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Im Rahmen dieser Arbeit wird eine dynamische Modellierung eines regelbaren PKW-Axialkolbenverdich... more Im Rahmen dieser Arbeit wird eine dynamische Modellierung eines regelbaren PKW-Axialkolbenverdichters mit Schwenkscheibenmechanismus für das Kältemittel CO2 durchgeführt, die den Verdichter in seiner Gesamtheit beschreibt. Das erstellte Gesamtmodell setzt sich dabei aus mehreren Teilmodellen zusammen, die unter anderem die Thermodynamik der Zylinderräume, der Saug- und Druckkammer sowie des Kurbelgehäuses, die Wärmeübertragung, die Dynamik und Reibung von Schwenkscheibe und Kolben, das Ventilverhalten, die Kolbenleckage und die Regelmassenströme beschreiben. Das Gesamtmodell wird anhand von Messdaten aus der Literatur für den stationären Volllastbetrieb und teilweise auch für den dynamischen Betrieb validiert. Wesentliche Schwerpunkte und Fortschritte im Vergleich zum bisherigen Stand des Wissens sind die simulative Verknüpfung von Detailmodellen zu einem umfassenden Gesamtmodell, die dynamische Modellierung von Kolben und Schwenkscheibe, wobei auch die Beeinflussung der einzelnen K...
As a result of the Kyoto Protocol, the use of R134a in air conditioning system of new cars is goi... more As a result of the Kyoto Protocol, the use of R134a in air conditioning system of new cars is going to be forbidden in the EU due to the high Global Warming Potential (GWP) of this substance. Carbon dioxide (CO2) is one of the possible alternatives as a cooling agent in mobile air conditioning applications and is desirable since it is a natural refrigerant. Cooling cycles using CO2 are currently achieving COP simi-lar to those of R134a cycles but there are promising options to further improve COP. One possibility is the application of an ejector instead of the valve. A Modelica library was developed that allows compu-tation of ejector cooling cycles in steady state with simplified component models that can be used as a design tool for the construction of an ejector proto-type. The library uses a new object-oriented library that serves as an interface to external medium librar-ies to compute thermodynamic and transport proper-ties for the refrigerant.
The focus of this investigation is the development of an advanced transient model to describe the... more The focus of this investigation is the development of an advanced transient model to describe the operation of a controlled swash plate compressor for an automotive air-conditioning system using the natural refrigerant R744. The over-all model consists of several partial models, that describe the thermodynamic laws in the control volumes of the cylinders, the suction and discharge chamber as well as the crankcase, the heat transfer, the dynamics and friction of the swash plate and the pistons, the valve behavior, the piston leakage and the control valve mass flows. Based on measured data from the literature a validation is carried out under stationary full load operation conditions. The main focus of this investigation and the achieved progress compared to the state-of-the-art are the simulative linkage of the sub models in one complete model: the dynamic modeling of pistons and swash plate taking into account the impact of each individual piston on each other. An extensive sensitiv...
As a result of the Kyoto Protocol, the use of R134a in air conditioning system of new cars is goi... more As a result of the Kyoto Protocol, the use of R134a in air conditioning system of new cars is going to be forbidden in the EU due to the high Global Warming Potential (GWP) of this substance. Carbon dioxide (CO2) is one of the possible alternatives as a cooling agent in mobile air conditioning applications and is desirable since it is a natural refrigerant. Cooling cycles using CO2 are currently achieving COP similar to those of R134a cycles but there are promising options to further improve COP. One possibility is the application of an ejector instead of the valve. A Modelica library was developed that allows computation of ejector cooling cycles in steady state with simplified component models that can be used as a design tool for the construction of an ejector prototype. The library uses a new object-oriented library that serves as an interface to external medium libraries to compute thermodynamic and transport properties for the refrigerant.
Im Rahmen dieser Arbeit wird eine dynamische Modellierung eines regelbaren PKW-Axialkolbenverdich... more Im Rahmen dieser Arbeit wird eine dynamische Modellierung eines regelbaren PKW-Axialkolbenverdichters mit Schwenkscheibenmechanismus für das Kältemittel CO2 durchgeführt, die den Verdichter in seiner Gesamtheit beschreibt. Das erstellte Gesamtmodell setzt sich dabei aus mehreren Teilmodellen zusammen, die unter anderem die Thermodynamik der Zylinderräume, der Saug- und Druckkammer sowie des Kurbelgehäuses, die Wärmeübertragung, die Dynamik und Reibung von Schwenkscheibe und Kolben, das Ventilverhalten, die Kolbenleckage und die Regelmassenströme beschreiben. Das Gesamtmodell wird anhand von Messdaten aus der Literatur für den stationären Volllastbetrieb und teilweise auch für den dynamischen Betrieb validiert. Wesentliche Schwerpunkte und Fortschritte im Vergleich zum bisherigen Stand des Wissens sind die simulative Verknüpfung von Detailmodellen zu einem umfassenden Gesamtmodell, die dynamische Modellierung von Kolben und Schwenkscheibe, wobei auch die Beeinflussung der einzelnen K...
As a result of the Kyoto Protocol, the use of R134a in air conditioning system of new cars is goi... more As a result of the Kyoto Protocol, the use of R134a in air conditioning system of new cars is going to be forbidden in the EU due to the high Global Warming Potential (GWP) of this substance. Carbon dioxide (CO2) is one of the possible alternatives as a cooling agent in mobile air conditioning applications and is desirable since it is a natural refrigerant. Cooling cycles using CO2 are currently achieving COP simi-lar to those of R134a cycles but there are promising options to further improve COP. One possibility is the application of an ejector instead of the valve. A Modelica library was developed that allows compu-tation of ejector cooling cycles in steady state with simplified component models that can be used as a design tool for the construction of an ejector proto-type. The library uses a new object-oriented library that serves as an interface to external medium librar-ies to compute thermodynamic and transport proper-ties for the refrigerant.
The focus of this investigation is the development of an advanced transient model to describe the... more The focus of this investigation is the development of an advanced transient model to describe the operation of a controlled swash plate compressor for an automotive air-conditioning system using the natural refrigerant R744. The over-all model consists of several partial models, that describe the thermodynamic laws in the control volumes of the cylinders, the suction and discharge chamber as well as the crankcase, the heat transfer, the dynamics and friction of the swash plate and the pistons, the valve behavior, the piston leakage and the control valve mass flows. Based on measured data from the literature a validation is carried out under stationary full load operation conditions. The main focus of this investigation and the achieved progress compared to the state-of-the-art are the simulative linkage of the sub models in one complete model: the dynamic modeling of pistons and swash plate taking into account the impact of each individual piston on each other. An extensive sensitiv...
As a result of the Kyoto Protocol, the use of R134a in air conditioning system of new cars is goi... more As a result of the Kyoto Protocol, the use of R134a in air conditioning system of new cars is going to be forbidden in the EU due to the high Global Warming Potential (GWP) of this substance. Carbon dioxide (CO2) is one of the possible alternatives as a cooling agent in mobile air conditioning applications and is desirable since it is a natural refrigerant. Cooling cycles using CO2 are currently achieving COP similar to those of R134a cycles but there are promising options to further improve COP. One possibility is the application of an ejector instead of the valve. A Modelica library was developed that allows computation of ejector cooling cycles in steady state with simplified component models that can be used as a design tool for the construction of an ejector prototype. The library uses a new object-oriented library that serves as an interface to external medium libraries to compute thermodynamic and transport properties for the refrigerant.