Natural Circulation loop (NCL) which is also called as a thermosyphon system is the heat transfer loop which uses no pump or external device to drive the loop fluid. In the present paper, a comparative study on thermal characteristics of two loop fluids viz. water and Al2O3/water nanofluid is made. Experiments are conducted on in-house designed test rig. Thermo-hydraulic behaviour of loop fluid is presented. Two parameters such as heat input, nanofluid concentration are varied in order to study their individual and combined effects. It is concluded that Al2O3/water nanofluid as loop fluid results in higher mass flow rates as compared to the water. Different derived quantities such as Nusselt number and Grashof number are calculated. Quantitative comparison is made between water and Al2O3/water nanofluid. Time to reach steady state is reduced by 22 % using Al2O3/water nanofluid as loop fluid when compared with water. Mass flow rate and Grashof number of the Al2O3/water nanofluid based NCL are enhanced by 6. 75% and 26% respectively, when compared with water-based NCL at 1000W heat input. At the heater, the temperature gradient is reduced by 30. 2% due to the improved thermal and transport properties of Al2O3/water nanofluid when compared with water at 1000 W heat input. As particle concentration increases from 1% to 5%, Nusselt number increases from 10. 1 to 20. 1, for the heat input of 1000W.

Recently closed loop pulsating heat pipes have been receiving much attention because of their potential applications in high heat flux micro-electronic systems. They work by self thermal driven oscillation without any mechanical parts. Though they are simple in structure, understanding of the heat transfer mechanism is highly complex having a strong thermo- hydro dynamic coupling governing their performance. In this paper, an experimental study on a closed loop PHP with a single turn has been conducted there by providing vital information regarding parameter dependence on its performance. The PHP is made of brass tube having an internal diameter of 2 mm and outer diameter of 3 mm. The parametric characterization has been done for the variation in internal diameter, fill ratio, working fluid and orientation of the device. The working fluids Acetone, Methanol, Ethanol and Propanol are considered for experimentation with volumetric filling ratios of 50%, 60%, 70% and 80%. Input heat power of 7 to 12 W is varied at the evaporator section. The CLPHP is also verified for its thermal performance at 00, 300 and 600 orientations. The transient and steady state experiments are conducted and operating temperatures are measured using K- type thermocouples. The results highlighted that the thermal performance of a PHP is strongly influenced by change in fill ratios, orientation and heat input.80% fill ratio yields an effective heat transfer rate for a horizontal mode of operation. Appreciable fluid movement and better heat transfer rate are observed for the 300 orientation of PHP operation. Acetone exhibits better heat transport capability compared to other working fluids in all orientations.

In this paper, a model for closed loop solar system is presented and an attempt is made to generalize the model to be utilized for primary design of any solar active thermal system. This model may be used for systems in which gas or a liquid are fluids that flow. Two new parameters, namely, the system heat delivery factor and the system heat absorption factor are introduced in the model. These two factors are fully discussed and some equations are developed for their determination.

Background: Heating at high temperatures creates a large change in the chemical properties of oils. Further research is necessary to choose the type and quality of the oil is due to its effects on health. Extra virgin olive oil is considered one of the best due to the beneficial effects of dietary oils. The aim of this study was to compare the thermal stability of extra virgin olive oil, Iranian and foreign.Methods: Eight samples of olive oil were tested in this study.oils were heated at 120oC for 4 h to evaluate the thermal stability, were sampled every 2 hours. Fatty acid composition, acid value, peroxide value, anisidine value, totox value, oxidative stability Rancimat, was conducted in accordance with Iranian national standards.Results: Results showed that oleic acid, the major fatty acid in olive oil, its value is between 69 to 74 percent. There was a significant relationship between time and acid value (P=0.013), peroxide value (P≤0.001), anisidine value (P≤0.001), totox value (P≤0.001). There is no significant relationship between changes in oil and acid value, peroxide value, anisidinevalue, But with totox value (P=0.003) a significant relationship was observed.Conclusion: Interpretation of the data suggests that the thermal process is changing the index of acidity, peroxide, anisidine and totox. The changes will further increase with time. The results will be receiving extra virgin olive oil external to the Iranian type features are better and are more resistant to heat.

The increase in demand for petroleum derivatives such as engine oil has contributed to not only the rapid and adequate response to them, but also attracting many managers and researchers to control their adverse environmental impacts. In this regard, this study unveils an optimization model to develop a closed loop supply chain network for engine oil in an uncertain environment. In the concerned model, in addition to addressing supply chain costs, adverse environmental effects are also minimized. To solve the proposed multi-objective model and acquire Pareto optimal solutions, the goal programming approach is deployed. The demand and amount of recyclable materials are considered to be imbued with uncertainty, which a robust optimization approach is devised to capture it. Likewise, new methods are taken into account to recycle engine oil, being capable of supporting both economic and environmental benefits. Lastly, a case study is utilized to evaluate and validate the presented model, through which outstanding management results are derived.

This paper presents the experimental investigations conducted on a vertical closed loop pulsating heat pipe (VCLPHP) to evaluate the thermal performance. The values of thermal resistance and heat transfer coefficient obtained in the experimentation is used as evaluation parameters. The VCLPHP used has capillary tubes having an inner diameter of 2mm and outside diameter 3mm and bent into 5 turns. The lengths of the evaporator, adiabatic and condenser sections are 50, 90 and 70mm, respectively. The binary mixture of fluids used are acetone – ethanol and ethanol-methanol mixtures. The thermal performance of these binary mixtures were then compared with conventional working fluids such as acetone, ethanol and methanol. The fill ratios was changed from 50 to 80% in steps of 10% and the heat inputs were varied between 60 to 90W in steps of 10W. However, the mixing proportions for all mixtures was maintained as 1: 1. All the experiments were conducted in the vertical position (90° ). The experimental results showed that, the overall performance of acetone was the best with the lowest thermal resistance and highest heat transfer coefficient as compared to all pure fluids and among fluid mixtures the acetone-ethanol mixture showed the best thermal performance.