Supercritical CO2 Heat Engine Cycles for High Ambient Conditions
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Solution Overview
Problem
Existing thermodynamic systems, particularly those using supercritical CO2, face limitations in power generation due to restricted pressure ratios and efficiency issues in high-ambient temperature environments, where conventional heat exchangers struggle to condense the working fluid effectively, leading to reduced energy extraction from waste heat sources.
Innovation Solution
A system with multiple compression stages and intercoolers, coupled with heat exchangers and recuperators, is designed to efficiently manage the working fluid's temperature and pressure, allowing for enhanced heat transfer and power generation by utilizing a series of heat exchangers and recuperators to maximize pressure ratios and thermal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional heat exchangers are used to condense working fluid in high-ambient temperature environments, then the system structure remains simple, but the condensation efficiency deteriorates and cycle efficiency is reduced
Solution Approach 1:
The heat exchanger is divided into multiple stages with different temperature profiles. The first heat exchanger operates at higher temperatures while the second heat exchanger operates at lower temperatures, allowing efficient condensation across the full temperature range even in high-ambient conditions.
Solution Approach 2:
The system changes the temperature parameters of the working fluid through staged heat exchange. By sequentially cooling the fluid through two heat exchangers at different temperature levels, the condensation process is optimized for high-ambient temperature environments.
2Device complexity
If single-cycle supercritical CO2 power cycles are used, then the system complexity is low, but the pressure ratio is limited and power extraction is reduced
Solution Approach 1:
The power generation system is segmented into multiple cycles that operate in parallel. Each cycle can be optimized for specific pressure ratios and temperature ranges, allowing the system to extract maximum power from the waste heat source while maintaining manageable complexity through modular design.
Solution Approach 2:
The system employs a multi-functional heat exchanger arrangement that serves multiple purposes: heating the working fluid, condensing the exhaust, and pre-heating the incoming fluid. This universal approach maximizes power extraction without requiring separate dedicated components for each function.
3Power
If the pressure ratio is increased to maximize power extraction, then the power output improves, but the condensation temperature requirement increases and cycle efficiency deteriorates in high-ambient conditions
Solution Approach 1:
The condensation process is segmented into two stages with different temperature requirements. The first heat exchanger handles the high-temperature condensation while the second handles the low-temperature condensation, allowing the system to achieve high pressure ratios without being constrained by single-temperature condensation limitations.
Solution Approach 2:
The system maintains continuous heat exchange action across both heat exchangers, ensuring that the working fluid is continuously cooled through the full temperature range. This continuous action allows high pressure ratios to be maintained while preserving cycle efficiency by eliminating temperature gaps in the heat transfer process.
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 configuration enables increased power extraction and efficiency from waste heat sources, even in high-ambient temperature conditions, by effectively utilizing residual heat and optimizing the working fluid's thermal energy conversion into work.
Implementation Method 1
one or more intercoolers, each being disposed between two of the plurality of compression stages and configured to cool the working fluid
Implementation Method 2
first and second heat exchangers coupled to a source of heat and disposed downstream from the second compression stage. The first heat exchanger is configured to transfer heat from the source of heat to the first mass flow
Implementation Method 3
The first turbine is configured to receive the first mass flow from the first heat exchanger and the second turbine is configured to receive the second mass flow from the second heat exchanger
Implementation Method 4
The first recuperator is configured to transfer heat from the working fluid on the high temperature side to working fluid on the low temperature side
Data Source
AI summary
A system for converting thermal energy to work. The system includes a working fluid circuit, and a precooler configured to receive the working fluid. The system also includes a compression stages and intercoolers. At least one of the precooler and the intercoolers is configured to receive a heat transfer medium from a high temperature ambient environment. The system also includes heat exchangers coupled to a source of heat and being configured to receive the working fluid. The system also includes turbines coupled to one or more of the heat exchangers and configured to receive heated working fluid therefrom. The system further includes recuperators fluidly coupled to the turbines, the precooler, the compressor, and at least one of the heat exchangers. The recuperators transfer heat from the working fluid downstream from the turbines, to the working fluid upstream from at least one of the heat exchangers.