Which Organic Fluid should I used in organic rankine cycle ?

[Muhammad Zeeshan]

I'm trying to make a low temp heat exchanger but feeling difficulty in selecting a type of organic fluid
some are very toxic, some are not environment friendly.
Is there anyone who could suggest me the working organic fluid but it should not be water.

 

[Bystander]

What temperature range?

 

[Muhammad Zeeshan]

300 to 500 degree celcius

 

[Muhammad Zeeshan]

500 is max
lets consider it just 300 degree celcius

 

[Bystander]

300 to 500 degree celcius

... and, why not water?

 

[Muhammad Zeeshan]

... and, why not water?

from 300 to 170 degree Celsius I've to use the temp range so water will not be efficient

 

[Bystander]

not be efficient

?