Mathematical model for optimising the performance of a ground source heat pump.

Energy demand for the twenty first century is expected to increase many fold along with corresponding diversification of energy sources and generation methods. Of the many energy sources available, use of Ground Source Heat Pump (GSHP) system is the focus of the analysis in this research. This work is carried out to identify the key parameters which affect the performance of the GSHP system. A mathematical model has been developed to understand the complex operation of the heat pump under typical working conditions. Individual sub-systems, such as Ground Heat Exchanger (GHE), evaporator, condenser, compressor and radiator are modelled in MathCAD and coupled together and solved simultaneously. The performance of the system is predicted while varying air temperature, power input to the compressor and the ground temperature beneath the earth's surface. In addition a special sub-model was developed for the single vertical U-tube GHE in FLUENT, a Computational Fluid Dynamics (CFD) software, to calculate the overall heat transfer coefficient for varying outer surface temperature of the borehole.The overall system results are validated against the published results with the system operating range of 18°C to 33°C with around 10 percent deviations. It is determined that the COP of the system increases with surface area and overall heat transfer coefficient (OHTC) of the heat exchanger. An increase in up to 500 m2 surface area, steep raise of COP from 10.05 to 10.3 is observed. Similarly increase of 10 W/m2K of OHTC has steep COP rise from 10.05 to 10.28. The temperature gradient across the system also has influence on its operating performance, where a 15°C increase in the ground temperature for cooling mode reduces the COP by around 5%. Finally the degree of refrigerant sub-cooling has a positive effect, for every 5°C temperature drop the COP improves by 0.5 similarly for degree of super-heating, COP improves by 0.25. Scope for performance enhancement for GSHP is investigated by tuning operating conditions. The effect of operating variables to the sensitivity of performance of heat pump is also determined

Effect of Temperature and Strain rate on Flow behavior of Al0.3CoCrFeNi HEA

High-entropy alloys (HEAs) are currently attracting much interest because they offer unique properties and good ductility at low temperatures. These materials are of interest primarily because they contain five or more principal elements, with each element having a concentration between 5 and 35 at. %, and yet they have very simple structures based on solid solution phases. Super plasticity is major concern for forming industries to fabricate complex and curves components, to use in automotive, aerospace and other application. In addition to that, the materials used in automobile and other structural applications often encountered with shock loadings. Recent experiments have shown that the HEAs also have a potential for exhibiting superplastic property when testing at elevated temperatures. Since super-plasticity requires a very small grain size, typically < 10 μm, it is feasible to introduce significant grain refinement by thermomechanical processing. The main aim of this work is to develop Al0.3CoCrFeNi high entropy alloy with very fine equi-axed stable grain microstructure using proper thermomechanical treatment. Study the deformation behavior both at room and high temperature. Explore the possibility of super plasticity. Further, study the effect of temperature and strain rate on the deformation behavior

Balanced double aortic arch with tetralogy of Fallot

AbstractWe present a rare case of balanced double aortic arch in a 19year old cyanotic boy, a known case of tetralogy of Fallot. This was suspected on chest X-ray and confirmed on further imaging by cardiac catheterization and computed tomography. We discuss the clinical and surgical implications of this condition

Characterization and in-vitro cytotoxicity of lupeol isolated from leaf extract of ficus mysorensis

Medicinal plant extracts gain more attention in research of modern medical sciences due to their non-lethal activity. The use of traditional medicine practices from plants has been accepted as a main sources for drug discovery in various health disorder especially cancer. Ficus mysorensis has a long history of usage as traditional medicine. The leaf extract of this plant possess phytochemicals such as alkaloids, flavonoids, terpenoids, steroids, saponins, Phenolics and glycosides. The ethanol leaf extract has been subjected to compound isolation and confirmed by GCMS, HPLC Chromatogram, 13C and 1H nuclear magnetic resonance (NMR), IR spectra. Based on spectral studies the isolated compound confirmed that Lupeol. Lupeol compound was evaluated against MCF-7 cell lines by MTT assay. Lupeol induced an effective change in the cell viability of MCF-7 cells with IC50 concentration (198.75 g/ml). Induction of cell death, change in cell morphology and cancerous cells population was observed in the treated cells, but the normal cells was not affected

Cor triatriatum and coronary artery fistula in tetralogy of Fallot

Coexistence of divided left atrium with tetralogy of Fallot is rare. Preoperative diagnosis of this rare association is difficult. We here report preoperative diagnosis of this rare combination. In addition, the patient also had coronary to left ventricle fistula

Racing heart and pounding neck: Classic clinical sign revisited

The present report describes “Frog sign” due to prominent jugular pulsations in the neck. This is seen in case of paroxysmal atrioventricular nodal reentrant tachycardia

Influences of Post-Heat Treatment on the Microstructure Evolution and Creep Properties of Ni-Based Superalloy IN718 Fabricated by Electron Beam Melting

In this study, the Ni-based superalloy IN718, fabricated using an electron beam melting process, was investigated in as-built and various heat-treated conditions. The relationships between the microstructure characteristics and creep properties were elucidated. Under testing conditions of 650 &deg;C and 650 MPa, the direct-aged specimen exhibited the lowest steady-state creep rate, at 0.15 &times; 10&minus;8 s&minus;1. The superior creep resistance can be attributed to the higher volume fraction of &gamma;&rsquo;/&gamma;&rdquo;-strengthening precipitates within the grain and fine &delta; precipitates along the grain boundaries. Being coherent to the &gamma; matrix, the nano-sized &gamma;&rsquo;/&gamma;&rdquo; precipitates effectively hindered the dislocation motion in the grain interior. In addition, controlled grain boundary &delta; precipitates inhibited grain boundary sliding and decelerated the steady-state creep strain rate during creep deformation

Yttrium’s Effect on the Hot Cracking and Creep Properties of a Ni-Based Superalloy Built Up by Additive Manufacturing

We studied the effects of the rare earth element yttrium (Y) on the hot cracking and creep properties of Hastelloy-X processed by selective laser melting. We used two different alloys to study hot cracking in Hastelloy-X: one with 0.12 mass% yttrium added and one with no yttrium. Y-free Hastelloy-X exhibited less cracks, mainly due to the segregation of Si, W, and C resulting in SiC- and W6C-type carbides at the grain boundary and interdendritic regions. On the other hand, more cracks formed in the Y-added Hastelloy-X specimen because of segregation of Y, resulting in the formation of yttrium-rich carbide (YC). Post-heat treatment was conducted at 1177 °C for 2 h, followed by air cooling, to obtain good creep properties. We carried out a creep test along the vertical and horizontal directions. Despite having more cracks, the Y-added as-built Hastelloy-X specimen showed longer creep life and ductility than the Hastelloy-X specimen. This was mainly because of the formation of Y2O3 and SiO2 inside the grains. After solution treatment, the Y-added specimen’s creep life was eight times longer than that of the Y-free solution-treated specimen. This was mainly because of the maintenance of the columnar grain morphology even after solution treatment. In addition, the formation of M6C carbides, Y2O3, and SiO2 improved creep life. To summarize the effect of Y, Y addition promoted the formation of cracks, which brought about creep anisotropy; however, it improved creep properties through the stabilization of oxygen and the promotion of discrete carbide precipitation, which prohibited the migration and sliding of grain boundary