Scraped Surface Heat Exchanger Geometry for Lower Scraper Wear
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Solution Overview
Problem
Scraped surface heat exchangers used in microparticulation of whey for producing whey protein concentrate face high wear issues due to high shear rates and speeds required to achieve desired particle sizes, leading to reduced equipment lifespan and increased maintenance costs.
Innovation Solution
The design of a scraped surface heat exchanger with a cylindrical inner surface and a rotatable shaft featuring gap portions that extend over at least 60% of the circumference, a specific radius ratio, and a protective layer, operating at reduced shear rates and speeds, significantly reduces scraper wear and extends cleaning cycle times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high shear rate and high shaft speed are used to achieve mean particle size of about 5 μm, then particle size control is improved, but scraper wear increases
Solution Approach 1:
The invention changes the geometric parameters of the shaft (gap portions extending over at least 60% of circumference, ratio of second radius to gap of at least 6, gap width less than 15 mm) to enable operation at reduced shear rates and shaft speeds while maintaining the required particle size control, thereby reducing scraper wear
Solution Approach 2:
The shaft is designed with non-uniform structure featuring gap portions that extend over at least 60% of the circumference, creating localized variations in the gap width that optimize the shear distribution and reduce overall scraper wear while maintaining particle size control
2Manufacturing precision
If high shaft speed is used to achieve desired particle size, then particle size control is improved, but electrical power consumption increases
Solution Approach 1:
The invention changes the shaft geometry parameters (gap portions, radius ratios, gap widths) to enable achieving the required particle size control at significantly reduced shaft speeds, thereby reducing electrical power consumption by over 50%
3Productivity
If extended production time between cleaning cycles is desired, then operational efficiency is improved, but particle quality control may worsen
Solution Approach 1:
The optimized shaft geometry enables extended production cycles while maintaining particle size control, as the redesigned gap structure provides more stable shear conditions over time
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 configuration results in a 50% increase in production time between cleaning cycles, reduced energy consumption, longer equipment lifespan, and a narrower particle size distribution around the desired 5 μm average size, while saving maintenance and power costs.
Implementation Method 1
the shear rate (D=v(R)/δ=1/30*n*n*R/δ) exerted by the scraping member on the whey protein material is less than about 600/s
Implementation Method 2
heating whey protein material in a scraped surface heat exchanger
Implementation Method 3
a shaft being rotatable mounted inside of and concentrically to the inner surface of the heat exchanging wall
Data Source
AI summary
The invention relates to a scraped surface heat exchanger (100) comprising a heat exchanging wall (20) having an cylindrical inner surface (21) with a radius (R+.delta.), a shaft (10) being rotatable mounted inside of and concentrically to the inner surface (21) of the heat exchanging wall (20) and having at least one gap portion (10A) with an outer surface (11) and a radius (R), and at least one scraping member (40) supported by the shaft (10) and extending to the inner surface (21) of the heat exchanger wall (20), characterized in that the at least one or the gap portions (10A) with an outer surface (11) and a radius (R) extend over at least 60% of the circumference of the shaft (10).