Staged Liquid Desiccant Air Conditioning for High-Humidity Control
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Solution Overview
Problem
Existing air conditioning systems are inefficient in removing high humidity levels and rely heavily on fossil fuel-powered electricity, leading to significant energy wastage and high operational costs, with desiccant-based systems failing to achieve economic viability due to high costs and inefficiencies.
Innovation Solution
An air conditioning system using a liquid desiccant with progressively changing concentration in multiple sectors, coupled with heat exchangers that facilitate turbulent flow to maximize heat transfer, allowing for efficient dehumidification and humidification, and utilizing low-temperature regeneration and cooling sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If compressor-based air conditioning is used to remove humidity, then cooling capacity is provided, but energy consumption increases significantly (up to 60% of total AC energy)
Solution Approach 1:
The air conditioning process is divided into separate functional stages: a dehumidification stage using liquid desiccant to remove moisture from air, and a cooling stage using heat exchangers to cool the dehumidified air. This segmentation allows each stage to operate optimally without the energy inefficiencies of compressor-based systems that attempt to handle both functions simultaneously.
Solution Approach 2:
The system changes the concentration parameter of the liquid desiccant across multiple stages, using progressively more concentrated desiccant solutions in subsequent stages to maximize humidity removal efficiency. This parameter variation enables effective dehumidification at lower energy costs compared to compressor-based refrigeration.
2Loss of energy
If liquid desiccant systems are used for dehumidification, then energy savings are achieved, but capital cost is high and payback period is extended
Solution Approach 1:
The system uses liquid desiccant flow through heat exchangers and distribution systems to achieve dehumidification, replacing expensive compressor-based refrigeration cycles. The hydraulic system for circulating and concentrating the desiccant is simpler and more cost-effective than high-capacity compressors and refrigerant handling equipment.
Solution Approach 2:
The system recovers and reuses the liquid desiccant after it has absorbed moisture from the air. The desiccant is regenerated by evaporating the absorbed water, and the concentrated desiccant is reused in the dehumidification process. This recovery and reuse mechanism reduces operational costs and improves economic viability.
3Productivity
If liquid desiccant is used in air conditioning, then dehumidification efficiency improves, but risk of droplet carryover into conditioned space increases
Solution Approach 1:
The system uses heat exchangers as intermediary devices between the liquid desiccant and the conditioned air. The heat exchangers transfer heat and moisture without direct contact between the desiccant liquid and the air stream, eliminating droplet carryover while maintaining high dehumidification efficiency through the heat and mass transfer process.
4Device complexity
If single-stage desiccant systems are used, then device simplicity is maintained, but dehumidification performance at high humidity levels is insufficient
Solution Approach 1:
The dehumidification process is divided into multiple stages with progressively more concentrated liquid desiccant. Each stage handles a portion of the humidity removal, with the first stage using less concentrated desiccant and subsequent stages using increasingly concentrated solutions. This multi-stage approach achieves high dehumidification performance while maintaining reasonable system complexity through modular design.
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 achieves low humidity levels with a relatively high-temperature cooling source and concentrated desiccant solution using low-temperature heating, reducing energy consumption and costs while maintaining efficient air conditioning and dehumidification performance.
Implementation Method 1
an air stream, which may be 100% outside air, is humidity controlled by contact with a liquid desiccant of progressively changing concentration in a number of sectors
Implementation Method 2
Passing a cooling fluid through heat exchangers cools the air by contact with the cooled desiccant
Implementation Method 3
Passing a cooling fluid through heat exchangers cools the air by contact with the cooled desiccant
Data Source
AI summary
In a process and apparatus of conditioning an airstream, the airstream is contacted with a liquid desiccant absorber in each of at least two stages. The same apparatus is used as an evaporator to reconcentrate the desiccant. The desiccant for each said stage is cooled or heated externally to the absorber or evaporator using an external source of cooling supplied with a common cooling or heating fluid at each stage. The desiccant flows between the stages counter-current to the flow of the airstream such that at each step the concentration of the desiccant is reduced or increased by contact with the airstream so that the concentration in each stage is distinct from the concentration of the desiccant in the previous stages.