| Energy consumption of the air conditioning systems in data centers has reached nearly 40%in total presently,which indicates great energy saving potential.Yet,conventional mechanical refrigeration systems,still widely applied in existing data centers,display poor performance when both considering cooling needs and energy conservation.Hence,transformation of refrigeration in current data centers is necessary.So far right now,integration of evaporative cooling and mechanical refrigeration has been proved effective on stabilizing the energy saving operation of data centers.However,evaporative cooling chillers do not present ideal results,compared with those in dry areas,when employed in areas with hot and humid climate,and thus the combining systems maintain majority of hours in mechanical refrigeration,which drastically reduces the utilization of natural cooling resource such as water and air with low wet bulb temperature.Moreover,there still exists some technical problems yet to be resolved originating from this hybrid approach.Coupling application of solid desiccant dehumidification and evaporative cooling technology in southern areas with hot and humid climate is proposed in this thesis,which aims at elevating the efficiency of evaporative cooling system and enlarging its applicable areas.In regard of this,a prototype of solid desiccant dehumidification system has been constructed by preliminary design and tested within hot and humid climate,after which dehumidification performance,temperature rise,and evaporative cooling efficiency of the prototype were investigated.It is concluded that the maximum average dehumidification capacity and maximum cumulative dehumidification capacity were obtained at 25.2℃ and 65.6%RH by the doublestage solid desiccant dehumidification box A,which were 1.6g/kg and 154g/kg respectively,while the peak average dehumidification efficiency and maximum dehumidification efficiency hit 26.7%and 14.4%independently at 14.1℃ within 59.7%RH.Moisture adsorption rate and moisture ratio became stable after 300 minutes’ operation.The maximum moisture adsorption rate（23.7%）and maximum average moisture adsorption rate（17.6%）were achieved by the double-stage solid desiccant dehumidification box A at 25.2℃ with 65.6%RH.Meanwhile,the established mathematical models presented considerable similarity compared to the data acquired within approximately 10%relative error.Though the double-stage solid desiccant dehumidification box A displayed better dehumidification performance,yet the temperature rise was higher.The maximum average temperature rise of the silica gel and the processed air reached 4.0℃ and 3.4℃ correspondingly at 25.2℃ with 65.6%RH.97%of adsorption heat generated during dehumidification was transformed to the heat storage of silica gel while only about 3%went to the heat gain of the air.When adopting the dew point efficiency in calculation,the systematic efficiency could be increased by 0.8%～7.3%at certain working conditions and it is found that the evaporative cooling efficiency would decline with the rising of dew point temperature.Taking the data center with all fresh air ventilation as an example,the coupling system could save 1.22×108kJ comparing with the conventional vapor compression refrigeration system from May to September as well as 21468.8 yuan in the first year of operation,and also conserve the operation cost of 33106.8 yuan in each operation year from May to September.This thesis started a new prototype of solid desiccant dehumidification device and proved the feasibility of a desiccative evaporative cooling system with this prototype in hot and humid areas for enhancing the system efficiency,and at the same time,referenced for its application. |
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