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Staffordshire, United Kingdom

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
Case Studies in Thermal Engineering | Year: 2014

Heat transfer fluids (HTF) need to be regularly sampled to assess the extent of thermal degradation, oxidative state, the accumulation of short-chained light-ends and contamination by intrinsic or extrinsic particles. The build-up of light-ends in a HTF system presents a potential fire hazard. A light-ends removal kit (LERK) enables light-ends to be removed continuously, helping to push-up flash point temperatures. In the current case, the concentration of light-ends started to build-up in the client's system and a LERK was subsequently installed. Data is presented that shows how effective the LERK was in restoring mean closed flash point temperature to stable levels, similar to those seen for a virgin HTF. Closed flash point temperature was, in this case, more variable than open flash point temperature. This highlights the need to make direct measurements of closed flash point temperature as opposed to indirect measurements of open flash point temperature. This case emphasises the need for regular HTF sampling and analysis, and that the installation of a LERK can help maintain the condition and life of a HTF. © 2014 The Author. Published by Elsevier Ltd.

Wright C.I.,Global Group | Premel J.,SNCF
Case Studies in Thermal Engineering | Year: 2014

Heat transfer fluids (HTF) should be analysed at least once per year to determine the extent of thermal degradation. Under normal operating conditions, mineral-based HTFs will thermally degrade and the bonds between hydrocarbons break to form shorter-chain hydrocarbons known as "light-ends". These light-ends accumulate in a HTF system and present a future potential fire risk. Light-ends can be removed from a HTF system via a batch vent or installation of a temporary or permanently installed light-ends removal kit (LERK). Data was collected prior to and following batch venting or installation of a LERK. The main study parameter was closed flash temperature as open flash temperature and fire point did not change considerably. Analysis showed that both methods increased closed flash temperature in excess of 130°C three months after the intervention, so both methods were deemed effective. Data showed that the percentage change achieved with the LERK, compared to batch venting, was 2-fold higher at three months and 10-fold higher at 6 months. The duration of effect was longer with the LERK with closed flash temperature being stable and consistently above 130°C for 50 months after being permanently installed. This case highlights the effectiveness of a permanently fitted LERK which is effective for the longer-term control of closed flash temperature. However, mobile LERKs could be an option for manufacturers looking to manage closed flash temperature on a shorter-term basis or as an alternative to batch venting. © 2014 The Authors. Published by Elsevier Ltd.

Wright C.I.,Global Group
Case Studies in Thermal Engineering | Year: 2014

Heat transfer fluid (HTF) ageing is a complicated chemical process. Laboratory techniques can provide rapid insights into the status of a HTF and a HTF system. In the current case, a potential client had requested their newly charged HTF be analysed. Prior to filling, however, the system had been flushed with caustic and water. The client reported reduced flow rates, high sludge formation in filters and regular HTF top-ups. Laboratory testing indicated that the HTF was showing signs of serious thermal cracking (high carbon levels and low flash point temperatures) and significant thermal oxidation (a high total acid number). The recommendation was to drain the HTF from the system and flush the system to remove carbon, acids and flammable by-products. This action would work to reduce the risks associated with coke depositing on the internal pipework of the system and eliminate any fire risk presented by the formation of flammable by-products within the system. The case highlights the detrimental effects of HTF decomposition on a system as well as the need to flush a system with a fluid intended to be used as a flush and to washout any residual cleaner prior to filling with a new HTF. © 2014 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.

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