Calculations of the pulse combustion drying system I. Zbici  nski * , C. Strumillo, M. Kwapinska, I. Smucerowicz Faculty of Process and Environmental Engineering, Technical University of Lodz, ul. W olczanska 213/215, 90-924 Lodz, Poland Abstract The paper describes modelling of spray drying system where valved and valveless pulse combustors were appliedasasourceofdryingagent.Experimentalanalysisofpulsecombustorsoperationwascarriedoutin order to optimize their performance to achieve low emission of toxic substances, stable operation and high and smooth pressure oscillations. Optimized valved and valveless units were applied in the drying system. Extensive drying and evaporation tests were carried out to establish basic data required for modelling of thesystem.Lasertechniqueswereappliedtodetermine¯ow®eldinthedryingchamberLDA)aswellasto analyse the structure of disperse phase PDA). A modi®ed mathematical model of heat, mass and momentum transfer in spray drying, developed earlier,wasusedtodescribethepulsecombustiondryingsystem.Themodelenablestoobtaintemperatures ofcontinuousanddispersephases,percentofevaporationandpositionsofparticularfractionsinthedryer. Airvelocitypro®lesintheaxialandradialdirectionsinthedryingchamberdeterminedexperimentallywere substituted to the main programme calculating the spray drying process. A comparison of theoretical and experimental results shows good agreement also for complex hydro- dynamics of pulsating ¯ow in the drying chamber. Experimental investigations and mathematical modelling proved that the pulse combustion spray drying system could be eectively applied in dewatering of solutions with low content of solids, which could be important for waste disposal. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: Valveless, valved pulse combustor; Spray drying; Entrainment rate 1. Introduction Drying process is one of the most harmful to environment and energy demanding unit oper- ations in chemical engineering. Therefore, for many years, studies concerning modi®cations of the Energy Conversion and Management 42 2001) 1909±1918 www.elsevier.com/locate/enconman * Corresponding author. Fax: +48-42-6364923. E-mail address: zbicinsk@ck-sg.p.lodz.pl I. Zbici  nski). 0196-8904/01/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII:S0196-890401)00050-4