Counter-Current Heat Exchange in Alternating-Flow Thermal Circuits
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Solution Overview
Problem
Thermal devices with alternating primary fluid circulation suffer from inefficient heat exchange due to changes in direction, leading to counter-current or co-current heat exchange, which reduces efficiency, especially in magnetocaloric devices where frequency increases heat transfer but also shortens exchange time, resulting in reduced thermal power delivery.
Innovation Solution
A thermal device design with unidirectional counter-current heat exchange zones, where the primary and secondary fluids move in opposite directions, and a control mechanism to ensure continuous unidirectional flow in a common primary circuit portion, optimizing energy transfer and reducing pressure drops and device volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the primary fluid is moved in an alternating motion to establish a thermal gradient in magnetocaloric materials, then the temperature gradient is improved, but the heat exchange efficiency with the secondary fluid deteriorates due to counter-current and co-current flow patterns
Solution Approach 1:
The primary circuit is divided into at least two unidirectional primary circuit portions at division points located at the outlet of the apparatus core. This segmentation allows the primary fluid to flow in opposite directions in different portions while maintaining unidirectional flow in each portion, enabling counter-current heat exchange in each segment while preserving the overall alternating motion needed for thermal gradient establishment.
Solution Approach 2:
The invention introduces dynamic flow direction control through devices for controlling the direction of circulation of the primary fluid in each unidirectional portion. These devices force unidirectional movement of the primary fluid in each portion while allowing the overall system to alternate between different flow patterns, adapting the heat exchange mode dynamically to maintain efficiency.
2Power
If the frequency of changes in flow direction is increased to deliver more thermal power, then the thermal power delivery is improved, but the heat exchange efficiency deteriorates due to reduced exchange time
Solution Approach 1:
The unidirectional primary circuit portions with counter-current heat exchange ensure continuous and efficient heat transfer between primary and secondary fluids during each phase of the alternating cycle. By maintaining unidirectional flow in each portion and optimizing the heat exchange interface, the system maximizes the useful heat exchange action during the limited time available at each frequency cycle.
3Temperature
If the primary fluid circulates back and forth through channels to exchange heat with magnetocaloric material, then the thermal gradient is established, but the temperature averaging in heat exchangers occurs leading to efficiency loss
Solution Approach 1:
By segmenting the primary circuit into distinct unidirectional portions with controlled flow directions, the invention prevents the temperature averaging that occurs in traditional back-and-forth circulation. Each segment maintains a specific flow direction and temperature profile, allowing the heat exchangers to operate with optimized temperature differences throughout the cycle.
Solution Approach 2:
The dynamic control of flow direction in each unidirectional portion allows the system to adapt the temperature profiles in different circuit segments to match the thermal needs of the magnetocaloric materials, maintaining optimal heat exchange efficiency throughout the alternating cycle.
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 design enhances heat exchange efficiency and capacity, allowing for better temperature convergence and increased thermal power delivery while reducing energy losses and device size.
Implementation Method 1
These thermal devices exploit the magnetocaloric effect (MCE) of certain materials, which consists of a change in their temperature when subjected to a magnetic field.
Implementation Method 2
at least one heat exchange interface of the primary fluid with a secondary fluid circulating unidirectionally in a secondary circuit
Data Source
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AI summary
The present invention concerns a thermal apparatus (1) comprising at least one primary circuit (P1) in which a heat transfer fluid referred to as the primary fluid is displaced by a drive device with an alternating motion, and at least one heat exchanging interface (I1.1, I1.2) between the primary fluid and a secondary fluid flowing unidirectionally in a secondary circuit (S1.1, S1.2), said apparatus being characterised in that said interface (l1.1, I1.2) comprises at least one heat exchange area (ZN, ZN+1, Z'N, Z'N+1) in which the primary fluid and the secondary fluid move unidirectionally and countercurrent relative to each other.