Deleting Image Generated By Chart Control

Question

Is there a way where we the rendered images from chart control be deleted automatically? If not, is it possible to use a dir outside my solution folder, say D:\ChartImages. Below is my AppSettings but the deleteAfterServicing=true is not working

 

<add key="ChartImageHandler" value="storage=file;timeout=20;dir=c:\TempImageFiles\; deleteAfterServicing=true;" />

Thanks for any help.