Third week of Introduction to Chemical Product Design.
4th May 2021
Assembly & Disassembly
Before we started the practical, we were given the task of disassembling and reassembling a coffee machine as shown in the picture. When we were first given the coffee machine, we were given the challenge of finishing the task within an hour. As the challenge started and we started disassembling the coffee maker using tools such as screw drivers, we realized that the coffee machine can be split into 2 different sections, one being the top half which contains the water and coffee grains whereas the other part contains the heating element and electrical component. As we ventured further into the heating and electrical component, we realized that in the heating element, there is a pipe that is connected to the heating element which contains water. As the heating element heats up, it will bring the water in the piping into a boil and convert it into steam. This steam will push up the water through a check valve in the piping and into the coffee grains at the top section to produce coffee. After disassembling the coffee machine, we realized that it was a machine that used chemical engineering principles such as heat transfer and conduction. As we disassembled the coffee machine, we did not encounter many problems as it was relatively simple to do. The real problems started after we began to reassemble the machine. The problematic part came when we had to adjust the wiring inside the bottom component. Since the wiring had to be adjusted to a specific position, we had much trouble finding out how to position it. After a couple of minutes of trial and error, we finally manage to do it! Luckily, we completed it in the nick of time and manage to complete the challenge.
Actual Practical
For the actual practical, we were tasked to determine the energy consumption of the coffee maker BD100® by brewing some coffee. We utilized an electricity consumption monitor to help us measure the energy consumption of the machine at any time interval.
Summary of procedures:
The water tank of BD100® was filled with 300ml of water and its temperature was recorded.
20g of coffee powder was added into the filter holder.
BD100® and the electricity consumption monitor were plugged in together and the mains power supply was turned on.
Start timer.
Temperature and average electric consumption were recorded every 30 sec.
After coffee is made, measure temperature of coffee.
Record electricity consumption value.
Measure mass of coffee made.
Measure mass of filter paper.
Clean the coffee machine.
Perform house keeping..
#1: How did we obtain the mass of a piece of filter paper accurately?
We took 10 pieces of filter paper, weighed them altogether on the electronic scale, and divided the mass by 10 to get the mass of a single piece.
#2: How did we collect and obtain the mass of the condensate?
At first, we ran into a roadblock, as we did not know how to record the mass of condensate of lid. Our first method of attempting to collect the condensate escaping was to stuff a tissue paper into a small beaker taped over the small holes it escaped from. We would first weigh the dry tissue paper and wet tissue paper, then subtract the mass of the wet from the dry to determine the mass of the escaping condensate.
We later substituted the tissue for a towel as we also had to wipe off any condensate on the surface under the lid, as a tissue would not have the absorption capacity we needed. However, we scrapped this method as our second method eliminated the need for collection.
Our second method was to work backwards, using the mass of our starting amount of water subtracted by the mass of black water we had at the end of the brewing to get the mass of the condensate. This way, we would not have to worry about the collection of the condensate since we were focused on how much black water we had after the coffee brewing.
#3: How did we get the average temperature of the coffee powder?
We decided to use the digital thermometer to measure the temperature of the coffee powder. We would open the lid, stick it into the coffee powder and recorded the temperature in 30 second intervals. We realized that we could keep the lid open and any condensate that escaped into the environment would be no different if it condensed onto the underside of the lid, as we were calculating its mass using the reverse method, with no need for collection.
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