title: Tube shape selection for heat recovery from particle-laden exhaust gas streams

authors: Walmsley, Timothy Gordon

abstract: Heat recovery from exhaust gas streams is applicable to a wide variety of industries. Two problems encountered in exhaust gas heat recovery are: the high heat transfer resistance of gases and the presence of entrained particulate matter, which can limit the use of extended surface area. Standard heat exchangers use round tube. This study uses Computational Fluid Dynamics (CFD) to investigate whether round or another shape is the best tube selection for exhaust heat recovery.
Tube shape rankings are based on taking into account heat transfer, gas flow resistance and foulability. Foulability is inferred from the average wall shear stress around the front or back of each shape. An estimated asymptotic fouling resistance is used to calculate an equivalent fouled j factor, jf. CFD results suggest the best tube for exhaust heat recovery is an elliptical tube. The ellipse shape produced j/f and jf/f ratios (where f is the tube bank friction factor) over 1.5 times larger than that of standard round tube. A flattened round tube is also promising and may be the practical and economic optimum.

text: Tube shape selection for heat recovery from particle-laden exhaust gas streams Heat recovery from exhaust gas streams is applicable to a wide variety of industries. Two problems encountered in exhaust gas heat recovery are: the high heat transfer resistance of gases and the presence of entrained particulate matter, which can limit the use of extended surface area. Standard heat exchangers use round tube. This study uses Computational Fluid Dynamics (CFD) to investigate whether round or another shape is the best tube selection for exhaust heat recovery.
Tube shape rankings are based on taking into account heat transfer, gas flow resistance and foulability. Foulability is inferred from the average wall shear stress around the front or back of each shape. An estimated asymptotic fouling resistance is used to calculate an equivalent fouled j factor, jf. CFD results suggest the best tube for exhaust heat recovery is an elliptical tube. The ellipse shape produced j/f and jf/f ratios (where f is the tube bank friction factor) over 1.5 times larger than that of standard round tube. A flattened round tube is also promising and may be the practical and economic optimum.

year: 2011-12-01

title: Purification and preliminary characterization of an extracellular pullulanase from Thermoanaerobium Tok6-B1

authors: Plant, Adrian R.

subjects: biology

abstract: Extracellular pullulanase (pullulan 6-glucanohydrolase, EC 3.2.1.41) was purified from cell free culture supernatants of Thermoanaerobium Tok6-B1 by ammonium sulphate precipitation, affinity precipitation, gel exclusion and ion exchange chromatography. A final purification factor of over 1600 was achieved. A molecular weight of 120 kD was determined by steric exclusion HPLC. Enzyme activity was specifically directed towards the  1–6 glucosidic linkages of pullulan resulting in 100% conversion to maltotriose and also possessed activity towards  1–4 linkages of starch, amylopectin and amylose producing maltooligosaccharides (DP2-DP4) as products. Maltotetraose was slowly hydrolysed to maltose. Values of K m (% w/v) were 7.3×10⁻³ for pullulan, 2.7×10⁻³ for amylopectin and 4.7×10⁻³ for Lintner's starch. Pullulanase activity was resistant to 6 M urea and was thermostable at temperatures up to 80°C (t 1/2 in the order of hours). Above 80°C thermal denaturation was significant (t 1/2=17 min at 85°C; 5 min at 90°C) but became less so in the presence of substrate (pullulan or starch). Thermostability was greatest at the pH activity optimum (pH 5.5) and was promoted by Ca²⁺ ions.

text: Purification and preliminary characterization of an extracellular pullulanase from Thermoanaerobium Tok6-B1 Extracellular pullulanase (pullulan 6-glucanohydrolase, EC 3.2.1.41) was purified from cell free culture supernatants of Thermoanaerobium Tok6-B1 by ammonium sulphate precipitation, affinity precipitation, gel exclusion and ion exchange chromatography. A final purification factor of over 1600 was achieved. A molecular weight of 120 kD was determined by steric exclusion HPLC. Enzyme activity was specifically directed towards the  1–6 glucosidic linkages of pullulan resulting in 100% conversion to maltotriose and also possessed activity towards  1–4 linkages of starch, amylopectin and amylose producing maltooligosaccharides (DP2-DP4) as products. Maltotetraose was slowly hydrolysed to maltose. Values of K m (% w/v) were 7.3×10⁻³ for pullulan, 2.7×10⁻³ for amylopectin and 4.7×10⁻³ for Lintner's starch. Pullulanase activity was resistant to 6 M urea and was thermostable at temperatures up to 80°C (t 1/2 in the order of hours). Above 80°C thermal denaturation was significant (t 1/2=17 min at 85°C; 5 min at 90°C) but became less so in the presence of substrate (pullulan or starch). Thermostability was greatest at the pH activity optimum (pH 5.5) and was promoted by Ca²⁺ ions.

year: 1987

title: On the stage Māori medium ITE: Listening to students’ voices

authors: Lee-Morgan, Jenny Bol Jun

subjects: Māori medium education

abstract: Māori-medium initial teacher education (ITE) is a small but highly important group ‘on stage’ in te ao Māori and New Zealand education. While education plays a major role in Māori language revitalisation, Māori language is also pivotal to Māori education if the aspiration ‘to live as Māori’ (Durie, 2001) is to be fulfilled. Māori-medium teachers are critical to the success of learners and their whānau who select a Māori-medium pathway and who can make a meaningful difference to the educational outcomes of Māori (Hōhepa, Hāwea, Tamatea, & Heaton, 2014). This article draws on the students’ voices in a two-year research project that centered on the development of a teaching and learning initiative within one Māori-medium ITE programme. Building on previous work by Hōhepa et al. (2014), this study adds another layer of students’ voices to understand more clearly language related issues and student experiences in Māori-medium ITE programmes. The article presents some of the complexities associated with Māori language regeneration facing students of Māori-medium ITE, with the understanding that whatever appears on the stage is always part of a greater narrative behind the scenes.

text: On the stage Māori medium ITE: Listening to students’ voices Māori-medium initial teacher education (ITE) is a small but highly important group ‘on stage’ in te ao Māori and New Zealand education. While education plays a major role in Māori language revitalisation, Māori language is also pivotal to Māori education if the aspiration ‘to live as Māori’ (Durie, 2001) is to be fulfilled. Māori-medium teachers are critical to the success of learners and their whānau who select a Māori-medium pathway and who can make a meaningful difference to the educational outcomes of Māori (Hōhepa, Hāwea, Tamatea, & Heaton, 2014). This article draws on the students’ voices in a two-year research project that centered on the development of a teaching and learning initiative within one Māori-medium ITE programme. Building on previous work by Hōhepa et al. (2014), this study adds another layer of students’ voices to understand more clearly language related issues and student experiences in Māori-medium ITE programmes. The article presents some of the complexities associated with Māori language regeneration facing students of Māori-medium ITE, with the understanding that whatever appears on the stage is always part of a greater narrative behind the scenes.

year: 2017