Blar i NTNU Open på forfatter "Hafner, Armin"
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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 refrigeration system design and optimization for LNG driven cruise ships
Saeed, Muhammad Zahid; Hafner, Armin; Gabrielii, Cecilia H; Tolstorebrov, Ignat; Widell, Kristina Norne (Chapter, 2021)The cruise industry is in the evolution of eco-friendly technologies due to strict environmental regulations. Liquified natural gas (LNG) is an alternative marine fuel. Compared to conventional diesel fuels, LNG offers a ... -
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 for air conditioning in a supermarket CO2 booster refrigeration system
Selvnes, Håkon; Alvarez Pardinas, Angel; Hafner, Armin (Chapter, 2023)Integrated supermarket refrigeration systems are based on transcritical CO2 booster systems, supplying cooling and freezing of the products in the store and air conditioning (AC) of the shop area by cooling a glycol circuit ... -
Cold thermal energy storage for industrial CO refrigeration systems using phase change material: An experimental study
Selvnes, Håkon; Allouche, Yosr; Hafner, Armin; Schlemminger, Christian; Tolstorebrov, Ignat (Journal article, 2022)Refrigeration systems in industrial food processing plants are large users of electric energy and often show high peak power consumption. Cold thermal energy storage (CTES) technology integrated into refrigeration systems ... -
Cold thermal energy storage in solid-liquid transition of carbon dioxide: Investigating the possibility
Mastani Joybari, Mahmood; Selvnes, Håkon; Sevault, Alexis; Hafner, Armin (Chapter, 2022)Industrial freezing is an energy-intensive process which is growing due to the increasing demand. This is exerting stress on electrical grids, especially at peak hours. To tackle this issue, thermal energy storage has ... -
A cold thermal energy storage unit for CO2 refrigeration using phase change material: First experimental results
Selvnes, Håkon; Allouche, Yosr; Hafner, Armin (Chapter, 2021)Refrigeration demands in industrial food processing plants can vary significantly over a week, depending on the production schedules. As a result, it is common to experience peaks of electricity consumption due to the ... -
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 R744 ejector CFD models
Ringstad, Knut Emil; Hafner, Armin (Chapter, 2021)This work presents a comparative study of four different R744 ejector CFD models at a wide range of operating conditions. The models compared are the homogeneous equilibrium model, the UDRGM mixture model, a homogeneous ... -
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 ... -
A comparative study to investigate two configurations of a two-stage evaporator in a CO2 heat pump chiller
Hazarika, Mihir Mouchum; Hafner, Armin; Bengsch, Jan (Chapter, 2023)This study is carried out to investigate the performance of a CO2 heat pump chiller that provides heating and cooling simultaneously. For heating applications, hot water is produced at 90°C; while for cooling applications, ... -
Compressors for ammonia-water hybrid absorption-compression heat pumps
Ahrens, Marcel Ulrich; Hafner, Armin; Eikevik, Trygve Magne (Chapter, 2019)In this paper, investigations on the development of industrial high temperature heat pumps are carried out based on the analysis of the current available compressors. The compressor used for the ammonia compression is a ... -
Crossing CO2 equator with the aid of multi-ejector concept: A comprehensive energy and environmental comparative study
Gullo, Paride; Tsamos, Konstantinos; Hafner, Armin; Banasiak, Krzysztof; Ge, Yunting; Tassou, Savvas A. (Journal article; Peer reviewed, 2018)The ever-stricter regulations put into effect worldwide to significantly decrease the considerable carbon footprint of commercial refrigeration sector have forced the transition to eco-friendlier working fluids (e.g. CO2, ... -
Cryogenic cold utilization and system integration possibilities for LNG-driven fishing vessels
Saeed, Muhammad Zahid; Widell, Kristina Norne; Hafner, Armin; Nordtvedt, Tom Ståle; Svendsen, Eirik Starheim (Chapter, 2020)Liquified natural gas (LNG) fuelled vessels are increasing in the fishing industry due to its reduced environmental footprint as compared to vessels using heavy hydrocarbon fuels. Cryogenic tanks are used to store LNG on ... -
Current state and market trends in technologies with natural refrigerants
Hafner, Armin; Ciconkov, Risto (Chapter, 2021)The market for refrigeration and heat pumps systems based on natural working fluids is growing at different pace in different market segments, while they have always been applied and available in others. The aim of this ... -
Data-driven modeling of a CO2 refrigeration system
Andreasen, Glenn; Stoustrup, Jakob; Izadi-Zamanabadi, Roozbeh; Pardiñas, Ángel Á.; Hafner, Armin (Peer reviewed; Journal article, 2019)This paper describes a data-driven method for system identification of a CO 2 refrigeration system. Traditionally, the interaction between the measured variables is not utilized as they are highly dependent on the refrigeration ...