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A numerical study was performed of natural laminar convective heat transfer to its concentrated triangular enclosure around a horizontal circular cylinder. The air-filled enclosure kept the inner and outer cylinders at uniform temperatures. The Boussinesq density approximation to the momentum problem and the control volume approach iteratively resolved the governing equations to explain buoyancy. CFD results show that the velocity behavior increases by increasing Ra, so the stream lines becomes more sluggish and less uniform behavior and vortices gets less circulated pattern. The rotation angle ? has significant effect on vortices, at 90o gives the higher range of velocity zones of free convection with higher range. The thermal boundary layer seems to be larger in rr=0.455 as compared with rr=0.345 and decreases by increasing ?. The larger variation of isotherms and thermal boundary layer appears at lower ? because the higher heat transfer rate occurs at higher ? and becomes maximum at 90o. Eight correlations of average Nusselt number have been deduced as a function of Rayleigh number for the taken values of aspect ratio and enclosure angles of rotation and inclination.

In this paper, the effect of multilayer screen mesh wicks and CuO nano-fluid as working fluid is investigated on the performance of heat pipe. Three heat pipes were fabricated with different layers of screen mesh wicks to improve capillary action of working fluid. Heat pipes of 350 mm length and 19.5 mm diameter were used. The different mesh configurations used in this work were 100+150 mesh, 100+2X150 mesh and 4X150 meshes. The concentration of CuO nano-fluids in the experiments was maintained at 1% by weight of water. The heat pipes are tested with water and CuO as working fluid for different heat inputs of 35W, 50W 75W, 100W and 120W. The thermal resistance and heat transfer rate were determined. It is found that the thermal resistance decreases with increase in heat input. There is increase in heat transfer rate in case of CuO nanofluid loading in ordinary water compared to distilled water as working fluid. For all orientation the maximum heat transfer through the heat pipe increased as the number of mesh layer of the wick is increased. The heat transfer rate is found to be maximum at 100 l/h mass flow rate compared to that of 150 l/h.

Refrigeration is one of the most important aspects of thermal environment engineering. The term refrigeration may be defined as the process of removing heat from a substance under controlled conditions. It also includes the process of reducing and maintaining the temperature of a body below the general temperature of its surroundings. In other words, the refrigeration means a continued extraction of heat from a body whose temperature is already below the temperature of its surrounding. There are many applications of refrigeration in our daily life. With the advancement of science and technology, the luxuries of yesterday are necessity of today. In addition, refrigeration embraces industrial refrigeration, including the processing and preservation of food, removing the heat from the substances in chemical, petroleum and petrochemical plants; and many special applications such as those in the manufacturing and construction industries. Medical industries have progressed a lot with application of refrigeration such as drugs and medicine storages, blood and skin storages etc. Refrigeration also has wide application in road, railways, marine and air transport. Refrigeration may be produced by several methods. One of these methods is vapour compression system. It is used in majority of refrigeration applications. In this method, alternately condensation and evaporation takes place. In evaporation, the refrigerant absorbs latent heat from the surrounding to be cool and cooling is accomplished by evaporation of liquid refrigerant at reduced pressure and temperature. While in condensation, it gives out its latent heat to the circulating water/air of cooler. According to the requirement, vapour compression system is further modified for better performance and control. Such systems are compound systems, cascade systems and multi evaporator systems. In many refrigeration installations, different temperature are required to be maintained at various point in the plant such as in hotels, large restaurants, institutions, industrial plants and food markets where the food products are received in large quantities and stored at different temperatures. For example, the fresh fruits, fresh vegetables, fresh cut meats, frozen products, dairy products, canned goods, bottled goods have all different conditions of temperature and humidity for storage. In such cases, each location is cooled by its own evaporator in order to obtain more satisfactory control of the condition. For these type of case, system with more than one evaporator i.e., multi evaporator system is used. Multi evaporator systems yields the higher value of coefficient of performance compared to single evaporator system meant for different temperatures. There is easy control of fluctuations in loads by controlling individual evaporator. Also saving in initial cost and space required are the additional advantages with single compressor multi evaporator systems. Considering the above advantages of multi evaporator system over single evaporator system one can easily recommend ...