On dynamic crack propagation—A literature study

Today, analysis in fracture mechanics has become so important that an international collaborative research programme in this field is being carried out. Its importance lies in the fact that the strength or the toughness of a material cannot be measured directly. Moreover, the present structures are often subjected to dynamic loading. Hence the determination of the dynamic fracture toughness values, in particular the crack arrest toughness and the initiation fracture toughness, at high loading rates has become an essential aspect of present investigations. The present work is primarily concerned with a literature survey on dynamic stress analysis, with specific attention to the determination of the stress intensity factor K for three-point bending (3PB) specimens. Future areas of investigation have been discussed.     

Availability analysis of combustion flue gases—A case study

The thermodynamic availability of combustion flue gases was analysed and modelled. The results were correlated in a polynomial of third degree with a high degree accuracy. It was found, for combustion processes, that the availability losses may reach up to 55% due to draft and dew point limitations in most fired heaters.     

Ellipsometry in the study of selective radiation—Absorbing surfaces

Ellipsometry is the study of surfaces by the analysis of the state of polarisation of reflected light. It is an extremely sensitive technique yet can be quite inexpensive. A simple form of the apparatus is described and the method of determination of optical constants, n and k, discussed. The relevance of the method in the study of selective surfaces is considered and comparisons made between calculated spectral reflectivities and experimental observations for electro-deposited black nickel films on copper substrate. Good agreement is found for a number of different authors, leading to a clearer understanding of former empirical results.     

The performance of heat pumps in service—A simulation study

A computer model is developed to simulate the performance of air-to-water heat pumps heating a house via a radiator system. The performance characteristics of the heat pumps are derived from laboratory measurements. Hourly weather observations are used to calculate the heat demand of the house and the performance of the heat pump. The effects of changes in heat pump characteristics, changes of radiator size, and changes in heat demand of the house due to insulation, are compared in terms of their effects on annual energy consumption.     

A parametric study of closed loop solar heating systems—II

A nondimensional equation describing the closed loop solar heating system with either parallel or series auxiliary heaters is derived. Using European weather data the monthly solar fraction is calculated for variations in the major non-dimensional groups. A correlation is given relating the solar fraction to three non-dimensional parameters M, Kc and Rc. M is the ratio of energy available on the collector aperture to energy demand. To calculate the energy available it is necessary to know the monthly utilizability. Kc is the ratio of the store temperature required for a 100 per cent solar contribution to the average monthly collector peak stagnation temperature. Both these temperatures are referenced to the demand temperature. Rc is the effective “turn over time” of the store, i.e. the number of days to empty the energy contents of the store. The magnitudes of Kc and Rc depend on the load heat exchanger size. Comparisons between the solar fraction predicted with a dimensional hour by hour computer model and that by the correlation are made for two system types. The agreement is good and it is concluded that the correlation can be used as a reliable method to optimise closed loop solar heating systems.     

A study of switching overvoltages on composite feeders—Line-cable feeders

This study is concerned with the overvoltages produced as a result of switching operations on composite feeders, this is when a circuit-breaker closes its contacts at the peak values of the applied voltage. Line-cable feeders are considered in the study. The means by which such overvoltages can be reduced are also included. Also, the effects of system parameters and factors on the initial voltage applied and accompanied overvoltages are covered.     

Hybrid solar–wind domestic power generating system—a case study

A techno-economic study to design a hybrid solar photo-voltaic-wind domestic power generating system for a site on the western coast of India is described. The system uses short-term electrical power storage using lead-acid batteries, and auxiliary power from the A.C. mains power supply.The optimum system would be able to supply 84.16% of the annual electrical energy requirement of the site. The annualized cost of this power in Rs./kwh works out to be several times the present price of government supplied electricity.     

Thermal conductivity of carbon nanotube nanofluid—Experimental and theoretical study

In this work, thermal conductivity of carbon nanotubes' (CNTs) nanofluid is studied both experimentally and theoretically. CNT nanofluids were stabilized using gum arabic (GA). The concentration of CNTs was varied from 0.01–0.1 wt% while the concentration of GA was varied from 1–2.5 wt%, respectively. The effect of particle volume fraction and temperature on the thermal conductivity enhancement of the nanofluids was also studied. A simple thermal conductivity model which demonstrates the effect of diameter and aspect ratio of the CNTs and takes into account the effect of temperature on thermal conductivity enhancement is presented. Good agreement between experimental and estimated values proves that the proposed model can provide precise prediction of the thermal conductivity of fluid containing CNTs. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20405     

Numerical study on the formation of Taylor bubbles in capillary tubes

Numerical simulations have been carried out for the transient formation of Taylor bubbles in a nozzle/tube co-flow arrangement by solving the unsteady, incompressible Navier–Stokes equations. A level set method was used to track the two-phase interface. The calculated bubble size, shape, liquid film thickness, bubble length, drift velocity, pressure drop and flow fields of Taylor flow agree well with the literature data. For a given nozzle/tube configuration, the formation of Taylor bubbles is found to be mainly dependent on the relative magnitude of gas and liquid superficial velocity. However, even under the same liquid and gas superficial velocities, the change of nozzle geometry alone can drastically change the size of Taylor bubbles and the pressure drop behavior inside a given capillary. This indicates that the widely used flow pattern map presented in terms of liquid and gas superficial velocities is not unique.     

Boiling of small droplets

Analysis is reported of the boiling of small diameter suspended droplets, such as found in emulsions. A one-dimensional model considers both the energy and momentum equations, and effects of differences in fluid and thermodynamic properties between the droplet and the surrounding liquid are examined. Results are presented in the form of time varying bubble radius and temperature. The initial boiling of the droplet is insensitive to the surrounding liquid and droplet diameter, while the final evaporation rate is strongly affected by the properties of the surrounding liquid. After a droplet has completely evaporated, the vapor bubble expands and contracts via radial oscillations near the Minnaert frequency for isothermal bubbles. Thermal damping is observed but the model does not capture acoustic damping.     

Flyash disposal problems at thermal power stations—an experimental study

Disposal of flyash at thermal power stations is carried out in the form of ash slurry by mixing the ash with water. The ash slurry is stored in an ash pond. The water in the slurry is gradually drained out, through decanting wells, earthern embankments and over spillways, leaving the ash to deposit in the pond. It is observed that, the design of decanting wells presently being used allows a considerable amount of flyash to flow out with water, leading to the contamination of soil and the water courses. Further, it is observed that, the failure of earthern bunds of ash ponds, which results in a major damage to the environment, is mainly due to ineffective functioning of filters in the bunds. This paper presents the details of an experimental investigation carried out to study the role of geotextiles in improving the performance of decanting wells and earthern bunds. Two series of experiments were carried out. In the first series two model decanting wells were tested with geotextile lining. In the second series, a number of model earthern bunds were tested with and without geotextiles. Economics of providing geotextiles in earthen bunds is studied. The results indicated that, the use of geotextiles is economical and effective in improving the performance of decanting wells and the earthen bunds of an ash pond. Copyright © 1999 John Wiley & Sons, Ltd.     

The use of probability theory in fracture mechanics—A case study

A probabilistic approach to fracture mechanics in the form of a typical case study is described wherein the integrity of a high-pressure water pipeline is assessed. An analysis methodology is discussed incorporating the probability density functions of defect sizes, the statistics of defect occurrences and the statistical distribution of material properties. This method enables the analyst to supply a very simple assessment of safety, based on the probability of failure (a single number) which may be compared to accepted industrial standards (e.g. 10⁻⁶ for nuclear applications). It is argued that this method often offers the only way to scientifically and economically assess the integrity of fracture prone structures.     

Renewable energy in India — a modelling study for 2020–2021

The energy requirement in India is steadily increasing and this requirement is being met by both commercial and renewable energy sources. Due to the non-availability of sufficient resources and a considerable amount of emission of pollutants from commercial energy, it is now being felt that renewable energy has to be utilized to a greater extent. An optimization model was developed to determine the optimum allocation of renewable energy in various end-uses in 2020–2021, taking into account commercial energy requirement. In lighting end-use renewable energy to an extent of 1.27×10¹⁵ kJ can be utilized. Scenarios were developed for various parameters and sensitivity analysis was performed on the model. It was found that for a 3% increase in social acceptance of bio resources, there was 65% decrease in solar PV utilization and to that extent bioresources were introduced. Similar analysis was performed on the model by changing the demand, potential, reliability, emission and employment factors. The analysis revealed the critical parameters for the utilization of a renewable energy source. Using the critical parameters, appropriate policies can be formulated for promoting renewable energy sources.     

The availability of daylight from tropical skies—a case study of Malaysia

In Malaysia, no long-term daylight data are measured. It was only recently that the need to measure the availability of daylight became urgent when the importance of daylighting in buildings was rediscovered. The hourly daylight availability has been simulated for the Malaysian sky using daylight modelling techniques based on empirical and measured solar irradiation and cloud cover data. This paper presents the techniques involved in producing exterior illuminance data. These data were then compared with measured illuminance at Shah Alam and Bangi, Malaysia. The global illuminance levels are generally high, with values exceeding 80,000 lux at noon during the months when solar irradiation is highest. Even during the months when the ground receives less solar irradiation, the peak illuminance can reach 60,000 lux. Applications and uses of such data are in daylighting design, both for visual and thermal comfort, task illuminance and energy-conscious design of buildings. Recommendations are made at the end of the paper on the various climatic data that are required to be measured for overall daylighting design applications.     

A study of the operating characteristics of an experimental absorption cooler using water—lithium bromide—ethylene glycol as a ternary working system

Absorption heat pumps and coolers can be satisfactorily operated using the water—lithium bromide—ethylene glycol ternary system with an ethylene glycol to water mole ratio of 1/15. This gives a high coefficient of performance and a lower risk of crystallization.     

Solar cookers—part-II—cooking vessel with central annular cavity

Cooking vessels used in a solar cooker must be able to transfer the heat trapped in the cooker effectively to the food material. In the preceding paper (Part-I) the advantage of keeping the vessel on lugs was discussed. In the current paper the performance of a cooking vessel with a central annular cavity kept on lugs is discussed. The experiments were conducted for several days using water and thermic fluid as working medium. The studies indicated that the cooking vessel with central annular cavity on lugs performs much better than the conventional vessel kept on the floor of the cooker. The conventional vessel is considered to be the benchmark for the purposes of comparison.     

Ethyl ester of rapeseed used as a biodiesel fuel—a case study

A 1994 Dodge 2500 turbocharged and intercooled diesel pickup fueled with 100% ethyl ester of rapeseed oil was driven by personnel representing the University of Idaho, Agricultural Engineering Department from Moscow, Idaho to Los Angeles, California and back to Moscow and then from Moscow to Ocean City, Maryland, east of Washington, D.C. and back to Moscow, Idaho. These trips covered a total of 14,069 km (8742 miles). The truck averaged 7.76 km/l (18.7 mile/gal) using 1772 l (468 gal) of ethyl ester of rapeseed oil fuel. No problems or unusual events were encountered with the truck's operation. The truck was completely unmodified as to the engine and fuel system. The fuel required for the trip was all processed in the Agricultural Engineering Laboratory at the University of Idaho and was carried on-board as no refueling facilities were available away from Moscow, Idaho. This is believed to be the first coast-to-coast and back run on 100% biodiesel.     

Financing renewable energy projects via closed-end funds—a German case study

During recent years, closed-end funds have become one of the dominant financing schemes for wind farms in Germany. Having evolved out of the traditional model of local citizen-financed wind farms (‘Bürgerwindpark’), closed-end wind funds can be seen as a logical consequence of the increasing professionalism and specialisation trend within the wind business as a whole. This article illustrates the basic market mechanisms behind the project development and financing approach based on closed-end funds and gives an overview on recent market developments in Germany. Finally, the transferability of this approach to other technologies or other regional markets is discussed.     

Micro-level energy planning in India—A case study of bangalore north Taluk

Demand for energy in India is constantly on the rise and the conventional supply options available have failed to cope with this increase. The emergence of efficiency improvement, carrier substitution and renewable energy as alternative sources of energy supply, make adherence only to macro-level energy planning unrealistic. A micro-level (district/taluk) energy planning becomes pragmatic under these circumstances to pursue the goal of sustainable development and to harness locally available energy resources. This paper considers the energy consumption pattern in Bangalore North taluk in 1987–88 and projects the demand for energy in 1995–96. Taking into account the different energy sources used to provide different end-use services through different end-use devices, the paper presents a linear programming formulation for optimum allocation. The model considers the conventional and new alternative technologies for meeting the demand for energy service. The results show that substantial savings could be achieved by this optimal allocation. The cost savings could be to the tune of Rs 41.879 million in Bangalore North taluk during 1995–96 (terminal year of Eighth Five-Year Plan). Energy savings of about 27% and cost savings of 16% could also be achieved.     

Demand analysis for solar photovoltaic cells—a case study of Gundlupet Taluk

The demand for energy in India has been growing steadily over the years. Since conventional energy options have failed to cope with this increase, there has been growing interest in non-conventional energy sources. Solar photovoltaic (SPV) cells could be one such alternative energy source since solar energy is available abundantly in India. It is also renewable and non-pollutant. In this paper, estimation of demand for SPV cells in a drought-prone area of Karnataka State, Gundlupet, is projected for four identified market segments for the year 1996. Comparison of the cost of generation by SPV with that of conventional hydroelectricity with present and future costs is also made. The demand projections are encouraging for use of SPV cells. The projected cost of SPV energy by AD 2000 for amorphous silicon cells would be Rs 7·01 per kilowatt hour for a module price of Rs 55 per peak watt of power and a distance from the rigid of 3 km.