3,236 research outputs found
A radial model for fast analysis of thermal pile heat exchangers
No full textEnergy piles offer an effective way to decarbonise heating and cooling via exchange of heat through the deep foundations of a building or other structure. However, efficient analysis methods are required to allow energy performance to be determined in a way compatible with building energy design and energy system design approaches. We test a fast run time analytical model (the Claesson-Javed radial model) that retains a physical basis linked to the energy pile geometry, while making simplifications to permit a radial approximation to be used. We also present validation G-functions from the model development processes that have been derived from 2D and 3D numerical simulation.</span
Evaluating the applicability of the radial approximation for pile heat exchangers
No full textThis paper appraises the efficacy of using an analytical radial approximation for different thermal pile heat exchanger geometries. Unsteady radial heat-flow from fluid in a pipe set within a grouted borehole into the external ground is well-documented and can be solved analytically very rapidly using Laplace Transforms (Javed and Claesson 2011). By comparing the radial model with finite-element simulations including explicit pile geometries, this paper provides a provisional analysis of the accuracy of this approach. Initial findings suggest that the radial model may provide an appropriate approximation to pile behaviour for certain pipe configurations, albeit with small ‘mid-time’ error
Optimal distribution of thermal insulation and ground heat losses /Johan Claesson, Bengt Eftring
No full textHeat extraction from the ground by horizontal pipes :a mathematical analysis /Johan Claesson, Alain Dunand
No full textA fast approximate method for simulating thermal pile heat exchangers
No full textGround source heat pump systems, operating in conjunction with vertical ground heat exchangers, will play a key role in decarbonising heating and cooling of buildings. Design of traditional borehole heat exchangers relies on tools which implement routine analytical relationships between heat transferred and the temperature change in the ground and circulating thermal fluid. However, for novel piled foundations used as ground heat exchangers, there are few such analytical solutions available that are practical for routine implementation. This paper examines the use of a radial approximation to simulate the dynamic thermal behaviour of pile heat-exchangers. Originally developed for small diameter and high aspect ratio borehole heat exchangers, the approach is more challenging for piles since unsteady heat transfer within the pile material is more significant over typical timescales. Nonetheless, we demonstrate that for pile diameters between 300 mm and 1200 mm, generally the error is <1 °C with centrally placed heat transfer pipes or four or more pipes placed near the edge with circumferential spacing less than 550 mm. The radial model is therefore practical for most pile configurations. The strong performance of the model is demonstrated for a year of hypothetical heating and cooling cycles, and also against a field-scale thermal response test
Report of Governor Johan Rising, 1655, on New Sweden
No full textGovernor Johan Rising reports to the Swedish government and royalty on the status of New Sweden (present-day New Jersey). He also reports on other Swedish colonies in the area. He asks that single women and skilled tradesmen be sent to the colonies. Rising also reports that attacks from neighboring Indian tribes are increasing. He has found some protection by forming an alliance with English settlers, but the cost is high, and his colony owes the English money and supplies. Rising asks that Sweden send them money so that they can pay off their debts, build ships that would establish a trading dominance with the West Indies, and cultivate land and crops to gain more profit. Reports from New World governors were sent back to their native countries via ships. Rising sent this report in June of 1655, but Sweden did not recieve the report until November of 1655. This article is part of a Primary Source Material collection compiled by the New Sweden Commemorative Commission in 1988
Report of Governor Johan Printz, 1647, on New Sweden
No full textGovern Johan Printz, the governor of New Sweden (later to become New Jersey), reports on the status of the colony and the settlers. Many freemen have arrived to settle in New Sweden, but the criminals and military men who were conscripted to the colony want to return to Sweden. Of the freemen, very few are skilled, so Governor Printz asks that blacksmiths, tanners, tailors, carpenters, and butchers be sent to the colony. Additionally, he asks for single women. Printz also reports on two new Swedish colonies that have been established along the Delaware River. However, Dutch settlers have become very aggressive by re-purchasing land from the Indians that the Swedish had already bought. They are also interrupting trade between the Swedes and the Indians, as well as instigating the Indians to attack the Swedes. Printz directed the construction of some storage houses along common trade routes to win back trade from the Indians. However, fighting has erupted between different Native tribes as each tries to establish dominance in trading with the colonies. This article is part of a Primary Source Material collection compiled by the New Sweden Commemorative Commission in 1988
Relation of the surrender of New Sweden, by Governor Johan Clason Rising, 1655
No full textGovernor Johan Rising of New Sweden reports to Sweden on the August 1655 Dutch attack on New Sweden's Fort Christina. The Dutch traveled from New Amsterdam (present-day New York) and easily captured a New Sweden outpost. Rising sent men to the outpost to fend of the Dutch, but the Dutch defeated them and took them as prisoners, leaving Fort Christina without fighting men and supplies. The Dutch then put the Fort under seige. A few days later, Rising surrendered the Fort. He and the Swedish colonists were ordered to either return to Sweden, or to remain in the New World in service to the Dutch. This article is part of a Primary Source Material collection compiled by the New Sweden Commemorative Commission in 1988
The past, present and future of social media in project management
No full textGreen Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Integral Design & Managemen
An operationalization of Stevenson’s conceptualization of entrepreneurship as opportunity-based firm behavior
No full textThis is the author-version of article published as: Brown, Terrence and Davidsson, Per and Wiklund, Johan (2001) An operationalization of Stevenson’s conceptualization of entrepreneurship as opportunity-based firm behavior. Strategi
- …
