# Figuring out the split for power dissipated?

1. Apr 4, 2015

### Valkarie

Hello everyone!

This is my first post, I've done a bunch of searching on this forum which has yielded me quite positive results, so thank you for all of your posts which are a bloody gold mine of information.

Although I've gotten quite a lot of information that has been useful, I'm still having a problem with understanding what I have to do and was wondering if anyone could offer any input for this problem so I could wrap it together.

Basically, I am attempting to build a humidifier, which works by evaporating a liquid and releasing it into the room. The problem I am having is attempting to build an open loop model whose input (voltage -> power) can be related to the amount of mass of liquid which is being evaporated.

I am investigating how the power dissipated though a heating element relates to how the energy lost is split amongst different sources of losses. The heating element will boil some of the liquid it is in contact with, it will heat up some of the air around it, it will lose some energy via radiation. Its internal energy will also heat up and it will itself heat up as power is provided to it.

Lets assume we have a heating element made from a simple resistive metal, this heating element has a constant layer of a fluid on its surface (thin layer). The element will boil the layer of liquid and this will be carried away by a constant stream of air moving away from the element. Thus we can assume that the humidity, pressure and temperature of the air are constant within the control volume.

As the resistor dissipates energy, how do I know how much energy is being disspiated into vaporizing the liquid and how much will be lost into the surrounding air?

So far I have set up an experiment to find the temperature of the resistor in the operating conditions, and compare this with the theoretical temperature assuming no energy is dissipated and all energy goes into raising the internal energy of the resistor, then comparing the two to find the energy lost to the combination of the surroundings. But it all seems very shambles to me.

Can anyone point me in the right direction?

2. Apr 9, 2015