5. Lab report

Write the lab report according to the guidance given to you (see Canvas, 2200 words count) while incorporating or answering the following information or questions:

• Draw a flow diagram of the process, labelling all inputs, outputs and process conditions

• Perform energy and mass balances and calculate the total drying time, t. if the density of particle, ρp= 1500 kg/m3.. The feed droplets generated by the nozzle have an estimated range in diameters from 40 to 95 µm and their critical moisture content is 40 % wet basis.

• Calculate the overall efficiency

• Calculate Reynold number for the feed and drying air. The viscosity of the milk is 2.127 cp. The Reynold number is calculated using the air velocity based on Figure 3.The inlet pipe diameter for air is 0.4 cm and that for the feed is 0.2 cm.

NB. The drying air is sucked through the drying chamber by the aspirator motor. Therefore the amount of heated drying air can be increased or decreased by regulating the aspirator speed.

• Estimate the heat transfer from a gas to a single particle of initial diameter 100 µm. Latent heat of vaporisation is 2360KJ/kg.

• Estimate the rate of mass transfer from the particle initial diameter 100 µm to a gas

• Assuming the ration height to diameter of the drying chamber is 2:1, estimate the dimensions of the drying chamber.

• Estimate a droplet free fall velocity assuming milk droplet falls in the dry air at 95 ˚C under Stokes conditions

• What differences did you observe (if any) in the solubility of the powder and yield when varying the inlet temperature. Use table 1 while presenting your results

• Discuss different ways of controlling the outlet temperature

• Discuss and interpret the results in comparison to the theory and the quality of other commercial dried powder products such instant coffee.