Thermal and dynamical characterization of the plume above a cylindrical heat source

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1 Thermal and dynamical characterization of the plume above a cylindrical heat source J.R. Fontaine, J. Blaise, INRS, France P. Hynynen, FIOH, Finland R. Devienne, LEMTA, France

2 Introduction Numerous industrial processes employ heat sources; By natural convection these sources create plumes likely to convey various pollutants; This could lead to occupational risks Plume flow analysis is necessary for the design of appropriate ventilation system.

3 Industrial processes with thermal and pollutant sources - examples Electrostatic powdering on preheated parts Bending of barrels

4 Industrial processes with thermal and pollutant sources - examples Lead foundry Extrusion and blowing

5 Industrial processes with thermal and pollutant sources - examples Crepe paper manufacturing

6 Objective of the work developed at INRS To deliver a method to characterize plume flows generated by industrial heat source Geometry and convected heat power of the source Air flowrate convected by the plume, temperature and velocity distribution (radii)

7 Objective of the work developed at INRS Experimental characterisation of plume flows generated by simple generic source (disks, cylinders, rectangles ) Numerical approach applicable to real complex cases and validated for generic sources The goal of this paper is to present the experimental analysis of plumes generated by cylindrical heat source

8 Vertical ventilation test room 4, m 8 7 5,6 m 7,4 m ,8 m 1) Experimental chamber ) Perforated floor 3) 4 fabric blowing ducts 4) 4 blowing conduits (air supply) 3 4 5) Heat source 6) Air treatment and blowing unit 7) Perforated ceiling 8) 3 fabric extraction ducts Test room 4.8 x 4. x 5.6 m3 Vertical ventilation Q : 000 to m3/h Blowing air temperature T : 18 to 5 C

9 Modular cylindrical heat source Copper disc D = 1000 mm thickness 8 mm nickel plated Zone Zone 1 Copper cylinders D = 1000 mm thickness 8 mm height 50 mm nickel plated Zone 3 Zone 4 Thermal insulation thickness 10 mm Zone 5 Thermal insulation thickness 50 mm Surface temperature of each zone independently fixed 5 zones of identical area (0.78 m) Maximal heat power 0 kw

10 Measurement system 3D displacement system 1,4 m 0,6 m 0, m 0,1 m VIVO units for measuring air velocity and temperature z y 3D displacement system 35 cm x Cylindrical source 140 cm 140 cm Hot film Thermocouples type K x z y 35 cm Cylindrical source Thermistor

11 Test cases 350 C 110 C 59 C 50 C 50 C 65 C 60 C 100 C 65 C 35 C 35 C 65 C C C 51 C Case 1 Case Case 3 Blowing temperature 0 C Air flowrate 5000 m3/h Heat power of the source 5700 W

12 Plume in a non stratified medium T ( r, z) T = ( T ( z) T ) a c a exp b T r () z w ( r, z) = w c exp () z r b T c T a z: height b T (z), b(z) : thermal, dynamical radius of the plume T c, w c temperature, velocity at the centre of the plume T a : temperature of the ambient medium

13 Dynamic and thermal radii of the plume case 1 0,6 b, b T (m) case 0,6 b, b T (m) 0,5 0,5 slope = 0,11 0,4 slope = 0,107 0,4 0,3 0,3 slope = 0,095 0, slope = 0,090 b (case 1) 0, b (case ) z v =-1 m 0,1 bt (case 1) z v =-1,5 m 0,1 bt (case ) z (m) z (m) b 6 = α( z 5 z v ) b α λ z v (m) λ = T Case Case b

14 Plume flow rate Q 1 3 ( z) = 0.005Pc ( z zv ) 5 3 Q (m 3 /h) Q (computed from wc ; case 1) Q (computed from wc ; case ) P c 1/3 (z-z v ) 5/3 (m) Q = πb ( ) 3 w c Q = Pc z zv

15 Elliptical plume (case 3) 50 C 50 C 65 C 60 C 100 C 65 C 35 C 65 C C 51 C Case Case 3 T ( ) ( ( ) ) f ( x, y) x, y, z T = T z T e a c a f cos a θ sin b θ + sin a θ + = ( x, y) ( x x ) + ( y y ) + ( x x )( y y ) sin θ + θ cos b 1 a 1 b

16 Temperature distributions (case and 3) Elliptical model : case Elliptical model : case 3

17 Conclusions Plume flows generated by a cylindrical heat source were experimentaly described; The convected heat power was kept constant but the source surface temperature distribution was varied; When the top surface of the cylinder was heated (cases 1 and ) the corresponding plume flow was equivalent to the flow generated by a point source located at a virtual origin.

18 Conclusions () For case 3 the plume lost the symmetry of the source Centre of the plume does not coincide with the axis of the cylinder The temperature distribution in horizontal planes is elliptic It is nevertheless possible to fully characterise the plume. Work is in development to predict the dependence of the plume on the geometry of the source. Cylindrical sources Rectangular sources with aspect ratios varying from 1 to 6

Effect of Jet Disturbance on Convective Flow from a Heat Source

Effect of Jet Disturbance on Convective Flow from a Heat Source Esa Sandberg Principal Lecturer Satakunta Polytechnic, Finland (since 1.1.2006 Satakunta University of Applied Sciences) Tel. +358 44 710