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The present study is conducted to investigate the local heat/mass transfer characteristics for flow through perforated plates. A naphthalene sublimation method is employed to determine the local heat/mass transfer coefficients on the effusion plate. Two parallel perforated plates are arranged in two different configurations: staggered and shifted in one direction. The experiments are conducted for hole pitch-to-diameter ratios of 6.0, for gap distance between the perforated plates of 0.33 to 10 hole diameters, and for Reynolds numbers of 5000 to 12,000. The result shows that the high transfer region is formed at stagnation region and at the midline of the adjacent impinging jets due to secondary vortices and flow acceleration to the effusion hole. For flows through the perforated plates, the mass transfer rates on the surface of the effusion plate are about six to ten times higher than for effusion cooling alone (single perforated plate). In general, higher heat/mass transfer is obtained with smaller gap distance between two perforated plates.

The gas turbine blade/vane internal cooling is achieved by circulating compressed air through the cooling channels inside the turbine blade. Cooling channel geometries vary to fit the blade profile. This paper experimentally investigated the rotational effects on heat transfer in an equilateral triangular channel (Dh=1.83 cm). The triangular shaped channel is applicable to the leading edge of the gas turbine blade. Angled 45 deg ribs are placed on the leading and trailing surfaces of the test section to enhance heat transfer. The rib pitch-to-rib height ratio (P/e) is 8 and the rib height-to-channel hydraulic diameter ratio (e/Dh) is 0.087. Effect of the angled ribs under high rotation numbers and buoyancy parameters is also presented. Results show that due to the radially outward flow, heat transfer is enhanced with rotation on the trailing surface. By varying the Reynolds numbers (10,000–40,000) and the rotational speeds (0–400 rpm), the rotation number and buoyancy parameter reached in this study are 0–0.58 and 0–1.9, respectively. The higher rotation number and buoyancy parameter correlate very well and can be used to predict the rotational heat transfer in the equilateral triangular channel.

An experimental study has been conducted to measure the local film-cooling effectiveness and the heat transfer coefficient for a single row of rectangular-shaped holes. The holes have a 35° inclination angle with 3 hole diameter spacing of rectangular cross-sections. Four different cooling hole shapes such as a straight rectangular hole, a rectangular hole with laterally expanded exit, a circular hole and a two-dimensional slot are tested. The rectangular cross-section has the aspect ratio of 2 at the hole inlet with the hydraulic diameter of 10 mm. The area ratio of the exit to the hole inlet is 1.8 for the rectangular hole with expanded exit, which is similar to a two-dimensional slot. A thermochromic liquid crystals technique is applied to determine adiabatic film cooling effectiveness values and heat transfer coefficients on the test surface. Both film cooling effectiveness and heat transfer coefficient are measured for various blowing rates and compared with the results of the cylindrical holes and the two-dimensional slot. The flow patterns inside and downstream of holes are calculated numerically by a commercial package. The results show that the rectangular holes provide better performance than the cylindrical holes. For the rectangular holes with laterally expanded exit, the penetration of jet is reduced significantly, and the higher and more uniform cooling performance is obtained even at relatively high blowing rates. The reason is that the rectangular hole with expanded exit reduces momentum of coolant and promotes the lateral spreading like a two-dimensional slot.

The present study investigates convective heat/ mass transfer and flow characteristics inside rotating disks. The rotating disks are simulated on the commonly used 3:5 00 hard disk drives (HDD). The experiments are conducted for the various hub heights of 5, 10 and 15 mm in a single rotating disk and 4, 6 and 8 mm in co-rotating disks and for the various rotating Reynolds numbers of 5.53 · 10 4 , 8.53 · 10 4 and 1.13 · 10 5 . To accommodate the general operating conditions of HDD, the experiments are also conducted with an obstruction of rectangular crosssection in the space, which simulates a read-write head arm. A naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients on the rotating disks using the heat and mass transfer analogy. Flow field measurements are conducted using laser Doppler anemometry (LDA) and numerical calculations are performed simultaneously to analyze the flow patterns induced by disk rotation. The results of a single rotating disk show that the heat transfer on the rotating disk is enhanced considerably according to the reduction of the hub height and the increase of the rotating Reynolds number. The head arm inserted in the cavity between the rotating disk and the cover enhances uniformity of the heat/mass transfer on the disk due to the deficit of the momentum in the average flow despite the enhancement of the tangential component of fluctuation velocity. The heat/mass transfer rates on the co-rotating disks have very low values near the hub in the inner region of the solidbody rotation and increase rapidly toward the outer region. The change of heat/mass transfer for various hub heights is negligible.

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