Research Of Composite Absorbent And Adsorbent Bed Used In Adsorption Refrigeration Driven By Medium Temperature Waste Heat

In order to improve the performance of adsorbent bed and reliability of adsorption refrigeration system driven by internal combustion engine exhaust waste heat,some research and exploration,which are focused on high-performance composite adsorbent,the installation method between absorbent and adsorbent bed, the performance of single-tube adsorbent bed and new refrigeration unit,were done. Main results are as follows.1.A zeolite-based composite absorbent was preparated and recommended,with the formula:13X zeolite 100(mass fraction),attapulgite clay 40,blister 15,expanded graphite 30,350℃sintered;2.With the orthogonal test and stepwise regression method,the empirical was derived and validated by experiment,The equations about of the thermal conductivity and adsorption performance of composite adsorbent with the 4 factors above are as follows:Thermal conductivity:λ=0.379-0.857a-0.771b+0.468c-8.6×10^-5d+1.481a²+1.515b²+0.0336c² W/(mK) Adsorption performance(by weighted evaluation method):χ=9.038-0.487a-8.982b-1.770c-0.001d-4.995bc+16.799b²+0.0152a²b-0.435a²c+0.512b²c Where a,b,c are mass percent of attapulgite clay,blister,expanded graphite,d is the sintered temperature(℃).3.Bonding method is proposed to reduce the contact thermal resistance between the absorbent and the heat transfer surface of adsorbent bed.This bonding method can not only reduce the thermal stress,which is generated by the difference of linear expansion coefficient between the absorbent and the metal heat exchanger,but also can enhance the reliability of the adsorbent bed.The results of experiments show that the silicone rubber added nano-Sic is a good adhesive for sorbent and adsorbent bed.4.In the single-tube adsorption refrigeration test-bed,the effects to the adsorption refrigeration performance of composite absorbent and bonding methods are tested.The tests show that the response time by using composite adsorbent will be shorten about 12.9%than pure zeolite.The response time by using the new bonding methods will be shorten about 27.4%than bulk methods.This will effectively result in the cycle time of system be shorten.5.A new type of adsorption refrigeration unit and its application systems are proposed,which combines the features of heat pipe and the floating head heat exchanger.Lumped parameter method and Simulink are used to simulate the performance of system,which consists of two new units.The operation law of the adsorption refrigeration system and the influence of operating parameters to adsorption refrigeration system were studied.The results show that the capacity of refrigeration system will be weakened with the raise of heat source temperature when the heat source temperature overrun an extremum;the increase of evaporation temperature,or the decrease of cooling temperature,or the increase of thermal conductivity of sorbent,will help to improve the capacity of refrigeration system;The ratio between adsorption time and desorption time is related to the cycle periodic time, and the adsorption time is usually longer than desorption time,it takes up about 60% of cycle time.