Stacking of Peltier units - Part 2 

Up here in Sweden, it is a bit different. We usually have 25-28°C on the hottest days, and rarely, I see temperatures above 30°C. Cold... Once I experienced -25°C. So, I can imagine how could it feel to sit on the top of the Peltier. :)

Yes, because the transferred heat would increase, which would automatically imply a drop in dT. Either you can achieve high dT or high Qc, but not both at the same time.

Yup! You have the Joule heat, *plus* the pumped heat showing up on the hot side. The disadvantage is that you can not achieve too high temperatures. Otherwise, you'd damage the module.

Hi! I will not calculate it very precisely but let's check the numbers roughly and let's think about some ideas. First of all, the simplest one: 1 unit is 16 cm^2 surface area. Either you have 192 cm^2 (TEC12715) or 1024 cm^2 (TEC12703). So, there is a factor of 5 in the surface area. More surface area, more heat transfer. Your question is underdetermined, and you did not tell what temperature difference you can maintain. I will say DT = 40°C. The 12703 will give you roughly 22 W / unit (264 W total), and the 12715 will give you 80 W / unit, so 960 W total. So, the factor between the cooling powers is also around 5 (rather 4). If you can cool the 12715 properly, go for that. Less parts, less complexity. If you don't have appropriate cooling, you might want to go for the 12703, because of the small contribution of the Joule heat term. But your question is not so precise. you haven't told anything about your cooling, about the required temperature difference, ambient temperature...etc. I cannot answer it properly without these details.

Thank you for wanting to help me because it's not my profession ... so I have a mushroom farm and two 40 cm diameter fans on the wall and 400w each, on which I want to place two car radiators ... it would flow through them water (slightly stronger pump) and cooled by peltier modules and aluminum blocks, so that I would not enter the nursery hot air outside but cooled (and heated in winter) ... the desired temperature in the nursery is about 17 degrees ... the air is injected into every 45 minutes and lasts 10 minutes ... air conditioning is a bad solution because when the hot air enters it cannot cool it and in 45 minutes a new one is inserted ...@@CuriousScientist

To say that I would use the hot air from the cooled peltier module (350W fan) for incubation in the next room where it takes about 25 degrees ...

If the air conditioning cannot deal with the hot air, the Peltier will have even more struggle since it is about 3-4 times less efficient. If you cannot solve this by air conditioning, Peltier will be even more difficult. I assume that the mushroom farm has a relatively large volume. In that case, it is not feasible to solve the cooling/heating with Peltiers. I think you should think about improving the AC instead.

@@CuriousScientist The room is about 200m3 ... I would be pleased that if it is 30 degrees outside, 20 degrees air enters ... expectations are that if the air passes through a car cooler in which the water in aluminum blocks is cooled by almost 2KW, it can to cool the air at least 10 degrees ... I'm not sure if it's worth a try ...

This is literally a combination of TEC12715 (Bottom) and TEC12706 (Top). If you change the Peltiers, there are 2 very important things to keep in mind: 1; the bottom Peltier has to be able to provide a cooling power that can deal with the full amount of heat coming from the top unit. The top unit has 2 heat sources: one from the current that runs through it (P = I *U), and the other is the heat pumped from the cold side to the hot side (Qc or cooling power). 2; The system which cools the hot side of the bottom Peltier has to be able to deal with the bottom Peltier's total rejected heat which is P = I*U, plus its Qc, which is in this specific case is the product of the terms mentioned in the first point for the top Peltier. This makes sense of course, because if you want to cool the top unit, you need that cooling power to be available in order to remove all the rejected heat. In this case, you will need a cooler that can take away 3-400 W. If you don't have any specific application where you can use these low temperatures, then it does not worth it. This will not cool down any significant heat source.

Less then 30 deg

Thanks! Yes, I guess this very small closed cycle system cannot do any much better despite that the calculations show something different. I think I will be happy with the -40°C.

I know. I also said it many times that I am trying to demonstrate the minimum achievable temperature.

🙌

Yes, this seems to be the limit. I will try that mist, don't worry, I am just waiting for some parts. I was thinking about the system, and I came up with some sort of design for the fan. That will be strictly for air cooling of course, so mist+air cooling. I just need to receive the parts, then I can upload a whole bunch of videos with that type of cooling.

Why?

@@CuriousScientist I thought that might work better than adding cold water like you did.

I see. Yes, probably better, sure.