Heat and cooling a hot-plate with a peltier module

[sammy2010]

Hi all,
first time poster here.

I want to build a small hot-plate which I can heat from room T (eg 25degC) to about 120degC and then cycle between that and 60~75 degC (I will need to vary this) for several cycles. The material of the hot plate is open; I am currently considering aluminum or brass. The overall size of the area that I need heated is about 30mm square and the plat will have a thickness of ~4mm. I have considered using a resistance (cartridge) element for heating and a water circuit to cool but I don't actually have running water in my "workshop" (at least at the moment....). Hence I am looking at options and considering a peltier heater and am looking for advice....

I have no experience of using these heaters and the kind of questions I have are:
- Would a peltier module be appropriate for this kind of application?
- From RT to maximum temperature I have a deltaT of 95 but I am happy enough if the cold side heats up (from RT) so am I correct in thinking that the deltaT I would need when checking module specs is 60?
- How are such units typically controlled to cycle between 2 temperatures?
- How are such units thermally isolated from their mountings?

I would appreciate any help and guidance you can offer...

Thanks in advance,
sammy

 

[Boncuk]

I guess you're on the wrong track here.

All a peltier element can do is creating a temperature difference of 65deg/C.

To achieve 120deg/C on the hot side the "cold" side must have a temperature of 55deg/C.

To make a hot plate I suggest using a resistive heating element (e.g. heaters of irons).

Removing the handle with the body you'll have a nice heating plate made of hardenend aluminum and absolutely plain. Just turn it upside down. Don't remove the temperature switch.

Using the lowest setting you'd be able to get the desired 120deg/C.

Boncuk

 

[Reloadron]

I agree with Boncuk and would consider using something like this. Control becomes easy also and material like this can use mains power or lower DC voltages like 28 VDC.

Ron

 

[sammy2010]

Boncuk and Reloadron,
thanks for your responses. I understand the benefits that either of these solutions would have for heating, but I also need to cool it down from 120degC to 60~75degC. I think that a cooling system would definitely be needed to cool in a realistic time. Hence my proposal to use a peltier module for cooling (and I thought it could also be used for heating). Would a peltier be appropriate for this cooling function?

 

[Boncuk]

Of course you might use a peltier element for cooling.

Since you want to cool the (initially) hot iron you should consider a large heat sink on the "hot" side of the peltier for quick reaction.

Just bare in mind that peltiers can create a maximum temperature difference of 65deg/C.

The most powerful peltier offered by my electronics supplier measures 40X40mm and has 8.5A of current flow at 15.4V (~130W).

It should cool down your heating area within short time (provided heating is off ) if you use pulse width modulation to reduce cooling power when the desired low temperature is approached.

Boncuk

 

[Boncuk]

I agree with Boncuk and would consider using something like this. Control becomes easy also and material like this can use mains power or lower DC voltages like 28 VDC.

Ron

Hi Ron,

I'm shocked!

For US$88 you can purchase as many as 10 irons! (and have ten handles for ice bowling. )

Regards

Hans

 

[Reloadron]

Hi Ron,

I'm shocked!

For US$88 you can purchase as many as 10 irons! (and have ten handles for ice bowling. )

Regards

Hans

HI Hans

Damn, I never looked at the price.

I have used those at work and I don't ask what things cost, I just buy things. Me thinks me is losing touch with reality.

I agree with your heating suggestion. Much lower cost. As to cooling, yes, a peltier should work. Not sure how the plate will be configured for heating and cooling both.

Ron