In order to recover the low grade waste heat and increase system fuel economy for main engine 10S90ME-C9.2-TII(part load, exhaust gas bypass) installed on a 10000 TEU container ship, a non-cogeneration and single-pressure type of waste heat recovery system based on organic Rankine cycle is proposed. Organic compound candidates appropriate to the system are analyzed and selected. Thermodynamic model of the whole system and thermoeconomic optimization are performed. The saturated organic compound vapor mass flow rate, net electric power output, pinch point, thermal efficiency and exergy efficiency varied with different evaporating temperature are thermodynamically analyzed. The results of thermodynamic and thermoeconomic optimization indicate that the most appropriate organic compound candidate is R141b due to its highest exergy efficiency, biggest unit cost benefit and shortest payback time.
The paper presents investigations related to solving of a direct and inverse problem of a non-stationary heat conduction equation for a cylinder. The solution of the inverse problem in the form of temperature distributions has been obtained through minimization of a functional being the measure of the difference between the values of measured and calculated temperatures in M points of the heated cylinder. The solution of the conduction equation was presented in the convolutional form and then numerically integrated approximating one of the integrand with a step function described with parameter Θ ∈ (0, 1]. The influence of the integration parameter Θ on the obtained solution of the inverse problem (including a number of temperature measurement points inside the heated body) has been analyzed. The influence of the parameter Θ on the sensitivity of the obtained temperature distributions has been investigated.
Results of experimental and numerical investigations of wood chips drying are described in the paper. Experiments are carried out on two test facilities: a small laboratory rig and a larger pre-prototype dryer. Both facilities are thorough-circulation convective air dryers. The first one is a batch dryer, whereas the second one is a continuous dryer with wood chips flowing down by gravity from a charging hopper to a gutter with the aid of screw-conveyor. The latter is considered a half scale model (preprototype) for professional drying installations. A low feeding rate of wood chips into the pre-prototype dryer makes the process quasi-stationary and the difference between it and a batch drying is negligible. So, most experiments at this facility were carried out as batch dryers with non-agitated packed beds. The investigations exhibit the same linear correlation between the mass of evaporated water from the packed bed and the drying air velocity for both facilities. Numerical analysis of the drying process is conducted using the Ansys Fluent software enriched in drying capabilities by means of self-written procedures – user defined functions. Simulations confirmed a phenomenon of a drying front observed in the small laboratory rig. A thin layer of wood chips comprises the whole heat exchange and moisture evaporation phenomenon. The drying front travels downstream in the course of the process separating the already dried layer and still wet layer.
The flat horizontal polymer loop thermosyphon with flexible transport lines is suggested and tested. The thermosyphon envelope consists of a polyamide composite with carbon based high thermal conductive micro-, nanofilaments and nanoparticles to increase its effective thermal conductivity up to 11 W/(m°C). Rectangular capillary mini grooves inside the evaporator and condenser of thermosyphon are used as a mean of heat transfer enhancement. The tested working fluid is R600. Thermosyphon evaporator and condenser are similar in design, have a long service life. In this paper three different methods (transient, quasi-stationary, and stationary) have been used to determine the thermophysical properties of polymer composites used as an envelope of thermosyphon, which make it possible to design a wide range of new heat transfer equipment. The results obtained contribute to establish the viability of using polymer thermosyphons for ground heat sinks (solar energy storage), gas-liquid heat exchanger applications involving seawater and other corrosive fluids, efficient cooling of superconductive magnets impregnated with epoxy/carbon composites to prevent wire movement, enhance stability, and diminish heat generation.
An evaluation method is developed for temperature oscillation experiments in heat exchangers. The unity Mach number dispersion model is applied. For the consideration of lateral wall heat conduction an effective wall thickness is introduced together with a wall heat transfer coefficient. The evaluation method may also be applied to single blow experiments with pulse signals. A sensitivity analysis describes and discusses the accuracy of different evaluation procedures.
Present paper is a continuation of works on evaluation of red, green, blue (RGB) to hue, saturation, intensity (HSI) colour space transformation in regard to digital image processing application in optical measurements methods. HSI colour space seems to be the most suitable domain for engineering applications due to its immunity to non-uniform lightning. Previous stages referred to the analysis of various RGB to HSI colour space transformations equivalence and programming platform configuration influence on the algorithms execution. The main purpose of this step is to understand the influence of computer processor architecture on the computing time, since analysis of images requires considerable computer resources. The technical development of computer components is very fast and selection of particular processor architecture can be an advantage for fastening the image analysis and then the measurements results. In this paper the colour space transformation algorithms, their complexity and execution time are discussed. The most common algorithms were compared with the authors own one. Computing time was considered as the main criterion taking into account a technical advancement of two computer processor architectures. It was shown that proposed algorithm was characterized by shorter execution time than in reported previously results.
The paper presents results of experimental investigation of microchannel boiling flow which was controlled by dielectrophoretic (DEP) restrictor. The DEP restrictor was connected to the microchannel liquid supply tube. Operation of DEP restrictor influenced the flow rate at the microchannel inlet. Resulting changes in flow structures and vapour content along the microchannel were observed and analysed with a high-speed video camera. Video recordings were synchronised with measurements of differential pressure between the channel inlet and outlet. It was found that it is possible to change average void fraction in the microchannel by switching on and off the voltage applied to the restrictor electrodes. However, to achieve significant variation of the void fraction, applied voltage should be of the order of 2000 Vpp. The voltage switching also generates oscillations of the differential pressure. The amplitude of these oscillations is proportional to the voltage magnitude, reaching 35 Pa for 2400 Vpp.
Presented work considers flow and thermal phenomena occurring during the single minijet impingement on curved surfaces, heated with a constant heat flux, as well as the array of minijets. Numerical analyses, based on the mass, momentum and energy conservation laws, were conducted, regarding single phase and two-phase simulations. Focus was placed on the proper model construction, in which turbulence and boundary layer modeling was crucial. Calculations were done for various inlet parameters. Initial single minijet results served as the basis for the main calculations, which were conducted for two jet arrays, with flat and curved heated surfaces. Such complex geometries came from the cooling systems of electrical devices, and the geometry of cylindrical heat exchanger. The results, regarding Nusselt number, heated surface temperature, turbulence kinetic energy, production of entropy and vorticity, were presented and discussed. For assumed geometrical parameters similar results were obtained.
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