I played around with one of my 168 watt Peltier coolers today and heres what I got while running it for about 2 hours at 11 volts 7 amps input using a big aluminum heat sink on the hot side and an old CPU heat sink on the cold side. The other Peltier cooler and the quarter are for size reference. These coolers are approximately the same size as a standard CPU.
My IR thermometer says the hot side is about 83 F and the cold side is about 22 F. No heat sink compound or clamping was used.
View attachment 36130
I dont know about you but that just seems to say mini beer cooler to me!
To start I think whoever sold you the TEC appear to of quoted the specs at hotside temp of 50ºC.
This increases the voltage and current rating and also the Qmax, i.e. makes it look better... Then they went and quoted the input power instead of the Qmax. It is the Qmax you really want.
I tend to work with hotside 27ºC specs. At 27ºC Bismuth telleride couples have a voltage of 0.1227v so a 127 couple unit like yours, at hotside temp of 27ºC has a voltage of 127 x 0.1227v = 15.6v this is the true voltage of the unit (people quote variously 15.2 - 15.8 ) and your current will be 10amps (it's a standard value.) so your unit is a 12710. 12710 have a standard Qmax of around 90w (it varies a bit depends who makes it.)
So to me you a 12710 90w unit.
The reason for clamping is that in normal use TECs vibrate. This vibration is sufficient to affect the heat transfer also eventually after long continued use it can break down the solder joins. TECs will work happily without clamping but if you do clamp you will get a better performance from better heat transfer and a longer life for the TEC. Also the use of a quality TIM will make quite a difference.
Your difference of 60ºF while it might seem impressive is nothing for 11v in for a 15.2v unit, it is only 15ºC, in terms of performance it is piss poor. Perhaps your heatsinks don't help but with clamping, TIM and voltage tweaking you should be on
at least 25-30
ºC difference (77 - 85ºF) or even more, after all you very little load (it is under load even in free air.)
I got 28ºF from an 80w Qmax. (15.2v) unit running at 4v !! I had a vapochill micro on the hotside, silver TIM, a 10mm hotplate and a 5mm coldplate and it was running in free air same as yours with an ambient of 20ºC (68ºF it was outside.) And I thought that was not very good !!!