A Computer Analysis of Energy Use and Energy Conservation Options for a Twelve Story Office Building in Austin, Texas

The energy use of the Travis Building at Austin, Texas was analyzed using the DOE 2.1B building energy simulation program. An analysis was made for the building as specified in the building plans and as operated by the personnel currently occupying the building. The energy consumption of the building was compared with the energy consumption of the building modified to comply with the proposed ASHRAE 90.1p standards. The base design and the ASHRAE design of the Travis building were evaluated in Brownsville, Houston, Lubbock, and El Paso to study the influence of the weather on its energy consumption. In addition, a glass with high reflectivity and low overall heat transfer coefficient was used to study the reduction of glass conduction and glass solar loads. Finally, the energy consumption of the modified building was compared with the energy consumption of the modified building which conformed to the California energy standards

Effects of nanoparticle types on carbon dioxide foam flooding in enhanced oil recovery

Enhancement of foam stability has been recently evidenced with addition of nanoparticles (NPs), especially in the case of CO2 foams. Stabilized foams via solid NPs can potentially withstand high reservoirs temperatures. Studies have been conducted to examine the effect of NPs on foam stability; however, more research is required for various types of NPs. Therefore, the authors aimed to investigate the performance of silicon dioxide (SiO2), aluminum oxide (Al2O3), copper oxide (CuO), and titanium dioxide (TiO2) of different sizes in the presence of fixed concentration of anionic surfactant (AOS) on foam stability. Nano particle concentrations of (0.1 wt%, 0.3 wt%, 0.5 wt%, and 1 wt%) were used to investigate the foam stability, displacement test were performed to determine oil recovery at the optimum concentrations for each nanoparticle. The stability of the aqueous foam was evaluated by the Ross-Miles method using half-life measurements. All experiments were conducted at room temperature and pressure. The results revealed that all different NPs used were able to improve the stability of CO2 foam at certain concentrations. However, aluminum oxide NPs showed better results compared to others in terms of foam stability and half-life time. In addition, 0.1 wt% of all NPs types gave the highest foam stability and half-life time. In conclusion, a low concentration of NPs is recommended regardless of type for improving form stability

Experimental investigation of the effect of drill pipe rotation on improving hole cleaning using water-based mud enriched with polypropylene beads in vertical and horizontal wellbores

Field experience has shown that the inefficient transport of small cuttings is a main factor contributing to excessive drag and torque during the drilling of a deviated hole; however, very little is known about the transport behavior of small cuttings. This experimental study investigates the effect of different polypropylene bead concentrations in water-based mud (WBM) on hole cleaning, along with the effects of cutting size, drill pipe rotation, and hole inclination angle. A total of 160 runs were performed using an experimental rig consisting of a 13 ft (3.96 m) long casing with a 2 in (50.8 mm) Inner Diameter (ID) and a rotary inner pipe with a 0.8 in (20 mm) Outer Diameter (OD). Four cutting size ranges, namely, 0.5–1.0 mm, 1.0–1.4 mm, 1.4–1.7 mm, and 1.7–2.0 mm, with a density of 2400 kg/m3 were tested in WBM with varying polypropylene bead concentrations ranging from 0 to 8 ppb. The concentric annulus flow test section was changed to vertical and horizontal angles with pipe rotation from 0 to 150 rpm. The mud density and viscosity were maintained at 10 ppg and 16 cp, respectively, under a flow velocity of 3.48 m/s (Reynolds number of 6620). The results indicate that smaller cuttings are easier to transport at all pipe rotations and polypropylene bead concentrations in both vertical and horizontal holes. The optimal pipe rotational speed was found to be 60 rpm. In this study, polypropylene beads undeniably enhanced the mud carrying capacity by significantly increasing the cutting transport ratio (CTR) by up to 16.57% in vertical holes and 15.73% in horizontal holes

Improving the performance of oil based mud and water based mud in a high temperature hole using nanosilica nanoparticles

Oil-based mud (OBM), a non-Newtonian fluid, is known for its superior performance in drilling complex wells as well as combating potential drilling complications. However, the good performance may degrade under certain circumstances especially because of the impact of chemical instability at an elevated temperature. The same phenomenon occurs for water-based mud (WBM) when it is used in drilling under high temperature conditions. To prevent this degradation from occurring, numerous studies on utilizing nanoparticles to formulate smart fluids for drilling operations are being conducted worldwide. Hence, this study aims to evaluate the performance of nanosilica (NS) as a fluid loss reducer and a rheological property improver in both OBM and WBM systems at high temperature conditions. This study focuses on the impacts of different nanosilica concentrations, varying from 0.5 ppb to 1.5 ppb, and different mud weights of 9 ppg and 12 pg as well as different aging temperatures, ranging from ambient temperature to 300 °F, on the rheological performance of OBM and WBM. All the rheological properties are measured at ambient temperature, and additionally tests, including lubricity, electrical stability, and high-pressure high-temperature filtration measurements, are conducted, and rheological models are obtained. The performance of nanosilica is then studied by comparing each of the nanosilica-enhanced mud systems with the corresponding basic mud system, taking the fluid loss and rheological properties as the benchmark parameters. Nanosilica shows a positive impact on OBM and WBM, as the presence of nanosilica in the mud systems can effectively improve almost all their rheological properties

A new nonlinear HEMT model for AlGaN/GaN switch applications

International audienceWe present here a new set of equations for modeling the IV characteristics of Field Effects Transistors (FETs), particularly optimized for AlGaN/GaN HEMTs. These equations describe the whole characteristics from negative to positive breakdown loci, and reproduce the current saturation at high level. Using this model enables to decrease the modeling process duration when a same transistor topology is used for several applications in a T/R module. It can even be used for switches design, which is the most demanding application in terms of IV swing. Moreover, particular care was taken to accurately model the first third orders of the current derivatives, which is important for multione applications. We also focused on an accurate definition of the nonlinear elements such as capacitances for power applications. There are 18 parameters for the main current source (and six for both diodes Igs and Igd). This can be compared to Tajima's equations-based model (13 parameters) or to the Angelov model (14 parameters), which only fit the IV characteristics for positive values of Vds. We will detail here the model formulation, and show some measurements/modeling comparisons on both IV, S-parameters and temporal load-pull obtained for a 8 75 m GaN HEMT, with 0.25 m gate length