Parallel Cycle Heat Engine for Low-Temperature Waste Heat Recovery
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Solution Overview
Problem
Current systems for converting waste heat into work, such as steam-based Rankine cycles and organic Rankine cycles, face limitations due to high temperature requirements, complexity, and inefficiencies in energy extraction, making them impractical for low-temperature or small flow rate waste heat sources.
Innovation Solution
A parallel heat engine cycle system utilizing carbon dioxide as a working fluid, with multiple heat exchangers and turbines arranged in series and parallel configurations, allowing for efficient thermal energy conversion across multiple temperature levels and pressure ratios, thereby maximizing power generation from waste heat sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If steam-based Rankine cycle is used, then power generation capability is improved, but temperature requirement increases to 600°F or higher
Solution Approach 1:
The patent changes the working fluid from water/steam to organic fluids with lower boiling points (such as R245fa, propane, or butane), thereby changing the operational temperature parameters of the cycle to match lower temperature waste heat sources while maintaining power generation capability
Solution Approach 2:
The patent introduces an organic Rankine cycle as an intermediary system between waste heat sources and power generation, using organic working fluids that can efficiently transfer thermal energy at lower temperatures compared to steam-based systems
2Quantity of substance
If steam-based Rankine cycle with multiple pressures/temperatures is used, then heat capture capability is improved, but equipment cost and operating labor increase
Solution Approach 1:
The patent segments the heat recovery process into multiple independent organic Rankine cycles, each operating at different temperature levels with dedicated heat exchangers and expanders, allowing flexible configuration that reduces overall system complexity compared to multi-pressure steam systems
Solution Approach 2:
The organic Rankine cycle system is designed to universally handle various waste heat sources across different temperature ranges using the same fundamental cycle architecture, eliminating the need for complex custom-designed multi-pressure steam systems for each application
3Use of energy by moving object
If single cycle supercritical CO2 power cycle is used, then thermal coupling with heat sources is improved, but temperature reduction and energy extraction are limited
Solution Approach 1:
The patent divides the single supercritical CO2 cycle into multiple sequential or parallel cycles, each extracting energy at different pressure ratios and temperature levels, thereby fully utilizing the available thermal energy and minimizing residual energy in the exhaust fluid
Solution Approach 2:
The patent extends the single-dimension single-cycle approach to multi-dimensional parallel or series cycle configurations, enabling energy extraction across multiple pressure and temperature dimensions to maximize overall energy utilization
4Temperature
If organic Rankine cycle is used, then temperature requirement is reduced, but thermal instability and fluid safety issues are introduced
Solution Approach 1:
The patent carefully selects organic working fluids with optimized physical and chemical parameters (such as R245fa, propane, or butane) that balance low boiling point requirements with thermal stability and safety characteristics, avoiding fluids with excessive toxicity or flammability
Solution Approach 2:
The patent uses well-established organic fluids as intermediary working substances that mediate between heat source and power generation while maintaining known and controllable thermal stability and safety properties
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 effectively converts a wide range of thermal energies into work by optimizing heat transfer across multiple stages, increasing thermal efficiency and power output, and is suitable for various industrial and renewable thermal sources.
Implementation Method 1
thermal communication with the heat source via a first heat exchanger arranged in series with a second heat exchanger
Implementation Method 2
a first turbine arranged in parallel with a second turbine and in fluid communication with the first heat exchanger; and a second turbine arranged in parallel with a first turbine
Data Source
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AI summary
Waste heat energy conversion cycles, systems and devices use multiple waste heat exchangers arranged in series in a waste heat stream, and multiple thermodynamic cycles run in parallel with the waste heat exchangers in order to maximize thermal energy extraction from the waste heat stream by a working fluid. The parallel cycles operate in different temperature ranges with a lower temperature work output used to drive a working fluid pump. A working fluid mass management system is integrated into or connected to the cycles.