Why Hardware acceleration is slowing down the Export in premiere pro??

I was using an old system on i3 Intel processor with 8 GB RAM. Considering the old configuration, it was taking some time to render/export the video from premiere pro. 

I recently upgraded to following System, without Graphic card.

My computer configuration
Processor 11th Gen Intel(R) Core(TM) i7-11700K @ 3.60GHz 3.60 GHz
Installed RAM 32.0 GB (31.8 GB usable)
System type 64-bit operating system, x64-based processor

As the i7 supports the Hardware acceleration, I turned it on, but It seems it actually slowed down the export. 
A 15 min video with 2 layers of videos side by side & with lower third in entire video used to take 45 min in old PC. 
In newer one with Hardware acceleration, it is taking 3 hours. I don't know why?

My export setting are as screen shot:

My CPU usage with acceleration is 

 
I have gone through all many articles and answered given here, mostly all recommend using GPU acceleration, but I am getting opposite results.