No abstract

No abstract

No abstract

This study seeks to evaluate thermal comfort in naturally ventilated classrooms to draw sustainable solutions that reduce the dramatic energy consumed in mechanically ventilated spaces. Passive ventilation scenarios are generated using alternations of openings on the windward and leeward sides to evaluate their effects on thermal comfort. Twenty-eight experiments were carried in Bahrain during winter inside an exposed classroom, the experiments were grouped into five scenarios namely: “single-inlet single-outlet” SISO, “single-inlet double-outlet” SIDO, “double-inlet single-outlet” DISO, “double-inlet double-outlet” DIDO and “single-side ventilation” SSV. The findings indicate that single-side ventilation did not offer comfort except at high airspeed, while comfort is attained by using cross-ventilation at ambient temperature between 21.8–26.8 °C. The temperature difference between monitored locations and the inlet is inversely proportional to the number of air changes per hour. The DISO scenario accomplishes the lowest temperature difference. Using cross-ventilation instead of single-side ventilation reduces the temperature differences between 0.5–2.5 °C and increases airspeed up to three folds. According to the measured findings, the DISO cross-ventilation scenario is a valid sustainable solution adaptable to climatic variation locally and beyond with zero-energy consumption and zero emissions.

No abstract

No abstract

Humidification-Dehumidification desalination (HDH) process is an existing, widely-spread and developing technology. This technology has high potential to serve people who suffer lack of water in undeveloped, poor countries as it could be built and operated using locally available natural resources.HDH cycle is considered man-made rain cycle. It utilizes vaporization of water from saline solution into a carrier gas (usually air). Then this saturated air with water vapor passes over a cold surface, leading to condensation process obtaining fresh potable water suitable for human usage.This paper focuses on the heat and mass transfer processes inside each of the humidifier and the dehumidifier sections. In the humidifier section, counter flow between air and water at atmospheric pressure, where direct contact between air and water occurs. In the dehumidifier section, air flows over a coil containing flowing water in opposite direction. Based on mass balance and rate equations, the mathematical modeling equations of both humidifier and dehumidifier sections are established. Output results of simulation process depend on liquid-gas ratio, entering temperature of air in addition to water temperature entering both sections as well as the geometry of both humidifier and dehumidifier.These design parameters can provide great reference significance for the design, optimization and regulation of humidifiers and dehumidifiers sections.

By contrast with conventional heat transfer fluids, the usage of Microencapsulated phase change material (MPCM) suspended in conventional cooling fluids such as water; has shown enhanced heat transfer characteristics. This is due to their higher apparent specific heat values when subjected to heating within their phase change temperature range. The present study investigates numerically the impact of using MPCM slurry on heat transfer coefficient, and pressure drop for laminar thermally developing flow inside rectangular channel subjected to constant heat flux. The MPCM slurry consists of MPCM particles suspended in water as a base coolant. Lagrangian model was used to simulate the transport of MPCM particles through the flow domain by using ANSYS-FLUENT solver. Furthermore, the thermophysical properties of the MPCM particle were defined through the implementation of User-Defined Functions (UDF) available in FLUENT solver. The simulation results were compared to experimental data found in the literature and showed good agreement. The effect of varying MPCM mass concentration inside the slurry was also investigated to record their effect on heat transfer, pressure drop, and channel temperature. It was found that the heat transfer coefficient of MPCM slurry was noticeably increased when compared to the single phase fluid (water), but this comes on the expense of severe increase in the pressure drop. Moreover, a significant drop in the upper channel wall temperature was achieved due to phase change process of the slurry.