Applied Mechanics and Materials Vol. 787

Abstract: An indirect type solar dryer is fabricated with the components like evacuated tube collector, drying chamber and blower. The performance of the drier is evaluated by carrying out drying experiments with copra at Coimbatore district Tamilnadu, India. A short survey of these showed that applying the indirect type solar dryer not only significantly reduced the drying time but also resulted in many improvements in the quality of the dried products. The temperature of the drying chamber ranges from 55°C to 75°C while the ambient temperature ranges from 28°C to 38°C. Nine basic solar drying models were used to fit the experimental data of copra. For experimental results, the logarithmic model showed the best curve fitting with highest correlation coefficient (R²⁾ and lowest value of RMSE (Root Mean Square Error). Solar dried copra obtained is free from smoke, dust, bird and rodent damage.

Abstract: Automotive radiators use flattened tubes within which Ethylene Glycol (EG) and Water (W) based nanofluids flow to enhance the heat transfer. Computations were carried out to understand the flow and thermal characteristics of the Aluminium oxide based nanofluids, with EG:W ratio of 60:40 as the base fluid, flowing inside a flattened tube. The flow was maintained in the turbulent regime with the Reynolds number (Re) ranging from 5,000 to 14,000.Investigations were carried out for nano particle concentrations (φ) varying from 1% to 5% of the base fluid by volume. Computations were also carried out for a circular tube to study the influence of tube shape. The nanofluid with φ = 5% increased the Nusselt number values by 40% for the flattened tubes compared to the base fluid at Re =14,000. These estimates are done at constant flow Reynolds number in-line with literature, which necessitated increased inlet velocity, which meant increased pumping power. Pumping power increased with increase in φ and Re. For a constant pumping power per unit length (P_p) of 5W/m the values of average heat transfer coefficient () decreases with increase in φ. The values of for the 2% and 5% nano fluid were lower than the base fluid by 6% and 23.8% respectively. Nanofluid with φ = 1% alone showed a 1.2% higher value than the base fluid indicating the need of further exploration of φ in a closer range.

Abstract: A solar chimney power plant (SCPP) sometimes also called 'solar updraft tower' is a part of the solar thermal group of indirect solar conversion technologies, utilizing a combination of solar air collector and central updraft tube or chimney to generate a solar induced convective flow which drives pressure staged turbines to generate electricity. In this paper the performance of a solar chimney power plant (SCPP) is evaluated if established in the Kota region of Rajasthan in India. Kota has high intensity of solar radiation with more than 270 sunny days in a year. To investigate the theoretical performance evaluation of the solar chimney power plant in Kota region, total energy generation and average power output for every ten minute interval has been calculated on the basis of solar radiation and temperature data provided by Centre for wind energy Technology (C-WET) available for the period from June 2011-May 2012 for every ten minute interval. Subsequently day wise and month wise calculations have been performed for energy generation and power output for the year June 2011 - May 2012. Further, annual average power output of SCPP is calculated at Kota for different sets of dimensions of SCPP and assuming different values of collector efficiency. Power produced at the plant established in Kota region is compared with power output estimated by J. Schlaich by their experience gained from prototype of SCPP in Manzanares, Spain. Land area required for solar chimney power plant if installed in Kota region of Rajasthan India is calculated for 200 MW capacity plant.

Abstract: The environment we live in is very fragile and has a delicate balance. In the current era, the human kind is consuming the natural resources at a higher rate than it can produce it and is generating wastes at a higher rate than the environment can remove it. Because of anthropocentric ideology, human race believes in development through destruction. The urge for luxury and sophistication has given an impetus to industrial revolution and technological development. This has lead to exponential consumption of resources of the world. To worsen this scenario, the world has undergone huge population explosion in the 19^th century. This has increased pressure on all available resources. Hence, in order to meet the current demands, people started using unsustainable technologies leading to huge pollution in all sectors. In this paper, the adverse effect of population growth in India on various factors like water pollution, emissions of CO₂ and green house gases are discussed. The data for analysis are based on the statistics of United Nations Population Division, The WorldBank data bank and Central Pollution Control Board of India.

Abstract: Wastewater is a very turbid liquid with an offensive smell in most cases. Its composition varies from large floating or suspended solids to smaller suspended solids, very small solids in colloidal form and chemical impurities as dissolved substances. This makes the treatment complicated and hence it is essential to adopt more than one type of treatment method. It is a common practice to carry out cost effective pre treatment to make the actual treatment less tedious and more effective. Chemical impurities such as sulphides, sulphates, chloride, oil and greases are usually found at the second stage of tannery effluent. The pH of tannery effluent ranges from 5.5 to 10. This work explores common herbs as a viable pre treatment option for non – chromium tannery effluent.

Abstract: The applications of heat exchangers are vast and the enhancement of heat transfer and compact size are the key factors for designing the heat exchangers in order to achieve energy savings. In the field of tubular heat exchangers one of the possible ways for reducing the space occupied by the exchanger is by bending tube axis in helical shape. This option is particularly suitable when construction simplicity is needed and the geometry of the place in which the exchanger has to be housed is the cylindrical one. In this paper, an attempt is made to enhance the heat transfer rate without application of any external power. This is achieved by providing the helical tube in tubes. The parameters influencing the nature of flow in a helical coil heat exchanger are the tube geometry namely pitch coil diameter, pitch and tube diameter. CFD analysis is carried out to study these geometry effects on heat transfer and hydraulic characteristics by varying Reynolds number (hot fluid). The CFD results of velocity and temperature distribution in the heat exchanger are used to estimate the Nusselt number and heat transfer coefficient. This helps to arrive at an optimum value of Reynolds number and Nusselt number for the corresponding tube-to-coil diameter ratios.

Abstract: In the present work a transient numerical model is developed to investigate and predict the performance of a paraffin phase change material (PCM) in the annular portion of the cylindrical container during its solidification and melting processes. Enthalpy method of modeling is adopted and the discretised non-dimensional form of governing equations and boundary conditions are solved by implicit finite difference method by using MATLAB software. The temperature variation of PCM along two axes of the polar co-ordinates (r, z) and the time required for solidification are analyzed and presented. The effect of system variables on the performance of the Latent Heat Thermal Energy system ( LHTES) is studied. The model tested finds application in the concept of free cooling which is the process of storing the coldness of the night time ambient air in the LHTES in order to cool the building during the daytime by retrieving the stored cold energy.

Abstract: In this study the conventional still is modified with cotton cloth at the inner wall surfaces to improve the performance of the still. The main purpose of this experimental study is to make use of the heat available on the inner wall surfaces of a basin by using cotton cloths. Two single-slope solar stills with the same area of 1mx0.5m are fabricated and tested. The hourly amount of extracted distilled water, the various temperatures and the insolation were observed for one month period (April 2014). The results were performed by comparing with conventional solar still and cotton cloth still. The experimental results clearly shows that, by reducing transfer of heat from inner surfaces to the outer surfaces with the help of cotton cloth the modified still gives yield about 13.3% higher than the conventional still.

Abstract: Global warming and climate change are the foremost environmental challenges facing the world today. It is our responsibility to minimize the consumption of energy and hence reduce the emissions of greenhouse gases. Companies choose ‘Carbon Footprint’ as a tool to calculate the greenhouse gas emission to show the impact of their activities on the environment. In this working paper, we assess the carbon foot print of an educational institution and suggest suitable measures for reducing it. Greenhouse gas emitting protocol for an academic institution in terms of tones of equivalent CO₂ per year is projected using three basic steps includes planning (assessment of data’s), calculation and estimation of CO₂ emitted. The estimation of carbon foot print is calculated by accounting direct emission from sources owned/controlled by the educational institution and from indirect emission i.e. purchased electricity, electricity produced by diesel Generator (DG), transport, cooking (Liquefied Petroleum Gas) and other outsourced distribution. The CO₂ absorbed by trees are also accounted. Some of the options are identified in order to reduce CO₂ level. The information of corporate carbon footprint helps us identifying the Green House Gases (GHG) emission “hot spots” and identifies where the greatest capacity exists in order to reduce the GHG emissions. The main prioritization goes to transport and then followed by DG, cooking and then electricity. The per capita CO₂ emission and the total CO₂ emission for a typical educational institution are estimated.

Abstract: Dispersing small amounts of solid nano particles into base-fluid has a significant impact on the thermo-physical properties of the base-fluid. These properties are utilized for effective capture and transportation of solar energy. This paper attempts key idea for harvesting solar energy by using alumina nanofluid in concentrating parabolic trough collectors. An experimental study is carried out to investigate the performance of a parabolic trough collector using Al₂O₃-H₂O based nanofluid. Results clearly indicate that at same ambient, inlet temperatures, flow rate, concentration ratio etc. hike in thermal efficiency is around 5-10 % compared to the conventional Parabolic Trough Collector (PTC). Further, the effect of various parameters such as concentration ratio, receiver length, fluid velocity, volume fraction of nano particles has been studied. The different flow rates employed in the experiment are 2 ml/s, 4 ml/s and 6 ml/s. Volumetric concentration of 0.02%, 0.04% and 0.06% has been studied in the experiment. Surfactants are not introduced to avoid bubble formation. Tracking mode of parabolic trough collector is manual. Results also reveal that Al₂O₃-H₂O based nanofluid has higher efficiency at higher flow rates.