196,949 research outputs found
Letter from Samuel M. Loveridge to T.Z.R. Jones
No full text2 p.Sam Loveridge writes to T.Z.R. Jones, lamenting that Jones along with his associate Samuel Graves cancelled their insurance policies with Loveridge. In contrast to the possible pro-slavery motive behind John Ransom’s cancellation of his scholarship detailed in Letter 305, Sam Loveridge renews his scholarship to the College, reflecting that the “land of Liberty” hypocritically contains “3,000,000 of slaves.
Thermal response testing through the chalk aquifer
No full textThermal conductivity of the ground is an important parameter in the design of ground energy systems, which have an increasing role to play in providing renewable heat to the built environment. For larger schemes, the bulk thermal conductivity of the ground surrounding the system is often determined in situ using a thermal response test. Although this test method is commonly used, its limitations are often not fully understood, leading to an over-simplistic interpretation that may fail to identify key facets of the ground thermal behaviour. These limitations are highlighted using data from an instrumented thermal response test carried out in a 150 m deep borehole in east London. It is shown that a single, unique value of bulk thermal conductivity may not be appropriate, as stratification of the ground can lead to differences in thermal performance, depending on the direction of heat flow. Groundwater flow within the Chalk aquifer is also shown to have an important effect on the long-term heat transfer characteristics
Temperature response functions (G-functions) for single pile heat exchangers
No full textFoundation piles used as heat exchangers as part of a ground energy system have the potential to reduce energy use and carbon dioxide emissions from new buildings. However, current design approaches for pile heat exchangers are based on methods developed for boreholes which have a different geometry, with a much larger aspect (length to diameter) ratio. Current methods also neglect the transient behaviour of the pile concrete, instead assuming a steady state resistance for design purposes. As piles have a much larger volume of concrete than boreholes, this neglects the significant potential for heat storage within the pile. To overcome these shortcomings this paper presents new pile temperature response functions (G-functions) which are designed to reflect typical geometries of pile heat exchangers and include the transient response of the pile concrete. Owing to the larger number of pile sizes and pipe configurations which are possible with pile heat exchangers it is not feasible to developed a single unified G-function and instead upper and lower bound solutions are provided for different aspects ratios
G-Functions for multiple interacting pile heat exchangers
No full textPile heat exchangers – where heat transfer pipes are cast into the building piled foundations – offer an opportunity to use ground energy systems without the additional construction costs related to the provision of special purpose heat exchangers. However, analysis methods for pile heat exchangers are still under development. In particular there is an absence of available methods and guidance for the amount of thermal interaction that may occur between adjacent pile heat exchangers and the corresponding reduction in available energy that this will cause. This is of particular importance as the locations of foundation piles are controlled by the structural demands of the building and cannot be optimised with respect to the thermal analysis. This paper presents a method for deriving G-functions for use with multiple pile heat exchangers. Example functions illustrate the primary importance of pile spacing in controlling available energy, followed by the number of piles within any given arrangement. Significantly it was found that the internal thermal behaviour of a pile is not influenced appreciably by adjacent piles
Comparison of two different models for pile thermal response test interpretation
No full textThermal response tests (TRTs) are regularly used to characterise the thermal resistance of borehole heat exchangers and to assess the thermal conductivity of the surrounding ground. It is becoming common to apply the same in situ testing technique to pile heat exchangers, despite international guidance suggesting that TRTs should be limited to hole diameters of 152 mm (6 in.). This size restriction arises from the increased thermal inertia of larger diameter heat exchangers, which invalidates the assumption of a steady state within the concrete needed to interpret the test data by traditional line source analysis techniques. However, new methods of analysis for pile heat exchangers have recently been developed that take account of the transient behaviour of the pile concrete. This paper applies these new methods to data from a multi-stage TRT conducted on a small diameter test pile. The thermal conductivity and thermal resistance determined using this method are then compared with those from traditional analytical approaches based on a line source analysis. Differences between the approaches are discussed, along with the observation that the thermal resistance may not be constant over the different test stages
Pile heat exchangers: thermal behaviour and interactions
No full textThermal piles – that is structural foundation piles also used as heat exchangers as part of a ground energy system – are increasingly being adopted for their contribution to more sustainable energy strategies for new buildings. Despite over a quarter of a century having passed since the installation of the first thermal piles in northern Europe, uncertainties regarding their behaviour remain. This paper identifies the key factors which influence the heat transfer and thermal–mechanical interactions of such piles. In terms of heat output, pile aspect ratio is identified as an important parameter controlling the overall thermal performance. Temperature changes in the concrete and surrounding ground during thermal pile operation will lead to additional concrete stresses and displacements within the pile–soil system. Consequently designers must ensure that temperatures remain within acceptable limits, while the pile geotechnical analysis should demonstrate that any adverse thermal stresses are within design safety factors and that any additional displacements do not affect the serviceability of the structur
Afroedura bogerti Loveridge 1944
No full textA. bogerti Loveridge 1944 (Fig. 3 B) Distribution. Namibe Province, Angola and adjacent northern Kaokoveld of northern Namibia (Branch 1998; Griffin 2003) (Fig. 4). Remarks. This distinctive species was originally described by Loveridge (1944) as A. karroica bogerti, and was only elevated to specific status by Onderstall (1984). Afroedura bogerti and A. karroica possess the diagnostic features of different species groups and are separated from one another by a disjunction of approximately 2000 km; that they were previously considered conspecific is illustrative of the fact that herpetologists were reluctant to erect new specific level taxa for geckos of this genus, presumably because of the their general morphological conservatism (Jacobsen 1997). Barts & Haacke (2010) provided data about reproduction in captivity.Published as part of Jacobsen, Niels H. G., Kuhn, Arianna L., Jackman, Todd R. & Bauer, Aaron M., 2014, A phylogenetic analysis of the southern African gecko genus Afroedura Loveridge (Squamata: Gekkonidae), with the description of nine new species from Limpopo and Mpumalanga provinces of South Africa, pp. 451-501 in Zootaxa 3846 (4) on page 467, DOI: 10.11646/zootaxa.3846.4.1, http://zenodo.org/record/25049
The thermal behaviour of three different auger pressure grouted piles used as heat exchangers
No full textThree auger pressure grouted (APG) test piles were constructed at a site in Richmond, Texas. The piles were each equipped with two U-loops of heat transfer pipes so that they could function as pile heat exchangers. The piles were of two different diameters and used two different grouts, a standard APG grout and a thermally enhanced grout. Thermal response tests, where fluid heated at a constant rate is circulated through the pipe loops, were carried out on the three piles, utilising either single or double loops. The resulting test data can be used to determine the surrounding soil thermal conductivity and the pile thermal resistance, both essential design parameters for ground source heat pump schemes using pile heat exchangers. This paper uses parameter estimation techniques to fit empirical temperature response curves to the thermal response test data and compares the results with standard line source interpretation techniques. As expected, the thermal response tests with double loops result in smaller thermal resistances than the same pile when the test was run with a single loop. Back analysis of the pile thermal resistance also allows calculation of the grout thermal properties. The thermally enhanced grout is shown to have inferior thermal properties than the standard APG grout. Together these analyses demonstrate the importance of pile size, grout thermal properties and pipe positions in controlling the thermal behaviour of heat exchanger piles
Supporting the development of number fact knowledge in five- and six-year-olds
No full textThis paper focuses on children’s number fact knowledge from a study that explored the impact of using multiplication and division contexts for developing number understanding with 34 five- and six-year-old children from diverse cultural and linguistic backgrounds. After a series of focused lessons, children’s knowledge of number facts, including single digit addition, subtraction, and doubles had improved. However, they did not always apply this knowledge to relevant problem-solving situations. The magnitude of the numbers did not necessarily determine the difficulty level for achieving automaticity of number fact knowledge
A new modelling approach for piled and other ground heat exchanger applications
No full textPile heat exchangers have an increasing role to play in the delivery of renewable heating and cooling energy. Traditionally the thermal design of ground heat exchangers has relied upon analytical approaches which take a relatively simple approach to the inside of the heat exchanger. This approach is justified while the heat exchanger diameter remains small. However, as larger diameter piled foundations are used as heat exchangers, the transient heat transfer processes operating within the pile become more important. To increase our understanding of these processes and ultimately lead to improved thermal design approaches for pile heat exchangers it is important to examine the heat transfer within the pile in detail. To accomplish this, a new numerical approach has been implemented within the finite element software ABAQUS. Coupling of the convective heat transfer due to fluid flow within the heat transfer pipes and the heat transfer by conduction within the pile concrete is the most important facet of the model. The resulting modelling approach, which is ready to generalise to other geothermal applications and to assess thermo-mechanical couplings, has been validated against a multi-stage thermal response test carried out on a test pile in London Clay
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