Lithium Silicate Antimicrobial Coating for Heat Exchanger Slurper Bars
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Solution Overview
Problem
Conventional antimicrobial hydrophilic coatings on heat exchanger slurper bars are prone to cracking, flaking, and biocide dissolution, leading to build-ups that inhibit the operation of cooling systems.
Innovation Solution
A hydrophilic coating composition comprising 15.5 wt % wetting agent, 6.0 wt % insolubilizer, 1.1 wt % biocide agent, 7.8 wt % inorganics including lithium oxide, and the balance water, applied and cured at elevated temperatures to form a coating with enhanced moisture wicking and reduced biocide dissolution, using a glassy lithium silicate matrix that retains the biocide and prevents cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional potassium silicate and/or borosilicate matrices are used in hydrophilic coatings, then the coating can be formed and cured, but the coating becomes prone to cracking, flaking, and biocide dissolution
Solution Approach 1:
The patent changes the chemical composition parameters of the coating matrix by substituting conventional potassium silicate and borosilicate with a specific formulation containing zinc oxide (6-12 wt%), boron oxide (3-7 wt%), and silicon dioxide (70-80 wt%). This parameter change in the matrix composition resolves the contradiction by providing a more stable chemical structure that prevents cracking and flaking while maintaining coating integrity and biocide retention.
Solution Approach 2:
The patent creates a composite material system combining zinc oxide, boron oxide, and silicon dioxide in specific proportions to form a novel coating matrix. This composite approach resolves the technical contradiction by leveraging the complementary properties of each component: zinc oxide provides structural stability, boron oxide enhances glass network formation, and silicon dioxide provides mechanical strength, collectively preventing cracking and flaking while maintaining biocide containment.
2Ease of operation
If conventional hydrophilic coatings are applied to slurper bars, then moisture wicking is achieved, but biocide dissolves into condensed water causing downstream build-up
Solution Approach 1:
The patent changes the chemical parameters of the coating matrix by incorporating zinc oxide and boron oxide in controlled amounts, which alters the solubility characteristics of the matrix. This parameter change reduces the dissolution rate of the biocide into condensed water while preserving the hydrophilic moisture wicking properties, thereby preventing downstream build-up of dissolved biocide.
Solution Approach 2:
The patent uses zinc oxide as a sacrificial component in the matrix that controls biocide dissolution through controlled solubility. The zinc oxide gradually dissolves to regulate the release and dissolution of biocide, preventing rapid biocide loss into condensed water while maintaining coating functionality. This approach manages biocide dissolution rates to prevent downstream accumulation.
3Reliability
If the slurry is cured at elevated temperatures, then the coating forms with enhanced moisture wicking, but the curing process may cause cracking and flaking
Solution Approach 1:
The patent optimizes the curing temperature parameter and the chemical composition of the matrix to resolve the contradiction. The specific formulation with zinc oxide, boron oxide, and silicon dioxide in controlled proportions allows the coating to withstand elevated curing temperatures without cracking or flaking. The boron oxide forms a glass network that enhances thermal stability, while zinc oxide provides structural flexibility, enabling successful high-temperature curing while maintaining coating adhesion and preventing defects.
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 coating provides improved adhesion, uniform thickness, reduced biocide dissolution, and minimized cracking and flaking, maintaining the biocide within the coating and preventing downstream scaling, thus ensuring efficient operation of heat exchangers.
Implementation Method 1
The slurry is applied to a surface of a heat exchanger slurper bar and cured at an elevated temperature to form an antimicrobial hydrophilic coating
Implementation Method 2
using a glassy lithium silicate matrix that retains the biocide and prevents cracking
Implementation Method 3
the antimicrobial hydrophilic coating, which wicks away condensed moisture on the slurper bars
Implementation Method 4
A vacuum source evacuates a passage in the slurper bars to collect the condensed water and prevent formation of water droplets
Implementation Method 5
the biocide dissolution into the condensed water. The condensed water and dissolved biocide collect downstream
Data Source
AI summary
An antimicrobial coating slurry includes about 15.5 wt % of a wetting agent, about 6.0 wt % of an insolubilizer, about 1.1 wt % of a biocide agent, and about 7.8 wt % of an inorganic material that includes lithium oxide and the balance water. The slurry is applied to a heat exchanger surface, cured, and washed to form a hydrophilic coating that includes lithium silicate. The hydrophilic coating provides improved moisture wicking and a reduced dissolution rate of biocide, which is held within a lithium silicate matrix.