Electrocaloric Counter-Flow Heat Transfer for Large Temperature Lift
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Solution Overview
Problem
Current electrocaloric refrigeration systems suffer from large heat transfer losses and limited temperature differences between heat source and sink, making them non-competitive with vapor-compression technology due to the need for multiple cascades to achieve significant temperature differences.
Innovation Solution
The system employs electrocaloric materials in combination with a working fluid in counter flow, using thermal diodes or switches for selective heat transfer between the electrocaloric material and the fluid streams, allowing heat to be transported from the electrocaloric material to a first fluid stream when it is hotter and from a second fluid stream to the electrocaloric material when it is cooler, thereby establishing a net flow of heat energy from the heat source to the heat sink.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If multiple cascades of electrocaloric materials are used to increase temperature difference, then the temperature difference between heat source and sink is improved, but heat transfer losses increase significantly
Solution Approach 1:
The system divides the heat transfer process into two separate convective streams that operate in counter-flow, with each stream handling a portion of the temperature difference. This segmentation allows heat transfer to occur at smaller temperature gradients across each individual heat exchanger, reducing overall heat transfer losses while achieving the required total temperature difference between heat source and sink.
Solution Approach 2:
The patent introduces a working fluid as an intermediary medium that carries heat between the electrocaloric material and the external heat source/sink. The working fluid in counter-flow configuration acts as a mediator, enabling efficient heat transfer with reduced thermal losses compared to direct cascade connections of electrocaloric materials.
2Device complexity
If a single stage electrocaloric device is used, then device complexity is reduced, but the temperature difference produced is insufficient
Solution Approach 1:
The patent employs hydraulic principles by using a working fluid flowing through conduits in counter-flow configuration. This fluid-based heat transfer mechanism enables a single-stage device to achieve large temperature differences by utilizing the convective heat transfer properties of the working fluid, avoiding the need for multiple cascaded electrocaloric stages.
Solution Approach 2:
The invention transitions from a direct thermal coupling approach (one-dimensional heat transfer through cascaded materials) to a counter-flow convective heat transfer system (introducing a fluid dimension). This dimensional change allows heat transfer to occur along the length of the conduits with continuous temperature gradients, enabling large temperature differences in a single stage.
3Loss of energy
If electrocaloric materials are directly coupled to heat source and sink, then heat transfer efficiency is improved, but the system cannot achieve regenerative heat transfer
Solution Approach 1:
The system implements periodic action through the cyclic operation of the electrocaloric material (heating and cooling cycles) combined with continuous counter-flow of the working fluid. This periodic modulation of the electrocaloric material's temperature, coupled with the continuous fluid flow, enables regenerative heat transfer where heat is continuously extracted from the hot stream and delivered to the cold stream, improving both efficiency and productivity.
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 approach enables the establishment of large temperature differences between the heat source and sink, improving the efficiency and competitiveness of electrocaloric energy conversion systems by reducing energy losses and enhancing regenerative heat transfer.
Implementation Method 1
ECM s react to changes in the strength of an electric field, to which they are exposed, by changing their temperature. ECM s increase in temperature upon increase of the electric field and they decrease in temperature upon reduction (or removal) of the applied field.
Implementation Method 2
a first convective stream of working fluid flowing towards said heat sink; a second convective stream of said fluid flowing towards said heat source
Implementation Method 3
means for allowing transport of heat (preferably selective transport of heat) from said ECM to said first convective stream, when the ECM is at a higher temperature than the temperature of said first convective stream
Data Source
AI summary
The present invention lies in the field of electrocaloric energy conversion. More specifically, the present invention relates to improvements in systems and methods which employ electrocaloric materials as a source of temperature variation in electrocaloric refrigeration processes. Even more specifically, the present invention relates to the application of electrocaloric materials in combination with a working fluid communicating with a heat source and a heat sink in counter flow.