Waste Heat Recovery Cycle With Passive Working Fluid Mass Control
Find Innovative SolutionsGenerate Solutions
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 small flow rate and low temperature thermal sources.
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
1Power
If steam-based Rankine cycle is used for waste heat recovery, then power generation capability is improved, but equipment cost and operational complexity 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 waste heat sources while avoiding the complexity of multi-pressure steam systems. The organic working fluid enables single-pressure cycle operation that is simpler and more cost-effective for low-to-moderate temperature applications.
Solution Approach 2:
The patent employs simpler, less expensive equipment components suitable for organic Rankine cycle systems compared to complex steam turbine systems. The expander can be a simpler device rather than a complex steam turbine, and the heat exchangers can be designed for lower pressure and temperature conditions, reducing overall equipment cost and complexity while maintaining power generation capability.
2Power
If steam-based Rankine cycle is used for low temperature waste heat sources, then power generation efficiency decreases, but the system requires high temperature sources (600°F or higher)
Solution Approach 1:
The patent fundamentally changes the working fluid parameters from water/steam to organic fluids with lower saturation temperatures. This allows the cycle to match lower temperature waste heat sources (ranging from 100°F to 500°F) effectively. The organic working fluids have thermodynamic properties optimized for lower temperature operation, enabling efficient heat transfer and expansion without requiring the high 600°F+ temperatures needed for conventional steam cycles.
Solution Approach 2:
The patent utilizes phase transition of organic working fluids at lower temperatures to drive the expansion process. The organic fluid evaporates at lower temperatures in the heat exchanger and then expands through the expander, converting thermal energy to mechanical work. This phase transition mechanism works efficiently at lower temperatures compared to steam-based systems, enabling power generation from low-temperature waste heat sources.
3Power
If steam-based Rankine cycle is used for small flow rate heat sources, then heat capture capability is insufficient, but the system requires large mass flow
Solution Approach 1:
The patent changes the working fluid to organic substances with higher heat of vaporization relative to their mass flow requirements. This allows the system to capture sufficient heat energy from small flow rate sources. The organic working fluids can achieve the necessary energy transfer with lower mass flow rates compared to water/steam systems, making the system suitable for small-to-medium sized waste heat sources that would be inadequate for conventional steam cycles.
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 waste heat recovery system, method and device executes a thermodynamic cycle using a working fluid in a working fluid circuit which has a high pressure side and a low pressure side. Components of the system in the working fluid circuit include 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 in the working fluid circuit, 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, 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, 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, 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, and a mass management system connected to the working fluid circuit, the mass management system, method and device having a working fluid vessel connected to the low pressure side of the working fluid circuit and configured to passively control an amount of working fluid mass in the working fluid circuit.