I like my cup of latte in the morning. However, I am too lazy to go to a local coffee shop and, being a typical frugal engineer, I am opposed to spending hundreds of dollars on a machine that will make espresso for my latte. Hence, a basic moka pot and a cheap little milk frother provide the start to my daily routine.The moka pot is a stove top device, commonly used across Europe to make an espresso-like beverage. It basically heats water to near boiling which pressurizes the system. As the system pressurizes, water is forced upward through the coffee grounds and into a collection pot, a single pass through the grounds keeping the coffee from becoming over-extracted and keeping the temperature below boiling. This varies from the traditional percolator style coffee pot which uses boiling water and continually circulates the water/coffee through the grounds using gravity.
After experimenting with various coffee brands, roasts, and grinds, trying to find the best combination to suite my pallet, I went to Google. I came across several blogs and discussion forums on how to make the best coffee in a moka pot. Some folks insist you need to start with cold water, other say hot, and some say boil it first. Some say you should tamp the coffee to compact it, others say don’t tamp. Some say you should mound the coffee in the funnel, yet others say only fill the funnel level with the top. ARGGHH! So many self-claimed experts trying to push their two cents into my morning ritual.
At the same time, the boss was hounding me to become more proficient with compartments and TD Direct®. And of course, we are always trying to create sample problems for our customers. Does anyone need a model of a moka pot? No, but it could be an interesting challenge from the fluid perspective.
I decided to solve two problems at once, appease my boss and model a moka pot to see if any of the web-based theories have any basis. Hence my venture into modeling the perfect latte to test some of these theories.
Recently, long-time friends (and self-proclaimed espresso connoisseurs) stopped by for a visit. As we sat drinking tea and coffee with fresh baked blueberry scones, they told me about their vintage Atomic Coffee Maker. It was designed and patented by the Italian Giordano Robbiati back in 1947, such an artful fusion of form and function. Not only does it make wonderful espresso, it also steams the milk. I fell in love with the mid-century organic lines of the machine. True art in the eyes of a fluids engineer. Unfortunately, production of the Atomic stopped in the mid 1980s. More recently, an Australian company Ikon Exports and Bellman Co., in Taiwan started reproducing these iconic espresso machines, the La Sorrentina™. Not sure they are still producing them, but maybe I will let loose with some money and upgrade, assuming I can find one. Consider it a piece of art for my kitchen, not to mention a great conversation piece. As of today, my pursuit for a La Sorrentina begins. Hmm, maybe I can submit it on an expense report as research for another model.
Back to the topic of my morning coffee and moka pots. If you are interested, the final model and documentation can be downloaded from our website. Here is a video showing the heating of the walls and the movement of the various liquid/vapor planes during the brewing process.