Dennis Roskosch


Last Name

Roskosch

First Name

Dennis

ORCID

0000-0001-5144-8348

Organisational unit

01159 - Lehre Maschinenbau und Verfahrenstechnik

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2013 - 2019142020 - 202540
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Publications 1 - 10 of 54
  • Potential Analysis of Pumped Heat Electricity Storages Regarding Thermodynamic Efficiency
    Item type: Conference Paper
    Roskosch, Dennis; Atakan, Burak (2017)
    30th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2017)
    The rising share of renewable energy sources in power generation leads, due to increasing fluctuations, to the need of higher storage capacities. In this context, also some interest in pumped heat electricity storage (PHES) arises. The basic principle of such a PHES system is simple; in case of oversupply of energy to the grid, a thermodynamic cycle transfers electrical energy to thermal energy and charges the storage. In the event that less electrical energy is generated than consumed, a further thermodynamic cycle discharges the storage and converts thermal energy to electrical energy back again. Against the background that combining two Carnot cycles leads always to a roundtrip efficiency of 1, the maximum possible efficiency as well as important variables of such systems are nearly unknown, so far. In this context Thess [1], assuming a maximum power cycle, and also, equal charging and discharging times, derived an analytical expression for the roundtrip efficiency as a function of the heat source and heat sink temperatures. The present work also investigates two reversible cycles with irreversible heat transfer but analyses the roundtrip efficiency as a function of storage temperature, power output, thermal resistances (R=1/(U·A)) of the heat exchangers and relative charging and discharging time. From a thermodynamic point of view, an upper limit for the roundtrip efficiency is only found if restrictions like maximum power output are specified. Rather, power output and roundtrip efficiency lead to a Pareto frontier and a selection criterion must finally base on other, probably economic aspects. Regarding an exemplary storage temperature of 400 K, a reduction of the required power output by 10 % (relative to the maximum power output) already leads to a 40% increased roundtrip efficiency and results in a much better evaluation of the theoretical potential of PHES systems.
  • Indirect Electrochemical Cooling: Model-Based Performance Analysis and Working Fluid Selection
    Item type: Journal Article
    Liebl, Lana; Bardow, André; Roskosch, Dennis (2024)
    Industrial & Engineering Chemistry Research
    The rising energy demand for cooling and heating requires efficient and sustainable technologies. Vapor-compression systems represent the state of the art but suffer from downscaling limits and maintenance needs. These disadvantages may be overcome by recently proposed electrochemical processes. However, their potential has not been explored systematically. This work quantifies the thermodynamic potential of an indirect electrochemical cooling process that replaces the vapor compressor of a standard refrigeration cycle with an electrochemical cell. An equilibrium-based process model evaluates the process performance of a working fluid, depending on its composition and temperatures in the process. After screening an extensive database for possible working fluids, an electrochemical cooling process is analyzed and optimized for the coefficient of performance (COP) to operate between two heat reservoirs at 20 °C (heat source) and 35 °C (heat sink). The majority of the investigated working fluids yield smaller or similar efficiencies than vapor-compression refrigeration, with COPs between 3.0 and 4.0. However, 35 promising working fluids that achieve higher efficiencies are identified with a COP up to 9.63, corresponding to 49% of Carnot. These working fluids are worthy of further investigation as their use in the electrochemical cooling process possibly outperforms standard vapor-compression refrigeration.
  • Thermographic phosphor thermometry in transient combustion: A theoretical study of heat transfer and accuracy
    Item type: Journal Article
    Atakan, Burak; Roskosch, Dennis (2013)
    Proceedings of the Combustion Institute
  • Predicting PC-SAFT parameters of dipolar molecules: A Group-Contribution method
    Item type: Conference Poster
    Hemprich, Carl; Rehner, Philipp; Roskosch, Dennis; et al. (2023)
  • Propene/isobutane mixtures in heat pumps: An experimental investigation
    Item type: Journal Article
    Venzik, Valerius; Roskosch, Dennis; Atakan, Burak (2017)
    International Journal of Refrigeration
  • Inventory estimation for chemical processes from the reaction stoichiometry by decision trees
    Item type: Other Conference Item
    Langhorst, Tim; Tuchschmid, Moritz; Winter, Benedikt; et al. (2024)
    Abstract Book SETAC Europe 34th Annual Meeting
  • A theoretical approach to identify optimal replacement fluids for existing vapour compression refrigeration systems and heat pumps
    Item type: Conference Paper
    Roskosch, Dennis; Venzik, Valerius; Atakan, Burak (2018)
    Proceedings of the Heat Powered Cycles Conference 2018
    The nowadays used working fluids for vapour compression refrigeration systems and heat pumps partly have a high global warming potential and will have to be replaced. This holds for systems in operation but also to a large number of existing cycle designs. Therefore, it would be very helpful if alternative working fluids for a given plant could be found which do not require a redesign of the system and which, in best case, also are more efficient. Although it seems possible to achieve this goal with modern process simulation tools, it remains unclear how detailed a concrete plant design must be modelled to obtain a reliable ranking of working fluids, useful for selection. In order to investigate this question a vapour compression heat pump test rig is simulated by thermodynamic models with different levels of complexity. The model results are compared among each other and to measured values for various fluids. It turns out that simple cycle calculations lead to incorrect results regarding the efficiency and thus are not sufficient to find replacement fluids for existing plants. The implementation of a compressor model significantly improves the simulation and leads finally to reliable fluid rankings. However, the information whether the heat exchangers are of sufficient size and whether the fluid is suited at all for a given task can only be obtained, as it turns out, by means of the most complex model which includes extensive models for the heat exchangers.
  • High-temperature heat pumps and zeotropic refrigerant mixtures: A perfect match?
    Item type: Other Conference Item
    Widmaier, Philip Karl; Bardow, André; Roskosch, Dennis (2023)
    Refrigerant mixtures can improve the efficiency of high-temperature vapor compression heat pumps by matching their non-isothermal phase change to temperature changes in the heat source and sink. Previous studies suggest that the advantage of mixtures compared to pure refrigerants increases for larger temperature changes of heat sources and sinks. However, the potential efficiency increase has not yet been systematically studied. Thus, the conditions are still unclear under which zeotropic mixtures are particularly beneficial. In this work, we therefore screen a comprehensive set of pure refrigerants and all their binary mixtures for a broad range of sink and source temperature changes. The refrigerant set includes 33 natural and halogenated refrigerants. To assess the mixture performance, we model the heat pump process. Here, the compressor efficiencies depend upon the refrigerants. The study confirms the basic theory that mixtures can substantially improve the coefficient of performance (COP) and the benefits increase with the temperature changes of sink and source. However, the temperature change is shown to be more relevant at the heat source: mixtures are already beneficial at small temperature changes of the heat source, while a minimal temperature change of 10 K is needed for the heat sink. The greatest COP increase of a mixture, at 27%, is identified at maximum temperature changes of 40 K in the source and in the sink. The optimal mixture is highly specific to the temperature changes of heat sink and source. However, binary mixtures are identified that show good performance over broad ranges of source and sink temperature changes when their composition is tailored, e.g., pentene/cyclopropane. Such refrigerant mixtures could have the potential for universal use in heat pumps.
  • Elektrochemische Kältemaschine: Eine Alternative zur Dampfkompression?
    Item type: Other Conference Item
    Liebl, Lana; Roskosch, Dennis; Bardow, André (2021)
    Thermodynamik-Kolloquium 2021. Book of Abstracts
Publications 1 - 10 of 54