Sustainable design of hydrocarbon refrigerants applied to the hermetic compressor

International environmental concern led to the control and phase out of traditional chlorofluorocarbon refrigerants (CFCs) under the terms of the Montreal protocol. CFCs used in domestic applications were initially replaced with hydrofluorocarbons (HFCs) such as R134a which has a zero ozone depletion potential (ODP). The use of HFCs has also come under scrutiny as they have high global warming potential (GWP) and inferior thermodynamic and lubricating properties and have been replaced by hydrocarbon (HC) refrigerants such as R600a in much of the domestic European and Asian markets. Despite this, there has been little research into the long-term environmental consequences of their application. Domestic refrigeration compressors were analysed to ascertain the tribological contact conditions for both R600a and R134a systems. A novel pressurised micro-friction test machine was developed to simulate the tribological conditions of the critical components using aluminium on steel samples. Refrigerant charges of R600a with mineral oil (MO) and poly-ol-ester (POE) lubricant and R 134a with POE were tested for their tribological performance within the test rig. Experimental tribological information is presented from the physical test procedures to establish wear mechanisms and friction coefficients within the critical components. The tribological performance is used to predict deterioration in energy consumption and system durability. Results indicate that for higher contact stresses R600a MO charges provide a lower wear regime than R600a and R134a POE charges. At lower contact stresses the R600a and R134a POE charges provide a very low wear, very low friction regime. Despite contact conditions lead to a faster deterioration in durability, hence increase in energy consumption compared to the R600a system

Investment in Sustainable Development: A UK Perspective on the Business and Academic Challenges

There are many legislative, stakeholder and supply chain pressures on business to be more ‘sustainable’. Universities have recognised the need for graduate knowledge and understanding of sustainable development issues. Many businesses and universities have responded and introduced Sustainable Development models into their operations with much of the current effort directed at climate change. However, as the current worldwide financial crisis slowly improves, the expectations upon how businesses operate and behave are changing. It will require improved transparency and relationships with all stakeholders, which is the essence of sustainable development. The challenges and opportunities for both business and universities are to understand the requirements of sustainable development and the transformation that is required. They should ensure that knowledge is embedded within the culture of the organisation and wider society in order to achieve a sustainable future

The Challenges Facing Education in Engineering Drawing Practice

The Engineering Drawing has traditionally communicated the technical product specification (TPS) evolving to reflect technologies such as 2D and 3D-CAD as well as the full ISO Geometrical Product Specification (GPS). Although Model Based Definition (MBD) or Product Manufacturing Information (PMI) omit the use of drawing to communicate the TPS they lend themselves ideally to ISO-GPS methods. The methods present an opportunity to ensure Design and Engineering students are equipped with knowledge and understanding of GPS relevant to conventional TPS as well as PMI/MBD. A survey of industry experts indicated expectation of good knowledge and understanding of the underlying GPS methods alongside traditional elements such as orthographic projections and line-types and a fair or good understanding of PMI/MBD application. New materials and delivery structures were developed and implemented for the level 4 Design Media Unit; lectures were translated to seminars where the lecture element focused upon examples rather than rules with students applying the techniques using simple paper sketches. Throughout the series a simple scotch-yoke assembly was utilised, with rapid-prototyped physical working models and components distributed for students to work with; this provided familiarity of function, fit and form throughout the five week programme. The CAD tutorials utilised pre-modelled components identical to those used during the lectures. Students applied the methods practiced during the seminar and reinforced learning outcomes; students evaluated and recorded the appropriate fit, orientation and form tolerances to ensure system functionality with “worse-case” stack up. All components were considered together in order to maintain design intent and functionality

Challenges of 3D Printing for Home Users

3D printing is described as the next industrial revolution bringing manufacturing to the home. However, it’s attraction to the home or non-technical user is frustrated by the difficulty in deploying the software and the technology which both need professional understanding and training. Research and innovation in this area has concentrated on technology, not users and usability. Home users can access simple design software tools, best described as good for one task only. Software such as Microsoft word and Excel have been the subject of development for enabling most people to use computers without the need for training or the ability to program. However research in the home users of 3-D printing is very limited. This literature review is concerned is an investigation into home/non-technical use of 3-D printers, their needs and limitations, in order to facilitate the development of effective tools and manuals. An investigation of literature and a survey supported by a focus group of 42 university students aims to understand the way home/non-technical users currently use designs, and how they can to adapt/change their designs for effective use of 3-D printing. This will identify the tools/’apps’ needed for accessible understanding and deployment of the technology

PAL Week: Learning Sustainable Development in Design and Engineering

Institutional guidance highlights the wider qualitative aspects of sustainability, however these are largely ignored within engineering education in favour of quantitative methods. To encourage understanding of these aspects a course was developed as part of induction for BSc Design Engineering and MEng Engineering students. The one week course has been delivered to mixed groups of first and second year students since introduction in AY2010-11 and has evolved from examining “social usefulness” to include “material utilisation” and “future vision”. The one week assessed programme employs PBL and PAL methodologies to promote student engagement with the concepts of sustainable development. Each group is issued with a variation of the brief but with common underlying themes. The key to success has been the avoidance of didactic elements; students are expected to present their findings at daily presentations before a short micro-seminar and adaptation re-shapes their objectives. Students are not told who will be presenting for their group and no notes are allowed, ensuring all members know and understand the work done. Outputs have shaped how sustainable development is understood within the context of design engineering from a practical as well as educational perspective and resulted in a number of published works

Wear Performance Analysis of Ni-Al2O3 Nanocomposite Coatings under Nonconventional Lubrication

This article presents the wear study of Ni-Al2O3 nanocomposite coatings in comparison to uncoated steel contacts under reciprocating motion. A ball-on-flat type contact configuration has been used in this study in which a reciprocating flat steel sample has been used in coated and uncoated state against a stationary steel ball under refrigerant lubrication. The next generation of environmentally friendly refrigerant HFE-7000 has been used as lubricant in this study without the influence of any external lubricant. The thermodynamic applications and performance of HFE-7000 is being studied worldwide as it is replacing the previous generation of refrigerants. No work however has been performed to evaluate the wear performance of HFE-7000 using nanocomposite coatings. The wear scar developed on each of the flat and ball samples was studied under a Scanning Electron Microscope (SEM). The micrographs show that a combination of adhesive and abrasive wear occurs when using uncoated steel samples. Micro-delamination is observed in the case of Ni-Al2O3 nanocomposite coatings accompanied by adhesive and abrasive wear. Wear volume of the wear track was calculated using a White Light Interferometer. Energy-Dispersive X-ray Spectroscopic (EDS) Analysis of the samples reveal fluorine and oxygen on the rubbing parts when tested using coated as well as uncoated samples. The formation of these fluorinated and oxygenated tribo-films help reduce wear and their formation is accelerated by increasing the refrigerant temperature. Ni-Al2O3 nanocomposite coatings show good wear performance at low and high loads in comparison to uncoated contacts. At intermediate loads the coated contacts resulted in increased wear especially at low loads. This increase in wear is associated with the delamination of the coating and the slow formation of protective surface films under these testing conditions

Novel experimental setup to assess surfaces in tribo-contact lubricated by the next generation of environmentally friendly thermo-fluids.

Environmental concerns related to global warming and ozone depletion triggered the introduction of the fourth generation of thermo-fluids. Amongst the recently introduced thermo-fluids, one of the most promising fourth generation of thermo-fluids are Hydrofluoroethers (HFEs). Hydrofluoroethers have zero ozone depletion potential and have a lower global warming potential as compared to widely used thermo-fluids. The type of thermo-fluid used in a thermodynamic cycle directly affects the tribological performance of the system. HFEs have been reported to have good thermodynamic properties. The overall tribological performance of Hydrofluoroethers however have to be investigated in detail in-order to fully assess the mechanical behaviour of interacting components utilizing these thermo-fluids. This study is concerned with the experimental test rig design modifications and commissioning to conduct tribological testing with HFEs as lubricants. This article covers the experimental test rig design and setup. Experiments to analyse the frictional force, the coefficient of friction and wear by using Hydrofluororther-7000 (HFE-347mcc3) as lubrication medium have been conducted. Industrial applications were simulated by varying test conditions and the results are presented in this paper

Model Based Definition: Finally, the Engineering Drawing Killer?

The Engineering drawing has stood as the universal method of translating design intent since the first standard was formalized in 1927 as BS308. Further development of national and international standards has been informed by advances in CADCAM technology and the need for transfer of complex yet unambiguous definition between organisations. The emergence of model based definition (MBD) has driven a new workflow where the engineering drawing is no longer required. Instead, the dataset includes semantic, machine readable, tolerancing of surfaces and features for integration into manufacturing and metrology procedures. Despite the advantages of MBD, it has been largely ignored in UK Higher Education. However MBD is the ideal method for teaching and learning geometrical tolerancing since it ignores the theoretically exact dimensions and housekeeping, concentrating on the functional limits. Further, it utilises the 3D workspace that students are increasingly familiar with