Various studies to improve the thermal performance of flat plate solar collector (FPSC) solar water heater have been conducted, and more are currently in progress. This study aims to review existing methods on thermal performance enhancement for FPSC and discuss on heat-transfer enhancement using vibration and its potential application for FPSC. Ten methods for improving thermal performance are identified, which include applications of nanofluids, absorber coatings, phase change materials (PCM), thermal performance enhancers, FPSC design modifications, polymer materials, heat loss reduction, mini and micro channel and heat-transfer enhancement using vibration. An examination of heat-transfer enhancement using vibration in low frequency ranges for an evacuated-tube solar collector (ETSC) solar water heater system showed that it can potentially achieve heat-transfer enhancement of up to 78%. Nevertheless, there is still a lack of research on the applications of heat-transfer enhancement using vibration on FPSC to date.

Numerical fluid–structure interaction (FSI) methods have been widely used to predict the cardiac mechanics and associated hemodynamics of native and artificial heart valves (AHVs). Offering a high degree of spatial and temporal resolution, these methods circumvent the need for cardiac surgery to assess the performance of heart valves. Assessment of these FSI methods in terms of accuracy, realistic modeling, and numerical stability is required, which is the objective of this paper. FSI methods could be classified based on how the computational domain is discretized, and on the coupling techniques employed between fluid and structure domains. The grid-based FSI methods could be further classified based on the kinematical description of the computational fluid (blood) grid, being either fixed grid, moving grid, or combined fixed–moving grid methods. The review reveals that fixed grid methods mostly cause imprecise calculations of flow parameters near the blood–leaflet interface. Moving grid methods are more accurate, however they require cumbersome remeshing and smoothing. The combined fixed–moving grid methods overcome the shortcomings of fixed and moving grid methods, but they are computationally expensive. The mesh-free methods have been able to encounter the problems faced by grid-based methods; however, they have been only limitedly applied to heart valve simulations. Among the coupling techniques, explicit partitioned coupling is mostly unstable, however the implicit partitioned coupling not only has the potential to be stable but is also comparatively cheaper. This in-depth review is expected to be helpful for the readers to evaluate the pros and cons of FSI methods for heart valve simulations.

Purpose: The purpose of this paper is to investigate oil-gas slug formation in horizontal straight pipe and its associated pressure gradient, slug liquid holdup and slug frequency. Design/methodology/approach: The abrupt change in gas/liquid velocities, which causes transition of flow patterns, was analyzed using incompressible volume of fluid method to capture the dynamic gas-liquid interface. The validity of present model and its methodology was validated using Baker’s flow regime chart for 3.15 inches diameter horizontal pipe and with existing experimental data to ensure its correctness. Findings: The present paper proposes simplified correlations for liquid holdup and slug frequency by comparison with numerous existing models. The paper also identified correlations that can be used in operational oil and gas industry and several outlier models that may not be applicable. Research limitations/implications: The correlation may be limited to the range of material properties used in this paper. Practical implications: Numerically derived liquid holdup and holdup frequency agreed reasonably with the experimentally derived correlations. Social implications: The models could be used to design pipeline and piping systems for oil and gas production. Originality/value: The paper simulated all the seven flow regimes with superior results compared to existing methodology. New correlations derived numerically are compared to published experimental correlations to understand the difference between models.

Energy performance of buildings has attracted much attention among building physicists and engineers worldwide. The effects of building heating; ventilation; and air conditioning (HVAC) systems’ design upgrade on the building energy performance are the focus of the current study. The adopted HVAC system consisted of chilled ceiling and chilled beam systems served by a centrifugal water chiller. An energy simulation study was undertaken in accordance with the national Australian built environment rating system-rules for collecting and using data. A three-dimensional simulation study was carried out utilizing the virtual environment-integrated environmental solutions software. Results from the current study have shown the importance of utilizing energy-efficient HVAC systems and HVAC strategies for achieving a high building energy star rating. Recommended strategies in order to achieve the nominated star rating; as predicted by the simulation analysis; were presented. Moreover; the effects of solar radiation inside the building atrium were significant; which cannot be overcome by simply installing a low shading coefficient glazing type at the atrium skylight. In addition to providing chilled ceiling technology; a high efficiency chiller and low energy lighting; it is recommended that the building be well tuned during the commissioning period. The current approach could be extended to accommodate higher energy ratings of commercial buildings at different locations worldwide.

Bileaflet mechanical heart valves (BMHVs) are widely used to replace diseased heart valves. However, patients may suffer from implant complications, such as platelet aggregation and damage to blood cells, which could lead to BMHV failure. These complications are related to the blood flow patterns in the BMHV. A three-dimensional computational fluid dynamic (CFD) model was developed to investigate blood hydrodynamics and shear stresses at different cardiac cycles. A user-defined function (UDF) code was developed to model the valve leaflet motion. This UDF updates the tetrahedral mesh according to the location of the valve leaflet, which enables modeling of complicated moving geometries and achieves solution convergence with ease without the need to adjust the relaxation factor values. The agreement between the experimental and numerical results indicates that the developed model could be used with confidence to simulate BMHV motion and blood flow. Furthermore, valve leaflet and valve pivot were found to be continuously exposed to shear stresses higher than 52.3 Pa which according to previous research findings may cause damage to blood platelets.

Among numerous electronic cooling methods, a vibrating heat sink using sinusoidal wave vibration effectively enhances the heat transfer by disturbing the thermal boundary layer. However, sinusoidal wave vibration has reached its limits in enhancing heat transfer. The present study utilizes a new square wave-shaped vibration and numerically investigates the thermal performance of a heat sink subjected to sinusoidal and square waves vibration. It is found that using the square wave vibration is more beneficial to the thermal performance of the heat sink than the sinusoidal wave. The sudden impulsive motion of square wave vibration induces a higher randomness of the airflow profile and recirculation zones than the sinusoidal wave, causing the air flow to impinge directly into the fin surfaces, and further enhances the heat transfer. Furthermore, increasing the frequency and amplitude leads to a higher heat transfer enhancement. Moreover, square wave vibration achieves a 25% increase in Nusselt values compared to the nonvibrating fins and it is 11% higher than the Nusselt number recorded by the sinusoidal vibration. Consequently, Reynolds number values can be reduced by 42.2% to achieve the Nusselt number values of nonvibrating fins, potentially reducing the cooling system or fin size. This reduction may contribute to solving the challenges of electronic systems compactness.