Split Liquid Desiccant Air Conditioning with Membrane Dehumidification
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Solution Overview
Problem
Conventional mini-split air conditioning systems are inefficient in handling high humidity and cooling in small buildings, as they rely on evaporator coils that are better suited for sensible cooling rather than dehumidification, leading to unacceptable humidity levels when only small amounts of cooling are required.
Innovation Solution
A split liquid desiccant air conditioning system where the liquid desiccant flows down a support plate contained by a microporous membrane, with the air stream directed vertically over the membrane to absorb both latent and sensible heat, using a heat transfer fluid that flows counter to the air stream, and a regenerator that rejects heat to the environment, allowing for efficient heating and humidification of air in winter conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional mini-split air conditioning systems use evaporator coils for cooling, then sensible cooling is achieved, but dehumidification capability is insufficient leading to unacceptable humidity levels
Solution Approach 1:
The patent introduces liquid desiccant as an intermediary substance between the air stream and the cooling system. The desiccant absorbs moisture from the air stream through mass transfer, enabling effective dehumidification without relying solely on evaporator coils. This mediator allows the system to achieve both sensible cooling and latent heat removal (dehumidification) simultaneously.
Solution Approach 2:
The system changes the operational parameters by using liquid desiccant concentration gradients to drive moisture absorption. By controlling the desiccant strength and flow rates, the system optimizes both dehumidification performance and energy efficiency, resolving the contradiction between energy loss and humidity control.
2Productivity
If liquid desiccant systems use concentrated salt solutions for dehumidification, then dehumidification efficiency is improved, but desiccant carry-over risk increases
Solution Approach 1:
The patent employs microporous membranes as physical barriers to contain the liquid desiccant. These porous materials allow water vapor to pass through while blocking the salt solution, enabling efficient dehumidification without desiccant carry-over into the air stream. The membrane structure maintains productivity while eliminating the harmful effect of desiccant contamination.
Solution Approach 2:
The system uses replaceable microporous membranes that can be easily replaced if they become fouled or damaged. This approach allows the use of concentrated salt solutions for high dehumidification efficiency while managing the carry-over risk through periodic membrane replacement rather than requiring permanent complex containment systems.
3Temperature
If conventional systems use high-pressure refrigerant lines for mini-split installation, then cooling capability is achieved, but installation complexity and capital costs increase
Solution Approach 1:
The patent replaces the high-pressure mechanical refrigerant system with a liquid desiccant-based system operating at atmospheric or low pressure. The desiccant circulation pump and heat exchangers substitute for the compressor and refrigerant lines, achieving the same cooling capability while dramatically reducing installation complexity and eliminating the need for specialized high-pressure piping.
4Temperature
If evaporator coils are used in conventional mini-split systems, then cooling is provided, but mold growth risk increases due to condensate accumulation
Solution Approach 1:
The patent extracts the condensate accumulation problem by using liquid desiccant to absorb moisture directly in the air stream before it can condense and accumulate. The desiccant continuously absorbs water vapor, preventing the formation of standing condensate that would otherwise promote mold growth on evaporator coils and in drainage 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 provides efficient heating and humidification of air in small buildings at low capital and energy costs, reducing electricity consumption and eliminating the need for high-pressure refrigerant lines, while preventing desiccant carry-over and mold growth issues associated with conventional systems.
Implementation Method 1
a sheet of material positioned proximate to the at least one surface of each structure between the liquid desiccant and the air stream, said sheet of material permitting transfer of water vapor between the liquid desiccant and the air stream
Implementation Method 2
permitting transfer of water vapor between the liquid desiccant and the air stream
Implementation Method 3
the liquid desiccant dehumidifies and cools the air stream
Implementation Method 4
a reversible heat pump coupled to the conditioner and to the regenerator by heat transfer fluid pipes, wherein the heat pump pumps heat from the heat transfer fluid flowing in the conditioner to the heat transfer fluid flowing in the regenerator
Implementation Method 5
the liquid desiccant dehumidifies and cools the air stream
Implementation Method 6
the liquid desiccant dehumidifies and cools the air stream
Implementation Method 7
said regenerator causing the liquid desiccant to desorb water in the warm weather operation mode
Data Source
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AI summary
A split liquid desiccant air conditioning system for cooling and dehumidifying an air stream flowing into a space in a building. The split liquid desiccant air conditioning system comprises a conditioner located inside the building, said conditioner including a plurality of first structures arranged in a substantially vertical orientation, each structure having at least one surface across which a liquid desiccant can flow, each structure also including a passage through which a heat transfer fluid can flow, wherein the air stream flows between the structures such that the liquid desiccant dehumidifies and cools the air stream, the conditioner further comprising a sheet of material positioned proximate to the at least one surface of each structure between the liquid desiccant and the air stream, said sheet of material permitting transfer of water vapor between the liquid desiccant and the air stream. The split liquid desiccant air conditioning system further comprises a regenerator located outside the building connected to the conditioner by liquid desiccant pipes for exchanging liquid desiccant with the conditioner, said regenerator including a plurality of second structures arranged in a substantially vertical orientation, each structure having at least one surface across which the liquid desiccant can flow, each structure also including a passage through which a heat transfer fluid can flow, said regenerator causing the liquid desiccant to desorb water to an air stream flowing through the regenerator. The split liquid desiccant air conditioning system yet further comprises an indirect evaporative cooling unit coupled to the conditioner for receiving the heat transfer fluid that has flowed through the first structures and a portion of the air stream that has been dehumidified and cooled by the conditioner, said indirect evaporative cooling unit including a plurality of third structures arranged in a substantially vertical orientation, each structure having at least one surface across which water is flowed, each structure also including a passage through which the heat transfer fluid from the conditioner is flowed, wherein the portion of the air stream received from the conditioner flows between the structures such that the water is evaporated by the air stream, resulting in cooling of the heat transfer fluid which is returned to the conditioner, and wherein the air stream treated by the indirect evaporative cooling unit is exhausted to the atmosphere. The split liquid desiccant air conditioning system further comprises an apparatus for moving the air stream through the conditioner and the indirect evaporative cooling unit, an apparatus for circulating the liquid desiccant through the conditioner and regenerator, and an apparatus for circulating heat transfer fluid through the conditioner and the indirect evaporative cooling unit; and a heat source for heating the heat transfer fluid in the regenerator.