Improvement of humidification–dehumidification desalination unit using a desiccant wheel

Investigations on a solar humidification dehumidification desalination system equipped with various packing materials and multi-stage bubble column dehumidifier

This work presents the theoretical and experimental investigation of a solar-powered humidification dehumidification desalination (HDD) system with different humidifier packing materials and a two-stage bubble column dehumidifier (BCD). Naturally available coconut shells (CS) and coconut shells with drilled holes (CSH) on the surface to improve water permeability were used as packing materials in the humidifier, and their performance was compared with that of commercial-type pall ring (PR) and raschig ring (RR) packings. An in-house developed numerical model of the HDD system in conjunction with a flat plate solar water collector was used in this study. Steady-state experimental results showed that CSH packing exhibited the highest volumetric mass transfer coefficient (0.00852 kg/s), resulting in maximum humidifier efficiency (96%) and freshwater yield (2.16 kg/hr), followed by PR (0.00841 kg/s, 94%, and 2.137 kg/hr), CS (0.00831 kg/s, 90%, and 2.127 kg/hr), and RR (0.0081 kg/s, 81%, and 2.087 kg/hr) at feedwater mass flow rate of 1.5 kg/min and humidifier inlet temperature of 75 [Formula: see text]. Furthermore, transient outdoor test results showed that using a two-stage configuration in a BCD increased the daily average effectiveness to 0.93, as against 0.79 for a single-stage BCD. Employing CSH instead of PR and RR packings in the humidifier reduced freshwater costs by 6.2% and 7.6%, respectively.

Experimental Investigation of Desiccant Dehumidification Cooling System for Climatic Conditions of Multan (Pakistan)

In this study, experimental apparatus of desiccant dehumidification was developed at lab-scale, using silica gel as a desiccant material. Experimental data were obtained at various ambient air conditions, while focusing the climatic conditions of Multan (Pakistan). A steady-state analysis approach for the desiccant dehumidification process was used, and thereby the slope of desiccant dehumidification line on psychrometric chart (ϕ*) was determined. It has been found that ϕ* = 0.22 in case of silica gel which is lower than the hydrophilic polymeric sorbent, i.e., ϕ* = 0.31. The study proposed two kinds of systems, i.e., (i) standalone desiccant air-conditioning (DAC) and (ii) Maisotsenko-cycle-assisted desiccant air-conditioning (M-DAC) systems. In addition, two kinds of desiccant material (i.e., silica gel and hydrophilic polymeric sorbent) were investigated from the thermodynamic point of view for both system types, using the experimental data and associated results. The study aimed to determine the optimum air-conditioning (AC) system type, as well as adsorbent material for building AC application. In this regard, perspectives of dehumidification capacity, cooling capacity, and thermal coefficient of performance (COP) are taken into consideration. According to the results, hydrophilic polymeric sorbent gave a higher performance, as compared to silica gel. In case of both systems, the performance was improved with the addition of Maisotsenko cycle evaporative cooling unit. The maximum thermal COP was achieved by using a polymer-based M-DAC system, i.e., 0.47 at 70 °C regeneration temperature.

Enhancement of PV/T-integrated single slope solar desalination still productivity using water film cooling and hybrid composite insulation

This context is about enhancing the freshwater production of a single slope solar desalination still (SSSDS) using water film cooling over the glass cover and using hybrid natural fibre composite (HNFC) insulation. In contrast to the conventional insulations, we proposed the HNFC insulation; this composite was made of natural fibre Pharsalus vulgaris (6 %) and nano-silica (1 %) with unsaturated polyester resin. In this study, conventional SSSDS and proposed SSSDS with enhanced evaporation and condensation have been designed. The same was built with native materials. A conventional and proposed type SSSDS was subjected to the same experimental condition. The experimental result showed that using water film cooling over glass cover and HNFC insulation at 0.5 cm depth caused a 35% increase in the amount of distilled water when compared with the conventional type SSSDS with polystyrene-Styrofoam (thermocol) insulation. Water film cooling over glass cover and HNFC insulation at 1 cm depth caused a 21% increase in the amount of distilled water when compared with the conventional type SSSDS with thermocol insulation. The conventional type solar desalination still with thermocol insulation at 0.5 and 1 cm depth yields are 1.665 and 1.171 l/m²/day, respectively, and the proposed solar desalination still with water film cooling over glass cover and HNFC insulation at 0.5 and 1 cm depth yields are 2.253 and 1.420 l/m²/day, respectively.

A Novel Humidification Technique Used in Water Desalination Systems Based on the Humidification–Dehumidification Process: Experimentally and Theoretically

In this paper, an experimental and theoretical investigation is performed on a novel water desalination system based on a humidification–dehumidification technique using a heat pump. An ultrasonic water atomizer is used in the humidification process in order to improve the humidification system. In addition to that, a new configuration is employed in the humidification process (hybrid atomization system), which combines the traditional spraying atomization system and the ultrasonic water atomizer. The new humidification system performance is investigated and compared with the spraying water atomizer system in terms of humidification effectiveness and freshwater productivity. The results show that the ultrasonic water atomizer has enhanced and improved humidification effectiveness, and consequently, the productivity of freshwater. The maximum humidification effectiveness and productivity achieved by the ultrasonic water atomizer are 94.9% and 4.9 kg/h, respectively, meaning an increase of 25.2% and 18.8%, compared to the traditional spraying atomization system. The hybrid system increases humidification effectiveness and productivity by 3.8% and 8.2%, respectively, in comparison with the stand-alone ultrasonic water atomizer. A cost analysis was also carried out in this paper in order to perform an economic comparison of different humidification processes (spraying, ultrasonic; and hybrid atomization systems). The minimum production cost of one liter of freshwater amounts to $0.0311 with the spraying system, $0.0251 with the ultrasonic system, and $0.0250 with the hybrid atomization system. These results reveal the profitability of the new configuration.