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THERMODYNAMICS - CASE STUDY

    Introduction




Phase Change Experiment

 

A student is working on his thermodynamics experiment about phase change. He boils room temperature water using a pan placed on the top of a electric heater at room pressure. A thermometer is used to measure the temperature of the substance in the pan.

Known:

  • The mass of the water in the pan is m = 1.0 kg
  • The power (energy per unit time) of the electric heater is = 2.0 KW
  • The temperature of the room is Troom = 20 oC and the pressure is P = 1 atm
  • The specific heat of water is c = 4.184 kJ/(kg-K)
  • The latent heat of vaporization of water is L = 2257.0 kJ/kg
     
    Questions



Phase Change Process on T-v Diagram
Click to View Movie (4 kB)

 

The student needs to record the temperature over a period of time. The records should include all phases such as subcooled liquid, saturated liquid, saturated mixture, saturated vapor, and superheated vapor. Please determine the time intervals between each two records.

   
  Approach

 
  • Take the water in the pan as a system
  • The process is shown on the T-v diagram