Abstract
An MIL-101(Cr) powder material was successfully prepared using the hydrothermal synthesis method, and then the original MIL-101(Cr) was combined with different mass fractions of CaCl2 using the immersion method to obtain a MIL-101(Cr)/CaCl2 composite material. The physical properties of the adsorbent were determined by X-ray powder diffraction (XRD), an N2 adsorption desorption isotherm test, and thermogravimetric analysis (TG). The water vapor adsorption performance of the metal-organic frameworks MOFs was tested with a gravimetric water vapor adsorption instrument to analyze its water vapor adsorption mechanism. Based on the SIMULINK platform in the MATLAB software, a simulation model of the coefficient of performance (COP) and cooling capacity of the adsorption refrigeration system was established, and the variation trends of the COP and cooling capacity of the adsorption refrigeration system under different evaporation/condensation/adsorption/desorption temperatures was theoretically studied. MIL101-(Cr)/CaCl2-20% was selected as the adsorption material in the adsorption refrigeration system through the physical characterization of composite materials with different CaCl2 concentrations by means of adsorption water vapor test experiments. A closed adsorption system performance test device was built based on the liquid level method. The cooling power per unit and adsorbent mass (COP and SCP) of the system were tested at different evaporation temperatures (288 K/293 K/298 K); the adsorption temperature was 298 K, the condensation temperature was 308 K, and the desorption temperature was 353 K. The experimental results showed that COP and SCP increased with the increase in the evaporation temperature. When the evaporation temperature was 298 K, the level of COP was 0.172, and the level of SCP was 136.9 W/kg. The COP and SCP of the system were tested at different adsorption temperatures (293 K/298 K/303 K); the evaporation temperature was 288 K, the condensation temperature was 308 K, and the desorption temperature was 353 K. The experimental results showed that the levels of COP and SCP decreased with the increase in the adsorption temperature. When the adsorption temperature was 293 K, the level of COP was 0.18, and the level of SCP was 142.4 W/kg.
Highlights
Adsorption refrigeration is an environmentally friendly refrigeration method.Adsorption refrigerators can use natural working fluids as refrigerants and have zero OzoneDepletion Potential (ODP), which has attracted widespread attention in recent years
The results showed that the coefficient of performance (COP) of Metal-organic frameworks (MOFs)/water was generally higher than that of MOF/ethanol, but the performance of MOF/ethanol was better than that of MOF/water
Composite adsorption and materials were applied in an adsorption refrigeration system, and the results showed that the SCP was 631 W/kg and the COP was 0.83
Summary
Adsorption refrigeration is an environmentally friendly refrigeration method. Adsorption refrigerators can use natural working fluids as refrigerants and have zero Ozone. Garzon-tovar [12] synthesized a new solid composite adsorbent by combining metal organic framework UiO-66 and hygroscopic salt CaCl2 through spray drying, improving the water absorption capacity of the original material. Calcium chloride is a very hygroscopic salt, it has a strong affinity for water It has been reported in the literature that when salt is combined with activated carbon, silica gel, zeolite and other porous materials (matrix) to form a composite material, its performance is significantly improved. Chan [16] soaked zeolite 13X in 46% CaCl2 solution, In this paper, MIL-101(Cr)/CaCl2 composite materials with different CaCl2 concentrations (10%, and the adsorption capacity increased by 0.4 gH2O /gads at 25 and 75 ◦ C and 870 Pa. 20%, 30%) were prepared by the dipping method. The pair of working media for the adsorption refrigeration system to test the system performance at different evaporation/adsorption temperatures
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