Rotary Heat Exchangers Pty Ltd

Indirect Evaporative Cooling


The following Table indicates the performance of our modular Indirect Evaporative Cooling units which incorporate our highly efficient (up to 90%) RHE together with the 80% efficient evaporative cooler and highly efficient fans using the latest fan technologies.

This Table of indicative performance is based on our high efficiency Series S426 RHE of varying wheel size diameters, equal Fresh and Exhaust air flows and a hot and dry ambient condition of 37C and 30% rh for comparison purposes.

MODEL          RHE Wheel Size         Air Flow l/s     Typical Cooling kW
 IEC 760         RHE 760                     500                              15
 IEC 1000       RHE 1000                   1000                            30
 IEC 1270       RHE 1270                   1500                            40
 IEC 1500       RHE 1500                   2000                            50

CSIRO pioneered R&D in Indirect Evaporative Cooling (IEC) in the late 60's on an international stage as a possible viable option for solar air-conditioning.
The single and double effect indirect evaporative cooling open cycles utilising 100% fresh air were first published by CSIRO Chief Scientist R.V. Dunkle from Melbourne's Mechanical Engineering Division in 1965 and was the subject of R&D until the 90's.

The Melbourne Mylar Rotary Heat Exchanger was the optimum high efficiency heat exchanger developed to be utilised in this IEC cycle and the manufacturing company RHE was formed in 1968. It's director Bill Ellul was one of the CSIRO's engineer/scientist vitally involved in this R&D.

Computer modelling studies conducted by CSIRO showed that indirect evaporative cooling using water as the cooling medium, could be used for or as an aid to air-condition buildings in all the dry and moderate climatic parts of Australia in which by far the majority of  towns and cities are located.

Desiccant dehumidification and solar air-heating is not required when using IEC for the majority of the summer season in these locations.

IEC is simply a compact air handling unit comprising one RHE, one Evaporative Cooler, one air supply fan and one exhaust air fan. For optimum performance it is most important that all these components perform at very high efficiency levels (>80%).

The building exhaust air is blown from the building and evaporatively cooled through an efficient EC before passing through the exhaust side of an efficient RHE.

Fresh air is indirectly evaporatively cooled by blowing it through the fresh air side of the RHE before entering the building. This cools the building indirectly without humidifying it, providing more cooling and better comfort conditions than standard direct evaporative cooling. This process is most effective in dry to moderate climates such as occurs in most Australian cities.

In the more humid and tropical areas such as northern Queensland a system to dehumidify the incoming humid fresh air will be required. This can be accomplished by the adding a dehumidifying desiccant rotary heat exchanger (DRHE) which requires a separate heated air stream to regenerate the desiccant rotor. This heated air can be supplied by solar air heating.

Revised 30 Oct 2014 Copyright © 2014 Bill Ellul. All rights reserved