Potential alternatives to edible oils for biodiesel production - A review of current work

Enhancing heat transfer surface are used in many engineering applications such as heat exchanger, air conditioning, chemical reactor and refrigeration systems, hence many techniques have been investigated on enhancement of heat transfer rate and decrease the size and cost of the involving equipment especially in heat exchangers. One of the most important techniques used are passive heat transfer technique. These techniques when adopted in Heat exchanger proved that the overall thermal performance improved significantly. This paper reviews experimental and numerical works taken by researchers on this technique since 2004 such as twisted tape, wire coil, swirl flow generator,… etc. to enhance the thermal efficiency in heat exchangers and useful to designers implementing passive augmentation techniques in heat exchange. The authors found that variously developed twisted tape inserts are popular researched and used to strengthen the heat transfer efficiency for heat exchangers. The other techniques used for specific work environments are studied in this paper. Twisted tape inserts perform better in laminar flow than turbulent flow. However, the other several passive techniques such as ribs, conical nozzle, and conical ring, etc. are generally more efficient in the turbulent flow than in the laminar flow.

A comprehensive review on passive heat transfer enhancements in pipe exchangers

Economic reasons (material and energy saving) leads to make efforts for making more efficient heat exchange. The heat transfer enhancement techniques are widely used in many applications in the heating process to make possible reduction in weight and size or enhance the performance of heat exchangers. These techniques are classified as active and passive techniques. The active technique required external power while the passive technique does not need any external power. The passive techniques are valuable compared with the active techniques because the swirl inserts manufacturing process is simple and can be easily employed in an existing heat exchanger. Insertion of swirl flow devices enhance the convective heat transfer by making swirl into the bulk flow and disrupting the boundary layer at the tube surface due to repeated changes in the surface geometry. An effort has been made in this paper to carry out an extensive literature review of various turbulators (coiled tubes, extended surfaces (fin, louvered strip, winglet), rough surfaces (Corrugated tube, Rib) and swirl flow devices such as twisted tape, conical ring, snail entry turbulator, vortex rings, coiled wire) for enhancing heat transfer in heat exchangers. It can be concluded that wire coil gives better overall performance if the pressure drop penalty is considered. The use of coiled square wire turbulators leads to a considerable increase in heat transfer and friction loss over those of a smooth wall tube.

Review of heat transfer enhancement methods: Focus on passive methods using swirl flow devices

Energy is fundamental to the quality of life in the earth. Meeting the growing demand for energy sustainably is one of the major challenges of the 21st century. Indonesia is a developing country and the world's fourth most populous nation. Total annual energy consumption increased from 300,147 GWh in 1980, 625,500 GWh in 1990, 1,123,928 in 2000 and to 1,490,892 in 2009 at an average annual increase of 2.9%. Presently, fossil-fuel-based energies are the major sources of energy in Indonesia. During the last 12 years, Indonesia has recorded the most severe reduction in fossil fuel supplies in the entire Asia-Pacific region. This reduction has stimulated promoting the usage of renewable energy resources capable of simultaneously balancing economic and social development with environmental protection. Biodiesel is an alternative and environmentally friendly fuel that will participate in increasing renewable energy supply. Jatropha curcas is one of biodiesel resources that offer immediate and sustained greenhouse gas advantages over other biodiesel resources. Globally, J. curcas has created an interest for researchers because it is non-edible oil, does not create a food versus fuel conflict and can be used to produce biodiesel with same or better performance results when testing in diesel engines. The present study is concerned with the prospect of biodiesel produced from J. curcas in Indonesia. The first part gives a summary and overview of energy resources and consumption in the country, second part discusses the potential of biodiesel as a powerful renewable energy resource and third part investigates the potential of J. curcas as a feedstock for biodiesel in Indonesia. The final part discusses the development of biodiesel market in Indonesia. The paper found out that the production of biodiesel from J. curcas offers many social, economical and environmental benefits for the country and can play a great role to solve the problem of energy crisis in Indonesia.

A review on prospect of Jatropha curcas for biodiesel in Indonesia

In this contribution, authors present a review on the state-of-the-art in the utilization of industrial and agricultural waste materials for the development of metal–matrix composites (MMCs), providing, through the judicious analysis of an ample and varied references source – from the oldest to the newest ones – an insight into the challenges and opportunities for the exploitation to their full potential. In addition to its topicality, the novelty of this contribution lies in the presentation of key statistical, technical, and property-related information of a comprehensive variety of waste materials classed into two main groups, namely, fly ash reinforced MMCs and MMCs derived from other waste materials. Although fly ash has been exploited in a broad range of applications, the attention paid for its use in the development of MMCs seems to be insufficient. A purposely designed chart helped to pinpoint the more demanding and profitable applications of fly ash, and establish strategic opportunity ar...

Development of metal-matrix composites from industrial/agricultural waste materials and their derivatives

Copper–5%tin–fly ash mixtures containing 0–16 wt% fly ash with or without copper coating were prepared. Small cylindrical specimens of 9 mm diameter and 10.5 mm length were fabricated at 300 MPa using single action die compaction at ambient temperature. These compacts were sintered in argon atmosphere for a period of 45 min at 700°, 740°, and 780°C, respectively. The green and sintered properties of the compacts were determined as a function of fly ash weight percent. The results indicated that density, hardness, and compression strength of the green compacts were improved by the electroless copper coating on fly ash reinforcement. It was also observed that coated green compacts exhibited lower spring back and higher ejection pressures compared to uncoated compacts. Sintering resulted in increase in density and decrease in volume of green compacts. Sintered density of the composites was found to decrease with increasing weight percent of fly ash. It was further observed that sintering of coated composites...

Preparation and Properties of Sintered Copper–Tin Composites Containing Copper Coated or Uncoated Fly Ash

Effect of Intensified Swirl and Squish on the Performance of a Lean Burn Engine Operated on LPG

The present investigation reports on a study that has been taken up to develop an understanding of the electron beam welding characteristics of similar and dissimilar combination of maraging steel and high strength low alloy steel, which are in the hardened condition, i.e. maraging steel, in a solution that was in treated and aged condition, whereas high strength low alloy steel in a quenched and tempered condition before welding. The joint characterisation studies include microstructural examination, microhardness survey across the weldment and measurement of residual stresses. Maraging steel weld metal is under compressive stress rather than tensile stress as observed in low alloy steel welds because the martensite transformation occurs at a relatively low temperature. It has been observed that, in dissimilar metal welds, tensile stress is observed at the fusion boundary of low alloy steel and weld metal, whereas compressive stress is obtained at the location between weld and maraging steel fusi...

Microstructure, hardness and residual stress distribution of dissimilar metal electron beam welds: maraging steel and high strength low alloy steel

The absence of mechanical moving parts, simplicity and robustness of loop heat pipes (LHPs) has prompted many satellite manufacturers to employ LHPs as primary thermal control systems. The acknowledgement of temperature dynamics of LHP plays a vital role in conception, optimization and control of the same. The overall thermal conductance varies not only with the power input, sink temperature and ambient conditions, but also with the previous history of its operation. In this connection, the present work is focused on a different approach for modeling LHPs. Experimental data for a vertical loop heat pipe made of copper, with two different working fluids, viz., water and ethanol for a range of heat inputs and fill ratios is collected from the literature. An artificial neural network (ANN) is trained with the collected test data and validated. Fully connected feed forward multilayer configuration (MLFFN) with momentum back propagation algorithm is adopted for the ANN. The MLFFN architecture consists of two input nodes representing the parameters heat input and fill ratio, and a single output node representing the thermal resistance of the LHP. The MLFFN predictions were validated within the domain of total available experimental data. This study also emphasizes that the understanding of the physical phenomena of LHP to be modeled by ANN is a prerequisite for getting acceptable results. As there is a serious limitation of conventional techniques for understanding the LHP physical phenomena and thermal behaviour, ANN approach appears to be very promising, if sufficient experimental data is available covering the entire range of system operation.

Performance analysis on modeling of loop heat pipes using artificial neural networks

Biomass derived vegetable oils are quite promising alternative fuels for agricultural diesel engines. Use of vegetable oils in diesel engines leads to slightly inferior performance and higher smoke emissions due to their high viscosity. The performance of vegetable oils can be improved by modifying them through the Transesterification process. In this present work, the performance of single cylinder water-cooled diesel engine using methyl-ester of Jatropha oil as the fuel was evaluated for its performance and exhaust emissions. The fuel properties of biodiesel such as kinematic viscosity, calorific value, flash point, carbon residue and specific gravity were found. Results indicated that B25 have closer performance to diesel and B100 had lower brake thermal efficiency mainly due to its high viscosity compared to diesel. The brake thermal efficiency for biodiesel and its blends was found to be slightly higher than that of diesel fuel at tested load conditions and there was no difference between the biodies...

A. V. Sita Rama Raju

Papers

Preparation and Properties of Sintered Copper–Tin Composites Containing Copper Coated or Uncoated Fly Ash

Effect of Intensified Swirl and Squish on the Performance of a Lean Burn Engine Operated on LPG

Microstructure, hardness and residual stress distribution of dissimilar metal electron beam welds: maraging steel and high strength low alloy steel

Performance analysis on modeling of loop heat pipes using artificial neural networks

Performance and Emission Characteristics of Diesel Engine with Methyl Ester Jatropha Oil and its Blends