Study On Marine Rotary Desiccant Air-conditioning System

The rotary desiccant air-conditioning system can process humidity load using low-gradeenergy such as industrial waste heat and solar energy, and hence has remarkable energy-savingeffect. From the research status at home and abroad, it can be found that most of the studies ofrotary desiccant air-conditioning system were focused on its application on land building, andfew on ships. In this paper, the application of rotary desiccant air-conditioning system on shipswas proposed. The scheme of a one-rotor two-stage marine desiccant air-conditioning systemwas constructed, and an experimental rig of the system was established for further study aboutsystem’s performance.Firstly, a system scheme of one-rotor two-stage marine desiccant air-conditioning wasconstructed. The silica-gel desiccant was selected for the rotary wheel to deal with humidity load.One-rotor two-stage desiccant model was adopted as the system’s circulating mode. The systemincluded two air flows, i.e., process air flow and regeneration air flow. Process air flow wasdehumidified twice by desiccant wheel, and then cooled by seawater after each dehumidifyingprocess, and finally further cooled to reach the required supply-air condition by the auxiliarycompression-type refrigerating unit. Fresh air and return air were mixed as the process air beforethe first dehumidification in desiccant wheel. Regeneration air was extracted from cabins andheated by saturated steam which produced by exhaust-heat boiler, and then sent into tworegeneration areas in desiccant wheel, respectively.Secondly, an experimental rig of a one-rotor two-stage marine rotary desiccantair-conditioning system was established, which maximum supply air volume was1000m3/h. Inthe rig the regeneration air was heated by electric heater instead of steam; and the simulatedmarine environment was produced by a unit which could provide constant temperature andhumidity of air as desired. Two units which could provide constant temperature of water wereused to imitating the inter-cooling of seawater and auxiliary cooling of compression-typerefrigerating unit. Meanwhile, the parameters of air state and cooling water were measured bythermocouples and humidity/temperature sensors, which measurement errors were rectified.Finally, the dehumidification and thermal performance of the one-rotor two-stage marinedesiccant air-conditioning system were studied experimentally using the experimental rig Duringexperiments, two typical air conditions were selected for the inlet process air in accordance withthe design conditions of indoor and outdoor air. Under one condition the fresh air ratio was60%, and another condition100%. During experiments the supply air volume was set to be500,600,700and800m3/h respectively. Dehumidification and thermal performance were investigatedwith different rotational wheel speed, process air volume and seawater temperature respectively.It was shown by the experimental results that under the same inlet air conditions more humidityremoval in wheel could be achieved with less supply air volume, and higher COP value withlower water temperature in coolers. The average COP value under the condition with100%fresh-air ratio is higher than another condition. With the seawater temperature decreased, totalhumidity removal in desiccant wheel and the COP value were all increased under conditions withthe same inlet air and supply air volume.From theoretical analysis and experimental studies, it could be proved that marine rotarydesiccant air-conditioning system had a better dehumidification effect and was significant energysaving. The system can take full advantage of ship exhaust heat and abundant seawater availablefor the system. With the fresh-air ratio of process air increased, total humidity removal in wheeland the COP value was increased, which was in accordance with the characteristics of highfresh-air ratio for marine air-conditioning systems.