Engineered Packing Sheets for High Heat Transfer at Low Pressure Drop
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Solution Overview
Problem
Existing heat exchangers face challenges in achieving high heat transfer coefficients and low pressure drops at low superficial velocities, particularly in applications requiring less expensive materials and increased geometric surface area for enhanced chemical reactions.
Innovation Solution
The apparatus features sheets oriented at an angle of at least 10 degrees relative to the heat transfer surface, with tabs forming channels that direct fluid flow to impinge the surface, and includes additional sheets with similar configurations to enhance heat transfer, manufactured using computational fluid dynamics and finite element analysis for efficient and cost-effective production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If extended surfaces are used to increase heat transfer area, then heat transfer efficiency is improved, but manufacturing cost increases due to requirement of high thermal conductivity materials like copper, aluminum or noble metals
Solution Approach 1:
The invention changes the geometric parameters of the heat transfer surface by creating micro-scale protrusions and recesses (extending 10-90 micrometers from the surface) that increase the effective heat transfer area by 10-100% without requiring high-cost materials. This parameter change allows achieving high heat transfer efficiency with conventional, lower-cost materials.
Solution Approach 2:
The invention creates a micro-porous structure on the heat transfer surface through controlled protrusions and recesses, increasing the effective surface area available for heat transfer. This porous-like structure enhances heat transfer efficiency without requiring the use of expensive high thermal conductivity materials.
2Temperature
If flow velocity is increased to improve heat transfer coefficient, then Nusselt number increases, but pressure drop increases proportionally more
Solution Approach 1:
The invention changes the flow regime parameters by creating micro-scale surface features that induce local turbulence and disrupt boundary layers at lower flow velocities. This allows achieving high Nusselt numbers without the need for high flow velocities that would cause excessive pressure drops.
Solution Approach 2:
The invention adds a micro-scale dimension (10-90 micrometer protrusions and recesses) to the heat transfer surface, creating three-dimensional flow patterns that enhance heat transfer. This dimensional change allows effective heat transfer at lower macro-scale flow velocities, reducing pressure drop.
3Area of stationary object
If micro-scale protrusions and recesses are added to increase heat transfer area, then effective surface area increases, but manufacturing complexity increases
Solution Approach 1:
The invention replaces complex mechanical machining processes with a chemical etching process to create the micro-scale protrusions and recesses. This substitution of mechanical manufacturing with chemical processing simplifies production and reduces manufacturing complexity while achieving the desired micro-structure.
Solution Approach 2:
The invention uses controlled chemical etching parameters (etchant concentration, etching time, temperature) to precisely control the depth and distribution of micro-protrusions and recesses. By changing these process parameters, the effective heat transfer area can be adjusted without requiring complex manufacturing equipment or procedures.
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 achieves high Nusselt numbers at low superficial velocities and low pressure drops, allowing for more efficient heat transfer and increased geometric surface area, beneficial for chemical reactions in catalytic reactors, while being easier and less expensive to manufacture.
Implementation Method 1
the plurality of tabs collectively form channels directing a fluid passing from the inlet to the outlet to impinge the heat transfer surface
Implementation Method 2
apparatus providing enhanced heat transfer... directing a fluid passing from the inlet to the outlet to impinge the heat transfer surface
Data Source
Figure 1A~2B
Figure 3A~4B
Figure 5A~6B
AI summary
An apparatus includes an inlet, an outlet, and a sheet disposed proximate a heat transfer surface, the sheet being oriented in a sheet plane that is displaced from a plane of the heat transfer surface by an angle of at least 10 degrees. The apparatus also includes a plurality of tabs attached to the sheet, the tabs lying in respective tab planes, wherein the tab planes and the sheet plane intersect forming respective intersections, the intersections of the tab planes and the sheet plane are substantially parallel, the intersections of the tab planes and the sheet plane are at an angle of less than 88o to the heat transfer surface, and the plurality of tabs collectively form channels directing a fluid passing from the inlet to the outlet to impinge the heat transfer surface.