Per Lundqvist

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Low temperature heating systems for single-family houses, based on heat pumps are becoming progressively more preferable in the global market. The possibility of such systems to optimise the energy utilisation and to achieve a high annual energy efficiency make them more promising for future low energy houses. In this study we model and analyse the(More)
Background: Small capacity, low temperature, geothermal heat sources provide significant opportunities for distributed, small scale power generation. Project definitions and pre-dimensioning however require advanced thermodynamic engineering at a cost independent of project size. In order to reduce this cost, a new method has been developed to allow basic(More)
Performance of Organic Rankine Cycles is sensitive not only to the entry temperature ratio between heat source and heat sink but also to the temperature degradation of the heat source flow, caused by the heat transfer to the process in pre-heater, evaporator and super heater. In order to adopt the cycle to the great variety of heat sources a multitude of(More)
Analysis of global energy efficiency of thermal systems is of practical importance for a number of reasons. Cycles and processes used in thermal systems exist in very different configurations, making comparison difficult if specific models are required to analyze specific thermal systems. Thermal systems with small temperature differences between a hot side(More)
We propose a model to account for the bolometric light curve, quasi-continuum and the Ca ii emission features of the peculiar type Ia supernova (SN) 2002ic, which exploded in a dense circumstellar envelope. The model suggests that the SN Ia had the maximum possible kinetic energy and that the ejecta expand in an approximately spherically symmetric (possibly(More)
We study the evolution of dense neutral clumps located in the outer parts of planetary nebulae. These clumps will be photo-ionized by the ionizing radiation from the central star and change their structure in the process. The main effect of the ionization process is the setting up of a photo-evaporation flow and a shock running through the clump. Once this(More)
Modelling of high resolution Balmer line profiles in the early-time spectra of SN 1998S shows that the inferred fast (≈ 400 km s−1) circumstellar (CS) gas on days 23 and 42 post-explosion is confined to a narrow, negative velocity gradient shell just above the photosphere. This gas may be identified with a slow (v < 40 km s−1) progenitor wind accelerated at(More)
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