Modelling and experimental study of urban waste water sludge solar drying in a greenhouse
H. Amadou1*, C. Beck2, R. Mose2, J.-B. Poulet3, A.-G. Sadowski2
1 Université Abdou Moumouni de Niamey, Faculté des sciences et Techniques Bp 10662 Niamey–Niger
2Laboratoire de Systèmes Hydrauliques Urbains ENGEES.1, quai Koch 67070 Strasbourg , France
3 Laboratoire en Génie de conception INSA.24,Boulevard de
* Corresponding author. E-mail: firstname.lastname@example.org
Received: 05October 2011; revised version accepted: 29 November 2011
Solar drying of sludge is a new process whose design techniques remain very empirical, and too rudimentary to reflect the complexity of the physical phenomena involved. In the current study, a mathematical model of simultaneous heat and moisture transfer in a greenhouse is proposed for prediction of air drying temperature, sludge and glass cover temperatures. It also allowed describing the moisture loss from the sludge at wide ranges of relative humidities, air drying temperatures, air velocities and solar radiation values. The model took into account the effect of moisture-solid interaction at the drying surface by means of sorption isotherms of sludge. Physical constants and thermal properties were also incorporated in the model. The classical fourth-order Runge-Kutta method was used in the solution of simultaneous heat and moisture transfer equations at different times during drying. The validation of the model is submitted to an experimental approach in the laboratory. When the experimental results were compared with those obtained from simulated, good agreement was found.
Keywords: Urban residuary sludge; Drying kinetics; Numerical simulation; Heat and mass transfer; Solar drying.