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Slip Ratio (slip + ratio)
Selected AbstractsPerformance prediction of a refrigerating machine using R-407C: the effect of the circulating composition on system performanceINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2002P. Haberschill Abstract This article presents a steady-state model of a vapour compression refrigerating machine using a ternary refrigerant mixture R-407C. When using a zeotropic mixture in a refrigerant cycle, the circulating composition does not agree with the composition of the original charged mixture. It is mainly due to the temperature glide and the vapour,liquid slip ratio. As a result of the composition shift and its magnitude, the system performance changes depending on the system design, especially the presence of liquid receiving vessels. In this paper, a method that predicts the circulating composition has been associated to a refrigerating machine model. The results obtained with this model show an enrichment in the most volatile components of about 1% for the circulating composition, which is sufficient to decrease the system performance by about 3%. Factors affecting the overall performance have been investigated. The results show a very strong performance dependence on the refrigerant charge. The COP can decrease by 25% when the refrigerant charge is insufficient. An initial charged composition variation of 2% involves variations of the cooling capacity of about 5%. Furthermore, our model was employed to compare the performance for both R-22 and R-407C. The cooling capacity for R-22 is slightly greater in comparison to R-407C and the COP is almost constant. Copyright © 2002 John Wiley & Sons, Ltd. [source] A new heat balance for flow boilingAICHE JOURNAL, Issue 8 2007Francisco J. Collado Abstract Recently, one of the authors suggested calculating void fraction, an essential element in thermal-hydraulics, working with the "thermodynamic" quality instead of the usual "flow" quality. However, the standard heat balance is currently stated as a function of the "flow" quality. Therefore, we should search a new energy balance between the mixture enthalpy, based on "thermodynamic" quality, and the absorbed heat. This work presents the results of such analysis based on accurate measurements of the axial profile of the cross-sectional average void fraction in the region of boiling with subcooling for water at medium and high pressures taken by Moscow Power Institute (MPI) and Argonne National Laboratory (ANL). As main results, we find that, under uniform heat flux, the mixture enthalpy suffers an abrupt reduction of its slope upon passing saturation point, and a new slip ratio could balance heat with such mixture enthalpy. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Methods to control wheel locks and wheel spins on low friction coefficient roads for front and rear wheel independent drive type electric vehicles (FRID EVs)IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 2 2009Nobuyoshi Mutoh Member Abstract Wheel lock and spin control methods suitable for front and rear wheel independent drive type electric vehicles (FRID EVs) are studied here. Wheel locks and spins occur easily when braking and driving operations such as deceleration and acceleration are performed on bad roads with low friction coefficient such as wet or frozen roads. The methods studied here are characterized by using the structural feature of FRID EVs which can freely distribute the driving and braking torques to front and rear wheels according to running and road surface conditions. These wheel locks and spins occurring when braking and driving on bad roads are controlled by properly distributing the braking and driving torques to front and rear wheels in consideration of the load movement caused by braking operations and slip ratios of the front and rear wheel sides. The effectiveness of the wheel lock and spin methods studied here is verified through simulations and experiments on various roads with a low friction coefficient using a prototype EV with the FRID structure. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Two years of Visual Odometry on the Mars Exploration RoversJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 3 2007Mark Maimone NASA's two Mars Exploration Rovers (MER) have successfully demonstrated a robotic Visual Odometry capability on another world for the first time. This provides each rover with accurate knowledge of its position, allowing it to autonomously detect and compensate for any unforeseen slip encountered during a drive. It has enabled the rovers to drive safely and more effectively in highly sloped and sandy terrains and has resulted in increased mission science return by reducing the number of days required to drive into interesting areas. The MER Visual Odometry system comprises onboard software for comparing stereo pairs taken by the pointable mast-mounted 45 deg FOV Navigation cameras (NAVCAMs). The system computes an update to the 6 degree of freedom rover pose (x, y, z, roll, pitch, yaw) by tracking the motion of autonomously selected terrain features between two pairs of 256×256 stereo images. It has demonstrated good performance with high rates of successful convergence (97% on Spirit, 95% on Opportunity), successfully detected slip ratios as high as 125%, and measured changes as small as 2 mm, even while driving on slopes as high as 31 deg. Visual Odometry was used over 14% of the first 10.7 km driven by both rovers. During the first 2 years of operations, Visual Odometry evolved from an "extra credit" capability into a critical vehicle safety system. In this paper we describe our Visual Odometry algorithm, discuss several driving strategies that rely on it (including Slip Checks, Keep-out Zones, and Wheel Dragging), and summarize its results from the first 2 years of operations on Mars. © 2006 Wiley Periodicals, Inc. [source] | ||||||||||