City Research Online

Abstract

This paper describes an experimental blowdown facility designed to characterise the expansion of supercritical CO2 near the critical point. Specifically, the test rig aims at replicating the expansion process at the leading edge of a CO2 compressor with the goal of studying the role of real-gas effects, and possible condensation. The test rig consists of two pressure vessels (high and low pressure), a reciprocating compressor used for charging, a temperature-controlled water circuit to adjust the temperature of the high-pressure tank and a test section comprised of a convergent-divergent nozzle.

The specification of the pressure vessels and the recharging compressor is described which are selected to allow for reasonable charging and blowdown times. The design of a thermal management system is also described that keeps the conditions within the high-pressure vessel temperature within the desired range, whilst avoiding over pressurisation. The optimisation of the test rig layout is also discussed which includes identifying an economically and technically viable solution for the positioning of pressure relief valves and the ventilation system. Furthermore, the range of anticipated test conditions that can be achieved and the expected expansion process within the nozzle have been explored using transient lumped mass models of pressure vessels that are coupled with a quasi-steady nozzle model to determine the expected conditions within the nozzle. The nozzle model assumes a homogeneous mixture under thermal equilibrium at any point where the working fluid enters the saturation dome.

For the defined test rig specifications (high pressure tank = 0.1 m3; low pressure tank = 0.185 m3; CO2 charge = 100 kg; nozzle throat = 100 mm2) it is predicated that constant inlet pressure conditions can be sustained for between 0.4 and 5.5 seconds for test section inlet conditions ranging between 27 and 45 °C, and 70 and 90 bar.

Publication Type:	Conference or Workshop Item (Paper)
Additional Information:	Copyright © 2024 by ASME. This paper has been originally published by ASME and it's available online at: https://doi.org/10.1115/GT2024-129415.
Publisher Keywords:	supercritical CO 2, waste heat recovery, non-equilibrium effects, real-gas effects, turbomachinery
Subjects:	T Technology > TJ Mechanical engineering and machinery
Departments:	School of Science & Technology School of Science & Technology > Engineering
SWORD Depositor:	Symplectic Administrator

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