Performance analysis of rotary indirect evaporative air coolers

Abstract

This paper presents the concept of a Rotary Indirect Evaporative Cooler (RIEC) which the operation principle is based on implementation of evaporative cooling in rotary exchanger to increase its cooling effectiveness. The RIEC unit can operate in two modes: standard and regenerative. The mathematical model of RIEC, based on the ε–NTU method, is presented. The operation of RIEC is compared to the traditional Counter-flow Indirect Evaporative Cooler (CIEC) which also operates in two modes: standard and regenerative. Different performance indicators are introduced i.e. Energy Efficiency Ratio (EER), indicators relating the cooling capacity to cooler's length, cooler's inlet cross-section, and to cooler's overall volume. Additional two indicators are introduced to describe RIEC and CIEC operation principles by relating the cooling capacity to the rate of heat or mass transfer occurring in the wetted part of the cooler. The performance of RIEC and CIEC is compared under different climate conditions following Köppen-Geiger climate classification system. It was found that the values of performance indicators calculated for RIEC are higher than for CIEC under various operational parameters and climatic conditions. It was stated that choosing RIEC instead of CIEC allows increasing EER on average by 63% in standard mode and 88% in regenerative mode. It was concluded that RIEC is a competitive solution for cooling purposes due to its lower electricity demand and smaller dimensions.