Now showing items 1-20 of 117

    • A CFD analysis for the performance assessment of a novel design of plates-in-tank latent storage unit for freezing applications 

      Selvnes, Håkon; Allouche, Yosr; Sevault, Alexis; Hafner, Armin (Chapter, 2019)
      In this paper, the charging and discharging processes of a recently developed cold thermal energy storage (CTES) unit integrated into a poultry processing plant is investigated. A mathematical model of the CTES was created ...
    • A modified homogeneous relaxation model for CO2 two-phase flow in vapour ejector 

      Haida, Michal; Palacz, Michal; Smolka, Jacek; Nowak, Andrzej J.; Hafner, Armin; Banasiak, Krzysztof (Journal article; Peer reviewed, 2016)
      In this study, the homogenous relaxation model (HRM) for CO2 flow in a two-phase ejector was modified in order to increase the accuracy of the numerical simulations The two- phase flow model was implemented on the effective ...
    • A novel PCM accumulator for refrigerated display cabinet : design and CFD simulations 

      Sevault, Alexis; Banasiak, Krzysztof; Bakken, Jørn; Hafner, Armin (Chapter, 2018)
    • A review on recent technological advancements in multi-ejector concept 

      Gullo, Paride; Hafner, Armin; Banasiak, Krzysztof; Minetto, Silvia (Chapter, 2018)
      As a consequence of the coming into force of the EU F-Gas Regulation 517/2014, enormous technological developments have been experienced on the part of transcritical R744 supermarket refrigeration systems. These have led ...
    • 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 ...
    • Air reversing CO2 heat pumps 

      Andreassen, Hanne Elisabeth Bø (Master thesis, 2010)
      CO2 is an environmentally friendly refrigerant that has a no global warming potential when used as refrigerant. The current refrigerants used for air conditioning in public transport are chemical components, and have a ...
    • 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 ...
    • Analysis of supermarket CO2 refrigeration cycles equipped with multi-ejectors 

      Wiecha, Jakub Krzysztof (Master thesis, 2016)
      This thesis presents an analysis of operating conditions in a refrigeration system located in supermarket Rema 1000 Prinsensgata, Trondheim (Norway). The main emphasis is put on a problem with oversized gas cooler, which ...
    • ANN modelling of CO2 refrigerant cooling system COP in a smart warehouse 

      Opalic, Sven Myrdahl; Goodwin, Morten; Lei, Jiao; Nielsen, Henrik Kofoed; Pardiñas, Ángel Á.; Hafner, Armin; Kolhe, Mohan Lal (Peer reviewed; Journal article, 2020)
      Industrial cooling systems consume large quantities of energy with highly variable power demand. To reduce environmental impact and overall energy consumption, and to stabilize the power requirements, it is recommended to ...
    • 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 ...
    • Attaining a higher flexibility degree in CO2 compressor racks 

      Álvarez Pardiñas, Ángel; Contiero, Luca; Hafner, Armin; Banasiak, Krzysztof; Larsen, Lars F.S. (Chapter, 2020)
      CO2 compressor racks have shown their suitability for commercial and industrial refrigeration systems at any location and climate. Even if some references state that CO2 units can compete in capital cost with any other ...
    • CFD modeling of ice formation and melting in horizontally cooled and heated plates 

      Selvnes, Håkon; Allouche, Yosr; Sevault, Alexis; Hafner, Armin (Chapter, 2019)
      This paper investigates the ice formation and melting processes in a novel CTES unit using the commercial CFD software ANSYS Fluent 19. The storage unit is designed to operate as a peak shaving device integrated into the ...
    • Characteristics of evaporation of propane (R290) in compact smooth and microfinned tubes 

      Allymehr, Ehsan; Pardiñas, Ángel Á.; Eikevik, Trygve Magne; Hafner, Armin (Peer reviewed; Journal article, 2020)
      Evaporation of flowing propane and the effect of enhanced geometry on heat transfer coefficient and pressure drop is experimentally investigated. One smooth tube and two microfinned tubes with an outer diameter of 5 mm ...
    • CO2 cooling challenges at CERN for the future phase 2 upgrade program 

      Verlaat, B; Petagna, P.; Zwalinski, L; Daguin, J.; Giakoumi, D.; Bhanot, V; Battistin, M; Hafner, Armin; Collot, J; Postema, H; Tropea, P; Blust, Stefanie; Hanf, P; Pardiñas, Ángel Á. (Chapter, 2019)
      At CERN, evaporative CO2 is the baseline cooling solution for the thermal management of the phaseII silicon detectors which will be installed in 2025 in the ATLAS and CMS experiments. Since 2008 CO2 cooling is used in 3 ...
    • CO2 Solar Assisted Heat Pump System for Water heating, Drying, and Cooling. 

      Nana, Oluwafemi Samuel (Master thesis, 2017)
      Solar energy is often considered as waste energy in the world as only few percentage of the solar energy reaching the earth being harnessed for use. With growing demand in heating and cooling demands around the world, it ...
    • Cold thermal energy storage with low-temperature plate freezing of fish on offshore vessels 

      Verpe, Espen Halvorsen; Tolstorebrov, Ignat; Sevault, Alexis; Hafner, Armin; Ladam, Yves (Chapter, 2019)
      This paper presents the results of a numerical and experimental study of freezing time for fish in plate freezers, and the potential for improvement by altering fish block thickness and lowering evaporation temperature. ...
    • Cold thermal storage integration in a large industrial refrigeration system 

      Selvnes, Håkon; Hafner, Armin; Kauko, Hanne (Chapter, 2018)
      Global warming is one of the greatest challenges our society faces today, and researchers strive to find solutions to reduce the emissions of greenhouse gases that accelerate the global warming effect. This paper describes ...
    • Compact Interior Heat Exchangers for CO2 Mobile Heat Pumping Systems 

      Hafner, Armin (Dr. ingeniøravhandling, 0809-103X; 2003:69, Doctoral thesis, 2003)
      The natural refrigerant carbon dioxide (CO2) offers new possibilities for design of flexible, efficient and environmentally safe mobile heat pumping systems. As high-efficient car engines with less waste heat are developed, ...
    • Comparative analysis of evaporation of isobutane (R600a) and propylene (R1270) in compact smooth and microfinned tubes 

      Allymehr, Ehsan; Pardiñas, Angel A.; Eikevik, Trygve Magne; Hafner, Armin (Peer reviewed; Journal article, 2021)
      Data base for evaporation of flowing isobutane and propylene in compact internally enhanced surfaces is extended by experimental tests in two microfinned tubes and a smooth tube. The outer diameter for all of the test tubes ...
    • Comparative study of various supermarket refrigerating systems in European climate context 

      Gullo, Paride; Purohit, Nilesh; Dasgupta, Mani Sankar; Hafner, Armin; Banasiak, Krzysztof (Chapter, 2018)
      Due to the enormous carbon footprint of food retail stores the interest in natural working fluids, such as propane (R290) and CO2 (R744), has recently intensified in the commercial refrigeration sector. In this theoretical ...