i'm using a peltier device to cool my equipment but it seems not to be effective cause it dissipates too much heat. do you know any other effective cooling device which is very small like peltier. or can you guys help me with the best power supply for my peltier it's power rating is 25W.
A peltier device does not remove heat. It moves heat from one side of the device to the other side while adding its own power consumption in heat. Therefore, the hot side of a peltier will be hotter than the equipment you want to cool in the first place.
So, no matter what, you will still have to do effective cooling on the warm side of the peltier element.
They only make sense if you did a proper thermal analysis of the situation, and you know the thermodynamic effect. If you do not know usage of a peltier makes sense, it very probably doesn't.
In general, they are mostly used in applications to produce a chill (as in for beverages), if a mechanical heat pump would be to big - in full knowledge of the added power, low efficiency etc - and including proper cooling for the warm side. For cooling electronics - not so much.
If you are trying to cool something that's hot, like a chip, you do not need a Peltier; the temperature gradient from the hot device to the cooler environment will naturally cause heat to flow out of the device. To increase the cooling effect, you only need to prevent the heat from the device from warming up the environment around it, which would reduce the gradient. Fortunately, this is easily accomplished with a good thermally bonded heat sink and fan. The Peltier device will actually only increase the amount of heat that must be removed from the system, as it dissipates energy (as heat!) in order to move heat.