Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 11) Show all publications
Grenman, T., Gahm, G. F. & Elfgren, E. (2017). Dusty globules in the Crab Nebula. Astronomy and Astrophysics, 599, Article ID A110.
Open this publication in new window or tab >>Dusty globules in the Crab Nebula
2017 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 599, article id A110Article in journal (Refereed) Published
Abstract [en]

Context. Dust grains are widespread in the Crab Nebula. A number of small, dusty globules, are visible as dark spots against the background of continuous synchrotron emission in optical images. Aims. Our aim is to catalogue such dusty globules and investigate their properties. Methods. From existing broad-band images obtained with the Hubble Space Telescope, we located 92 globules, for which we derived positions, dimensions, orientations, extinctions, masses, proper motions, and their distributions. Results. The globules have mean radii ranging from 400 to 2000 AU and are not resolved in current infrared images of the nebula. The extinction law for dust grains in these globules matches a normal interstellar extinction law. Derived masses of dust range from 1 to 60 × 10-6M, and the total mass contained in globules constitute a fraction of approximately 2% or less of the total dust content of the nebula. The globules are spread over the outer part of the nebula, and a fraction of them coincide in position with emission filaments, where we find elongated globules that are aligned with these filaments. Only 10% of the globules are coincident in position with the numerous H2-emitting knots found in previous studies. All globules move outwards from the centre with transversal velocities of 60 to 1600 km s-1, along with the general expansion of the remnant. We discuss various hypotheses for the formation of globules in the Crab Nebula

Place, publisher, year, edition, pages
EDP Sciences, 2017
National Category
Other Physics Topics Energy Engineering
Research subject
Energy Engineering; Applied Physics
Identifiers
urn:nbn:se:ltu:diva-61736 (URN)10.1051/0004-6361/201629693 (DOI)000395821900088 ()2-s2.0-85015159073 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-03-24 (andbra)

Available from: 2017-01-31 Created: 2017-01-31 Last updated: 2018-11-20Bibliographically approved
Andersson, J.-O., Elfgren, E. & Westerlund, L. (2014). Improved energy efficiency in juice production through waste heat recycling (ed.). Paper presented at International Conference on Applied Energy : Energy Solution for a Sustainable World 01/07/2013 - 05/07/2013. Applied Energy, 130(S1), 757-763
Open this publication in new window or tab >>Improved energy efficiency in juice production through waste heat recycling
2014 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 130, no S1, p. 757-763Article in journal (Refereed) Published
Abstract [en]

Berry juice concentrate is produced by pressing berries and heating up the juice. The by-products are berry skins and seeds in a press cake. Traditionally, these by-products have been composted, but due to their valuable nutrients, it could be profitable to sell them instead. The skins and seeds need to be separated and dried to a moisture content of less than 10 %wt (on dry basis) in order to avoid fermentation. A berry juice plant in the north of Sweden has been studied in order to increase the energy and resource efficiency, with special focus on the drying system. This was done by means of process integration with mass and energy balance, theory from thermodynamics and psychrometry along with measurements of the juice plant. Our study indicates that the drying system could be operated at full capacity without any external heat supply using waste heat supplied from the juice plant. This would be achieved by increasing the efficiency of the dryer by recirculation of the drying air and by heat supply from the flue gases of the industrial boiler. The recirculation would decrease the need of heat in the dryer with about 52%. The total heat use for the plant could thereby be decreased from 1262 kW to 1145 kW. The improvements could be done without compromising the production quality.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-33065 (URN)10.1016/j.apenergy.2014.01.092 (DOI)000340311500076 ()2-s2.0-84904819243 (Scopus ID)7d43cecf-6d02-4fbb-bb80-e13b44ce5f5d (Local ID)7d43cecf-6d02-4fbb-bb80-e13b44ce5f5d (Archive number)7d43cecf-6d02-4fbb-bb80-e13b44ce5f5d (OAI)
Conference
International Conference on Applied Energy : Energy Solution for a Sustainable World 01/07/2013 - 05/07/2013
Note
Validerad; 2014; 20140310 (andbra); Konferensartikel i tidskriftAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-07-10Bibliographically approved
Andersson, J.-O., Elfgren, E. & Grip, C.-E. (2013). Improved energy efficiency in juice production through waste heat recycling (ed.). In: (Ed.), (Ed.), International Conference on Applied Energy, ICAE 2013: . Paper presented at International Conference on Applied Energy : Energy Solution for a Sustainable World 01/07/2013 - 05/07/2013.
Open this publication in new window or tab >>Improved energy efficiency in juice production through waste heat recycling
2013 (Swedish)In: International Conference on Applied Energy, ICAE 2013, 2013Conference paper, Published paper (Refereed)
Abstract [en]

The global demand for Nordic wild berries has increased steadily, partly due to their healthy properties and their good taste. Juice concentrate is produced by pressing berries and heating up the juice. The by-products are berry skins and seeds. Traditionally, the by-products have been composted. Higher competiveness can be achieved by decreasing the production cost and increasing the product values. The berry skins and seeds have a commercial value since they are rich in vitamins and nutrients. To use and sell these by-products, they need to be separated from each other and dried to a moisture content of less than 10 %wt. A berry juice industry in the north of Sweden has been studied in order to increase the energy and resource efficiency and optimize the quality and yield of different berry fractions. This was done by means of process integration with thermodynamics and psychrometry along with measurements of the berry juice production processes. Our calculations show that the drying system could be operated at full without any external heat supply. This could be achieved by increasing the efficiency of the dryer by recirculating 80 % of the drying air and by heating the air with heat from the flue gases from the industrial boiler. This change would decrease the need for heat in the dryer with about 64 %. The total heat use for the plant could thereby be decreased from 1204 kW to 1039 kW. The proposed changes could be done without compromising the production quality or the lead time.

Keywords
Natural sciences - Physics, renewable energy resources, psychrometrics, thermodynamic, drying, pinch analys, Naturvetenskap - Fysik
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-36993 (URN)add3b9bb-6da2-4d22-bfff-e78c64e19b15 (Local ID)add3b9bb-6da2-4d22-bfff-e78c64e19b15 (Archive number)add3b9bb-6da2-4d22-bfff-e78c64e19b15 (OAI)
Conference
International Conference on Applied Energy : Energy Solution for a Sustainable World 01/07/2013 - 05/07/2013
Note
Godkänd; 2013; Bibliografisk uppgift: Konferensbidrag, finns omskrivet till en journal artikel; 20130613 (janand)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-05-02Bibliographically approved
Elfgren, E., Grip, C.-E., Wang, C. & Karlsson, J. (2011). Exergy as a means for process integration in an integrated steel plant (ed.). Paper presented at International Conference on Energy Efficiency and CO2 Reduction in the Steel Industry : 27/06/2011 - 01/07/2011. Paper presented at International Conference on Energy Efficiency and CO2 Reduction in the Steel Industry : 27/06/2011 - 01/07/2011.
Open this publication in new window or tab >>Exergy as a means for process integration in an integrated steel plant
2011 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

The Luleå energy system consists of SSAB (an integrated steel plant) – LuleKraft (the heat and power plant) – Luleå Energi (the district heating network). The exergy flows in the whole system have been studied and some possibilities on how to reduce the exergy losses are discussed. The exergy thermal efficiency of SSAB, LuleKraft and Luleå Energi are 70 %, 40 % and 30 % respectively. The relatively low exergy thermal efficiencies is a natural consequence of converting high-value chemical energy into heating water. In the integrated steel plant, the exergy losses are caused by the cooling of the steel prior to transport. In the heat and power plant, exergy is destroyed mainly in the furnace. In the district heating, exergy is destroyed mainly by the customer. A preliminary conclusion is that a lot of exergy is destroyed and lost in order to produce hot water, which doesn’t really need so much exergy. By lowering the water temperature of the district heating, a larger portion of the exergy can be converted to high-value electricity. Mapping by combined Exergy/energy analysis is important to find ways to improve energy efficiency. It can also be important to initiate regional energy collaboration.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-35430 (URN)9f7e37f2-3b1e-40d7-aa02-45d37b8c7a05 (Local ID)9f7e37f2-3b1e-40d7-aa02-45d37b8c7a05 (Archive number)9f7e37f2-3b1e-40d7-aa02-45d37b8c7a05 (OAI)
Conference
International Conference on Energy Efficiency and CO2 Reduction in the Steel Industry : 27/06/2011 - 01/07/2011
Note
Godkänd; 2011; 20110920 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-02Bibliographically approved
Grip, C.-E., Elfgren, E., Söderström, M., Thollander, P., Berntsson, T., Åsblad, A. & Wang, C. (2011). Possibilities and problems in using exergy expressions in process integration (ed.). In: (Ed.), (Ed.), Proceedings of the World Renewable Energy Congress 2011 (WREC 2011): 9-13 May, Linköping. Paper presented at World Renewable Energy Congress : 09/05/2011 - 13/05/2011. Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Possibilities and problems in using exergy expressions in process integration
Show others...
2011 (English)In: Proceedings of the World Renewable Energy Congress 2011 (WREC 2011): 9-13 May, Linköping, Linköping: Linköping University Electronic Press, 2011Conference paper, Published paper (Refereed)
Abstract [en]

Industrial energy systems are complicated networks, where changes in one process influence its neighboring processes. Saving energy in one unit does not necessarily lead to energy savings for the total system. A study has been carried out on the possibility to use the exergy concept in the analysis of industrial energy systems. The exergy concept defines the quality of an amount of energy in relation to its surrounding, expressing the part that could be converted into work. The study consists of literature studies and general evaluations, an extensive case study and an interview study. In the latter it was found that non technical factors are major obstacles to the introduction of exergy.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011
National Category
Energy Engineering Other Physics Topics
Research subject
Energy Engineering; Fysik
Identifiers
urn:nbn:se:ltu:diva-35508 (URN)a0f7e999-8424-4b61-9162-b9ec562c54f8 (Local ID)a0f7e999-8424-4b61-9162-b9ec562c54f8 (Archive number)a0f7e999-8424-4b61-9162-b9ec562c54f8 (OAI)
Conference
World Renewable Energy Congress : 09/05/2011 - 13/05/2011
Note
Godkänd; 2011; 20110914 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-02Bibliographically approved
Elfgren, E., Grip, C.-E., Wang, C. & Karlsson, J. (2010). Possibility to combine exergy with other process integration methods for a steelmaking case (ed.). In: (Ed.), Jirí J. Klemeš; Hon Loong Lam; Petar S. Varbanov (Ed.), PRES 2010, 13th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction: . Paper presented at Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction : 28/08/2010 - 01/09/2010 (pp. 1375-1380). : AIDIC Servizi S.r.l.
Open this publication in new window or tab >>Possibility to combine exergy with other process integration methods for a steelmaking case
2010 (English)In: PRES 2010, 13th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction / [ed] Jirí J. Klemeš; Hon Loong Lam; Petar S. Varbanov, AIDIC Servizi S.r.l. , 2010, p. 1375-1380Conference paper, Published paper (Refereed)
Abstract [en]

The energy system of Luleå consists of the steel plant, a local CHP using process gases from the plant and the district heating system. Process integration work to improve the efficiency of the system is presently carried out by mathematical programming using a MILP tool (reMIND). Further improvements would need an improved possibility of the tool to consider the thermodynamic quality of the energy flows. This project aims to include exergy parameters in the node equations and object functions. This has been carried out for a test case, including a part of the system. Programming principles and some results are described.

Place, publisher, year, edition, pages
AIDIC Servizi S.r.l., 2010
Series
Chemical Engineering Transactions, ISSN 1974-9791 ; 21
Keywords
Energy efficiency, Process integration, Exergy, MILP, Mathematical programming, Process industry, Engineering mechanics - Mechanical and thermal engineering, Energieffektivitet, Process integration, Exergi, MILP, Matematisk programmering, Processindustri, Teknisk mekanik - Mekanisk och termisk energiteknik
National Category
Other Physics Topics Energy Engineering
Research subject
Fysik; Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-29714 (URN)10.3303/CET1021230 (DOI)000286978600230 ()78650270586 (Scopus ID)344f5a10-073d-11e0-b767-000ea68e967b (Local ID)978-88-95608-05-1 (ISBN)344f5a10-073d-11e0-b767-000ea68e967b (Archive number)344f5a10-073d-11e0-b767-000ea68e967b (OAI)
Conference
Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction : 28/08/2010 - 01/09/2010
Note
Validerad; 2010; 20110209 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-07-10Bibliographically approved
Elfgren, E. & Fredriksson, S. (2008). Mass limits for heavy neutrinos (ed.). Paper presented at . Astronomy and Astrophysics, 479(2), 347-353
Open this publication in new window or tab >>Mass limits for heavy neutrinos
2008 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 479, no 2, p. 347-353Article in journal (Refereed) Published
Abstract [en]

Context. Neutrinos heavier than MZ/2 ∼ 45 GeV are not excluded by particle physics data. Stable neutrinos heavier than this might contribute to the cosmic gamma ray background through annihilation in distant galaxies, as well as to the dark matter content of the universe.Aims. We calculate the evolution of the heavy neutrino density in the universe as a function of its mass, MN, and then the subsequent gamma ray spectrum from annihilation of distant N ¯N (from 0 < z < 5).Methods. The evolution of the heavy neutrino density in the universe is calculated numerically. To obtain the enhancement due to structure formation in the universe, we approximate the distribution of N to be proportional to that of dark matter in the GalICS model. The calculated gamma ray spectrum is compared to the measured EGRET data.Results. A conservative exclusion region for the heavy neutrino mass is 100 to 200 GeV, both fromEGRET data and our re-evalutation of the Kamiokande data. The heavy neutrino contribution to dark matter is found to be at most 15%.

National Category
Other Physics Topics
Research subject
Fysik
Identifiers
urn:nbn:se:ltu:diva-8956 (URN)10.1051/0004-6361:20078898 (DOI)000253039600009 ()2-s2.0-39049114947 (Scopus ID)783538a0-be05-11dc-a8ca-000ea68e967b (Local ID)783538a0-be05-11dc-a8ca-000ea68e967b (Archive number)783538a0-be05-11dc-a8ca-000ea68e967b (OAI)
Note
Validerad; 2008; 20080108 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Elfgren, E. (2007). Cosmic dust and heavy neutrinos (ed.). (Doctoral dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Cosmic dust and heavy neutrinos
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This Doctoral thesis treats two subjects. The first subject is the impact of early dust on the cosmic microwave background (CMB). The dust that is studied comes from the first generation of stars, which were hot and short-lived, ending their lives as giant supernovae. In the supernova explosions, heavy elements, produced through the fusion in the stars, were ejected into the interstellar medium. These heavy elements condensed to form dust, which can absorb and thus perturb the CMB radiation. The dust contribution to this radiation is calculated and found negligible. However, since the dust is produced within structures (like galaxy clusters), it will have a spatial correlation that could be used to detect it. This correlation is calculated with relevant assumptions. The planned Planck satellite could eventually detect and thus confirm this correlation. The second subject is heavy neutrinos and their impact on the diffuse gamma ray background. Neutrinos heavier than M_Z /2 ~ 45 GeV are not excluded by particle physics data. Stable neutrinos heavier than this might contribute to the cosmic gamma ray background through annihilation in distant galaxies as well as to the dark matter content of the universe. The evolution of the heavy neutrino density in the universe is calculated as a function of its mass, M_N, and then the subsequent gamma ray spectrum from annihilation of distant N-Nbar (from 0 < z < 5). The evolution of the heavy neutrino density in the universe is calculated numerically. In order to obtain the enhancement due to structure formation in the universe, the distribution of N is approximated to be proportional to that of dark matter in the GalICS model. The calculated gamma ray spectrum is compared to the measured EGRET data. A conservative exclusion region for the heavy neutrino mass is 100 to 200 GeV, both from EGRET data and our re-evalutation of the Kamiokande data. The heavy neutrino contribution to dark matter is found to be at most 15%. Finally, heavy neutrinos are considered within the context of a preon model for composite leptons and quarks, where such particles are natural. The consequences of these are discussed, with emphasis on existing data from the particle accelerator LEP at CERN. A numerical method for optimizing variable cuts in particle physics is also included in the thesis.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2007. p. 69
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544 ; 2007:75
National Category
Other Physics Topics
Research subject
Fysik
Identifiers
urn:nbn:se:ltu:diva-25662 (URN)a6e5b1d0-be04-11dc-a8ca-000ea68e967b (Local ID)a6e5b1d0-be04-11dc-a8ca-000ea68e967b (Archive number)a6e5b1d0-be04-11dc-a8ca-000ea68e967b (OAI)
Note
Godkänd; 2007; 20080108 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-02Bibliographically approved
Elfgren, E., Désert, F.-X. & Guiderdoni, B. (2007). Dust distribution during reionization (ed.). Paper presented at . Astronomy and Astrophysics, 476, 1145-1150
Open this publication in new window or tab >>Dust distribution during reionization
2007 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 476, p. 1145-1150Article in journal (Refereed) Published
Abstract [en]

Context. The dust produced by the first generation of stars will be a foreground to cosmic microwave background.Aims. In order to evaluate the effect of this early dust, we calculate the power spectrum of the dust emission anisotropies and compare it with the sensitivity limit of the Planck satellite.Methods. The spatial distribution of the dust is estimated through the distribution of dark matter.Results. At small angular scales l ≥ 1000 the dust signal is found to be noticeable with the Planck detector for certain values of dust lifetime and production rates. The dust signal is also compared to sensitivities of other instruments. The early dust emission anisotropies are finally compared to those of local dustand they are found to be similar in magnitude at mm wavelengths.

National Category
Other Physics Topics
Research subject
Fysik
Identifiers
urn:nbn:se:ltu:diva-8211 (URN)10.1051/0004-6361:20053151 (DOI)000251507500010 ()2-s2.0-38049181032 (Scopus ID)6aed5540-a42b-11dc-8fee-000ea68e967b (Local ID)6aed5540-a42b-11dc-8fee-000ea68e967b (Archive number)6aed5540-a42b-11dc-8fee-000ea68e967b (OAI)
Note
Validerad; 2007; 20071206 (elf)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Elfgren, E. (2005). Dust in the early universe (ed.). (Licentiate dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Dust in the early universe
2005 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This Licentiate thesis treats the impact of early dust on the Cosmic Microwave Background (CMB). The dust that is studied comes from the first generation of stars, which were hot and short-lived, ending their lives as giant supernovæ. In the supernova explosions, heavy elements, produced through the fusion in the stars, were ejected into the interstellar medium. These heavy elements condensed to form dust, which can absorb and thus perturb the Cosmic Microwave Background radiation. The dust contribution to this radiation is calculated and found negligible. However, as the dust will be produced within structures (like galaxy clusters), it will have a spatial correlation that could be used to detect it. This correlation is calculated using relevant assumptions. The planned Planck satellite is likely to be able to measure and thus confirm this correlation.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2005. p. 31
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757 ; 2005:17
National Category
Other Physics Topics
Research subject
Fysik
Identifiers
urn:nbn:se:ltu:diva-26244 (URN)d4d3f020-70c1-11db-962b-000ea68e967b (Local ID)d4d3f020-70c1-11db-962b-000ea68e967b (Archive number)d4d3f020-70c1-11db-962b-000ea68e967b (OAI)
Note
Godkänd; 2005; 20061110 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-02Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-4400-3276

Search in DiVA

Show all publications