# How to control turbine in Organic Rankine Cycle system

• Lei
In summary, the conversation discusses the working principles of a small scale ORC system, where the turbine inlet pressure and flow rate are controlled by a pump and the turbine inlet temperature is determined by the evaporator. The question arises about how to control the turbine outlet pressure and rotational speed, with the answer being that the speed is determined by the load and the pressure is minimized. The conversation also requests for diagrams showing the practical arrangement and thermodynamic cycle of the system.
Lei
I am currently working on turbine design for small scale ORC system to produce power from low-enthalpy heat source. In ORC, turbine inlet pressure and flow rate are controlled by pump, and turbine inlet temperature is determined by evaporator when the flow rate of refrigerant and enthalpy of heat source are constant.
During turbine operation, I am curious about how to control turbine outlet pressure (condenser inlet pressure) and rotational speed. Is the outlet pressure controlled by turbine, condenser or buffer tank? How to change turbine speed?

If everything else is truly constant then turbine speed is determined by the load . Reducing load means speed increases . Increasing load means speed decreases .

I would be very surprised though if everything else did really remain constant . Generally in turbine systems any change results in everything else changing .

Can you post diagrams showing the practical arrangement of components and the thermodynamic cycle for this system ?

@Nidum is correct. You can't begin to talk about speed without first describing the load.

Exit pressure is not "controlled" it is minimized. The lower you can get the exit pressure, the better. For example in a steam turbine cycle like in power plants, a condenser operating at a vacuum pressure follows the turbine.

Hi Nidum and Anorlunda,

Thank you so much for your reply.

The thermal cycle of ORC is shown in Figure below. The refrigerant liquid captures energy from waste heat at evaporator and is vaporized to vapour. Then high pressure and high temperature vapour goes into turbine and expands across turbine passage to produce mechanical energy. After existing turbine, the vapour is condensed into liquid in condenser and the liquid is pumped back to evaporator, initiating a cycle.

The minimum pressure of turbine outlet is determined by the property of the refrigerant and the saturation temperature in condenser.
Nidum,as you mentioned, if the working condition of turbine is stable, the turbine speed is determined by load. Does it mean that the turbine speed is controlled by adjusting generator load?
I will appreciate it if you have any further thoughts on this.
Regards

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## 1. How does the turbine in an Organic Rankine Cycle system work?

The turbine in an Organic Rankine Cycle system works by using high-pressure vapor to turn a series of blades, which are connected to a rotor. As the vapor passes through the blades, it causes the rotor to rotate, generating mechanical energy.

## 2. What factors affect the control of the turbine in an Organic Rankine Cycle system?

The control of the turbine in an Organic Rankine Cycle system is affected by several factors, including the temperature and pressure of the working fluid, the speed of the turbine, and the efficiency of the heat exchanger.

## 3. How is the turbine speed controlled in an Organic Rankine Cycle system?

The turbine speed in an Organic Rankine Cycle system is typically controlled by adjusting the flow rate of the working fluid. By increasing or decreasing the flow rate, the speed of the turbine can be controlled to optimize its performance.

## 4. What is the role of the control valve in an Organic Rankine Cycle system?

The control valve in an Organic Rankine Cycle system is responsible for regulating the flow of the working fluid into the turbine. By adjusting the valve, the flow rate and pressure of the working fluid can be controlled, allowing for efficient operation of the turbine.

## 5. How can the turbine in an Organic Rankine Cycle system be optimized for maximum efficiency?

The turbine in an Organic Rankine Cycle system can be optimized for maximum efficiency by carefully controlling the flow rate and pressure of the working fluid, as well as ensuring that the heat exchanger is operating at its highest efficiency. Additionally, using a high-performance turbine design can also improve overall efficiency.

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