Search results1 – 2 of 2
The purpose of this paper is to model the convective flows in a room equipped by a glass door and a heated floor of length l = 0.8 × H and submitted to a sinusoidal…
The purpose of this paper is to model the convective flows in a room equipped by a glass door and a heated floor of length l = 0.8 × H and submitted to a sinusoidal temperature profile and mono alternative temperature profile.
The paper opts for a numerical study of convective flows in a large scale cavity using the Lattice Boltzmann Method (LBM) by considering a two dimensions (2D) square cavity of side H and filled by air (Pr = 0.71). All the vertical walls, the ceiling and the rest of the floor are thermally insulated, the hot portion of length l = 0.8×H is heated with two imposed temperature profiles of amplitude values 0.2 ≤ a ≤ 0.6 and for two different periods ζ = ζ0 and ζ = 0.4×ζ0. One of the vertical walls has a cold portion θc = 0 that represents the glass door.
A systematic study of the flow structure and heat transfer is carried out considering principal control parameters: amplitude “a” and period ζ for Rayleigh number Ra = 108. Effects of these parameters on results are presented in terms of isotherms, streamlines, profiles of velocities, temperature in the cavity, global and local Nusselt number. It has been found that an increase in amplitude or period increases the amplitude of the temperature in the core of cavity. The Nusselt number increases when the amplitude “a” of the imposed temperature increases, but this later is not affected by variation of the period.
The authors used LBM to simulate the convective flows in a cavity at high Ra, heated from below by tow imposed temperature profiles. Indeed, they simulate a local equipped by a solar water heater (SWH). The floor is subjected to a periodic heating: Sinusoidal heating (Case 1) for which the temperature varies sinusoidally (SWH without a supplement), and mono alternation heating (Case 2), the temperature evolves like a redressed signal (SWH with a supplement). The considered method has been successfully validated and compared with the previous work. The study has been conducted using several control parameters such as the signal amplitude and period in the case of turbulent convection. This allowed us to obtain a considerable set of results that can be used for engineering.
The aim of this study was to measure the apparent viscosity, flow behavior and density of melon juice as a function of temperature and juice concentration and to obtain…
The aim of this study was to measure the apparent viscosity, flow behavior and density of melon juice as a function of temperature and juice concentration and to obtain simple equations to correlate experimental data.
Melon juice was concentrated in a rotary evaporator to 40±1, 52.5±1 and 65±1°Brix at 50°C, 80 rpm and stored at 4°C until analysis. Density of melon juice was determined with 25 ml pycnometer at 15, 25 and 35°C and was expressed as kg/m3. All experiments were conducted in triplicate. Experimental data were fitted to different models (linear, quadratic, exponential, quadratic exponential and polynomial) using Minitab 16. Significant differences in the mean values were reported at p<0.05. The flow behavior of melon juice was determined using a concentric cylinder rotational viscometer at shear rate range of 13.2-330 s−1 and temperatures of 15, 25 and 35°C. The experimental data were analyzed Slide Write V7.01 Trial Size (p<0.05) and the rheograms was plotted by Microsoft Excel 2007.
Results showed that the four-term polynomial model is the best model for computing density values from temperature and concentration (R2=0.999). The measured shear stress was within 1.69-780 Pa, corresponding to viscosity range of 0.016-0.237 Pa · s. Within the tested conditions, the concentrate exhibited a pseudo plastic behavior. Temperature had an inverse effect on shear stress and apparent viscosity.
No research had been done on production of melon juice concentrate.