Simulation Analysis of Ammonia Leakage and Dispersion in a Large-Scale Refrigeration System

The use of ammonia in large-scale refrigeration systems(such as those used for a stadium)requires adequate ammonia leakage prevention mechanisms are put in place.In the present study,numerical simulations have been conducted to study the dispersion law in the ammonia machinery room of the refrigeration system for the 2022 Beijing Winter Olympics.The wind speed,and release location have been varied to investigate their effects on the dispersion profile.Different positions of the leakage points in the ammonia storage tank have been found to lead to different areas affected accordingly.In general,the dangerous region area decreases with an increase in the wind speed.However,when the wind is aligned with the leakage direction,this trend is reverted.The study may offer an effective method to predict the impact of ammonia dispersion and implement the safe operation of such large-scale systems.

The effect of ammonia on soot formation in ethylene diffusion flames

This paper originally investigates the effect of NH_(3) dilution on soot formation when NH_(3) is gradually added into the fuel stream in an ethylene laminar diffusion flame stabilized on a Santoro burner.The variations of flame diameter and two flame heights,i.e.,mixture-strength flame height and visible flame height are carefully documented and analyzed.Moreover,local soot volume fraction(SVF)and soot temperature fields are simultaneously measured by compact-modulated absorption and emission technique,and the corresponding measurement random errors are also provided by the error propagation calculations for the first time.All the reported measurement random errors of SVF and soot temperature fields are estimated within the range of±0.07–±0.08 ppm and±40–±91 K,respectively.As an original database,the concomitantly measured SVF and soot temperature distributions are provided as high-fidelity datasets for refining soot formation model that is overrode by NH_(3).In addition,the flame cross-section average SVF F_(soot)(z)is calculated for every NH_(3) diluted flame,and the relative contributions of NH_(3) dilution and chemical effect are quantitatively assessed in terms of F_(max)-X_(NH_(3))plotting.It is found that when X_(NH_(3))<30%,the chemical effect of ammonia is about twice that of the dilution effect.While X_(NH_(3))>30%,the chemical effect and dilution effect of ammonia are gradually equal.Eventually,through modeling of the soot formation rate V in the flames,the relative contributions of chemical effect,dilution effect and thermal effect of NH_(3)are further novelty discriminated within the X_(NH_(3))from 0 to 46%and it is shown that NH_(3) chemical effect plays the dominate role in soot suppression,then the dilution effect and the thermal one at the least.