Optimization of a solar air heater with phase change materials: Experimental and ‎numerical study

In this paper, a solar air heater (SAH) with phase change material (PCM)-based energy storage is ‎investigated. Paraffin was placed underneath the absorber plate as the PCM. A transient two-‎dimensional laminar model was used in the Ansys Fluent 17 software to study the effects of different ‎parameters on the performance of the SAH, such as the air mass flow rate, the amount of paraffin, and ‎the thermal conductivity of the paraffin. The performance of the SAH was optimized by considering ‎two objectives simultaneously: thermal energy efficiency and maximum nocturnal temperature ‎difference between the inlet and the outlet of the SAH. To validate the numerical model, a SAH with ‎a 2-cm paraffin layer and the same dimensions as the numerical model was built and tested. The ‎results of the simulation showed good agreement with the experimental results.

Effect degree of temperature subcooling in the performance of refrigeration with CFC, HFC and hydrocarbons refrigerant

Global warming is the result of the use of Chloro Fluoro Carbon (CFC) and Hydro Flouro Carbon (HFC) refrigerants. CFC and HFC refrigerants are not environmentally friendly in air conditioning systems. Researchers conducting the research to find an alternative refrigerant with hydrocarbon and the use of liquid suction heat exchanger (LSHX) subcooling in the vapor compression refrigeration system. One kind of LSHX is heat exchanger between tube to tube. Retrofit refrigerant is used to find a replacement refrigerant for R22, R134a, R404A with R600, and mixture refrigerant R290/R600a in the ratio 50:50. From the analysis are conclude that the increases of degree of subcooling temperature significantly affects to the effectiveness of LSHX, increase the refrigeration capacity and also refrigeration capacity index, increase the compressor of work, compressor work of index, COP and COP index. The parameters of the indicators that mixture the refrigerant R290/R600a in the ratio of 50:50 can be used as a substitution for R404A and R22, while the R600 refrigerant can be used as a substitution for R134a in the vapor compression refrigeration system with LSHX

Study of Seasonal Heat, Freshwater, and Volume Transports in the Gulf of Thailand using an Ocean Circulation Model

This research aims to investigate volume, heat, and freshwater transports in the Gulf of Thailand for each season. The Model grid used in this research is the orthogonal curvilinear grid which is constructed via cubic splines and solving Laplace's equation. For the vertical grid, the sigma coordinate is introduced to deal with significant topographical variability. The data used consist of bottom topography, current velocities, potential temperature, salinity, and seawater density, which are calculated from the primitive equations. The results show that the highest and lowest values of volume, heat, and freshwater transports in each season occur at the same region, and the direction of volume and heat transports are all same in the Gulf of Thailand, but the freshwater transport is in the opposite direction of volume and heat transports. The highest values of volume, heat, and freshwater transports occur between latitudes 7°N to 8°N in the winter and at the connection section between the Gulf of Thailand and the South China Sea in the summer, rainy season, and the end of the rainy season.  Their lowest values occur at latitude 11°N in the winter, between latitudes 8°N to 9°N in the summer, and between latitudes 10°N to 11°N in the rainy season and the end of the rainy season. In order to validate the results, a comparison was made with the results of Wyrtki's research which investigated the volume transports of Southeast Asian Waters. It can be summarized that the results of our research are on track

Effect of the Use of Natural Gas-Diesel Fuel Mixture on Performance, Emissions and Combustion Characteristics of a Compression-Ignition Engine

A compression ignition engine with a mechanical fuel system was converted into common rail fuel system by means of a self-developed electronic control unit. The engine was modified to be operated with mixtures of diesel and natural gas fuels in dual-fuel mode. Then, diesel fuel was injected into the cylinder while natural gas was injected into intake manifold with both injectors controlled with the electronic control unit. Energy content of the sprayed gas fuel was varied in the amounts of 0% (only diesel fuel), 15%, 40%, and 75% of total fuel’s energy content. All tests were carried out at constant engine speed of 1500 r/min at full load. In addition to the experiments, the engine was modeled with a one-dimensional commercial software. The experimental and numerical results were compared and found to be in reasonable agreement with each other. Both NO x and soot emissions were dropped with 15% and 40%, respectively, energy content rates in gas–fuel mixture compared to only diesel fuel. However, an increase was observed in carbon monoxide emissions with 15% natural gas fuel addition compared to only diesel fuel. Although smoke emission was reduced with natural gas fuel addition, there was a dramatic increase in NO x emissions with 75% natural gas fuel addition

Heat Transfer Performance of a Glass Thermosyphon Using Graphene-Acetone Nanofluid

This study presents an enhancement in the heat transfer performance of a glass thermosyphon using graphene-acetone nanofluid with 0.05%, 0.07%, and 0.09% volume concentrations. The heat load is varied between 10 and 50 W in five steps. The effect of heat load, volume concentration, and vapor temperature on thermal resistance, evaporator and condenser heat transfer coefficients, are experimentally investigated. A substantial reduction in thermal resistance of 70.3% is observed for the maximum concentration of 0.09% by volume of graphene-acetone nanofluid. Further, an enhancement in the evaporator heat transfer coefficient of 61.25% is observed for the same concentration. Also from the visualization study the different flow patterns in the evaporator, adiabatic, and condenser regions are obtained for acetone at different heat inputs