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 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

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

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 Find the amount of evaporated water

Comparing Data using Ratio

Standardizing Data 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 1 g You wouldn’t just dry 15 minutes worth of water

Total kWh needed- all trials

Averages Adjusted to Evaporate all 15g of water

Average energy needed to evaporate 15g

Further Trials Petri dish is not realistic Tried hair.

Hair

Hair Trials

Averages Adjusted to Evaporate all water

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 http://tlc.howstuffworks.com/style/hair-dryer.htm ty/electrical-power.php http:// ty/electrical-power.php on.htm http:// on.htm dryer-work.html http:// dryer-work.html maxwell_boltzmann.htm http:// maxwell_boltzmann.htm

Standard Deviation  (X av -X i ) 2 N-1  = Sum X av = Average X i = 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

Averages Adjusted to evaporate all water