Investigation On Resorption Cycle For Refrigeration And Power Conversion Based On Metal Halide Consolidated Compound Adsorbent

In this paper, based on heat and mass transfer enhancement of metal halide, resorption system for refrigeration and power conversion is proposed. The concerning system is established correspondingly. The resorption system is driven by the low grade heat source. The refrigerant desorbed by HTS bed expands in the scroll expander for power generation while desorption heat of LTS bed produces cooling effect. Because desorption heat is larger than vaporization enthalpy of the refrigerant, cooling capacity of the resorption system is theoretically larger than that of conventional adsorption system. Simultaneously, the resorption system takes the advantages of low system pressure and good capability of anti-vibration. The resorption system for refrigeration and power conversion is mainly aimed at the utilization of low temperature heat source and improving heat utilization efficiency. Details are as follows:Static heat and mass transfer performance of different granular metal chloride and consolidated composite adsorbent are investigated. Results show that thermal conductivity of granular metal chlorides are very low, which ranges from 0.24-0.31. NH4 Cl, Ca Cl2 and Mn Cl2 are the optimum choices for the LTSs, MTSs and HTSs. For consolidated composite adsorbent, thermal conductivity for different salts decreases, while the density of adsorbent and the percentage of salt decrease. For different salts with the density of 450 kg/m3, thermal conductivity ranges between 0.61 to 1.87 W/(m·K), and for the density of 550 kg/m3, thermal conductivity ranges between 0.84 to 2.13 W/(m·K). Considering the salts with different equilibrium reaction temperature for adsorption/desorption, NH4 Cl and Fe Cl3 show the optimum data for the thermal conductivity in LTSs and HTSs. The data for two types of MTS salt, i.e. Sr Cl2 and Ca Cl2, are similar. Permeability of composite adsorbents is around 10-10-10-13 m2. The optimum choices for LTSs, MTSs, and HTSs are Na Br, Ca Cl2 and Mn Cl2, respectively. Dynamic heat and mass transfer performance of different granular metal chloride and consolidated composite adsorbent is investigated. For a given compact adsorbent, the thermal conductivity increases with an increasing proportion of ENG, an increasing compact adsorbent density, and an increasing adsorption quantity. For different salts, thermal conductivity ranges from 0.62 to 2.4 W/(m·K) and 0.89 to 2.98 W/(m·K), respectively, for the densities of 450 and 550 kg/m3. It can be observed that the permeability decreases for the adsorbents with increasing density, and permeability of the different salts ranges from 10-14-10-10m2. The values decrease when the adsorbent rate for both the diverging and converging modes increases. Compared with the experimental results of maximum SCP, cooling capacity and COP,the errors of SCP cooling capacity and COP for dynamic heat and mass transfer properties are 9.1%, 8.3% and 12% while static values increase by 42.8%, 41.4% and 36%, respectively. Adsorption refrigeration performance decreases significantly when considering the errors of thermal conductivity and permeability in the adsorption and desorption process. Static thermal conductivity and permeability will cause the trend of excessive increment and less time for cooling capacity and SCP. Comparably, dynamic thermal conductivity and permeability will coordinate the refrigeration performance accurately. To seek for the adsorbent with higher heat and mass transfer performance while keeping the permeability, heat and mass transfer properties as well as adsorption performance of consolidated composite Ca Cl2 with matrix of ENG-TSA are investigated. Thermal conductivity and permeability of composite adsorbent with ENG-TSA show the same trends as that of ENG when considering mass ratio of Ca Cl2 and density. The highest thermal conductivity of plate sample is 88.1 W/(m·K) for the sample with the bulk density of 300kg/m3 as well as salt mass ratio of 50%. For different mass ratios and different bulk densities, thermal conductivity ranges from 23.5 to 88.1 W/(m·K). For different bulk density and mass ratios, permeability of consolidated composite Ca Cl2 /ENG-TSA ranged from 9.31×10-10 to 3.05×10-14m2. For Mn Cl2 composite adsorbent, thermal conductivity varies form 20.3 to 80.6 W/(m·K), permeability range from 8.02×10-11 to 1.01×10-14 m2.For consolidated Ca Cl2/ENG-TSA with 80% salt, the maximum cycle adsorption quantity reaches 0.4455 g/g under the condition of evaporating temperature of 15 oC, condensing temperature of 25 oC. The cycle adsorption quantity of consolidated composite Ca Cl2 doesn’t change very much with the change of density as well as the mass ratio of salt. The cycle adsorption quantity of consolidated Ca Cl2/ENG-TSA is a little higher than that of consolidated Ca Cl2/ENG.After enhancing heat and mass transfer performance of adsorbent, resorption system for refrigeration and power conversion is proposed and analyzed. It indicates that resorption cogeneration cycle enjoys a good performance. The highest power and refrigeration exergy efficiency are 0.69 and 0.29, respectively. The highest COP of system is bout 0.77. Under the condition of 150 oC superheating source temperature, the total exergy efficiency of Ba Cl2-Sr Cl2-NH3 working pair is as high as 0.9. Compared with Goswami cycle, total exergy efficiency of the resorption cogeneration system is improved by about 40%-60%. For solar energy and waste heat, resorption system for power and refrigeration cogeneration is prospective for meeting the needs of power and refrigeration.Since the scroll expander is modified from the vehicle scroll compressor, the compressed air power generation experimental rig is established to investigate and analyze the performance of scroll expander by inlet and oulet pressure and temperature. When the pressure of turbine inlet varies from 0.6 to 1 MPa, the isentropic efficiency and work to power efficiency maintain at about 60% and 80%. The work output and electricity increase with the increment of expander inlet temperature and pressure. Internal efficiency for power generation is 53% when turbine inlet pressure is 1 MPa. Working pairs of Mn Cl2-Ca Cl2-NH3 with matrix ENG-TSA is tested for cycle adsorption quantity under the condition of heat source temperature, cooling temperature and refrigeration temperature. Simulaiton results show when heat source temperature is 150 oC and the evaporating temperature varies from-10 oC to 20 oC the total energy efficiency of the resorption system for refrigeration and power conversion increases from 0.316 to 0.376 and exergy efficiency decreases from 0.402 to 0.391.After simulation and design, resorption system for refrigeration and power conversion is established and investigated. Results show that COP and SCP of the system change with heat source temperature. When heat temperature is higher than 160 oC, sensible load of the system increases, which means keep heating HTS adsorption bed is not able to improve the system performance. For refrigeration temperature is 15 oC and 10 oC, COP of the system ranges from 0.284 to 0.396 and 0.277 to 0.368, respectively. SCP of the system ranges from 98.6 to 340 W/kg and 91.9 to 321W/kg, respectively. The maximum power output is nearly 253 W and the overall average value is 82.3 W lastes for 114 s. The total energy efficiency increases from 0.293 to 0.417 then decrease to 0.407 and exergy efficiency increases from 0.12 to 0.16. The highest power and refrigeration power are 253 W and 2.98 k W when the heat source temperature is 160 oC.