Another important consideration may be the material of the enclosing case. If the case is made of plastic, or any thermally insulative material, it will contain the heat as the components heat the air within the case. A case of aluminum or any thermally conductive material will shed heat to the surrounding air as the interior heats. Cooling fans have been a part of PCs since the first. Rather than explain the history or operation of fans, or the thermodynamics of conduction, I'll instead point out a few facts on improving your cooling.
Turbulent air cools better.
Say, for sake of argument, you have a simple tube with a fan in the middle. The fan pulls air from one side of the tube, and blows into the other. If you have a hot component on the exhaust side of the fan, it will be more efficiently cooled than on the intake side. This is because the air on the exhaust side of the fan is more turbulent. For lack of a better explanation, the loops and whorls of turbulent air moving across the surface pick up more heat.