Development and study of efficiency of ecologically safe solar adsorption refrigerating unit

Abstract

Performance of solar refrigerating units using ammonia, methylamine, ethylamine, dimethylamine, methanol, and ethanol as refrigerants (adsorbates) and activated carbon as adsorbents has been studied. A mathematical model has been built to determine the level of thermodynamic perfection based on simplified theoretical operation cycle and gradual integration of experimental and calculated values of daily variation of the key parameters of the refrigerating unit. A solar power unit where horizontal insolating tubes and plane mirror concentrators are used has been built and successfully tested.One way of utilizing solar energy (radiation) for refrigeration is to use ecologically safe solar adsorption refrigerating units (SARU).Operation of such units is based on the physical adsorption process in which the molecules of a gaseous refrigerant cluster up over the solid surface of the sorbent, followed by condensation, upon cooling, of the vapor of the refrigerant in the porous structure of the sorbent. This process is reversible, i.e., when heat energy is supplied, the refrigerant (adsorbate) is desorbed from the adsorbent.The flow diagram of the SARU does not differ from that of "dry" solar sorption units [1]. The presence of the solid sorbent predetermines the periodicity (cyclicity) of operation of such a unit. During the day, due to solar heating in the generator, the refrigerant is released (desorbed) from the saturated adsorbent and is accumulated in a receiver upon liquefaction in a condenser. During the night, the refrigerant is adsorbed as the adsorber cools off, whereupon cooling effect is produced in the evaporator.In the SARU, ammonia (NH 3 ), methylamine (CH 3 NH 2 ), ethylamine (C 2 H 5 NH 2 ), dimethylamine (CH 3 ) 2 NH, methanol (CH 3 OH), and ethanol (C 2 H 5 OH) can be used as refrigerants-adsorbates and activated carbon, as adsorbents.In the process of producing activated carbon, hydroxyl (-OH) and carboxyl (-COOH) groups may form on its surface, so the carbon may be both nonpolar and polar and exhibit properties of cations, anions, or ampholytes.The adsorbates containing electronegative elements (oxygen, nitrogen, etc.) may form associates (micelle) owing to formation of hydrogen bonds and the amine and alcohol molecules may exhibit diphilic properties due to polar functional groups (-NH 2 and -OH) and nonpolar radical (-R); the molecules of the surface-active substances may form associates depending on the polarity of the surrounding phase. Having dipole moments, the adsorbates also may form associates on account of electrostatic interaction of the dipoles [2].Based on their basicity strength, the adorbates can be arranged in the following order: C 2 H 5 NH 2 > (CH 3 ) 2 NH > > CH 3 NH 2 > NH 3 > C 2 H 5 OH > CH 3 OH.The base is an electron donor (nucleophile) [3]. Presence of carboxyl groups (-COOH) on the carbon surface facilitates formation of stronger bonds with strong bases.

Sectional automatic adjustment of catalyst layers in gas and liquid phase reactors

“…Displacement reactors are devices with an elongated body (channel) providing directional movement and mutual mixing of the reaction mass. There are many traditional factors and methods of influencing the process such as the hydrodynamic situation in the reactor, the thermal conditions of the chemical process, the conditions of heat exchange, the presence of a catalyst, the method of organizing the process, changing of the processes over time, the design features of the apparatus, etc [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. The most promising areas of intensification of hydrodynamic and diffusion processes, as well as activation of reactions and influence on the conversion degree of reaction products are considered by the authors to be the ability to generate certain frequency radiations at the micro level contributing to the resonant reactions and the highest degree of energy transfer, and the creation of a developed flow mode and close to ideal flow structures of reaction masses at the macro level which may be accompanied by impulse-vibration modes of oscillations of the catalyst layers with the subsequent energy transfer from the catalyst to the reaction products which results in a sharp activation of the mutual mixing of the reaction products and prevents the catalyst layers from coking.…”