Closed cycle gas turbine is divided into two types, namely gas turbine with direct closed cycle and gas turbines with indirect closed cycle. In direct closed cycle gas turbine, cooler gas is heated in the reactor and expands through turbine, cooled in heat exchanger and it is compressed back into reactor. This cycle can also use other gas. There is not radioactive gas be discharged into atmosphere in normal operation. The most suitable fluid for this cycle is helium.
|Figure 1: Direct Closed Cycle Gas Turbine|
While on indirect closed cycle gas turbine, gas turbine with this cycle is combination of indirect open-cycle turbines and direct closed-cycle turbine, because reactor separate from working fluid by heat exchanger. While working gas was throwing heat into the atmosphere through heat exchanger. Primary coolant material that is usually used is water or helium gas.
|Figure 2: Indirect Closed Cycle Gas Turbine|
In this closed cycle, working fluid is not connected to surrounding atmosphere; thereby its purity can be maintained. This is very advantageous in terms of prevention of damage caused by erosion and corrosion. In this system can also be used with high pressure air up to 40 atm as the installation of steam, but the works did not experience phase change.
The advantages in closed cycle gas turbine are:
- For the same power turbine has a smaller size
- Can be used on high-pressure system
- The use of fuel can be more efficient