Organic Fluid Heat Recovery System with Dual Suction Expanders
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Solution Overview
Problem
Current organic Rankine cycle systems are inefficient in converting low-temperature heat sources into electric energy, particularly below 120°C, and lack compact designs suitable for small-scale applications like vehicles and residences, with no available solutions optimizing electric energy production using a single expander based on varying heat inputs.
Innovation Solution
A closed-loop system with a branch circuit, multiple heat exchangers, an expander, and a control unit that adjusts the flow of organic fluid based on temperature and pressure signals to optimize energy conversion, utilizing a scroll expander and brushless generator for efficient energy generation from multiple heat sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single expander is used for heat recovery, then the system complexity is reduced, but the ability to optimize electric energy production from varying heat inputs is worsened
Solution Approach 1:
The system dynamically switches between two expanders based on heat source temperature. A control unit monitors temperature sensors and activates the appropriate expander (first for low temperature <120°C, second for high temperature ≥120°C), enabling adaptive optimization without permanent system complexity
Solution Approach 2:
The system employs two expanders with different operational characteristics - a first expander optimized for low-temperature heat sources and a second expander for high-temperature sources. Both expanders connect to the same organic fluid circuit, allowing the system to universally handle varying heat inputs while maintaining optimized performance across different temperature ranges
2Ease of operation
If small size systems are designed for vehicle installation, then the ease of installation is improved, but the electric power generation capacity is worsened
Solution Approach 1:
The ORC system is designed as a compact integrated unit that can be nested within the vehicle's existing engine bay or utility space. The closed circuit components (heat exchangers, expanders, condenser, pump) are arranged in a space-efficient configuration, allowing the system to fit within constrained vehicle dimensions while maintaining functional integrity
Solution Approach 2:
The system combines multiple heat recovery functions into a single integrated ORC unit. The first and second heat exchangers can process different heat sources (exhaust gases and cooling liquid) simultaneously, merging heat recovery streams into one organic fluid circuit that drives the expanders, thereby maximizing power density within a compact footprint
3Adaptability or versatility
If heat sources below 120°C are utilized, then the adaptability to low-temperature sources is improved, but the conversion efficiency is worsened
Solution Approach 1:
The system applies different expander characteristics to different temperature ranges. The first expander is specifically designed with properties optimized for low-temperature heat sources (<120°C), while the second expander is optimized for high-temperature sources (≥120°C). This local optimization ensures maximum conversion efficiency for each temperature regime
Solution Approach 2:
The system changes operational parameters by switching between two expanders with different characteristics. When heat source temperature drops below 120°C, the control unit activates the first expander which has parameters (such as expansion ratio, speed, and mechanical design) specifically tuned for low-temperature operation, thereby maintaining acceptable conversion efficiency across varying thermal conditions
Data Source
Figure 1~2
Figure 3
Figure 4A~4D
AI summary
System (1) for converting heat energy into electric energy comprising: a closed main circuit (2) in which flows an organic fluid; a first heat exchanger (3) thermally coupled to a first energy source (4) through a first circuit (28); said first heat exchanger (3) being positioned along the main circuit (2) for heating the organic fluid; an expander (5) comprising at least a first and second suction inlets (6,7) and one discharge outlet (8); an electric generator (33) mechanically coupled to an output shaft of the expander (5); a condenser (9) positioned along the main circuit (2) and fluidly connected to the discharge outlet (8) of the expander (5) and to a tank (10), said condenser (9) being configured to condense the organic fluid exiting from the expander (5); a first pump (11) positioned along the main circuit (2) between the tank (10) and the first heat exchanger (3); a second heat exchanger (12) thermally coupled to a second energy source (13) through a second circuit (24); said second heat exchanger (3) being positioned along the main circuit (2) between the first heat exchanger (3) and the first suction inlet (6) of the expander (5) for heating the organic fluid; a branch (2') of the main circuit (2) fluidly connecting a point of the main circuit (2) arranged between the first and second exchangers (3,12) to the second suction inlet (7) of the expander (2) so to bypass the second exchanger (12); at least a valve (14,15,16) configured to divert the organic fluid towards the first suction inlet (6) of the expander (5) or towards the second suction inlet (7) of the expander (5); a first temperature sensor (25) arranged along the first circuit (28) upstream the first heat exchanger (3) configured to output a first temperature signal (T1); a second temperature sensor (26) arranged along the first circuit (28) downstream the first heat exchanger (3) configured to output a second temperature signal (T2); a third temperature sensor (29) arranged along the second circuit (24) upstream the second heat exchanger (12) configured to output a third temperature signal (T3); a fourth temperature sensor (30) arranged along the second circuit (24) downstream the second heat exchanger (12) configured to output a fourth temperature signal (T4); a control unit (21) configured to receive said first, second, third and fourth temperature signals (T1,T2,T3,T4) to generate a first pump control signal (PS) and a first valve control signal (VS) based on said first, second, third and fourth temperature signals (T1,T2,T3,T4) to operate the first pump (11) and the at least a valve (14,15,16); wherein the expander (5) being configured to expand the organic fluid vaporized in said first heat exchanger (3) or in said first and second heat exchangers (3,12) to generate mechanical energy for driving the electric generator (33). Vehicle (100) comprising said system (1) for converting heat energy in electric energy.