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| 2. |
- Acuña, José, 1982-
(författare)
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Distributed thermal response tests : New insights on U-pipe and Coaxial heat exchangers in groundwater-filled boreholes
- 2013
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- U-pipe Borehole Heat Exchangers (BHE) are widely used today in ground source heating and cooling systems in spite of their less than optimal performance. This thesis provides a better understanding on the function of U-pipe BHEs and Investigates alternative methods to reduce the temperature difference between the circulating fluid and the borehole wall, including one thermosyphon and three different types of coaxial BHEs.Field tests are performed using distributed temperature measurements along U-pipe and coaxial heat exchangers installed in groundwater filled boreholes. The measurements are carried out during heat injection thermal response tests and during short heat extraction periods using heat pumps. Temperatures are measured inside the secondary fluid path, in the groundwater, and at the borehole wall. These type of temperature measurements were until now missing.A new method for testing borehole heat exchangers, Distributed Thermal Response Test (DTRT), has been proposed and demonstrated in U-pipe, pipe-in-pipe, and multi-pipe BHE designs. The method allows the quantification of the BHE performance at a local level.The operation of a U-pipe thermosyphon BHE consisting of an insulated down-comer and a larger riser pipe using CO2 as a secondary fluid has been demonstrated in a groundwater filled borehole, 70 m deep. It was found that the CO2 may be sub-cooled at the bottom and that it flows upwards through the riser in liquid state until about 30 m depth, where it starts to evaporate.Various power levels and different volumetric flow rates have been imposed to the tested BHEs and used to calculate local ground thermal conductivities and thermal resistances. The local ground thermal conductivities, preferably evaluated at thermal recovery conditions during DTRTs, were found to vary with depth. Local and effective borehole thermal resistances in most heat exchangers have been calculated, and their differences have been discussed in an effort to suggest better methods for interpretation of data from field tests.Large thermal shunt flow between down- and up-going flow channels was identified in all heat exchanger types, particularly at low volumetric flow rates, except in a multi-pipe BHE having an insulated central pipe where the thermal contact between down- and up-coming fluid was almost eliminated.At relatively high volumetric flow rates, U-pipe BHEs show a nearly even distribution of the heat transfer between the ground and the secondary fluid along the depth. The same applies to all coaxial BHEs as long as the flow travels downwards through the central pipe. In the opposite flow direction, an uneven power distribution was measured in multi-chamber and multi-pipe BHEs.Pipe-in-pipe and multi-pipe coaxial heat exchangers show significantly lower local borehole resistances than U-pipes, ranging in average between 0.015 and 0.040 Km/W. These heat exchangers can significantly decrease the temperature difference between the secondary fluid and the ground and may allow the use of plain water as secondary fluid, an alternative to typical antifreeze aqueous solutions. The latter was demonstrated in a pipe-in-pipe BHE having an effective resistance of about 0.030 Km/W.Forced convection in the groundwater achieved by injecting nitrogen bubbles was found to reduce the local thermal resistance in U-pipe BHEs by about 30% during heat injection conditions. The temperatures inside the groundwater are homogenized while injecting the N2, and no radial temperature gradients are then identified. The fluid to groundwater thermal resistance during forced convection was measured to be 0.036 Km/W. This resistance varied between this value and 0.072 Km/W during natural convection conditions in the groundwater, being highest during heat pump operation at temperatures close to the water density maximum.
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| 3. |
- af Ekström, Hanna, 1981, et al.
(författare)
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NORM-CRITIQUE IN PRACTICE: HAPTIC AND TACTILE DESIGN METHODS IN THE NOTION OF CARE
- 2019
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Ingår i: Nordes design conference, Aalto University, Helsinki, Finland.
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- We invite participants to this workshop with the purpose to explore participatory processes based on tactile and haptic methods within the framework of norm-critical methodology. The workshop is based on cases from the project ‘Tink – Idea development for available and inclusive open stormwater solutions`. Innovation- driven projects in urban planning are often based on technical aspects and deviate from social values. Through a norm-critical methodology, we argue that technical innovation needs to include social values based on intersectional analysis. Firstly, in the project Tink, that means that we work together across disciplines and focus areas, in an interdisciplinary environment with disability activists, researchers, practitioners, and municipal officials. Secondly, we state that norm critical methodology includes design processes based on inclusive methods in the notion of care, engagement and social inclusion. In a workshop environment, this means creating settings for people with different experiences and abilities.
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| 4. |
- af Ekström, Hanna, 1981
(författare)
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Norm Form
- 2017
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Ingår i: 6 Okt 2017 – 11 Feb 2018, ArkDes, Stockholm, Sweden.
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- Norm Form är en utställning om design som sätter sig på tvären och utmanar det som anses vara normalt. Denna banbrytande utställning innehåller verk av ett femtiotal formgivare som avslöjar de dolda budskap som föremål omkring oss förmedlar och ger dig verktyg för att undergräva dem. Utställningen är en spegling av en stark rörelse bland formgivare att arbeta normutmanande, en rörelse som har rötter i kritisk design och aktivism.
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| 6. |
- Ahl, Zandra, 1975-
(författare)
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På andra sidan lera
- 2015
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Ingår i: Konsthantverk i Sverige del 1. - Tumba : Mångkulturellt centrum. - 9789186429409 ; , s. 149-157
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Ahmed, Ashraf Awadelkarim Widaa, et al.
(författare)
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The Incentives and Challenges of Delivering Linear Broadcasting Services over Cellular Network in Developing Countries : Sudan as Case study
- 2014
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Ingår i: The 25th European Regional Conference of the International Telecommunications Society,Brussels, Belgium, 22nd - 25th June 2014. - Brussels : nternational Telecommunications Society.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Broadcasting sector has been evolved in terms of service production, transmission platform and reception devices in the last few decades. In contrast to cable and satellite platform, which are suitable for fixed reception only, the terrestrial digital platform can support portable, mobile and fixed reception scenarios. In general, there are two options of mobile multimedia service; one is based on a mobile communication network with IP cast known as MBMS (Multimedia Broadcast Multicast Services), while the other is based on broadcast technology. In the context of convergence, the players in the mobile sector argues that unlike traditional mobile network systems, where the use was restricted to a given application, emerging mobile networks will be able to carry a variety of services and accordingly separate broadcasting networks will no longer be required. In line with argument, it is not economically viable to roll out dedicated wireless broadband networks by the broadcasters to meet the increasing demand for interactive broadcasting services. That is why the broadcasters may look for innovative mechanism to deliver the broadcast services over mobile broadband network owned by the telecommunication operators.The focus on this paper is to investigate the incentives and challenges for such trend in developing countries; taking Sudan as case study. The main conclusion in this paper indicate that a potential economic incentive for delivering the broadcasting service over cellular network in Sudan subject to the deployment of high efficient mobile network. Moreover, the mobile operators may consider support such approach considering the increase demand for additional frequency resource. However, the key challenges remain in how to develop a suitable regulations landscape to assure fair and competitive business practices on hand while guaranteeing the continuation of the public broadcasting service. In this regard, a new regulation framework needs to be developed to separate the three key functions in digital terrestrial broadcasting value chain (namely the content production and distribution). Further on, the necessary interconnection regulations need to put on place in order to pave the way for rollout of common platform that are necessary for interactive and nonlinear services.
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| 9. |
- Akner-Koler, Cheryl
(författare)
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A Note on Nano (FormGiving)
- 2015. - 1 uppl.
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Ingår i: Radical Re Re Re Re Re Rethinking. - Stockholm : Konstfack. - 9789185549139 ; , s. 128-133
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Akner-Koler, Cheryl, et al.
(författare)
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Aesthetics and nanostructure
- 2011
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Ingår i: International Innovation. - : Research Media. - 2041-4552. ; :6, s. 97-97
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Professors Cheryl Akner-Kohler and Lena Tibell of the Nanoform project describe the artistic methods and benefits that it might afford to both science and society.
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