Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Swirl Multi-pass Channel with Convergent Jet Slots

This paper presents a comparative experimental and numerical study of the heat transfer and pressure loss in a swirl multi-pass channel with tangential jet slots, and another baseline multi-pass channel with 180-deg U-bends as comparison baseline has also been investigated. Transient liquid crystal thermography is used to obtain the detailed heat transfer distribution on the internal surfaces of the multi-pass serpentine channels. The heat transfer patterns in the swirl multi-pass channel are quite different from that of the baseline multi-pass channel. Compared with the baseline multi-pass channel, the experimental globally averaged Nusselt number ratios of the last two passes in the swirl multi-pass channel can be increased by up to 82.9%, 104.8% and 124.6% for the Reynolds numbers 20,000, 40,000 and 60,000, respectively. The high and circumferentially uniform heat transfer is mainly due to the large-scale swirling flow induced by the tangential slots. More detailly, the large-scale swirling flow impinges onto the surface and further induces high tangential velocity near the wall, which destroys the boundary layer flow and thus improves the heat transfer rates at the wall. However, the notable pressure loss of the swirl multi-pass channel should be further controlled reasonably, which is about 5.4 times that of the baseline multi-pass channel. As supplements to the experiments, three-dimensional numerical computations provide more insights into the turbulent flow structure in the two kinds of multi-pass serpentine channels.

Optimization and Sensitivity Analysis of the Cutting Conditions in Rough, Semi-Finish and Finish Honing

Honing processes are currently employed to obtain a cross-hatched pattern on the internal surfaces of cylinders that favors oil flow in combustion engines or hydraulic cylinders. The main aim of the present paper is to optimize the machining conditions in honing processes with respect to surface roughness, material removal rate and tool wear by means of the desirability function. Five process variables are considered: grain size, density, pressure, linear speed and tangential speed. Later, a sensitivity analysis is performed to determine the effect of the variation of the importance given to each response on the results of the optimization process. In the rough and semi-finish honing steps, variations of less than 5% of the importance value do not cause substantial changes in the optimization process. On the contrary, in the finish honing step, small changes in the importance values lead to modifications in the optimization process, mainly regarding pressure. Thus, the finish honing phase is more sensitive to changes in the optimization process than the rough and the semi-finish honing phases. The present paper will help users of honing machines to select proper values for the process variables.

Analysis of Biodeteriogens on Architectural Heritage. An Approach of Applied Botany on a Gothic Building in Southern Italy

The degradation of stone materials depends on several interlinked factors. The effects caused by biodeteriogens on mineral-based substrates are now increasingly considered in the field of cultural heritage conservation from different experimental approaches. In this study, biodeteriogenic micro- and macroflora within the gothic building of Santa Maria della Pietà, Squillace, Calabria, have been analyzed using multiple approaches, such as optical microscopy and molecular techniques. All 17 plant species detected are usually widespread in Mediterranean regions and some of these, such as Ailanthus altissima and Ficus carica, showed a very high hazard index, which is potentially dangerous for masonry stability. Fungi, cyanobacteria, and green algae were identified within biofilm compositions in a total of 23 different taxa, showing many similarities with microbial associations commonly found in cave and hypogean environments. All of the 11 fungal taxa detected belong to Ascomycota phylum, with Penicillium as the most represented genus. Photoautotrophic organisms are mostly represented by filamentous genera, with widespread presence of Leptolyngbya as the most abundant genus. The results highlighted how the singular environmental conditions of the study site, combined with the architectural features and the building materials, determined all the degradation phenomena affecting the building’s internal surfaces, compromising over time the structural integrity.

Conceptualisation of an Efficient Particle-Based Simulation of a Twin-Screw Granulator

Discrete Element Method (DEM) simulations have the potential to provide particle-scale understanding of twin-screw granulators. This is difficult to obtain experimentally because of the closed, tightly confined geometry. An essential prerequisite for successful DEM modelling of a twin-screw granulator is making the simulations tractable, i.e., reducing the significant computational cost while retaining the key physics. Four methods are evaluated in this paper to achieve this goal: (i) develop reduced-scale periodic simulations to reduce the number of particles; (ii) further reduce this number by scaling particle sizes appropriately; (iii) adopt an adhesive, elasto-plastic contact model to capture the effect of the liquid binder rather than fluid coupling; (iv) identify the subset of model parameters that are influential for calibration. All DEM simulations considered a GEA ConsiGma™ 1 twin-screw granulator with a 60° rearward configuration for kneading elements. Periodic simulations yielded similar results to a full-scale simulation at significantly reduced computational cost. If the level of cohesion in the contact model is calibrated using laboratory testing, valid results can be obtained without fluid coupling. Friction between granules and the internal surfaces of the granulator is a very influential parameter because the response of this system is dominated by interactions with the geometry.

Research Part Surface Position Influence on Metal Removal and Steady-State Roughness During Vibro-Abrasive Processing

The paper is devoted to the study of part surface position and its influence on metal removal and steady-state rougness during vibro-abrasive processing. The article raises the differences between vibro-abrasive processing of external and internal part surfaces. Theoretical dependencies analysis for determination on part material removal and surface steady-state roughness is carried out. It is known that available theoretical dependencies do not take into account part surface position for material removal and the steady-state roughness calculation. Experimental researches to determine internal surface material removal with external surface isolation were carried out. The influence of part surface position on the steady-state roughness is investigated. Based on obtained experimental results, the dependence graphs of material removal and roughness on the processing time are constructed. The comparative analysis of the part surface position influence on material removal and the steady-state roughness during vibro-abrasive processing is carried out. The results showed that material removal volume from the internal surface more than from the external for short part length, however material removal volume from the external surfaces grows significantly in case of part length increasing, while from the internal surfaces is not significant. It is established that the internal surface steady-state roughness is ∼1.55 times higher than external surface steady-state roughness after processing in triangular prism 15×15, grit 16.

Mercury Contamination of Process and Pipeline Infrastructure - A Novel, All- Encompassing Solution for the Evaluation and Decontamination of Mercury from Pipelines and Topside Process Equipment to allow Safe Disposal

Mercury present in produced oil and gas will deposit onto the internal process infrastructure via a number of mechanisms including chemisorption and adsorption with the primary mechanism being through reaction with iron sulphide to form mercury sulphide. Due to the volumes of fluids produced and the length of time facilities are in production, even where the produced fluids have historically contained relatively low concentrations of mercury, pipeline scales containing percentage levels of mercury may be present. Thus, aged facilities and infrastructure that have reached the end of their operational life and are selected for either recycling or abandonment, may pose a serious risk to health and the environment if the decommissioning process is not managed correctly. Smelting, hot cutting or other thermal/abrasive surface preparations for example, can lead to significant release of elemental mercury, a worker exposure hazard. Alternatively, if sub-sea pipelines are abandoned in-situ, all mercury present will ultimately be transferred to the local ecosystems. Consequently, the oil and gas industry have the requirement for a complete mercury decontamination solution from initial evaluation, demonstrable cleaning efficacy through to a guarantee for the treatment and disposal of the mercury waste generated in an environmentally-friendly manner. In order to decide upon the most appropriate decontamination solution, an evaluation of the extent of mercury contamination should be undertaken. A novel approach that has recently been successfully implemented involved analysis of pipe sections by multiple analytical techniques, providing the mercury concentration in the scale/steel. From this, the total mass of mercury across the process or pipeline was approximated. Subsequently, the efficacy of the preferred chemical to remove mercury from the internal surfaces of pipework was evaluated by chemical treatment of the pipe sections under laboratory conditions. In-situ decontamination can be performed by a number of applications, including (i) the use of chemical pig trains in pipelines, (ii) closed loop circulation of chemical around topside process equipment and (iii) high pressure spraying of large surface areas such as storage tanks, FSO / FPSO vessels. The mercury waste generated is treated, on site or off site, to minimise the volume and disposed of in accordance with international regulations. An all-encompassing mercury decontamination solution is described. Trials involving the chemical treatment of steel sections have demonstrated that more than 97% of the mercury deposited can be removed from the internal surfaces of pipelines and safely disposed of, significantly reducing the risk of (i) mercury release to the environment and (ii) worker exposure to mercury during smelting activities.

Adaptive Thermal Comfort of an Office for Energy Consumption-Famagusta Case

The aim of this study was to determine how much thermal comfort can be obtained through heat/energy transfers between the office/external air and the transparent/opaque surfaces of an office by combining different transparent and opaque wall surface ratios with different window opening percentages using dynamic thermal simulations. It found that the optimum window-to-wall ratio (WWR) for energy conservation is 40%, with a 20% window opening ratio. The 80% and 90% thermal comfort ranges of the adaptive thermal comfort methodology are found in May, October, September, and the yearly average, while June and August are only in the range of 80% acceptability. The office constantly loses heat through air flow with any glass size on its external facade and any window opening ratio. Moreover, all sizes of opaque and transparent internal surfaces transferred heat from outside by conduction, while the opaque wall similarly always transferred energy to heat up the office air internally and outside air externally through convection. The external glass also heats the office air by convection, except in the months of January, November, and December.

Acoustic Behavior and Design of Large Urban Spaces – Canyon and Tunnel

Residents of large urban centers are daily exposed to urban noise pollution, especially to noise generated by traffic of vehicles. Environmental noise may harm the environment and the population's quality of life. Therefore, studies that aim to reduce the effects of noise pollution are extremely relevant. In urban divisions, there must be spaces between or in buildings to ensure access for people and vehicles. However, regarding sound transmission, these spaces are considered "weak points" as they ease the passage of urban noise to other spaces that have housing. Thus, this study, carried out in the city of Stuttgart/Germany, evaluates the influence of urban spaces called tunnel and canyon on the transmission of traffic noise to residential facades posterior to these spaces. Two locations were selected: the first with the presence of a tunnel-like space and the second with a canyon-like space. Through measurements and acoustic simulations, the current sound environment of the places was measured. In acoustic simulations, variations of geometric aspects and sound absorption coefficients of the internal surfaces of open spaces were also considered. The results show that the dimensions of open spaces are significant in sound transmission, especially the parameters width and height. The data also show that the installation of coatings with sound absorption on the internal surfaces of spaces is a viable measure from a technical point of view, as it resulted in an attenuation of up to 22 dB(A) on posterior facades.