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Preliminary Investigations of Energy Balances

Preliminary Investigations of Energy Balances. ENCH 4350 9/7/2010 Hemali Dholakia Jessica Lacy. Procedure Data Heating with Coffee Pot Heating with Microwave Ovens Heating with Hot Plate ∆H and Student’s T Test Results Challenges. Objectives. Procedure:

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Preliminary Investigations of Energy Balances

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  1. Preliminary Investigations of Energy Balances ENCH 4350 9/7/2010 Hemali Dholakia Jessica Lacy

  2. Procedure • Data • Heating with Coffee Pot • Heating with Microwave Ovens • Heating with Hot Plate • ∆H and Student’s T Test • Results • Challenges Objectives

  3. Procedure: • Observe energy and material balances • Determine average change in enthalpy (∆H) using calculations and experimental data • Determine the measure of uncertainty of experimental data using the Student’s T Test

  4. Thermometer Calibration 97.8oC -1.0oC

  5. Material and Energy Balance H = Cp*m*∆T, where CpH2O= 1 cal/oC*g Hot Water: H= 100 g x 63oC = 6300 J Cold Water: H = 100.4 g x 1.9oC = 190.76 J Determine ∆T: ∆T = H/total mass ∆T = 32.4oC

  6. Hot and Cold Water Mixed

  7. Heating with Coffee Pot

  8. Heating with Microwave Ovens (EMCS 441)

  9. Heating with Microwave Ovens (EMCS 427)

  10. Heating with Hot plate

  11. Microwave (427) Watts Time (30 second intervals)

  12. Time (30 second intervals)

  13. Energy Comparison Using Experimental Data

  14. Energy Comparison Using Calculated Data

  15. Uncertainty of Experimental DataDetermined by Student’s T Test

  16. Calculated and experimental data did not match • Experimental data factored in time (H = watts*time) • Calculated data determined energy usage per ΔTemp (H = Cp*m*∆T) • Large time interval to reach >90oC causing large electrical energy consumption • All three appliances consumed more energy (J) than expected by H equation Results

  17. Time interval used based on how long temperature reached >90oC for microwave and hot plate • Coffee Pot data dependent on time for water to cycle through system Challenges

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