The objective of this research was to investigate pin fin midline heat transfer in terms of our understanding of stagnation region heat transfer for cylinders in cross flow and turbine airfoils. An experimental investigation was conducted in a staggered-pin fin array at Reynolds numbers of 3000, 10,000, and 30,000 based on the maximum velocity between cylinders. Midline distributions of static pressure and heat transfer were acquired for rows 1 through 8 at the three Reynolds numbers. Turbulence measurements and velocity distributions were acquired at the inlet and in between adjacent pins in rows using hot wire anemometry. One-dimensional power spectra were calculated to determine integral and energy scales. Midline heat transfer distributions are reported as the Nusselt number divided by the square root of the Reynolds number as a function of angle. In these terms, heat transfer was found to increase through row 3 for a Reynolds number of 30,000. After row 3, heat transfer diminished slightly. The Reynolds number for each row was recast in terms of an effective approach velocity, which was found to be highest in row 3 due to the upstream blockage of row 2. Based on this effective velocity the Nusselt number divided by the square root of the Reynolds number increased through row 4. These data indicate that heat transfer is highest in row 3 pins due to the highest effective velocity, while heat transfer augmentation due to turbulence is highest in row 4 and beyond. Hot wire measurements show higher turbulence intensity and dissipation rates upstream of row 4 compared to upstream of row 3. Generally, pressure, heat transfer, and turbulence measurements were taken at all rows, providing a better understanding of turbulent transport from pin fin arrays.
The objective of this reserch was to investigate pin fin midline heat transfer in terms of our understanding of stagnation region heat transfer for cylinders in cross flow and turbine airfoils. An experimental investigation was conducted in a staggered pin fin array at Reynolds numbers of 3000, 10,000, and 30,000 based on the maximum velocity between cylinders. Midline distributions of static pressure and heat transfer were acquired for rows 1 through 8 at the three Reynolds numbers. Turbulence measurements and velocity distributions were acquired at the inlet and in between adjacent pins in rows using hot wire anemometry. One dimensional power spectra were calculated to determine integral and energy scales. Midline heat transfer distributions are reported as Nusselt number divided by the square root of Reynolds number as a function of angle. In these terms, heat transfer was found to increase through row 3 for a Reynolds number of 30,000. After row 3, heat transfer diminished slightly. Reynolds number for each row was recast in terms of an effective approach velocity, which was found to be highest in row 3 due to the upstream blockage of row 2. Based on this effective velocity Nusselt number divided by the square root of Reynolds number increased through row 4. These data indicate that heat transfer is highest in row 3 pins due to the highest effective velocity while heat transfer augmentation due to turbulence is highest in row 4 and beyond. Hot wire measurements show higher turbulence intensity and dissipation rates upstream of row 4 compared to upstream of row 3. Generally pressure, heat transfer, and turbulence measurements were taken at all rows providing a better understanding of turbulent transport from pin fin arrays.
The objective of this research has been to experimentally investigate the fluid dynamics of pin fin arrays in order to clarify the physics of heat transfer enhancement and uncover problems in conventional turbulence models. The fluid dynamics of a staggered pin fin array have been studied using hot wire anemometry with both single and x-wire probes at array Reynolds numbers of 3000; 10,000; and 30,000. Velocity distributions off the endwall and pin surface have been acquired and analyzed to investigate turbulent transport in pin fin arrays. Well resolved 3-D calculations have been performed using a commercial code with conventional two-equation turbulence models. Predictive comparisons have been made with fluid dynamic data. In early rows where turbulence is low, the strength of shedding increases dramatically with increasing in Reynolds numbers. The laminar velocity profiles off the surface of pins show evidence of unsteady separation in early rows. In row three and beyond laminar boundary layers off pins are quite similar. Velocity profiles off endwalls are strongly affected by the proximity of pins and turbulent transport. At the low Reynolds numbers, the turbulent transport and acceleration keep boundary layers thin. Endwall boundary layers at higher Reynolds numbers exhibit very high levels of skin friction enhancement. Well resolved 3-D steady calculations were made with several two-equation turbulence models and compared with experimental fluid mechanic and heat transfer data. The quality of the predictive comparison was substantially affected by the turbulence model and near wall methodology.
Six platinum(II) complexes of the general formula [Pt(cbdc)(HLn)2] (1–6; cbdc = cyclobutane‐1,1‐dicarboxylate and HL1–HL6 = benzyl‐substituted 6‐benzylamino‐2‐chloro‐9‐isopropylpurine derivatives) have been synthesized by the reaction of [Pt(cbdc)(dmso)2] with the corresponding HLn compound. The prepared complexes were characterized by elemental analysis and FTIR, Raman and NMR (1H, 13C, 15N and 195Pt) spectroscopy. Based on the results of these techniques, it can be concluded that the central PtII atom of the complexes 1–6 is coordinated to two oxygen atoms originating from the cyclobutane‐1,1‐dicarboxylate group and to two nitrogen atoms from two HLn molecules, that is, having a PtN2O2 donor set. Detailed multinuclear and two‐dimensional NMR studies indicated the N‐7 atom to be the coordination site of the purine derivatives. The coordination mode was proven by a single‐crystal X‐ray analysis of the [Pt(cbdc)(dmso)(HL7)]·H2O (7a·H2O) intermediate [HL7 = 2‐chloro‐6‐(2‐methoxybenzyl)amino‐9‐isopropylpurine]. The geometry is slightly distorted square‐planar and the central PtII atom is coordinated to one bidentate cyclobutane‐1,1‐dicarboxylate dianion, one dmso molecule through the sulfur atom and one HL7 molecule through the N‐7 atom of the purine ring, that is, with a PtNO2S donor set. The complexes 1–6 were tested for their in vitro cytotoxicity against K‐562 (chronic myelogenous leukaemia) and MCF7 (breast adenocarcinoma) human cancer cell lines. Values of IC50 (drug concentrations lethal for 50 % of the tumour cells) ranged from 4.5 to 14.1 μM for the K‐562 cells and from 4.3 to 21.0 μM for the MCF7 cells. The in vitro cytotoxicities were in several cases comparable or even higher than those of therapeutically used platinum‐based anticancer drugs, that is, cisplatin, carboplatin andoxaliplatin.
The objective of this research has been to experimentally investigate the fluid dynamics of pin fin arrays in order to clarify the physics of heat transfer enhancement and uncover problems in conventional turbulence models. The fluid dynamics of a staggered pin fin array has been studied using hot wire anemometry with both single- and x-wire probes at array Reynolds numbers of 3000, 10,000, and 30,000. Velocity distributions off the endwall and pin surface have been acquired and analyzed to investigate turbulent transport in pin fin arrays. Well resolved 3D calculations have been performed using a commercial code with conventional two-equation turbulence models. Predictive comparisons have been made with fluid dynamic data. In early rows where turbulence is low, the strength of shedding increases dramatically with increasing Reynolds numbers. The laminar velocity profiles off the surface of pins show evidence of unsteady separation in early rows. In row three and beyond, laminar boundary layers off pins are quite similar. Velocity profiles off endwalls are strongly affected by the proximity of pins and turbulent transport. At the low Reynolds numbers, the turbulent transport and acceleration keep boundary layers thin. Endwall boundary layers at higher Reynolds numbers exhibit very high levels of skin friction enhancement. Well-resolved 3D steady calculations were made with several two-equation turbulence models and compared with experimental fluid mechanic and heat transfer data. The quality of the predictive comparison was substantially affected by the turbulence model and near-wall methodology.
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