economizer, vapor injection, location, performance, screw compressor
Twin screw compressors are widely used in many applications. The performance limits of screw compressors are continuously being pushed to meet increased demand for energy efficiency. Several design adjustments can be made to the compressor to create a more efficient unit, such as the proper design of an economizer. The economizer is a port where refrigerant vapor is (re-)injected. General compressor effects of using an economizer are increase in compressor power, increase in discharge mass flow, and reduction of isentropic efficiency. However, the unit experiences an increase in refrigeration capacity and efficiency. The use of economizers for screw compressors is a developing application. This paper examines the addition of an economizer to a water chiller system with the intent of achieving a unit efficiency improvement. The economizer port size and location impacts the compressor performance. For this study, the port size location is varied to understand how it affects the unit performance. A useful procedure is developed to optimize the unit efficiency using internal compressor and system modeling tools is discussed within this paper. The selected port location will be used to create a new screw compressor design that is anticipated to achieve a 2% to 3% improvement in the unit coefficient of performance.