Heat transfer and pressure drop characteristics of a plate heat exchanger using water based Al2O3 nanofluid for 30° and 60° chevron angles

Nanofluid is a new class of engineering fluid that has good heat transfer characteristics which is essential to increase the heat transfer performance in various engineering applications such as heat exchangers and cooling of electronics. In this study, experiments were conducted to compare the heat transfer performance and pressure drop characteristics in a plate heat exchanger (PHE) for 30° and 60° chevron angles using water based Al2O3 nanofluid at the concentrations from 0 to 0.5 vol.% for different Reynolds numbers. The thermo-physical properties has been determined and presented in this paper. At 0.5 vol% concentration, the maximum heat transfer coefficient, the overall heat transfer coefficient and the heat transfer rate for 60° chevron angle have attained a higher percentage of 15.14%, 7.8% and 15.4%, respectively in comparison with the base fluid. Consequently, when the volume concentration or Reynolds number increases, the heat transfer coefficient and the overall heat transfer coefficient as well as the heat transfer rate of the PHE (Plate Heat Exchangers) increases respectively. Similarly, the pressure drop increases with the volume concentration. 60° chevron angle showed better performance in comparison with 30° chevron angle

Energy, economic, and environmental analysis of a flat-plate solar collector operated with SiO2 nanofluid

To overcome the environmental impact and declining source of fossil fuels, renewable energy sources need to meet the increasing demand of energy. Solar thermal energy is clean and infinite, suitable to be a good replacement for fossil fuel. However, the current solar technology is still expensive and low in efficiency. One of the effective ways of increasing the efficiency of solar collector is to utilize high thermal conductivity fluid known as nanofluid. This research analyzes the impact on the performance, fluid flow, heat transfer, economic, and environment of a flat-plate solar thermal collector by using silicon dioxide nanofluid as absorbing medium. The analysis is based on different volume flow rates and varying nanoparticles volume fractions. The study has indicated that nanofluids containing small amount of nanoparticles have higher heat transfer coefficient and also higher energy and exergy efficiency than base fluids. The measured viscosity of nanofluids is higher than water but it gives negligible effect on pressure drop and pumping power. Using SiO2 nanofluid in solar collector could also save 280 MJ more embodied energy, offsetting 170 kg less CO2 emissions and having a faster payback period of 0.12 years compared to conventional water-based solar collectors

building thermal exergy analysis

The energy and environmental impacts due to energy consumption in the building sector are one of the main topics in the global energy field. A building is an energy system that uses energy sources in order to maintain its functionality and to ensure thermal indoor comfort for its occupants. Exergy analysis is a way to assess the impact of an energy system on the environment. This chapter introduces a model able to describe the interaction between a building and its surroundings from an exergetic point of view. The building is considered as a so-called black box, evaluating the exergy of overall energy and matter fluxes that cross the system boundaries. In this way it is possible to evaluate the exergy balance of the system and particularly the destroyed exergy. The exergy destruction percentage can be understood as a building environmental impact indicator. To illustrate the model and its operating suitability, an existing building was analyzed using the transient simulation software Trnsys. The modeling results show that about 95 % of the exergy used from the building is destroyed and that about 5 % is lost (transferred to the surroundings). This means that this building has very high impact. The model can be applied to assess the effectiveness of different building energy retrofit strategies. Through Trnsys modeling some conventional and advanced retrofit strategies, as well as on-site renewable energy utilization, are analyzed. The chapter presents the main analysis results, showing which of these strategies are able to reduce the building's exergy demand and, hence, the building's impact

Transparent soil to model thermal processes: An energy pile example

Managing energy resources is fast becoming a crucial issue of the 21st century, with groundbased heat exchange energy structures targeted as a viable means of reducing carbon emissions associated with regulating building temperatures. Limited information exists about the thermo-dynamic interactions of geothermal structures and soil owing to the practical constraints of placing measurement sensors in proximity to foundations; hence, questions remain about their long-term performance and interaction mechanics. An alternative experimental method using transparent soil and digital image analysis was proposed to visualize heat flow in soil. Advocating the loss of optical clarity as a beneficial attribute of transparent soil, this paper explored the hypothesis that temperature change will alter its refractive index and therefore progressively reduce its transparency, becoming more opaque. The development of the experimental methodology was discussed and a relationship between pixel intensity and soil temperature was defined and verified. This relationship was applied to an energy pile example to demonstrate heat flow in soil. The heating zone of influence was observed to extend to a radial distance of 1.5 pile diameters and was differentiated by a visual thermal gradient propagating from the pile. The successful implementation of this technique provided a new paradigm for transparent soil to potentially contribute to the understanding of thermo-dynamic processes in soil

The integration of social concerns into electricity power planning : a combined delphi and AHP approach

The increasing acceptance of the principle of sustainable development has been a major driving force towards new approaches to energy planning. This is a complex process involving multiple and conflicting objectives, in which many agents were able to influence decisions. The integration of environmental, social and economic issues in decision making, although fundamental, is not an easy task, and tradeoffsmust be made. The increasing importance of social aspects adds additional complexity to the traditional models that must now deal with variables recognizably difficult to measure in a quantitative scale. This study explores the issue of the social impact, as a fundamental aspect of the electricity planning process, aiming to give a measurable interpretation of the expected social impact of future electricity scenarios. A structured methodology, based on a combination of the Analytic Hierarchy Process and Delphi process, is proposed. The methodology is applied for the social evaluation of future electricity scenarios in Portugal, resulting in the elicitation and assignment of average social impact values for these scenarios. The proposed tool offers guidance to decision makers and presents a clear path to explicitl

A method of strategic evaluation of energy performance of Building Integrated Photovoltaic in the urban context

This paper presents an integrated bottom-up approach aimed at helping those dealing with strategical analysis of installation of Building Integrated Photo Voltaic (BIPV) to estimate the electricity production potential along with the energy needs of urban buildings at the district scale. On the demand side, hourly energy profiles are generated using dynamic building simulation taking into account actual urban morphologies. On the supply side, electricity generated from the system is predicted considering both the direct and indirect components of solar radiation as well as local climate variables. Python-based Algorithm editor Grasshopper is used to interlink four types of modelling and simulation tools as 1) generation of 3-D model, 2) solar radiation analysis, 3) formatting weather files (TMY data set) and 4) dynamic energy demand. The method has been demonstrated for a cluster of 20 buildings located in the Yasar University in Izmir (Turkey), for which it is found the BIPV system could achieve an annual renewable share of 23%, in line with the Renewable Energy Directive target of 20%. Quantitatively-compared demand and supply information at hourly time step shows that only some energy needs can be met by BIPV, so there is a need for an appropriate matching strategy to better exploit the renewable energy potential

Modeling of sectoral energy and exergy utilization

WOS: 000230457500001For conventional energy technologies, energy and exergy analyses have been performed and have yielded useful results. Besides this, for advanced energy technologies, the use of energy and exergy analyses can be expected to provide meaningful insights into performance that will assist in achieving optimal designs. In this regard, this study describes the modeling and analysis of sectoral energy and exergy utilization. The sectors considered are subgrouped into four main sectors, namely, utility, industrial, commercial-residential and transportation. The modeling presented here is expected to assist in the simulation and optimization activities and also in the planned studies towards increasing energy efficiencies in the sectors studied