Direct-contact mass and heat transfer between vapor and liquid with change of phase
30 Jun 1972-Journal of Chemical Engineering of Japan (The Society of Chemical Engineers, Japan)-Vol. 5, Iss: 2, pp 119-124
TL;DR: In this article, an experimental study was carried out on direct-contact mass and heat transfer between vapor and liquid with change of phase, that is, simultaneous condensation of organic vapor and evaporation of water or water alone in a bubble column equipped with gas dispersion nozzles.
Abstract: Experimental study was carried out on direct-contact mass and heat transfer between vapor and liquid with change of phase, that is, simultaneous condensation of organic vapor and evaporation of water or evaporation of water alone in a bubble column equipped with gas dispersion nozzles. The systems used in this experiment were carbon tetrachloride-water and trichloroethylene-water, which were immiscible in the liquid phase. Volumetric coefficients of vaper phase mass transfer were measured and compared with previous work. From the experimental results, condensation and evaporation rates were calculated under the given operating conditions and the effects of these specified operating conditions on these rates were made clear.
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TL;DR: In this paper, a review of the literature regarding gas-liquid direct contact evaporators is presented, addressing classic and potential applications, bubble regimes, gas holdup and bubble size distributions, as well as mathematical models proposed for simulating the unit.
Abstract: Gas-liquid direct-contact evaporators are characterized by the bubbling of a superheated gas through the solution to be concentrated. In other words, they are nonisothermal bubble columns. Despite their simplicity of construction, these units exhibit rather complex hydrodynamics and, similar to what occurs to isothermal bubble columns, the design of such units still poses a problem. The present paper reviews the literature regarding this kind of equipment, addressing both experimental studies and modeling efforts. The covered issues include classic and potential applications, bubbling regimes, gas holdup and bubble size distributions, as well as mathematical models proposed for simulating the unit. Additionally, pertinent literature on isothermal bubble columns is also discussed. Recommendations are made for future research.
57 citations
TL;DR: In this paper, transient experimental measurements of liquid temperature, bubbling height, evaporation rate, gas hold-up and bubble size distributions in a direct-contact evaporator were performed for four gas superficial velocities including operation in both homogeneous and heterogeneous bubbling regimes.
32 citations
TL;DR: In this article, a novel structured packing, the 4D packing, has been characterized in terms of hydrodynamics, effective area and gas side mass transfer coefficient, which is very interesting for postcombustion CO 2 capture since it generates low pressure drop and a very high interfacial area.
Abstract: A novel structured packing, the 4D packing, has been characterized in terms of hydrodynamics, effective area and gas side mass transfer coefficient. The increase of the 4D opening fraction allows to reduce pressure drop and to get a better capacity than Mellapak 500Y and 750Y, for which the geometric areas are similar. The 50% open 4D packing, 4D-50%, leads to effective areas which are higher than Mellapak 500Y ones, and doubled compared with MellapakPlus 252Y ones. Effective areas for the 4D do not decrease when the opening fraction increases from 30 to 50%, this indicates that a non-negligible amount of droplets is generated at 50%. Gas side mass transfer coefficient had been measured with an original experimental method: water evaporation. Corresponding results seem to be in agreement with the literature, and with the fact that a large amount of droplets is generated. Correlations are proposed for both effective area and gas side mass transfer coefficient for the 4D-50%. The 4D-50% packing could be very interesting for post-combustion CO 2 capture since it generates low pressure drop and a very high interfacial area. This will be further confirmed by an economic study for which the absorber plant will be designed with a rate based model.
21 citations
TL;DR: In this article, a model for simulating direct contact evaporators operating in the homogeneous regime was extended to the heterogeneous bubbling regime, enabling, thereby, the simulation of a direct-contact evaporator for any bubble regime.
20 citations
TL;DR: In this paper, an alternative rote is proposed for fruit juice processing, according to which aroma compounds are extracted by gas stripping in a bubble column and then recovered by vapor permeation, in a first step, the aromadepleted juice being subsequently concentrated by direct-contact evaporation.
Abstract: An alternative rote is proposed for fruit juice processing, according to which aroma compounds are extracted by gas stripping in a bubble column and then recovered by vapor permeation, in a first step, the aroma-depleted juice being subsequently concentrated by direct-contact evaporation. To illustrate the adequacy of the proposed process, experiments were conducted with a synthetic juice, an aqueous solution of sucrose and two esters. In these tests, an aroma recovery degree of about 90% was obtained. Even though the operating pressure was slightly higher than 101 kPa, the liquid temperature did not exceed 66 °C and sucrose concentrations up to 77 wt % were achieved without any reduction in the evaporation rate. Additionally, pervaporation experiments were conducted with an aqueous solution of the esters and the flux results were compared with those related to the vapor permeation tests, revealing that the latter technique is less susceptible to concentration polarization and hence more appropriate for a...
14 citations