Unsteady Numerical Simulation And Experimental Study For Rossini Gas Calorimeter

Rossini-type gas calorimeter is the gas calorific value determination device which has the highest accuracy.In order to improve the level of its uncertainty,an approach of combining numerical simulation and experimental testing for optimizing the calorimeter is carried out on preliminary study in this paper.Firstly,in order to optimize its temperature field uniformity to improve its level of uncertainty,the 3D-unsteady numerical simulation of Rossini-type gas calorimeter is carried out by MRF model and standard k-ε model.The effects of the stirrer rotational speed and the burner height on the unsteady temperature field and velocity field in the calorimetric vessel are calculated,especially the influence on the heat transfer between combustion chamber and heat transfer medium and the influence on the thermal homogeneity of heat transfer medium,as well as to determine the best measurement location of temperature sensor.The results indicate that rotational speed of 420 rpm can be regarded as the optimal rotational speed.Reduction of the height of the combustion chamber can improve the temperature homogeneity of the heat transfer medium.The optimum position of the temperature sensor is on the equidistant line of the combustion chamber symmetry axis and the flow cylinder symmetry axis,and it is 25 mm from the bottom of calorimetric vessel.Secondly,this paper describes the test system of the heat capacity of the calorimeter determined by the electrical calibration.The platinum resistance thermometer is calibrated too,so that each one has its own quadratic function expressing the relationship between resistance and temperature.Once more,this paper presents the nine repeatability measurement results obtained for heat capacity of the calorimeter,and the heat capacity of the calorimeter obtained when the measurements were averaged is 18958 J/K.The extended uncertainty of the measurements is 466 J/K(k=2).Finally,the experimental study on the influence of the stirrer rotational speed on the calorific value measurement of the gas calorimeter is carried out.The experimental results are consistent with the numerical simulation results.With the increase of the rotational speed of the stirrer,the slope of heat transfer medium’s temperature curve increases,which is validated by the experimental results and the numerical simulation results.