Numerical and experimental investigation of desiccant cooling system using metal organic framework materials

Abstract

• Modelling of stationary desiccant wheel coated with different metal organic framework adsorbent materials (MIL-100(Fe), MIL101(Cr), CPO-27(Ni), Aluminium fumarate). • Develop new equilibrium equations from the isotherms related to these MOFs. • New experimental data and numerical data for stationary honeycomb desiccant wheel coated with Aluminium Fumarate was generated. • MOF materials coating process and performance comparisons with different humidifier air speeds. Evaporative cooling consumes fraction of the electricity required by the vapour compression refrigeration system but is only effective in dry weather conditions. A promising method for controlling the incoming air humidity is to use a desiccant wheel before the evaporative cooler. Currently, most desiccant cooling systems employ conventional materials like silica gel or zeolites which have low water uptake. Metal Organic Framework (MOF) materials are new class of meso -porous material with high water adsorption capabilities (∼1.5 kg/kgads). Using numerical modelling and experimental testing, this paper investigates the use of four MOF materials namely CPO27(NI), MIL100(Fe), MIL-101(Cr), Aluminium Fumarate and silica gel on the performance of a stationary desiccant heat exchanger (honeycomb Aluminium structure coated with MOF desiccant material) in terms of the Coefficient of performance (COP) and moisture removal rate. Numerical results showed that Aluminium fumarate produced the highest COP of 0.65 with water removal rate of 12.65 g/kg dry air and MIL-101(Cr) produced the highest moisture removal of 15.99 g/kg dry air but with COP of 0.44 compared to silica gel and other MOF materials used. Experimental tests were carried out using honeycomb structure coated with Aluminium fumarate as the stationary desiccant wheel and results were compared to numerical modelling showing good agreement with maximum deviation of 13%. Experimental and modelling results showed that the rate of moisture removal increases with the increase of air inlet humidity and with the decrease of incoming air speed. Also, results showed that the highest moisture removal occur after the first 2 min from starting the dehumidification process highlighting the advantage of using MOF materials.