No abstract

Vapor−liquid equilibrium data were measured using an automatic static total pressure apparatus for binary mixtures of 2-methylpropene + methanol, + 1-propanol, + 2-propanol, + 2-butanol, and + 2-methyl-2-propanol at 364.5 K. The measured p, T, z data were fitted against Legendre polynomials and reduced using Barker's method to obtain phase equilibrium data. In addition to Legendre polynomials, binary interaction parameters were also optimized for Wilson, UNIQUAC, and NRTL activity coefficient models. All binary data showed a positive deviation from the Raoult's law. In addition, azeotropic behavior was observed for the 2-methylpropene + methanol binary mixture.

An algebraic model for the estimation of gas-liquid packed-bed hydrodynamic parameters is developed, based on one-dimensional material and momentum balances for gas and liquid phases. Underlying momentum exchange closures are critically analyzed, which leads to discarding some interaction models between the phases and development of new models based on local hydrodynamics. The present approach is based on more-relevant assumptions for the particle scale geometry than the slit models presented in the literature. The resulting model requires a one-parameter iterative solution, from which both pressure drop and liquid holdup are obtained. The model can be used without any extra complication in situations where the boundary conditions are specified either at the inlet or at the outlet of the reactor. It is suitable for modeling both low-and highpressure operations, trickling as well as pulsing flow, upflow and downflow arrangements, and processes with Newtonian as well as non-Newtonian liquids. Finally, the present model is compared to its differential counterpart, and to available experimental data from open literature. Reasonably good agreement was observed for both pressure drop and liquid holdup data from a wide range of operating conditions, using only a single set of Ergun parameters.

Chatter is an unfavorable phenomenon in turning operation causing poor surface quality. Active chatter elimination methods require the chatter to be detected before the control reacts. In this paper, a chatter detection method based on a coherence function of the acceleration of the tool in the x direction and an audio signal is proposed. The method was experimentally tested on longitudinal turning of a stock bar and facing of a hollow bar. The results show that the proposed method detects the chatter in an early stage and allows correcting control actions before the chatter influences the surface quality of the workpiece. The method is applicable both to facing and longitudinal turning.

This paper proposes and investigates the application of the gradient heat flux sensor (GHFS) for measuring the local heat flux in power electronics. Thanks to its thinness, the sensor can be placed between the semiconductor module and the heat sink. The GHFS has high sensitivity and yields direct measurements without an interruption to the normal power device operation, which makes it attractive for power electronics applications. The development of systems for monitoring thermal loading and methods for online detection of degradation and failure of power electronic devices is a topical and crucial task. However, online condition monitoring (CM) methods, which include heat flux sensors, have received little research attention so far. In the current research, an insulated-gate bipolar transistor (IGBT) module-based test setup with the GHFS implemented on the base plate of one of the IGBTs is introduced. The heat flux experiments and the IGBT power losses obtained by simulations show similar results. The findings give clear evidence that the GHFS can provide an attractive condition monitoring method for the thermal loading of power devices.