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The present work reports the thermal behavior of synthetic jets (SJs) with different non-circular orifices and various waveforms such as triangular, sinusoidal, and square. Tests are conducted for the different nozzle-to-plate spacing (1–25) for a given value of Reynolds number (5380). The triangular waveform exhibits better heat transfer for all the orifice shapes. The value of maximum heat transfer for rectangular SJ is found to be 32% and 16.5% higher than isosceles and equilateral triangular SJs, respectively. The equilateral triangular SJ exhibits 12.9% higher heat transfer than the isosceles triangular SJ. The power spectral density distribution is plotted for all three waveforms. [ABSTRACT FROM AUTHOR]

AbstractThe present experimental investigation reports the performance of both the single and two stage direct evaporative cooling systems in composite climatic conditions of Patna, India. A two-stage direct evaporative cooling system has been designed and fabricated. The first stage of the two-stage cooling system utilizes a heat exchanger designed internally to sensibly cool hot and arid ambient air. The effect of varying the frontal air velocity (0.5–9 m/s) and different saline water concentration (5–10%) on the performance of two stage direct evaporative cooler is investigated. The maximum effectiveness of single and two-stage desert cooler is found to be 0.7 and 0.98 at frontal velocity of 2 m/s and 2.5 m/s, respectively. The performance of the two-stage cooler with tap water is found to be 40% higher than the single stage desert cooler. The effectiveness of single and two stage desert coolers with tap water is found to be in the range of 6–11% and 9.3–14% higher compared to the saline water at salt concentrations of 5–10%, respectively. Moreover, increasing salt concentration leads to reduced relative humidity at the cooler exit, with the two-stage cooler exhibiting 28.5% lower relative humidity than single-stage desert cooler. [ABSTRACT FROM AUTHOR]

This experimental investigation aims to analyze the heat transfer capabilities of both single and multi-orifice SJs (MOSJs) for varied waveforms(sine, square, and triangular), at a fixed Reynolds number (3525). The jet-to-plate distance and pitch radius is varied in the range of 1–19 and 3.8–8 mm, respectively. The MOSJs at pitch radius (PR) of 3.8 mm shows 30.6% higher average Nusselt number than single SJs. For a PR of 8 mm, the Nusselt number contour shows multiple heat transfer regions adjacent to the stagnation point; however, a single heat transfer region is evident at PR of 3.8–6 mm. [ABSTRACT FROM AUTHOR]

The present article reports the thermal and flow characteristics of single and multi-orifice circular synthetic jet for different waveform shapes through numerical investigation. Present study reports the effect of various parameters such as the pitch ratios (PR = 1.3, 2.1, and 2.8), surface to nozzle distance (z/d = 1–15), and different excitation frequency (f = 50–150Hz) on the thermal performance. The synthetic jet with triangular wave pattern provides higher thermal performance than sinusoidal and rectangular wave patterns for both single and multi-orifice jets. At PR of 1.3, the maximum value of the average Nusselt number for multi-orifice synthetic jet is found to be 17.5% and 39.6% higher compared to PR of 2.1 and 2.8, respectively. At PR of 1.3, f = 150Hz with triangular wave pattern, multi-orifice synthetic jet exhibits 29.8% higher heat transfer compared to single orifice synthetic jet. Present study investigates the flow behavior such as flow interaction between the multi-orifice synthetic jet, jet mass flow rate, and jet half-width for its possible effect on heat transfer rate. The interaction and merging of the adjacent jets are found to be delayed with the increase in the separation distance between the orifice. [ABSTRACT FROM AUTHOR]

The present experimental and numerical analysis reports the thermal performance of circular synthetic jets involving sinusoidal and triangular waveforms. The Reynolds number, dimensionless axial distance, the dimensionless stroke length, and the driving frequency are varied within 4150–5600, 1–18, 5–13, and 80–250 Hz. The average Nusselt number obtained from the triangular waveform exhibits 11% higher heat transfer than the sinusoidal waveform of the synthetic jet. The thermal characteristics of synthetic jet and steady jet are compared, and it is found that synthetic jets exhibit 38.6% higher thermal performance than continuous jets in the far-field region. Also, correlation is proposed for the average Nusselt number. [ABSTRACT FROM AUTHOR]

Present experimental study reports the thermal and flow measurement of multiple-orifice synthetic jet involving circular, square, and rectangular orifice shapes. Here, an infrared camera and constant temperature anemometer are used for measurement of surface temperature and flow velocity, respectively. Reynolds number and the dimensionless axial distance is varied within 1689–4670 and 1–25. The average Nusselt number for the multiple-orifice jet is found to be 60% higher compared to single orifice jets. The power spectral density of the velocity signal is analyzed to understand the vortex dynamics. [ABSTRACT FROM AUTHOR]