Abstract Recent developments in micro‐energy and micro‐chemical systems have produced a need for greater understanding of flow small channels. Several recent studies friction factors transition Reynolds numbers rectangular microchannels results that differ from classical theory. In this work, laminar constants were determined water flowing high aspect ratio channels with depths ranging 128 to 521 μm. between 60 3,450. Pressure drops measured within the channel itself exclude entrance exit...

The evolution of energy sector worldwide triggered intense preoccupation on both finding alternative renewable sources and environmental issues. Romania is considered to have technological potential geographical location suitable usage for electricity generation. But this high not fully exploited in the context policies regulations adopted globally, more specific, European Union (EU) strategies legislation related sources. This SWOT analysis solar source presents state art, future prospects...

This paper focuses on the finite physical dimensions thermodynamics (FPDT)-based design of combined endoreversible power and refrigeration cycles (CCHP). Four operating schemes were analyzed, one for summer season three winter season. These basic CCHP should define reference ones, having maximum possible energy exergy efficiencies considering real restrictive conditions. The FPDT is an entropic approach because it defines uses dependences between entropy control operational parameters...

This paper reports on an experimental study of heat transfer in high aspect ratio (width/depth), rectangular micro-channels. A single channel with width 10 μm was cut into polycarbonate spacers various thicknesses, resulting depths 128 μm, 263 and 521 μm. Heat experiments were performed a constant flux boundary condition applied at the surface channel. Experiments conducted for refrigerant R-124 working fluid range Re = 300 − 900 Pr 3.6 3.8 showed small or no departure from macro-scale...

Abstract This paper presents the results of experiments performed on single-phase flow in microchannels. Channel depths ranged between 100 and 500 microns, with a W:H ratio greater than 20:1. Water was primary working fluid these studies, Reynolds numbers (based hydraulic diameter channel) ranging 40 4000. The experimental setup used allowed measurements local pressure drop as well visualization patterns within channel using microscopy. Data presented include friction factors for various...

This article describes several numerical simulations on aerodynamic characteristics of an oval shaped hovercraft. The 3D model was created in CATIA V5 and analysis performed ANSYS Fluent. For simulation, the velocity at inlet section air-clearance height were specified as input parameters, with stationary hovercraft, flat ground surface flexible skirt that does not deform under influence pressure imposed conditions. Three different heights velocities are analysed. output results mass flow...

Abstract People spend nearly one-third of their life on sleeping. Several factors can affect bedroom air quality and comfort sleep, such as temperature, relative humidity quality. The most common indicator indoor is the concentration carbon dioxide, its presence in environment being strictly related to respiration human metabolism. Since 2002, when European Parliament Council approved directive energy performance buildings, EU member countries launched various programs for refurbishment...

Abstract At present time, the most used flexible skirt in construction of air cushion vehicles is segmented one. Therefore, this study focuses on performing CFD analysis specific to area segments such a skirt. The proposed model has outer diameter 1 meter, segment thickness 2 mm and feed hole 50 mm. A particular feature circular ring shape hole. Considering that height clearance directly influence performance cushion, these two parameters were varied. Values ranged between 200 for from 10...

Abstract In 2020, the world population was surprised by spread and aggressiveness of a pandemic outbreak SARS-CoV-2 disease (caused COVID-19 coronavirus). world-spread effort to diminish medical effects, measures employed large majority countries severely influenced all economic sectors, including energy one. This paper reports on status sources usage Romanian market within worldwide context current effects national contingency plan market, especially solar photovoltaic area. The conclusions...

This paper proposes two configurations for a hybrid solar energy conversion device that can be used as self-sustained, independent power generation system in isolated locations hot climate areas. Given the strong dependence of photovoltaic cell efficiency on operation temperature, cooling backside becomes imperative, increasing not only electrical, but also overall efficiency. The provides now electricity and hater domestic applications. To further improve electrical efficiency,...

Hybrid electric vehicles (HEV) are currently considered a viable solution for fossil fuel saving and pollutant emissions reduction in transportation sector. The typical HEV configuration contains reciprocating internal combustion engine – gasoline or diesel. Aiming to increase performance reduce pollution, study on performance, size mass of with micro gas steam turbine was developed. proposed system generates 100 kW output power operates compressed natural (CNG hybrid technology), which is...

Friction torque in an angular contact ball bearing is dependent on the motion of balls, lubricant viscosity and quantity, rotational speed applied loads. To evaluate friction a bearing, SKF methodology includes geometrical parameters, type lubrication, operation speeds loads (radial axial). As indicated catalogue, above-mentioned can be used for equal to or larger than recommended minimum load indicated. For very low dry limit conditions, catalogue doesn't indicate adequate models estimate...

Abstract The presence of the lubricant in a ball-race contact has two principal effects on friction: reduces sliding friction, as result developing film thickness between surfaces and increases rolling hydrodynamic friction. influence friction torque modified 7205B angular ball bearing been theoretically experimentally studied. experiments demonstrated that, for very low loads balls races, effect force is dominant total torque. have validated by using Biboulet’s transition model forces...

Abstract World population growth along with requirements for more energy forced scientists into research cleaner and sustainable sources. The largest available source, solar requires improved technologies processes conversion electrical thermal energy. This paper continues a series of analyses proposed hybrid module, which combines direct photovoltaic (PV) to electricity (T) waste heat recovery (using thermoelectric devices, TE). An extended life cycle analysis (LCA) is performed on each the...

A procedure has been developed to determine both the value of ball's angular velocity and position this velocity, according normal loads in a linear system with four contact points. The program is based on variational analysis power losses ball-races contacts. Based two kinematics parameters ball (angular position) were determined, type KUE 35 as function C/P ratio.

Abstract Ever since 1716, when the first concept of building a vehicle to operate with an air cushion was presented, world remained fascinated by this concept. This article presents study on important parameters flow into inner cavity simple plenum hull, configuration vehicle. In order achieve this, six constructive models were chosen, only major difference being angle inclination at bottom hull. The paper specific mathematical model adapted for type configuration, imposed dimensions, steps...

The functioning of a Vuilleumier heat pump with four variable-volume chambers and six exchangers was numerically simulated using theoretical adiabatic physico-mathematical model. All were assumed as the considered isothermal. model uses piston movement laws given by mechanism not simplified sinusoidal ones. described through thermodynamic diagrams showing pressure temperatures cyclical variations inside machine each chamber. allows to estimate performances, highlighting energy exchanged...

Abstract The anticipated depletion of conventional fuels (crude oil, coal) reserves as energy sources triggered extended researches for renewable sources. In the last few decades, technologies conversion from solar to electric and thermal evolved rapidly. Some recent photovoltaic (PV) panel cooling methods involve thermoelectric (TE) elements. authors proposed a trifold that employs both (T) TE lower temperature PV operation extract waste heat. Recently, an important number publications...

Abstract Polylactic acid (PLA) is a plastic material used occasionally for thermal insulation. Thus, information required with respect to the insulation property specific various types of PLA. On other hand, development 3D printing processes has led ensuring conditions manufacturing PLA parts, properties that can be modified by varying input factors process. The proposed experimental research method uses measurement temperature variation on one surface panel, while applying cooling process...