• Energy Research

The present study represents a computational analysis of two-dimensional air flow in a new designed configuration of a solar air heater (SAH). The shape of the installed ribs along the absorber pla...

Recently, the cooling process for electronics components has attracted many researchers and several techniques for improving the cooling efficiency and heat transfer rate have been demonstrated. One of the best efficient techniques is the introduction of a synthetic jet and the modification of heating surface. In the present study, the form of heating surface and the signal of the diaphragm has been modified to improve the synthetic jet. These modifications are novel and have been applied for the first time with very good thermal enhancement efficiency for microchannels with synthetic jets applications. This study allowed us to make a quantitative comparison between a basic case with a periodic signal and modified case with bi-periodic signal with two cavities having a slope of 3°, 60 percent obstruction orifices and 10mumof undulation heated wall. The unsteady flow and heat transfer for the two-dimensional synthetic jet are solved using ANSYS fluent code and k-ω (SST) model is selected to account for fluid turbulence. Obtained results showed an increase of Nusselt number by about 51% for the modified case compared with the basic case. Keywords: Heat transfer, Synthetic jet, (SST) K-ω turbulence model, Undulation heated wall, Nusselt number, Periodic signal, Bi-periodic signal

In the present study, numerical investigation of two-dimensional incompressible air flow through a solar air heater (SAH) with a triangular artificial roughness having a curved top corner is performed using ANSYS Fluent 15.0 based finite volume method. The geometrical parameters of the triangular ribs having a curved top corner such as the roughness height ratio (e/D = 0.021, 0.03 and 0.042) and the roughness pitch ratio (p/e =7.14, 10.70, 14.28 and 17.86) have been investigated for a varied Reynolds number between 3800 to 18000. Flow and energy governing equations were solved with the accosiation of two transport equation for the turbulence kinetic energy k and the dissipation rate ɛ. The RNG k-ε turbulent model have been selected to be the more appropriate turbulence model for the present study. Results indicates that the values of Nusselt number and friction factor strongly depend on the roughness relative height e/D, relative pitch p/e and the value of Re number. The best solar air heater performance could be obtained for e/D=0.042 and p/e=7.14.

Every year, flare gas is responsible for more than 350 million tons of CO2 emissions. Aside from thermal and environmental pollution impacts, flare gas contributes to global warming and enormous economic losses. Thus, waste heat recovery due to flaring gas can be explored through Organic Rankine Cycle ORC systems for electricity production. In this context, the assessment of a toluene ORC system is proposed for a potential application in an Algerian petrochemical unit. The study focuses mainly on highlighting the potential and thermodynamic performances of the ORC application to produce electricity and potential cooling thanks to coupling an absorption chiller by recovering heat due to flaring gas. Such a solution can easily be implemented as an energy efficiency key solution. The ORC electrical production can meet the increasing demand of natural gas initially intended to be provided to a gas power plant and assures the major part of the Algerian electrical production.