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Hellström, Göran
Publications (10 of 57) Show all publications
Gustafsson, A.-M., Westerlund, L. & Hellström, G. (2010). CFD-modelling of natural convection in a groundwater-filled borehole heat exchanger (ed.). Paper presented at . Applied Thermal Engineering, 30(6-7), 683-691
Open this publication in new window or tab >>CFD-modelling of natural convection in a groundwater-filled borehole heat exchanger
2010 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 30, no 6-7, p. 683-691Article in journal (Refereed) Published
Abstract [en]

In design of ground-source energy systems the thermal erformance of the borehole heat exchangers is important. In Scandinavia, boreholes are usually not grouted but left with groundwater to fill the space between heat exchanger pipes and borehole wall. The common U-pipe arrangement in a groundwater-filled BHE has been studied by a three-dimensional, steady-state CFD model. The model consists of a three meter long borehole containing a single U-pipe with surrounding bedrock. A constant temperature is imposed on the U-pipe wall and the outer bedrock wall is held at a lower constant temperature. The occurring temperature gradient induces a velocity flow in the groundwater-filled borehole due to density differences. This increases the heat transfer compared to stagnant water. The numerical model agrees well with theoretical studies and laboratory experiments. The result shows that the induced natural convective heat flow significantly decreases the thermal resistance in the borehole. The density gradient in the borehole is a result of the heat transfer rate and the mean temperature level in the borehole water. Therefore in calculations of the thermal resistance in groundwater filled boreholes convective heat flow should be included and the actual injection heat transfer rate and mean borehole temperature should be considered.

National Category
Water Engineering Energy Engineering
Research subject
Urban Water Engineering; Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-9606 (URN)10.1016/j.applthermaleng.2009.11.016 (DOI)000275976600019 ()2-s2.0-76449084925 (Scopus ID)842c8080-ddbd-11de-bae5-000ea68e967b (Local ID)842c8080-ddbd-11de-bae5-000ea68e967b (Archive number)842c8080-ddbd-11de-bae5-000ea68e967b (OAI)
Note
Validerad; 2010; 20091130 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Kjellsson, E., Hellström, G. & Perers, B. (2009). Analyses of ground-source heat pumps combined with solarcollectors in dwellings (ed.). In: (Ed.), Signhild Gehlin (Ed.), Abstract book and proceeding : Effstock 2009: 11th International conference on Thermal Energy Storage for Energy Efficiency and Sustainability. Paper presented at International Conference on Thermal Energy Storage : 14/06/2009 - 17/06/2009. Stockholm: Energi- och Miljötekniska Föreningen / EMTF Förlag
Open this publication in new window or tab >>Analyses of ground-source heat pumps combined with solarcollectors in dwellings
2009 (English)In: Abstract book and proceeding : Effstock 2009: 11th International conference on Thermal Energy Storage for Energy Efficiency and Sustainability / [ed] Signhild Gehlin, Stockholm: Energi- och Miljötekniska Föreningen / EMTF Förlag , 2009Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Stockholm: Energi- och Miljötekniska Föreningen / EMTF Förlag, 2009
National Category
Water Engineering
Research subject
Water Resources Engineering
Identifiers
urn:nbn:se:ltu:diva-39613 (URN)e711b080-e4c5-11de-bae5-000ea68e967b (Local ID)e711b080-e4c5-11de-bae5-000ea68e967b (Archive number)e711b080-e4c5-11de-bae5-000ea68e967b (OAI)
Conference
International Conference on Thermal Energy Storage : 14/06/2009 - 17/06/2009
Note

Godkänd; 2009; 20091209 (andbra)

Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2019-10-10Bibliographically approved
Kjellsson, E., Hellström, G. & Perers, B. (2009). Optimization of systems with the combination of ground-source heat pump and solar collectors in dwellings (ed.). Paper presented at . Energy
Open this publication in new window or tab >>Optimization of systems with the combination of ground-source heat pump and solar collectors in dwellings
2009 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785Article in journal (Refereed) Published
Abstract [en]

The use of ground-source heat pumps for heating and domestic hot water in dwellings is common in Sweden. The combination with solar collectors has been introduced to reduce the electricity demand in the system. In order to analyze different systems with combinations of solar collectors and ground-source heat pumps, computer simulations have been carried out with the simulation program TRNSYS. Large differences were found between the system alternatives. The optimal design is when solar heat produces domestic hot water during summertime and recharges the borehole during wintertime. The advantage is related to the rate of heat extraction from the borehole as well as the overall design of the system. The demand of electricity may increase with solar recharging, because of the increased operating time of the circulation pumps. Another advantage with solar heat in combination with heat pumps is when the boreholes or neighbouring installations are drilled so close that they thermally influence each other. This may lead to decreasing temperatures in the ground, which gives decreased performance of the heat pump and increased use of electricity. The net annual heat extraction from the ground is reduced by recharge from solar heat. © 2009 Elsevier Ltd. All rights reserved.

National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-3655 (URN)10.1016/j.energy.2009.04.011 (DOI)178ae6e0-7c3a-11de-8da0-000ea68e967b (Local ID)178ae6e0-7c3a-11de-8da0-000ea68e967b (Archive number)178ae6e0-7c3a-11de-8da0-000ea68e967b (OAI)
Note
Upprättat; 2009; 20090729 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Hellström, G. & Gehlin, S. (2008). Borrhålet och dess funktion: universitets- och högskoleforskning (ed.). Energi och miljö (1), 55-56
Open this publication in new window or tab >>Borrhålet och dess funktion: universitets- och högskoleforskning
2008 (Swedish)In: Energi och miljö, ISSN 1101-0568, no 1, p. 55-56Article in journal (Other academic) Published
National Category
Water Engineering
Research subject
Water Resources Engineering
Identifiers
urn:nbn:se:ltu:diva-11252 (URN)a2de0df0-bd39-11dd-a7c4-000ea68e967b (Local ID)a2de0df0-bd39-11dd-a7c4-000ea68e967b (Archive number)a2de0df0-bd39-11dd-a7c4-000ea68e967b (OAI)
Note

Godkänd; 2000; 20081128 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-03-14Bibliographically approved
Nordell, B. & Hellström, G. (2004). Bergvärme - den nya folkrörelsen (ed.). Paper presented at . Miljöforskning : Formas tidning : för ett uthålligt samhälle (5-6), 27-28
Open this publication in new window or tab >>Bergvärme - den nya folkrörelsen
2004 (Swedish)In: Miljöforskning : Formas tidning : för ett uthålligt samhälle, ISSN 1650-4925, no 5-6, p. 27-28Article in journal (Other (popular science, discussion, etc.)) Published
National Category
Water Engineering Water Engineering
Research subject
Water Resources Engineering; Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-9807 (URN)87dfd6d0-b85b-11db-abff-000ea68e967b (Local ID)87dfd6d0-b85b-11db-abff-000ea68e967b (Archive number)87dfd6d0-b85b-11db-abff-000ea68e967b (OAI)
Note
Godkänd; 2004; 20070209 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Lund, J., Sanner, B., Rybach, L., Curtis, R. & Hellström, G. (2004). Geothermal (ground-source) heat pumps: a world overview (ed.). Paper presented at . Geo-Heat Center Quarterly Bulletin, 25(3)
Open this publication in new window or tab >>Geothermal (ground-source) heat pumps: a world overview
Show others...
2004 (English)In: Geo-Heat Center Quarterly Bulletin, ISSN 0276-1084, Vol. 25, no 3Article in journal (Other academic) Published
National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-11784 (URN)accaa450-96c8-11dd-aadc-000ea68e967b (Local ID)accaa450-96c8-11dd-aadc-000ea68e967b (Archive number)accaa450-96c8-11dd-aadc-000ea68e967b (OAI)
Note
Upprättat; 2004; 20081010 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Nordell, B. & Hellström, G. (2004). Spillvärme gör flygplatsen snöfri (ed.). Paper presented at . Miljöforskning : Formas tidning : för ett uthålligt samhälle (5-6), 38
Open this publication in new window or tab >>Spillvärme gör flygplatsen snöfri
2004 (Swedish)In: Miljöforskning : Formas tidning : för ett uthålligt samhälle, ISSN 1650-4925, no 5-6, p. 38-Article in journal (Other (popular science, discussion, etc.)) Published
Keywords
Civil engineering and architecture - Building engineering, Samhällsbyggnadsteknik och arkitektur - Byggnadsteknik
National Category
Water Engineering
Research subject
Water Resources Engineering
Identifiers
urn:nbn:se:ltu:diva-14565 (URN)df37ea80-b85b-11db-abff-000ea68e967b (Local ID)df37ea80-b85b-11db-abff-000ea68e967b (Archive number)df37ea80-b85b-11db-abff-000ea68e967b (OAI)
Note
Godkänd; 2004; 20070209 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Gehlin, S. & Hellström, G. (2003). Comparison of four models for thermal response test evaluation (ed.). Paper presented at . ASHRAE Transactions, 109, 135-146
Open this publication in new window or tab >>Comparison of four models for thermal response test evaluation
2003 (English)In: ASHRAE Transactions, ISSN 0001-2505, Vol. 109, p. 135-146Article in journal (Refereed) Published
Abstract [en]

Four two-variable parameter estimation models for evaluation of thermal response test data are compared when applied on the same temperature response data. Two models are based on line-source theory, the third model is a cylinder-source-based solution, and the fourth is a numerical one-dimensional finite difference model. The data sets contain measured temperature response, heat load, and undisturbed ground temperature from three thermal response tests, together with physical data of the tested borehole heat exchangers (BHE). The models estimate ground thermal conductivity and thermal resistance of the BHE and are compared regarding test length and data interval used. For the three defined data sets, the line source approximation model shows the closest agreement with the measured temperature response. The cylinder source and numerical models show sensitivity to the inclusion of early data. A recommended minimum response test duration of 50 hours is concluded from the model comparison

National Category
Water Engineering
Research subject
Water Resources Engineering
Identifiers
urn:nbn:se:ltu:diva-15311 (URN)eceb4500-f04a-11dc-ba03-000ea68e967b (Local ID)eceb4500-f04a-11dc-ba03-000ea68e967b (Archive number)eceb4500-f04a-11dc-ba03-000ea68e967b (OAI)
Note
Validerad; 2003; 20080312 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Andersson, O., Hellström, G. & Nordell, B. (2003). Heating and cooling with UTES in Sweden: current situation and potential market development (ed.). In: (Ed.), (Ed.), Proceedings: Futurestock 2003, 9th International Conference on Thermal Energy Storage : Warsaw, Poland, September 1 - 4, 2003. Paper presented at International Conference on Thermal Energy Storage : 01/09/2003 - 04/09/2003 (pp. 207-215). Warszawa: PW Publishing House
Open this publication in new window or tab >>Heating and cooling with UTES in Sweden: current situation and potential market development
2003 (English)In: Proceedings: Futurestock 2003, 9th International Conference on Thermal Energy Storage : Warsaw, Poland, September 1 - 4, 2003, Warszawa: PW Publishing House , 2003, p. 207-215Conference paper, Published paper (Refereed)
Abstract [en]

Underground Thermal Energy Storage (UTES) applications have slowly gained acceptance on the Swedish energy market. Two UTES concepts are successfully implemented; the ATES (aquifer storage) and the BTES (borehole storage) systems. Also snow storage in pits or caverns has reached a commercial status. The number of ATES has steadily grown to 40 large-scale plants at the end of 2002. The systems are usually designed for cold storage in district cooling application, but industrial process cooling is also common. The economical potential in terms of straight payback time is usually very favourable. However, there is still a certain risk for operational problems that might jeopardize the calculated profit. Well clogging problems and system control remain as R&D issues to be solved. From a legislation point of view any ATES application needs a permit. The process of obtaining a permit has become complex and time-consuming since a new act on environmental assessment was put into effect in 1999.BTES systems are normally used in smaller applications. At the end of 2002 there were more than 200 installations comprising more than 10 boreholes. The majority of these are applied for space cooling of commercial or institutional buildings and for process cooling within the telecommunication sector. From a technical point of view, BTES are much simpler to construct and operate than ATES. Furthermore, they can be applied in almost any kind of geology. Another advantage compared to ATES is that the permitting procedure is much simpler. The major market obstacle is that the profitability is not always acceptable if calculated as a straight payback time. To increase the market potential, there is a need for further R&D on improvement of borehole heat exchangers and of more effective drilling methods.Snow storage is still a new technology though the Sundsvall snow storage plant has been operated successfully for several years. This good example has inspired several pre-studies of new snow storage plants. These have shown that snow storage is feasible in various sizes and in different applications.

Place, publisher, year, edition, pages
Warszawa: PW Publishing House, 2003
National Category
Water Engineering
Research subject
Water Resources Engineering
Identifiers
urn:nbn:se:ltu:diva-33209 (URN)802c0960-b930-11db-b560-000ea68e967b (Local ID)83-7207-435-6 (ISBN)802c0960-b930-11db-b560-000ea68e967b (Archive number)802c0960-b930-11db-b560-000ea68e967b (OAI)
Conference
International Conference on Thermal Energy Storage : 01/09/2003 - 04/09/2003
Note
Godkänd; 2003; 20070210 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Gehlin, S. & Hellström, G. (2003). Influence on thermal response test by groundwater flow in vertical fractures in hard rock (ed.). Paper presented at . Renewable energy, 28(14), 2221-2238
Open this publication in new window or tab >>Influence on thermal response test by groundwater flow in vertical fractures in hard rock
2003 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 28, no 14, p. 2221-2238Article in journal (Refereed) Published
Abstract [en]

In this paper different approaches to groundwater flow and its effect in the vicinity of a borehole ground heat exchanger are discussed. The common assumption that groundwater flow in hard rock may be modelled as a homogeneous flow in a medium with an effective porosity is confronted and models for heat transfer due to groundwater flow in fractures and fracture zones are presented especially from a thermal response test point of view. The results indicate that groundwater flow in fractures even at relatively low specific flow rates may cause significantly enhanced heat transfer, although a continuum approach with the same basic assumptions would suggest otherwise.

National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-7926 (URN)10.1016/S0960-1481(03)00128-9 (DOI)65b88630-9471-11dd-a897-000ea68e967b (Local ID)65b88630-9471-11dd-a897-000ea68e967b (Archive number)65b88630-9471-11dd-a897-000ea68e967b (OAI)
Note
Upprättat; 2003; 20081007 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved

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