Study the condensation of steam at different temperature levels

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David Holden 13T Physics Investigation

 For my physics coursework, I have to decided to study the condensation of steam at different temperature levels, I will then set about studying how to prevent condensation of steam on a general household object that is frequently subjected to steam on a daily basis – a sheet of glass (eg. A mirror in a bathroom)

 It became apparent to me that studying this topic would not be easy when I put some thought into it, my initial idea was having a mirror, that would heat itself as more water vapour entered the atmosphere, preventing water vapour condensing on it. (A simple example of this is when spectacles are ‘steamed up’, run them under hot water for a few seconds to wash away the condensed water, and more importantly adjust the temperature of the spectacles to the surroundings to prevent further condensation of water.)

 For a practical everyday mirror for this purpose, it would be easy to run a heating element along the backside of the mirror (to conduct the heat through to the mirror surface) and link the heating element to a variable resistor, which in turn would be connected to the hot tap handle, so in theory, the more hot water flowing through the bath tap/showerhead, the more water vapour produced so in turn the hotter the mirror becomes. This idea is easy enough, but the problems start with calibrating the variable resistor, ie, how to reduce the condensation levels effectively using the heating elements at temperatures that will least effect the glass surface. This idea indicated that I would have to study the condensation of steam at different surface temperatures, as this is a major part of my experiment, I set around devising a suitable method for collecting significant samples of condensation on a glass surface.

Preliminary design 1

 My first idea was as above, but a few problems arose for experimental purposes.

  • It would be very difficult to subject the mirror to the steam evenly.
  • How was I going to measure the condensation collected?
  • How was I going to measure the temperature of the surface of the mirror, and in turn be able to adjust the temperatures of the heating element?
  • What was I going to use for the heating element?

Scaling down my preliminary experiment answered some of the questions, I decided upon subjecting microscope slides to steam, as microscope slides are thin and will conduct heat very easily, so would be responsive to changes in temperature of the heating element, and are fairly small so would be easy to evenly subject to the steam. It became apparent that heating the microscope surface will most easily be done with nichrome wire, which is available and easily manipulated as it is a thin wire.

To heat the microscope slide evenly, I was going to have to distribute the nichrome wire evenly upon the rear surface of the slide, like so.

To keep the nicrome wire in place, I decided upon sandwiching it between two microscope slides, then sticking them together with some araldyte glue. Another problem came around with measuring the temperature of the surface of the slides, to monitor and calibrate the temperature of the nicrome wire, the easiest solution is to make a thermocouple and attach it to the surface.

The main obstacle in this experiment is measuring the rate of steam condensation, I think its important that this is dynamically recorded to give me a good idea of how fast the steam collects up on the surface. I had two ideas for this.

  • Shine light through the microscope slide and use a LDR to detect the absorption of light by the condensed steam
  • Dynamically weigh the entire slide, and as one cm3 of water = 1 gramme, I will be able to detect the increase in mass as the condensation collects on it.

The first idea was proved flawed, as the water vapour would interfere with the light shining on to the LDR, and that as more and more water condenses, tiny droplets form, and these are basically tiny convex lenses which will scatter the light in all directions, not asorb it. There might be a suitable solution to this idea, and I may explore it again for the second part of my investigation.

I decided to use the second idea and stick the microscope slide sandwich on a sensitive set of scales which would be connected to a data logger which in turn would be connected to a laptop. I decided upon using a kettle for the source of steam, as this will always heat to the same temperature on each boiling of the water.

A factor I need to consider is boiling the same amount of water each time, because boiling a large amount of water will produce more steam than boiling a small amount of water. Of course I cannot be sure that each time I boil the kettle the same amount of water vapour will be produced within a certain amount of time but this is one of the reasons why I will be repeating the experiment.

My first idea would look like this.

This idea was going to need serious reworking after running a few preliminary tests and putting some extra thought in due to the following reasons.

  • Although advantageous for the reasons already state, the slides were only going to collect a mass of condensation in the order of 10-3 grams, and even the most sensitive balance in school will only just record as low as 10-3g, and at that scale there are too many variables to consider, such as convection currents and wires.
  • The kettle was a good idea, but for subjecting the slides to a constant flow of steam, a kettle would not be suitable as it boils the water, then stops, when the water cools down so will start producing less steam after boiling.
  • As the balances I am using are electronic, subjecting them to steam is not the best idea as I will soon find myself in a rather large debt to the physics department in school, also another thing against this idea is that steam will collect on the balance plate as it is steel and will obviously be cold. This would dramatically affect the results.
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Of course I will take all of this information in to consideration when I’m building my experiment with a mirror (or sheet of glass) and I’m not so interested in a dynamic collection of data showing how condensation collects on the surface, and this has proved very useful, but I had to rectify the problems so I could carry on designing a preliminary experiment.

Preliminary experiment 2

To increase the volume of condensation on the surface I decided that increasing the surface area was my best option, a way of getting around using a large sheet of ...

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