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Wright C.I.,Global Group | Bembridge T.,Kinetic Partners
Case Studies in Thermal Engineering | Year: 2015

This article describes a series of experiments to assess the performance and suitability of a permittivity sensor in the area of heat transfer. The permittivity sensor measures condition index and temperature of a fluid. A series of 5 experiments was conducted. They assessed the reproducibility of the sensor using both clean and dirty fluid samples, and showed the sensor had good reproducibility based on calculations of coefficients of variation. The sensor also detected water contamination, assessed from construction of a stimulus-response curve to step-wise increases in water and from real-life samples where water content was reported to be out of specification. Further experiments tested the association between condition index and both water content and fluid cleanliness in a real-life setting. Results demonstrated the sensor that condition index reflected changes in fluid water and cleanliness and was therefore a measure of fluid condition. The implication of these findings is that the sensor can be used to make rapid and reliable assessments of fluid condition using only small samples (i.e., <50 ml). The sensor may be of benefit to customers that need to make a lot of regular samples over a large processing site, such as concentrated solar power plants. © 2015 The Authors.

Wright C.I.,Global Group | Bembridge T.,Kinetic Partners | Picot E.,Pole Etudes Locomotive et TGV Optimisation de la Maintenance TGV Chez SNCF | Premel J.,Pole Etudes Locomotive et TGV Optimisation de la Maintenance TGV Chez SNCF
Applied Thermal Engineering | Year: 2015

It is reported that there are some 4000 companies operating high temperature thermal fluid systems in the UK and Ireland. This excludes steam or water based systems. The heat transfer fluids (HTFs) used in food processing are highly refined mineral HTFs that are non-toxic, non-irritating and lack an odour. If an HTF has been certified for use in food processing it carries an HT-1 certificate. HTFs suitable for use in food processing are commonly referred to as 'non-fouling' which means as they thermally degrade they produce small carbon particles that are suspended in the HTF. Moreover, the carbon formations are less sticky and this reduces the extent of adhesion to the internal surfaces of an HTF system. The current paper analysed the test reports from 1223 HTF systems and showed that, on average, the carbon residue for food grade HTF was lower than non-food grade HTF. This clearly demonstrates what the non-fouling nature of a food grade HTF. This paper then explored the regulatory, legal and environmental landscape for food grade HTFs. In this area of manufacturing, it is critical that the HTFs used are suitable for incidental contact with food. Other measures put consumer safety at the heart of all operations (i.e., internal company procedures such as hazard analysis and critical control points [HACCP]) and that food is safe for consumer consumption (e.g., external controls such as auditing manufacturers to ensure good quality and distribution practice). The authors introduce the idea that safety could be further enhanced through independent HTF sampling and chemical analysis of HTFs to ensure they are food grade and should be done without any interruption to a manufacturer's production. © 2015 Published by Elsevier Ltd.

Wright C.I.,Global Group | Picot E.,Pole Etudes Locomotive et TGV Optimisation de la Maintenance TGV Chez SNCF | Bembridge T.,Kinetic Partners
Applied Thermal Engineering | Year: 2015

A large number of industrial processes require the efficient transfer of heat energy. Heat transfer fluids (HTFs) are imperative in such processes. The efficient transfer of heat energy is affected by system fouling and past studies have mainly focused on the fouling of heat exchangers but not the overall system. In normal operations HTFs are routinely sampled and chemically analysed to get an insight into the condition of both the HTF and the heat transfer system. The aim of routine maintenance programmes is to sustain normal operation and slow the rate of thermal degradation. HTF analysis is used to assess the chemical by-products of thermal degradation and oxidation. It is also used to detect system wear particles, water and contamination. Manufacturers often recommend that an HTF is analysed at least once per year. To date, however, it is unclear if this is the optimal sampling frequency. The current study investigated if sampling frequency had any bearing on the overall condition of mineral-based HTFs. Results revealed that parameters of HTF condition were inversely related to sampling frequency with increases in sampling frequency being correlated with improvements in overall HTF condition. This implies that frequent sampling works to improve the health of mineral-based HTFs. The implication being that a mineral HTF should be assessed as frequently as possible. Furthermore, when systems are sampled regularly (i.e., ≥1 per year), total acid number and closed flash temperature need to be monitored closely as these were most frequently out of specification when sampled between once per year and four times per year. © 2014 Elsevier Ltd. All rights reserved.

Wright C.I.,Global Group of Companies | Bembridge T.,Kinetic Partners | Wright E.A.,Credit Suisse
Renewable Energy Focus | Year: 2015

IN THIS follow-up to last issue's 'Case study in CSP plant performance,' the authors report on the results of heat transfer fluid experiments using permittivity sensors to maintain the lifetime of CSP plants.

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