A simple and compact arrangement for flash evaporation is described. It uses a cell phone vibrator for powder dispensing that can be incorporated into a vacuum deposition chamber without any major alterations. The performance of the flash... more
A simple and compact arrangement for flash evaporation is described. It uses a cell phone vibrator for powder dispensing that can be incorporated into a vacuum deposition chamber without any major alterations. The performance of the flash evaporation system is checked by making thin films of the optical memory chalcogenide glass Ge2Sb2Te5 GST. Energy dispersive x-ray analysis shows that the flash evaporation preserves the stoichiometry in thin films
The low-pressure oxidizer preflow during start-up of an upper-stage rocket engine is analyzed computationally. An iterative Euler-Lagrange approach is used to describe the three-dimensional two-phase flow of oxidizer vapour and spray... more
The low-pressure oxidizer preflow during start-up of an upper-stage rocket engine is analyzed computationally. An iterative Euler-Lagrange approach is used to describe the three-dimensional two-phase flow of oxidizer vapour and spray which is characterized by intense phase transfer. Multipoint injection and flash-atomization of liquid oxi-dizer is modelled by stochastic droplet injection according to injector locations and spray characteristics. Based on the framework of classical D 2-theory, a flash-evaporation model is developed to describe heat and mass transfer between superheated liquid droplets and vapour flow. The computed transsonic flow field agrees well with experimental characteristics such as pressure level and temperature decrease and further provides detailed local information on vapour flow homogeneity and liquid wall deposit.
19 Hybrid organo-lead halide perovskites are becoming the benchmark material for next generation 20 photovoltaics and a very important player for other applications such as photodetectors and light 21 emitting diodes. Nevertheless, the... more
19 Hybrid organo-lead halide perovskites are becoming the benchmark material for next generation 20 photovoltaics and a very important player for other applications such as photodetectors and light 21 emitting diodes. Nevertheless, the most important issue hindering the large-scale application of these 22 materials remains their intrinsic instability due to the organic cation. Although the substitution with 23 inorganic cesium (Cs) enhances stability, in most cases solution deposition methods of fully 24 inorganic perovskites result in high surface roughness and poor surface coverage. This work reports 25 on the evaporation of the CsPbBr3 precursor by single source thermal ablation, showing that just after 26 deposition films consist of a mixture of CsPbBr3, CsPb2Br5, and Cs4PbBr6 due to a vertical 27 composition gradient. We point out that mild post deposition treatments lead to the conversion of 28 CsPb2Br5 and Cs4PbBr6 into CsPbBr3 due to its higher thermodynamic stability. Conversion results 29 into smooth and pinhole-free CsPbBr3 films with good light absorption and emission properties. We 30 demonstrate the suitability of obtained films for planar devices by preparing perovskite-based pure-31 green light emitting diodes, thus promoting Single Source Thermal Ablation as a promising 32 alternative deposition technique for all-inorganic perovskite-based devices. 33
Exhaust hot water (EHW) is widely used for various industrial processes. However, the excess heat carried by EHW is typically ignored and discharged into the environment, resulting in heat loss and heat pollution. An organic Rankine cycle... more
Exhaust hot water (EHW) is widely used for various industrial processes. However, the excess heat carried by EHW is typically ignored and discharged into the environment, resulting in heat loss and heat pollution. An organic Rankine cycle (ORC) is an attractive technology to recycle heat from low-temperature energy carriers. Herein, ORC was used to recycle the heat carried by EHW. To investigate the energy and exergy recovery effects of EHW, a mathematical model was developed and a parametric study was conducted. The energy efficiency and exergy efficiency of the EHW-driven ORC system were modeled with R245fa, R113 and R123 as the working fluids. The results demonstrate that the EHW and evaporation temperatures have significant effects on the energy and exergy efficiencies of the EHW-driven ORC system. Under given EHW conditions, an optimum evaporation temperature exists corresponding to the highest exergy efficiency. To further use the low-temperature EHW, a configuration retrofitted to the ORC by combining with flash evaporation (FE) was conducted. For an EHW at 120 °C and 0.2 MPa, the maximum exergy efficiency of the FE-ORC system is 45.91% at a flash pressure of 0.088 MPa. The FE-ORC performs better in exergy efficiency than the basic FE and basic EHW-driven ORC.
