Design And Research On Desalination Application Of Solar Heat Concentrating Steam Generation System

In order to avoid the use of complex optical concentrator,this paper design a solar heat concentrating steam generation system.Solar radiation is collected by using a large heat collecting plate,and is converged to the metal steam evaporating pipe with high efficient heat transfer.By establishing the heat and mass transfer mathematical model of the device,the temperature and the associated steam generating rate in the steam generation tube under different solar irradiance,heat collecting area,heat concentration ratio and heat loss are also achieved.With the optimizing of the structure to reduce the heat loss,the steam generation under solar medium temperature thermal concentration is realized.The main research work includes the following aspects:(1)The theory of the non-condensing solar heat concentrating steam generation were analyzed.And The energy input,energy transport structure and heat dissipation loss of solar heat concentrating medium temperature steam generation are studied.The effect of the collector area on the heat accumulation temperature is discussed.The correlation between the solar radiation,the heat collecting area,the heat concentrating ratio,the heat transfer structure,the heat loss and the heat accumulation temperature are revealed.If the thermal conductivity of the bottom and surrounding insulation material is 0.044W/(m·K)with using double glazing cover,the heat transfer coefficient is about 4W/(m~2·K),theoretical analysis showsthat when the effective collector area A_C is 7.6m~2 and the solar irradiance is higher than600W/m~2,the heat loss is lower than the solar radiation energy,and the obtained useful energy can output steam stably at three temperatures of 100?,110?and120?.(2)The system of solar heat concentrating medium temperature steam generation is built,and the operation and debugging of the system have been completed.temperature variation of each component in the solar heat concentrating device under different solar radiation were studied,variation of steam production with time and solar irradiance within a day were analyzed.The experimental results show the average temperature of the heat collecting plate,metal steam evaporating pipe and steam exhaust pipe are consistent with the changing trend of solar radiation.The temperature of the heat collecting plate is greatly affected by the solar radiation,and the metal steam evaporating pipe is smaller.In typical weather(cloudy or sunny days),the steam output of the solar heat concentrating device starts at 10o'clock.And after 15 o'clock,the solar heat concentrating device no longer generates steam.The difference is that the device can produce steam at a faster rate in typical sunny.(3)The influence of heat collecting plate temperature on daily steam production was analyzed.The results show that the steam production increased with the increase of the surface temperature of the heat collecting plate after 10 o'clock.Due to the influence of the weather,after 15:00,the temperature of the heat collecting plate is lower,the steam is no longer output.The accumulative steam time of the day is about 5h.In cloudy weather,the average temperature of the heat collecting plate is118?,and the daily steam production is about 4.415 kg.In sunny days,the average temperature of the heat collecting plate is 134?,and the daily steam production is about 6.174 kg.(4)The change of steam production per unit time of solar heat concentrating medium temperature steam generation system was studied.In typical weather,the steam production per unit time is almost zero at 9:00 and 16:00.Because of the two time periods at 8:00-9:00 and 15:00-16:00,the solar irradiance is smaller.So there is no steam output.In typical cloudy weather,the device adds water once at 12:00,and the rate of steam production drops rapidly.In typical sunny weather,the whole device needs to add water 3 times,about once every hour.(5)Research on desalination performance of solar heat concentrating medium temperature steam generation system.The experimental results show that the whole day water production of the system is 6.297 kg,the salinity is 1.65%and TDS is 660mg/L when the device is in the state of full-pressure.When the device is in pressure relief state,the whole day water production is 1.89 7kg,the salinity is 0.05%and TDS is 20 mg/L.If the system is regulated in a timely manner,the whole day water production is 3.026 kg,the salinity is 0.95%and TDS is 380 mg/L.(6)The change of water production rate of the desalination system in typical sunny weather is analyzed.In typical sunny days,the desalination system does not need to add salt water when the pressure is released.The water production rate of the system first increases and then decreases with time,and the water production rate of the system is the fastest at around 13:00.When the desalination system is regulated in a timely manner,it needs to be added salt water once.At around 13:00,the system also achieved the fastest rate of water production.However,the rate of water production appears a rebound because of adding salt water.When the desalination system is in full-pressure state,it needs to be added salt water three times.System water production rate reached the fastest time an hour earlier,near 12:00 in the fastest water production rate.