Journal of Selected Topics in Energy

In this study, the performance and emission characteristics of a direct injection diesel engine using coconut oil biodiesel were investigated. For this aim, coconut oil was converted to its biodiesel via transesterification approach. Then, the effects of the biodiesel percentage in blend, engine load, and speed on brake power, brake specific fuel consumption (BSFC), nitrogen oxides (NOx), carbon dioxide (CO₂), carbon monoxide (CO), and particle matter (PM) have been considered. Fuel blends with various percentages of biodiesel (0%0 - %3%) at various engine speeds and loads were tested. The results indicated that blends of cocunut with diesel fuel provide admissible engine performance on the other side, emissions decreased so much.

Effect of open windows on car drag and consequently on the required power and fuel consumption has been investigated in this study. To do this, a simulated model as possible as similar to the actual model has been considered. For example round angles and side slopes have been considered. The drag caused by aerodynamic forces has been calculated, for different cases. Results show, as the percentage of windows opening increased, the car drag first decreased and then increased such that, the car drag with open windows for a certain percentage is equal to that of the closed windows car. This certain percentage depends on the car velocity.

The limited available energy resources and it basic role in industrial development, employing the renewable sources of energy including wind, sun, water and etcetera as appropriate choice described. Renewable energies are not only economically advisable, but even can contribute to provide a cleaner approach of energy production and healthier environment. Hence, assessment of some old structures such as Middle East wind catcher that are established on the ground of clean energies and adapting them to the modern age demands with optimizing models is noteworthy. This work, by keeping focus on calculus of variation and analysis of the wind load on the wind catcher structures and present an optimal more resistant model. Optimization of the design parameters of wind catcher structures led to a hyperbolic model with least wind catcher surface and a higher stability and strength compared with the older structures of this category.

Copper oxide nanofluid that is obtained by dispersion of copper oxide nanoparticles in water base fluid is used as heat pipe working fluid. Nanofluids because of having better thermophysical properties in comparison with conventional heat transfer fluids, cause heat pipe performance improvement as an effective heat transfer equipment. In this work, a computational fluid dynamic method (CFD) is used to study the effect of using nanofluid and varying volume fraction, size and shape of suspended nanoparticles in nanofluid on heat pipe thermal performance. The results show thermal resistance reduction and heat pipe performance improvement by using nanofluid in comparison with pure water. Also volume fraction enhancement, nanoparticle’s diameter reduction and using cylindrical nanoparticles cause the evaporator and condenser temperature gradient reduction that in low volume fractions the effect of using nanoparticles with small diameter on heat transfer is more than using non spherical nanoparticles

 Supersonic wind tunnels are strong and useful tools for the detection of the flow physics around flying vehicles. In this work, a blowdown type supersonic wind tunnel with a Mach number of 3 was studied. The required air for the tunnel was supplied by a storage tank containing compressed air. The intended velocity in the test section of the wind tunnel is provided by the high pressure discharge of the air from the storage tank into the atomosphere. The nozzle's geometry has been designed based on the "characteristics" method. Embedding the injector in the wind tunnel provides the opportunity to launch the wind tunnel at lower compression ratios. Since the duration of the experimental data collection is limited in blowdown supersonic wind tunnel, proper design and exploitation of the injector in a way to allow tunnel launching at decreased compression ratios, provides significant influence on the saving the compressed air of the storage tank and increasing the experiment duration. It has been attempted in this work to study the effect of installation of the injector in wind tunnel through assessing the boundary layer and the flow physics inside the wind tunnel. The results show that the injected flow increases the energy level of the low energy boundary layer, so as the energy of the boundary layer in a placed ahead of the injector location is higher than a place before the injector location. This fact results in a decreased required compression ratio for tunnel launching. The physics of the formed flow was studied and physical phenomena such as boundary layer separations, bow shock, barrel shock and mach disk were reported around the injection site 

In this paper, the impact of micro bubbles as the second phase in the turbulent flow inside the channel flow has been investigated. The developed turbulent flow inside channel containing micro bubbles has been solved using large eddy simulation. Numerical analysis has been done to survey the impact of micro bubbles on turbulent characteristics derived from carrier flow. Finally, the mechanism of reducing frictional drag force was illustrated. According to the results, increasing the volume fraction of bubbles in the constant diameter will decrease the frictional drag force. Also studying the energy spectrum showed that the energy in the small scales has increased and in the large scales decreased.

In this work thermal performance of a cylindrical heat pipe at steady state has been investigated empirically. The used heat pipe, made of copper, has been designed and manufactured by considering effective parameters on heat pipe thermal performance. Then heat pipe has been charged by water as the working fluid. By installing sensors and the other equipment, the test set up has been prepared. After preparing the test set up by changing voltage, various input powers have been inserted into evaporator and the heat pipe surface temperature distribution has been obtained for each case. Then by using the obtained temperature distributions, thermal resistance variations and equivalent thermal conductivity coefficient have been computed. and variation of them versus input power have been plotted. The results show that the thermal resistance has its minimum value at maximum operating limit (maximum passing power) and equivalent thermal conductivity has its maximum value at this point.
 

Nowadays, according to increasing energy consumption especially in industry, the need for optimizing energy consumption and determining energy efficiency class of different devices is essential. The main challenge of the present study is developing an energy label instruction for centrifugal pumps. Since the used standard in Iran (ISIRI 7817-2, 1st.edition) only considers the effect of efficiency in energy labeling, a new method is presented to modify this standard. In the proposed method the effect of specific speed on efficiency is considered by choosing one of the constant specific speed curves in η- Q diagram and modifying efficiency for each specific speed. Then, different pumps are tested and labeled by different standards. While the used standard in Iran labels all the pumps in one class, but the new proposed method can label pumps properly as European standards that show the benefit of using the proposed method in centrifugal pumps energy labeling.
 

In this paper, the optimal operation of pumping stations was determined using a genetic algorithm so that the minimum energy cost. The schedule for the operation of the water pump system can be a significant savings in the cost of energy to be achieved. Determine the optimum pump operation schedule an optimization model - simulation-based genetic algorithm was developed. The model integrates GA optimizer and EPANET hydraulic network solver in MATLAB. The proposed model is applied to find the optimal pump operation schedule of Dogonbadan water conveyance system from Kowsar Dam in an ordinary day of the year. The comparison of optimal schedule with ordinary operation strategy shows 26.8 percent reduction in total energy cost. This indicates the high capability of the proposed model.