Built Enviroment

An experimental setup of double pipe heat exchanger fouling test rig was built to investigate the mineral scale deposition on different heat exchanger pipe surfaces. Progressive fouling deposition on different material surfaces under the similar solution conditions were observed and analyzed. Measurable data on the progressive build-up of scale deposits, deposition rate, as well as the composition and crystal morphology of the deposits were studied after each experimental run by analyzing the deposited scale on the test pipes. In this research the artificial calcium carbonate deposit on different material surfaces is considered as it is one of the major constituents of the most scales found in heat exchanging equipment. Fouling on different smooth test pipes were investigated in the centrally located larger concentric pipe heat exchanger. Uniform flow condition near the pipe surface was maintained by constant flow rate throughout the system. The calcium carbonate deposition rates on five different metal surfaces (Stainless steel 316, brass, copper, aluminium and carbon steel) were investigated. The results illustrated an upward trend for fouling rate with time on the tested specimens. The deposition on the surfaces showed a linear growth with the enhancement of thermal conductivity of the metals. However, de-position on carbon steel metal surfaces did not follow the typical linear trend of thermal conductivity over depo-sition as its surface was altered by corrosion effects. In addition, temperature, velocity, and concentration effects on fouling deposition were investigated on the SS316 metal surface. It is noted that the fouling deposition increases with the increase of temperature and concentration due to enhanced deposition potential whereas reduces due to the increase of velocity which enhances shear stress.

Calcium sulphate is one of the major fouling that lead to serious operating problems in industries. The mitigation of calcium sulphate scaling by physical water treatment (PWT) in an operating heat exchanger using zinc and tourmaline as catalytic materials is presented in this paper. The PWT is defined as a non-chemical effective fouling retardation method which exhibits promising protection to protect the environment and maintain a green environment. Catalytic materials such as (zinc and tourmaline) are capable of tackling fouling problems. Experiments were conducted in this study to verify and evaluate the performance of the PWT method. Artificially hardened water at 300 mg L −1 was used as the cooling water for deposit analysis. The velocity of the cooling water (i.e. hard water) was varied from 0.3 to 0.8 m s −1 and the bulk temperature of the solution was maintained at 45˚C. The experimental running time was set at 10 h each step. The artificially hardened water concentration was monitored under various velocities. Complex metric titration was implemented to measure the concentration of calcium sulphate every 2 h for cases with and without PWT-treated cooling water flow. The results showed that the reduction in calcium sulphate formation for case with PWT higher compared to those without PWT. However, it was observed that the performance of the PWT decreases gradually overtime, which needs to be addressed in future work.

• Fouling resistance is enhanced by the surface thermal conductivity. • Fouling is enhanced by the heat exchanger surface temperature and concentration of the foulant in the solution. • Additive gum arabic (benign to environment) retards fouling deposition on different metal surfaces. a b s t r a c t Investigation on fouling behaviour of calcium carbonate on heat exchanger surfaces as well as mitigation of fouling are presented in this paper. By varying parameters such as concentration of the fouling solution, temperature of the heating surface, type of materials and use of additives, the fouling rate on the test specimens were observed. A set of experiments were performed by using calcium carbonate solution. Fouling rate, fouling resistances and the rate of heat transfers were determined for different heat exchanger material surfaces. Fouling resistance is enhanced by the thermal conductivity and temperature of the heat exchanging surfaces and also by the concentration of the foulant in the solution. The addition of gum arabic additive (benign to the environment) to the solution retarded the rate of deposition. The results of these investigations could be design aid for economic and enhancement of heat exchanger performance.

Fouling can be defined as adherent deposits of unwanted compounds that are formed by the precipitation of soluble salts from water and crystal growth on the surfaces of processing equipment. The deposition layer becomes an insulating layer that deteriorates the heat transfer efficiency and shortens the service life. The development of functionalized nanomaterial leads to multi-functionality, such as the ability to adsorb scaling cations with high thermal conductivity, which is very important for heat transfer applications to manage the fouling problems. The purpose of this study was to evaluate the mitigation of calcium carbonate scaling by applying EDTA-treated MWCNT-based water nanofluids on heat exchanger surfaces. A set of fouling experiments was conducted by using additive EDTA-treated MWCNT-based water nanofluids (benign to the environment) to verify the additives' retardation of the fouling rate of deposition. Fouling solution for deposit analysis was prepared by using 300 mg/L of artificially-hardened calcium carbonate solution. Also the assessment of the deposition of calcium carbonate on the heat exchanger surface with respect to the inhibition of crystal growth was conducted by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectrometry (EDS). The results showed that the formation of calcium carbonate crystals can be retarded significantly by adding MWCNT-EDTA additives to the solution.

Decoration EDTA on MWCNT surface to retard the rate of fouling. Preparation of DTPA-treated MWCNT/water nanofluid. Evaluating the mitigation of DTPA-treated MWCNT-based water nanofluids. Retarding of calcium carbonate crystals by MWCNT-DTPA additives. The effect of additive on the rate of fouling. a b s t r a c t Mineral scale deposition on heat exchanging surfaces increases the thermal resistance and reduces the operating service life. The effect is usually intensified at higher temperatures due to the inverse temperature solubility characteristics of some minerals in the cooling water. Scale formation build up when dissolved salt crystallize from solution onto the heated surface, forming an adherent deposit. It is very important for heat transfer applications to cope with the fouling problems in industry. In this present study, a set of fouling experiments was conducted to evaluate the mitigation of calcium carbonate scaling by applying DTPA-treated MWCNT-based water nanofluids on heat exchanger surfaces. Investigation of additive DTPA-treated MWCNT-based water nanofluids (benign to the environment) on fouling rate of deposition was performed. 300 mg L À1 of artificially-hardened calcium carbonate solution was prepared as a fouling solution for deposit analysis. Assessment of the deposition of calcium carbonate on the heat exchanger surface with respect to the inhibition of crystal growth was conducted by Scanning Electron Microscope (SEM). The results showed that the formation of calcium carbonate crystals can be retarded significantly by adding MWCNT-DTPA additives as inhibition in the solution.

Heat exchanger is equipment used to transfer heat from one fluid to another. It has extensive domestic and industrial applications. Extensive technical literature is available on heat exchanger design, operation and maintenance, but it is widely scattered throughout the industrial bulletins, industrial design codes and standard, technical journals, etc. The purpose of this book chapter is to consolidate into basic background and concepts design of heat exchangers, operation, cleaning and green technology maintenance on heat exchanger closely related to the industrial practices.

Water quality is a growing area of research, with more and more focus in the UK and globally on environmental issues and water quality. Current methods of monitoring environmental data such as air quality have continued to develop, spurred on by the growth of the Internet of Things. However, water quality monitoring mainly still depends on manual sample collection. This research presents the first implementation of a multi-hop underwater radio frequency sensor network using bowtie antennas combined with the 433 MHz frequency and a controlled flooding routing approach. The experimental work was conducted in the water reservoir and demonstrates the potential of multi-hop routing in underwater sensor networks to extend range to 19 meters as well as improvements on communication distances from 7 meters previously to 17 meters using radio frequency communications in an underwater environment. Simulated results show that the experimental platform used could enable the long-term deployment of an underwater wireless sensor network that used RF for periods of over a year with support for a 100 sensor node network broadcasting twice daily remaining active for 418 days or a 100 sensor node network broadcasting hourly remaining active for 406 days before any node deaths.

Lead time reduction is a key concern of many industrial buyers of capital facilities given current economic conditions. Supply chain initiatives in manufacturing settings have led owners to expect that dramatic reductions in lead time are possible in all phases of their business, including the delivery of capital materials. Further, narrowing product delivery windows and increasing pressure to be first-tomarket create significant external pressure to reduce lead time. In this paper, a case study is presented in which an owner entered the construction supply chain to procure and position key long-lead materials. The materials were held at a position in the supply chain selected to allow some flexibility for continued customization, but dramatic reduction in the time-to-site. Simulation was used as a tool to consider time-to-site tradeoffs for multiple inventory locations so as to better match the needs of the construction effort.

Agent-based Modeling and Simulation (ABMS) is a relatively new development that has found extensive use in areas such as social sciences, economics, biology, ecology etc. Can ABMS be effectively used in finding answers to complex construction systems? The focus of this paper is to provide some answers to this question. Initial experimentation is conducted to understand the advantages of using ABMS either in isolation or in combination with traditional simulation methodologies. The paper provides a summary of this experimentation, conclusions and sets the agenda for future research in this area.

To encourage sustainable development, engineers and scientists need to understand the interactions among social decision-making, development and redevelopment, land, energy and material use, and their environmental impacts. In this study, a framework that connects these interactions was proposed to guide more sustainable urban planning and construction practices. Focusing on the rapidly urbanizing setting of Phoenix, Arizona, complexity models and deterministic models were assembled as a metamodel, which is called Sustainable Futures 2100 and were used to predict land use and development, to quantify construction material demands, to analyze the life cycle environmental impacts, and to simulate future ground-level ozone formation.

This article outlines the utilization of Petri nets as a computerized process modeling and analysis tool for the study of the Edmonton Mail Processing Plant (MPP). Development of new systems or designing improvement in existing system-such as the MPP-are some of the challenges faced by decision makers and managers on a regular basis in the industry. In order to make prudent decisions, modeling and analysis of the underlying processes that constitute new or existing systems has become essential. Usually process modeling and analysis is performed by initially developing a graphical portrayal of the process and then by dynamically studying the response of the process to external and internal factors. In this article an overview of Petri net based process modeling and analysis is provided. Petri net is a formal graphical modeling tool that can be efficiently utilized as a process modeling and analysis tool because it can graphically portray and dynamically simulate a process in an integrated manner. The objective of this article is to highlight the symbolic graphic format and dynamic simulation capabilities of Petri nets. The article contributes significantly in the area of computer based decision making and provides value to practicing engineers and project managers who manage complex tasks. ᭧ (A. Sawhney) www.elsevier.com/locate/advengsoft A. Sawhney et al. / Advances in Engineering Software 30 (1999) 543-549 546 Raw Mail Cull Culled Mail Cancellation 9 7 % 3 % Ready for M L O C R & O C R Ready for rerun Rerun Culling Machine Fig. 3. Petri net model of the ''culling and cancellation'' activity. 6 5 % 3 5 % Ready f o r M L O C R Ready for OCR Processing b y M L O C R Processing by OCR 9 5 % 5 % 1 0 % 9 0 %

Traditional research in construction safety focused on accident data analysis, identification of root cause factors and safety climate modeling. These research efforts did not study the dynamic repetitive interaction among multiple root cause factors. Recently safety research focuses on developing accident causation models. These models attempt to explain how the interaction among multiple project factors gets translated into safety incidents. Agent based modeling and simulation (ABMS) is an appropriate technique to develop computational models of accidents causation because of its ability to model human factors and repetitive decentralized interactions. This paper presents a conceptual framework for developing agent based models of construction safety. The key components of the model such as construction crew, management, work environment, material and equipment related quality issues, project/process level complexities, interaction rules and adaptation have been discussed. Further the adaptation of agents in response to the safety culture has been demonstrated using a simple ABMS experiment

Contactor's expertise and performance play a significant role in successful delivery of a project. While clients strive hard to make the best decisions in selecting the right contractor for the right job, a clear understanding of the underlying attributes associated with contractors' selection in the context of achieving successful project outcomes is critical. In an attempt to understand these pre-emptive qualification criteria and their links to contractors' performance on a project, a hierarchical structural model is established. By employing the structural equation modelling technique, the model adapts a total of 29 technical attributes across five confirmatory factors namely, soundness of business and workforce (SBW), planning and control (PC), quality performance (QP), past performance (PP) and overall project success (OPS). Based on the survey data collected across medium size construction projects in Australia, the results of the model confirmed that technical planning and controlling expertise of contractor is key in achieving success on projects. With a clear understanding of the significance of these factors in the context of contractors' performance, these findings could potentially contribute to the development of a company's procedures or to enhance existing knowledge of contractor prequalification practices.

This study analyzed the environmental impacts of a single-story residential building using different exterior wall systems. The environmental impacts over the complete life cycle of the residential buildings were determined and compared using the following indicators: air pollution index, energy consumption ͑embodied and operational͒, global warming potential, resource use, solid waste emissions, and water pollution index. The exterior wall systems analyzed were concrete block, poured in-place concrete, insulated concrete, traditional 0.05 m ϫ 0.1 m by 0.4 m ͑2 in. ϫ 4 in. by 16 in.͒ on center wood frame, traditional 0.05 m ϫ 0.15 m by 0.6 m ͑2 in. ϫ 6 in. by 24 in.͒ on center wood frame, and steel stud framing. Additionally, structural insulated panels were modeled for the operational energy of the building. For each scenario, the designs were based on the minimum R value required by the International Building Code. ATHENA, a life-cycle assessment software tool, and eQuest, an energy usage modeling software tool that calculated the operational energy of the building, were used to evaluate the environmental impacts of the building, during the construction, use, and end of life phases, for each scenario. The results show that in the preuse phase, the insulated concrete buildings produce the greatest impact on the environment followed by the concrete block, poured in-place concrete, and steel stud buildings. Traditional wood frames had the fewest environmental impacts when considering only the preuse phase. In the use phase, the insulated concrete buildings had the lowest impacts to the environment because they required less operational energy, whereas concrete block, poured in-place concrete, traditional 0.05 m ϫ 0.15 m by 0.6 m ͑2 in. ϫ 6 in. by 24 in.͒ on center wood frame, traditional 0.05 m ϫ 0.1 m by 0.4 m ͑2 in. ϫ 4 in. by 16 in.͒ on center wood frame, and steel stud framing had progressively larger environmental impacts. The end of life phase was negligible with respect to the other phases. In the complete life-cycle assessment ͑LCA͒, 50-year life span, insulated concrete exterior walls used around 700 GJ ͑5%͒ less energy than traditional wood 0.05 m ϫ 0.15 m by 0.6 m ͑2 in. ϫ 6 in. by 24 in.͒ on center wall systems. The results also indicate the importance of exterior wall's thermal mass for the energy performance of a building, especially for a city located in a hot climate zone such as Phoenix, Arizona, and the importance of a holistic approach, such as LCA, to properly assess the negative environmental impact of different technologies.

Workflow analysis is an important component in the simulation of construction operations. It involves creating a specific number of work requests for a crew every time period, computing outputs such as work arrival rate for a downstream crew and plotting work in process (WIP). These outputs are not directly provided in many construction simulation software tools. Determining these outputs is generally considered a time consuming and tedious undertaking. Developing modeling constructs that automate the computation of these workflow outputs will be useful for construction modelers. This paper presents a special purpose simulation (SPS) template developed for workflow analysis. The SPS template consists of four modeling constructs that implement the workflow analysis functionalities mentioned above. The SPS template logic was verified using two simulation experiments. Use of this SPS template for analyzing different workflow based issues as well as to test the production management principles in construction is also highlighted.

Performance of a construction project, a portfolio of construction projects, a company involved in construction, the regional and national construction sector, and the international construction sector has been a topic for research discourse for many decades. In recent years, the debate was reignited in the United Kingdom by the 1998 "Rethinking Construction" report developed by Sir John Egan 1 . In 2004, Teicholz sparked this discussion by highlighting decline in construction productivity in US by graphically capturing the "Construction and Non-Farm Labour Productivity Index" from 1964 to 2004 2 . Egan and Teicholz set in motion research focussed upon the importance of measuring performance of the construction sector at various levels; focussing more on the output to the Gross Domestic Product of a nation. Spatial and temporal comparison, of the typically comparison resistant, construction sector was forged as a topic of research. However, little renewed attention has been paid to the development of new tools, models, methods and approaches for measuring construction performance at the workface level. The textbook entitled "Managing Performance in Construction" fills this important gap by providing a textbook for construction project management students and a handbook for construction professionals to measure performance in the field. With a rich combination of traditional textbook material, simulation software, innovative website, and an exhaustive list of references the book offers a complete source of guidance on this topic. The authors by combining productivity and effectiveness, and by discouraging a productivity only view, present a compelling business case for a holistic performance management system in construction. While keeping the workface view point the authors encourage an encompassing view of performance that includes the process level and the supply chain level.

India is growing at a fast pace. A direct result of this growth is the tremendous requirements for efficient delivery of physical infrastructure. Therefore the Indian construction sector is poised to play a crucial role in this growth. Much is dependent on the capacity of the sector to efficiently deliver large and complex construction projects. One of the many ways being contemplated to enhance our preparedness towards meeting these challenges is appropriate use of Information and Communication technologies (ICT) in the construction sector. However, beset with fragmentation, SME-predominance, manpower constraints and other factors peculiar to the sector itself, the construction sector has been a slow adopter of technology as a means to achieving business objectives. There is increasing realisation, though, that the sector could be at the cusp of far-reaching changes in this area that will bring wholesome benefits to all stakeholders in the sector. This paper argues for a whole-ofsector approach towards adopting ICT and emphasises that an eTools approach will bring uniform benefits flowing out of better management of time, cost and value to stakeholders. Among other things, timely project completion, reduced risk of errors and project rework, better overall client satisfaction and informed decision making will accrue from improved communication and information flow that results from the adoption and use of ICT. Moreover, advancements in technology have also made it possible for technology to be available with those in the sector who could not earlier afford it making the vision of information available anywhere and anytime now possible.