Research On The Performance Of Combined Cooling And Power System Driven By Ocean Thermal Energy And Heat Exchanger

The development and utilization of ocean energy and other renewable energy will help protect the ecological environment and prevent climate deterioration.It can be seen that China attaches more and more importance to the development and utilization of ocean energy from the proposal of promoting the large-scale utilization of ocean energy in the Fourteenth Five-Year Plan.The ocean thermal energy has become the most remarkable part of ocean energy due to the advantages of stable,reliability and huge reserve.However,there are plenty of technical problems such as low utilization efficiency,large consumption of seawater and heat exchanger with low heat transfer coefficient,so that the ocean thermal energy has not been used commercially.In view of the above problems,this paper carries out related research,which provides a certain theoretical basis for the development and utilization of ocean thermal energy.In this paper,a novel combined cooling and power system driven by ocean thermal energy is proposed to improve the utilization efficiency of ocean thermal energy and the heat transfer efficiency of the generator,and reduce the consumption of seawater.In order to realize the full use of energy,a part of the working fluid flowing out of the condenser is fed into the refrigeration cycle to produce cooling capacity by the splitter and then enters the compressor,the working fluid from the compressor is mixed with the remaining working fluid in the mixer and then enters the ocean thermal energy conversion cycle to generate electricity.It is found that the maximum primary energy ratio of the system can reach 21.15%,and compared with the basic ocean thermal energy conversion cycle,the consumption of warm seawater and cold seawater is reduced by 36.60% and 28.91%,respectively.When the split ratio is greater than0.06,the working fluid at the inlet of generator reaches the boiling state under the conditions of calculation,thus greatly improving the heat transfer efficiency of the generator.In addition,it is found that these parameters have obvious effects on the coefficient of performance,primary energy saving ratio,primary energy ratio,output power of turbine and cooling capacity of evaporator after detailed analysis of evaporation temperature,condensation temperature,type of working fluid and split ratio.In order to improve the heat utilization efficiency of the system,the heat transfer performance of the heat exchanger which is the key equipment in the system is studied experimentally and numerically in this paper.The influence of groove size,oscillatory fraction and Strouhal number on heat transfer performance of plate heat exchanger with groove channel as the basic unit under pulsatile flow is investigated.The aluminum dust method is adopted to visualize the flow patterns of pulsatile flow in the experiment.Then the heat transfer performance of the groove is further analyzed by FLUENT.The results show that the unsteady flow of fluid is beneficial to the enhancement of heat transfer,and the increase of groove length,oscillatory fraction(P)and Strouhal number(St)can lead to the unsteady flow.The flow and heat transfer under the pulsatile flow can be divided into low Strouhal number range and high Strouhal number range.The increase of Strouhal number can improve the heat transfer in the low Strouhal number range,and the peak of mean local enhancement heat transfer factor is gradually delayed with St during a pulsating period.But an increase in St is harmful to the enhancement of heat transfer in the high Strouhal number range.Moreover,it is found that an optimal St corresponding to the peak value of time-average enhancement heat transfer factor is independent of the oscillatory fraction.When the net Reynolds number and groove length are150 and 5.6 respectively,the transition period is St=0.0417,and the maximum value of time-average enhancement heat transfer factor is 2.14 for P=1/2.