الهدف الأساسي للألواح الكهروضوئية هو توليد الكهرباء ، وتعتمد كفاءة هذه العملية على درجة حرارة سطح تشغيل اللوحة. تؤدي درجات الحرارة المنخفضة إلى أداء أعلى ، مما يجعل من الضروري الحفاظ على الخلية الكهروضوئية باردة قدر الإمكان. يمكن تحقيق ذلك من خلال نظام التبريد ، الذي لا يعزز الكفاءة الكهربائية للوحدة الكهروضوئية فحسب ، بل يقلل أيضًا من معدل تدهورها بمرور الوقت ، وبالتالي يطيل من عمرها. بالإضافة إلى ذلك ، يمكن استخدام الحرارة الزائدة التي يتم إزالتها بواسطة نظام التبريد في العديد من التطبيقات. هناك العديد من تقنيات التبريد المتاحة ، بما في ذلك استخدام الهواء أو الماء كسوائل عمل ، مع الحركة الناتجة عن دوران الماء ، أو مبادل حرارة الماء القسري ، أو رش الماء ، أو المروحة. تقدم هذه الورقة مراجعة للأدبيات ذات الصلة حول التبريد النشط للتنظيم الحراري وتعزيز الكفاءة الكهربائية للوحدات الكهروضوئية. أظهرت الأبحاث التي أجريت في هذا المجال أن هذه التقنيات قد تم تطبيقها بنجاح لتحسين كفاءة الخلايا الكهروضوئية في ظل ظروف مختلفة.

To optimize a vertical flash tank separator, the characteristics of the flow entering the separator are required to be known. A flash tank separator improves the performance of a refrigeration cycle by separating the liquid from liquid-gas flow and providing the evaporator with only liquid refrigerant. This technique improves the effective area and enhances the heat transfer coefficient in the evaporator. This paper investigates the influence of the inlet operating conditions to an expansion device, on the adiabatic two-phase flow development in a horizontal pipe downstream from the expansion device. This work also compares three dimensional numerical simulations and experimental observations for the two-phase flow development after the expansion device in the horizontal pipe. A general trend of the two-phase flow after the expansion device was gradually developed and the expansion length was identified at less than 200 mm from the inlet. The two-phase flow behaviour was recorded using a digital camera recording the flow behaviour at the upstream and downstream of the horizontal tube. The results revealed that an increase of the mass flow rate causes an increase in the void fraction and a reduction in the slip ratio in the developed region. The simulations underestimate the expansion length and the mean difference between the experimental data and the numerical results is 8 %.

To improve the performance of vapor compression refrigeration systems that use vertical gravitational flash tank separators, the liquid separation efficiency of the vertical gravitational flash tank separator requires to be approved. To approach this improvement, the two-phase flow development and its behavior after the expansion device need to be investigated and predicted. For thus, this paper presents a three-dimensional computational investigation of the two-phase flow development of R134a after the expansion device in a horizontal pipe. Computational Fluid Dynamic (CFD) was used to predict the two-phase development and its behavior in the horizontal pipe. ANSYS 16.2 program was used to generates the geometry of the three-dimensional horizontal pipe of 2 meters long and 25 mm inner diameter. The hexahedral mesh was generated and it is assessed to obtain the optimum mesh size and number. Eulerian-Eulerian two-phase model was used with k-ɛ turbulence model. R134a was used as a working fluid in the horizontal pipe utilizing four different inlet diameters: 12, 12.5, 25, and 50.0 mm. Mass flux and vapor quality have been changed from 288 to 447 kg/m2.s and from 10 to 20% respectively. Results were validated against experimental results from the literature and revealed that the separation region length is affected by the initial phase velocities, inlet vapor quality, and inlet tube diameter. An empirical correlation to predict the expansion region length is proposed as a function of Froude, Webber, and Lockhart-Martinelli numbers.

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Heat pipes are crucial in various industrial applications owing to their superior heat transfer properties and their improvement of thermal management systems. This work introduces a two-dimensional Computational Fluid Dynamics (CFD) simulation to examine the temperature distribution and phase change processes occurring during evaporation in a heat pipe. ANSYS Fluent is employed to create the 2D heat pipe shape and produce an optimal computational mesh. A k-ɛ turbulence model is utilized to characterize fluid flow behavior, and nanorefrigerant (Al2O3/R11) is designated as the working fluid. Simulation results indicate a substantial temperature differential in the evaporator portion, as well as the impact of heat flow and wick construction on thermal resistance. The CFD results offer significant insights for optimizing heat pipe design and a comprehensive comprehension of the evaporation process, which is a consequence of phase change.