دراسة تجريبية وعددية لنظام تحلية مياه بالامتزاز باستخدام مصادر حرارة منخفضة

Experimental and Numerical Study of an Adsorption Water Desalination System Utilizing Low-grade Heat Sources

Abstract

Drinking water scarcity is a widespread issue in several countries, affecting millions of people’s life quality. Although desalination technologies can help solving the problem of water scarcity, they need a lot of energy and to emit a lot of (CO2). This study was carried out constructing a test apparatus and MATLAB SIMULINK model for the adsorption desalination and cooling system, monitoring the system’s performance under various operating conditions, and determining the best operating conditions. The system was investigated experimentally and numerically under steady conditions.
The test rig consists of main parts and accessories. The adsorption bed, condenser, and evaporator are the main components of the system. While the pumps, tanks, and measuring devices with various kinds are secondary parts.
MATLAB Simulink has been utilized in this work to simulate the different components of the proposed system using Silica-gel and water as an adsorption pair. Due to the lab and cost limitations, the experimental facility contains only one adsorbent bed in addition to the condenser and evaporator, while the numerical model simulates two adsorbent beds besides the condenser and evaporator.
The simulation model has been validated with previously published experimental research. The performance of the system is monitored by its outputs, which are the specific daily water production(SDWP) and the specific cooling power(SCP). The effect of the working fluid temperatures in the condenser, evaporator, and bed, as well as the half cycle time, has been studied.
The experimental results showed that the SDWP and SCP of the system increase with the hot bed temperature by (2.43-6.21 l/kgads/day), (87.95-100.88 W/kgads), respectively and with the temperature of the evaporator by (4.5-6.3 l/kgads/day), (72.43-103.47 W/kgads) respectively, while they decrease with the water temperature of the condenser by (6.03-5.49 l/kgads/day), (99.59-98.3 W/kgads) respectively and with the half-cycle time by (4.59-2.97 l/kgads/day), (95.71-72.43 W/kgads) respectively.
Rising the heating temperature from (70°C to 90°C) results in a (60 %) growing in (SDWP) and a (12.8 %) increase in (SCP). (SDWP) and (SCP) have been improved by (28.5 %) and (30 %), respectively, when the evaporator water temperature raises from (30°C to 38°C). (SDWP) and (SCP) values are reduced by (55 % and 32 %), respectively, when the half-cycle period is increased from (300 to 500 sec).
The results highlight the potential of producing potable water and cooling system utilizing low grade temperatures helping millions of people around the world.