Closed Loop Organic Wind Tunnel (CLOWT): Design, Components and Control System

Abstract Organic Rankine Cycle (ORC) systems offer a suitable technique to achieve reduced energy consumption. However, experimental work is largely lacking, and there is an overweight in theoretical work. For this reason, the computation of dense gas flows still represents a major difficulty in ORC development, and there is a need for validation studies based on experimental data, which is currently hardly available. The Closed Loop Organic Wind Tunnel (CLOWT), is a facility to fill this gap. In the first part of this contribution, the design of the CLOWT is presented. A close look will be taken at the main components, such as compressor (especially shaft sealing) and chiller. Furthermore, typical wind tunnel components, such as diffuser, settling chamber, and nozzle, are briefly discussed. Based on the test rig design, the second part shows the basic operating principle of this closed gas cycle, focusing on an exemplary thermodynamic cycle at maximum compressor power. The third part deals with the control system of the CLOWT. For a closed wind tunnel, the setting of the operation points for testing requires special attention, and some similarity to closed cycle gas turbine systems exists. However, in case of a closed wind tunnel, inventory backward control approach is difficult to realize directly. To overcome this problem, an inventory forward control approach is designed for the CLOWT. The findings presented in this part are being used to build up a distributed control system.