ScienceAsia 29 (2003): 067-075 |doi: 10.2306/scienceasia1513-1874.2003.29.067

Development of Mathematical Model for Continuous Spray Evaporator/Air (de)humidifier with Nonisothermal Polydisperse Droplets

Pratarn Wongsarivej and Wiwut Tanthapanichakoon^*

ABSTRACT: A steady state model of co-current spray evaporator and air (de)humidifier for non-isothermal droplets has been developed to investigate the effect of polydispersity of droplet size on performance. The model is validated by comparison with results of Dickinson and Marshall (1968, AICHE J.14,541). It reveals that their ideal assumption of constant droplet temperature leads to significant error when the droplet size distribution is strongly polydisperse. Numerous simulation cases of the spray evaporator show that the average droplet diameter and droplet size distribution of water spray significantly affect the change in the air properties and the size, velocity and temperature of water droplets. For polydisperse droplets, a narrower droplet size distribution ( =0.2) shows a more rapid decrease in the diameter of the droplets, thus causing a more rapid temperature decrease and humidity increase of the air than the case of a broader droplet size distribution ( =0.4) with the same volume-averaged diameter.

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Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand.

* Corresponding author, Email: fchwtt@eng.chula.ac.th

Received 30 Apr 2001, Accepted 13 Aug 2002