This paper provides a review of the literature on condition monitoring of a gearbox. The progress and changes over the past 30 years in failure detection techniques of rotating machinery including helicopter transmission are reviewed. Vibration Analysis techniques, indicators and parameters used in condition monitoring are arranged in a historical perspective. The use of vibration-based analysis damage detection techniques is classified and discussed in details. The capability of each technique to sense failure and damage in rotary equipments is addressed. These diagnostics techniques in gearbox condition monitoring are organized and regrouped in this review paper in a better approach so they can be easily recognized.
This work involves measurements, analyses, and evaluation of performance of air-source heat pump water heaters (HPWHs), and their impacts on electric utility loads. Two add-on, heat pumps (HPs) rated at 7000 BTU/h (2.051 kW) and 12,000 BTU/h (3.517 kW) were utilized. The HPs were retrofitted to two 50 gal (189.3 l) electric water heaters (EWHs) with their electric heating elements removed. A third standard EWH was used for comparison. The testing setups were fully instrumented for measurements of all pertinent parameters, including inlet and outlet water temperatures, inlet and outlet air temperatures of the HPs, temperature and humidity of the surrounding air, volume of water drawn out of the storage tanks, as well as the electric energy consumptions of the systems. Performance measures evaluated included the coefficient of performance, the energy factor (EF), and the first hour rating (FHR). The HPWH systems gave EFs ranging from 1.8 to 2.5 and corresponding energy savings (and reductions in utility peak loads) ranging from 49.0% to 63.0%, approximately. The values obtained in the summer months were, as expected, somewhat higher than those obtained in the winter ones. The average values of the EFs and energy savings (and reductions in utility peak loads) were about 2.1 and 56.0%, respectively. FHR results were much lower for the HPWHs compared with those for the standard EWH. These results show that HPWHs are much more efficient compared with standard EWHs. While the average value of the EF for the EWH was about 0.92, the HPWHs yielded EFs averaging more than 2.00, resulting in annual energy savings averaging more than 50%. The results also show that HPWHs are effective at reducing utility peak loads, in addition to providing substantial cost savings to consumers.
Owing to the increasing miniaturization and number of high-power-dissipating components in electronic packages, proper thermal management has become of vital importance. Numerical simulations were carried for three block-type elements representing electronic components located on the bottom plate of a rectangular channel. The top plate of the channel was parametrically examined in order to assess the radiative heat-transfer component. The effects of the air flow rate in the channel and the spacing, geometry, and emissivity of the blocks were investigated. Two types of heat sources were considered: A uniform heat-generation rate in each block and a point heat-source at the center of each block. Reynolds numbers varying from 10 to 1000 and block length-to-spacing ratio varying from 1 to 3.7 were considered in this work. The results clearly indicate that, when the radiative heat-transfer component is neglected, 33% of the heat generated is conducted through the bottom substrate while the remaining 67% is convected to the cooling medium. However, when the radiative heat transfer is considered in the analysis, the radiant heat loss is estimated to range from 4 to 8%, at a Reynolds number of 500.
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