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

Experimental and numerical studies to assess the energy performance of naturally ventilated PV façade systems

This paper presents a holistic approach to assess the energy performance of a naturally ventilated PV façade system. A rigorous combined experimental and numerical approach is established. The real energy performance of the system has been evaluated through a long-term high resolution monitoring of a typical ventilated PV façade system. A numerical model based on TRaNsient SYstem Simulation (TRNSYS) package was developed to assess the thermal and energy performance of the system, which has been verified by a series of statistical analysis using the data collected from the experiment. The validated model was then used to assess the energy and thermal performance of a 7.4 kWp prototype ventilated PV façade system in Izmir, Turkey. The results of this study demonstrated that ventilation in the air cavity of the PV façade system could significantly improve energy performance of the system even in a southeast facing façades. The quantitative analysis provides useful guidance to the system designers for the improvement of energy efficiency of the PV facade system

Performance evaluation of a building integrated photovoltaic (BIPV) system combined with a wastewater source heat pump (WWSHP) system

This paper deals with both energetic and exergetic performance assessments of two combined systems as a whole. The first one is a Building Integrated Photovoltaic (BIPV) system while the second one is a wastewater (WW) Source Heat Pump (WWSHP) system. Both systems were installed at Yasar University, Izmir, Turkey within the framework of EU/FP7 and the Scientific and Technological Research Council of Turkey (TUBITAK) funded projects, respectively. The BIPV system was commissioned on 8 February 2016 and has been successfully operated since then while the WWSHP system was put into operation in October 2014. The BIPV system has a total peak power of 7.44 kW and consists of a total of 48 Crystalline Silicon (c-Si) modules with a gap of 150 mm between the modules and the wall, and a peak power per PV unit of 155 Wp. The WWSHP system consists of three main sub- systems, namely (i) a WW system, (ii) a WWSHP, and (iii) an end user system. Two systems considered have been separately operated while the measured values obtained from both systems have been recorded for performance assessment purposes. In this study, a combined system was conceptually formed and the performance of the whole system was evaluated using actual operational data and some assumptions made. Exergy efficiency values for the WWSHP system and the whole system were determined to be 72.23% and 64.98% on product/fuel basis, while their functional exergy efficiencies are obtained to be 20.93% and 11.82%, respectively. It may be concluded that the methodology presented here will be very beneficial to those dealing with the design and performance analysis and evaluation of BIPV and WWHP systems

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

Advanced Exergy Analysis of Waste-Based District Heating Options through Case Studies

The heating of the buildings, together with domestic hot water generation, is responsible for half of the total generated heating energy, which consumes half of the final energy demand. Meanwhile, district heating systems are a powerful option to meet this demand, with their significant potential and the experience accumulated over many years. The work described here deals with the conventional and advanced exergy performance assessments of the district heating system, using four different waste heat sources by the exhaust gas potentials of the selected plants (municipal solid waste cogeneration, thermal power, wastewater treatment, and cement production), with the real-time data group based on numerical investigations. The simulated results based on conventional exergy analysis revealed that the priority should be given to heat exchanger (HE)-I, with exergy efficiency values from 0.39 to 0.58, followed by HE-II and the pump with those from 0.48 to 0.78 and from 0.81 to 0.82, respectively. On the other hand, the simulated results based on advanced exergy analysis indicated that the exergy destruction was mostly avoidable for the pump (78.32–78.56%) and mostly unavoidable for the heat exchangers (66.61–97.13%). Meanwhile, the exergy destruction was determined to be mainly originated from the component itself (endogenous), for the pump (97.50–99.45%) and heat exchangers (69.80–91.97%). When the real-time implementation was considered, the functional exergy efficiency of the entire system was obtained to be linearly and inversely proportional to the pipeline length and the average ambient temperature, respectively

Application of net zero extended exergy buildings concept for sustainable buildings analysis

[EN] Different Zero-Energy Building (ZEB)-related definitions considering its four main dimensions, such as zero energy, zero carbon, zero exergy and zero cost, have been proposed by different investigators. Among these, exergy-based definitions are relatively low in numbers. In this regard, the main objective of this present study is to propose net zero extended exergy buildings as a new concept, which combines extended exergy and net zero exergy building concepts and is a measure of the exergetic footprint. This concept setups a balance between extended exergy accounting of electricity from the grid and electricity generated in building. The proposed methodology is applied to a building available in the literature for heating and cooling seasons. Results show that 450Wp peak power and 44.181 kWh electrical energy must be obtained for meeting the electricity demand of the building. Another novel result is that the extended exergy accounting of the electricity generated by PV panels is bigger than the extended exergy of the electricity taken from the gird meaning that exergetic footprint of the electricity generated by PV panels is bigger. However, this result must be interpreted for the whole life time of the system.S

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

Advanced exergy analysis of waste‐based district heating options through case studies

The heating of the buildings, together with domestic hot water generation, is responsible for half of the total generated heating energy, which consumes half of the final energy demand. Meanwhile, district heating systems are a powerful option to meet this demand, with their significant potential and the experience accumulated over many years. The work described here deals with the conventional and advanced exergy performance assessments of the district heating system, using four different waste heat sources by the exhaust gas potentials of the selected plants (munici-pal solid waste cogeneration, thermal power, wastewater treatment, and cement production), with the real‐time data group based on numerical investigations. The simulated results based on conventional exergy analysis revealed that the priority should be given to heat exchanger (HE)‐I, with ex-ergy efficiency values from 0.39 to 0.58, followed by HE‐II and the pump with those from 0.48 to 0.78 and from 0.81 to 0.82, respectively. On the other hand, the simulated results based on advanced exergy analysis indicated that the exergy destruction was mostly avoidable for the pump (78.32– 78.56%) and mostly unavoidable for the heat exchangers (66.61–97.13%). Meanwhile, the exergy destruction was determined to be mainly originated from the component itself (endogenous), for the pump (97.50–99.45%) and heat exchangers (69.80–91.97%). When the real‐time implementation was considered, the functional exergy efficiency of the entire system was obtained to be linearly and inversely proportional to the pipeline length and the average ambient temperature, respec-tively