Astudy On The Evaluations And Applications Of The New Composite Adsobent In The Adsorption Beds

The key in the adsorption refrigeration is to shorten the refrigeration cycles and increase the cooling capacity within a fixed unit of time.Currently,domestic and international studies on this issue mainly focus on these three aspects:the performance of the adsorption refrigerant pair,the methodology of the refrigeration cycling,and the optimization in the adsorption bed structures.The performance of the adsorbent is particularly important for the adsorption refrigeration system.The disadvantages of using the chemical adsorbent include the poor performance in transferring the heat and mass,and swelling during the adsorption cycling process.With the additions including a porous medium and a high thermal conductivity material,the composite adsorbent obtains performance improvements in heat and mass transfer,and adsorption process.In this paper,with the goal of improving the heat and mass transfer and adsorption performance of adsorbents,a new composite adsorbent was proposed.The analyses include evaluating the influence of factors,like the density,on the heat and mass transfer and adsorption performance of the composite adsorbent in the preparation process.The simulation study for the adsorption process was performed with COMSOL software.The best preparation process was achieved by the analysis on the simulation study,and the effects of different preparation processes on the refrigeration performance.The main work of this paper is as follows:?1?The usage of the calcium chloride and the expanded graphite as raw materials was applied,with the sucrose as a binder and the phosphoric acid as an activator.A new composite adsorbent was prepared by the carbonization activated pore-forming method.The orthogonal experiment was based on each factor with different levels in the preparation process.?2?The adsorption capacity of ammonia in each group of composite adsorbents was measured.It was found that,the density,the activation temperature,and the mass concentration of the calcium chloride solution had significant effects on the adsorption capacity of the composite adsorbent.The maximum adsorption capacity per unit mass was 0.592g?g^-1.?3?The thermal conductivity and permeability of the composite adsorbents were measured.It was found that the density and the activation temperature of each factor had significant effects on the thermal conductivity,and the highest thermal conductivity reached 3.48W·m^-1·K^-1;density and activation.The variable time also had a significant influence on the permeability,with a maximum permeability of1.127×10^-9m².?4?The physical model and mathematical model of the adsorption bed was established.The numerical simulation analysis was conducted on the adsorption process of the three groups of samples with orthogonal experiment and the adsorption,the thermal conductivity,and the permeability of three groups with the estimated unit volume of refrigeration SCP.The parameters of the best preparation process were determined by comparisons:the adsorbent density 140kg?m^-3,the mass ratio of phosphoric acid sucrose 0.6,the activation temperature 500°C,the activation time 3 h,and mass concentration of calcium chloride solution 50%.In the temperature field,the change of the adsorption amount and the change of the adsorption reaction rate were analyzed for this group of samples.Compared with the existing composite adsorbent,the completion time in the adsorption reaction was shortened by 2 to 3 times roughly.