Numerical Assessment of Heat Transfer and Entropy Generation of a Porous Metal Heat Sink for Electronic Cooling Applications

In the present study, the thermal performance of an electronic equipment cooling system is investigated. The heat sink used in the current cooling system consists of a porous channel with a rectangular cross-section that is assumed to be connected directly to the hot surface of an electronic device. In this modeling, a fully developed flow assumption is used. The Darcy–Brinkman model was used to determine the fluid flow field. Since using the local thermal equilibrium (LTE) model may provide results affected by the error in metal foams, in the present research, an attempt has first been made to examine the validity range of this model. The local thermal non-equilibrium (LTNE) model taking into account the viscous dissipation effect was then used to determine the temperature field. To validate the numerical solution, the computed results were compared with other studies, and an acceptable agreement was observed. Analysis of the temperature field shows that if the fluid–solid-phase thermal conductivity ratio is 1 or the Biot number has a large value, the difference between the temperature of the solid phase and the fluid phase decreases. Moreover, the effect of important hydrodynamic parameters and the porous medium characteristics on the field of hydrodynamic, heat, and entropy generation was studied. Velocity field analysis shows that increasing the pore density and reducing the porosity cause an increase in the shear stress on the walls. By analyzing the entropy generation, it can be found that the irreversibility of heat transfer has a significant contribution to the total irreversibility, leading to a Bejan number close to 1. As a guideline for the design of a porous metal heat sink for electronic equipment, the use of porous media with low porosity reduces the total thermal resistance and improves heat transfer, reducing the total irreversibility and the Bejan number. Moreover, the increasing of pore density increases the specific porous surface; consequently, it reduces the total irreversibility and Bejan number and improves the heat transfer

Контрастивний аспекту вивченні фразеологічних одиниць із компонентом вогонь (на матеріалі української та англійської мов)

(uk) У статті проведено контрастивный аналіз фразеологізмів із компонентом «вогонь» в українській та англійській мовах, а також визначено, що він відіграє першочергову роль у формуванні фразеологічного значення, оскільки виступає у ролі мотивуючого компонента семантики аналізованих фразеологізмів. У всіх досліджуваних одиницях української та англійської мов компонент «вогонь» сигналізує сему «смерть», іноді — «очищення», «витримка».(en) The article deals with the contrastive analysis of phraseological units with the component ‘fire’ in Ukrainian and English. It is found out that it plays a primary role in shaping the idiomatic meaning as a motivating component of semantics of the analyzed idioms. In all Ukrainian and English units with the component ‘fire’ it implies the seme ‘death’, or sometimes ‘cleaning’, ‘endurance’

Comparison of structure and observance of scientific writing of nursing master students theses in Kerman & Tabriz University of Medical Sciences

Introduction: Dissertation component of university research is considered that represent the power of initiative and creativity of students . Thesis in nursing education to increase knowledge and positive vision research process in nursing students and to create clinical practice field is based on scientific evidence. Objectives: Thesis evaluation as a research document, or look for scientific and research information available is essential therefore present study assessed the structure and observing scientific writing thesis master of nursing students was conducted in Kerman University of Medical Sciences. Method: In this descriptive thesis M.sc Nursing 75 cases and 130 cases of Kerman, Tabriz, to selected randomly and in terms of general profile, structure and content were examined data by an information form and contains 14 questions and 38 questions about general characteristics of elements related to research and research methods were 16 indicators have been collected. In the analyzed data using descriptive statistics and t tests,X2, ANOVA, Mann-Whitney U and kruskal- Wallis and software 18SPSS was performed. Results: Most of the thesis investigated more Kerman and Tabriz (76, 70.2percent) of the type of descriptive studies, more than half (60, 68.5percent) were the themes Surgical Nursing. Triple points in total 16 indicators thesis studied Kerman and Tabriz to more 85/ 6 ± 10.14 and 74.7 ± 13.7from 114, the statistical difference p =0.000) was significant. And 16 fold in all criteria also significant difference (p=0.05) was observed. Most consistent in Kerman thesis in order to correct writing (86.7percent) and (58.8 percent) and lowest compliance respectively Kerman how to abstract thesis (29.3 percent) and how introduction (3.11) respectively. Total thesis of Kerman 9.1 percent and Tabriz 17.7 percent succeeded in publishing article had been. Differences between mean total score of the end of the letter based on the time period of five (p =0.000), published articles, letters from the end (p =0.000), academic degrees Supervisor (0.001) and the number of Supervisor (p= 0.002) means was significant. Conclusion: Although a total of Kerman thesis rather than structure and scientific writing were better. But the scientific evaluation of this documentation in both training center, indicate that thesis in recent years enjoy a better quality of. Growing trend of improvement course developed thesis represented hale promote scientific research and development of students and faculty members Ian universities and attention to the necessity of making use ‌ research results to promote the importance of their operations that run much and develop theses shows. Keywords: Thesis, Msc Nursing, Evaluation, Comparison, Kerman, Tabri

A review of advanced air distribution methods - theory, practice, limitations and solutions

Ventilation and air distribution methods are important for indoor thermal environments and air quality. Effective distribution of airflow for indoor built environments with the aim of simultaneously offsetting thermal and ventilation loads in an energy efficient manner has been the research focus in the past several decades. Based on airflow characteristics, ventilation methods can be categorized as fully mixed or non-uniform. Non-uniform methods can be further divided into piston, stratified and task zone ventilation. In this paper, the theory, performance, practical applications, limitations and solutions pertaining to ventilation and air distribution methods are critically reviewed. Since many ventilation methods are buoyancy driving that confines their use for heating mode, some methods suitable for heating are discussed. Furthermore, measuring and evaluating methods for ventilation and air distribution are also discussed to give a comprehensive framework of the review

Construction and Evaluation of a Controlled Active Mass (CAM) : A new cooling system design for increased thermal comfort using low exergy sources

Nowadays, office buildings often have large temperature variations during the day and building envelope acts as an energy storing mass and damp these effects and so Offices need more cooling because of internal heat sources. But we know that cooling is more expensive than heating and it uses the very good quality of energy sources (exergy). Controlled Active Mass (CAM) is new approach to absorb radiant heating and acts as a passive cooling device. It has direct cooling effect and reduces the peak load. CAM is a new cooling system design with applying the low energy sources and operates at water temperature close to room temperature and increase the efficiency of heat pumps and other systems. In this project, we calculated the transient heat transfer analysis for CAM in a very well insulated test room with façade wall, Internal heat generators (such as Manikin, Computer simulator & lighting) and ventilation. Then Polished (shiny) CAM constructed from Aluminum sheets with 0.003 m thickness. It is cube shape with 0.6 m length. This size of CAM is according to 2.5 times larger than human body volume and initial water temperature assumed near half of human body temperature. Then in order to more radiation damping (absorption) by CAM, it painted black (also based on color analysis in heat transfer calculation). Some velocity and temperature measurement have been carried out on both polished CAM and black CAM, after visualization by smoke and Infrared Camera. And more cases tested to see the effect of façade wall, IHG’s and ventilation inlet temperature. Thermal comfort measurement also have been done for finding PMV, PPD and temperature equivalent for a seated person which is doing an office job with normal closing. At the end results discussed which includes the effect of CAM in room, differences between polished CAM and black CAM and effect of main heat sources on both CAM types (Polished / Black)

INVESTIGATION OF TEMPERATURE DISTRIBUTION IN THE DISCHARGE MACHINING STEEL P20

در این مقاله توزیع حرارت در سطح قطعه کار در ضمن تخلیه الکتریکی واحد توسط نرم‏افزار Fluent شبیه سازی شد. برای این منظور از خواص ترمودینامیکی میانگین برای جنس قطعه کار و شعاع شار گرمایی با توزیع گاوسین برای منبع حرارتی و اعمال شرط مرزی جابجایی آزاد در سطح بالایی قطعه کار استفاده شد. در نهایت از روی پروفیل توزیع دما در قطعه کار استیل P20 حجم گودال بدست آمد و با داده های تجربی مقایسه شد. سیال دی الکتریک مورد بررسی کروسن انتخاب شده است. در تمامی شبیه سازی های صورت گرفته، گرمای نهان ذوب ماده در نظر گرفته شده است که باعث کاهش خطای محاسبات نرخ براده برداری شده است. مقایسه نشان داد که بر خلاف نظریات ارائه شده در مدل های پیشین، کسر انرژی منتقل شده به قطعه کار و مایع دی الکتریک با توجه به شرایط ماشین‌کاری متغیر است و با افزایش شدت جریان ورودی و مدت زمان روشنی پالس، کسر انرژی منتقل شده به قطعه کار افزایش می یابد. همچنین با استفاده از توزیع دمایی در زیر گودال ایجاد شده، به بررسی اثرات تغییرات ساختاری ایجاد شده بر روی صافی سطح پرداخته شد. با افزایش شدت جریان حجم منطقه انتقال افزایش و باعث تغییرات ساختاری و تغییر خواص ترمودینامیکی قطعه کار می شود و باعث کاهش صافی سطح قطعه کار ماشین‌کاری شده می شود

Numerical and experimental investigation of flow behavior in a confluent jet ventilation system for industrial premises

A conventional supply principle, such as rmxing or displacement ventilation, in industrial applications often results in low ventilation efficiency and high draught. A possible way to improve the ventilation efficiency in industrial premises is to implement a new type of supply system known as confluent jet ventilation. The confluent system can be described as a number of free jets issued in a plane, parallel to each other. In the proximity of the diffuser, the confluent jets behave as separate jets, but downstream the jets starts to merge with each other and eventually behave as a single jet. The main advantage of the confluent jet system is its ability to conserve momentum in an efficient way. The high level of momentum makes the ventilation system less sensitive to mechanical disturbances and buoyancy forces than displacement ventilation. This effect can be used to enhance the ventilation efficiency. The purpose of this study is to investigate both numerically and experimentally the flow behavior of a confluent jet system in the region close to the diffuser. In the present study, a diffusor consisting of 36 jets with an in-line anangement using equidistant spacing has been studied. The Reynolds number of the jet, based on the nozzle diameter, is Red= 3290. ARANS simulation using the Reynolds Stress Model (RSM) has been used to predict the mean velocity field and the tmbulence characteristics of the confluent jet configuration. The numerical simulations are compared with measurements using Particle Image Velocimetty (PIV), performed in a region extending out to a downsttream distance of 26 times the nozzle diameter. The flow behavior of the confluent jets showed good agreement with the experimental results.Ett nytt ventilationskoncept för industrilokale