ORC System Startup via Gravitational Working Medium Distribution
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Solution Overview
Problem
Organic Rankine Cycle (ORC) systems face challenges in starting up reliably due to insufficient working medium distribution and unfavorable temperature distribution, leading to cavitation issues, especially in compact designs where the evaporator cannot be placed at the highest point, and existing solutions require additional components or complex configurations.
Innovation Solution
The system is designed to utilize gravitational flow by positioning the evaporator lower than the condenser, creating a natural circulation that collects liquid working medium at the pump inlet, with optional features like a bypass valve and sensors to manage flow height and temperature, ensuring sufficient Net Positive Suction Head (NPSH) for trouble-free startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the evaporator is positioned at the highest point to enable automatic working medium collection, then the working medium distribution is improved, but the overall height of the system increases
Solution Approach 1:
The patent inverts the conventional arrangement by positioning the condenser at the highest point instead of the evaporator. This inversion allows the system to achieve proper working medium distribution through gravitational flow from the condenser to the evaporator, while maintaining a compact overall height that fits within standard containerized ORC system dimensions.
2Reliability
If additional pumps are used to convey working medium to correct points, then the starting reliability is improved, but the device complexity increases
Solution Approach 1:
The patent implements self-service by designing the system to automatically distribute working medium through gravitational flow during startup. The condenser positioned at the highest point naturally delivers condensed working medium to the evaporator and pump suction line without requiring additional pumps or external intervention, thereby maintaining starting reliability while avoiding increased device complexity.
3Reliability
If valves are used to flush system parts with liquid working medium, then the working medium distribution is improved, but the device complexity increases
Solution Approach 1:
The system performs self-service during startup by utilizing the temperature difference between the heated evaporator and the condenser to create natural circulation. This eliminates the need for valves to manually flush system parts, as the working medium automatically flows to where it is needed through the temperature-driven circulation pattern.
4Productivity
If the pump temperature is higher than the condenser temperature, then the pump operates more efficiently, but cavitation occurs due to insufficient NPSH
Solution Approach 1:
The patent applies preliminary action by positioning the condenser at the highest point to pre-establish a reservoir of condensed working medium that naturally flows to the pump suction line before the pump starts operating. This preliminary gravitational flow ensures sufficient NPSH is available at the pump inlet, preventing cavitation even when the pump temperature is higher than the condenser temperature during normal operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for reliable and cavitation-free startup without additional components, reducing the need for inert gas and maintaining system efficiency, while also reducing the required amount of working medium and extending maintenance intervals, thus lowering operational costs.
Implementation Method 1
an evaporator for evaporating the working fluid
Implementation Method 2
a condenser for condensing and possibly supercooling the working medium
Implementation Method 3
the fluid in the circuit flows to the evaporator by gravitational forces
Data Source
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AI summary
A thermodynamic cycle device comprising: a working medium; an evaporator (2) for evaporating the working medium; an expansion machine (3) for generating mechanical energy by expansion of the evaporated working medium; a condenser (4) for condensing the working medium; and a pump (1) for pumping the condensed working medium to the evaporator, wherein the geometric arrangement of the evaporator is selected such that, before starting the pump, the condensed working medium can flow from the condenser to the evaporator by gravity and the working medium can circulate in a closed loop via the evaporator and the condenser, thereby in particular providing a predetermined supply height of the liquid working medium at the pump.Furthermore, a method for starting the thermodynamic cycle device according to the invention, comprising the following steps: applying heat to the evaporator and evaporating the working medium in the evaporator, causing the working medium to flow to the condenser; condensing the working medium in the condenser; starting the pump when a predetermined supply height of the working medium at the pump is reached or exceeded.