Xiaojun Li

Bio: Xiaojun Li is an academic researcher from Zhejiang Sci-Tech University. The author has contributed to research in topics: Centrifugal pump & Impeller. The author has an hindex of 17, co-authored 57 publications receiving 758 citations. Previous affiliations of Xiaojun Li include Jiangsu University.

Entropy generation analysis for the cavitating head-drop characteristic of a centrifugal pump:

Abstract: Cavitation is a challenging flow abnormality that leads to undesirable effects on the hydraulic behaviour of centrifugal pumps. This study analyses the cavitating flow at a normal flow rate using t...

Experimental and numerical investigations of head-flow curve instability of a single-stage centrifugal pump with volute casing

Abstract: Unstable or flat head-flow curves can cause problems in parallel operations or in flat systems. Despite the considerable efforts that have been devoted to the study of head-flow curve instability in single-stage centrifugal pumps with volute casing, the cause of such phenomenon is not sufficiently understood. In this study, we investigated the variation of hydraulic losses based on the relationship between velocity distribution and entropy generation fields. Steady-state and unsteady simulations were obtained for a pump with an impeller outlet diameter of 174 mm, and the unsteady results are more coincided with the experiments. Results showed that the losses mainly focused on the blade suction surface and volute tongue, as well as in the region of the volute discharge at high flow rates. The entropy generation rate of the pump casing at partial flow rates changed slightly with a decrease in flow rate, whereas the energy losses in the impeller increased steeply when the flow rate dropped to 35 m3/h (the de...

The growth of vapor bubbles in superheated liquids. report no. 26-6

Abstract: The growth of a vapor bubble in a superheated liquid is controlled by three factors: the inertia of the liquid, the surface tension, and the vapor pressure. As the bubble grows, evaporation takes place at the bubble boundary, and the temperature and vapor pressure in the bubble are thereby decreased. The heat inflow requirement of evaporation, however, depends on the rate of bubble growth, so that the dynamic problem is linked with a heat diffusion problem. Since the heat diffusion problem has been solved, a quantitative formulation of the dynamic problem can be given. A solution for the radius of the vapor bubble as a function of time is obtained which is valid for sufficiently large radius. This asymptotic solution covers the range of physical interest since the radius at which it becomes valid is near the lower limit of experimental observation. It shows the strong effect of heat diffusion on the rate of bubble growth. Comparison of the predicted radius‐time behavior is made with experimental observations in superheated water, and very good agreement is found.

A state of art review and future viewpoint on advance cooling techniques for Lithium–ion battery system of electric vehicles

Abstract: Electric Vehicles (EVs) have emerged as most promising means of transport owing to the low operational costs, high speed, and energy-efficient battery technologies, where battery thermal management system (BTMS) is possibly the most crucial element of an EV. During the charging/discharging mode of EVs, a major focused area for the researcher is to maintain the optimal working temperature range of the batteries and reduce both the maximum temperature and temperature difference. Suitable and effective cooling methods can significantly reduce the adverse effect of the high surface temperature of battery cells and efficiently augments the battery thermal efficiency, improves the safety of EVs, and increase the service life. In this context, this work presents a detailed state of the art review of different BTMS technologies, including natural and forced air-cooling techniques, direct and indirect liquid cooling methods, and cooling by heat pipes. It is found that the air-cooled BTMS possesses advantageous features such as safe, consistent, and simple design, but the lower heat capacity and thermal efficiency of the air as a cooling medium restricts its application to a low capacity battery. This leads to employment of forced air-cooled BTMS under high charging/discharging rate, in which air flows through the channels inside the battery packs to provide the optimum cooling. Liquid-cooled BTMS is also emerging as one of the most promising cooling technologies, which requires attention to the sealing cover during the design stage to avoid leakages. The integration of metal plates with the mini channel can effectively improve the cooling performance, but the weight of the system is a major concern. Liquid metals, nanofluids, and boiling liquids are considered as the most prominent battery cooling methods owing to their higher thermal conductivity. The advancement in hybrid cooling using fins, nanofluids, PCM along with micro channels-based cooling will significantly improve the battery performance under high charging/discharging rate and attention should be given to compact design with a cheaper cost.