•Effect of multi-magnetic turbulator on hydrothermal parameter was clarified.•Effect of geometry and arrangements of turbulator on heat transfer was investigated.•The highest heat transfer was ...observed in the presence of quadruple strip turbulator.•Most optimum state was selected using thermal enhancement factor (TEF).•Magnetic turbulator increases TEF up to 3.02 times that of the plain tube.
Electromagnetic vibration (EMV) is a novel active method to enhance heat transfer in heat exchangers. This method installs a magnetic turbulator vibrating at a specific frequency inside a tube. Recent studies have used a single turbulator inside the tube. This paper is the first exploration of the effect of using multiple turbulator on hydrothermal parameters. In this regard, a turbulator with strip or string geometries with three different arrangements of double, triple, and quadruple turbulators was placed inside the tube to investigate its effect on heat transfer and pressure drop. Experiments were performed for the Reynolds number range from 500 to 1500. The results indicated the significant effect of the geometry and the magnetic turbulator arrangement on hydrothermal parameters. The highest heat transfer and thermal enhancement factor (TEF) were observed in a quadruple strip turbulator. In the presence of this turbulator, heat transfer was up to 3.02 times that of the plain tube, and TEF was 2.01.
•Effect of perforated magnetic turbulator on the hydrothermal parameters was presented.•Effect of the hole pitch and hole diameter on the hydrothermal parameters was clarified.•This turbulator ...increases heat transfer up to 1.53 to 3.82 times of a plain tube.•Optimal pitch and diameter were selected using TEF.•Turbulator with hole of 2 mm and pitch of 6 mm was selected as optimal case.
The utilization of a magnetic turbulator presents a novel method for enhancing heat transfer in heat exchangers. This research introduces the use of both simple and perforated magnetic turbulators for the first time, aiming to optimize the thermal enhancement factor. The perforated magnetic turbulator is a composite of a magnet and a perforated oscillator. By inducing an alternating magnetic field around the tube, the magnet and, thus, the oscillator are forced to oscillate and as a result act as a flow disruptor. The oscillator is designed with holes in four varying diameters 1, 2, 3, and 4 mm and five distinct pitches 4, 6, 12, 18, and 24 mm to examine the impact on pressure drop and heat transfer. Also, to ascertain the optimal case, the thermal performance factor has been used. Tests have been carried out in the hot fluid flow range from 0.23 to 1.38 l/min. According to the results, the highest amount of heat transfer has been observed in the presence of a simple magnetic turbulator. The heat transfer and friction factor ratio in the presence of best case were 1.67 to 5.7 and 1.04 to 1.34 times higher than those of the plain tube, respectively. Meanwhile, the maximum value of the thermal performance coefficient (5.35) was observed in the presence of a perforated turbulator with a hole diameter of 2 mm and a pitch of 6 mm.
Considering that turbulators generally have a high pressure drop level and as a result low thermal performance, in this research a numerical study conducted for a new form of aerodynamically designed ...turbulators that are concentrically perforated to have less pressure drop. In this study, the effects of a novel perforated teardrop-shaped turbulator (PTST) on the hydro-thermal parameters were numerically examined. Results were compared with a plain tube and a tube equipped with a simple teardrop-shaped turbulator (STST). PTST with the horizontal perforation geometry including a square, hexagon, octagon, and circle holes was installed inside a copper tube with constant wall temperature. The effect of the horizontal perforation cross-section area on the heat transfer and pressure drop was also evaluated. Tests were conducted under turbulence flow rates in the range of 0.044–0.099 kg/s. To select the optimal case, the thermal enhancement factor (TEF) was calculated. The results clarified that the hole area and hole geometry have a significant effect on TEF and hydro-thermal parameters. The highest heat transfers and pressure drop took place in the presence of the STST, while the highest TEF was equivalent to 1.39 and occurred in the presence of a PTST with a 5 mm diameter circular hole. The heat transfers in the presents of STST and PTST increased by 310.1% and 298% compared to the plain tube. Finally, a correlation expressing the relationship of TEF and perforation area was also presented based on curve fitting.
•Hole with different geometry of square, hexagon, octagon, and circle was made on the STST to increase TEF of heat exchanger.•Effects of STST and PTST on hydro-thermal parameters were compared.•Effects of hole geometry and hole area on hydro-thermal parameters were clarified.•The highest heat transfers and pressure drop was happened in the presence of a STST.•Optimal case was selected using TEF. PTST with a 5 mm diameter circular hole was selected as optimal case.
In this study, the effect of simultaneously using two active and passive methods, namely the magnetic turbulator and the helical coil wire (HCW) turbulator, on the hydrothermal parameters of a double ...tube heat exchanger is being evaluated for the first time. The results are also being compared with those of a simple heat exchanger, a heat exchanger equipped with a magnetic turbulator, and a heat exchanger with a HCW turbulator insert. Finally, the most optimal option is selected using TEF. Tests have been conducted using different pitch ratios of the HCW turbulator (ranging from 2.5 to 10) and fluid flow rates (ranging from 0.5 to 4 l/min). According to the results, the usage of the HCW turbulator, magnetic turbulator, and the simultaneous use of both turbulators increases heat transfer by 237 %, 262 %, and 491 %, respectively. Additionally, the pressure drop in the presence of these two methods is 3.8 times that of a simple heat exchanger. Furthermore, with the help of TEF, the heat exchanger armed with both turbulators is chosen as the optimal option, achieving a TEF of 3.78.
•Magnetic turbulator and HCW turbulator were utilized separately as well as in combination in a DTHEX.•Effect of the pitch ratio of HCW on hydrothermal parameters of a DTHEX was investigate.•Heat transfer in the simultaneous presence of two turbulators is up to 3.8 times of the simple DTHEX.•The highest amount of TEF was observed in the simultaneous presence of two turbulators (TEF = 3.78).•The pitch ratio of 5 was chosen as the most optimal pitch ratio using TEF.
The magnetic turbulator and electromagnetic vibration (EMV) methods have recently been employed to enhance heat transfer in heat exchangers. This method involves placing a magnetic oscillator inside ...the tube and attaching a magnet with specific dimensions to this oscillator. Creating an AC magnetic field near the tube causes the magnet and the oscillator to vibrate, acting as a magnetic turbulator. In this study, multiple perforated magnetic turbulators were used inside the tube of a heat exchanger for the first time, and their impact on hydrothermal parameters was assessed. Various factors were examined, including perforation diameter, pitch, and fluid flow rate. The thermal enhancement factor (TEF) was used to identify the optimal configuration. The results showed that simple and perforated turbulators increased heat transfer up to 156% and 150%, respectively. However, the pressure drop in the presence of these turbulators was up to 1.97 and 1.86 times higher than that of a simple heat exchanger. In addition, the maximum value of TEF was observed in the presence of a perforated magnetic turbulators with a hole diameter of 2 mm and a hole pitch of 12 mm. This turbulator was the optimal choice, providing a TEF equivalent to 2.06.
This study proposes a novel twisted tape turbulator with a unique DNA-like shape, referred to as the special shape twisted tape turbulator (SSTT), to augment the heat transfer efficiency within heat ...exchanger conduits. This turbulator is composed of segmented components and facilitates the passage of fluid flow through the gaps while inducing swirling motion along the conduit. The pitch ratio of the segments has been examined within the range of 1–4 mm to evaluate its impact on the heat transfer properties. The findings indicate that the novel geometry offers notable benefits compared to a basic twisted tape design. Optimal heat transfer occurs at a pitch ratio of 2 mm, resulting in a 125% improvement over a plain tube. To further improve thermal efficiency, a helical coiled wire turbulator is incorporated alongside the tube, in combination with the chosen SSTT. The findings indicated a 142% rise in the heat transfer coefficient, accompanied by a 960% increase in pressure drop in the presence of these turbulators. Consequently, the thermal performance reached 1.31, representing a 20% improvement compared to a basic twisted tape turbulator.
In this experimental study, a novel approach combining a helical coiled wire (HCW) turbulator and bubble injection (BI) method has been employed to synergistically improve the heat transfer ...efficiency of double tube heat exchanger. The thermal-frictional characteristics were evaluated by investigating different parameters, including the bubble injection flow rate ranging from 2 to 5 l/min and HCW pitch ranging from 2.5 to 10 mm. For all cases, the thermal enhancement factor (TEF) is employed to determine the optimal configurations. The experimental findings indicate that the introduction of bubble injection, the implementation of the HCW turbulator, and the simultaneous utilization of both methods result in an enhancement of heat transfer by 66 %, 78 %, and 156 % respectively. However, it should be noted that the usage of these methods also leads to an increase in pressure drop. Also, the findings indicate that the integration of two methods yields favorable outcomes in terms of thermal performance when compared to their individual functions. In the optimal scenario, the TEF has the potential to reach a maximum value of 1.28. Furthermore, in order to obtain a more precise comprehension of the relationship between TEF and the parameters under investigation, an empirical equation have been derived and presented.
This study represents a pioneering investigation into the impact of a punched twisted tape turbulator on the hydrothermal parameters of a pipe operating under constant surface temperature conditions. ...The punched turbulator was specifically designed by incorporating cuts with diverse geometries, including semicircular, square, and triangular shapes, into the basic twisted tape turbulator. To evaluate the performance of the punched twisted tape, a comparative analysis was conducted with both a smooth tube and a tube equipped with a basic turbulator. The criterion for selecting the optimal cut geometry was the thermal enhancement factor. Subsequently, the influence of the cut area on the hydrothermal parameters was thoroughly elucidated. The enhancement factor was again utilized to identify the most optimal area. Based on the comprehensive evaluations, it was observed that the turbulator with a semicircular cut geometry and a diameter of 5 mm exhibited superior thermal performance compared to all other geometries. By employing this specific turbulator design, a remarkable enhancement in heat transfer and pressure drop within the heat exchanger was achieved, offering improvements of up to 1.63 and 3.65 times, respectively, when contrasted with the plain tube. The maximum enhancement factor value recorded during the investigation reached 1.09.
For the purpose of enhancing the thermal efficiency of double-tube heat exchangers, a new technique has been implemented. By integrating a vibrating turbulator and bubble injection technique, this ...innovative method produces an added turbulence effect. This research aims to experimentally assess the thermal efficiency of employing two active methods concurrently. Different parameters were analyzed, including water flow rates ranging from 0.5 to 4 kg/min and bubble injection flow rates varying from 2 to 6 l/min, to investigate the effects on heat transfer and pressure drop with and without the magnetic turbulator. The results suggest that by incorporating bubble injection, adopting the magnetic turbulator, and simultaneously utilizing both methods, there is a significant improvement in heat transfer. In optimal scenarios, the heat transfer coefficient is amplified by 150.3% through the injection of bubbles, 328.8% through the implementation of magnetic turbulator, and 586.2% when both techniques are employed in tandem. In comparison to the smooth tube, the friction factor ratios were 6.7, 1.6, and 7.8 times higher in the specified cases. The findings indicated that the concurrent utilization of both techniques can yield an added impact on heat transfer. Ultimately, the integrated approach demonstrated a noteworthy thermal enhancement factor value of 3.49.
For the first time, three alternative techniques were used in this research to enhance the thermal performance of a double pipe heat exchanger: the air bubble injection method, the use of a ...perforated wavy strip turbulator, and the use of Nano fluids as the working fluid. Distinct bubble injection flow rates ranging 2–6 LPM and turbulators with variable hole diameter ratio (D/L) were used in the experiments. Working fluids have included water, air/water, CuO-water, and air/CuO-water with different volume fractions ranging 0.25 % to and 1 %. Based on the findings, the use of Nano fluid, the PWST and bubble injection method increased the heat transfer by 56, 53 and 14.1 %, respectively. Also, the simultaneous employment of these three techniques increases heat transfer and exergy losses up to 2.15 and 1.82 times greater than those of plain pipe, respectively. The double pipe heat exchanger equipped with a perforated wavy strip turbulator with a hole diameter ratio of 6 and bubble injection with m˙a = 6 LPM was chosen as the best-case utilizing net profit per unit transferred heat load (ηp) and thermal performance factor (TEF). In this case, the maximum amount of ηp and TEF are equal to 2.124 × 10−9 and 1.24, respectively.
