The calculation of Joule Thomson coefficient of supercritical water jet flow and the analysis oncooling effect in the process of throttling

It is a process of throttling flow when high-temperature fluid flows through nozzles.It can change the internal temperature of fluid, and consequently impact the impact force and thermal cracking effect of high-temperature jet flow.In this paper, the formula for calculating Joule Thomson coefficient during the running of jet flow through the nozzle was deduced by applying the definition formulas of physical property equation and Joule Thomson coefficient of supercritical water.Then, a program was prepared for iterationcalculation to figure out the distribution characteristics and change laws of Joule Thomson coefficient for different parameters.Finally, Joule Thomson coefficient calculation formula was adopted to calculate the change laws of temperature drop corresponding to different parameters in the process of nozzle throttling.It is indicated that Joule Thomson coefficient is positive under the condition of 25 to 65 MPa and 650 to 1 000 K.As the temperature inside the reaction chamber increases, Joule Thomson coefficient increases first and then decreases.And its maximum value is 4.92 in the conditions described in this paper.As the pressure inside the reaction chamber increases, Joule Thomson coefficient decreases and reaches the minimum 0.22, under the condition of 65 MPa and 650 K.Maximum Joule Thomson effect occurs at superheated steam zones, and deviates from the boundary line with the increasing of temperature.Temperature and pressure drops shall not be neglected during the jetting of jet flow.And its maximum could reach 73.5 K in the conditions described in this paper.Therefore, it is necessary to set rationally the temperature and pressure inside the reaction chamber so as to decrease the temperature loss of high-temperature jet flow when it runs through the nozzle.