Search results

The purpose of the paper is to study natural convection within porous square and triangular geometries (design 1: regular isosceles triangle, design 2: inverted isosceles triangle) subjected to discrete heating with various locations of double heaters along the vertical (square) or inclined (triangular) arms.

Galerkin finite element method is used to solve the governing equations for a wide range of modified Darcy number, Da_m = 10⁻⁵–10⁻² with various fluid saturated porous media, Pr_m = 0.015 and 7.2 at a modified Rayleigh number, Ra_m = 10⁶ involving the strategic placement of double heaters along the vertical or inclined arms (types 1-3). Adaptive mesh refinement is implemented based on the lengths of discrete heaters. Finite element based heat flow visualization via heatlines has been adopted to study heat distribution at various portions.

The strategic positioning of the double heaters (types 1-3) and the convective heatline vortices depict significant overall temperature elevation at both Da_m = 10⁻⁴ and 10⁻² compared to type 0 (single heater at each vertical or inclined arm). Types 2 and 3 are found to promote higher temperature uniformity and greater overall temperature elevation at Da_m = 10⁻². Overall, the triangular design 2 geometry is also found to be optimal in achieving greater temperature elevation for the porous media saturated with various fluids (Pr_m).

Multiple heaters (at each side [left or right] wall) result in enhanced temperature elevation compared to the single heater (at each side [left or right] wall). The results of the current work may be useful for the material processing, thermal storage and solar heating applications.

The heatline approach is used to visualize the heat flow involving double heaters along the side (left or right) arms (square and triangular geometries) during natural convection involving porous media. The heatlines depict the trajectories of heat flow that are essential for thermal management involving larger thermal elevation. The mixing cup or bulk average temperature values are obtained for all types of heating (types 0-3) involving all geometries, and overall temperature elevation is examined based on higher mixing cup temperature values.

The first part of the paper describes the results of an extensive search into two factors which effect, to a high degree, the efficiency of online information retrieval: (i) the manner by which classification codes and keywords are chosen as a means of retrieval by the reviewers of the reference work (ii) the degree in which papers with comparable contents are accorded similar keywords. The influence of these two factors on the practical results is shown by the example of extensive searches: these searches were done manually as well as online. It was concluded that the efficiency of the assigned keywords was very low, owing to their insufficient accuracy and the large number of synonyms, spellings and other words that there may be to express one idea. The purpose of the analysis as described in the second part of the paper is to examine the possibility of finding a good search strategy, in spite of the low efficiency of the assigned keywords, that costs little and has a high efficiency factor. Therefore, a three‐fold situation is examined: (i) the relationship of the search strategy to (ii) the factors affecting cost, and (iii) the efficiency of retrieval. The problems arising in choosing a search strategy are examined; 14 different methods were selected from the large number of possibilities to formulate a search. A method of calculating the factors which affect the connect‐time cost and the offprint costs is worked out. The various strategies, employed to achieve the greatest improvements in cost and efficiency, include classification codes and keywords (subject headings and free terms). This procedure was carried out via an ESA terminal. The results are presented in the form of tables comparing the size of the factors affecting the cost, the judged cost per relevant item and the efficiency of retrieval. The conclusion is that the best search consists of using the classification codes, including the subject, coupled with some carefully selected free terms, for the simplest method, the lowest cost and the highest efficiency of retrieval.

The purpose of this paper is to investigate the reduction in efficiency of central heating systems of multi-family buildings when independent heating capability is offered to each apartment, to access the impact of the applied heating cost allocation (HCA) on this deterioration and suggest highly cost-effective ways (operation, control strategy, alternative HCA) of overcoming them at minimum cost.

The paper reveals the problem of reduced efficiency in centrally heated multi-family dwellings through two case studies in real buildings, where data-loggers were installed and performance curve analysis was performed, in combination with detailed simulation.

The paper finds that the enforcement of a suitable HCA regulation is a prerequisite to achieving energy savings in centrally heated multi-family dwellings. In addition the effects of dissimilarly heated apartments on the total energy demand and the significance of indirect heating and how these should be charged, are assessed. It is found that convenient operation of the central heating system may lead to high energy cost savings and higher efficiency at no cost.

HCA adopted more than three decades ago should be revised according to the present situation, namely, increasing fuel costs, existence of many low income families, energy poverty, availability of alternative (or supplementary) heating devices and better building envelopes.

Occupants of multi-family dwellings should be appropriately educated and agree on rational use of the common heating system of the building.

The paper identifies weak points of valid HCA regulation, reveals inefficiencies in centrally heated multi-family dwellings and measures the actual effectiveness of remedying measures. Detailed simulation contributes to the scientific documentation of the findings.

Looks at models constructed for the gas industry domestic, central heating, cooling and industrial markets. Shows how these models can be used to permit the rapid assessment of marketing targets for appliance sales and price levels against gas supply constraints. Concludes that although these models do not provide instant solutions to the marketing problems of the gas industry they do help to organize available data in a more efficient way.

The purpose of this paper is to look more closely at the residents' attitude to individual heat metering and charging systems (IMC) of multi‐family dwellings in residential properties, and to evaluate the tenant's perception of IMC and how it may affect the continued expansion of such systems.

The research in this paper is based on a questionnaire and interviews with tenants at two municipal housing companies, in Sweden, that currently are using IMC.

The studies in this paper show certain dissatisfaction with the applied IMC systems. This depends partly on the tenant's perceived lack of knowledge and partly because of the technical shortcomings of the IMC system.

In order to increase the extension of IMC a better understanding is required of how the systems work and why they are used. Information to the tenants needs to be improved and techniques need to be developed to create fairer systems of IMC and thus increase the level of acceptance from both landlords and tenants.

The purpose of this paper is to outline an early adopter “low energy” domestic dwelling, one of the social houses built by a collaboration between a university, the local council. The origins of this project are from the early days of interest in sustainable housing, the 1970s. The dwellings were innovative and built to what became known as “the Salford design” which performed to unusual specifications, using approximately 75 per cent less energy than the UK average for space heating and over 40 per cent less than for houses built to what were then the standard building regulations.

A qualitative and interpretative stance was deemed to be the most appropriate. Within that lens, interviews were chosen as the primary research instrument.

A marked feature of the results is the variation in energy consumption by different households. A Salford-designed house could be habitable throughout the year without any space heating at all, comfortable at 10 per cent and very comfortable at 25 per cent of normal consumption.

As there continues to be interest and commitment to reducing energy – not just from the United Kingdom but also on a worldwide scale – the United Nations Conference of the Parties known as COP 22 (2016) met in Morocco to take forward many of the initiatives outlined in the Paris Agreement 2015. It is of interest, then, that the latest set of interviews showed that the houses built to the innovative and original 1970s’ Salford design principles, protected by highly insulated well-sealed envelopes, are even presently functioning at a relatively low energy threshold.

Stresses the importance of forecasting in essential supply industries such as the gas industry with regard to storing the product. Examines some of the problems encountered in this area and how they are dealt with.

The heating of resin kettles has traditionally been achieved using steam, induction heating or direct firing. In recent years, thermal fluid heating has been a further option available with many advantages to offer. We will consider these alternatives in turn.

The purpose of this paper is to describe how a traditional metal base plate is replaced with a vapour chamber, a two‐phase flow heat transfer module with high heat transfer efficiency, to effectively reduce the temperature of heat sources as graphic processing unit (GPU) of smaller area and higher power.

As a first step, the nature of flow field of a vapour chamber‐based thermal module with heat sink is simulated and analysed through computational numerical method. Second, a sample is prepared according to the theoretical results and the performance of thermal modules is tested together with thermal performance experiment.

The results show that when the fin height from vapour chamber top to fan bottom area is more than 3 mm and not more than 8 mm, the vapour chamber‐based thermal module can achieve the optimum heat dissipation and the maximum heat flux may exceed 90 W/cm². Also, when copper fins are 3 mm in height, 0.2 mm in thickness, 53 in number and spaced out 1.0 mm apart, the optimum total thermal resistance of a vapour chamber‐based thermal module is 0.28 ^○C/W.

The Sapphire Atomic HD3870 of Video Graphics Array module for AMD RV670XT using MicroLoops vapour chamber has greater thermal performance than the AMD reference dual slot thermal module. So, AMD latest GPU is considered to be the vapour chamber thermal cooler to solve the higher power consumption.

Many institutions of higher education have committed to carbon neutrality. Given this goal, the main economic issue is minimizing cost. As for society as a whole, dominant decarbonization strategies are renewable electricity generation, electrification of end uses and energy efficiency. The purpose of this paper is to describe the optimum combination of strategies.

There are four questions for eliminating the primary institutional greenhouse gas emissions: how much renewable electricity to produce on-site; where and at what price to purchase the balance of renewable electricity required; how to heat and cool buildings without fossil fuels; and how much to invest in energy efficiency. A method is presented to minimize decarbonization costs by equating marginal costs of the alternates.

The estimated cost of grid-purchased carbon-free energy is the most important benchmark, determining both the optimal level of campus-produced renewable energy and the optimum efficiency investment. In the context of complete decarbonization, greater efficiency investments may be justified than when individual measures are judged only by fossil-fuel savings.

This paper discusses a theoretically ideal plan and implementation issues such as purchasing carbon-free electricity, calculating marginal costs of conserved energy, nonmarginal cost changes, uncertainty about achieving efficiency targets, and dynamic pricing. The principles described in this study can be used to craft a cost-minimizing decarbonization strategy.

While previous studies discuss decarbonization strategies, there is little economic guidance on which strategies are optimal, on how to combine strategies to minimize cost or how to identify a preferred path to decarbonization.