Browsing NTNU Open by Author "Nekså, Petter"

Now showing items 1-20 of 56

    • A steady and quasi-steady state analysis on the CO2 hybrid ground-coupled heat pumping system 

      Jin, Zhequan; Eikevik, Trygve Magne; Nekså, Petter; Hafner, Armin (Journal article; Peer reviewed, 2017)
      This article contains the steady and quasi-steady state analysis on a CO2 hybrid ground-coupled heat pumping system for warm climates. The hybrid system uses a combination of ambient air and ground boreholes as a heat sink ...

    • Active and passive measures to maintain pressure in LNG fuel systems for ships 

      Hernes, Hugo Eugen (Master thesis, 2015)
      The purpose of this master thesis is to investigate the effects of active and passive measures to maintain the pressure in LNG fuel systems for ships. The background was two de-loading events that occurred on the gas engines ...

    • Advancements in Automated Methods for Fluid-Dynamic Turbomachinery Design 

      Agromayor Otero, Roberto (Doctoral theses at NTNU;2021:180, Doctoral thesis, 2021)
      Automated design methods are emerging as a powerful tool for the fluid-dynamic design of turbomachinery components. Such automated methods integrate mathematical models of different level of sophistication with numerical ...

    • Analysis of Natural Gas engine de-loading on LNG fuelled vessels 

      DiRenzo, Joseph; Nekså, Petter; Kolsaker, Kjell (Journal article; Peer reviewed, 2015)
      Onboard the Norwegian Coast Guard vessel KV Bergen, as well as other LNG fuelled vessels, there has been reports of a sudden fall in the fuel tank system pressure, resulting in de-loading of the NG engines. This study ...

    • Analysis of R744 refrigeration system with liquid ejectors 

      Singh, Simarpreet; Reddy, Amshith; Parkash, Maiya M.; Banasiak, Krzysztof; Hafner, Armin; Nekså, Petter (Chapter, 2018)
      In recent years, there is a rapid increase in the cooling demand. Hence, not only the consumption of energy, but also the quantity of the refrigerants released into the air is increasing globally leading to planetary ...

    • Annual energy performance of R744 and R410A heat pumping systems 

      Jin, Zhequan; Eikevik, Trygve Magne; Nekså, Petter; Hafner, Armin; Wang, Ruzhu (Journal article; Peer reviewed, 2017)
      This work compares the annual energy performance of heat pumping systems using R744 and R410A as refrigerant. Focus is the annual energy efficiency of R744 hybrid ground-coupled heat pumping system. The hybrid system uses ...

    • Boil-off gas handling from liquefied hydrogen storage 

      Groznik, Jan (Master thesis, 2020)
      The main objective of the thesis was to develop concepts for hydrogen boil-off gas reliquefaction. Three different processes were simulated, analyzed, and compared: helium Brayton refrigeration cycle with two helium turbine ...

    • CO2 Capture from IGCC by Low-Temperature Synthesis Gas Separation 

      Berstad, David Olsson; Skaugen, Geir; Roussanaly, Simon; Anantharaman, Rahul; Nekså, Petter; Jordal, Aina Benedikte Kristin; Trædal, Stian; Gundersen, Truls (Journal article; Peer reviewed, 2022)
      Capture conditions for CO2 vary substantially between industrial point sources. Depending on CO2 fraction and pressure level, different capture technologies will be required for cost- and energy-efficient decarbonisation. ...

    • Concepts for Large Scale Hydrogen Liquefaction Plants 

      Eckroll, Jørgen (Master thesis, 2017)
      The main objective of this thesis is to perform a technical-exergetic analysis of a large-scale hydrogen liquefaction system. The system boundary of the technical analysis is isolated to the precooling part of the overall ...

    • Concepts for Large Scale Hydrogen Production 

      Jakobsen, Daniel; Åtland, Vegar (Master thesis, 2016)
      The objective of this thesis is to perform a techno-economic analysis of large-scale, carbon-lean hydrogen production in Norway, in order to evaluate various production methods and estimate a breakeven price level. Norway ...

    • Cryogenic CO2 condensation and membrane separation of syngas for large-scale LH2 production 

      Berstad, David Olsson; Wilhelmsen, Øivind; Skjervold, Vidar T.; Nekså, Petter (Chapter, 2017)
      Liquid hydrogen (LH2) has the potential to become a global energy commodity analogous to liquefied natural gas (LNG) in the future. This will require LH2 production capacities of similar scale as for large-scale LNG plants. ...

    • Dynamic Analysis of Energy Recovery Utilizing Thermal Storage from Batch-Wise Metal Casting 

      Andresen, Trond; Lingaas, Simon Johan Nilsen; Hagen, Brede; Nekså, Petter (Chapter, 2020)
      The thermal exergy contained in the liquid metal in ferroalloy production makes it an interesting source for energy recovery. The heat released during casting is rarely utilized today. This work investigates the feasibility ...

    • Dynamisk simulering av systemløsninger for kuldeanlegg i supermarked 

      Watvedt, Lars Siewers (Master thesis, 2011)
      Energibruk i supermarkeder er blant de høyeste innefor bygningssektoren i Norge. Norske supermarkeder har typisk et årlig energibehov på mellom 400 og 600 kWh/m^2 . Opp mot 50 % av dette totale energibehovet går til ...

    • Effect of design specifications for off-design operation of low temperature Rankine cycles using zeotropic mixtures and pure working fluids 

      Durakovic, Goran (Master thesis, 2018)
      Using organic Rankine cycles to produce power from low temperature heat sources seems like a promising solution to lower our reliance on environmentally damaging energy sources. By introducing this technology to new and ...

    • Enabling Efficient Heat Recovery from Aluminium Pot Gas 

      Clos, Daniel Perez; Andresen, Trond; Nekså, Petter; Johnsen, Sverre Gullikstad; Aune, Ragnhild Elizabeth (Chapter, 2017)
      In the present work, previous studies carried out by the Norwegian aluminium industry and research centres with the aim of recovering heat from aluminium production off-gas, are reviewed. The main challenge in improving ...

    • Energy efficient multiejector CO2 cooling system for high ambient temperature 

      Singh, Simarpreet; Maiya, Prakash; Hafner, Armin; Banasiak, Krzysztof; Nekså, Petter (Peer reviewed; Journal article, 2020)
      Experimental evaluation of a multiejector CO2 cooling system of 33 kW cooling capacity is conducted for an Indian supermarket at high ambient temperature context. The test-rig is designed to depict the actual supermarket ...

    • Equation-oriented methods for design optimization and performance analysis of radial inflow turbines 

      Hagen, Brede; Agromayor, Roberto; Nekså, Petter (Peer reviewed; Journal article, 2021)
      This paper presents methods for design optimization and performance analysis of radial inflow turbines. Both methods are formulated in an equation-oriented manner and involve a single mathematical problem that is solved ...

    • Evaluation of Rankine cycles with mixed component working fluids 

      Nikolaisen, Monika (Master thesis, 2017)
      The thesis evaluates the performance of Rankine cycles with mixed component hydrocarbon working fluids, or hydrocarbon mixtures. The objective is to compare mixtures with pure fluids on the basis of the same total heat ...

    • Experimental Evaluation of a Multi-Ejector Trans-critical CO2 System for Supermarkets 

      Singh, Simarpreet; Hafner, Armin; Banasiak, Krzysztof; Maiya, Prakash; Nekså, Petter (Chapter, 2019)
      In the present experimental study, the performance of a multi-ejector based trans-critical CO2 cooling system is tested at high ambient temperature up to 46°C for a supermarket application with and without internal heat ...

    • Experimental evaluation of multi-ejector based CO2 cooling system for supermarkets in tropical zones 

      Singh, Simarpreet; Hafner, Armin; Banasiak, Krzysztof; Maiya, Prakash M.; Nekså, Petter (Chapter, 2018)
      Cooling system for supermarkets, now-a-days in developing countries like India, mainly uses man-made synthetic refrigerants/mixtures such as R134a, R404A and R410A (HFCs). These fluorinated refrigerants possess an outrageous ...