Wiebke Brix Markussen
Technical University of Denmark
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Publication
Featured researches published by Wiebke Brix Markussen.
Science and Technology for the Built Environment | 2015
Lorenzo Bellemo; Brian Elmegaard; Martin Ryhl Kærn; Wiebke Brix Markussen; Lars Reinholdt
Desiccant wheels are rotary desiccant dehumidifiers used in air-conditioning and drying applications. The modeling of simultaneous heat and mass transfer in these components is crucial for estimating their performances, as well as for simulating and optimizing their implementation in complete systems. A steady-state two-dimensional model is formulated and implemented, aiming to obtain good accuracy and short computational times with the purpose of inclusion in complete system models. The model includes mass and energy balances and correlations for heat and mass transfer based on empirical relations from the scientific literature. Convective heat and mass transfer coefficients are computed locally accounting for the entrance length effects. Mass diffusion inside the desiccant material is neglected. Comparison with experimental data from the literature shows that the model reproduces the physical behavior of desiccant wheels satisfactorily, as the deviation between the computed results and available data is always within 12%. The simulation time is as low as 3 s for a model with 200 control volumes. It is found that for the applied case, the model provides accurate results for the overall flow using an equiangular control volume discretization with 200 control volumes and no axial discretization. More computationally expensive configurations with axial discretization give more accurate results and information on local flow and desiccant conditions inside the wheel.
13th IIR Gustav Lorentzen Conference on Natural Refrigerants (GL2018) | 2018
Pernille Hartmund Jørgensen; Torben Schmidt Ommen; Wiebke Brix Markussen; Erasmus Damgaard Rothuizen; Kenneth Hoffmann; Brian Elmegaard
Denmark presents ambitious climate policies, and in order to fulfil these visions electrically driven large-scale heat pumps (HP) are often mentioned as an important technology for future district heating (DH) systems. To reach the high temperatures needed in current DH systems, the suggested HP installations become complex systems, where heat transfer between the HP cycle and the heat sink takes place at several temperature levels. In this study the heat exchanger network (HEN) between a HP installation consisting of two serially connected two-stage ammonia HP units and a heat sink being heated from 50 °C to 80 °C was investigated. The study applied pinch analysis to estimate the highest attainable Coefficient of Performance (COP) with the given HP configuration. Based on the result of the pinch analysis, a HEN reaching the highest COP was suggested and compared with COPs obtained with three other solutions for a HEN. The result revealed an estimated highest COP of 3.46. The three other design suggestions yielded reductions in the COP of -2.3%, -2.0%, and -1.8% compared to the highest. From this it was concluded that the HEN has an influence on the COP, and that the pinch analysis can be used to estimate the highest COP for a given HP installation. Furthermore, the COP obtained by practical installations was accordingly shown to come close to the target.
Energy | 2016
Torben Schmidt Ommen; Wiebke Brix Markussen; Brian Elmegaard
Energy | 2014
Torben Schmidt Ommen; Wiebke Brix Markussen; Brian Elmegaard
Energy | 2014
Torben Schmidt Ommen; Wiebke Brix Markussen; Brian Elmegaard
International Journal of Refrigeration-revue Internationale Du Froid | 2015
Torben Schmidt Ommen; Jonas Kjær Jensen; Wiebke Brix Markussen; Lars Reinholdt; Brian Elmegaard
International Journal of Refrigeration-revue Internationale Du Froid | 2015
Jonas Kjær Jensen; Wiebke Brix Markussen; Lars Reinholdt; Brian Elmegaard
Energy | 2017
Torben Schmidt Ommen; Jan Eric Thorsen; Wiebke Brix Markussen; Brian Elmegaard
Energy | 2017
Jonas Kjær Jensen; Torben Schmidt Ommen; Wiebke Brix Markussen; Brian Elmegaard
international journal of energy and environmental engineering | 2015
Jonas Kjær Jensen; Wiebke Brix Markussen; Lars Reinholdt; Brian Elmegaard