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为了达到最佳COP,跨临界二氧化碳两级压缩循环的高压和中间压力需同时进行优化,而优化过程比较复杂。本文提出一种简便的循环分离法,将两级压缩循环分离为两个复叠的单级压缩循环:高压循环为跨临界循环,以中间压力为其蒸发压力;低压循环为亚临界循环,以中间压力为其冷凝压力。先通过高压循环优化高压,再优化两级循环的中间压力。对一种典型的两级循环进行了优化计算,建立了相应的最优高压和最优中间压力的经验关联式,与直接优化的结果相比,预测循环最佳COP的最大值和平均误差分别为-0.85%和-0.15%。对于其他不同类型的跨临界二氧化碳两级压缩循环的优化,使用循环分离法只需再重复中间压力的优化过程。
In order to achieve the best COP, the high pressure and the intermediate pressure of the transcritical carbon dioxide two-stage compression cycle need to be optimized simultaneously, and the optimization process is more complicated. In this paper, a simple method of cycle separation is proposed, which separates the two-stage compression cycle into two cascaded single-stage compression cycles: the high-pressure cycle is a transcritical cycle and the middle pressure is the evaporation pressure; the low-pressure cycle is a subcritical cycle The middle pressure is its condensing pressure. Optimize the high pressure through the high pressure cycle first, and then optimize the intermediate pressure of the two stages. A typical two-stage cycle is optimized and the corresponding empirical correlation of the optimal high pressure and the optimal intermediate pressure is established. Compared with the direct optimization results, the maximum and average error of the optimal COP of the prediction cycle are respectively -0.85% and -0.15%. For other different types of transcritical carbon dioxide two-stage compression cycle optimization, the use of cycle separation method only need to repeat the optimization of the intermediate pressure.