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    Two-phase Loop Thermosiphon Coupled With Latent Heat Storage For Electronics Cooling
    (Purdue University Libraries, 2022-07)
    Albertsen, Björn
    ;
    Speerforck, Arne
    In this study, a twophase loop thermosiphon cooling system is coupled with latent heat storages integrated in the evaporator and investigated experimentally. A test rig using the lowGWP refrigerant R1233zd(E) is set up with a maximum power of 1.3 kW (23.2 W cm-1), supplied by a dummy for the electronic component to be cooled. Dynamic application scenarios are divided into two general categories and examined using respective examples. The results show high potential for changes in the heat sink temperature, whereas varying heat loads are more challenging regarding design and dimensioning of the PCMevaporatorcomposites. In both cases, significant improvements can be achieved in terms of temperatures and uncritical operation time.
    Publicationtype: Conference Paper
      82
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    IEA HPT Annex 54: heat pump systems with low-GWP refrigerants ; country report: Germany
    (IEA, 2022-01)
    Oltersdorf, Thore
    ;
    Schnabel, Lena
    ;
    Braungardt, Simon
    ;
    Fugmann, Hannes
    ;
    Joos, Lukas
    This report provides a comprehensive, most up-to-date review of current research and the development of systems and their optimizations using low-GWP refrigerants for heat pump applications. It also includes a state-of-the-art review of life cycle evaluations of such systems using low-GWP refrigerants. It summarizes the collective efforts by researchers, engineers, and regulation committees across the industry. The report is comprised of the following chapters. Chapter 1 provides two representative studies from teams in the United States. The first part summarizes the activities related to establishing a detailed database of alternative lower GWP refrigerants for various HVAC&R applications, including thermodynamic and transport properties. The goal is to identify the most suitable candidates for replacing traditional refrigerants based on thermodynamic performance and environmental benefits. It also considers the extent of potential system adjustments required to accommodate the new alternative refrigerants. The second part provides a comprehensive investigation of unitary air conditioners' life cycle climate performance. The review focused on life cycle climate performance methodologies, impacts of parameter and methodology selections, and a few representative case studies. Chapter 2 provides a comprehensive update on research and development activities in Italy. Three research entities report their progress on low GWP refrigerants and their applications in various heat pump systems. The chapter covers condensation and boiling heat transfer coefficients measurements, and multiple experimental-oriented projects on long-term evaluations of novel heat pump systems using low GWP refrigerants. Chapter 3 mainly describes the work in Japan, the first step of a two-step process on life cycle climate performance evaluation of heat pump-type air conditioners with next-generation refrigerants. It also presents an overview of a project to establish a new concept and hypothesis for life cycle climate performance evaluation, in which field data related to air conditioners is adopted. Chapter 4 presents a study carried out by the France teams on finned tube heat exchangers using low GWP refrigerants. The study assessed the heat transfer performance during evaporation and condensation of R410A, R454B, and R32 in a finned tube heat exchanger. A 30-kW experimental setup was built to assess the heat exchanger performance with these three refrigerants. The simulations show that the same design of the finned tube heat exchanger can be used for R410A and R454B, but a design optimization is necessary with R32. Chapter 5 presents a high-level summary of R&D progress across multiple institutions in Germany. Part one is a summary of the most recent large-scale heat pump monitoring project, a review of ongoing heat pump projects based on an analysis of the enArgus database, and a survey on heat pumps and their refrigerants as part of the market incentive program coordinated at the Federal Office for Economic Affairs and Export Control. In part two, within the last five years, the activities for heat pump research have changed. The activities cover more fundamental research up to the application of deployable heat pump demonstrators for white goods (e.g., dishwashers), mobile systems for electric-driven buses, or large capacity heat pumps systems for multi-family houses. This report aims at providing a much-needed review and updates on component R&D using low-GWP refrigerants for heat pump applications. We hope it can be a good reference for researchers, engineers, and policymakers across the HVAC industry. We greatly appreciate the contributions of authors for each chapter. The report would not exist without their valuable efforts.
    Publicationtype: Technical Report
      159
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    Experimental parameter studies on a two-phase loop thermosyphon cooling system with R1233zd(E) and R1224yd(Z)
    (Elsevier, 2021-08-04)
    Albertsen, Björn
    ;
    Schmitz, Gerhard
    Two-phase loop thermosyphon (TPLT) is a promising technology looking at highly effective electronics cooling. Due to strong coupling between the internal and external parameters, in this study experimental tests in steady-state are carried out using R1233zd(E) and R1224yd(Z) as a working fluid to investigate the respective influences and resulting design requirements. The relationship between the governing thermal and flow equations is presented to facilitate the interpretation of the test results. The study shows a stable flow and cooling performance over a wide range of heat loads and recooling temperatures. The refrigerant charge is identified as one of the main influencing factors, with an optimum being between excessive subcooling and beginning dry-out. Both tested refrigerants lead to basically similar results, showing minor differences regarding thermal performance and system stability.
    Publicationtype: Journal Article
    Scopus© Citations 13  139  778
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    Untersuchung einer zweiphasigen Naturumlaufkühlung von Leistungselektroniken im Flugzeug
    (Hüthig, 2019-03)
    Albertsen, Björn
    ;
    Schmitz, Gerhard
    Two-phase natural circulation systems provide effective cooling of power electronics in the aircraft at reduced weight. Due to the lack of a pump, the external operating conditions are of particular importance and are investigated in terms of their influence on the mass flow rate and electronics temperature.
    Publicationtype: Journal Article
      105
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