Search Results
Abstract
The rate of thermal exchange reactions between carboxyl groups and14CO2 increases in the presence of catalytic amounts of alkali malonates. This catalytic effect can be utilized for preparative purposes also in the synthesis of11C-labelled aliphatic carboxylic acids from11CO2.
Abstract
The spiral plate heat exchanger (SHE) is widely used in plenty of industrial services in full counter current flow liquid-liquid heat exchange. We have produced a thermal modelling of the heat exchanges in both steady-state and time dependent cases with 2D spiral geometry, allowing computation with different materials, forced convective heat transfer models in turbulent flow and geometrical parameters options. We will display here some results in steady-state conditions in order to improve the exchanger performances.
Abstract
A kinetic study of thermal and photoaccelerated U(IV)-U(VI) isotope exchange has been carried out in oxalate solutions at 11–40°C. The rate and quantum yield were determined as a function of U(IV), U(VI) and oxalate concentration, wavelength of incident light, temperature and absorbed dose of 
-radiation. The kinetic equations for thermal and photoaccelerated exchange have been obtained. It was assumed that the mechanism of exchange involves formation of U(V) as an intermediate, followed by slow exchange between U(V) and U(IV). The isokinetic dependence confirms the identity of limiting stages for thermal and photostimulated exchange. The upper component of photoexcited T1 level of uranyl is supposed to be the most reactive in the process of U(V) generation. It was observed that the small doses of -radiation evoke the acceleration of isotope exchange, however, at D>100 krad the rate of exchange is reduced to the level of thermal exchange.
Abstract
We show here an adaptation of the classical Flash Method permitting the measure of the thermal conductivity of semi-transparent porous materials. A flash lamp send a heat pulse on the upper face of a cylindrical sample and lower face temperature is analysed. The semi-transparent material is sandwiched between two copper slices. The sample used scatters thermal radiation, and absorbs it very little. It is therefore possible to account for two parts of heat transfer through the material: a pure conductive phenomenon and a radiative one. In most insulating materials radiative transfer represents about 1/3 of the total heat flux at the ambiant temperature. The problem is solved with electrical analogy, quadripoles technique and Laplace transform. The modelization brings out two physical character parameters of the material and a coefficient qualifying the thermal exchange between the sample and the environment during the experiment.
capacity of thermal exchange between sample and temperature sensors, which in turn have to transmit the signal to the recording devices. Leiva [ 12 ] used thermogravimetry to determine the activation energy of combustion of fuel oils and compared the
the sample, C p is the heat capacity of the sample, K ( t ) is the thermal exchange coefficient being the calibration function of the measuring system, Δ T S–R , Δ T S–E and Δ T R–E are the temperature gradients between the sample (S), reference
normal situations since the frame structure that holds the PV module is in touch only with the thin sidewalls of the PV module, which has relatively small area. Also, the thermal exchange through side surfaces is neglected because of its small area
