title: Numerical performance comparison of different tube cross–sections for heat recovery from particle-laden exhaust gas streams

authors: Walmsley, Timothy Gordon

subjects: heat recovery

abstract: Heat recovery from exhaust gas streams is applicable to a wide variety of industries. However, high heat transfer resistance of gases and the presence of entrained particulate matter that readily fouls limits industry uptake of current heat recovery technology. Improvements to standard heat exchanger designs are needed. In this study Computational Fluid Dynamics (CFD) is used to investigate the effect of ten different tube cross-sections on heat transfer resistance, gas flow resistance and foulability. The average wall shear stress around the shape is used to predict foulability and an estimated asymptotic fouling resistance is used to calculate an equivalent fouled Coulburn j factor, jf. CFD results show the best tube for exhaust heat recovery is an elliptical tube closely followed by the flattened round tube. The ellipse shape produced fouled Coulburn j factor, jf values, expressed as a ratio of tube bank friction factor f, over 100% higher than that of standard round tube. A flattened round tube is also promising, given enough spacing between the tubes, and may be the practical economic optimum.

text: Numerical performance comparison of different tube cross–sections for heat recovery from particle-laden exhaust gas streams Heat recovery from exhaust gas streams is applicable to a wide variety of industries. However, high heat transfer resistance of gases and the presence of entrained particulate matter that readily fouls limits industry uptake of current heat recovery technology. Improvements to standard heat exchanger designs are needed. In this study Computational Fluid Dynamics (CFD) is used to investigate the effect of ten different tube cross-sections on heat transfer resistance, gas flow resistance and foulability. The average wall shear stress around the shape is used to predict foulability and an estimated asymptotic fouling resistance is used to calculate an equivalent fouled Coulburn j factor, jf. CFD results show the best tube for exhaust heat recovery is an elliptical tube closely followed by the flattened round tube. The ellipse shape produced fouled Coulburn j factor, jf values, expressed as a ratio of tube bank friction factor f, over 100% higher than that of standard round tube. A flattened round tube is also promising, given enough spacing between the tubes, and may be the practical economic optimum.

year: 2012

title: Scientific evaluation of deterioration of historic huts of Ross Island, Antarctica

authors: Farrell, Roberta L.

subjects: Ross Island

abstract: There are many challenges facing conservation of the historic
huts in Antarctica including non-biological, biological and
environmental impacts explains Professor Roberta L. Farrell,
Department of Biological Sciences, the University of Waikato. The article presents a discussion of historical huts of Ross Island, Antarctica.

text: Scientific evaluation of deterioration of historic huts of Ross Island, Antarctica There are many challenges facing conservation of the historic
huts in Antarctica including non-biological, biological and
environmental impacts explains Professor Roberta L. Farrell,
Department of Biological Sciences, the University of Waikato. The article presents a discussion of historical huts of Ross Island, Antarctica.

year: 2007

title: Te tuangi (the clam): A metaphor for teaching, learning and the key competencies

authors: Simpson, Mary Louisa

subjects: Early childhood

abstract: This article explores the shift from “essential skills” to “key competencies” in the school curriculum. Drawing on information gathered from teacher interviews and observations at a New Zealand primary school, this article suggests that culture and context strongly shape and influence the interpretation of key competencies. The authors develop a metaphor—te tuangi—to theorise the relationship between a learner (akonga) and a teacher (kaiako) in a cultural and social context.

text: Te tuangi (the clam): A metaphor for teaching, learning and the key competencies This article explores the shift from “essential skills” to “key competencies” in the school curriculum. Drawing on information gathered from teacher interviews and observations at a New Zealand primary school, this article suggests that culture and context strongly shape and influence the interpretation of key competencies. The authors develop a metaphor—te tuangi—to theorise the relationship between a learner (akonga) and a teacher (kaiako) in a cultural and social context.

year: 2011