Effect of temperature settings on energy efficiency of a hair dryer Angela Taylor Bellwood-Antis High School Grade 11 Problem • I wanted to find out if a hair dryer is more energy efficient on the hot or cold temperature setting. How a Hair Dryer Works http://www.petervaldivia.com/technology/el ectricity/electrical-power.php Power of Hair Dryers – Wattage=power setting • Hair dryers range from 600 to 2500 watts • Mine is rated at 1875 watts • Higher wattage uses energy faster – Higher fan speed=more watts – Higher heat setting=more watts Evaporation • Process in which atoms/molecules in liquid state gain enough kinetic energy to become a gas http://www.tonywhiddon.org Temperature vs. Speed – Cold setting=lower wattage – Less energy=more efficient – Evaporation happens faster at higher temps-less time needed – Higher temperature =more efficient Hypothesis • I think the hair dryer will be less energy efficient on the cold setting because it will take much longer to evaporate all the water. General Procedure • Measure energy used to dry 15mL of water in a Petri dish for 15 minutes on both the hot and cold setting as well as high and low fan speed • Weigh dish before and after to find amount evaporated Procedure: Set up Procedure: Set up Experimental Design • Experimental Variables: – Different temperature settings • Experimental Groups: – Hot Temp/High Fan settings, Hot/Low settings, Cold/High settings, Cold/Low settings • Control Group: – Petri dish of water allowed to dry for 15 minutes without the hair dryer Control Variables • • • • • Hair dryer at set length from water 15mL of water Same hair dryer 15 minutes of drying time Always inside (same location in the room) Humidity and Evaporation • More humidity=less evaporation • Important because if the room I tested in is too humid, the tests won’t accurately reflect the amount of water that could be evaporated in 15 minutes. Procedure: Analyze Data Trial Set 1 Amt. Dish w/ water Weight after evaporated kWh (g) drying (g) (g) used High/Hot 21.97 17.731 4.239 0.39 • Find the amount of evaporated water Comparing Data using Ratio Trial Set 1 Fan/Temp High/Hot Low/Hot High/Cool Low/Cool Amt. evaporated Energy use (g) kWh used (kWh/g) 4.239 3.163 2.978 2.509 0.39 0.20 0.06 0.03 0.092 0.063 0.020 0.012 Standardizing Data High/Hot Total Energy to Amt. evaporated Energy use Dry (g) kWh used (kWh/g) (kWh) 4.239 0.39 0.092 1.380 • Set up a proportion to find out how much energy is needed to completely dry the water – Ex: High/Hot: – 15g * 0.092kWh= 1.38 kWh for 15 g 1g • You wouldn’t just dry 15 minutes worth of water Trial Set 1 Total kWh needed- all trials High/Hot Low/Hot High/Cool Low/Cool High/Hot Low/Hot High/Cool Low/Cool High/Hot Low/Hot High/Cool Low/Cool Amt. evaporated kWh (g) used 4.239 0.39 3.163 0.2 2.978 0.06 2.509 0.03 Trial Set 2 4.249 2.942 2.942 2.089 0.39 0.2 0.06 0.03 Trial Set 3 4.302 0.39 3.12 0.2 2.8 0.06 2.129 0.03 Energy use (kwh/g) 0.092 0.063 0.020 0.012 Total kWh needed 1.380 0.948 0.302 0.179 0.092 0.068 0.020 0.014 1.377 1.020 0.306 0.215 0.091 0.064 0.021 0.014 1.360 0.962 0.321 0.211 Averages Adjusted to Evaporate all 15g of water Setting High/Hot Low/Hot High/Cool Low/Cool kWh 1.37 ± 0.01 0.98 ± 0.04 0.31 ± 0.01 0.20 ± 0.02 Average energy needed to evaporate 15g 1.600 1.400 k 1.200 W 1.000 h 0.800 n e 0.600 e 0.400 d e 0.200 d 0.000 High/Hot Low/Hot High/Cool Hair Dryer Settings Low/Cool Further Trials • Petri dish is not realistic • Tried hair. Hair Hair Trials Trial 1-Hair Mass w/ Mass after water (g) drying (g) High/Hot 164.29 89.08 Low/Hot 125.51 87.35 High/Cool 134.80 114.90 Low/Cool 141.22 132.35 Amt. Evap (g) kWh used 75.20 0.41 38.16 0.20 18.78 0.07 8.88 0.03 kWh/g 0.0055 0.0052 0.0037 0.0034 Total kWh needed 0.501 0.267 0.232 0.243 kWh/g 0.0081 0.0037 0.0011 0.0014 Total kWh needed 0.480 0.308 0.092 0.111 Trial 2-Hair Mass w/ water (g) High/Hot 139.90 Low/Hot 161.33 High/Cool 152.24 Low/Cool 146.12 Mass after drying (g) 89.29 104.69 98.78 125.10 Amt. Evap (g) kWh used 50.61 0.41 56.63 0.21 53.47 0.06 21.02 0.03 Averages Adjusted to Evaporate all water 0.600 0.500 k W h 0.400 0.300 n e e d e d 0.200 0.100 0.000 High/Hot Low/Hot High/Cool Hair Dryer Setting Low/Cool Conclusion • In a Petri dish, the low/cool settings are the most energy efficient. • On real hair, high/hot was least efficient, but the other three weren’t statistically different • I reject my hypothesis that cold would be the least efficient Improvements • Hair had a high standard deviation – Hard to standardize/weigh • Shorten distance – Not realistic Sources • http://atoc.colorado.edu/~englishj/Humidity.htm 1-31-11 • http://tlc.howstuffworks.com/style/hair-dryer.htm 1-2-11 • http://www.petervaldivia.com/technology/electrici ty/electrical-power.php 2-1-11 • http://www.sciencedaily.com/articles/e/evaporati on.htm 12-28-10 • http://www.ehow.com/how-does_4564927_blowdryer-work.html 1-2-11 • http://www.webchem.net/notes/how_far/kinetics/ maxwell_boltzmann.htm 12-28-10 Standard Deviation (Xav-Xi)2 N-1 • = Sum • Xav = Average • Xi = Trial •N = # of Trials Materials • • • • • • • • • Hair Dryer Ring stand Petri dish Graduated cylinder Pitcher Force meter Hair sample Physics books Kill-a-watt meter Data • Petri Dish • Hot air • High setting – 1: hair dryer wasn’t steady or lined up; water spilled – 2: hair dryer wasn’t lined up; water spilled • Decided to measure masking tape square to align dryer with dish – 3: With masking tape square; water did not spill; evaporated 1.7g, used .12kwh in 5 minutes Evaporative Cooling • As evaporation occurs, temp of liquid decreases – As faster-moving molecules escape, remaining molecules have lower kinetic energy • This is why sweat cools the human body • Explains why the water in my experiment was cooler, even after having hot air blown on it for 15 minutes. Hair Data Analysis Trial 1-Hair High/Hot Low/Hot High/Cool Low/Cool Amt. Evap (g) 75.20 38.16 18.78 8.88 kWh used 0.41 0.2 0.07 0.03 kWh/g 0.0055 0.0052 0.0037 0.0034 Total kWh needed 0.501 0.267 0.232 0.243 kWh/g 0.0081 0.0037 0.0011 0.0014 Total kWh needed 0.480 0.308 0.092 0.111 Trial 2-Hair Amt. Evap (g) High/Hot 50.61 Low/Hot 56.63 High/Cool 53.47 Low/Cool 21.02 kWh used 0.41 0.21 0.06 0.03 Averages Adjusted to evaporate all water Setting High/Hot Low/Hot High/Cool Low/Cool kWh 0.490 ± 0.014 0.287 ± 0.029 0.162 ± 0.099 0.177 ± 0.093