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THE AEROSOL CHAMBER FACILITY AIDA

Introduction

The AIDA aerosol chamber facility was designed and constructed to investigate physical and chemical, especially heterogeneous, processes involving atmospheric aerosols. A unique feature is the large range of accessible temperatures from 183 K to 333 K. In addition, the chamber can be evacuated for cleaning and pre-conditioning purposes and can be operated at reduced pressures. Thus, aerosol experiments can be carried out in the full range of tropospheric and stratospheric temperatures and pressures.

Figure 1
Figure 1: The AIDA experimental facility

The main parts of the facility (Figure 1) include the reaction vessel, the thermostated housing, the vacuum pump and gas supply system, and the instrumentation for aerosol characterization and trace gas analysis.

Reaction vessel and thermostat

Some technical data concerning the reaction vessel and the thermostated housing are listed in Table 1. The temperature is controlled by circulating air around the reaction vessel. The air is ventilated through two heat exchangers with flow rates up to 30000 m3/h. Down to 233 K, cooling is achieved with a conventional cooling machine, the cooling medium (R404A) being directly evaporated inside the heat exchangers.

Reaction vessel.Thermostated housing.
Material: AlMg3 Volume: 360 m3
Surface area: 103 m2Temperature range: 183 K - 333 K
Volume: 84.3 m3Temperature stability: ±0.5 K
Surface to volume ratio: 1.22 m-1Cooling rate: up to 6 K/h
Pressure range: 0.01 to 1000 hPaHeating rate: up to 6 K/h
Flange diameters: 10 to 1100 mm..

Table 1: Technical data of the AIDA experimental facility

The cooling power is about 58 kW at 233 K. The electrical heating power is 33 kW. Below 233K , cooling is achieved by direct evaporation of liquid nitrogen inside the heat exchangers. During the down-cooling phase, liquid nitrogen consumption is about 600 l/h at a cooling rate of 6 K/h. For keeping the facility at a constant temperature below 233 K, about 200 l/h liquid nitrogen is required.

The first low temperature test was successfully performed in the end of September 1996 (Figure 2). As expected, cooling rates of up to 6 K/h were achieved in the whole temperature range. A step-like temperature profile was chosen to check for temporal and spatial temperature control. The temperature stability turned out to be better than ±0.5 K.

Figure 2
Figure 2: Result of the first low temperature run of the AIDA aerosol chamber. The plotted temperatures are measured inside the chamber at three different locations.

Vacuum and gas supply system

A 2600 m3/h, oil-free roots blower pump (Edwards EH2600) evacuates the vessel within 2 to 3 hours to the final pressure (about 0.01 hPa). The tube connection between the vessel and the pump is about 5 m long and 0.2 m wide. After evacuation, the vessel can be filled with synthetic air. An adsorption drier is used to lower the dew point to about 203 K. The vessel can also be cleaned and conditioned at high ozone concentrations.

Trace gas and aerosol instrumentation

The AIDA instrumentation for trace gas analysis and physical and chemical aerosol characterization is listed in tables 2 and 3.Various techniques are used for aerosol generation. Salt aerosol particles with diameters between approximatly 10 nm and 5 µm are generated by dispersing salt solutions using nebulizers, fine nozzles, or ultrasonic devices. A carbon sparc generator and acetylene burners are used to generate soot aggregates with primary particle diameters between 5 nm and 50 nm and mass equivalent diameters between 0.05 µm and 0.5 µm. A separate 3.7 m3 pre-chamber can be used to prepare aerosols for introduction into the AIDA reaction vessel.

 
Type of Instrument Measurement Sampling Method / Medium Status
Long path FT-IR system (Bruker IFS66v, resolution 0.1 cm-1 ) Extinction (800 -6000 cm-1),
Trace gases and aerosols
 In situ, White type multi-reflection cell (254 m path length) Operating
Long path FT-VIS system (Bruker IFS66/s, resolution 0.1 cm -1 Extinction (800-40000cm-1),
e.g. HONO, NO3, etc.		 In situ, White type multi-reflection cell (112 m path length) Operating
Tunable diode laser system (DFB)
 Water absorption at 1370 nm
 In situ, White type multi-reflection cell (112 m path length) Operating
Ion trap MS with EI and CI (Bruker, Esquire-LC) Acids, halogen and sulfur compounds, ... Direct sampling/flow tube system with CI Operating
Gas chromatographs (ECD, FID) Stable trace gases On-line sampling or via adsorption trap Stand by
NOx monitors (chemi-luminescence method) NO/NOx Direct sampling via teflon tube Operating
Ozone analysers (UV absorption method) O3 Direct sampling via teflon tube Operating
Dew/Frost point mirrors
 Dew/Frost point
 Heated stainless steel tube
 Operating

Table 2: AIDA analytical instrumentation for trace gas concentration measurements.

 
Type of Instrument Measurement Sampling Method / Medium Status
Aerosol concentration . . .
Condensation nuclei counters (TSI 3010, 3022A, 3025A) Number concentration Stainless steel tube, 3 mm diam., 0.3 l/min Operating
Micro balance Mass concentration Teflon membrane filter Operating
Aerosol size distribution . . .
SMPS mobility analysers (TSI 3071) Number size distribution (10 nm to 900 nm) Stainless steel tube, 3 mm diam., 0.3 l/min Operating
APS (TSI)
 Number size distribution
 Stainless steel tube
 Operating
Fine particle mobility analyser (Hauke EMS VIE-07 FC 3/150) Number size distribution (3 nm to 150 nm) Stainless steel tube, 3 mm diam. Stand by
Optical particle spectrometer (Palas PCS 2000) Number size distribution (0.6 µm to 40 µm) Stainless steel tube, 8 mm diam., 10 l/min Operating
Optical particle spectrometer (Palas WELAS)
 Number size distribution
 Stainless steel tube
 Operating
Laser particle spectrometer LAS-X (PMT) Number size distribution (0.1 µm to 7 µm) Stainless steel tube, 5 mm diam. Operating
9-stage Berner cascade impactor Mass distribution (0.06 µm to 16 µm) Stainless steel tube, 8 mm diam., 10 l/min Operating
11-stage rotating disk Berner cascade impactor Mass distribution (0.02 µm to 16 µm) Stainless steel tube, 14 mm diam., 25 l/min Operating
Aerosol shape and composition . . .
Coulomat
 Total carbon mass
 Quarz fibre filter
 Stand by
Thermograph (RA10m)
 Carbon mass (EC/OC)
 Quarz fibre filter
 Operating
Ion chromatograph (Dionex DX-500) Bulk and size segregated chemical composition Teflon membrane filter and impactor samples Operating
SEM, TEM Particle shape and size Nuclepore filter samples In cooperation
SIMS Chemical particle analysis Inertial sampling on indium foils In cooperation
Photoelecton emision sensor (PAS 2000, EcoChem)
 Suface sensitive photoelectron emission
induced at 222 nm
 Stainless steel tube
 Operating
Diffusion charger (LQ-q, Matter Engineering AG)
 Active (Fuchs) surface area
 Stainless steel tube
 Operating
Optical aerosol properties . . .
Laser
 Extinction (635 nm) In situ, 4 m path length Operating
Extinction cell Extinction (450 nm) Ex situ, 75 m path length Operating
UV/VIS/NIR spectrometer
 Extinction (300-1700 nm)
 In situ, Multipath cell
 Operating
UV/VIS spectrometer Extinction (250-1000 nm) In situ, 5 m path length Operating
Nephelometer (TSI) Scattering (450, 550, and 700 nm) Stainless steel tube
 Operating
Argon-Ion laser (488 nm)
 Scattering & depolarisation In situ Operating

Table 3: AIDA instrumentation for physical and chemical aerosol analysis.


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This page is part of the AIDA information service on research related to aerosols and heterogenous atmospheric chemistry. Comments and suggestions are welcome.
Revised: August 09. 2004 Copyright © 1996 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft
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