ABSTRACT
In three-phase gravity separators used in gas and oil production, foaming can occur by either depressurization or injection of gas in the equipment. This formed foam can be harmful, causing various problems such as liquid carry-over, gas carry-under, decreased capacity, and difficulty in level measurement. The mechanism of foam formation by gas injection in separators motivated the present study. Thus, this work proposes the analysis of the influence of certain physical-chemical parameters such as temperature (20-40 °C), pressure (1-10 bar), and types of gases (nitrogen and methane) on the formation of the column and stability of the foam formed, in ISO14 mineral oil + sodium laureth sulfate + water, through gas injection in separator conditions. To carry out this analysis, an experimental apparatus was designed and assembled consisting of a transparent foam formation cell of 0.5 m height and 5 cm internal diameter. Parameters such as foamability, foaminess, and the collapse curve were also evaluated to characterize the foam formed. In addition, simplified models of foam formation and decay by gas injection were proposed based on models already available in the literature, which were validated with the experimentally obtained results. The experimental results showed good agreement when compared to the literature, referring to the behavior of temperature (higher temperature, lower stability), pressure (higher pressure, higher stability), and type of injected gas (dependency on solubility). In addition, maximum errors of 26% (in height) and 11% (decay phase) were obtained for the formation and decay models, respectively.
ABSTRACT
BACKGROUND: Bariatric surgery is a successful method for weight loss in cases of morbid obesity; however, as an invasive procedure, surgical complications may occur. Low-level laser therapy (LLLT) has been increasingly used due to its effectiveness in controlling the inflammatory response, accelerating tissue repair, and reducing pain. The objective of this study was to investigate photobiomodulation effects after bariatric surgery and determine the laser actions during the inflammatory process, wound healing (clinical observation), and analgesia. METHODS: This study was a randomized, placebo-controlled, clinical trial in which 85 patients underwent Roux en-Y gastric bypass (RYGB) by conventional techniques (i.e., open surgery). Patients were divided into two groups and were irradiated with LLLT at 10 different points through the surgical scar in three sessions of applications: the laser group (laser-on) consisted of 43 patients who received the CW diode laser (MMOptics), while the placebo group (laser-off) consisted of 42 patients who were treated by the same protocol but with a disabled laser. Temperature was measured by a digital thermometer in both groups, and pain was evaluated using the visual analogue scale for pain. Biochemical analysis and digital images were used to document and evaluate the inflammatory response as well as tissue repair process at the surgical wound site. RESULTS: Patients in the laser group demonstrated diminished wound temperature as erythrocyte sedimentation rate (ESR) compared with the placebo group, indicating better inflammatory process control as well as improved wound healing and reduced pain. CONCLUSIONS: LLLT applied with the described protocol led to a decrease by biochemical markers and wound temperature compared with the placebo, which indicated that LLLT was able to control the inflammatory process; in addition, seroma and pain were reduced and cicatrization was improved by this preventive procedure.
