Despite the studies already developed about Trombe walls, more research work is needed to contribute to the knowledge about their behaviour and optimize it according to the specific characteristics ...of each climatic region. The ventilation openings and the shading device operation decisively influence the temperatures fluctuation along the system and that impact should be discussed.
In this context, a test cell with a classical Trombe wall was submitted to real climatic conditions in a Portuguese city. The effect of ventilation openings and shading devices in the temperatures fluctuation was analysed.
The temperatures in the air layer and along the massive wall presented a similar oscillation pattern and exceeded 60°C without ventilation and shading devices. For this configuration, temperature values at the top of the air layer were always higher than those obtained at the base and a differential of 19°C was achieved.
The temperature fluctuation across the massive wall was not proportional to its thickness due to its heat storage capacity.
When the ventilation system was closed and the shading device was not activated, the temperature inside the test cell exceeded the outside temperature value in 9°C, showing the system ability to store and release heat.
The photothermal conversion performance (PCP) of a nanofluid-based solar energy system is investigated numerically and experimentally. The impacts of particle size, volume concentration, nanoparticle ...type, base fluid type and collector inclination angle on the PCP are investigated. It is observed that using nanoparticles improves the ability to absorb solar energy. Temperature gain is 2.2, 3.2, 3.8, 4.2, and 9 times better than pure water for water-based Al, Al2O3, Au, Cu, and Graphite mono nanofluids, respectively. Interestingly, blended nanofluids containing the same nanoparticles significantly argument the optical properties, with useful heat enhancement ranging from 62.8 (mono) to 194 kJ/kg (hybrid). However, the collector's inclination angle, which ranges from 0 to 60°, has a negative impact on the PCP by reducing the solar radiation absorption of the nanofluids due to a decrease in the radiation penetrating the collector. Furthermore, as nanoparticle size increases, so does the thermal performance of the nanofluid. An experimental investigation is carried out for pure water and nanofluid at various wind speeds and solar irradiation levels ranging from 1 to 4 m/s and 200–1000 W/m2, respectively, to validate the numerical results.
•Photothermal performance of a nanoparticle based solar collector is experimentally and numerically investigated.•Attenuation of pure working fluid is augmented by nanoparticles.•Improving nanoparticle diameter enhances temperature gain.•Blended nanoparticles further enhance useful heat capacity.•Tilt angle diminishes thermal capacity of the collector.
•Tests were conducted on hybrid tubular K-joints with circular braces and square chord in stainless steel.•Load-carrying capacities of overlapped hybrid tubular K-joints are much larger than those of ...gapped hybrid tubular K-joints.•Load-carrying capacities increased with the increase of the β, but increased with the decrease of the e.•CIDECT is unconservative, while EC3, AS/NZS and Chinese Code are very conservative for overlapped hybrid K-joints.•CIDECT and EC3 are conservative, Chinese Code is unconservative, and AS/NZS is appropriate for gapped hybrid K-joints.
An experimental investigation was conducted in this study on hybrid tubular K-joints with circular braces and square chord in stainless steel. A total of 14 hybrid tubular K-joints including 7 overlapped and 7 gapped K-joints were tested. All specimens were made of AISI 304 austeniticstainlesssteel. The failure modes, load-carrying capacities, and testing curves of axial load versus vertical displacement/chord deformation of all specimens were obtained. The influences of important geometric variations including brace diameter/chord width ratio (β), eccentricity (e), overlap ratio (Ov) of overlapped tubular K-joints and gap distance (g) of gapped tubular K-joints were analyzed. It is shown that the load-carrying capacities of overlapped hybrid tubular K-joints are much greater than those of gapped hybrid tubular K-joints. It is also discovered that the load-carrying capacities increased with the increment of the β value, and increased with the decrement of the e value. Furthermore, the load-carrying capacities of overlapped hybrid tubular K-joints increased with the increment of the Ov value; however, the influence of the g value on the load-carrying capacities of gapped hybrid tubular K-joints is insignificant. It is demonstrated that the design formulae provided by CIDECT are generally unconservative; whereas the design formulae provided by EC3, AS/NZS and Chinese Code are all quite conservative for overlapped hybrid tubular K-joints. In addition, the design formulae provided by CIDECT and EC3 are generally conservative; however, the design formulae provided by Chinese Code are generally unconservative; and the design formulae provided by AS/NZS are generally appropriate for gapped hybrid tubular K-joints.
•High-pressure VLE data concerning CO + N2 binary system has been measured using static analytic method.•Cubic equation of state has been considered to predict the phase diagram.•Van Ness consistency ...test method has been applied.•Comparison with literature data and GERG model predictions have been realized.
Isothermal vapor-liquid equilibrium (VLE) data have been measured for the nitrogen + carbon monoxide binary system at 5 temperatures from 100.01 to 130.07 K, and at pressures from 0.37 to 3.35 MPa. This system had already been studied by different authors. Nevertheless, the existing literature data generally indicate high vapor pressure for pure CO and for the highest CO composition in the N2-CO binary VLE measurements. Our new VLE data have been measured using the “static-analytic” method, taking advantage of two pneumatic capillary samplers (Rolsi®, Armines' patent) coupled to an adapted apparatus able to work at cryogenic temperatures. The new data were compared with the predictions of the GERG equation of state and their consistency was checked by a Van Ness type test. We have observed that the isothermal P, x, y data were well represented with the Peng-Robinson equation of state, especially in the CO rich region.
Ethnoarchaeological research, which gained great popularity in the second half of the 20th century, has become a new full-fledged source for a variety of socio-economic reconstructions in ...archaeology, including when characterizing the features of industrial complexes. Developments that combine experimental traceological analysis of tools and ethnographic data play an important role in modeling ancient technologies, especially when ethnographic artifacts are a direct continuation of archaeological traditions, both in terms of their manufacturing method and specific purpose. In this regard, the study of stone knives from the Ekven burial ground of the 1st millennium AD is of great interest, discovered in Chukotka. These products have retained their specific form from antiquity to the present day. The presence in the archaeological and ethnographic collections of these items in varying degrees of processing and use (from blanks to tools with a completely recycled or redesigned working blade) made it possible not only to describe the chain of basic technological operations of their manufacture from the primary processing of raw materials, shaping, processing of the working and edge parts, mounts in the handle, but also to install the tools involved in this production process. The data obtained were verified using experimental work, which confirmed the invariability of the technology for processing slate raw materials and manufacturing archaeological and ethnographic man’s knives from it.
•Assembly of a mathematical and simulation model for the solar chimney.•Construction of a modified experimental rig together with a solar imaging reflector.•Detailing the solar concentration effect ...at the base of the chimney.•Validating the results by comparing experimental and simulation results.•Drawing conclusions with respect to temperature and air flow velocity.
In solar chimney the flow of air in the system plays a dominant role. Solar chimney systems are usually large and have a low efficiency. In this research a redesigned experimental solar chimney power plant with a modified collector layout was evaluated. A tracking mirror reflector was used to enhance the thermal concentration effect underneath the chimney. The emphasis was on increasing the temperature at the transition zone between the collector and the chimney base and creating an improved overall temperature difference. Mathematical analysis of the thermal and flow behavior of the currents, under the influence of the concentration effect from the reflector, led to the development of a simulation algorithm to assist in the evaluation process. A comparative analysis was applied to investigate the effect of thermal concentration on the air flow velocity under the chimney. The indicators were the variation of the overall thermal radiation in the transition zone and the instigated temperature rise with hourly ambient temperature change. The obtained results suggested up to 10.25% increase in the maximum temperature obtained at the chimney base. This induced a maximum air flow velocity improvement of 22.22%. The impeding effect of density reduction at the considered temperature range was checked against the total theoretical output power. At peak output when the power scored 56.867% rise from the average for the day, air flow velocity showed 25.316% increase while the air density was reduced by only 2.069% from the mean values for the day.
•The performances of a novel integrated of indirect evaporative cooler and evaporative condenser are experimentally studied.•The effects of pre-cooling unit (indirect evaporative cooler) on the ...performance of evaporative condenser are investigated.•The effect of external film cotton layer on performance of evaporative condenser is investigated.•The percentage increases in cooling load change between 35.4 and 54.2% for using the pre-cooling unit and cotton layer.
In this study, the performance of a novel integrated system of indirect evaporative cooler with internal baffles as air pre-cooling unit and evaporative condenser has been experimentally investigated. For this purpose, the experimental setup consisting of an indirect evaporative cooler with internal baffles followed by an evaporative condenser contains the hot water serpentine tubes with external thin film cotton layer was designed, constructed and tested. The influences of pre-cooling unit and the external thin film cotton layer on the performance of the evaporative condenser are investigated. The experimental results show that, for increasing the air flow rate from 250 to 1450 m3/h, the temperature difference of hot water through the evaporative condenser change in the ranges between 13 and 24.9°C for the case without pre-cooling unit, 17.6–38.4°C for using the pre-cooling unit with internal baffles and with use the thin film cotton layer. Also, the rate of change of the cooling load is in the ranges between 166 and 318kW for case without pre-cooling unit, but for using the pre-cooling unit with internal baffles and with use the thin film cotton layer the cooling load change between 224.7 and 490.3kW. For using the external thin film cotton layer on the tubes of cross flow heat exchanger and with use the pre-cooling unit with internal baffles before the evaporative condenser the percentage increases in the cooling load change between 35.4 and 54.2% compared to the evaporative condenser without pre-cooling unit.
PDF
