Cel IN LARGE FLUIDIZED BEDS, NATURAL CIRCULATION OCCURS WITH AN UPWARD MOVEMENT IN THE MIDDLE OF THE BED AND DOWNWARD MOTION AT THE SIDES. IN SMALLER BEDS SUCH A CIRCULATION CAN BE INDUCED BY A HEAT EXCHANGER WITH HORIZONTAL TUBES IN THE CENTRE OF THE BED. IN THIS STUDY, THE EFFECT OF THE SHAPE OF THE HEAT EXCHANGER ON THE CIRCULATION IS INVESTIGATED. BECAUSE OF THE CIRCULATION, THE TUBES CAN BE VERY CLOSE. THE HEAT EXCHANGER IS THUS VERY COMPACT AND ONLY A SMALL PART OF THE BED IS NEEDED FOR HEAT EXCHANGE. HEAT TRANSFER AND COMBUSTION IN THE BED ARE THUS SEPARATED. BY VARYING THE CIRCULATION FLOW THE HEAT OUTPUT CAN ALSO BE REGULATED. ONE OF THE AIMS OF THIS PROJECT IS TO STUDY THE GEOMETRY OF THE GRATE, WHERE THE FLUIDIZATION OCCURS, SO THAT THE CIRCULATION EFFECT CAN BE KEPT UNDER CLOSE CONTROL. THE RATE OF CIRCULATION IS VARIED TO SUIT THE RELEVANT APPLICATION AND OPERATING CONSTRAINTS, REGARDLESS OF THE HEAT EXCHANGER GEOMETRY. CIRCULATION OF THE SOLIDS THROUGH THE EXCHANGER SHOULD GIVE A BETTER COEFFICIENT OF HEAT TRANSFER BETWEEN THE FLUIDIZED BED AND THE TUBES. THIS IS A RESULT OF THE FASTER CIRCULATION OF PARTICLES IN CONTACT WITH THE TUBES AND OF THE ELIMINATION OF THE LAYER OF MOTIONLESS PARTICLES WHICH OTHERWISE FORM ON THE UPPER SURFACE OF THE HORIZONTAL TUBE BUNDLES. THE TEST RIG HAS CLEARLY DEMONSTRATED THAT THE SELF-MAINTAINING CIRCULATION STARTS WHEN A COMPACT HEAT EXCHANGER IS INSERTED ONLY IN THE CENTRE OF THE FLUIDIZED BED. UPWARD PARTICLE VELOCITIES OF 1 TO 30 MM/S HAVE BEEN OBTAINED. A SERIES OF EXPERIMENTS WERE CARRIED OUT TO DETERMINE THE EFFECT OF DIFFERENT VARIABLES ON THE OPERATION. IT WAS ESTABLISHED THAT THE STRENGTH OF CIRCULATION VARIED LINEARLY AS A FUNCTION OF THE MEAN GAS VELOCITY WHILE THE DISTRIBUTION OF THE FLUIDIZING GAS WAS NOT IMPORTANT. VERY GOOD OUTSIDE HEAT TRANSFER COEFFICIENTS (BETWEEN BED AND TUBEWALLS) OF 300 AND 400 W/M2/DEGREE C HAVE BEEN MEASURED (FOR PARTICLES OF 847 AND 470 MICRONS. THIS CONFIRMED THE BENEFICIAL INFLUENCE OF PARTICLE CIRCULATION ON HEAT TRANSFER. HEAT TRANSFER AND COMBUSTION IN THE BED ARE MORE OR LESS SEPARATED AND BY VARYING THE CIRCULATION FLOW THE HEAT OUTPUT CAN BE REGULATED. Program(-y) PRE-ENNONUC 2C - Energy research and development programme (EEC), 1979-1983 Temat(-y) Data not available Zaproszenie do składania wniosków Data not available System finansowania Data not available Koordynator Creusot Loire Industrie SA Wkład UE Brak danych Adres 71208 Le Creusot Francja Zobacz na mapie Koszt całkowity Brak danych Uczestnicy (1) Sortuj alfabetycznie Sortuj według wkładu UE Rozwiń wszystko Zwiń wszystko Université de Technologie de Compiègne Francja Wkład UE Brak danych Adres 60206 Compiègne Zobacz na mapie Koszt całkowity Brak danych
