Life cycle analysis of the environmental impact of different cabinet designs

The design of refrigerated display cabinets greatly affects their subsequent environmental impact. To control this impact, a designer must primarily consider the operating efficiency of a cabinet. However, less account is taken of the materials used to make the cabinet, nor the construction techniques used. These both have a significant effect on the environmental impact of different cabinets outside the use phase of their life cycle. Initial construction impact, remanufacturability and recyclability are all affected. Given the ubiquity of the display cabinet in the retail sector, it is important to assess their lifetime impact in toto. This is particularly so with the increasing implementation of the WEEE directive in member states. Three typical refrigerated display cabinets are examined in this paper, all offering the same function, but manufactured with quite different constructions and materials. The mass of materials in each cabinet was determined experimentally and the methods of assembly examined. The stages in the life of each cabinet were then modelled and life cycle analyses performed. To compare the efficiency of the cabinets in terms of their environmental impact, the Eco Indicator Points/litre of refrigerated space/day were determined in each case. When combined with the energy performance (kWh/litre/day) this provides a good measure of the overall environmental impact of a cabinet and a way of choosing between different models that nominally provide the same refrigeration function. Different end of life scenarios, and improvements in the choice of materials, were also investigated depending on the type of construction

Pines Calyx Earth Tube Performance

In temperate climates earth tubes achieve increased comfort in summer and the pre-heating of inlet air in winter, reducing the requirement for cooling and heating. This strategy was adopted to pre-temper air entering a small conference centre building in Kent, UK. The earth tube is about 16m long comprising a concrete pipe with an internal diameter of 0.6m. The pipe is located approximately 1.5m below ground level. A very low energy fan at the outlet end draws air through the tube and pushes it through a heat exchanger before it is distributed via ducts in the building. This paper reports on the results of monitoring the earth tube temperatures and air velocities under different weather conditions. Temperature sensors were positioned externally and at both ends of the earth tube. An anemometer was fixed in place 4m from the inlet end. This ‘fixed’ anemometer in the earth tube was calibrated and the velocity profile of the air flow in the tube was established. The air in the tube was found to have an almost uniform velocity profile, which is likely to be caused by the considerable turbulence created by changes in the direction of the tube, and the dimensions of the pipe relative to the flow rate. This indicates that the system was well-designed to maximise the heat exchange potential of the duct. The energy contribution of the earth in pre-heating and pre-cooling the air has been calculated at approximately 500W for each degree Kelvin raised or lowered, compared to only 18W power consumed by the fans. This demonstrates that earth tubes can make a very significant contribution to providing heating and cooling, with very low carbon emissions. Earth tubes are a durable and low-cost method of providing resilience in the face of climate change

An Unbiased Estimator of Peculiar Velocity with Gaussian Distributed Errors for Precision Cosmology

We introduce a new estimator of the peculiar velocity of a galaxy or group of galaxies from redshift and distance estimates. This estimator results in peculiar velocity estimates which are statistically unbiased and that have errors that are Gaussian distributed, thus meeting the assumptions of analyses that rely on individual peculiar velocities. We apply this estimator to the SFI++ and the Cosmicflows-2 catalogs of galaxy distances and, using the fact that peculiar velocity estimates of distant galaxies are error dominated, examine their error distributions, The adoption of the new estimator significantly improves the accuracy and validity of studies of the large-scale peculiar velocity field and eliminates potential systematic biases, thus helping to bring peculiar velocity analysis into the era of precision cosmology. In addition, our method of examining the distribution of velocity errors should provide a useful check of the statistics of large peculiar velocity catalogs, particularly those that are compiled out of data from multiple sources.Comment: 6 Pages, 5 Figure

Theoretical Expectations for Bulk Flows in Large Scale Surveys

We calculate the theoretical expectation for the bulk motion of a large scale survey of the type recently carried out by Lauer and Postman. Included are the effects of survey geometry, errors in the distance measurements, clustering properties of the sample, and different assumed power spectra. We consider the power spectrum calculated from the IRAS--QDOT survey, as well as spectra from hot $+$ cold and standard cold dark matter models. We find that sparse sampling and clustering can lead to an unexpectedly large bulk flow, even in a very deep survey. Our results suggest that the expected bulk motion is inconsistent with that reported by Lauer and Postman at the $90-94\%$ confidence level.Comment: 13 pages, uuencoded compressed postscript file with two figures and a table enclosed, UM-AC-93-2

The impact of urban geometry on the radiant environment in outdoor spaces

Urban geometry, namely the quantitative relationship of building volumes and open spaces (i.e. built density) and their spatial configuration (i.e. urban layout), is a major modifier of urban microclimate. This paper presents the results of an ongoing research which explores the impact of urban geometry on the radiant environment in outdoor spaces, with direct implications for urban microclimate and outdoor thermal comfort. In particular, the research investigates the relationship between a set of urban geometric indicators (such as Built Density, Site Coverage, Mean building Height and Frontal Area Density) and Mean Radiant Temperature (Tmrt) at the pedestrian level, in different areas of London. Three representative areas of London were selected to be studied; in central, west and north London which are of high, medium and low built density, respectively. Each area was divided into squares of 500m x 500m size, with a total of 84 urban squares included in the study. The methodology comprises three stages: (i) A set of simple geometric indicators have been computed for all urban squares using special algorithms written and executed in Matlab software. (ii) Radiation simulations have been performed for 10 days of a typical year in London, with the use of SOLWEIG software. SOLWEIG simulates hourly, 3-D radiation fluxes, incoming to / outgoing from the ground, spatial variations of Tmrt, Ground View Factor (GVF) as well as Sky View Factor (SVF). Sunny and cloudy days have been considered, evenly distributed in the year in order for the effect of solar angles to be examined. (iii) Statistical tests have been conducted for investigating the correlation between urban geometry, as expressed by the geometric variables, and hourly, average values of Mean Radiant Temperature in the outdoor spaces of the urban squares. The simulation results show that at night-time and in fully overcast conditions, the outdoor spaces of central London’s urban squares are warmer than those of west and north London, due to greater longwave radiation emitted and reflected by building volumes. In contrast, on sunny days, average daytime Tmrt values have been found to be higher in North London’s urban squares due to the larger insolation of their outdoor spaces. Additionally, the statistical analysis has shown that in the absence of direct solar radiation, the correlation between the geometrical variables and average values of Tmrt is very high with an almost perfect linear relationship between the geometrical variables and average SVF values (r2= 0.980). In the presence of direct solar radiation, the strength of the correlation varies with the sun altitude angle; the higher the sun altitude angle, the higher the correlation. In particular, a threshold altitude angle of 20 degrees has been identified, above which the correlation of average Tmrt values with urban geometry approximates that of night-time / cloudy hours. Finally, further statistical tests showed that site coverage (built area over site area) and frontal area density (façades’ total area over site area) are the strongest indicators among those considered in the analysis

Effect of Night Blinds on Open Integral Display Cabinets

The impact of night blinds on the product temperature performance and electrical energy consumption of an integral open multi-deck cabinet is investigated in this paper. The cabinet was tested at various environmental conditions to establish the impact of ambient temperature on the effectiveness of the blind in reducing the energy consumption of the cabinet during night-time operation. The cabinet was tested over a range of temperatures between 20 °C and 35 °C at a constant moisture content. The results indicate that the use of night blinds could produce energy savings of between 10% and 22% calculated on the basis of a 24 hour period of operation with the blind lowered for 12 hours out of the 24 hours. These energy savings lead to pay-back periods of between 2 and 4 years. The savings reduced with increasing ambient temperature due to the increase in the impact of infiltration and conduction across the blind at higher temperatures

An Investigation Into Thermal Comfort In Residential Buildings In The Hot Humid Climate Of Sub-Saharan Africa: A Field Study In Abuja-Nigeria

A field study was conducted to understand the real and preferred conditions of thermal comfort in low-income residential buildings in Abuja, Nigeria. Knowing the temperatures people are experiencing in their houses and the limits which residents can tolerate is a first step to proffer passive solutions to reduce discomfort. During the study, 40 people responded to a post occupancy questionnaire and two households were issued a comfort survey questionnaire. Physical measurements were taken simultaneously during the comfort survey in both an air-conditioned and naturally ventilated residential building. The ASHRAE and air flow sensation scale were chosen as voting scales. The results from this study show that during the monitoring period the average and maximum temperatures in an air conditioned residential building were 31°C and 34°C; and 33°C and 36°C for natural ventilated buildings in Abuja. This compares with the external average and maximum air temperatures of 31°C and 39°C

Aspects of reheating in first-order inflation

Studied here is reheating in theories where inflation is completed by a first-order phase transition. In the scenarios, the Universe decays from its false vacuum state by bubble nucleation. In the first stage of reheating, vacuum energy is converted into kinetic energy for the bubble walls. To help understand this phase, researchers derive a simple expression for the equation of state of a universe filled with expanding bubbles. Eventually, the bubble walls collide. Researchers present numerical simulations of two-bubble collisions clarifying and extending previous work by Hawking, Moss, and Stewart. The researchers' results indicate that wall energy is efficiently converted into coherent scalar waves. Also discussed is particle production due to quantum effects. These effects lead to the decay of the coherent scalar waves. They also lead to direct particle production during bubble-wall collisions. Researchers calculate particle production for colliding walls in both sine-Gordon and theta (4) theories and show that it is far more efficient in the theta (4) case. The relevance of this work for recently proposed models of first order inflation is discussed

Current Status Of Velocity Field Surveys: A Consistency Check

We present an analysis comparing the bulk--flow measurements for six recent peculiar velocity surveys, namely, ENEAR, SFI, RFGC, SBF and the Mark III singles and group catalogs. We study whether the direction of the bulk--flow estimates are consistent with each other and construct the full three dimensional bulk--flow vectors for each survey. We show that although the surveys differ in their geometry, galaxy morphologies, distance measures and measurement errors, their bulk flow vectors are expected to be highly correlated and in fact show impressive agreement in all cases. We found a combined weighted mean bulk motion of 330 km s$^{-1}$ $\pm 101$ km s$^{-1}$ toward $l= 234^{\degree}\pm 11^{\degree}$ and $b=12^{\degree}\pm 9^{\degree}$ in a sphere with an effective depth of $\sim4000$ km s$^{-1}$.Comment: 16 pages, 2 figures 2 tables, minor changes, reflects published versio