The performance of an ASHP system using waste air to recover heat energy in a subway system

In this short communication, we demonstrate that the performance of a typical air source heat pump (ASHP), exploiting a relatively stable air temperature within a subway environment, is high, even during the peak heating months. After a nine-month operational run, the coefficient of performance is demonstrated to be 3.5. The design and installation difficulties are stated together with the lessons learnt following this trial. The actual energy and carbon savings are discussed

Waste Water Transformed into Heat Energy

This study investigates the feasibility of utilising ground water ingress into the Glasgow Subway system. At present this unused excess water is being discharged into the city’s drainage system as waste. This valuable resource could be channelled through a Water Source Heat Pump (WSHP) to produce heat energy for domestic or public use (heating and domestic hot water). A study has been carried out in order to calculate the heat contained in the water. Water flow and water temperature have been recorded over a ten month period (since May 2014) at fifteen different points within the network of underground tunnels. Water sampling has also been undertaken at all of these points, with chemical analysis results for six of them already obtained. The measurements will continue for at least seven more months to have readings for an 18 months period. A feasibility study to review the number of support factors (i.e. Renewable Heat Incentive) that could profit the subway system has been undertaken as well. Options have been discussed and a selection of a site inside the tunnels for a pilot system has been decided and is due to be installed in June 2015. The findings of this study are expected to develop an appropriate renewable solution through a cost effective heat pump system design. This waste water will be collected and used as renewable energy. During this process energy will be produced from a waste product using a sustainable and environmental friendly method. A similar approach ought to be transferable to many other subway systems around the world, some of which experience ground water ingress

Heat recovery from air in underground transport tunnels

The performance of a typical air source heat pump could be increased dramatically by a relatively stable air temperature with a high humidity, even during the peak heating months. In this short communication we show such conditions exist in the underground transport tunnels of the Glasgow Subway system, where we had conducted an annual survey of air flow, air temperature and relative humidity at thirty different points within the subway network. We found relatively stable temperatures and sufficient air movement inside the twin tunnels (average temperature during winter = 15 °C, annual variation = 2.6 °C; average air flow = 16.47 m3/h) indicating higher system efficiency compared to a conventional air source heat pump installation. Potential energy and carbon savings are discussed

The impact of process parameters on surface roughness and dimensional accuracy during CO2 laser cutting of PMMA thin sheets

This study investigated the impact of the laser speed and power, and the position and orientation of the samples, on the average surface roughness (Ra) and dimensional accuracy (DA) during CO2 laser cutting of polymethyl methacrylate (PMMA) thin sheets. A mixed five-parameter fractional factorial design was applied, and thirty-six measurements for the Ra and DA were obtained. The experimental results were analysed using ANOM diagrams, ANOVA analysis and interaction plots of all parameters. It was concluded that the laser speed is the critical parameter for both surface roughness and dimensional accuracy, resulting in strong interactions with laser power and positioning parameters. It was also shown that Ra values are affected by the orientation of the specimen and can be minimized when the samples are aligned in the laser travel direction. Finally, it was proved that lower laser speed improves the average roughness but reduces the dimensional accuracy

A generalised approach on kerf geometry prediction during CO2 laser cut of PMMA thin plates using neural networks

This study presents an application of feedforward and backpropagation neural network (FFBP-NN) for predicting the kerf characteristics, i.e. the kerf width in three different distances from the surface (upper, middle and down) and kerf angle during laser cutting of 4 mm PMMA (polymethyl methacrylate) thin plates. Stand-off distance (SoD: 7, 8 and 9 mm), cutting speed (CS: 8, 13 and 18 mm/sec) and laser power (LP: 82.5, 90 and 97.5 W) are the studied parameters for low power CO2 laser cutting. A three-parameter three-level full factorial array has been used, and twenty-seven (33) cuts are performed. Subsequently, the upper, middle and down kerf widths (Wu, Wm and Wd) and the kerf angle (KA) were measured and analysed through ANOM (analysis of means), ANOVA (analysis of variances) and interaction plots. The statistical analysis highlighted that linear modelling is insufficient for the precise prediction of kerf characteristics. An FFBP-NN was developed, trained, validated and generalised for the accurate prediction of the kerf geometry. The FFBP-NN achieved an R-all value of 0.98, in contrast to the ANOVA linear models, which achieved Rsq values of about 0.86. According to the ANOM plots, the parameter values which optimize the KA resulting in positive values close to zero degrees were the 7 mm SoD, 8 mm/s CS and 97.5 W LP

Dynamic vehicle routing problems: Three decades and counting

Since the late 70s, much research activity has taken place on the class of dynamic vehicle routing problems (DVRP), with the time period after year 2000 witnessing a real explosion in related papers. Our paper sheds more light into work in this area over more than 3 decades by developing a taxonomy of DVRP papers according to 11 criteria. These are (1) type of problem, (2) logistical context, (3) transportation mode, (4) objective function, (5) fleet size, (6) time constraints, (7) vehicle capacity constraints, (8) the ability to reject customers, (9) the nature of the dynamic element, (10) the nature of the stochasticity (if any), and (11) the solution method. We comment on technological vis-à-vis methodological advances for this class of problems and suggest directions for further research. The latter include alternative objective functions, vehicle speed as decision variable, more explicit linkages of methodology to technological advances and analysis of worst case or average case performance of heuristics.© 2015 Wiley Periodicals, Inc