Rotating Impeller Air Gap Membrane Distillation Flux
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Solution Overview
Problem
Membrane distillation technology, particularly air gap membrane distillation, faces challenges in achieving high permeate flux and energy efficiency due to resistance from air in the distillate chamber, leading to low commercial adoption despite advancements in membrane development.
Innovation Solution
Incorporating a rotating impeller within the air gap compartment of the membrane distillation apparatus to decrease pressure on the permeate side of the membrane, enhance vapor permeation, and promote mass and heat transfer through turbulent dissipation, while using a thermally conductive plate for condensation of water vapor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rotating impeller is added to the air gap compartment to enhance vapor permeation and mass transfer, then permeate flux and energy efficiency are improved, but device complexity increases
Solution Approach 1:
The patent applies the dynamics principle by introducing a rotating impeller into the air gap compartment, transforming the static air gap system into a dynamic one. The impeller rotation creates turbulent flow patterns that actively enhance mass transfer and vapor permeation through the membrane, directly addressing the low productivity issue while maintaining a relatively simple mechanical structure
Solution Approach 2:
The patent utilizes pneumatic principles by employing the impeller to generate fluid motion and pressure variations within the air gap compartment. The rotating impeller creates localized pressure gradients and turbulent flow that facilitate enhanced vapor transport and mass transfer, improving permeate flux through fluid dynamic mechanisms
2Ease of operation
If the air gap compartment is filled with air to enable vapor transport, then membrane distillation can proceed, but resistance from air reduces permeate flux and energy efficiency
Solution Approach 1:
The patent applies the extraction principle by removing the detrimental effect of air resistance through impeller-driven flow. Instead of trying to eliminate air from the system, the impeller extracts the harmful stagnation and creates continuous motion that overcomes air resistance, maintaining the ease of operating with an air-filled compartment while improving productivity
Solution Approach 2:
The rotating impeller creates periodic flow patterns and pressure variations in the air gap compartment. This periodic action disrupts the stagnant air layers that cause resistance, creating cyclical zones of high and low pressure that facilitate continuous vapor transport through the membrane, thereby increasing permeate flux
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 implementation of a rotating impeller increases permeate flux by up to 147% and improves energy efficiency, resulting in higher water purity and reduced operational costs, making membrane distillation more viable for desalination and waste treatment applications.
Implementation Method 1
A membrane provides a barrier for a liquid phase while allowing a vapor phase to pass through the membrane
Implementation Method 2
The membrane defines pores that are sized to allow water vapor originating from the hot medium stream to pass from the hot medium compartment through the membrane to the air gap compartment
Implementation Method 3
The thermally conductive plate and the cold medium stream within the cold medium compartment are cooperatively configured to condense the water vapor from the hot medium compartment that passed through the membrane
Implementation Method 4
The thermally conductive plate and the cold medium stream within the cold medium compartment are cooperatively configured to condense the water vapor
Implementation Method 5
The impeller is configured to mix fluid within the air gap compartment in response to the rotatable shaft being rotated by the motor
Data Source
AI summary
A membrane distillation apparatus includes a housing and an impeller. The housing includes a hot medium compartment, a cold medium compartment, an air gap compartment, a membrane, and a thermally conductive plate. The hot medium compartment includes a hot medium inlet configured to receive a hot medium stream including water. The cold medium compartment includes a cold medium inlet configured to receive a cold medium stream. The membrane defines pores that are sized to allow water vapor originating from the hot medium stream to pass from the hot medium compartment through the membrane to the air gap compartment. The thermally conductive plate and the cold medium stream are cooperatively configured to condense the water vapor from the hot medium stream. The air gap compartment is substantially filled with air and includes a permeate outlet configured to discharge the condensed water vapor. The impeller is disposed within the air gap compartment.