2. Syst Flashcards
What is a systems? (2)
a definable part of the world that is interesting to us.
It is seperated from its environment by a system boundary.
How can systems be categorized and distinguished? (3)
Can be categorized in:
Isolated systems
Closed systems
Open systems
What types of energy transfer exist? (3)
mechanical
thermal
through material flow
Types of energy transfer
mechanical: Energy in the form of ?(1)? crosses the system boundary
thermal: Energy in the form of ?(2)? is transferred across the system boundaries
through material flow: Different types of energy (e.g. kinetic energy) cross the system boundary with the ?(3)?
(1) work (W)
(2) heat (Q)
(3) material flow
Beispiele für welchen system typ jeweils?
1) Themos flask
2) Cooled turbo compressor
3) Closed cylinder of a combustion engine
1) Isolated system
2) Open system
3) Closed cylinder of a combustion engine
Characteristics of an isolated system? (2)
Matter and energy impermeable
No energy transit possible
Characteristics of an closed system? (2)
Matter impermeable
Energy transfer in the form of:
Work
Heat
Characteristics of an open system? (2)
Matter permeable
Energy transfer in the form of:
Work
Heat
Material-bound energy transport
What is the difference between a system and a model?
A system is the real-world entity being studied, while a model is a simplified abstraction of the system tailored to solve a specific problem.
(System: We analyze the world by diving it into smaller subsystems and sub-subsystems, which are then studied using methmatical methods.
Model: Constructing models simplifies complex systems by creating a simplified description, often using mathematical equations. Models help reduce complexity but are not exact replicas of reality.
From system to model: A model is closely related to the purpose of the problem being investigated. The problem determines the system, system boundaries and the relevant system parameters
Setting up a conceptual model using a box representation
-> p.6
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What is a system analysis? (Definition)
Is a system-technical way of describing a system through:
Elements
A cause-effect-relationship
In a ??, the easiest black-box structure is found in order to describe the relationship between the state of the system and the state of the surroundings
system analysis
What is energy system analysis? (Definition)
Investigation of the structural elements of a system, i.e. the representation of how the system works.
Goals of systems research and systems analysis?
Support decisions in energy policy and energy research with regard to technologies and infrastructures for energy supply and energy conversion on a knowledge-based and systematic basis.
What is thermodynamics? (4)
Could be defined as a “general energy theory”
teaches to distinguish between different forms of energy
describes their conversions into each other by using energy balances of the 1st law of thermodynamics
clarifies the conditions and limits for the conversion during natural and technical processes by applying the statements of the 2nd law of thermodynamics
Energy balancing:
Change = ??
= Transport + Generation - Losses
What are the elements of thermodynamics? (3)
- System and system boundaries
- State/status and variables describing the status
- Process and process variables
What are state variables (Zustandsgrößen)?
variables like mass, temperatur, volume etc.
(The system is in a certain state if it can be described at any moment by a unique set of variables (state variables))
Name some process variables? (4)
for example: Work (W), Power (P), Heat (Q), Heat flow (QPunkt)
(If a system is in energetic interaction with its environment, the state of the system changes, it goes through a process. The energy in the form of e.g. heat or work (process variables) is supplied or removed over the system boundaries)
Energy units, Definition and Conversion Factors
-> slide15!!!!
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Name some common energy units!
Kilojoule (kJ)
Oil equivalent (OE)
Coal equivalent (CE)
Kilocalorie (Kcal)
Kilowatt hour (kWh)
British Thermal Unit (BTU)
Oil (barrels (bbl)):
What is 1 bbl in liter and in tonnes?
1 bbl = 159l ~= 0.136 t
Gas
What is 1 cubic feet/day in m^3/years?
10.34 m^3 / yearc
What is the 1st Law of Themodynamics?
Law of conservation of energy: There can be no generation or destruction of energy
The different forms of energy can be transformed into each other, but they cannot be generated or destroyed.