Marcet`s Boiler

Experiment : Marcet`s Boiler


Aim                     : To show the relation between the pressure and temperature of  
                                    satuated   steam             
                             
Theory            : At a given pressure, the  temperature at which a pure substance      
                                  changes its phase is called saturation temperature . Analogusly at 
                                  pure substance change its phase is called the saturation                      
                                  pressure.

                                          This experiment explores the relationship between the 

                                   saturation  temperature and its corresponding pressure

                                   for water.

                                         When the water in the boiler is heated up it starts to evaporate a

                                  more  water changes it`s phase from liquid to vapour.More vapour 

                                  accumulates inside the boiler vessel and increase the pressure 

                                 imposed on the water surface.The pressure build up tends to  

                                 increase the resistance faced by liquid up molecules as they change 

                                 in to vapour.

                                        Consequently increasing the saturation pressure of the remaining 

                                liquid .Absolute pressure of steam is the sun of the gauge pressure   

                                and the atmospheric pressure average value of saturated temperature 

                                for each gauge pressure is the mean value of saturated temperature 

                               measured during heating and cooling.

Procedure  :Heat the boiler half filed  with water by means of a bunsen until the         gauge pressure is about 15 lbs/in.(1.035 bar ) and lift the safety valve to allow  the air above the water to be driven out and replaced by steam.Then allow the boiler to cool and the pressure to drop to atmospheric pressure.This ensures as far as possible the whole apparatus being at the same temperature  before readings are taken.Now heat the boiler and tabulate values of gauge pressure and temperature up to 7 bar (at intervals of 0.5 bar).Then Remove the burner and as the apparatus aools read the temperatures below atmospheric,poen the steam cock and read the vacuum gauge.


Calculation      :


Atmospheric Pressure     = 75.95 Hg cm
                                                  = 75.95 x 10² x 13600 x 9.81
                                                                 10


Specimen calculation for absolute pressure 
 when
                    gauge pressure          = 1.0 bar
                 Absolute pressure        =  Gauge pressure + Atmospheric pressure
                                                            = 1.0 + 1.0315
                                                            = 2.0315 bar  
For Average temperature when gauge pressure is 1 bar


                      T Avg                           = T heating + T cooling
                                                                             10
                                                            = 101 + 125
                                                                     2
                                                            = 113 ^oC


                         Error                         = saturated  temperature - Average temperature  
                                                            = 120.3  ^oC - 113  ^oC                      
                                                            = 7.3 ^oC


Discussion :           


          Pressure and temperature are the two fundamental quantities of any material standard temperature and pressure is a standard set of conditions for experimental measurements to enable comparisons to be made between sets of data
         In the experiment the pressure and temperature are compared by the graphs and tabulated results as for the pressure and temperature are compared and it was almost constant through out the experiment.The result showed that by comparing each test , error made during the experiment can be analyzed and support the discussion effectly.


* Error Analysis
            The error precentage should be around 10 - 20 % because there`s small difference between the actual and ideal value`s we got.
     Source of experiment error

• Measurement reading accuracy
• Room temperature and pressure
• The stability of the materials

Resolution to Experimental errors

• Avoid measurements readings errors.