Membrane Absorption Heater Layout for Compact LiBr Heat Exchange
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Solution Overview
Problem
Existing absorption refrigeration systems face challenges in achieving high performance and compactness due to limitations in heat exchanger size and efficiency, particularly in LiBr-water systems, where the absorption and desorption processes are hindered by the limited water mass transfer coefficient of the LiBr solution, leading to suboptimal heating and cooling capabilities.
Innovation Solution
The development of an absorption-based heater with a desorber and absorber separated by a heat exchanger on a fluid barrier plate, utilizing vapor-permeable membranes over three-dimensionally structured microchannels to enhance heat exchange, allowing for improved absorption and desorption rates through membrane-based thin film technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional falling film or pool boiling heat exchanger configurations are used in LiBr-water absorption systems, then the system can achieve basic heating and cooling functions, but the heat exchanger size becomes large and the water mass transfer coefficient remains limited
Solution Approach 1:
The patent employs thin film configurations where LiBr solution flows as a thin film over structured surfaces rather than conventional falling film or pool boiling. This thin film approach dramatically increases the water mass transfer coefficient while reducing the required heat exchanger volume, directly resolving the contradiction between transfer efficiency and system size.
Solution Approach 2:
The patent utilizes three-dimensionally structured microchannels with porous or structured surfaces that enhance the thin film absorption and desorption processes. These structured surfaces increase the effective surface area and improve mass transfer coefficients without proportionally increasing the overall heat exchanger volume.
2Productivity
If ultra-thin film absorbers with nanofiber membranes are used to improve absorption rates, then the absorption rate increases beyond conventional absorbers, but the system complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of using complex nanofiber membranes throughout the entire system, the patent applies three-dimensionally structured microchannels and thin film configurations at specific locations where mass transfer enhancement is most needed. This localized approach achieves high absorption rates while avoiding the manufacturing complexity of full-system nanofiber membranes.
Solution Approach 2:
The patent transitions from two-dimensional flat plate heat exchangers to three-dimensionally structured microchannels, creating vertical and horizontal structures that enhance surface area and mass transfer without requiring nanofiber membrane technology. This dimensional approach achieves high absorption rates with manufacturable structures.
3Volume of stationary object
If compact heat exchanger architectures are developed to reduce system volume, then the system becomes more suitable for small-scale applications, but the heat exchange efficiency and surface area available for absorption and desorption may be reduced
Solution Approach 1:
The patent employs three-dimensionally structured microchannels that utilize vertical and horizontal spaces efficiently. This allows the system to pack more heat exchange surface area into a smaller overall volume by creating multi-level structures rather than relying on simple planar expansion.
Solution Approach 2:
By using thin film configurations over structured surfaces, the patent achieves high heat exchange efficiency in a compact form. The thin films conform to the three-dimensional structures, maximizing surface area utilization within the available volume without requiring large planar surfaces.
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 a higher coefficient of performance (COP) of about 1.63, enabling compact, efficient, and cost-effective heating and cooling systems suitable for small-scale applications while maintaining minimal volume and achieving improved surface area for water heating and dehumidification.
Implementation Method 1
The vapor permeable membrane is permeable to a refrigerant in the vapor state but impermeable to an absorbent solution that flows on the vapor exchange faces of the absorption based heater
Implementation Method 2
heat exchanger, and absorber sequentially residing on different portions of a fluid barrier heat exchanging plate
Implementation Method 3
absorber sequentially residing on different portions of a fluid barrier heat exchanging plate
Implementation Method 4
desorber, heat exchanger, and absorber sequentially residing on different portions of a fluid barrier heat exchanging plate
Data Source
AI summary
An absorption based heater is constructed on a fluid barrier heat exchanging plate such that it requires little space in a structure. The absorption based heater has a desorber, heat exchanger, and absorber sequentially placed on the fluid barrier heat exchanging plate. The vapor exchange faces of the desorber and the absorber are covered by a vapor permeable membrane that is permeable to a refrigerant vapor but impermeable to an absorbent. A process fluid flows on the side of the fluid barrier heat exchanging plate opposite the vapor exchange face through the absorber and subsequently through the heat exchanger. The absorption based heater can include a second plate with a condenser situated parallel to the fluid barrier heat exchanging plate and opposing the desorber for condensation of the refrigerant for additional heating of the process fluid.