Investigation of Water Vapour Adsorption on Silica Gel Grains Coated on a Metal Pipe

Abstract

ABSTRACT:The dynamics of water vapour adsorption on silica gel coated on the metal pipe surface is studied. Those systems in which silica grains were used to coat the heat-exchanger pipes were utilized for heat-transfer enhancement in adsorption chillers. A mathematical model of this process, which takes into account the adsorption kinetics, is proposed. Experimental results for different gas velocities are presented in the form of breakthrough curves. They are used to verify the model and to determine the values of parameters characterizing the adsorption kinetics. The model is applied to predict the spatial and temporal variations of water concentration in the adsorbent layer (grains) covering the pipe and to determine the contribution of the internal mass transfer resistance (in grains) to the total mass transfer resistance (in both phases). It is revealed that the external resistance (in gas) is dominant over the internal resistance and that the contribution of the internal resistance increases with both time and gas velocity.

Kinetics of Sorption in Hygroscopic Hydrogels

“…Compared with typical sorption processes using solid-state sorbents such as silica, , zeolite, − and metal–organic framework, ,, the kinetics of hydrogel sorption is distinct due to the presence of gas, liquid, and polymer network. Therefore, conventional approaches by considering the vapor transport only are insufficient to describe the complex interactions during hydrogel sorption. , Figure a shows a schematic of the sorption process where a thin hydrogel layer is placed into a humid environment.…”

Engineering Approach to Modeling of a Sorption Bed of a Single-Stage Adsorption Chiller

“…This situation is demonstrated in Figure 1. The heat transfer in the adsorption bed work cycle is controlled by the porosity ε, which determines the gaseous spaces ratio to the volume of the sorbent bed [11]. The high beds porosity is an important limitation to the sorption processes efficiency, because it generates high resistance to heat flow in the volume of sorbent, due to very low thermal conductivity of the gases (only 0.025 [W•m -1 •K -1 ] for air).…”

“…One of the promising conceptions is to bond the first layer of porous media to the heat exchanger surface with an adhesive material which is characterized by a higher thermal conductivity coefficient than the sorbent and gaseous spaces of the bed volume. The epoxide resins and adhesives based on polyvinyl alcohol PVA have been selected for modifying of the sorption bed construction due to the good thermal conductivity and mechanical strength in humid conditions [9][10][11]. Another conception is to use a polydispersive bed design.…”

Extreme Water Uptake of Hygroscopic Hydrogels through Maximized Swelling‐Induced Salt Loading

“…To meet these different requirements, many sorbent materials have been explored, including hygroscopic salts, [18][19][20] zeolites, [21][22][23] silicas, [24,25] and metal-organic frameworks (MOFs). [3,26,27] However, to date, there is no sorbent that can meet all the above criteria simultaneously.…”