scholarly journals Selection of materials for biofouling detection in cooling water systems

2017 ◽  
Vol 18 (4) ◽  
pp. 1162-1172
Author(s):  
Joana Melo Mota ◽  
Maria Diná Afonso
Keyword(s):  
High Density Polyethylene ◽  
Vibration Amplitude ◽  
Food Industry ◽  
Cooling Water ◽  
Water Systems ◽  
Vibration Sensor ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Effective Roughness ◽  
Selection Of

Abstract This work aimed to select materials capable of favouring biofouling build-up in order to develop plain coupons as alternative to expensive commercial biofouling mesh coupons. Plain coupons of copper, stainless steel (SS), polyvinyl chloride (PVC) and high density polyethylene (HDPE) were dipped and tested in a cooling water from a food industry. PVC and HDPE coupons showed promising responses and appear to be preferable since they are corrosion-free. Moreover, an experimental vibration sensor monitored biofilm adhesion on SS and PVC tubular coupons (simulators of the respective sensor tubes), inside which flowed the water aforementioned. The SS sensor tube and tubular coupons displayed the most satisfactory results, i.e. the highest vibration amplitude and the highest adhered biofilm mass, respectively. Biofilm adhesion onto the materials tested depended on their surface shear stress, effective roughness and hydrophobicity, as determined by scanning electron microscopy and goniometry.

The boundary layer over an impulsively started flat plate

1969 ◽  
Vol 310 (1502) ◽  
pp. 401-414 ◽  
Keyword(s):  
Boundary Layer ◽  
Leading Edge ◽  
Surface Shear Stress ◽  
Unsteady State ◽  
Similarity Condition ◽  
Surface Shear ◽  
Boundary Layer Problem ◽  
Independent Variables ◽  
Selection Of ◽  
Layer Problem

A numerical solution has been obtained for the development of the flow from the initial unsteady state described by Rayleigh to the ultimate steady state described by Blasius. The usual formulation of the problem in two independent variables is dropped, and three independent variables, in space and time, are reverted to. The boundary-layer problem is unconventional in that the boundary conditions are not completely known. Instead, it is known that the solution should satisfy a similarity condition, and use is made of this to obtain a solution by iteration. A finite-difference technique of a mixed, explicit-implicit, type is employed. The iteration converges rapidly. It is terminated where the maximum errors are estimated to be about 0.04%. A selection of the results for the velocity profiles and the surface shear stress is presented. One striking feature is the rapidity of the transition from the Rayleigh to the Blasius state. The change is practically complete, at a given station on the plate, by the time the plate has moved a distance equal to four times the distance from the station to the leading edge of the plate.

Technical Basis for Maximum Allowable Indentation Depths in HDPE Pipes for Proposed ASME Section III Code Case on Alternative Requirements to Appendix XXVI for Inspection and Repair

2019 ◽  
Author(s):  
Douglas Scarth ◽  
Prabhat Krishnaswamy ◽  
Phillip Rush ◽  
Douglas Munson
Keyword(s):  
High Density Polyethylene ◽  
Large Diameter ◽  
Cooling Water ◽  
Water Systems ◽  
Parent Material ◽  
Surface Conditions ◽  
Service Water ◽  
Piping Systems ◽  
Technical Basis ◽  
Hdpe Pipes

Abstract Mandatory Appendix XXVI of Section III of the ASME B&PV Code contains rules for the construction of Class 3 polyethylene pressure piping systems. The scope is limited to buried portions of Class 3 service water or buried portions of Class 3 cooling water systems, consisting of PE4710 High Density Polyethylene (HDPE) materials. The minimum Pennsylvania Notched Test (PENT) rating for the HDPE material is 2,000 hours. Appendix XXVI contains acceptance standards for the maximum allowable depths of gouges, cuts or other surface conditions that are characterized as indentations. The acceptance standards are considered to be very restrictive, in particular for large diameter HDPE pipes. Less restrictive maximum allowable indentation depths for pipes with a minimum PENT rating of 2,000 hours were developed based on use of results from tests performed on pressurized HDPE pipes containing flaws in the parent material. These maximum allowable indentation depths were implemented into the new Section III Code Case N-891 on alternative requirements to Appendix XXVI for inspection and repair. The technical basis for the maximum allowable indentation depths is described in this paper.

Detachment of biofilm bacteria due to variations in nutrient supply

1998 ◽  
Vol 37 (4-5) ◽  
pp. 211-214 ◽  
Author(s):  
Linda K. Sawyer ◽  
Slawomir W. Hermanowicz
Keyword(s):  
Phase Contrast ◽  
Digital Image Analysis ◽  
Specific Growth ◽  
Nutrient Supply ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Nutrient Limitations ◽  
Contrast Microscopy ◽  
Biofilm Bacteria ◽  
Observable Parameter

Growth and detachment rates of an environmental isolate of Aeromonas hydrophila attached to a surface were determined under varying nutrient supply conditions in a complex medium. Growth and detachment of cells were observed in real time using phase contrast microscopy in glass parallel plate flow chambers. Surface shear stress was controlled in all experiments at 3 N m−2. Images were taken every 15 min. Digital image analysis was used to determine specific growth and detachment rates. An observable parameter proportional to the nutrient depletion at the surface due to transfer limitations was used to indicate nutrient limitations. Specific detachment rates increased as the depletion parameter increased, indicating that nutrient limitations cause this bacterium to detach at greater rates.

Microencapsulation: A Prospective to Protect Probiotics

2020 ◽  
Vol 16 (6) ◽  
pp. 891-899 ◽  
Author(s):  
Wissam Zam
Keyword(s):  
Gastrointestinal Tract ◽  
Food Industry ◽  
Health Benefits ◽  
Probiotic Bacteria ◽  
Bacterial Cells ◽  
Beneficial Effects ◽  
Host Health ◽  
Resistant Strains ◽  
Selection Of

Probiotics are viable microorganisms widely used for their claimed beneficial effects on the host health. A wide number of researchers proved that the intake of probiotic bacteria has numerous health benefits which created a big market of probiotic foods worldwide. The biggest challenge in the development of these products is to maintain the viability of bacterial cells during the storage of the product as well as throughout the gastrointestinal tract transit after consumption, so that the claimed health benefits can be delivered to the consumer. Different approaches have been proposed for increasing the resistance of these sensitive microorganisms, including the selection of resistant strains, incorporation of micronutrients, and most recently the use of microencapsulation techniques. Microencapsulation has resulted in enhancing the viability of these microorganisms which allows its wide use in the food industry. In this review, the most common techniques used for microencapsulation of probiotics will be presented, as well as the most usual microcapsule shell materials.

Fluorescent-tagged no phosphate and nitrogen free calcium phosphate scale inhibitor for cooling water systems

2009 ◽  
Vol 113 (3) ◽  
pp. 1966-1974 ◽  
Author(s):  
Kun Du ◽  
Yuming Zhou ◽  
Liuqian Wang ◽  
Yingying Wang
Keyword(s):  
Calcium Phosphate ◽  
Cooling Water ◽  
Water Systems ◽  
Free Calcium ◽  
Scale Inhibitor
Sign in / Sign up

Export Citation Format

Share Document