Study On Seepage And Heat Transfer Of Multi-well Infiltration Intake System For Seawater Source Heat Pump

The ocean covers more than 71%of the earth's surface.It is a massive source of potential renewable energy and is a suitable heat source and sink for water-source heat pump systems.Seawater Source Heat Pump(SWHP)systems require an auxiliary heat source in cold climate area with extreme weather conditions.The Beach Well Infiltration intake System(BWIS)provides an integrated renewable energy system that uses seawater and ground thermal energy.FLUENT is commonly used to establish and simulate seepage and heat transfer models for BWIS systems.However,numerical simulation time is lengthy for studies of large-scale regions.Also,under the numerical model,it is difficult to determine the relationships among the numerous influencing factors for multi-well system.So,it is necessary to establish a fast-solving model and optimization method,and it is significance to study seepage and heat transfer characteristics of BWIS systems for scientific application.This study first conducts a field test and analysis to compare BWIS performance and the direct intake system for SWHP systems at the Liaodong Peninsula,China.The average sea water temperature for the direct intake system was 5.83 ? and for the beach well infiltration intake system was 12.85 ?.The unit COPs were 2.99 and 4.66,respectively.The test results show that the beach well infiltration intake method improves the stability,reliability,and energy efficiency of the SWHP system in cold climate area and that the intake seawater temperature is a critical factor in SWHP system performance.Secondly,seepage and heat transfer models were established for scientific applications of BWIS.The reflection method and superposition principle were used to analyze solutions for the seepage model.This method was faster at problem-solving than the numerical solution for studies of multi-well systems in large-scale region.The method explicitly analyzed the qualitative and quantitative relationships among the influencing factors of the system.In the heat transfer model,the Peclet number was four orders of magnitude larger in the mainstream area,which shows that the advection term dominates heat transfer and that the conduction term can be ignored in a BWIS heat transfer model for SWHP systems.Then,a software simulation of BWIS seepage and heat transfer was developed based on the MATLAB platform.This study then designed and established a BWIS experimental system for solving the regional limitations of the experimental results in practical engineering.Experimental data validated the above model.Similitude-criterion numbers are found by the similarity theory analysis.Experiments were conducted under the difference schemes,and a similitude-criterion formula was then proposed.Excess temperature,(?),increased alongside a decrease in the Fourier number,FO,Flow number,D,and Location number,R.The degree of influence on the excess temperature,(?),from greatest to smallest was the Fourier number,FO,Location number,R,and Flow number,D.Finally,a step enumeration method was presented based on the above BWIS model aiming at the problem of the immense optimizing data.This paper proposes a project(approximately 37,000 m2)as an example.Under this example,optimal results were:site width of 750 m,site length of 500 m,one row of beach wells,three columns of beach wells,permeability of 0.0007 m/s,and specific heat capacity of 1260 J/(kg·K)for life-cycle costs.It was found that the step enumeration method has a higher level of precision and better analyticity than the orthogonal method,and there is also an improvement in optimization speed than enumeration method.As such,this method is useful for optimizing BWIS,and the corresponding optimization results can scientifically guide BWIS design.