Evaluation of minimum desorption temperatures of thermal compressors in adsorption refrigeration cycles

The purpose of this paper is to identify the minimum desorption temperatures required to operate thermally driven adsorption beds of a solid sorption refrigeration system. The method is based on the evaluation of uptake efficiency of the adsorption bed and estimating there from conditions under which the compressor ceases to provide any throughput. The difference in the densities of the refrigerant between the inlet and outlet, the adsorption characteristics of the adsorbate-refrigerant pair and the void volume in the thermal compressor are the contributors to the manifestation of the desorption state. Among them, the void volume is a controllable parameter whose role is analogous to the clearance volume in a positive displacement compressor. The methodology has been tested out with three systems, namely, silica gel + water, activated carbon fiber + ethanol and activated carbon + HFC 134a systems. It is shown that waste heat at as low as $60^o C$ can operate these systems which make them good energy conservation devices through recovery of low grade process waste heat

The Effects of a Low-Level Boron, Phosphorus, and Nitrogen Doping on the Oxygen Reduction Activity of Ordered Mesoporous Carbons

In order to elucidate the role of B, N, and P dopants in carbon materials on the kinetics of oxygen reduction reaction (ORR) and to provide a fair comparison of the effects of each dopant, a series of ordered mesoporous carbons (OMCs) with low concentration of heteroatoms ( lt 1 at%) has been prepared. Doped OMCs were characterized using X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), Raman spectroscopy, X-ray powder diffraction (XRD), and N-2 physisorption measurements. Comparative study of the ORR activity of these materials in alkaline solution was performed using rotating disk electrode voltammetry. The experiments evidenced that, compared to non-doped OMC, charge transfer kinetics was improved independently on the nature of the heteroatom. The decrease of the ORR overvoltage and the increase of the mass activity upon doping are similar for B and P and less prominent for N. On the other hand, OMCs doped with low levels of B and N were found to be selective for O-2 reduction to peroxide, while for P-doped OMCs, the apparent number of electrons consumed per O-2 molecule was up to 3.1. Experimental measurements were complemented by density functional theory (DFT) calculations