Rapid heat transfer is one of the major concerns in the growing engineering disciplines. Nanofluid has added a new dimension to rapid heat transfer because of its improved thermophysical properties. In this current investigation, investigation was carried out for 0.1% and 0.2% Al2O3/Water nanofluid in turbulent flow. Constant heat flux was supplied in the test section tube with the help of nichrome resistance wire which was spirally winded uniformly on the test section tube. The investigation reveals that the heat transfer coefficient and dimensionless Nusselt number enhance for Al2O3/water nanofluid than water as the working fluid. Heat transfer coefficient also improves with the increase in volume fraction of nanoparticles though the stability of nanofluid decreases. Nusselt number increases by 33.46% for 0.1% Al2O3/water nanofluid compared to water. Conversely, the Nusselt number increases by 57.01% for 0.2% Al2O3/water nanofluid compared to water. A higher thermal performance factor was found for a higher volume fraction of nanoparticles. Friction factor and pumping power per unit length also increase with the increase in the volume fraction of nanoparticles. It was concluded that Al2O3/water nanofluid with a higher volume fraction of nanoparticles gives a higher heat transfer rate for the same pumping power per unit length than water as a working fluid.

Internal combustion (IC) engines are always exposed to extreme temperatures and thermal stresses. So, cooling the internal combustion (IC) engine is necessary to operate. The fins are used in engines to disperse the heat produced by the engine, especially in 4-stroke bike engines. The main focus of this research is to analyse and compare the thermal properties of the IC engine, such as temperature and total heat flux, by varying the shape and materials of four-stroke bike engine fins. In this study, Beryllium oxide (BeO) was proposed as an engine fin besides a few traditional metals. To obtain various temperatures and maximum total heat flux results, a four-stroke 125cc HERO GLAMOUR BS 6 motorcycle engine for various fin shapes such as circular, parabolic, wavy and slotted fins and different materials such as Aluminium 6061, Aluminium 2014, Beryllium oxide (BeO) and Silicon Carbide-Aluminium 2124 (SiC-Al 2124 25%) alloys used in this study. The best performance in case of maximum heat flux was found 8.417% more for Beryllium oxide (BeO) compared to Aluminium 6061 in circular fins.

One of the dominating meat supply industries, the poultry chicken sector, is facing waste management concerns worldwide. Due to high oil content containment, biofuel researchers emphasized poultry waste as abundant, cheap, and high-quality feedstock for biodiesel production. Therefore, in the current study, an experimental investigation of biodiesel production from wasted chicken skin through the transesterification process has been performed. The chicken skin used in this study for biodiesel production can be used as the potential waste source for biodiesel production worldwide. Techno-economic, environmental, and sustainability analyses were also performed. During the synthesis, the reaction was conducted with potassium hydroxide (KOH), and the process yielded 48% biodiesel. The cost of electricity for providing electricity is estimated at US$0.575 per kWh when an auto-sized generator has been fueled by biodiesel. The environmental and substantiality analysis found that biodiesel is more suitable than conventional diesel as an environmentally friendly and sustainable fuel.

Helical baffles, wire coils, and rectangular ribs are used to improve the annular fluid flow turbulence and heat transfer performance. Among the different insert types, loose-fitted helical baffles or strips are of major interest because of their better performance. Tight-fitted helical strips can show better performance in the annular flow because they can act as a fin besides acting as a swirl generator compared to loose-fitted ones. For that reason, a three-dimensional (3D) computational fluid dynamics (CFD) study is performed to investigate the heat transfer and pressure drop characteristics of turbulent flow (4000 <= Re <= 10000) at annuli with and without tight-fitted helical strip inserts. Annuli with 0.6, 0.7, and 0.8 annuli diameter ratio (ADR) are studied for plain and helical strip inserts with pitch ratios (PRs) of 1, 2, and 3. Result showed that higher heat transfer coefficient (HTC) and friction factor were found for insert-fitted annuli compared to those of plain annuli. HTC increased with increase in Re and ADR and decrease in insert PR. The best performance was for 0.8-ADR insert-fitted annuli: 171%-207% (1 PR), 82%-105% (2 PR), and 56%-75% (3 PR) compared to 0.8-ADR plain annuli. Although HTC increased with increase in ADR, the Nusselt number (Nu) decreased because of the smaller hydraulic diameter. Nu increased with increase in Re but decreased with higher ADR and insert PR. The friction factor increased with decrease in insert PR and ADR and decreased with increase in Re. A figure of merit (FoM) was used to combine the benefit of heat transfer enhancement and the drawback of higher pressure drop. The FoM ranged from 0.9 to 1.3, 0.94 to 1.22, and 0.92 to 1.24 for ADR values of 0.6, 0.7, and 0.8, respectively, for a specific Re range. The heat transfer performance obtained was in the order of 3 PR < 2 PR < 1 PR for insert-fitted annuli, but the FoM followed 1 PR < 2 PR < 3 PR because of a much higher pressure drop for lower PR. This study confirms that inserts improve heat transfer, which is better at lower Re. (C) 2021 Elsevier Ltd. All rights reserved.

Industrial furnaces play a significant role in industrial energy consumption and production. Minimizing losses from these furnaces can contribute to industrial sustainability. Exergy being an optimization tool can reduce energy loss and emission from furnaces and contribute to environmental sustainability. Currently, no exergy-based sustainability analysis has been adopted in the literature. In this analysis, a reheater furnace that is fired by natural gas is analyzed in terms of energy and exergy utilization. To address the sustainability of the furnace, several exergy-based sustainability parameters have been used. The overall energy efficiency of the furnace is 93.40%, while exergy efficiency is only 27.37%. From sustainability analysis, it is found that 72.63% of the fuel is diminished from the furnace, and it contributes to a lower sustainability index of 1.38. Higher exergy losses from this furnace positively affect the environment, which is validated from the higher value of the environmental destruction coefficient, the environmental destruction index, and the lower value of the environmental benign index. The value of the environmental destruction coefficient is 3.65, and the value of the environmental benign index is 0.38. Recovering waste energy and optimizing auxiliary equipment will increase the value of sustainability parameters.

Nanofluid is a suspension of nanoparticles which is promising heat transfer fluid in the heat transfer enhancement having a plethora of applications because of its superior thermal conductivity and rheological properties. This paper points out the previous studies and recent progress in the improvement of heat transfer using nanofluid. The recent progresses on preparation and enhancement of stability were reviewed. Thermophysical, heat transfer characteristics of nanofluid and different factors such as particle size, shape, surfactant, temperature, etc. on thermal conductivity were presented. The present study reveals potential applications by utilizing nanofluid such as heat exchanger, transportation cooling, refrigeration, electronic equipment cooling, transformer oil, industrial cooling, nuclear system, machining operation, solar energy and desalination, defense, etc. Few barriers and challenges were also addressed. Finally, the challenges and further research opportunities were presented.

A three-dimensional computational conjugate heat and mass transfer study has been carried out using computational fluid dynamics (CFD) software package ANSYS FLUENT to investigate the effect of insert’s twist ratio on the heat transfer and fluid flow performance. Investigation was carried out for air flow at 300 Kelvin and Reynolds number ranging from 3642 to 21857 through a tube with constant wall heat flux of 8000 W/m2. Validating against Gneilski and Petukhob models, the current model has been used to investigate the effect of insert with twist ratio 3.46 and 7.6 on Nusselt number, friction factor and thermal performance factor of the tube. Results show that for twist ratio of 3.46, Nusselt numbers and friction factors are increased by 20% to 62% and 185% to 245% respectively, and thermal performance factor ranged between 0.9 and 1.2. Those were observed to be increased by 10% to 30%, 128% to 183% and ranged between 0.95 to 1.05 respectively for twist ratio of 7.6. It is concluded that twisted tapes provide better heat transfer enhancement at relatively lower Reynolds number and twist ratio.

In this experiment pyrolysis of coconut shell is done for bio-oil production using infrared radiation as heat source. For this a methodology is structured and experimental setup is prepared for pyrolysis. After cooling of pyrolysis product bio-oil is collected, weighted and tested for different fuel properties. Infrared pyrolysis is a relatively new technology and very few investigation is done about it. The obtained biofuel and char has a calorific value of 22.95MJ/kg, 17.85 MJ/kg and bio-oil's dynamic viscosity is 17 centipoise at 20 degrees c. A maximum oil yield of 43 wt. % is found after 35 minutes of pyrolysis at a heating rate of 40 degrees c/min till 410 degrees c then gradually increasing it to 510 degrees c for remaining time. An oil yield of 38 wt. % is observed after 20 minutes of beginning of pyrolysis which only increases by 4 wt. % in next 20 minutes. So, pyrolysis can be done only for 20 minutes for optimization in production process.

From the slaughtering and processing of livestock, a huge amount of animal discards are produced. Much of this waste biomass is animal fat and skin and these discards can be used to produce biodiesel. In this study, chicken skin was used as raw materials for biodiesel production. Chicken skin was extracted from a local shop and subjected to transesterification. The products of transesterification were Fatty acid methyl esters (FAME) and glycerol. After separating glycerol it was observed that the yield percentage was 35%. Then FAME produced was tested for two parameters namely calorific value, Kinematic viscosity.

Biogas, a source of renewable energy is produced from bacteria in the process of biodegradation of organic matter under anaerobic conditions. A research work was performed to find out the production of biogas from cow dung using charcoal and gelatin as additives. Five laboratory scale experimental set-up were constructed using 0, 0.2, 0.4, 0.6 and 0.8% gelatin with cow dung as additive to perform the research work. For all the set-up 0.5% charcoal was also added. All the set-ups were made from 1-liter capacity conical flask. The amount of water and cow dung was used respectively 382 gm. and 318 gm. in every set-up. Total solid content was maintained 8% throughout all set-ups. The digesters were operated at ambient temperature of 26 degrees-32 degrees C. The total gas yield without using gelatin additive was found to be 12 L/kg cow dung. The maximum gas yield was found from 0.2% gelatin additive and 23% more as compared to without gelatin gas production. The retention time varied from 28 to 79 days for the experiments.

A research work was conducted to investigate the enhanced production ability of biogas from mesophilic anaerobic digestions of cow dung (CD) using gelatin as additive. Five laboratory scale digesters were constructed to digest cow dung, where one set up was used for digestion of cow dung without additive and the other set up were used for digestion with additive. Gelatin additive was added in the slurry of amount 0.29, 0,57, 0.85 and 1.14% (wt.). The digesters were made of glass conical flask of 1-liter capacity each. Cow dung was used 335 gm and water was used 365 gm in each experiment. In the slurry, total solid content was maintained 8% (wt.) for all the observations. The digesters were fed on batch basis. The digesters were operated at ambient temperatures of 26 - 35 degrees C. The total gas yield was obtained about 14.4 L/kg CD for digestion without additive and about 65% more biogas for digestion with 0.29% gelatin additive. The retention time for digestion without additive was 38 days and with additive retention time varied between 24 and 52 days.

The heat pipe is a highly effective heat transmitting device that allows transferring a large amount of heat over a considerable distances with minimal temperature difference. As heat pipe can transmit a large amount of heat by the virtue of latent heat of vaporization and condensation by using a two phase fluid as working fluid and it requires no external power source, it has become one of the heavily investigated approaches to the researcher in the field of heat transfer. This paper illustrates an experimental work for a simple vertical heat pipe using refrigerant R-22 with a view to analyzing the performance for free and forced convection with and without the application of a constant power input. The overall thermal contact resistance was also calculated and compared for free and forced convection. During the experiment the air velocities of 2.4 and 3.2 m/s was used for forced convection and a constant power input of 7.84 watt was applied. It has been observed that forced convection require 67% to 70% less time than free convection. The overall thermal resistance was also found to be higher in forced convection than free

This research work has been performed to produce biogas from poultry and household (kitchen) waste using silica gel as a catalyst.A fabricated laboratory scale digester was used to generate biogas from the locally available waste obtained from poultry farms and domestic kitchens.Two laboratory-scale digesters were prepared to digest the solid wastes with and without silica gel respectively.The operating temperatures of the digesters were maintained within 26°C-31°C.The water displacement method was used to investigate the volume of the produced gas.It was found that the production rate of biogas was increased while using silica gel as catalyst.The total gas production was found to be 7921 ml/kg of waste without silica gel whereas it was 10545 ml/kg with a maximum production rate of 1206 ml/kg in a day with silica gel as a catalyst and it was 33.12% higher than before.Finally, by using a k-type thermocouple, the flame temperature of the gas was measured as 619°C.Considering the magnitude of flame temperature and total gas yield after adding the silica gel, the large scale set-ups can be a prospective source of clean energy.

Biogas originates from bacteria in the process of biological breakdown of organic material under anaerobic conditions. A research work was conducted to investigate the production ability of biogas from mesophilic anaerobic digestions of cow dung (CD) using silica gel as catalyst. Two laboratory scale digesters were constructed to digest cow dung, where one set-up was used for digestion of cow dung without catalyst and the other set-up was used for digestion with catalyst. The digesters were made of glass conical flask of 1-liter capacity each. Cow dung was used 390 gm and water was used 310 gm in each experiment. In the slurry, total solid content was maintained 8% (wt.) for all the observations. The digesters were fed on batch basis. The digesters were operated at ambient temperatures of 27–31°C. The total gas yield was obtained about 27.3L/kg CD for digestion without catalyst and about 30.5L/kg of CD for digestion with catalyst. The retention time was about 76 days for both the digestions. The gas yields were compared with the previous work of mesophilic digestions of cow dung without catalyst of operating temperatures 18–28°C.

In this study a series of Pt-Ni composites were supported on alumina doped with 3 wt% ceria, and the resulting materials were characterized and tested as catalysts for the aqueous phase reforming of glycerol to produce H2. Amongst the catalysts tested, bimetallic 1Pt-6Ni/3CeAl catalyst gave the highest H2 yield (86%) and gas phase C yield (94%), even though it contained one third as much Pt as the benchmark 3Pt/3CeAl catalyst. Though the 3Pt/3CeAl and 1Pt-6Ni/3CeAl catalysts produced almost same amount of H2 (1.8 and 1.9 mmol respectively) for per gram of catalyst per hour, 1Pt-6Ni/3CeAl produced five times (258 mmol) as much H2 per gram of Pt per hour, this could make the catalyst competitive for large scale H2 production. X-ray diffraction (XRD) and thermogravimetric (TG) analyses of the spent catalysts showed no serious catalyst deactivation by carbon deposition after 30 hour on stream, except in the case of Pt-free 6Ni/3CeAl, which ceased to produce H2 after 15 hour on stream.

An experimental study was conducted to evaluate the performance of heat transfer for turbulent flow through a tube using air as the working fluid with perforated rectangular strip inserts. Mild steel rectangular strips of different pore diameters 2.1, 3.2, 4.25, 5.3, and 7.42 mm with corresponding porosities of 1.1%, 2.5%, 4.4%, 6.8%, and 13.3%, respectively, were used in the flow field. Heat transfer and pressure drop data were taken for Reynolds numbers ranging from 14,000 to 47,000. The experimental results showed that the Nusselt number, heat exchanger effectiveness, and friction factor were higher than those of the plain tube. The Nusselt number and the friction factor for employing the perforated strip inserts were found to be increased up to 2.65 and 1.75 times, respectively, over the corresponding plain tube. The heat transfer performance was evaluated and found to be 2.5 times higher compared to the plain tube based on the constant blower power. Finally, a correlation was developed with the experimental data for prediction of heat transfer in turbulent flow through a tube with perforated rectangular strip inserts.

An experimental investigation was carried for measuring tube-side heat transfer coefficient, friction factor, heat transfer enhancement efficiency of water for turbulent flow in a circular tube fitted with rectangular-cut twisted tape insert. A copper tube of 26.6 mm internal diameter and 30 mm outer diameter and 900 mm test length was used. A stainless steel rectangular-cut twisted tape insert of 5.25 twist ratio was inserted into the smooth tube. The rectangular cut had 8 mm depth and 14 mm width. A uniform heat flux condition was created by wrapping nichrome wire around the test section and fiber glass over the wire. Outer surface temperatures of the tube were measured at 5 different points of the test section by T-type thermocouples. Two thermometers were used for measuring the bulk temperatures. At the outlet section the thermometer was placed in a mixing box. The Reynolds numbers were varied in the range 10000-19000 with heat flux variation 14 to 22 kW/m2 for smooth tube, and 23 to 40 kW/m2 for tube with insert. Nusselt numbers obtained from smooth tube were compared with Gnielinski [1] correlation and errors were found to be in the range of -6% to -25% with r.m.s. value of 20%. At comparable Reynolds number, Nusselt numbers in tube with rectangular-cut twisted tape insert were enhanced by 2.3 to 2.9 times at the cost of increase of friction factors by 1.4 to 1.8 times compared to that of smooth tube. Heat transfer enhancement efficiencies were found to be in the range of 1.9 to 2.3 and increased with the increase of Reynolds number.

Influence of triple helical tapes inserted for turbulent flow through a tube on heat transfer enhancement was studied experimentally. The triple helical tapes made of mild steel with different helix angles, α = 9°, 13°, 17°, and 21° were examined for Reynolds number ranging from 22,000 to 51,000. The experiment showed that the Nusselt number, effectiveness and friction factor for the inserts were found to be up to 4.5, 3.45 and 3.0 times, respectively, over the plain tube. The highest enhancement efficiency achieved was 3.7 for the inserts based on constant blower power. Finally, new correlations for predicting heat transfer and friction factor for turbulent flow through a circular tube fitted with the inserts were proposed.

In condensation over horizontal tubes where the wall temperature is not measured directly, the Wilson plot is used to determine the cooling side heat transfer coefficient. Conventionally, the variation in Nusselt number, Nu, with condensate side temperature drop, DTs, which accompanies change of cooling side flowrate, is assumed to be Nu µ 1/DTsn with n = 0.25. This is the free convention condensation value. In this paper a technique is devised, not only to check the accuracy of this assumption in the usual vapor side cross flow situation, but also to determine the effect on this accuracy of allowing the index n to vary. In a case study the best agreement between DTs assumed and the value obtained using the cooling side heat transfer coefficient which resulted from the Wilson plot, occurred at n = 0.21. Based on the random errors in the measured data, a linear regression taking into account the errors in both Wilson plot coordinates gave the cooling side heat transfer coefficient and its uncertainty.Keywords: Heat transfer; condensation; Wilson plots.DOI: 10.3329/jme.v41i1.5360Journal of Mechanical Engineering, Vol. ME 41, No. 1, June 2010 31-41