A Review of Heat Transfer Enhancement Methods Using Coiled Wire and Twisted Tape Inserts

Heat transfer enhancement is categorized into passive and active methods. Active methods need external power to input the process; in contrast, passive methods do not require any additional energy to improve the thermohydraulic performance of the system. Passive methods are widely used in both experimental and numerical applications when investigating heat transfer enhancement and friction losses to save energy and costs. The many passive methods for increasing heat transfer rate include various components located in the fluid flow path, such as twisted tapes, coiled or tangled wires, and nozzle turbulators. The present paper represents a comprehensive review that focused on heat transfer enhancement methods with coiled wire and twisted tape inserts since the installation of inserts is easier and more economical. The thermodynamic performance of heat exchange components is also affected by the flow conditions such as laminar or turbulence. The present review comprises investigations on the enhancement of heat transfer using twisted tape and coiled wire inserts in laminar and turbulent flow region

The optimization of the thermal and hydraulic characteristics of a tube with twisted tapes using Taguchi-based-AHP-TOPSIS approach

One of the most commonly used techniques in heat transfer enhancement studies is loose-fit twisted tape with variety of configurations. Optimizing the configurations prevents additional effort, time and cost losses. In this regard, the current research examined the impacts of design parameters identified as twist ratio, clearance ratio, and Reynolds number of the loose-fit twisted tape with trapezoidal wings used in a heat exchanger pipe on pressure drop and heat transfer. For the optimization study, the impacts of three various twist and clearance ratios, and six various Reynolds numbers on the friction factor, Nusselt number, and thermohydraulic performance factor identified as performance parameters were evaluated. The optimum conditions were revealed by conducting the signal-to-noise ratio analysis of the Taguchi method for the purpose of maximizing/minimizing the response variables on an individual basis. As methodology, multi-criteria decision-making problem was applied because of the optimum conditions depending on many variables and various response variables. The solution of the multi-objective optimization problem was provided by employing a pair of methods of the AHP/ TOPSIS. The analysis of variance was performed to determine the extent to which every parameter contributed to the response variables. According to the ANOVA findings, the most effective parameter was the Reynolds number. The Reynolds number of 18000, the twist ratio of 2, and the clearance ratio of 0.0178 were chosen as the multi-objective optimum conditions. In relation the results, an approach regarding the optimum design parameters, which has not been revealed before in the use of loose-fit twisted tape, has been put forward.</p

Does dietary intake of acrylamide affect hydroxyproline levels? An animal study

Acrylamide is a chemical that occurs due to high temperatures during cooking. It consists of an amino acid found in foods and sugars. Studies have shown that cancer formation occurs within the scope of oxidant reagents and DNA damage due to exposure to acrylamide. Our study aims to examine the effects of dietary acrylamide intake on plasma hydroxyproline levels in rats. In this study, 4 groups were formed with 8 rats in each group (total number=32). Blood samples were collected on days 14 and 28. Acrylamide solution was applied to each rat in the treatment group by gastric gavage process at 5 mg/kg three times a week. Hydroxyproline levels in rats&apos; plasma samples were measured. The median (IQR) hydroxyproline levels were 7.40(2.45) µg/L in group 1 (14. days control group) and 7.98(3.34) µg/L in group 2 (14. days acrylamide applied) who received acrylamide. The mean hydroxyproline levels were 7.25(1.96) µg/L in group 3 (28. days control group) and 9.76(2.64) µg/L in group 4 (28. days acrylamide applied) who received acrylamide. No difference was observed between the groups. Dietary acrylamide intake did not have a significant effect on hydroxyproline levels at the application dose and duration in our study. [Med-Science 2022; 11(4.000): 1478-81

Human chorionic gonadotropin expression in endometrial hyperplasia and endometrial carcinoma: Could it be a new marker?

Objective: Human chorionic gonadotropin (hCG) is a glycoprotein hormone expressed in a variety of tumors and is correlated with advanced stage disease and poor prognosis. This study aimed to determine hCG expression immunohistochemically in endometrial specimens obtained from patients with normal endometrium, endometrial hyperplasia, and endometrial carcinoma, and to determine if there is a correlation between invasiveness and hCG positivity. Methods: The histologic materials and medical records for patients diagnosed with normal endometrium, endometrial hyperplasia with/without atypia, and endometrial carcinoma between September 2017 and September 2020 were retrospectively reviewed. Immunohistochemical staining for hCG was performed and analyzed semi-quantitatively. Results: A total of 96 patients were included: normal endometrium (27.1%) (n=26); endometrial hyperplasia without atypia (25%) (n=24); atypical endometrial hyperplasia (22.9%) (n=22); endometrioid endometrial cancer (25%) (n=24). Median age of the patients was 48 (range 28-81) years. hCG was positive in 8.3% of patients with endometrial hyperplasia without atypia, 18.2% in those with atypical endometrial hyperplasia, and 41.7% in those with endometrial cancer (p<0.001). None of the patients with normal endometrium had a positive hCG. The rate of endometrial cancer was 62.5% in the hCG-positive group and 17.5% in the hCG-negative group. Conclusion: hCG is expressed to a significantly greater degree in patients with atypical endometrial hyperplasia and endometrial carcinoma and it may be potentially used as a marker for these lesions