Practical 1

REVERSE ENGINEERING ⇄

Our first Practical together! 

In this practical, we have 2 parts to complete:

1. Dismantle the coffee machine to see the different parts and find out their different functions.
2. Making batch coffee and calculate the energy consumption of the heating element in the coffee maker.

DISMANTLING:

Firstly, we dismantled the top part of the coffee machine:

From the outer view of the coffee machine, we found out that there is a hot plate at the on the bottom half of the coffee machine to place the jug so as to keep the coffee (brown water) in the jug warm. After dismantling the top, we realised that there is a spring present at the bottom filter holder. Then we wondered. 

Why is a spring needed?

- When pressure is applied onto the handle connecting to the spring, the spring compresses and there will be an opening between the liquid and the filter holder, allowing coffee (brown water) to flow into the jug placed at the bottom of the coffee machine.

We flipped the coffee machine upside-down and started unscrewing the screws at the bottom of the machine.

Top View After Unscrewing:

As seen from the image above, there is a heating element that heats up water in the horseshoe tubing as well as the hot plate. we then took out the horseshoe tubing and the orange rubber connected to 2 ends of the horseshoe tubing. 

After experimenting on the orange rubber tube, we concluded that is it a check valve so as to make heating more efficient, preventing hot water from re-entering the tubing. We then realised, other than the tubing there is nothing else to push the heated water up to the filter. So:

How does the heated water travel upwards above the initial water level and into the filter?

When water is heated in the horseshoe tubing by the heating element, water expands. Density then increases and vapour pushes the heated water up and into the filter causing a slug flow*. 

Slug flow* - two phases flow. 

REASSEMBLE:

After finding out the different components to this coffee machine, we had to reassemble it. Reassembling was not difficult for our group as we labelled all our screws, so that it would be easier for anyone that took over to reassemble it without wasting any time.

BATCH COFFEE:

Afterward, we made a batch of coffee using a non-dismantled coffee machine.

Before starting and during the experiment, we measured all items that was needed for any calculations afterwards.

1. Mass of coffee powder used.
2. Volume of water used.
3. Temperature of tap water.
4. Mass of dry coffee filter paper.
5. Temperature of coffee powder.
6. Mass of beaker.
7. Time taken to brew coffee.
8. Power (W).
9. Average Energy Reading (KWH). 

After coffee is brewed, we took the measurements of:

1. Temperature of the brown water.
2. Temperature of residue in the filter.
3. Volume of brown water in the jug. 
4. Mass of condensate on coffee machine lid.
5. Mass of wet coffee filer & spent coffee powder.

Hence, using energy balance, we calculated 4 parts:

1. Energy of brewed coffee in the jug.
2. Energy of retained water in the filter.
3. Energy of powder in the filter.
4. Energy of vapour.

Thus, we conclude our first practical!! 👍😀