A strategy to optimize the charge amount of the mixed refrigerant for the Joule–Thomson cooler

•A novel strategy is proposed to optimize the mixed refrigerant charge amount.•The proposed strategy is verified by an experiment with a ternary mixture.•The circulation composition can be adjusted to the approximate optimal value.•A favorable performance of the cooler can be obtained by the proposed strategy.

The performance of the mixed refrigerant (MR) Joule–Thomson cooler is mainly dependent on the MR circulation composition for a given hardware. However, it is difficult to charge the MR to the desired circulation composition, due to the composition shift. In the present study, a novel strategy was proposed to solve this problem. In this strategy, the MR Joule–Thomson cooler is first charged with the initial charge amount, which is obtained by estimating the MR inventory in the cooler using the homogeneous model. Afterwards, the cooler is started and the MR circulation composition is adjusted to the corresponding optimal composition by adding the MR charge amount stepwise. Additionally, this strategy was verified by an experiment with a ternary mixture of methane, ethane and i-butane. The experimental results indicated that the MR circulation composition was able to be adjusted to the corresponding optimal circulation composition approximately within the relative deviation of ±5%.