Implementation examples

Oxycom uses water, nature’s most powerful refrigerant (R718), to cool air in an environmentally friendly manner. Evaporating 1 m3 of water delivers almost 700 kWh of cooling. As a comparison, the same amount of water is used in a power plant to generate only 50 kWh of electricity, which conventional air conditioning systems can convert in no more than 150 kWh of cooling. Oxycom developed several evaporative cooling technologies and technology combinations, each with its own applicability region:

  • Standalone Oxyvap®: suitable for any outdoor temperature and outdoor absolute humidity up to 12 g/kg (0.012 lb/lb).
  • Two-stage Oxyvap®: suitable for any outdoor temperature and outdoor absolute humidity up to 16 g/kg (0.016 lb/lb).
  • Standalone Oxycell®: suitable for any outdoor temperature and outdoor absolute humidity up to 16 g/kg (0.016 lb/lb).
  • Oxycell®-based hybrid cooling: suitable for any outdoor temperature and humidity.
  • Oxyvap®-based condenser pre-cooling: suitable for any outdoor temperature and humidity.

Standalone Oxyvap®

The Oxyvap® is a direct evaporative cooling pad that adiabatically cools air towards its wet bulb temperature, typically achieving a 90% saturation efficiency. Its modular design enables it to be used for any airflow, while the frontal air velocity is typically 1−3 m/s (197−591 fpm).

Two-stage Oxyvap®

The two-stage Oxyvap® is an Oxyvap®-based cooling configuration that uses an additional air-to-water heat exchanger to enhance its performance. Chilled water from the Oxyvap® is fed to the heat exchanger to pre-cool outdoor air before it enters the Oxyvap® pad, that is then fed with water returning from the heat exchanger.

Since it is a closed system, the cooling process as a whole will be adiabatic, but the combination of the pre-cooling process and the recirculation of water between the components will lead to a vertical temperature gradient in the air leaving the Oxyvap® pad.

The upper half of the supply air will have a higher enthalpy than the intake air, whereas the lower half will have a lower enthalpy. When the upper half of the air is discarded, the lower half can be used as supply air, reaching an average temperature below the initial wet bulb temperature, while less moisture is added compared to traditional adiabatic cooling.

Standalone Oxycell®

The Oxycell® is a counter-flow indirect evaporative heat exchanger in which air in the secondary channel (work air) is evaporatively cooled, hereby extracting heat from air in the primary channel (process air). This principle is referred to as Indirect Evaporative Cooling (IEC).

Dew Point Cooling (DPC) is a special application of the Oxycell® heat exchanger, in which part of the cooled primary air (typically 35−40%) is branched off and used as secondary inlet air, where it is cooled evaporatively, hereby extracting heat from the primary air stream. Ideally, primary air can be cooled down to its dew point temperature, while maintaining a constant absolute humidity.

Whether DPC or IEC is the preferred cooling method depends on various parameters, such as the outdoor air conditions, heat load and fan configuration.

Oxycell®-based hybrid cooling

The hybrid configuration is based on the Oxycell® IEC. In practice, the Oxycell® IEC cools outdoor air (flowing through the primary channel) down to about a degree above the physical limit, i.e. the wet bulb temperature of the secondary inlet air, while maintaining a constant absolute humidity.

When humid outdoor air conditions do not allow for sufficient cooling, the evaporator coil from a conventional vapor compression air conditioning system may be used to cool and dehumidify pre-cooled air from the Oxycell® to the desired supply air conditions. The condenser coil is placed downstream of the secondary (wet) channel of the Oxycell®. Generally, this air is cooler than the outdoor air, leading to an increase in compressor efficiency.

Annual savings are typically 50% compared to standalone conventional air conditioning systems.

Oxyvap®-based condenser pre-cooling

In conventional air conditioning technology, a compressor is used to compress the gaseous coolant before it loses its heat by condensation in the condenser coil.

When using the Oxyvap® to pre-cool the air that is supplied to the condenser coil, the coolant is able to condense at a lower temperature, hereby decreasing the work that has to be done by the compressor and consequently increasing its efficiency.