Mathematical modelingof heat and mass transfer processes in the adsorbers of the air purification system

The present work is devoted to the study of the processes of heat and mass transfer in the adsorbers of the preliminary drying unit of the atmosphere purification system. A mathematical model has been developed that adequately reflects the physical processes at all stages of the adsorption cycle.Algorithms for solving problems and programs for calculating heat and mass transfer processes in an adsorption regenerated installation are obtained, results of parametric calculations of heat and mass transfer processes at each stage of the adsorption cycle and for the entire cycle as a whole are obtained.

Numerical calculation of heat and mass transfer processes in the adsorbers of the air purification system

In this work, a series of parametric calculations was made for the processes of sorption and desorption of water vapor in relation to the conditions of the process of sorption air purification. A mathematical model was developed that adequately reflects the processes of heat and mass transfer in the adsorption unit at all stages of the adsorption cycle. Algorithms for solving problems and programs for calculating heat and mass transfer processes in an adsorption regenerated installation are obtained, results of parametric calculations of heat and mass transfer processes at each stage of the adsorption cycle and for the entire cycle as a whole are obtained.

Steady-State Investigation of Carbon-Based Adsorbent–Adsorbate Pairs for Heat Transformation Application

In this study, the ideal adsorption cycle behavior of eight activated carbon and refrigerant pairs is evaluated. The selected pairs are KOH6-PR/ethanol, WPT-AC/ethanol, Maxsorb-III/methanol, Maxsorb-III/CO2, Maxsorb-III/n-butane, Maxsorb-III/R-134a, SAC-2/R32 and Maxsorb-III/R507a. The following cooling performance parameters are evaluated for all pairs: specific cooling energy (SCE), concentration difference (ΔW) and coefficient of performance (COP) of ideal adsorption cooling and refrigeration cycles. The evaporator temperatures for the applications of adsorption cooling and refrigeration are selected as 7 and −5 °C, respectively. It is found that the Maxsorb-III/methanol pair has shown the highest specific cooling energy and coefficient of performance in a wide range of desorption temperatures; i.e., for the adsorption cooling cycle it has SCE and COP of 639.83 kJ/kg and 0.803, respectively, with desorption temperatures of 80 °C. The KOH6-PR/ethanol and the WPT-AC/ethanol pairs also give good performances comparable to that of the Maxsorb-III/methanol pair. However, the SAC-2/R32 pair possesses a higher concentration difference than the Maxsorb-III/methanol, KOH6-PR/ethanol and WPT-AC/ethanol pairs but shows a lower performance. This is due to the lower isosteric heat of adsorption of SAC-2/R32 compared to these pairs. It is found that Maxsorb-III/methanol, KOH6-PR/ethanol and WPT-AC/ethanol are the most promising pairs for application in designing adsorption cooling and refrigeration systems.

Study of CO2 adsorption and separation using modified porous carbon

Porous carbon and La2O3/porous carbon materials are synthesized for the study of CO2 adsorption and separation by the volumetric method. The synthesized adsorbents are characterized by X-ray diffraction, N2 adsorption–desorption isotherms, Raman spectra and scanning electron microscopy with energy-dispersive X-ray analysis. Characterization results confirm the existence of porosity in the synthesized carbon materials and uniform distribution of lanthanum(III) oxide on porous carbon. The CO2 adsorption capacity for porous carbon and La2O3/porous carbon is 21 and 33 cm3 g−1, respectively, at 298 K and 1 bar. High adsorption of CO2 is obtained for La2O3/porous carbon because of the electrostatic interaction between La2O3 and CO2. Moreover, the N2 adsorption capacity is 2.8 cm3 g−1 for porous carbon and 2.2 cm3 g−1 for La2O3/porous carbon at 298 K and 1 bar. The change in N2 adsorption is due to the decrease in surface area. For La2O3/porous carbon, the selectivity of CO2/N2 is 33.5 and the heat of CO2 adsorption is 36.5 kJ mol−1 at low adsorption of CO2. It also shows constant CO2 adsorption capacity in each adsorption cycle.

Performance Analysis of a Cascading Adsorption Cycle Powered by High-Temperature Heat Sources for Low-Temperature Cooling in Hot Climates

Cascade adsorption refrigeration technology using high-temperature driving heat is a very promising option for low-temperature cooling applications due to the large temperature difference between the heat source and the cold distributed. The present work carried out a feasibility and parametric study in order to analyze the functioning of a cascading adsorption cycle using the working pair zeolite/ammonia in beds operating at high temperatures and activated carbon/ammonia in those operating at low temperatures. At the nominal thermal conditions, namely, heating, condensing, and evaporating temperatures of 280 °C, 35 °C, and (−5) °C, respectively, the coefficient of performance (COP) and the specific refrigerating capacity (SCP) of the cycle were 0.53 and 67.1 W/kg. When the driving temperature is varied from 260 °C to 320 °C, the COP increases by 57% and the SCP by 36%. The performance of the cascading adsorption cycle at negative evaporating temperatures is very satisfactory.