## 1 Introduction
### Studying the Effect of Pressure on Gas/Liquid Interfacial Area  
Literature reviews reveal that there are various studies concerning the influence of pressure on the hydrodynamics and mass transfer in gas/liquid systems. Some of the studies are devoted to the influence of pressure on the creation of bubbles. These studies used a capillary tube or single orifices connected to a gas chamber. Other studies have investigated the influence of pressure on interfacial areas in a bubble column, packed column, or tray column. [PERSON] et al. (1962) [5] were the first to observe that an increase in pressure at a single gas inlet orifice and constant superficial gas velocity creates a decrease in the initial bubble volume ([PERSON] 1989) [6]. [PERSON] et al. (1962) [5] suggested that the increase in energy content causes the gas to enter further into the liquid, causing elongated bubbles, which separate more easily from the orifice, leading to smaller bubbles at higher pressures. [PERSON] et al. (1974) [7] studied the influence of pressure and gas flow rates on the creation of CO\({}_{2}\) bubbles in the water at different diameters of orifices photographically. They published the results of the behavior of bubble volume over pressure up to 2.1 MPa at different gas flow rates. They found that the bubble volume is increased when the gas flow rate is increased. Furthermore, it was shown that the bubble volume decreased significantly when the pressure was increased between 0.1-1 MPa, whereas it slightly decreased when the pressure was increased between 1-2.1 MPa. [PERSON] et al. (1978) [8] studied the influence of operating pressure on an initial bubble volume, by sparging N\({}_{2}\) or He through a capillary tube into the water or ethanol. The authors concluded that the influence of the operating pressure is much smaller compared with sparging the gas through an orifice connected to a gas chamber since the gas chamber limits pressure vibrations that happen in close gas supply lines ([PERSON] 1989) [6]. [PERSON] et al. (1987) [9] noted that the diameter of the initial bubble decreases to 25% when pressure is increased from 0.1 to 15 MPa. [PERSON] et al. (1989) [10] determined interfacial areas at pressures up to 1.85 MPa in a bubble column and a packed column. The authors found that the interfacial areas are unaffected by pressure in the packed bubble column, but that the influence of the pressure on the interfacial areas in the bubble column arises from the generation of smaller bubbles at the gas distributor. [PERSON] et al. (1988) [11] investigated the effect of the pressure and superficial velocity of gas and liquid on the interfacial area in a laboratory column equipped with cross-flow sieve trays; they checked that each tested variable has an independent influence on the interfacial area. They investigated the effect of the pressure on the total interfacial area in two different gas-liquid systems, CO\({}_{2}\)-DEA and CO\({}_{2}\)-NaOH. They reviewed that the total interfacial area decreases when the pressure is increased. [PERSON] et al. (1996) [12] studied the effect of pressure on the interfacial area in a counter-current packed column. Their experiment conditions were conducted at specific gas mass flow rates of 0.1 kg/m\({}^{2}\)s, and specific liquid mass flow rates of 5.52 kg/m\({}^{2}\)s. They concluded that the interfacial area decreases when the pressure is increased between 0.1 and 1.2 MPa. [PERSON] et al. (1996) [13] determined the gas-liquid interfacial during CO\({}_{2}\) absorption by using DEA as well as DEA-ETG aqueous solutions. Their experiment device was a bubble column reactor with an inner diameter of 156 mm. The results obtained by [PERSON] et al. (1996) [13] are different; they reviewed that there is no observed influence of pressure on the measured interfacial areas. Most available studies in the literature are interested in the proportional correlation between the pressure and the absorbed amount of gas in a liquid.