| Solid-gas sorption refrigeration technology is kind of green energy-saving andenvironment-friendly refrigeration technique powered by low grade thermal energy, which ispaid more attention by many researchers in the area of low grade heat recovery and sustainableenergy utilization. However, the low efficiency is still a bottleneck that shall be solvedurgently.In this paper, the double-effect and double-way thermochemical adsorptionrefrigeration system with adsorption and resorption technology and internal heatrecovery was set up, based on the double-way thermochemical adsorption refrigerationcycle with adsorption and resorption technology, and the double-effect thermochemicaladsorption refrigeration cycle with heat recovery. The working conditions, experimentalprocedures and result characteristics were studied deeply from the point views ofadsorption working pairs, thermodynamic and performance analysis for double-effectand double-way thermochemical adsorption refrigeration cycle, and the features andkey points of this novel cycle were concluded. Moreover, the overall calculation, theheat transfer calculation, the pressure drop calculation along path and stress checkingcalculation involved in the design of double-effect and double-way thermochemicaladsorption refrigerator, and the layout, composition and theory of devices ofdouble-way thermochemical adsorption refrigeration and double-effect and double-waythermochemical adsorption refrigeration, were introduced. The composite adsorbentusing expanded graphite was applied in the systems of double-way thermochemicaladsorption refrigerator and double-effect and double-way thermochemical adsorptionrefrigerator to enhance the ablity of heat transfer. For the double-way thermochemicaladsorption refrigeration cycle, two cold outputs as the adsorption refrigeration andresorption refrigeration were available at the expense of only one heat input, which wastestified by experimental result. For the double-effect and double-way thermochemicaladsorption refrigeration cycle, four cold outputs were achieved at the expense of onlyone heat input, whose higher system COP was available either. As for the optimum ofdouble-effect and double-way thermochemical adsorption refrigeration cycle, there aretotally three methods: one is the new heat recovery process; another one is theintegrated adsorption process in place of normal adsorption process; the last one is themass recovery process between the high temperature salt and middle temperature salt.Besides, the numerical simulation model for the double-effect and double-waythermochemical adsorption refrigeration cycle powered by low grade heat source wasalso set up, which was based on the kinetic governing equations for adsorptionprocesses and resorption processes, combined with the energy conservation equationand momentum conservation equation. The differential algebraic equations with indexof2was formulated and solved. In addition, the dynamic simulation models for theadsorber/desorber using fin tube heat exchanger were set up also, whose calculationresults comply with the real working conditions very well through the solutions of partial differential equations. The relationship between the system COP with thestructure of adsorber/desorber and kinds of salts was analysed in detail. The simulationresults reveal that the theoretical COP can reach2.0and the calculation COP can be1.3~1.5on the condition of fine matchings between parameters. The experimental resultwas that the experimental COP can be1.1~1.2at the desorption temperature of260oC,heat sink temperature of30oC, refrigeration temperature of10~15oC, which is withinthe error of20%compared with the simulated data. The direction and methods toimprove COP further were provided through the comparsion of simulated data with theexperimental data. The main conclusions were as the follows:（1） For the double-way thermochemical sorption refrigeration cycle using theworking pairs of barium chloride and manganese chloride, the system COP canbe0.703, SCP can be225W·kg-1, at the desorption temperature of160oC, heatsink temperature of30oC, refrigeration temperature of15oC. Moreover, for thiscycle, there exists good matching between middle temperature salt and lowtemperature salt. when the average global conversion reaches the peak, COP isalso maximal. In the same time, the error of molar numbers of adsorptionprocess and resorption process is within5%, which means the cycle can runhigh efficiently and stably.（2） The comparsion of simulated data with the experimental data of double-effectand double-way thermochemical adsorption refrigeration cycle reveals that theerror of difference of simulated COP with experimental COP is within20%under the same desorption temperature and heat sink temperature and differentrefrigeration temperature. Following the increasing of refrigeration temperature,the increase range is increasing for both the simulated COP and experimentalCOP. Under the same desorption temperature, following the increasing ofrefrigeration temperature, the temperature difference between the simulatedCOP and experimental COP increases under the same refrigeration temperature.Due to the global conversion during simulated process is less than that duringexperimental process, at the refrigeration of10oC and15oC, the optimum cycletime of simulated adsorption and resorption refrigeration process is greater thanthat of experimental adsorption and resorption refrigeration process. But at therefrigeration temperature of0oC and5oC, because the pressure differencebetween the reactors is relatively smaller, the experimental reaction time islonger than the simulated data.（3） For double-effect and double-way thermochemical adsorption refrigerationcycle, the effective reaction time is reduced a lot by the new heat recoveryprocess. Because the pressure difference becomes bigger, the desorption processbetween middle temperature salt and low temperature salt is quicker than thatbetween middle temperature salt and condenser. Moreover, the new heatrecovery process can improve the global conversion effectively. The new heatrecovery process lower down the desorption temperature and speed up thereaction process, and the mass recovery process becomes better either, whicharebeneficial to the improvement of global conversion. As for the new heatrecovery process, the global conversion can reach0.8, which is improved60%. （4） For the double-effect and double-way thermochemical adsorption refrigerationcycle, the COP can be improved5%by the integrated adsorption process.Moreover, following the increasing of refrigeration temperature, the COPincrease. And the real meaning of integrated adsorption process lies in theguarantee of the normal output of the adsorption process, which could make thesystem operate normally and continously.（5） For the double-effect and double-way thermochemical adsorption refrigerationcycle, the mass recovery between the high temperature salt and middletemperature salt makes ammonia in the dead volume of high temperatue salt beddesorb to the MTS, which makes the cooling capacity between the lowtemperature salt and high temperature salt bigger; at the same time, the globalconversion in middle temperature salt is improved, which are good to theincreasing of system COP. Both the theorical analysis and experimental resultshows that the mass recovery process between the high temperature salt andmiddle temperature salt can improve COP10%.In a word, based on the double-way thermochemical adsorption refrigeration cyclewith adsorption and resorption technology, and the double-effect thermochemicaladsorption refrigeration cycle with heat recovery, the numerical and experimentalresearch on the double-effect and double-way thermochemical adsorption refrigerationcycle powered by low grade heat source was carried on and kinds of conclusions andachievements were available, which provided the key foundation for the furtherresearch and development of the topic. |
PDF Full Text Request