Hochschule Bremen - University of Applied Sciences

Hochschule Bremen

Lubrication-Installation of Screw Engine applied in an Organic Rankine Cycle

Begutachtete Publikation

Natur und Technik

Julius Robert Mayer - Institut für Energietechnik

Smolen, Slawomir, Prof. Dr.-Ing.
Eicke, Albrecht, Dipl.-Ing.


Autor_innen, Jahr, Titel
Slawomir Smolen
3rd International Conference:
“Low Temperature and Waste Heat Use in Communal and Industrial Energy Supply Systems, Theory and Practice”
Proceedings, October, 25th-26th, 2012, page: 165-169

Weitere Informationen
Proceedings, University of Applied Sciences Bremen

Proceedings LTWHU 2012
Proceedings Low Temperature and Waste Heat Use 2012
Lubrication-installation of screw engine
applied in an Organic Rankine Cycle
Slawomir Smolen, Albrecht Eicke
University of Applied Sciences Bremen
Faculty Nature & Engineering, Department of Mechanical Engineering
Neustadtswall 30
28199 Bremen, Germany

1 Introduction

A Rankine cycle using organic fluids as working medium, called organic Rankine cycle (ORC), is potentially capable of recovering low temperature heat sources - it means first of all waste heat - from different industrial and communal processes. The theoretical efficiency of the ORC-Cycle primarily depends on the temperature difference between the heat source and the natural environment (cooling medium). The low efficiency (due to the low temperature of the heat source) requires increased power plant equipment size (turbine, condenser, pump and boiler) that can become cost-prohibitive. Another aspect is the optimisation of the subprocesses, especially expansion in the turbine or other devices, which impacts the total efficiency of the real plant with its energy losses caused by deviations from the theoretical conditions. One of the technical possibilities is using a screw engine as effective expansion device. The principle of a screw engine has been used for the first time as compressor and can be adopted and used in reverse (expansion). This rearrangement requries many modifications and changes of the installation, in order to use the general priciple effectively.
This paper presents some practical aspects of using screw engines as expansion devices, especially a novel lubrication installation addopted from a compressor and modified for the requirenments of expansion machine.

2 Two-Stage ORC-Concept for waste heat recovery

A novel concept for optimising CHP-units with combustion engines (especially biogas plants) by converting the waste heat into electricity in an ORC process at medium or low temperature was developed and investigated theoretically within a former research work published in [5].
The concept comprises two heat input stages and two expansion stages. The two temperature levels of heat input correspond to the heat transfer temperatures and ratios in the exhaust gas heat exchanger of a combustion engine – specifically a gas motor in a biogas plant, and in the cooling system of the engine. High-pressure expansion is carried out in a micro-turbine, and the residual expansion is coupled to the expansion of the working fluid from the low-temperature heat input in a screw engine. Although this complicates the system as a whole, it permits better operational exploitation of the options provided by the two expansion devices. The general overall concept for the ORC system is shown in Fig.1.
Diagram of a Two-Stage ORC Process
Fig.1: Overall concept for a two-stage ORC-System



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