Experimental Study On Variable Load Water Production Characteristics Of Plate-type Seawater Desalination Devic

The traditional plate type seawater desalination device has no regulating mechanism and narrow working range,which is difficult to adapt to the variable load work of Marine diesel engine and can not meet the increasing requirements of fine operation of ships.The key to broaden the operating temperature range is to control the operating parameters of the adjustable jet pump.However,the study of the internal characteristic parameters of plate desalination unit is still very short,and the understanding of the interaction between the parameters of the combined operation between the adjustable jet pump and the desalination unit is very short.Comprehensive experimental testing and theoretical analysis are urgently needed.In this paper,precision instruments are used to measure and explore the influence of operating conditions,such as seawater temperature,seawater flow and heat source hot water temperature,on the water yield and liquid level of concentrated seawater.Combined with the micro-channel boiling heat transfer mechanism,the action principle between water yield change and parameters is deeply analyzed,and the correlation formula of boiling heat transfer criterion of plate evaporator is concluded.Based on the experiment,the concentration factor and the liquid level parameters of thick seawater are introduced to establish the calculation model of variable load regulation of plate desalination device.Through calculation,the adjustment mode of adjustable jet pump under variable load is obtained.Then,the equipment is regulated to meet the ship’s demand for variable load water production,which is helpful to provide theoretical basis and technical support for variable load regulation of plate desalination plant.In this paper,the research progress of Marine desalination plant and the two important parts of plate desalination plant jet pump and plate evaporator are reviewed and discussed in detail.Through detailed calculation,the plate type rising film evaporator is manufactured,the stationary gas-liquid two-stage jet pump is designed and manufactured,and the plate type desalination device experimental platform is built.The experimental system is introduced in detail and the experimental method is expounded.The air tightness test and heat balance test were carried out before the experiment to verify the reliability of the experimental platform.By observing the formation of scale layer inside the plate,the inhomogeneous flow in the evaporator was analyzed,and the minimum concentration factor was obtained by comprehensive analysis.Experiments of water production under different working conditions were carried out.The evaporator was determined to be a micro-channel by calculating the experimental data in the evaporator.Combined with the flow boiling heat transfer theory of micro-channel,the influence trend of different working parameters on the water production was analyzed,and the optimal working parameters were obtained when the water production reached the maximum.The correlation fitting method is discussed.Matlab fitting method based on nonlinear least square method can fit the experimental data of asymmetric plate heat exchanger well.The single-phase convective heat transfer correlation formula and boiling heat transfer correlation formula of plate evaporator are fitted by this method.It is found that Bd number reflecting fluid surface tension and plate spacing can predict the trend of convective heat transfer coefficient with higher accuracy.In this paper,the adjustable jet pump with regulating cone is designed to replace the fixed jet pump,so as to realize the variable load regulation process.The liquid level variable of concentrated seawater is introduced into the equation of jet pump,and the thermodynamic equation and jet pump equation are coupled into the variable load regulation model of plate desalination plant.The results show that the state parameters of the ejecting fluid of the adjustable jet pump can be effectively adjusted by adjusting the cone stroke.The temperature range of the heat source hot water of the desalination device is extended from 66～84℃ of the fixed structure to 29～84℃ of the adjustable structure.Compared with the fixed structure that simply depends on the adjustment of the flow rate,the seawater desalination device of the adjustable structure has higher thermal efficiency.