-Loop Heat Cycle for Waste Heat Recovery
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Solution Overview
Problem
Conventional steam Rankine bottoming cycles for waste heat recovery are inefficient and bulky due to constraints of the working fluid, particularly at low temperatures, and require complex de-aeration units for low-pressure condensation.
Innovation Solution
A compound closed-loop heat cycle system combining a Brayton top cycle with carbon dioxide vapor and a Rankine bottom cycle using a hydrocarbon working fluid, where carbon dioxide vapor is heated in the Brayton cycle and transferred through heat exchangers to heat the working fluid in the Rankine cycle, facilitating efficient heat exchange and electricity generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional steam Rankine bottoming cycle is used for waste heat recovery, then electricity can be generated from waste heat, but the system becomes bulky and complex due to large low-pressure turbine and condenser volumes required for low-pressure steam condensation
Solution Approach 1:
The patent changes the pressure parameter of steam condensation from low pressure to atmospheric pressure. This parameter change allows the use of a compact condenser without requiring large volumes, while still enabling efficient heat recovery and electricity generation through the Rankine cycle
2Power
If a conventional steam Rankine bottoming cycle is used for waste heat recovery, then electricity can be generated from waste heat, but the system requires complex de-aeration units to remove atmospheric air that leaks into sub-atmospheric pressure vessels
Solution Approach 1:
The patent changes the pressure parameter from sub-atmospheric to atmospheric pressure for steam condensation. This eliminates the need for de-aeration units and simplifies the system by removing complex air removal equipment, while maintaining electricity generation capability
Solution Approach 2:
The patent extracts and removes the de-aeration units and sub-atmospheric pressure vessels from the system. By operating at atmospheric pressure, these complex components are no longer needed, simplifying the overall system design
3Power
If water-based steam Rankine cycles are used for low temperature waste heat recovery, then electricity can be generated, but the system becomes inefficient and costly
Solution Approach 1:
The patent optimizes temperature and pressure parameters for low-temperature waste heat applications. By adjusting these parameters and operating at atmospheric pressure, the system achieves improved thermal efficiency and reduced energy losses while generating electricity from low-temperature heat sources
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
The system achieves higher efficiency and compactness by using carbon dioxide as a non-flammable, non-toxic working fluid that withstands high temperatures, eliminating the need for de-aeration units and optimizing heat recovery from both high-temperature and low-temperature waste heat sources.
Implementation Method 1
a heater configured to circulate carbon dioxide vapor in heat exchange relationship with a hot fluid from a heat source to heat carbon dioxide vapor
Implementation Method 2
A Rankine cycle system is coupled to the Brayton cycle system and configured to circulate a working fluid in heat exchange relationship with the carbon dioxide vapor to heat the working fluid
Data Source
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AI summary
A waste heat recovery system includes a Brayton cycle system having an heater (46) configured to circulate carbon dioxide vapor in heat exchange relationship with a hot fluid to heat carbon dioxide vapor. A Rankine cycle system is coupled to the Brayton cycle system and configured to circulate a working fluid in heat exchange relationship with the carbon dioxide vapor to heat the working fluid.