Solid State Thermodynamic Cycle
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Solution Overview
Problem
Existing elastocaloric thermodynamic cycles face inefficiencies due to uncontrolled martensitic volume changes during heat recovery processes, leading to increased thermal loads and reduced COP, as they assume full phase changes that are not achievable in real materials.
Innovation Solution
A method to maintain constant martensite volume by controlling stress during thermodynamic cycles, using isothermal and polytropic processes to manage stress and temperature changes, reducing work input and enhancing COP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If full phase change from austenite to martensite is assumed in elastocaloric thermodynamic cycles, then the cycle can be modeled using traditional gas cycles (reverse Brayton and reverse Stirling), but the martensitic volume changes uncontrolled during heat recovery processes, leading to increased thermal loads and reduced COP
Solution Approach 1:
The patent changes the thermodynamic parameters during heat recovery processes by applying controlled stress variations. Instead of maintaining constant volume (isochoric) or constant pressure (isobaric) conditions, the system dynamically adjusts stress to maintain constant martensitic volume fraction, transforming the heat recovery processes into a new type of controlled thermodynamic process that eliminates uncontrolled volume changes and associated energy losses
Solution Approach 2:
The patent introduces dynamic stress control during heat recovery processes. The stress applied to the elastocaloric material is continuously adjusted based on temperature changes to maintain constant martensitic volume fraction. This dynamic control mechanism prevents the uncontrolled martensitic volume changes that occur in traditional cycles, thereby reducing thermal loads and improving COP
2Power
If stress is increased to achieve desired stress value or full phase transition, then heat rejection and absorption can be achieved, but martensitic volume increases during heat recovery, causing further heat rejection and increasing thermal loads
Solution Approach 1:
The patent implements a feedback control mechanism where the stress applied to the elastocaloric material is continuously adjusted based on the martensitic volume fraction. During heat recovery processes, the system monitors temperature and stress changes and dynamically modifies the applied stress to maintain constant martensitic volume fraction. This feedback loop prevents the runaway effect where increased stress leads to increased martensitic volume, which in turn causes excessive heat rejection and thermal load
3Ease of manufacture
If isochoric or constant material volume processes are used for heat recovery, then the cycle follows traditional Stirling cycle methodology, but the martensitic volume changes with temperature, creating process imbalance and requiring higher thermal load handling
Solution Approach 1:
The patent fundamentally changes the parameter control strategy for heat recovery processes. Instead of maintaining constant volume (isochoric) conditions as in traditional Stirling cycles, the system maintains constant martensitic volume fraction by dynamically adjusting both stress and volume parameters. This parameter transformation eliminates the process imbalance inherent in isochoric processes where martensitic volume naturally changes with temperature, thereby improving heat recovery efficiency and reducing energy losses
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 method increases the COP by 25% and reduces material hysteresis, making elastocaloric technology more efficient and cost-effective for heating and cooling applications.
Implementation Method 1
The EC cycle takes advantage of the superelastic behaviour of Shape Memory Alloys (SMAs), which facilitates, through cyclic uniaxial loading and unloading, the absorption of heat from a low temperature source and its rejection to a higher temperature sink.
Implementation Method 2
heat rejection and heat absorption are isothermal processes
Implementation Method 3
the heat recovery processes which preheat and precool the SMA are isochoric or constant material volume processes
Data Source
AI summary
Disclosed is a method for implementing a thermodynamic cycle for an elastocaloric material. The method includes increasing a stress applied on the elastocaloric material, till the stress reaches a desired stress value or the elastocaloric material transitions from austenite to martensite form, decreasing a temperature of the elastocaloric material from high to low value, and decreasing a stress of the elastocaloric material to maintain a constant volume fraction of corresponding martensite form during temperature decrease, decreasing the stress of the elastocaloric material, till the stress reaches a minimum stress value or the elastocaloric material transitions from martensite to austenite form and increasing the temperature of the elastocaloric material from low to high value, and increasing the stress of the elastocaloric material to maintain a constant volume fraction of corresponding martensite form during temperature increase.