Search results

A comprehensive investigation on the outlet air position effects on the thermal comfort and air quality has been achieved. In addition, airflow and temperature distributions in ventilated cavities filled with an air-CO₂ mixture with mixed convection are predicted. The airflow enters from the cavity through an opening in the lower side of the left vertical wall and exits through the opening in one wall of the cavity. This paper aims to investigate the outlet location effect, four different placement configurations of output ports are considered. Three of them are placed on the upper side and the fourth on top of the opposite side of the inlet opening. A uniform heat and CO₂ contaminant source are applied on the left vertical wall, while the remaining walls are impermeable and adiabatic to heat and solute. The cooling efficiency inside the enclosure and the average fluid temperature are computed for different Reynolds and Rayleigh numbers to find the most suitable fluid outlet position that ensures indoor comfortable conditions while effectively removing heat and the contaminant. This is demonstrated by three relevant indices, namely, the effectiveness for heat removal, the contaminant removal and the index of indoor air quality.

The simulations were performed via the finite-volume scSTREAM CFD solver V11. Three different values of CO₂ amount are considered, namely, 10³, 2 × 10³ and 3 × 10³ ppm, the Reynolds number being in the range 100 ≤ Re ≤ 800.

Based on the findings obtained, it is the configuration whose air outlet is placed near the heat source and the contaminant, which provides a better air distribution and a ventilation efficiency compared to the others ventilation strategies.

The studies on heat and mass transfers by natural and forced convection in ventilated cavities remain a fruitful research topic. Thereby, such a study deals with different ventilation strategies through cavities containing an air-CO₂ mixture subjected to a mixed regime. In particular, the air inlet velocity and contaminant sources’ effects on thermal comfort and air quality have been investigated.

Disappearing ink was prepared using different concentrations of thymolphthalein, phenolphthalein and their mixture, applying to different types of handwriting surfaces such as cotton, polyester and polyamide. The effects of thymolphthalein, phenolphthalein and alkali concentrations (i.e. pH) on the fading time were studied. The handwriting stability increased when the concentration of thymolphthalein or phenolphthalein was increased. At a high concentration of alkali with phenolphthalein and its mixture with thymolphthalein, the handwriting stability decreased with polyester or polyamide handwriting surfaces and the stability increased in the case of cotton. When the faded handwriting surfaces were subject to the thermal effect in a thermostatically controlled oven at 100°C for 10 minutes by hanging them with suitable hooks, there was no change in the faded handwriting. When they were at 150°C for 20 minutes, the faded phenolphthalein ink, which contained 0.5ml of 1N NaOH, was visible and shown red on the polyester and polyamide handwriting surfaces, but there was no change on the faded cotton handwriting surface.