Sinan Caliskan

Design Analysis of Impinging Jet Array Heat Transfer From a Surface With V-Shaped and Convergent–Divergent Ribs by the Taguchi Method

In this work, the effects of the impingement plate geometry, Reynolds number, jet-plate distance-to-jet diameter ratio, and the jet diameter-to-rib height ratio on the impingement jets were investigated using the Taguchi experimental design method. The heat transfer measurements over a surface with V-shaped ribs (V-SR) and convergent-divergent shaped ribs (CD-SR) by a circular impinging jet array were investigated using a thermal infrared camera. Both V-SR and CD-SR configurations, with an angle of 45°, were considered. Both projected and total Nusselt numbers were considered as performance statistics. After the data on each quality characteristic were obtained from the orthogonal arrays, a main effect analysis and analysis of variance (ANOVA) were conducted to determine the parameters that had significant effects on these quality characteristics. The L32 (21 × 43) orthogonal array was selected as an experimental plan for the four parameters. The Taguchi method was applied with an optimization process to reach the maximum heat transfer. Experimental results validated the suitability of the proposed approach. The best heat transfer performance was obtained with the V-SR arrangements.

Transient Turbulent Flow and Heat Transfer Phenomena in Plate-Fin Type Cross-Flow Heat Exchanger

In this article, a transient performance of a plate-fin cross-flow heat exchanger with convergent–divergent longitudinal vortex generators is investigated. The effect of flow geometry is taken into account to analyze the transient forced convection heat transfer in a designed heat exchanger. The time-dependent Nusselt number and dissipation energy criterion are experimentally measured in 4- and 8-kW heater powers for various Reynolds numbers between 42,000 and 60,000 for the hot and cold fluids. In order to present the quality of the heat exchanger, the general empirical equations of the time-dependent Nusselt number and friction factor were derived as a function of the Reynolds number corresponding to fin geometry parameters. Following this, the transient behavior of the heat exchanger according to the change in the inlet and outlet temperatures of the hot and cold fluids was analyzed. The results showed that the variations of the time-dependent dissipation energy criterion increase with the increase in the Reynolds number. The appropriate correlations are proposed to predict the heat transfer and friction characteristics of the transient performance for the presented configuration, which indicates the designed heat exchanger has good heat conduction.

Experimental investigation of heat transfer from different pin fin in a rectangular channel

ABSTRACT In this study, the effect of both hexagonal pin fins (HPFs) and cylindrical pin fins (CPFs) into the rectangular channel on heat transfer augmentation, Nusselt number and friction factor were experimentally investigated. In planning of the experiments, different Reynolds number, pin fin array, pin fin geometry and the ratio of the distance between pin fin spacing (s) to the pin fin hydraulic diameter (s/Dh) were chosen as the design parameters. Air was used as the fluid. The Reynolds number, based on the channel hydraulic diameter of the rectangular channel, was varied from 3188 to 19531. In the experiments, the heating plate was made of stainless steel foil. The foil was electrically heated by means of a high current DC power supply to provide a constantly heated flux surface. The heat transfer results were obtained using the infrared thermal imaging technique. The heat transfer results of the hexagonal pin fins (HPFs) and cylindrical pin fins (CPFs) are compared with those of a smooth plate. Best heat transfer performance was obtained with the hexagonal pin fins. The maximum thermal performance factor ((Ƞ), was obtained as Re = 3188, staggered array, s/Dh = 0, Ƞ = 2.28.