Serial Expander Power System for Waste Heat Recovery
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Solution Overview
Problem
Existing power systems fail to efficiently convert waste heat into useful mechanical or electrical power, particularly in industrial processes like gas turbines and gas engines, where high-temperature exhaust gases contain significant thermal energy that is often lost.
Innovation Solution
A power system utilizing a working fluid circuit with serially arranged expanders and a pump, where the first expander drives the pump and the second expander generates power for a load, with a regulating valve to adjust back pressure and a bypass valve to manage available waste heat, enabling efficient conversion of waste heat into mechanical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If waste heat is converted into useful power using traditional heat engine systems with single expanders, then power generation is achieved, but the conversion efficiency is insufficient and significant thermal energy is lost
Solution Approach 1:
The patent divides the expansion process into two separate stages using two expanders in series. The first expander handles the high-pressure to intermediate-pressure expansion, while the second expander handles the intermediate-pressure to low-pressure expansion. This segmentation allows each expander to operate at optimal pressure ratios, improving the overall efficiency of waste heat conversion and reducing energy loss.
Solution Approach 2:
The patent changes the pressure parameters through the two-stage expansion process. By introducing an intermediate pressure stage between the two expanders, the system optimizes the pressure drop across each expander, enabling more efficient extraction of mechanical work from the waste heat and improving overall power conversion efficiency.
2Productivity
If multiple expanders and pumps are added to improve power conversion efficiency, then waste heat utilization improves, but the device complexity increases
Solution Approach 1:
The patent merges the function of driving the pump with power generation by using the first expander to simultaneously drive the pump and generate useful power. This integration reduces the need for separate driving mechanisms and simplifies the overall system structure while maintaining high power conversion efficiency.
Solution Approach 2:
The first expander serves multiple functions: it expands the working fluid from high to intermediate pressure, drives the pump to maintain system circulation, and generates useful mechanical power. This multi-functionality reduces the number of separate components needed, thereby reducing device complexity while improving efficiency.
3Productivity
If serially arranged expanders are used to improve efficiency, then waste heat conversion improves, but the back pressure control and fluid management complexity increases
Solution Approach 1:
The patent introduces a back pressure control valve as an intermediary device between the two expanders. This valve actively regulates the intermediate pressure, ensuring optimal operation of both expanders while simplifying the control of back pressure. The valve acts as a mediator that manages the fluid flow and pressure transitions, making the system easier to operate despite the increased complexity of having two expanders in series.
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 enhances the overall efficiency of power conversion by directly driving a pump or compressor and reducing the number of electric machines, thereby improving efficiency and reducing costs while effectively utilizing waste heat.
Implementation Method 1
a heater configured to circulate the working fluid in heat exchange relationship with a hot fluid to vaporize the working fluid
Implementation Method 2
vaporize the working fluid
Implementation Method 3
serially arranged first expander and second expander fluidly coupled to the working fluid circuit and disposed between the high pressure side and the low pressure side, configured to expand working fluid flowing therethrough and generating mechanical power therewith
Implementation Method 4
A pump is fluidly coupled to the working fluid circuit between the low pressure side and the high pressure side, configured to rise the pressure of the working fluid in the working fluid circuit
Implementation Method 5
a cooler fluidly coupled to and in thermal communication with the low pressure side of the working fluid circuit and arranged and configured to remove heat from the working fluid in the low pressure side of the working fluid circuit
Data Source
Figure 1
Figure 2
AI summary
The power system comprises a working fluid circuit (2) having a high pressure side (2A) and a low pressure side (2B) and configured to flow a working fluid therethrough. The working fluid circuit (2) further comprises a heater (7) configured to circulate the working fluid in heat exchange relationship with a hot fluid to vaporize the working fluid. The system further comprises serially arranged first expander (9) and second expander (11) fluidly coupled to the working fluid circuit and disposed between the high pressure side and the low pressure side thereof. One of the expanders drives a load (37) and the other expander drives a pump or compressor (33) fluidly coupled to the working fluid circuit (2) between the low pressure side (2B) and the high pressure side (2A) thereof. A cooler (29) is further arranged and configured to remove heat from the working fluid in the low pressure side (2B) of the working fluid circuit (2).