The Efficiency of Hand Dryers

1. The Efficiency of Hand Dryers Chris Mullen EtayOrlander

2. Introduction • Hand dryers much more environmentally friendly than paper towels • People get frustrated with length of time to dry hands • Compared the effectiveness of different models • Older warm-air dryers • Newer energy efficient models

3. Tested Models

4. Theory • Dryers modeled as compressors • Steady state, with control volume, standard assumptions (pressure at one bar, no stray heat transfer) • Air as an ideal gas • Ideal gas law • Set amount of energy to evaporate a set amount of water • Assumed 5 mL initially on hands

5. Theory-Equations • Ẇ = ṁ(hin-hexit) • ṁ = • v = • η = • Q1 = mc∆T, Q2 = m*L, Total energy = Q1 + Q2 = 12.83 kJ • m = 5 g, c = 4.179 kJ/kg *K, L = 2.26 * kJ/kg • Time to dry =

6. Methods • Measured dimensions of output nozzle • Measured ambient temperature • Measured output velocity, temperature • Mass flow rate calculated from area and velocity • Power out calculated from mass flow rate and h values from tables • Gathered Manufacture information from Internet

7. Equipment Used

8. Results Xlerator XL-SB Toto Clean-Dry World Dryer NR-126 World Dryer RA-5

9. Results

10. Conclusions • All models had comparable output power • Variable efficiency • Newer models generally more efficient/effective • Positive correlation between area of nozzle and effectiveness • Main dryer disadvantage is they are less hygienic than paper towels

11. Questions? • And…..Family Guy!