I am designing a 9u rack server with optical ports. I want to implement Thermo Electric Cooler(TEC) for cooling the ICs(switches, FPGAs) on board, so that I can reduce the fan speeds. Is this a good idea, if yes suggest some TEC modules.
TECs aren't magic: they don't destroy heat. That would be a violation of conservation of energy.
All they do is pump heat from one side of its plates to the other while using some energy. When you make one side cool, you still need to cool off the other side of the plate. The other side of the plate will probably get pretty hot, more hotter than the CPU alone.
TECs aren't very good for constant thermal loads, so you're probably not gonna go anywhere with this setup. I don't have any numbers to back this up, but you're probably going to see a tiny decrease of temperature in the CPU while your heatsink gets way way hotter. Not a great idea if you're trying to reduce fan speeds.