Application of Scroll Expander in Cryogenic Process of Hydrogen Liquefaction

Abstract

Hydrogen is a clean energy carrier and can be a potential alternative of fossil fuels. Its use in energy systems needs efficient storage for on-demand distribution to the facilities. However, storage of hydrogen as a gas needs large storage tank which is not feasible due to a high volume to energy ratio. By liquefying hydrogen this barrier of storing can be solved. In this paper, a modification to Claude liquefaction process of hydrogen is proposed for increased efficiency. More specifically, the Joule–Thompson valve of the typical Claude cycle is replaced with an expander for work recovery. In addition, the integration of an additional expander is found suitable to recover more work from the expanding hydrogen. However, consideration was made in selecting expanders as it involves two-phase flow. Scroll expander being capable of operating with two-phase fluid is suitable to use in this cycle for cryogenic hydrogen liquefaction. This paper presents an analytical feasibility study of the scroll expanders integration with a modified Claude cycle. The result shows that a 2–3 % work recovery is possible with the integration of the expanders which justifies further study on the process with more detailed analysis and optimization methods. The expansion power that is recoverable is of the order of 1–5 kW. The paper concludes that the scroll expander can be used for work recovery in other cryogenic applications which becomes increasingly more important.

Nomenclature

C _p :

Specific heat, kJ/kg K

k :

Adiabatic exponent

h :

Specific enthalpy

$\dot{m}$ :

Mass flow rate, kg/s

P :

Pressure, bar

PR :

Pressure ratio

T :

Temperature, K

w :

Specific work, kJ/kg

$\dot{W}$ :

Work rate, W

η :

Efficiency

e:

Expander

en:

Energetic

ex:

Exergetic