| Constant humidity system is required to regulate the preservation microenvironment of cultural relics in small independent display cases.The constant humidity system continuously consume water in humidification process.To maintain normal operation of the constant humidity system,it is necessary to replenish water into the water tank.Manual water replenishment is time-consuming and laborious,and it will increase the possibility of cultural relics being damaged due to failing replenishing water in time.Air is rich in water vapor.It can be an inexhaustible source of water for the constant humidity system.Many devices for extracting water fro m air has been developed at home and abroad so far.Most of them are based on refrigeration condensation.These devices have the advantages of small size and simple structure,but they are not suitable in low humidity environment.On the basis of comparison among various methods for extracting water from air,the following works were carried out to invent a compact device of extracting water from air for small constant humidity display cases.(1)To meet the requirements of safe and non-toxic use of museum equipment,silica gel is selected as adsorbent for its stable chemical properties,low regeneration temperature and non-corrosiveness.The water vapor is adsorbed by silica gel in adsorption process and released by heating in regeneration process.The released water vapor is cooled and condensed.A new structure of air-cool condenser was designed,and the radial flow adsorber was chosen.Finally,a compact device of extracting water from air for small constant humidity display cases was designed.(2)The operation mode of the device was determined by preliminary experiments,in which the driving force of air in regeneration process is caused by natural convection.Then the experiments were conducted under different inlet air temperature,inlet air relative humidity,adsorber structure and heating power.According to the experimental results,several conclusions can be drawn.With the increase of relative humidity of inlet air,the amount of produced water increases,and the inlet air temperature has little effect on the device’s performance.With the increase of heating power,the amount of produced water increases firstly due to the increase of outlet air humidity of the adsorber,and then decreases due to the insufficient heat exchange in condenser as the restriction of heat rejection capability of the condenser.With the increase of heating power,the desorption time decreases,and the water produced per energy consumption increases first and then decreases.When the water produced meet demand,the heating power of optimal water produced per energy consumption should be selected.Reducing the central channel’s diameter can increase the amount of silica gel in adsorber and thus increase the amount of produced water.According to the experimental results and water replenishment demand,the device can be used as the humidification water source for small cultural relics display cases.(3)A dynamic heat and mass transfer model was established to study the influences of adsorber and heating power on water production.The results showed that reducing the adsorber height and increasing the thickness can improve the performance of the device.However excessive thickness of the adsorber will lead to deterioration of heat transfer and excessive heat dissipation through the external insulation layer,resulting in a decrement of the water produced per energy consumption.When the dimensionless height(the ratio of adsorber height to radius of the central channel)is 2,the dimensionless inner radius of the annular channel(the ratio of the annular channel’s inner radius to the central channel’s radius)is 4,and the heating power is 20 W,the energy utilization ratio is the highest.When the heating power is 25 W and the desorption time is 14046 s,the energy utilization ratio of the existing device is the highest. |
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