Applied Mechanics and Materials Vols. 592-594

Abstract: Pulsating heat pipe (PHP) is a passive heat transfer device, which transfers heat from one region to another with exceptional heat transfer capacity. It utilizes the latent heat of vaporization of the working fluid as well as the sensible heat. As a result, the effective thermal conductivity is higher than that of the conductors. An experimental study on three turn closed loop pulsating heat pipe with three different working fluids viz., Acetone, Methanol, Heptane and distilled water were employed. The PHP is made up of brass material with an inner diameter of 1.95mm, with a total length of 1150 mm for different fill ratios (FR) was employed .The PHP is tested for the thermal resistance and the heat transfer coefficient. The experimental result strongly demonstrates that acetone is a better working fluid among the working fluids considered in terms of higher heat transfer coefficient and lower thermal resistance.

Abstract: Depletion of fossil fuels, unaffordability of conventional fuels (petrol, diesel) and atmospheric pollution lead researchers to develop alternative fuels. Fuels derived from renewable biological resources used in diesel engines are known as biodiesel. Biodiesel is environmental friendly liquid fuel similar to petrol and diesel in combustion properties. Increasing environmental concern, diminishing petroleum reserves and agriculture based economy of our country are the driving forces to promote biodiesel as an alternate fuel. Hydrogen seems to be viable fuel to meet sustainable energy demand with minimum environmental impact. Hydrogen has high calorific value and clean burning characteristics which makes it effective fuel for future. It was found that hydrogen usage reduce emissions such as CO₂ and HC. India is one of the largest producers of neem oil and its seed contains 30% oil content. It is an untapped source in India, so the neem oil usage will be a best option. The investigation made on pure neem oil and neem oil with hydrogen addition at different flow rate (2 lpm & 4 lpm) in CI engines. The result shows that, brake thermal efficiency of neem oil with 4 lpm hydrogen was increased to 7.98% compare to pure neem oil at 4 Nm torque and fuel consumption of neem oil with 4 lpm hydrogen was decreased to 13.49% compared to pure neem oil at 4 Nm torque.

Abstract: In the present work of experimental investigation, the heat transfer performance of Spiral Tube Heat Exchanger (STHE) is studied by manufacturing the heat exchanger. STHEs are known as excellent heat exchanger because it is compact in size and having high heat transfer ability. The STHE consists of copper coils in the spiral shape and placed inside the shell which is made of Stainless Steel. The spiral shape coil is made by bending the straight copper tube of 10 mm inside diameter. The heat exchanger uses 3 such spiral coil brazed with straight header tube of 25 mm inside diameter and at a distance of 15mm apart, the number of turn in a spiral coil is four. Pump is used for circulation of water in both circuits. Cold water is circulated through spiral coil which entered at the periphery and comes out from centre; hot water is entered at the bottom centre of shell and comes out from the top of the shell. The inlet temperature range of hot water and cold water is 50 to 80°C and 30 to 48°C. Mass flow rate range of hot water and cold water is from 0.0633 kg/s to 0.0833kg/s and 0.01 kg/s to 0.0833kg/s.

Abstract: The present work concerns with the evaluation of performance and emissions characteristics of CI engine using cottonseed based biodiesel (B20) with fuel additive EMDFA200 at different concentration levels. In the experimental work it was observed that addition of EMDFA200 as additive improved the performance of CI engine and reduced the emission levels of NOx, CO, HC. Tests were also conducted the effect of inlet air preheating and results shows the significant improvement in the engine performance and reduction in the emission levels. Better performance and emission levels observed when the engine runs at air inlet temperature of 70°C

Abstract: An Experimental investigation is conducted to establish the feasibility of using Jatropha biodiesel in Direct Injection Compression Ignition (DICI) engines. While the biodiesel has certain limitations and adverse in terms of poor performance and high level of pollutants in the exhaust of the gases, specified chemical (Propylene Glycol, C₃H₈O₂) and nano(Al₂O₃) additives are used with Jatropha biodiesel. The experiments are conducted in two phases by using an experimental test rig, which consists of a DICI engine, electric loading device, data acquisition system, and AVL exhaust gas analyzers. In the first phases of experimentation, the performance and emission characteristics of the engine are analyzed by using neat diesel and Jatropha biodiesel and in the second phase of investigation, similar experiments are conducted by using chemical and nanoadditives blended biodiesel. The results of biodiesel are compared with those of neat diesel and it is seen that the performance and emission characteristics of the engine are inferior in the case of biodiesel when compared with neat diesel. However, the results revealed that the working characteristics could be improved by selecting of proper chemical and nanoadditives in right proportions.

Abstract: An experimental investigation on the performance, emission and combustion characteristics of single cylinder water cooled diesel test engine was carried out at a constant speed of 1500 rpm with processed waste engine oil. The experiments were carried out at different load conditions from no load to 110% load. To compare the results obtained the baseline readings were taken with diesel. The standard operating condition of the engine was 200 bar injection pressure and 23° before Top Dead Center (bTDC). For processed Waste Engine Oil (pWEO) fuel operation the Brake Thermal Efficiency (BTE) obtained at rated load point was 32.18 %. at 100 % load and pWEO gave a peak pressure of 64.46 bar compared to 66.12 bar for diesel. There was a 5 % reduction in the Nitrous Oxide (NO) emission with pWEO. Heat release rate (HRR) and exhaust gas temperature showed considerable reduction with pWEO fuel operation.

Abstract: Braking system is one of the important systems in Automobiles. It is essential to decelerate the vehicle and stop it when essential. The temperature of the brake pad (stator) and disc (rotor) increases because of frictional force between them. Higher temperatures may lead to brake fading or failure of braking system. In the present study droplet cooling of commercially available Brake pad is analyzed with surface temperatures in the range of 80°C - 150°C. The brake pad material analyzed is a composite material with Fe₂O₃, BaO, CaO, SiO₂, SO₃ and MgO as major constituents. The percentage of the constituents are found using Scanning Electron Microscope (SEM). The brake pad is artificially heated using cartridge heater and a fixed volume of water is dropped on to the brake pad surface using a syringe pump. The characteristics of droplet on the surface of the brake pad are recorded using a High speed camera. The temperature is measured continuously using a K type thermocouple and is recorded using an online data acquisition system. The characteristic of droplet enhanced cooling is presented.

Abstract: The present work deals with the results of the experimental investigations carried out on augmentation of turbulent flow heat transfer in a horizontal circular tube by means of tube inserts, with air as working fluid. Experiments were carried out initially for the plain tube (without tube inserts). The Nusselt number and friction factor obtained experimentally were validated against those obtained from theoretical correlations. Secondly experimental investigations using three kinds of tube inserts namely Rectangular bar with diverging conical strips, Rectangular bar with converging conical strips, Rectangular bar with alternate converging diverging conical strips were carried out to estimate the enhancement of heat transfer rate for air in the presence of inserts. The Reynolds number ranged from 8000 to 19000. In the presence of inserts, Nusselt number and pressure drop increased, overall enhancement ratio is calculated to determine the optimum geometry of the tube insert. Based on experimental investigations, it is observed that, the enhancement of heat transfer using Rectangular bar with converging and diverging conical strips is more effective compared to other inserts. Key words: Heat transfer, enhancement, turbulent flow, conical strip inserts, friction factor, pressure drop.

Abstract: In this paper, effect of nucleation site size on bubble dynamics during nucleate pool boiling heat transfer in saturated water is studied experimentally. Single bubble was generated using right angle tip of a hypodermic needle as a nucleation site. The hypodermic needles were used of inner diameters 0.413mm, 0.514mm, and 0.603 mm with a constant depth of 25mm. The bubble dynamics was studied using SONY Cyber-shot DSC-H100 camera operating at 30 frames per second at atmospheric pressure and at a wall superheat of 5K. The results show that, bubble diameter, bubble height and bubble volume increases with increase in diameter of nucleation site. The bubble growth period is found to be dependent on nucleation site size, and it decreases with increase in diameter of nucleation site. This happens because as volume of vapor bubble increases, buoyancy force starts dominates the capillary force and bubble detaches earlier. Effect of nucleation site size on bubble departure diameter and bubble release frequency is also discussed.

Abstract: The addition of additives to the water is known to enhance boiling heat transfer. In the present investigation, boiling heat transfer coefficients are measured for Nichrome wire, immersed in saturated water with & without additive. An additive used is 2-Ethyl 1-Hexanol with varying concentrations in the range of 10-10000 ppm. Extensive experimentation of pool boiling is carried out above the critical heat flux. Boiling behavior i.e. bubble dynamics are observed at higher heat flux for nucleate boiling of water over wide ranges of concentration of additive in water. Results are encouraging and show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient considerably higher, and that there is an optimum additive (500-1000ppm) concentration for higher heat fluxes. An optimum level of enhancement is observed up to a certain amount of additive 500-1000ppm in the tested range. Thereafter significant enhancement is not observed. This enhancement may be due to change in thermo-physical properties i.e. mainly due to a reduction in surface tension of water in the presence of additive.