Monday, April 5, 2010
Day 7
Saturday, April 3, 2010
Day 5 - Wool
Friday, April 2, 2010
Day 4
Thursday, April 1, 2010
Day 3 - Dali Atomicus
Wednesday, March 31, 2010
Day 2
Tuesday, March 30, 2010
New Idea
Thursday, February 4, 2010
Time and Scale - Part 1
Saturday, January 16, 2010
Hair Drying - An Engineer's Perspective.
So, while brushing my teeth this morning I noticed that Allison's hair dryer has a power consumption rating of 1875 watts. Not being familiar with hair dryers it appears that is essentially how manufacturers determine which one is 'better' than the next and thus which should cost more - so you get 1000 watts for $10 and 2000w for $25 or similar. (Though in that case you get more watts per dollar for the cheaper one)
Being an engineer this seemed like an entirely arbitrary measure of the effectiveness of a hair dryer. Thinking about what matters in drying hair: the amount of power it is sucking from the wall does not particularly matter. The amount of it can transfer to the air that is passing through the device is more important. Thus, I propose that an efficiency metric is more of a meaningful 'this hairdryer is better' measure than the ultimate out-of-wall watt rating.
Take for example two 1500w hair dryers. Measure the remaining energy at say 10cm from the exhaust nozzle where the user's hair typically is. If one is able to deliver 500w at that distance it would be 33% efficient. (33 percent of the wall energy is transferred to your hair) If the other only delivers 150w at the same distance, it is only 10% efficient, and thus inferior.
This could then get the shopper to value energy efficiency - a very 'green' thing in the current age. And then the hair dryer makers could come up with more efficient heating coils to further increase their efficiency ratings and outperform the competition. It's a win win. Customer's get dryer hair faster, less energy is used in the process.