Measuring Heat Loss with Arduino + PID Loop?

Hi all,

I am testing some materials for beverage insulation application.

I want to pour boiling water into a glass beaker and then measure the heat loss through the thermal insulating material that I have wrapped around the beaker. The beaker will sit on a hot plate.

Is there a way that I can measure the heat loss with a PID loop? For example, observe the power draw of the PID loop as it tries to keep the temperature at the target temperature?

Yes, you could get a measure of insulation effectiveness by that round-about way. That would be a good project to learn about Arduino and PID, but unnecessarily complex if all you want to do is measure and compare insulation materials or techniques.

You would probably find that heat losses from the hot plate itself would significantly affect your results.

Why not : 1) Insulate the beaker, including the base 2) Add measured quantity boiling water 3) let it cool 4) Use arduino & suitable device to measure & record temperature drop as a batch of boiling water cools 5) Evaluate and compare results

That's simpler ...

HI,

As JimB says you need to be a bit more aware of the external influences of your project.

If you are looking at the insulation quality of the container you need to measure the temperature at the inside surface of the material and the outside surface of the material. Do this in a sealed cupboard to keep the external conditions stable, as temperature of the environment will be a factor.

Just putting a container on a hot plate and measuring how much energy it takes to maintain a temperature is a valid approach, but you must measure the environmental temperature as well, as heat transfer is proportional to the difference in the inner and outer temperatures.

Tom......... :)

That is if my Thermodynamics Lecturer is to be believed, although he did then get a gov grant to go to the Gold Coast and study the Fluidics of JellyFish.

if you sit back and contemplate this project, you have a continuos drive toward equaibrium on a never ending basis.

you have the temperature inside of the container.

an interesting point is that the center never cools or heats directly, it is strictly and only the outside the changes temperature.

the skin of your wrap will shed energy in an effort to reach and equilibrium with the environment. as that cools, the section just inside will see a temperature gradient and the heat will flow.

if you put the container in a cupboard, you can greatly effect the external temperature as the cupboard comes towards equilibrium with the mass.

what you are asking for is not that hard.

you control the energy to the hot plate. using your PID to keep the fluid at your setpoint temperature. now, on your second circuit, you monitor the current and voltage of energy being used to keep the fluid at that constant temp.

should be pretty straight forward to have those two loops.

the real question is where to put the temperature sensor that monitors your liquid.

Brennn10: I want to pour boiling water into a glass beaker and then measure the heat loss through the thermal insulating material that I have wrapped around the beaker. The beaker will sit on a hot plate.

I suspect you need to think more carefully about what you are measuring and, especially, whether the results you get are generally applicable or whether they are specific to your experiment. I imagine a hot plate will completely confound the experiment unless you can be absolutely sure that it cannot heat the environment surrounding the beaker.

I think @JimB's suggestion would be best, as well as being simple and repeatable. How do physicists do it? They could do this experiment very accurately 100+ years ago.

If I had to heat the water to maintain a constant temperature I would use an immersion heater inside the water in a fully insulated beaker - but I can't see any advantage for the extra complexity.

...R

Robin2: How do physicists do it? They could do this experiment very accurately 100+ years ago.

you mean put in a thermometer, record time calculate surface area and then do the math ? I think 100 years ago, they could just measure time till a temperature was reached I am a little baffled at the set-up. a hot plate would have to put all heat into the fluid, the immersion device would be better at that.