Counter current heat exchange module
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Solution Overview
Problem
Existing heat exchange systems for air streams, such as evaporative coolers, face limitations in achieving efficient heat transfer and humidity control, often resulting in excessive humidity and suboptimal cooling performance due to cross-flow configurations and lack of mass transfer prevention.
Innovation Solution
A counter-current heat exchange apparatus using a stack of thermally conductive sheets with corrugated surfaces, where alternate sheets are angled to create separate pathways for gas flows, preventing mass transfer and enhancing heat transfer efficiency by minimizing laminar flow and boundary layer thickness, and allowing for different wetting fluids in each pathway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cross-flow configuration is used in evaporative coolers, then cooling performance is achieved, but excessive humidity is created in the air stream
Solution Approach 1:
The heat exchange process is segmented into two separate pathways: a dry pathway for the primary air stream and a wet pathway for the secondary air stream. This segmentation prevents direct mass transfer (humidification) of the primary air stream while still enabling heat exchange, thus achieving cooling without excessive humidity creation.
Solution Approach 2:
The harmful mass transfer component is extracted from the heat exchange process. By using moisture impervious sheets, the patent separates the heat transfer function from the mass transfer function, allowing heat exchange to occur without the unwanted humidification effect that plagues conventional evaporative coolers.
2Temperature
If multi-stage wetted wicks are used to reduce temperature, then cooling is achieved, but the device complexity increases
Solution Approach 1:
Multiple functions are merged into a single component. The corrugated sheets simultaneously provide structural support, create turbulent flow patterns, enable heat transfer, and prevent mass transfer. This integration eliminates the need for multiple separate components like spaced parallel wetted wicks, reducing overall device complexity while maintaining cooling performance.
Solution Approach 2:
The corrugated (curved) surface geometry of the sheets serves multiple purposes: it creates turbulence to enhance heat transfer, provides structural rigidity, and maintains the separation between dry and wet pathways. This geometric feature replaces complex multi-stage mechanisms with a simpler curved surface design.
3Power
If counter-flow configuration is implemented, then heat transfer efficiency is improved, but mass transfer prevention becomes difficult
Solution Approach 1:
A moisture impervious sheet acts as an intermediary barrier between the dry and wet air streams. This intermediary maintains the counter-flow configuration for efficient heat transfer while physically preventing mass transfer (humidification) of the primary air stream, thus resolving the contradiction between heat transfer efficiency and mass transfer prevention.
Solution Approach 2:
The use of thermally conductive yet moisture impervious composite materials enables simultaneous achievement of efficient heat transfer and mass transfer prevention. These composite sheets combine thermal conductivity properties with moisture resistance, allowing counter-flow heat exchange without unwanted humidification.
4Loss of energy
If laminar flow is present in heat exchange pathways, then flow resistance is reduced, but heat transfer efficiency decreases
Solution Approach 1:
The corrugated (curved) surface geometry intentionally induces turbulent flow rather than laminar flow. The curved surfaces create flow separation and mixing that enhances heat transfer efficiency. The patent accepts the associated increase in flow resistance as a necessary trade-off to achieve superior heat transfer performance.
Solution Approach 2:
The corrugated structure creates periodic flow disturbances and turbulence that enhance convective heat transfer. These mechanical flow disturbances, while increasing energy loss slightly, dramatically improve heat transfer efficiency by preventing boundary layer formation and enhancing mixing.
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 configuration achieves efficient heat transfer between air streams with reduced humidity in one stream and improved cooling performance, approaching theoretical maximum heat exchange efficiency while maintaining dryness in one air stream, and enabling simultaneous evaporation and condensation processes.
Implementation Method 1
The corrugations provide heat transfer between the first and second gas flows such that a temperature change in one of the first and second gas flows causes heat transfer to the other of the first and second gas flows
Implementation Method 2
Evaporative coolers wherein the temperature of an air stream is reduced by the evaporation of water
Implementation Method 3
a plurality of laminated plates formed in a mesh type to increase air turbulence in its cross flow configuration
Data Source
AI summary
Heat exchange apparatus comprises a plurality of thermally conductive, moisture impervious sheets. Each sheet comprises a plurality of corrugations. The plurality of sheets are disposed in a stack such that each alternate sheet has its corrugations affixed to and disposed at an angle to the corrugations of an adjacent sheet to provide a plurality of separate flow pathways. The plurality of separate flow pathways comprises first predetermined pathways and second predetermined pathways. The stack of sheets have first end portions disposed to provide a first inlets and a first outlets for the first predetermined pathways and second end portions to provide second inlets and second outlets for the second predetermined pathways. The corrugations forming the second predetermined pathways comprise a wettable surface. The first predetermined pathways are adapted for a first fluid flow and the second predetermined pathways are adapted for a countercurrent second fluid flow.