DOAS with indirect evaporative precooling of supply air using heat exchangers with enhanced flow passages is presented. Benefits of patented primary and secondary corrugations of the flow passages of the air to air heat recovery heat exchanger are discussed. Compact heat exchangers with high effectiveness and low pressure drop are presented with case studies depicting the utility of such heat exchangers in DOASs. Precooling outside fresh air, close to its wet bulb temperature, using treated sewage water or saline water in these counter flow heat exchangers is presented. Good Indoor Air Quality (IAQ) can be affordably maintained using waste water.

The paper includes case studies indicating the thermal performance and potential savings with such DOAS in Mumbai and five Middle East cities. Simulation results of achievable effectiveness for this system in different processes and conditions are presented. Important factors like the energy savings, amount of CO₂ emission reduction and payback are also listed. Typical payback is in range of 0.5 to 1 year. Approach to WBT will be 2 to 5°C depending on operating conditions.