Membrane Cooling Tower for Biofouling Prevention
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Solution Overview
Problem
Conventional cooling towers face issues such as organic matter growth, legionella development, scaling due to mineral concentration, and inefficient heat exchange, particularly in wet cooling systems, which require disinfectants and antiscalants, leading to pollution and larger surface areas.
Innovation Solution
A vertical cooling tower with dry heat exchanger surfaces using vapor-permeable, liquid-tight membrane walls and a multistage membrane distillation apparatus, where the liquid is cooled by air flowing from bottom to top, preventing biological growth and allowing for higher mineral concentration without scaling, using a U-pipe configuration to maintain optimal liquid flow and reduce pressure loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If wet cooling towers are used for efficient heat exchange, then thermal surface performance is improved, but biological growth (organic matter, legionella) occurs on the wet surfaces
Solution Approach 1:
A hydrophobic membrane is introduced as an intermediary between the liquid cooling medium and the air stream. The membrane allows vapor to pass through for heat exchange while preventing liquid water from contacting the air, thus eliminating the wet surfaces that support biological growth while maintaining evaporative cooling efficiency
Solution Approach 2:
The patent employs thin hydrophobic membrane films as the heat exchange surface. These films are permeable to water vapor but impermeable to liquid water, enabling evaporative heat transfer while keeping the liquid side contained and preventing biofilm formation on exposed surfaces
2Quantity of substance
If water concentration is increased to reduce fresh water requirement and blowdown water quantity, then water usage efficiency is improved, but scaling (mineral deposits) occurs
Solution Approach 1:
The patent changes the physical parameters of the heat exchange process by using vapor-phase mass and heat transfer through hydrophobic membranes. This allows operation at higher water concentrations without scaling because the hydrophobic membrane surface prevents mineral deposit adhesion, and the controlled evaporation rate maintains favorable crystallization conditions
3Reliability
If disinfectants and antiscalants are added to prevent biological growth and scaling, then reliability is improved, but pollution of blowdown water increases
Solution Approach 1:
The patent converts the potential harm of concentrated minerals and organic matter into a benefit by using hydrophobic membranes that are inherently resistant to fouling and scaling. The membrane material itself provides the protection previously requiring chemical additives, and the blowdown water contains fewer contaminants because the membrane prevents adhesion of minerals and organic compounds
4Object-affected harmful factors
If induced draft cooling towers with fans are used to prevent biological growth, then biological growth is reduced, but energy consumption increases
Solution Approach 1:
The cooling tower system uses natural draft created by the temperature difference between the hot rising air/vapor mixture and the cooler ambient air. The hydrophobic membrane enables sufficient evaporative cooling to create this natural draft without requiring mechanical fans, thus eliminating the high energy consumption of induced draft systems while maintaining dry surfaces that prevent biological growth
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 solution achieves efficient heat exchange with dry surfaces, preventing biological growth and scaling, allowing for higher mineral concentration and reduced chemical usage, while maintaining thermal performance comparable to conventional wet cooling towers.
Implementation Method 1
a respective liquid passage which is separated from the gas space of the cooling tower at least partly by a vapor-permeable, liquid-tight membrane wall at both sides
Implementation Method 2
vapor-permeable, liquid-tight membrane wall
Implementation Method 3
the liquid is cooled in the cooling tower by a cooling gas, in particular air, flowing from bottom to top
Implementation Method 4
cooling gas, in particular air, flowing from bottom to top
Data Source
AI summary
A cooling device for cooling a fluid comprises a vertical cooling tower, into an upper area of which the fluid to be cooled is fed and from a lower area of which the cooled fluid is discharged. The fluid in the cooling tower is cooled by a cooling gas flowing from the bottom to the top. At least one installation in which the fluid is conducted is provided in the gas space of the cooling tower through which cooling gas flows. Each installation comprises at least one fluid channel that is separated at least in part from the gas space of the cooling tower by a fluid-tight membrane wall that is permeable to vapor on both sides.