Compact indirect evaporative cooler
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Solution Overview
Problem
Conventional indirect evaporative coolers and heat exchangers are bulky due to the need for increased turbulence to enhance heat transfer, which leads to higher pressure drops and power consumption, making them inefficient and large in size.
Innovation Solution
The design employs narrower plate spacing and shorter passage lengths to achieve laminar airflow with high shear rates, reducing the insulating effect of air and minimizing flow resistance, resulting in a compact and efficient heat exchanger core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If turbulence is increased to enhance heat transfer, then heat transfer efficiency is improved, but pressure drop increases and power consumption increases
Solution Approach 1:
The invention changes the flow regime parameter from turbulent to laminar flow. By operating in the laminar flow regime with high shear rates, the system achieves enhanced heat transfer without the excessive pressure drops associated with turbulence. This parameter change resolves the contradiction by finding an alternative operational state that provides heat transfer enhancement through different mechanisms (shear-driven) rather than turbulence-driven convection.
Solution Approach 2:
The invention inverts the conventional approach by using laminar flow instead of turbulent flow for heat transfer enhancement. Rather than accepting turbulence as the only means to improve heat transfer, the patent explores the opposite flow regime and discovers that laminar flow with high shear rates can achieve superior heat transfer efficiency with lower energy consumption, thus inverting the traditional wisdom.
2Stress or pressure
If plate spacing is increased to reduce pressure drop, then flow resistance is reduced, but heat transfer efficiency decreases
Solution Approach 1:
The invention changes the governing parameter for heat transfer from turbulence intensity to shear rate. By maintaining narrow plate spacing to preserve high shear rates in laminar flow, the system achieves both low pressure drops and high heat transfer efficiency. The parameter change allows the system to operate in a regime where shear-driven heat transfer dominates, resolving the trade-off between pressure drop and heat transfer efficiency.
3Productivity
If passage length is increased to improve heat transfer, then cooling capacity increases, but device size increases
Solution Approach 1:
The invention changes the dominant heat transfer mechanism from convection-driven (in long passages) to shear-driven (in short passages with laminar flow). By operating in the laminar regime with high shear rates, the system achieves rapid heat transfer that allows for much shorter passage lengths while maintaining or improving cooling capacity. This parameter change enables compact device design without sacrificing performance.
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 allows for a significant reduction in the size of the heat exchanger core to about 20% of conventional lengths while maintaining acceptable pressure drops and enhancing heat transfer efficiency, reducing energy consumption and system bulk.
Implementation Method 1
In the wet passages a 'working' airstream passes over wetted surfaces, accepting and carrying away sensible heat as well as latent heat of evaporation, leaving evaporatively cooled wet surfaces
Implementation Method 2
In the dry passages an initially warm airstream is cooled as heat is transferred by convective transfer from the airstream to the cooled plate surfaces and by conductive heat transfer through the plates
Implementation Method 3
heat is transferred by convective transfer from the airstream to the cooled plate surfaces and by conductive heat transfer through the plates
Implementation Method 4
The temperature gradient between the airstreams on either side of the thin plates drives the flow of heat from dry passage side to wet passage side
Implementation Method 5
As the outgoing warm humid air passes adjacent to the cold incoming air, the water vapor in the outgoing air condenses, evolving heat of condensation (equal to the heat of vaporization consumed in cooling), and transferring sensible heat across the metal plates to warm the incoming air in the dry passages
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An indirect evaporative cooling system with a core greatly reduced in size compared to conventional evaporative cooling systems The system has a heat exchanger core having heat exchange plates defining a plurality of wet air flow passages and a plurality of dry air flow passages. At least one fan drives air through the passages. The dry air passages have a small height and a short length, configured so that a substantially laminar airflow having a raised shear rate arises in the dry air passages, and so that a back pressure across a length of the dry air passages remains low.