2 results listed
Hydrogen can be produced by many processes, by a
series of chemical reactions, many of which have been known for
centuries. However, most of these reactions raise severe
environmental and safety problems. The analysis of Hydrogen
production without CO2 emissions is one of the most challenging
activities that have been initiated for a sustainable energy supply.
As one of the tracks to fulfil such objective, direct methane
cracking has been proposed.
In this context comes this numerical simulation of the methane
cracking phenomenon. The cracking phenomena of the methane
into hydrogen and carbon black takes place in a cylindrical
cavity of 16 cm in diameter and 40 cm in length under the heat of
concentrated solar radiation without any catalyst. The low
Reynolds K - ε turbulence model was applied. A time step of
0.04s has been used. A commercial calculation code "ANSYS
FLUENT" is used to simulate the cracking phenomena. The
effect of temperature, methane flow rate and residence time has
been analysed. From the view point of solar energy two cases
were studied: the first one applying a maximum solar radiation
of 16MW/m2 on the side wall of the reactor and the second one
applying a maximum solar radiation of 5 MW/m2. The CH4 flow
rates used at the inlet of the reactor are 0.10, 0.30, 0.58, 0.60, 0.62,
0.76, 0.94 and 1.25L/min. From the view point of phase numbers
three cases with were considered: first, the mixture is considered
to be biphasic formed by a gaseous phase with methane,
hydrogen gases and carbon black powder solid phase, this
powder is formed by solid particles with same diameter
(d=50nm); the second case is a mixture of 3 phases, i.e. a carbon
powder of 2 different diameters plus a gas phase; the third case
is a mixture of 5 phases, i.e. a carbon powder of 4 different
diameters plus a gas phase.
1.st International Conference Energy Systems Engineering
ıcese'17
Rabah Gomri
Belkacem Nezzari
Absorption cooling systems are more environment
friendly, capable of utilizing low grade heat. By consuming very
small electric power, the half-effect absorption chillers can be
driven by low temperature solar energy.
The half-effect absorption cooling system contains five
temperature levels and three pressure levels. For a given set of
generators, evaporator, condenser and absorbers temperatures,
the intermediate pressure (Pi) must be optimized to get a
maximum coefficient of performance ‘COP’ and exergy
efficiency of the system. The energy and exergy analysis is
carried out for each component of the half-effect absorption
cooling system. All exergy flows within the system are calculated.
The flow rate ratio, the coefficient of performance and the exergy
efficiency of the system are estimated. The effect of generator
temperature, absorber temperature and condenser temperature
are analyzed for a commonly used chilled water temperature
(12°C/7°C).
New analytical expression of the intermediate pressure is
developed. The derived correlation can help the researchers to
predict the values of the intermediate pressure of the half-effect
absorption cooling system before carrying out their experiments
1.st International Conference Energy Systems Engineering
ıcese'17
Rabah Gomri
Khellaf Nabil