Experimental Study About Effects Of Different Evaporators On The Organic Rankine Cycle Power System

For the most effective utilization of medium and low temperature energy,based on the law of thermodynamics,experiment about analysis of heat transfer performance,thermal efficiency,exergy,and temperature efficiency on a 500 W ORC system with different evaporators are carried out(respectively referred to plate ORC system and shell and tube ORC system).Optimal operating conditions are determined and some problems are found in the operation.Meanwhile,some solution is put forward.In the experiment,on the condition of different heat source temperatures,thermodynamic parameters of inlet and outlet of the components are recorded and analyzed by different software with varying the working fluid flowrate.No matter the evaporator is plate heat exchanger or shell and tube exchanger,optimal working fluid flowrate,optimal evaporation temperature and pressure with optimal system performance can be obtained.Higher the temperature of heat source is,most optimal system performance is and heavier the working fluid flowrate is.Superheat and amount of steam in the outlet of evaporator are the two main factors that determine system performance.Unstable power generation appears when superheat is low in the outlet of evaporator.However,in the experiment optimal system performance is obtained on the condition of low superheat.Therefore,when plate evaporator is designed in ORC systems,area of plate heat transfer exchanger should be larger than designed.There is no unstable performance in the shell and tube ORC system.The small evaporation in the plate heat exchanger is the main cause of the above problems and some solutions are promoted in this paper.Comparing these two systems,advantages of plate ORC system are that smaller space,lower cost and lower sealing requirement is needed.Meanwhile,heat transfer and pressure drop of plate ORC system performs better than shell and tube ORC system.With heat source temperature at 100 ?,the most optimal overall coefficient of shell and tube heat exchanger is 1977 W/m2·? and the most optimal overall coefficient of plate heat exchanger is 3164.79 W/m2·?,1.5 times of the coefficient of shell and tube heat exchanger.System parameters of shell and tube ORC system including power generation,thermal efficiency and exergy efficiency perform better than plate ORC system.Optimal thermal efficiency and exergy efficiency of the two systems respectively are 5.75 %/43.01 % and 3.64 %/28.92 %.