Bi-fluid cooling effect on electrical characteristics of flexible photovoltaic panel

A photovoltaic (PV) system integrated with a bi-fluid cooling mechanism, which is known as photovoltaic thermal (PVT) system, was investigated. The electrical characteristics of flexible solar panel were evaluated for PV and PV with bi-fluid (air and water) cooling system. The integration of monocrystalline flexible solar panel into both systems was tested under a fixed solar radiation of 800 W/m2. A total of 0.04–0.10 kg/s of air flow was utilised in PV with cooling system with a fixed water mass flow rate of 0.025 kg/s. The efficiencies of flexible panel for PV and PV with cooling system were explored. For PV with bi-fluid flow, the highest obtained efficiency of module was 15.95% when 0.08 kg/s of air and 0.025 kg/s of water were allowed to flow through the cooling system. Compared with PV without cooling mechanism, the highest efficiency of module was 13.35% under same solar radiation. Current–voltage and power graphs were also plotted to present the electrical characteristics (current, voltage and power) generated by both systems.

COMPARATIVE ANALYSIS OF FLUID COOLING SYSTEMS IN MOTORIZED SPINDLES

This paper analyzes geometrical approaches to optimize the fluid cooling circulation of motorized spindles. The spindle fluid cooling’s effectiveness, efficiency and influence on the machine’s precision are analyzed through observations of the stator temperature, pressure drop and thermal asymmetry, respectively. The observation is based on a validated coupled thermal/fluid mechanical simulation model. The widely used helix and meander shape stator cooling sleeves are primarily investigated. Additionally, a so-called S-meander shape was developed, which combines the advantages of the formerly mentioned sleeves. In order to understand the nonlinear thermal interactions properly, width and height of the cooling channels were varied separately and simultaneously. While keeping the flow rate identical, the average stator temperature could be decreased by 2.3 K solely with geometrical optimizations. Interestingly, the motor temperature is not continuously decreased by raising the fluid velocity through a reduction of the cooling channels size. For the helix and the S-meander, the temperature actually increases after passing a certain geometrical sweet spot. Additionally, this optimum is different for the helix, meander and S-meander cooling sleeve. The results imply that the geometrical optimization of fluid cooling channels in motorized spindles has a significant potential. Furthermore, the developed cooling sleeves are trans-ferable to any electric motor with fluid cooling.

Computer 2D modelling of a micro-grip fluid cooling system

Представлено компьютерное численное моделирование системы жидкостного охлаждения камеры микрозахвата. Построены математические модели течения жидкости, переноса тепла жидкостью, теплообмена между жидкостью и радиатором, теплообмена между радиатором и элементом Пельтье. Определено влияние геометрических и физических параметров камеры микрозахвата на эффективность системы охлаждения, а также найдена зависимость максимальной температуры, установившейся на радиаторе, от скорости течения охлаждающей жидкости и коэффициента теплопередачи между радиатором и жидкостью для стационарного течения. Проведено исследование влияния нестационарного течения жидкости на колебания температуры радиатора. На основе результатов численного моделирования предложены простые аналитические формулы, которые можно использовать в программном обеспечении системы управления микрозахватом Numerical simulation of a micro-grip chamber fluid cooling system is presented. The mathematical models for mass and heat transfer in a fluid, heat exchange between the fluid and the radiator as well as the heat exchange between the radiator and the Peltier element are constructed in a variational form. The equations of hydrodynamics and heat equations were simulated by the finite element method in the FreeFem++ software. The influence of the geometric and physical parameters of the cooling system chamber on the efficiency of the device is determined. It is shown that as the heat transfer coefficient between the radiator and the fluid and the velocity of the coolant increases, the maximum steady-state temperature on the radiator nonlinearly decreases with saturation. When flow of coolant oscillates then the temperature on the radiator so does with the flow frequency. As the flow frequency increases, the amplitude of temperature fluctuations decreases. The increasing amplitude of flow oscillations leads to the amplification of the temperature amplitude. Using orthogonal central compositional method, the influence of the parameters (heat transfer coefficient, fluid velocity) on the efficiency of the cooling system is found, and the contribution of pairwise interaction is determined. Based on the results of numerical modelling, simple analytical formulas are proposed that can be used in the software module of the micro-grip cooling control system.

Fluid Convection Models for Low-Temperature Grinding and Effect of Fluid Warming

The paper considers fluid convection in low-temperature grinding. Fluid cooling often predominates over all other forms of heat dispersion in the grinding zone particularly in low-temperature grinding. Experimental values of convection heat transfer coefficient (CHTC) up to and in excess of 200,000 W/m2K have been found by various researchers both for water-based emulsions and in one case for mineral oils employed in high wheel-speed grinding. Several convection models have been developed in recent years for the prediction of CHTCs in low-temperature grinding. This paper reviews advances in convection modeling and reconsiders the basic assumptions implied. A proposal is made for improved estimation for highly churned flow assuming a degree of fluid warming. Predicted coefficients are compared with measured values.