If you are referring to 2 fans on your CPU heatsink, you would want both of them to move air toward the rear. That would likely mean that the one toward the front of the case would blow air through the heatsink fans and the other one would suck air from the heatsink fins.
If you are referring to your case rather than your CPU heatsink, you generally want fans on the front side of the case to blow air into the case and fans on the backside of the case to suck air out.
A picture would be worth a thousand words here as I'm not familiar with your case. It sounds like the case has the traditional front intake fan and one rear facing, you then have the stock intel cooler fan which blows down over the CPU with case air. But this is a guess. Please clarify and if possible provide a picture of the inside front, inside mobo, inside rear and inside case top.
Are there any minimum speed of CPU cooling fans? How do i check speed of CPU fan before buy them?
When you say "CPU fan", do you mean the CPU itself? Or do you mean case fans?
The rpm of any fan is usually given in its description and usually is anywhere from 500 rpm on up.
In electronics, PWM normally refers to phase width modulation, but I don't know exactly where that is within a PC.
Its the mosfets on your board that controls voltages. Typically all around the CPU socket.
Some motherboards may actually have Heatsinks here as well.
Getting airflow in this area should bring that system temp down a bit, but as I mentioned earlier, if that is indeed what its refering to, you completely normal.
Most decent CPU air coolers will actuually blow some air down in the area, or help pull hot air away.
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