Development and performance evaluation of novel silica gel-coated heat exchanger with high durability and conductivity to improve adsorption water treatment

Abstract

Adsorption water treatment (AWT) has received considerable attention because it can be used to produce freshwater using low-grade heat sources. Furthermore, owing to its nearly consistent desalination performance and high-water recovery rate (>80 %), it has a high potential for use as a minimal liquid discharge process. However, a low freshwater production yield per unit volume of the AWT system is observed because the AWT system uses an adsorbent-packed heat exchanger (APHE), which has a high thermal resistance. In this study, the development and performance evaluation of a novel adsorbent-coated heat exchanger (ACHE) with high durability and conductivity is presented to enhance the heat and mass transfer rates during the adsorption and desorption processes. Binders and spray coating methods are utilized to achieve a uniform coating thickness and highly durable ACHE, and the adhesion strength is investigated using a pull-off test. The physical properties of the composite adsorbent are then examined using argon and water vapor adsorption isotherms, and the thermal conductivity is determined using the transient plane source method. Finally, the performance of the AWT process is evaluated considering the hot-water temperature and cycle time and achieves a significant superiority in the ACHE compared with the APHE.