This study evaluates the influence of latent heat storage elements on the condenser temperature o... more This study evaluates the influence of latent heat storage elements on the condenser temperature of a commercial household refrigerator. In order to determine the power consumption and the temperature distribution, a standard wire-and-tube condenser is equipped with different heat storage elements (containing water, paraffin or copolymer compound). The results indicate that particularly the application of phase change materials (PCM) lowers the condenser temperature, which leads to a significantly reduced power consumption.
High operating temperatures inside a crystalline silicon photovoltaic cell causes a significant n... more High operating temperatures inside a crystalline silicon photovoltaic cell causes a significant negative effect to its energy conversion efficiency. A reduction of this temperature would not only lead to a gain in energy yield of a PV module but also would have a positive effect to its degradation rate and lifetime. One effective approach seems to absorb the heat flow via phase change materials (PCM). Unfortunately, due to its low thermal conductivity and the mass required to provide a sufficient heat storage capacity, its application for PV modules has been very limited. This investigation includes a assessment of a new PCM compound, featuring an increased thermal conductivity, but with a lower heat storage capacity. For this reason, a single crystalline silicon PV module has been equipped with a conventional, commercially available PCM and another one with the new PCM compound. Both PV-PCM modules and bare reference PV module have been compared at real summer outdoor conditions in...
Molecular dynamics (MD) simulation is applied to the condensation process of supersaturated vapor... more Molecular dynamics (MD) simulation is applied to the condensation process of supersaturated vapors of methane, ethane, and carbon dioxide. Simulations of systems with up to a 10(6) particles were conducted with a massively parallel MD program. This leads to reliable statistics and makes nucleation rates down to the order of 10(30) m(-3) s(-1) accessible to the direct simulation approach. Simulation results are compared to the classical nucleation theory (CNT) as well as the modification of Laaksonen, Ford, and Kulmala (LFK) which introduces a size dependence of the specific surface energy. CNT describes the nucleation of ethane and carbon dioxide excellently over the entire studied temperature range, whereas LFK provides a better approach to methane at low temperatures.
noindent Henry's law constants of the solutes methane, nitrogen, oxygen and carbon dioxide in... more noindent Henry's law constants of the solutes methane, nitrogen, oxygen and carbon dioxide in the solvent ethanol are predicted by molecular simulation. The molecular models for the solutes are taken from previous work. For the solvent ethanol, a new rigid anisotropic united atom molecular model based on Lennard-Jones and Coulombic interactions is developed. It is adjusted to experimental pure component
Currently, molecular modeling and simulation gains importance for the prediction of thermophysica... more Currently, molecular modeling and simulation gains importance for the prediction of thermophysical properties of pure fluids and mixtures, both in research and industry. This is due to several reasons: Firstly, the predictive power of molecular models allows for results with technically interesting accuracies over wide range of state points and makes it superior to classical methods. Secondly, a given molecular
Molecular dynamics simulation is applied to Poiseuille flow of liquid methane in planar graphite ... more Molecular dynamics simulation is applied to Poiseuille flow of liquid methane in planar graphite channels, covering channel diameters between 3 and 135 nm. On this length scale, a transition is found between the regime where local ordering induced by the wall dominates the entire system and larger channel diameters where the influence of boundary slip is still present, but of
Superhydrophobic surfaces play an important role in the development of new product coatings such ... more Superhydrophobic surfaces play an important role in the development of new product coatings such as cars, but also in mechanical engineering, especially design of turbines and compressors. Thus a vital part of the design of these surfaces is the computational simulation of such with a special interest on variation of shape and size of minor pits grooved into plane surfaces.
The most important factor for quantitative results in molecular dynamics simulation are well deve... more The most important factor for quantitative results in molecular dynamics simulation are well developed force fields and models. In the present work, the development of new models and the usage of force fields from the literature in large systems are presented. Both tasks lead to time consuming simulations that require massively parallel high performance computing. In the present work, new
Two of the most challenging tasks in molecular simulation consist in capturing the properties of ... more Two of the most challenging tasks in molecular simulation consist in capturing the properties of systems with long-range interactions (e.g. electrolyte solutions) as well as systems containing large molecules such as hydrogels. For the development and optimization of molecular force fields and models, a large number of simulation runs have to be evaluated to obtain the sensitivity of the target
This study evaluates the influence of latent heat storage elements on the condenser temperature o... more This study evaluates the influence of latent heat storage elements on the condenser temperature of a commercial household refrigerator. In order to determine the power consumption and the temperature distribution, a standard wire-and-tube condenser is equipped with different heat storage elements (containing water, paraffin or copolymer compound). The results indicate that particularly the application of phase change materials (PCM) lowers the condenser temperature, which leads to a significantly reduced power consumption.
High operating temperatures inside a crystalline silicon photovoltaic cell causes a significant n... more High operating temperatures inside a crystalline silicon photovoltaic cell causes a significant negative effect to its energy conversion efficiency. A reduction of this temperature would not only lead to a gain in energy yield of a PV module but also would have a positive effect to its degradation rate and lifetime. One effective approach seems to absorb the heat flow via phase change materials (PCM). Unfortunately, due to its low thermal conductivity and the mass required to provide a sufficient heat storage capacity, its application for PV modules has been very limited. This investigation includes a assessment of a new PCM compound, featuring an increased thermal conductivity, but with a lower heat storage capacity. For this reason, a single crystalline silicon PV module has been equipped with a conventional, commercially available PCM and another one with the new PCM compound. Both PV-PCM modules and bare reference PV module have been compared at real summer outdoor conditions in...
Molecular dynamics (MD) simulation is applied to the condensation process of supersaturated vapor... more Molecular dynamics (MD) simulation is applied to the condensation process of supersaturated vapors of methane, ethane, and carbon dioxide. Simulations of systems with up to a 10(6) particles were conducted with a massively parallel MD program. This leads to reliable statistics and makes nucleation rates down to the order of 10(30) m(-3) s(-1) accessible to the direct simulation approach. Simulation results are compared to the classical nucleation theory (CNT) as well as the modification of Laaksonen, Ford, and Kulmala (LFK) which introduces a size dependence of the specific surface energy. CNT describes the nucleation of ethane and carbon dioxide excellently over the entire studied temperature range, whereas LFK provides a better approach to methane at low temperatures.
noindent Henry's law constants of the solutes methane, nitrogen, oxygen and carbon dioxide in... more noindent Henry's law constants of the solutes methane, nitrogen, oxygen and carbon dioxide in the solvent ethanol are predicted by molecular simulation. The molecular models for the solutes are taken from previous work. For the solvent ethanol, a new rigid anisotropic united atom molecular model based on Lennard-Jones and Coulombic interactions is developed. It is adjusted to experimental pure component
Currently, molecular modeling and simulation gains importance for the prediction of thermophysica... more Currently, molecular modeling and simulation gains importance for the prediction of thermophysical properties of pure fluids and mixtures, both in research and industry. This is due to several reasons: Firstly, the predictive power of molecular models allows for results with technically interesting accuracies over wide range of state points and makes it superior to classical methods. Secondly, a given molecular
Molecular dynamics simulation is applied to Poiseuille flow of liquid methane in planar graphite ... more Molecular dynamics simulation is applied to Poiseuille flow of liquid methane in planar graphite channels, covering channel diameters between 3 and 135 nm. On this length scale, a transition is found between the regime where local ordering induced by the wall dominates the entire system and larger channel diameters where the influence of boundary slip is still present, but of
Superhydrophobic surfaces play an important role in the development of new product coatings such ... more Superhydrophobic surfaces play an important role in the development of new product coatings such as cars, but also in mechanical engineering, especially design of turbines and compressors. Thus a vital part of the design of these surfaces is the computational simulation of such with a special interest on variation of shape and size of minor pits grooved into plane surfaces.
The most important factor for quantitative results in molecular dynamics simulation are well deve... more The most important factor for quantitative results in molecular dynamics simulation are well developed force fields and models. In the present work, the development of new models and the usage of force fields from the literature in large systems are presented. Both tasks lead to time consuming simulations that require massively parallel high performance computing. In the present work, new
Two of the most challenging tasks in molecular simulation consist in capturing the properties of ... more Two of the most challenging tasks in molecular simulation consist in capturing the properties of systems with long-range interactions (e.g. electrolyte solutions) as well as systems containing large molecules such as hydrogels. For the development and optimization of molecular force fields and models, a large number of simulation runs have to be evaluated to obtain the sensitivity of the target
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