Phase-Change Thermal Engine for Low-Temperature Heat Recovery
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Solution Overview
Problem
Existing heat engine technologies are inefficient when harvesting thermal energy from low-temperature sources due to their reliance on temperature differences between heat sources and sinks, and they do not fully utilize the phase change expansion of materials like Nickel-Titanium alloys.
Innovation Solution
A heat-driven engine utilizing a thermally conductive path and a phase change material with a heat pump that alternates between releasing and absorbing thermal energy to drive the working medium through phase changes, maintaining the medium at optimal temperature ranges for efficient energy conversion, and incorporating a heat spreader to manage heat flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional heat engine technologies are used to harvest thermal energy from low-temperature sources, then the engine can operate with simple design and available components, but the efficiency and power output are low due to reliance on temperature differences
Solution Approach 1:
The patent utilizes phase change materials (such as nickel-titanium alloys) that undergo phase transitions at specific temperatures. When the working medium undergoes phase change, it absorbs or releases latent heat, enabling efficient energy conversion from low-temperature sources without requiring large temperature differences. This directly addresses the efficiency limitation of conventional heat engines.
Solution Approach 2:
The invention changes the operating parameters by using materials with specific phase transformation temperatures matched to the available low-temperature heat source. By selecting phase change materials with transformation temperatures close to the source temperature, the system maximizes energy extraction efficiency while operating with minimal temperature differential.
2Temperature
If phase change materials like nitinol are used in heat engines to utilize low-temperature sources, then the engine can operate at lower temperatures, but the efficiency is reduced and full phase change expansion is not utilized due to inadequate insulation
Solution Approach 1:
The patent divides the heat engine into thermally isolated segments or chambers, each containing phase change materials with specific transformation temperatures. This segmentation allows different parts of the system to operate at different temperature ranges, preventing thermal short-circuits and ensuring that heat flows through the intended phase change materials, thereby maximizing energy utilization.
Solution Approach 2:
The system incorporates thermal insulation and heat management mechanisms that prevent heat loss before it occurs. By designing adequate thermal isolation between hot and cold reservoirs and using phase change materials that capture heat at specific temperatures, the system cushions against thermal energy loss and ensures efficient energy transfer.
3Adaptability or versatility
If existing phase change heat engine designs are used, then low-temperature sources can be utilized, but thermal energy is not efficiently used due to lack of full insulation between heat source and heat sink
Solution Approach 1:
The patent introduces phase change materials as intermediary substances between the heat source and heat sink. These intermediaries absorb heat from the source during phase transition and release it during reverse transition, mediating the heat transfer process and preventing direct thermal short-circuits. This intermediary mechanism ensures that thermal energy is efficiently captured and utilized.
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 solution enhances the efficiency of thermal energy conversion to mechanical energy by eliminating the need for a cold reservoir, recycling thermal energy, and increasing the overall efficiency of the engine, allowing for effective utilization of low-temperature thermal sources.
Implementation Method 1
a working medium of a phase change material, having a low-to-high temperature of transformation and a high-to-low temperature of transformation
Implementation Method 2
causing a phase change and an associated release of thermal energy, to drive the working medium above its low-to-high temperature of transformation
Implementation Method 3
a thermally conductive path into the engine, from a heat source
Implementation Method 4
a heat pump of phase change material positioned adjacent to the working medium. A stimulus is applied to the heat pump, causing a phase change and an associated release of thermal energy
Implementation Method 5
causing the phase change to reverse, and an associated intake of thermal energy, to drive the working medium below its high-to-low temperature of transformation
Data Source
AI summary
A heat-driven engine includes a thermally conductive path into the engine, from a heat source and a working medium of a thermostrictive material, having a first temperature of transformation, positioned adjacent to the thermally conductive path. Also, a heat pump of phase change material is positioned adjacent to the working medium and an actuator is controlled to apply stimulus to the heat pump, causing a phase change and an associated release of thermal energy, to drive the working medium above its low-to-high temperature of transformation and controlled to alternatingly remove the stimulus from the heat pump, causing the phase change to reverse, and an associated intake of thermal energy, to drive the working medium below its high-to-low temperature of transformation. Also, heat flow through the thermally conductive path maintains the working medium at a temperature range permitting the heat pump to drive the working medium temperature, in the manner noted.