Experimental Validation of Wet Compression with a Twin Screw Compressor Prototype
V.V. Kothari (TU Delft - Mechanical Engineering)
C. A. Infante Ferreira – Mentor (TU Delft - Engineering Thermodynamics)
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Abstract
Decarbonisation can be done through various routes: reducing the final energy consumption by improving process conditions and efficiency, reusing waste heat and by an outright energy transition to renewable sources. In this study, the focus is on reusing waste heat. Heat pumps have the potential to drastically reduce energy requirements in the industry and in that way reduce emissions (Kiss and Infante Ferreira, 2017). van de Bor et al. (2015) compared different heat pump technologies and for industrial applications where there is a temperature glide of the heat source and/or sink compression-resorption heat pumps (CRHP) utilizing wet compression can achieve a higher coefficient of performance (COP) than alternative technologies. However, an isentropic efficiency of 70% for the compressor was assumed. If this limit is not reached there might be no advantage of wet compression compared to the traditionally used vapour compression heat pump (VCHP) as pointed out by several authors (Itard and Machielsen (1994), and Zaytsev (2003)). This study consists of experimental and modelling aspects. The compressor model is experimentally validated in this thesis. Deep knowledge about relevant topics like wet compression, compressor specifications, thermodynamic and geometrical models is developed before starting off with the experiments. The experiments are carried out for four rotational speeds: 10320 rpm, 12910 rpm, 14205 rpm and 15500 rpm, taking system constraints into account. Two approaches are considered here: the homogeneous approach and the heterogeneous approach. In the homogeneous approach, the concentration of ammonia is constant across the compressor and the process medium is treated as a single entity. In the heterogeneous approach, an assumption is made: only the vapour is compressed whereas the liquid exchanges heat with the vapour leading to partial evaporation. The model developed is updated. The experimental and model results are then validated and conclusions are drawn.