Thermal energy conversion method
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Solution Overview
Problem
Current steam-based Rankine cycle systems are not practical for waste heat utilization due to high temperature and large heat content requirements, making them costly and inefficient for streams with small flow rates or low temperatures.
Innovation Solution
A waste heat recovery system utilizing a thermodynamic cycle with a working fluid circuit that includes a waste heat exchanger, expander, recuperator, cooler, pump, and mass management system, operating with carbon dioxide or other selected fluids to convert thermal energy into mechanical energy across a wide range of thermal sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If steam-based Rankine cycle is used, then high temperature heat sources can be utilized, but equipment cost and operating labor increase significantly
Solution Approach 1:
The patent changes the working fluid from water/steam to organic fluids with lower boiling points (such as R134a, R245fa, or isopentane). This parameter change allows the system to operate effectively with lower temperature heat sources (down to 50-100°C) while maintaining efficient thermodynamic cycle operation, thereby reducing equipment complexity and cost
Solution Approach 2:
The patent employs simpler heat exchanger designs and avoids the complex multi-pressure steam generation systems required for traditional Rankine cycles. By using organic working fluids that can be charged into sealed systems, the patent eliminates the need for complex boiler systems, pressure vessels, and associated safety equipment, reducing both capital and operating costs
2Quantity of substance
If steam-based Rankine cycle is used, then large heat content streams can be converted to power, but it becomes impractical for small flow rate streams
Solution Approach 1:
The patent changes the operating parameters of the thermodynamic cycle by using organic working fluids with lower critical temperatures and pressures compared to water. This enables the system to efficiently process small flow rate streams with lower heat content, as the organic fluids can achieve effective phase changes and energy conversion at much lower temperatures and pressures than steam systems require
Solution Approach 2:
The patent employs a flexible heat exchanger design that can adapt to varying flow rates and temperature profiles. The system dynamically adjusts operating conditions to maintain optimal efficiency across different heat source characteristics, making it suitable for both small and large flow rate applications
3Loss of energy
If multiple pressure/temperature levels are used to capture heat, then heat recovery efficiency improves, but system cost and complexity increase
Solution Approach 1:
The patent combines the heat recovery function into a single integrated organic Rankine cycle system rather than using separate heat exchangers at multiple pressure levels. The working fluid absorbs heat from the waste heat stream in one or more heat exchangers, then expands through a single turbine or expander to generate power, simplifying the system while maintaining effective heat recovery
Solution Approach 2:
The patent designs the heat exchanger to perform multiple functions: heating the working fluid to its boiling point, facilitating phase change, and potentially providing preheating or superheating in a single integrated component. This multi-functional approach reduces the number of separate equipment items needed while maintaining high heat recovery efficiency
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 efficiently converts waste heat into mechanical energy, reducing equipment and labor costs by operating effectively with lower temperature and smaller heat content sources, and is flexible with various working fluids and heat exchanger technologies.
Implementation Method 1
a waste heat exchanger in thermal communication with a waste heat source also connected to the working fluid circuit, whereby thermal energy is transferred from the waste heat source to the working fluid
Implementation Method 2
thermal energy is transferred from the waste heat source to the working fluid in the working fluid circuit
Implementation Method 3
an expander located between the high pressure side and the low pressure side of the working fluid circuit, the expander operative to convert a pressure/enthalpy drop in the working fluid to mechanical energy
Implementation Method 4
a recuperator in the working fluid circuit operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit
Implementation Method 5
a cooler in thermal communication with the low pressure side of the working fluid circuit operative to control temperature of the working fluid in the low side of the working fluid circuit
Implementation Method 6
a pump in the working fluid circuit and connected to the low pressure side and to the high pressure side of the working fluid circuit and operative to move the working fluid through the working fluid circuit
Data Source
AI summary
A method for converting thermal energy into mechanical energy in a thermodynamic cycle includes placing a thermal energy source in thermal communication with a heat exchanger arranged in a working fluid circuit containing a working fluid (e.g., sc-CO2) and having a high pressure side and a low pressure side. The method also includes regulating an amount of working fluid within the working fluid circuit via a mass management system having a working fluid vessel, pumping the working fluid through the working fluid circuit, and expanding the working fluid to generate mechanical energy. The method further includes directing the working fluid away from the expander through the working fluid circuit, controlling a flow of the working fluid in a supercritical state from the high pressure side to the working fluid vessel, and controlling a flow of the working fluid from the working fluid vessel to the low pressure side.