Membrane Dehumidification Contactor for Low-Energy Humidity Control
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Solution Overview
Problem
Conventional air conditioning systems are inefficient in humidity control, leading to high energy consumption and corrosion issues, while existing desiccant and liquid desiccant systems face challenges with space efficiency, energy regeneration, and direct contact-related problems.
Innovation Solution
An air temperature and humidity control device incorporating a first heat pump with a hygroscopic material-based contactor and a second heat pump, where the hygroscopic material flows through contactors with porous sidewalls, allowing for efficient heat and water vapor transfer without direct contact, and a second heat pump with coils for further temperature and humidity regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct expansion (DX) air conditioners are operated to condense moisture through supercooling, then humidity control is achieved, but significant energy is consumed during supercooling and reheating
Solution Approach 1:
A liquid desiccant is introduced as an intermediary substance to absorb moisture from air in a contactor. The desiccant solution circulates through heat exchangers, absorbing water vapor from incoming air without requiring supercooling of the air itself, thereby eliminating the energy-intensive cooling and reheating cycles of conventional DX systems
Solution Approach 2:
The system changes the thermodynamic parameters by using liquid desiccant at moderate temperatures (cooled by evaporator or heated by condenser) instead of supercooling air to below dew point. The desiccant's hygroscopic properties enable moisture removal at higher temperatures, and heat recovery from condenser or evaporator optimizes the thermal parameters of the desiccant solution
2Measurement precision
If liquid desiccant is sprayed for direct contact with air, then humidity control is achieved, but liquid desiccant droplets are entrained into air stream causing corrosion and health issues
Solution Approach 1:
A hydrophobic porous membrane is used as a thin film barrier in the contactor. The membrane allows water vapor to pass through via diffusion while blocking liquid desiccant droplets. This eliminates direct contact between liquid desiccant and air stream, preventing droplet entrainment, corrosion, and health issues while maintaining effective humidity control
Solution Approach 2:
The contactor employs a hydrophobic porous membrane material that selectively permits vapor transmission while repelling liquid. The porous structure provides large surface area for mass transfer, and the hydrophobic properties ensure liquid desiccant cannot penetrate through, solving the entrainment problem
3Measurement precision
If contact towers with packing materials are used, then humidity control is achieved, but the system becomes cumbersome and difficult to modulate for wide range of operations
Solution Approach 1:
The system is segmented into modular components: a compact contactor with membrane, external heat exchangers (evaporator and/or condenser), and a circulation pump. This modular segmentation replaces the monolithic contact tower with distributed, manageable units that can be independently sized and positioned, facilitating easy modulation for different operational requirements
Solution Approach 2:
The system transitions from the vertical dimension of tall contact towers to a distributed configuration where heat exchange occurs in separate external heat exchangers. The contactor becomes a compact horizontal or vertical unit, reducing overall system footprint and enabling flexible installation in various spatial configurations
4Quantity of substance
If hydrophobic porous material is used in contactors, then mass transfer potential is improved, but heat transfer potential is limited
Solution Approach 1:
The system merges the mass transfer function (performed by the hydrophobic porous membrane in the contactor) with heat transfer functions (performed by external heat exchangers). The evaporator cools the desiccant solution, the condenser heats it, and these heat exchange operations are combined with the moisture removal process, achieving both effective mass transfer and adequate heat transfer through coordinated system operations
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 solution provides efficient and energy-effective humidity control, reducing energy consumption and corrosion risks, while accommodating a wide range of operations with improved system modularity and cost-effectiveness.
Implementation Method 1
the hygroscopic material flows through contactors with porous sidewalls, allowing for efficient heat and water vapor transfer without direct contact
Implementation Method 2
a first heat pump with a hygroscopic material-based contactor and a second heat pump, where the hygroscopic material flows through contactors with porous sidewalls, allowing for efficient heat and water vapor transfer
Implementation Method 3
a contactor having at least one contact module with a porous sidewall that is permeable to water vapor and impermeable to the liquid desiccant employed
Data Source
AI summary
An air temperature and humidity control device is provided including a first heat pump having a compressor, an expansion valve, a condenser, and an evaporator. The first heat pump has a refrigerant circulating there through. A humidity controller includes a first contactor fluidly coupled to the evaporator and condenser. The first contact includes at least one contact module having a porous sidewall that defines an internal space through which a hygroscopic material flows. A first air flow is in communication with the porous sidewall of the first contactor. The device also has a second heat pump including a first polishing coil. The first polishing coil is substantially aligned with and arranged generally downstream from the first contactor relative to the first air flow.