FLOW CELL STUDIES ON FOULING CAUSED BY PROTEIN -CALCIUM PHOSPHATE DEPOSITION IN TURBULENT FLOW

A comparative study of the calcium phosphate fouling process, with and without proteins, was carried out using both standard 316 2R stainless steel and 2R surfaces modified by TiN magnetron sputtering. Fouling behavior was assessed in a heat transfer flow cell operating in the turbulent flow regime. The fouling curves resulting from calcium phosphate deposition in the absence of proteins were substantially different from the ones obtained when protein was present. In this last case, two different fouling periods could be observed. The surface energy of the modified materials was found to affect the deposition parameters (rate of deposition and final amount of deposit) leading to higher amounts of deposit on higher energy surfaces in the absence of protein, while leading to less deposit in its presence. The standard 316 2R substrate proved to be less prone to fouling from protein-calcium phosphate solutions than the TiN modified surfaces. However, the same conclusion could not be drawn for calcium phosphate solutions

Tailored surface energy of stainless steel plate coupons to reduce the adhesion of aluminium silicate deposit

Fouling in heat exchangers not only reduces heat transfer performance significantly, but also causes considerable pressure drop, resulting in higher pumping requirements. It would be much more desirable if surfaces which are inherently less prone towards fouling could be developed. In this paper, autocatalytic Nickel–Phosphorus–Polytetrafluoroethylene (Ni–P–PTFE) composite coatings and modified diamond-like carbon (DLC) coatings were applied to the coupons of the 316L stainless steel plates. The effects of surface energies of the coatings on the adhesion of aluminium silicate fouling were investigated and the best surface energy for which the fouling adhesion is lowest was obtained. The experimental results show that the coating with the most favourable surface energy reduced the adhesion of aluminium silicate deposit by 97%, compared with uncoated stainless steel plate coupons. The anti-fouling mechanism of the coatings was explained with the extended Deryagin, Landau, Verwey and Overbeek (DLVO) theor

Heat transfer correlation for flow boiling in small to micro tubes

This article is available open access under a Creative Commons license (http://creativecommons.org/licenses/by-nc-nd/3.0/) Copyright © 2013 The Authors. Published by Elsevier Ltd. All rights reserved.There is a large discrepancy in the open literature about the comparative performance of the existing macro and microscale heat transfer models and correlations when applied to small/micro flow boiling systems. This paper presents a detailed comparison of the flow boiling heat transfer coefficient for R134a in stainless steel micro tubes with 21 macro and microscale correlations and models. The experimental database that was used in the comparison includes the data for 1.1 and 0.52 mm diameter tubes, mass flux range of 100–500 kg/m2 s and system pressure range 6–10 bar obtained in the course of this study. The effect of the evaporator heated length on the comparative performance of the correlations and models was investigated using three different lengths of the 1.1 mm diameter tube (L = 150, 300 and 450 mm). This comparative study demonstrated that none of the assessed models and correlations could predict the experimental data with a reasonable accuracy. Also, the predictability of most correlations becomes worse as the heated length increases. This may contribute in explaining the discrepancy in the comparative performance of the correlations from one study to another. A new correlation is proposed in the present study based on the superposition model of Chen. The database used in developing the correlation consists of 5152 data points including the current experimental data and data obtained previously with the same test rig, fluid and methodology for tubes of diameter 4.26, 2.88, 2.01 mm. The new correlation predicted 92% of the data within the ±30% error bands with a MAE value of 14.3%

The magnetic model of the LHC in the early phase of beam commissioning

The relation between field and current in each family of the Large Hadron Collider magnets is modelled with a set of empirical equations (FiDeL) whose free parameters are fit on magnetic measurements. They take into account residual magnetization, persistent currents, hysteresis, saturation, decay and snapback during initial part of the ramp. Here we give a first summary of the reconstruction of the magnetic field properties based on the beam observables (orbit, tune, coupling, chromaticity) and a comparison with the expectations. The most critical issues for the machine performance in terms of knowledge of the relation magnetic field vs current are pointed out.peer-reviewe

Ion implantation of stainless steel heater alloys for anti-fouling applications

Ion implantation of fluorine and silicon ions into stainless steel heater alloys inhibits the accumulation of CaSO4 deposits when used in an saturated aqueous solution of 1.6 g/l concentration. This anti-fouling action leads to an increase in the heat transfer coefficient by more than 100% under a heat flux of 200 kW/m2 and 200% under a heat flux of 100 kW/m2 when compared to unimplanted heater elements. Heat transfer data indicate that following a heating cycle of 4000 minutes a thick layer of CaSO4 deposit remain on unimplanted heater surfaces. Similar CaSO4 deposits also formed on the implanted alloys initially but did not remain after 1000 minutes causing a significant recovery in the heat transfer coefficient. Ion implanting these alloys leads to surface energy reduction and hence the anti-fouling action observed