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This experimental study proposes a new approach to enhance heat transfer performance inside heat exchangers of engine by tandem utilization of bubble injection and a punched zigzag strip turbulator. The side edges of the zigzag turbulator underwent two distinct geometry modifications, involving V and U shape cuts. These cuts were made at varying zigzag angles, ranging from 60° to 150° and four diffirent surface area. The potential improvement in thermal efficiency of the heat exchanger was evaluated at different inlet Reynolds number ranging from 5390 to 10860. Based on survey results, it has been demonstrated that at a Reynolds number of 5390, the Nusselt number and friction factor increase by 48 % and 154 % for U-Cut with a bending angle of 150°, and by 61 % and 170 % for V-Cut, respectively. Hence, V-cut boasts a TEF of 1.15, representing a 6.5 % improvement over U-cut. Additionally, to assess further enhancement, air bubbles with flow rate ranging 2–6 LPM were introduced to the central tube while maintaining the superior geometry. The data suggests that incorporating air bubbles can enhance heat transfer up to 142 %, achieving a TEF of 1.17 at an air flow rate of 6 LPM.

This research delves into the cutting-edge realm of solar-powered dual-temperature refrigeration, adhering to the 3E model emphasizing Energy, Economic, and Environmental considerations with a key focus on financial optimization. The study investigates the implementation of advanced refrigeration technologies, notably the integration of supercritical CO2 and ammonia cycles, tailored for dual-temperature applications. A distinctive aspect of this research is the strategic use of excess thermal energy, enhancing the efficiency of the refrigeration systems under varied climatic conditions. Central to the study is a thorough economic analysis aimed at reducing the Levelized Cost of Cooling (LCOC), while simultaneously enhancing the overall efficiency of the system. With the aid of the Engineering Equation Solver (EES) software, the system is modeled and the preliminary results indicate a promising decrease in cooling expenses (reaching to 90.25 $/GJ) alongside an increase in system efficiency (an improved efficiency of 33.17 %), with the total Coefficient of Performance (COP) demonstrating a significant advancement over traditional refrigeration models. This research underscores the effectiveness of harnessing solar energy in refrigeration technologies, contributing to financially viable and environmentally responsible cooling solutions. It provides valuable insights for the future development of refrigeration systems, which are both economically and environmentally sustainable.

This experimental study proposes a new approach to enhance heat transfer performance inside heat exchangers of engine by tandem utilization of bubble injection and a punched zigzag strip turbulator. The side edges of the zigzag turbulator underwent two distinct geometry modifications, involving V and U shape cuts. These cuts were made at varying zigzag angles, ranging from 60° to 150° and four diffirent surface area. The potential improvement in thermal efficiency of the heat exchanger was evaluated at different inlet Reynolds number ranging from 5390 to 10,860. Based on survey results, it has been demonstrated that at a Reynolds number of 5390, the Nusselt number and friction factor increase by 48% and 154% for U-Cut with a bending angle of 150°, and by 61% and 170% for V-Cut, respectively. Hence, V-cut boasts a TEF of 1.15, representing a 6.5% improvement over U-cut. Additionally, to assess further enhancement, air bubbles with flow rate ranging 2–6 LPM were introduced to the central tube while maintaining the superior geometry. The data suggests that incorporating air bubbles can enhance heat transfer up to 142%, achieving a TEF of 1.17 at an air flow rate of 6 LPM.

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.

One of the performance enhancement strategies in thermoelectric technology is application of two-stage leg instead of normal single stage leg structure. However, for a thin-film solar thermoelectric generator applying this strategy requires many in-depth considerations including economic -cost and reliability aspects. In this research, attempts are made to identify the economic and performance characteristics of a two-stage thin-film solar thermoelectric generator under various geometrical conditions and then compare with normal single stage configuration. Generally, in addition to being cost-effective compared to the single-stage design, the double-stage design can produce more power if the appropriate material is selected. The results of numerical simulations show that the use of bismuth tellurides in single stage thermoelectric generator (SATEG) legs improves the performance of the system in terms of power generation. But the use of skutterudites in the lower layer and bismuth tellurides in the upper layer of the two-stage case, in addition to increasing the output power, significantly reduces the dollar/watt value. Furthermore, the highest output power and exergy efficiency are obtained in the lower layer angle ratio of 0.8–1 and in the upper layer angle ratio of 2. Among the geometrical parameters, the radius of heated area (Rh) has the greatest effect on the performance of double-stage solar annular thermoelectric generator (DSATEG). The highest power output is obtained at Rh = 1.5, which is equal to 1.323W.