Methods and systems for turbulent, corrosion resistant heat exchangers
Solution Overview
Problem
Conventional liquid desiccant systems for dehumidification and cooling face challenges such as high energy costs, corrosion issues, and inefficiencies due to the use of corrosive brines and packed bed designs, which lead to desiccant carry-over and increased energy consumption.
Innovation Solution
A system utilizing a microporous membrane with a liquid desiccant flowing as a falling film, combined with a turbulator to induce turbulence in the air stream and a thermally conductive support plate, which prevents desiccant carry-over and enhances heat and moisture transfer, while using a corrosion-resistant and cost-effective design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional packed bed designs are used for liquid desiccant dehumidification, then dehumidification can occur, but desiccant carry-over increases and energy consumption rises due to high air resistance
Solution Approach 1:
The patent uses a microporous membrane as the contact medium between liquid desiccant and air stream. The membrane's porous structure allows water vapor to pass through while retaining the liquid desiccant, eliminating carry-over issues inherent in packed bed designs. The membrane provides a controlled interface that prevents desiccant particles from entering the air stream while maintaining effective dehumidification.
Solution Approach 2:
The patent employs a falling film liquid distribution system where liquid desiccant flows down the membrane surface under gravity. This hydraulic approach ensures uniform desiccant distribution across the membrane while maintaining laminar flow conditions that prevent carry-over. The controlled fluid dynamics optimize mass transfer without the turbulence and particle generation associated with packed beds.
2Productivity
If turbulent flow is used to enhance heat and moisture transfer, then transfer rates increase, but desiccant carry-over risk increases
Solution Approach 1:
The microporous membrane acts as a physical barrier that allows vapor-phase mass transfer while blocking liquid-phase desiccant carry-over. The membrane's pore structure enables high transfer rates through capillary action and concentration gradients while maintaining laminar liquid flow on the membrane surface, thus achieving high productivity without carry-over.
Solution Approach 2:
The patent creates different flow regimes in different zones: laminar flow of liquid desiccant along the membrane surface to prevent carry-over, and turbulent mixing in the air stream to enhance mass transfer. The membrane interface locally separates these requirements, allowing high transfer rates without compromising liquid flow stability.
3Productivity
If corrosive brines like LiCl, LiBr, or CaCl2 are used for dehumidification, then dehumidification efficiency improves, but corrosion of system components increases
Solution Approach 1:
The microporous membrane serves as a corrosion barrier, allowing the use of highly efficient corrosive brines like LiCl and LiBr in the liquid desiccant stream while preventing contact with metal components. The membrane isolates the corrosive liquid from the structural framework, heat exchanger surfaces, and other metallic parts, enabling high dehumidification efficiency without corrosion damage.
Solution Approach 2:
The membrane acts as an intermediary barrier between the corrosive liquid desiccant and the system's structural components. It allows the beneficial corrosive brines to be used for their superior dehumidification performance while the membrane protects all metal parts from exposure, effectively decoupling the liquid choice from corrosion constraints.
4Ease of manufacture
If open desiccant systems with direct air-desiccant contact are used, then system cost is reduced, but desiccant carry-over risk and energy consumption increase
Solution Approach 1:
The microporous membrane enables an open system configuration where liquid desiccant and air directly contact through the membrane, eliminating the need for expensive closed vacuum vessels. The membrane's selective permeability allows vapor transfer while preventing liquid carry-over, providing a low-cost open system solution that avoids the harmful effects of traditional packed beds.
Solution Approach 2:
The membrane serves as a simple, inexpensive intermediary that enables direct contact between air and desiccant without requiring complex closed systems. It provides the necessary separation function at low cost, allowing open system operation with minimal equipment while preventing carry-over that would otherwise require expensive containment and separation systems.
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
The system efficiently dehumidifies and cools air streams while preventing desiccant contamination, reducing energy consumption and maintenance costs, and is manufactured using inexpensive, corrosion-resistant materials.
Implementation Method 1
a microporous membrane with a liquid desiccant flowing as a falling film
Implementation Method 2
liquid desiccant systems have been used for many years and are generally quite efficient at removing moisture from the air stream
Implementation Method 3
combined with a turbulator to induce turbulence in the air stream
Implementation Method 4
liquid desiccant systems have been used for many years and are generally quite efficient at removing moisture from the air stream
Implementation Method 5
a thermally conductive support plate, which prevents desiccant carry-over and enhances heat and moisture transfer
Implementation Method 6
Such heat exchangers can use gravity induced pressures (siphoning) to keep the micro-porous membranes properly attached to the heat exchanger structure
Data Source
AI summary
Disclosed are various turbulent, corrosion-resistant heat exchangers used in desiccant air conditioning systems.