Suchergebnisse

It has been found out that heat exchangers with longitudinal grooves produce better heat transfer than those without longitudinal grooves. However, up to now, there have been few investigations and applications of longitudinal grooves in relation to heat transfer associated with friction from the annulus of a heat exchanger. The present investigation examined the effects of longitudinal grooves in a double pipe heat exchanger on the characteristics of heat transfer and friction. Longitudinal rectangular grooves were carved into the outer side of a tube at a specified depth (t) and width (l). The effect of the number of longitudinal grooves, Reynolds number (Re), on the thermal and hydraulic performance was evaluated based on the heat exchanger experimental data. A total of four pipes were used: one pipe with 2 grooves, one pipe with 4 grooves, one pipe with 6 grooves and one pipe with 8 grooves. Water, hot and cold, was used as the working fluid. The test was performed with the cold water as the working fluid, with the Reynolds number from about 33 000 to 46 000 in a counter-flow scheme. The result showed that the number of grooves improved the heat transfer and caused a pressure drop. The increase in heat transfer ranged from 1.05 to 1.15, and the pressure loss of the system reached almost 30% as compared with the smooth annulus, the annulus with no groove. The installation of longitudinal grooves in a heat exchanger system enhanced the process of the heat flow through the boundary but provided a compensation for the pressure loss, which was correlated with the friction and pumping power.

The project ChillOUT: Smart Social Spaces Creating Connected Green Places is a partnership between the University of New South Wales, Georges River Council, Street Furniture Australia, and the University of Sydney. It is underpinned by a strong philosophical orientation towards supporting people + place + healthy urban living through smart technology. The ChillOUT project aims to improve the use and amenity of public spaces within the Georges River Local Government Area (LGA). The project involves designing, producing, and testing smart open-air community spaces known as 'ChillOUT Hubs.' These multi-functional Hubs are fully IT-enabled, with smart furniture, solar power, charging points, and environmental sensors (which measure and monitor the microclimate, utility use, and use of the space). Ultimately, the Hubs will increase community connectivity, enable knowledge exchange, and provide flexible spaces for work and play.

This Final Report distils the key strategic learning arising from Design in Action – an Arts & Humanities Research Council Knowledge Exchange Hub for the Creative Economy (2012-16). The report draws on reflective evidence from the key participants, economic impacts arising from the interventions in the chosen field of study and case studies arising from four years of diverse practice. DiA has spent four years making sense of its own agency in a complex environment of knowledge exchange, HEIs, economic development agencies and government policy. These reflections and recommendations arise from this work rather than through exhaustive power and ecosystem mapping.

2010/2011 ; Since from the first Industrial Revolution, energy supply, which feeds human activities, has been characterized by consumption of fossil fuels such as coal, crude oil and gas. This supply model is heavely affected by a dramatic limitation, taht is the idea of feeding an infinite system (such as the human activities energy demand) with a finite (in terms of time) source - fossil fuels. Although this issue was already forecast in the early decades of the last century (e.g. G. Ciamician in The photochemistry of the Future, during The Ninth International Congress of Applied Chemistry - New York), it has been largely neglected until the first oil crisis in the 70s, when public eye become aware of the (social) issue coming from the oil dependence. The exponential growth of Earth population and the consequent increase of energy demand and the environmental and pollution issues that characterized last decades leaded large part of scientific and (marginally) politic community to focusing its endeavours to research of more efficient way of exploiting renewable sources and to the fillip of their usage. The main drawback, which affects the usage of renewable energies, is that the supply, whether it comes from the earth or the sun, is never constant. Day turns to night, winds die down and the geothermal heat from the crust of the earth, although seemingly constant, will eventually diminish. The capability of storing energy and release it on demand, therefore, plays a crucial role in the possibility of exploiting renewable energies. The main target of this PhD study is investigation and design of devices capable of collecting thermal energy. According to the idea of gathering the largest quantity of energy in the most efficient way, as storage strategies it has been decided to adopt the latent heat thermal storage method. Suitable materials for accomplishing this task are Phase Change Materials (PCMs); they are a class of materials capable of collecting and releasing a large amount of energy during melting and freezing process at a temperature that may be useful for anthropic activities, such as air heating&cooling, domestic hot water production, industrial processes and energy production. In this thesis in particular, the existence of a convergence point between the possibility to adopt nano-enhanced material into largely used devices (heat exchangers, boilers etc.) is explored. This research has been, therefore, performed focusing mainly onto two different aspects: the possibility of improving thermal properties (melting enthalpy) of PCMs by addiction of nano-enhancer materials and on the other hand design and development of systems which imply the usage of PCMs, eventually nano-doped. The structure of this thesis reflects the division of topics and every part represents one of these task: * in the first part, Phase Change Materials a general overview on the state of art of PCMs is presented. A brief description of strategies for thermal storage is discussed and a dissertation on different typologies of PCMs, main advantages and disadvantages coming from their usage is given. The discussion than continues analysing possible ways of modelling the thermal behaviour during melting or freezing process. Both the analytical and numerical approaches are treated; * in the second part, Nanotechnology and Phase Change Materials, dissertation on thermal variations induced by inclusion of carbon nano tubes is carried out. After a snapshot on the state of the art in the field of nano-doping of PCMs, procedures and results of four commercially available paraffin waxes doped with CNTs have been discussed; * in the third part, Design and Phase Change Materials, devices which exploit PCMs have been designed and (numerically) optimized. A panel heat exchanger, capable to accomplish requirements of modularity and short time heat release has been numerically studied and optimized by genetic algorithm; the possibility of using a nano-enhanced material has been explored. Then, a system for avoiding ice formation on pavement surface during winter time has been developed. PCM elements (pipes) embedded into asphalt concrete of road pavement have been modelled using a commercial FE code. 1D and 2D models have been used and coupled with weather data collected in Trieste during the first week of January 2009; * in the last part, Conclusions, final remarks and further developments are discussed. ; XXIV Ciclo ; 1982

The preliminary findings of a comparative study of heat transfer rate and pressure drop between conventional staggered flow and double cross flow heat exchanger is reported. Excepting for the tube arrangements, the shell and tube dimensions, materials and inlet conditions are retained the same for the two configurations. While in the conventional arrangement, adjacent rows of tubes are normal only to the fluid flow in the shell, in the double cross-flow arrangement, they are normal to both fluid flow direction in the shell as well as to each other. Shell dimensions are 100 cm × 20 cm × 20 cm and tube outside and inside diameters are 1 cm and 0.8 cm. The shell and tube materials are steel and copper. Water and air were considered as tube and shell side fluids respectively, with an overall arrangement of parallel flow. The tube flow Reynolds number was fixed at 2200 and the shell flow Reynolds number was varied from 20 to 120 in the laminar regime and 360 to 600 in the turbulent zone. The study reveals that the proposed configuration gives a maximum increase of about 27 per cent in the heat transfer rate per unit pressure drop over the conventional one.