Laserfiche WebLink
<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />III. THE CLOUD CHAMBER FACILITY <br /> <br />3.1 Dynamic Cloud Chamber <br />The dynamic cloud chamber has been described by DeMott (1988) and <br />DeMott and Rogers (1990). It is shown in the schematics in Figure 3.1. <br /> <br />It consists of a 2.0 m3 stainless steel outer pressure vessel which <br /> <br />houses a thin (low thermal mass) cylindrical inner copper liner open to <br /> <br />the pressure vessel by small holes in the top and bottom plates. Total <br /> <br />experimental working volume is l.19 m3. In operation, air is evacuated <br /> <br />at a controlled rate from the pressure vessel (using a vacuum pump and <br /> <br />a stepping-motor-driven control valve connected to the pressure vessel) <br /> <br />to produce expansion cooling of the sample air. The space between the <br /> <br />pressure vessel and the inner vessel acts as an expansion plenum which <br /> <br />helps to dampen changes in flow rate out of the inner vessel as the <br /> <br />pressure control valve cycles. The evacuation rate is controlled by <br /> <br />computer, based on specified initial conditions of temperature, <br /> <br />pressure, humidity and ascent rate. The simulated ascents are based on <br /> <br />equations for dry adiabatic ascent to cloud point and moist adiabatic <br /> <br />ascent thereafter. The program allows for a high degree of flexibility <br /> <br /> <br />regarding initial chamber conditions and accounts for latent heat <br /> <br /> <br />release at the lifting condensation level. Computed air parcel <br /> <br />coefficients are output to an ascent profile memory system that is <br /> <br />triggered when the desired initial conditions have been physically <br />