Refrigeration – Storage of solidified or liquified gas – Liquified gas transferred as liquid
Patent
1995-11-20
1998-03-24
Gluck, Richard E.
Refrigeration
Storage of solidified or liquified gas
Liquified gas transferred as liquid
G21F 908, B01D 130
Patent
active
057299846
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an evaporative transpiration pump. Such pumps are capable of a number of applications but are particularly suitable for use in multi-column cryodistillation systems.
Transpiration pumps and their principles of operation are known. They employ the same physical principle as a tree does to drive sap from the roots to the leaves and facilitate transpiration. A porous barrier is provided with liquid on one side and a heater on the other. The porous barrier retains the liquid by surface tension until the gas pressure on the heated side exceeds the pressure on the liquid side by the amount ##EQU1## where .DELTA.p is the pressure difference, .sigma. is the surface tension and d.sub.eff is the "effective" pore size. The liquid is then sucked through the barrier by capillary action and evaporated by the heater in just the same way as water is evaporated from leaves by the heat of the sun. The above equation is strictly valid only for a barrier consisting of identical capillaries with circular cross-section. However, for example, a transpiration pump having a barrier which is a sinter filter with an effective pore size of 1.times.10.sup.-6 m pumping liquid hydrogen with a surface tension of 2.5.times.10.sup.-3 Nm.sup.-1 can be expected to provide a pressure difference of up to 10 KPa.
Evaporative transpiration pumps may be used for pumping any liquid which is reasonably volatile and can be easily evaporated by the heater. However they have found particular application in very low temperature pumping operations such as in multi-column cryodistillation processes. Such apparatus is described in Fusion Technology 21 (1992) 891-895 where it is used for the processing of the waste gas mixtures which exhaust from a nuclear fusion reactor. These waste gases contain mixtures of hydrogen isotopes such as tritium (T) and deuterium(D) including heteromolecular species such as HD, HT and DT. The cryodistillation apparatus separates such mixtures into three homomolecular product streams, H.sub.2, D.sub.2 and T.sub.2 but it requires pumps to drive the various side streams through catalytic equilibrators and/or recirculation flows against the natural pressure gradient in a system which is multiply interconnected.
Two kinds of pumps have in the past been generally used in multi-column cryodistillation systems, mechanical pumps or hydrostatic syphon pumps.
Mechanical pumps have the disadvantage that in order to be tritium compatible all components must be made entirely of metal and thus they suffer from fatigue over long operational periods. Also they usually need to be operated at room temperature.
Hydrostatic syphon pumps use a U-tube arrangement with a heater in one leg to produce a cold gas stream at a pressure differential corresponding to the hydrostatic difference between liquid levels in both legs. However, due to the low specific gravity of liquefied hydrogen isotopes, only small pressure differences can be generated when other restrictions are taken into account and the devices are prone to pressure oscillations which are difficult to dampen and may adversely effect the separation efficiency of distillation columns.
Evaporative transpiration pumps do not have any of the above drawbacks because of their simple construction and absence of moving parts. Such pumps have therefore been tried in multi-column cryodistillation systems as described in Fusion Engineering and Design 11 (1989) 93-100. However in earlier applications the porous body has comprised a material of relatively high thermal conductivity e.g. nickel or stainless steel. Metal sinter filters prove perfectly adequate for pumping a volatile liquid material containing a single element such as single isotope liquid hydrogen (LH.sub.2) or liquid nitrogen (LN.sub.2), the mass flows of the cold gas being directly proportional to the heater power applied as calculated from the heat of evaporation of the liquid. Thus heater power is only used to evaporate liquid off the porous surface without any superheating of the resulting saturated vapour.
How
REFERENCES:
patent: 1894497 (1933-01-01), Rowland
patent: 2683582 (1954-07-01), Kerr
patent: 3153439 (1964-10-01), Golden
patent: 3565551 (1971-02-01), Hobson
patent: 4255646 (1981-03-01), Dragoy et al.
patent: 4973566 (1990-11-01), Readey et al.
"Themal Conduction in Solids", McGrawhill Encyclopedia of Science & Technology, .COPYRGT. 1992, pp. 277-279.
"A Study of Thermal Transpiration for the Development of a New Type of Gas Pump", IECEC, 1968. pp. 961-972, by Hopfinger et al.
Hemmerich et al., Fusion Engineering and Design, Nov. 1989, Amsterdam, 93-100.
Ulrich et al., Fusion Technology, vol. 21, Mar. 1992, Lagrange Park, 891-895.
Ulrich et al., Fusion Technology, vol. 21, Mar. 1992, pp. 891-895.
Grant & Hackh's Chemical Dictionary, McGraw-Hill Book Company, New York. Table 94.
Hemmerrich Johann Ludwig
Milverton Paul
European Atomic Energy Community (EURATOM)
Gluck Richard E.
LandOfFree
Evaporative transpiration pump having a heater and a pouous body does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Evaporative transpiration pump having a heater and a pouous body, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Evaporative transpiration pump having a heater and a pouous body will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2281033