Temperature has a substantial impact on the safety, efficiency, and reliability of a lithium-ion (Li-ion) battery. The objective of a battery thermal management system (BTMS) is to maintain the battery in preferred temperature range. State-of-the-art BTMS is designed to react to the measured temperature at the battery surface, whereas research suggests that the performance of BTMS will likely improve when used in conjunction with predicted temperature. This article focuses on surface temperature prediction of Li-ion batteries based on an equivalent circuit model-based approach. Particularly, this article presents theoretically sound approaches to model heat generation in the core of the battery and its propagation to its surface. Another novel aspect of the present article is that the heat generation and propagation model identification is tested in various practical scenarios, where the measurement noise is significant. Experimental results using data collected from high precision battery cycler and temperature sensor show an open-loop mean absolute error of 1.678 $^{\circ }$ C during a high-current discharge that lasted approximately 800 s. Using the theoretical models presented in this article, the performance battery temperature prediction error at low SNR conditions can be understood.

The results of an experimental investigation of the energy separation performance of a microscale Ranque–Hilsch vortex tube are presented. The supply channel Reynolds number of a microscale Ranque–Hilsch vortex tube is varied over a considerable range, which extends into the laminar flow regime in order to determine the minimum conditions for cooling. Experiments are conducted for a fixed geometry and control valve setting. At low Reynolds numbers based on the inlet tube hydraulic diameter and average velocity, the results exhibit an increase in dimensionless temperature in both the hot and cold outlets as the Reynolds number is increased from zero, reaching maximum values below 500 and 1000, respectively. The hot outlet dimensionless temperature decreases after reaching its maximum and achieves a minimum value at a Reynolds number below 1500. It then increases steadily with further increases in Reynolds number. The cold outlet dimensionless temperature decreases steadily after the maximum to become negative at a Reynolds number of approximately 1800. This implies that the cooling effect occurs at Reynolds numbers consistent with turbulent flow. The performance characteristics of the microscale vortex tube operating at higher inlet pressures of $200kPa$, $300kPa$, and $400kPa$ with an average inlet temperature of $293.6K$ are also presented for cold air mass ratio values over the range of 0.05–0.95. An increase in the inlet pressure causes the values of the dimensionless cold temperature difference to increase over the whole range of the cold air mass fraction. An unstable operation is observed at a length to diameter ratio of approximately 10, causing radial mixing between the cold and hot flow streams and a dramatic change in the cold mass flow fraction plot.

This paper describes the development and evaluation of a novel equivalent fluid circuit model capable of accurately predicting the performance of a load-type bistable supersonic fluidic oscillator. The model utilizes some aspects of previous models that are available in the literature. It is based on a quasi-steady assumption and includes a special nonlinear element to account for certain aspects of the oscillator switching mechanism in addition to the traditional fluid resistance, capacitance, and inductance. A new technique for modeling a junction in a fluid duct network is also presented. Unlike previous studies which made use of empirical experimental data or analytical assumptions to estimate the fluid element parameter values and form of the nonlinearity, the current method utilizes steady, computational fluid dynamic techniques to evaluate the parameters and nonlinearity which cannot be accurately determined analytically. A simplification of the model is also used to establish the criteria for oscillations to exist. The transient solution of the model equations is then shown to give good quantitative agreement with previous experimental values of the oscillation frequency and amplitude. The model is also capable of predicting certain operational limitations and other trends in the data. Finally, the usefulness and robustness of the model are also demonstrated by showing the ease with which a parameter and design changes can be investigated.

Two-dimensional instead of three-dimensional computational fluid dynamic solutions of flow problems are quite often used in industry to facilitate short design turn-around times with varying degrees of success. A simple and robust approach for improving the accuracy of two-dimensional computational fluid dynamics solutions for problems involving internal flow passages in industrial applications is presented. The technique utilizes an approximation to the shearing stresses that act in the fully three-dimensional case but are ignored in the traditional two-dimensional approximation. Although the technique does not fully account for all the three-dimensional effects in such flows, it gives a reasonable estimate of the operation of devices with internal flows, even those involving transients. The usefulness and accuracy of the method are demonstrated through the application of the method to predict the performance of a supersonic fluidic oscillator for industrial design purposes. This brief provides industrial designers with a simple and robust tool for improving the accuracy of their computational fluid dynamic simulations.