A novel fluid for use as a working fluid in a heat pipe has been tested at UCLA. The fluid was discovered originally in use with a device consisting of a metal tube charged with the patented inorganic aqueous solution (IAS) which is evaporated when the tube is evacuated before use. According to the patent, this evaporation leaves a thin film which allows the tube to carry high heat flux loads with low temperature drop across the tube in a solid state mode. However, various experiments with these tubes have produced inconsistent results and there is some question as to whether the fluid is completely evaporated. The research on which this work is based, is focused on testing whether the charging fluid will operate as the working fluid in a heat pipe, in order to determine the nature of the IAS fluid. We charged a heat pipe apparatus with a biporous wick in order to investigate if the fluid plays a role in heat transfer. We have extensive data for this experiment using water as the working fluid which will use to compare the two sets of results. Testing has shown positive results in the reduction of the superheat required to drive heat fluxes through a wick compared to water. Some experiments have shown that the operating (temperature) range of the IAS is much larger than a standard heat pipe. It is theorized that the increase in performance of the IAS is due to an increased heat of vaporization. If this fluid is proven to be effective, it would lead to more effective and tunable heat transfer devices.

Detached turbulent flows are difficult to predict numerically and often serve as benchmark cases for developing new numerical schemes and new turbulent models. Turbulent flow over periodic hills is one such examples, since the flow exhibits separation and reattachment on a smoothly and/or sharp curved geometry, strong pressure gradients and fluctuation of the separation point in time. These cases have been chosen by many authors for testing different turbulence simulation approaches. When the bottom wall is heated, the complexity of the problem increased, since convective heat transfer is defined by small scale turbulent structures close to the wall. We developed a Reynolds-Averaged Navier-Stokes and Large Eddy Simulation solver based on the velocity-vorticity formulation of Navier Stokes equations. RANS equations are coupled by a low-Reynolds number turbulent model, while Smagorinsky subgrid model is used for LES. The governing equations are solved with a numerical solution algorithm, which is based on the boundary element method. The pressure field is computed in a post processing step by solving a Poisson equation. The single domain as well as domain decomposition approaches are applied. The developed method was validated using flow over periodic hills test case.

The critical heat flux values of copper substrates were increased from 87 to 125 W/cm 2 by using a simple chemical process resulting in growth of micro and nano-scale copper structures on the surface. Pre- and post-test surface analysis revealed that the morphology of the micro and nano-scale features of these copper structures changed during the boiling process accompanied by a change in oxide layer composition. Boiling performance of the micro and nano-structured samples was repeatable when testing at lower heat fluxes.

In this paper convective heat transfer performance of various duct geometries are compared using theoretical and experimental analyses. The experiments stretch further by perturbing the entrance region of the 2:1 rectangular duct (both inwards and outwards) and to obtain the effect on heat transfer performance. The cross-sectional area and length of the ducts are fixed and constant heat flux is applied to the ducts while cold water is used as the flow stream. The laminar flow regime is analysed. The theoretical and experimental cases are in agreement, with slight deviances attributed to certain assumptions made during the theoretical analysis and non-ideal testing conditions. The analyses concludes that perturbing the entrance region of a standard rectangular duct, both inwards and outwards, has a visible increase in heat transfer performance. The inward perturbed duct shows the highest increase in performance. The average variation between the theoretical and experimental case is about 18% for constant heat flux. The average error imposed on the results due experimental equipment is about 3% for constant heat flux experiments.

The transient thermal flash technique, originally developed for testing low thermal diffusivity micro/nanofibers, was implemented for measuring the thermal conductivity of vapor-grown carbon nanofibers. The present technique uses a microfabricated strip of gold, which acts both as a heater and a temperature sensor. The modifications were validated against commercially available carbon fibers (Pyrograf ® – I from Applied Sciences, Inc. and Mitsubishi K13D2U) and the results obtained were seen to match values previously reported in the literature. The carbon nanofibers reported in this article were also obtained from Applied Sciences, Inc. and are known as PR-25, belonging to the Pyrograf ® – III family of nanofibers. The thermal conductivities calculated based on the experimentally determined values of diffusivity along with the specific heat capacity and density of graphite were around 1100 W/m-K and 1700 W/m-K, respectively for the nanofibers heat treated to 1100 °C and 3000 °C.

Improved understanding of coal gasification chemical kinetics is needed to increase thermodynamic efficiency and to reduce undesirable CO 2 emissions. This work describes an optically-accessible entrained-flow coal gasifier designed and built to allow measurements of the major species at various stages of the chemical reactions. The 2-meter tall gasifier consists of five subsystems: the optical diagnostics, steam generator, coal feeder, external heaters, and gas sampling and analysis. A stoichiometric H 2 -O 2 flame generates superheated steam, the gasifying agent, which reacts with pulverized coal fed from a variable feed-rate pressurized powder feeder. To sustain the endothermic coal gasification reaction, radiant heaters provide 15 kW of external heating. Diagnostics to determine the major species concentrations consist of tunable diode laser absorption spectroscopy (TDLAS) measurements within the reactor vessel assembly and analysis of dry product gases using a gas chromatograph.

The effects of the Coriolis force and centrifugal buoyancy are well known in rotating internal serpentine coolant channels in turbine blades. As channel flow in rotation is highly complex, detailed knowledge of the heat transfer over a surface will greatly enhance the blade designer’s ability to predict hot spots so coolant may be distributed effectively. The present study uses a novel transient liquid crystal technique to measure heat transfer on a rotating two-pass channel surface with chilled inlet air. The present study examines the differences in heat transfer distributions of three channel types in rotation: smooth wall, 90° ribs, and W-shaped ribs. The two channels in the test section model radially inward and outward flow. To account for centrifugal buoyancy, cold air is passed through a room temperature test section. This ensures that buoyancy is acting in a similar direction to real turbine blades. Three parameters were controlled in the testing: inlet coolant-to-wall density ratio, channel Reynolds number, and Rotation number. Results were compared to previous studies with similar test conditions. The present study shows that the W-shaped ribs enhance heat transfer in all cases (stationary and rotating) approximately 2–3 times better than the 90° ribs. The W-shaped ribbed channel is least affected by rotation due to the complex nature of the flow generated by the geometry.

Circulating water systems (CW) and safety water systems (SW) in various power plants use vertical pumps to pump water from pump intakes. A properly designed pump intake structure prevents the occurrence of strong surface vortices, which might inhibit the proper functioning of the pump. Although several standards for experimental testing of pump intake structure suitability exist, our goal is to find a way to predict such vortices numerically, from a single-phase simulation. In such a process, we had already eliminated some of the turbulence models. In the current paper we confirm that Scale Adaptive Simulation (SAS) turbulence model with the curvature correction (CC) factor applied is well suited for such flows. By using a methodology for determining the vortex air core length, the SAS-CC turbulence model results were compared to the experimental data for two selected temperatures. The results show better agreement than the laminar simulations in terms of higher mean value accuracy and lower scattering.