Theoretical analysis for heat exchange performance of transcritical nitrogen evaporator used for liquid air energy storage

Qinghua Yu, Wenji Song, Bushra Al-Duri, Yan Zhang, Danmei Xie, Yulong Ding, Yongliang Li

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)
145 Downloads (Pure)

Abstract

In view of violent changes of thermo-physical properties, the segmental design method is adopted to explore the heat exchange performances of the transcritical nitrogen (T-N2) evaporator used for liquid air energy storage, in which cold N2 is heated up successively by hot propane and methanol in two wide temperature sections. The local heat capacity rate ratio between cold and hot fluids has crucial effects on the local heat exchange performance of evaporator, such as local effectiveness, local entransy dissipation, and local required heat conductance or local heat transfer rate. They have extremums near the positions where the local heat capacity rate ratio equals one, but their optimal values need to be determined by combining the changing trend of the local heat capacity rate ratio. The total heat exchange performance of evaporator is evaluated using total entransy dissipation and total exergy efficiency. When the heat load is fixed, the total performance is improved with the decrease in the mass flow rate of methanol, but at the expense of the required total heat conductance; The total performance can be optimized by precisely tailoring the heat load ratios between the two temperature sections. When the heat conductance is given, the optimum total performance can be obtained by adjusting the mass flow rate of hot fluids at a fixed heat conductance ratio; Increasing the heat conductance ratio of the low temperature section can further elevate the optimum total performance whereas the affordable heat load or the outlet temperature of N2 is notably decreased. Increasing N2 pressure elevates the total performance of evaporator but diminishes the extractable cold amount from the liquid N2 in the same temperature rise. This work is beneficial for selection of key parameters to achieve optimal operation of the T-N2 evaporator.

Original languageEnglish
Pages (from-to)844-857
Number of pages14
JournalApplied Thermal Engineering
Volume141
Early online date8 Jun 2018
DOIs
Publication statusPublished - 1 Aug 2018

Keywords

  • Energy storage
  • Entransy dissipation
  • Exergy efficiency
  • Heat exchanger
  • Supercritical nitrogen

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Industrial and Manufacturing Engineering

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