GB1569729A

GB1569729A - Vapourisation bubbler

Info

Publication number: GB1569729A
Application number: GB2407778A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1980-06-18

Description

(54) VAPORISA1AON BUBBLER (71) We, STANDARD TELEPHONES AND CABLES LIMITED, a British Company, of 190 Strand, London WC2R lDU, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to vaporisation bubbler apparatus.

In a vaporisation bubbler of the normal type carrier gas is introduced via a dip tube immersed in the liquid to be vaporised.

Bubbles rise to the surface entraining vapour in the process, and the gas/vapour mixture then escapes. The bubble path length is wholly dependent on the distance between the dip tube orifice and the liquid surface. As vapour is lost, so the liquid level falls and the bubble path length is reduced. This will cause a progressive reduction in the saturation level of the gas as the bubbler contents are expended.

According to the invention there is provided a vaporisation bubbler apparatus comprising a vertical bubble tube, means for introducing a stream of carrier gas into the lower end of the bubble tube, means for filling the bubble tube from its lower end with a liquid to be vaporised, the internal diameter of the bubble tube being substantially comparable with the size of the bubbles which, when the apparatus is in use, rise up the filled tube, a liquid reservoir connected to the filling means, overflow means whereby, in use, liquid carried to the top of the bubble tube is returned to the reservoir, and means for discharging from the upper part of the apparatus the vapour bearing gas.

Embodiments of the invention will be described with reference to the accompanying drawings, in which: - Fig. 1 shows an embodiment of the invention, and Fig. 2 shows a modification to the bubbler tube of Fig. 1.

Fig. 1 shows a schematic representation of the constant level bubbler. Gas emerging through the gas inlet orifice 1 enters the bottom bulb 2, which is filled with liquid 3 supplied by gravity from the reservoir 4 via the liquid supply tube 5. The gas bubbles 6 so generated rise, passing into the lower end of a vertical tube 7 of predetermined bore-the bubble tube. As its bore is made of a size comparable with that of the bubbles, the rising stream carries liquid trapped between adjacent bubbles up the tube. The bubble tube 7 is of a length sufficient to ensure that when the gas emerges at the top it is completely saturated with vapour. The liquid and gas mixture vent into the top bulb 8, this being above the surface level of the liquid 3 in the reservoir. Here the gas may be allowed to escape and the liquid flows by gravity back into the reservoir through the return tube 9. However it is preferable that both gas and liquid are passed into the reservoir before separation. This helps prevent liquid droplets from being carried over with the gas stream, which may be further guarded against by a suitable baffle 10 in the reservoir inserted between the return tube orifice and the gas outlet tube 11. The presence of a relatively large gas volume between the bubble tube and the gas outlet also acts as a buffer to pressure pulses in the bubble tube, caused by the quantum nature of bubbles, and to any short term fluctuations in bubble delivery rate. The liquid, having been returned to the reservoir, is then available for recirculation via the liquid supply tube.

The rheological conductance of the bubble tube should be chosen so that at low gas flow rates liquid is still being forced to the top, whilst not exerting an excessive back pressure at higher flow rates. It has already been mentioned that the bubble tube should be sufficiently long to ensure total saturation; to increase bubble path length further the tube may also be helical.

Performance of the bubbler is improved, especially at high flow rates, by introducing a repetitive variation in the bubble tube bore diameter. As the bubble rate in a smooth bore tube is increased, the bubbles tend to become larger, and as they are prevented from enlarging in the horizontal plane by the tube bore, they must elongate. Thus at higher flow rate in a tube of a given length there will be fewer bubbles. As flow rate increases further the bubbles will continue to elongate until there is just one continuous column of gas blowing through the tube. So the surface area of liquid in contact with the gas is progressively decreased, possibly resulting in reduced saturation levels. By introducing a regular modulation of the tube bore (Fig.

2), at high bubble rates fluid is retained in the bulges 30 up the entire length of the tube, and not as before being largely blown out of the top. Turbulence generated within each bulge also assists in obtaining maximum saturation of the gas.

WHAT WE CLAIM IS: - 1. A vaporisation bubbler apparatus comprising a vertical bubble tube, means for introducing a stream of carrier gas into the lower end of the bubble tube, means for filling the bubble tube from its lower end with a liquid to be vaporised, the internal diameter of the bubble tube being substantially comparable with the size of the bubbles which, when the apparatus is in use, rise up the filled tube, a liquid reservoir connected to the filling means, overflow means whereby, in use, liquid carried to the top of the bubble tube is returned to the reservoir, and means for discharging from the upper part of the apparatus the vapour bearing gas.

2. Apparatus according to Claim 1 wherein the bubble tube is helical.

3. Apparatus according to any preceding claim wherein the bubble tube is formed with a repetitive variation in the tube bore diameter.

4. A vaporisation bubbler apparatus substantially as described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

especially at high flow rates, by introducing a repetitive variation in the bubble tube bore diameter. As the bubble rate in a smooth bore tube is increased, the bubbles tend to become larger, and as they are prevented from enlarging in the horizontal plane by the tube bore, they must elongate. Thus at higher flow rate in a tube of a given length there will be fewer bubbles. As flow rate increases further the bubbles will continue to elongate until there is just one continuous column of gas blowing through the tube. So the surface area of liquid in contact with the gas is progressively decreased, possibly resulting in reduced saturation levels. By introducing a regular modulation of the tube bore (Fig.

2), at high bubble rates fluid is retained in the bulges 30 up the entire length of the tube, and not as before being largely blown out of the top. Turbulence generated within each bulge also assists in obtaining maximum saturation of the gas.

WHAT WE CLAIM IS: - 1. A vaporisation bubbler apparatus comprising a vertical bubble tube, means for introducing a stream of carrier gas into the lower end of the bubble tube, means for filling the bubble tube from its lower end with a liquid to be vaporised, the internal diameter of the bubble tube being substantially comparable with the size of the bubbles which, when the apparatus is in use, rise up the filled tube, a liquid reservoir connected to the filling means, overflow means whereby, in use, liquid carried to the top of the bubble tube is returned to the reservoir, and means for discharging from the upper part of the apparatus the vapour bearing gas.
2. Apparatus according to Claim 1 wherein the bubble tube is helical.
3. Apparatus according to any preceding claim wherein the bubble tube is formed with a repetitive variation in the tube bore diameter.
4. A vaporisation bubbler apparatus substantially as described with reference to the accompanying drawings.