Heat recovery unit

with indirect adiabatic cooling

Air flow rate: 3500÷20000 m³/h


Product benefits

  • Heat recovery system with maximised summer efficiency
  • Can be used in combination with every handling module in the range
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Heat recovery with indirect adiabatic cooling.

Principle of operation

To improve the performance of sensitive heat exchangers in summer mode, combine them to an indirect adiabatic cooling system (IAC).
Rhoss has developed a state of the art recovery system that integrates indirect adiabatic cooling with high efficiency static heat recovery. Through this system, the exhaust air can be cooled in a sensitive way in one or more stages of humidification by obtaining a lower delivery air temperature than the ambient temperature without using any cold coils, thereby continuing to recover heat also if the outdoor air temperature is lower than the room temperature.
This cooling method is extremely cheap and sustainable. It also allows you to reduce the size of the cooling unit or even remove it.

Summer mode and intermediate warm season
During the hot season, the system activates the indirect adiabatic humidifier automatically, which cools the expulsion air down before entering the heat recovery unit.
This way, the temperature difference between expulsion air and outdoor air is maximised as is system efficiency. If intervention is required, the regulator activates the cooling coil and possibly the reheating one to obtain the exact temperature and humidity conditions required.

Winter mode and intermediate cold seasons
In winter the system maintains all the energy benefits arising from free-cooling and/or recovery of sensitive heat, thereby guaranteeing maximum energy savings in any environmental condition.
According to an enthalpic comparison between outdoor air and room air, and according to the required percentage of fresh air, the system regulation selects the most economic operating mode between total free-cooling, partial free-cooling, and partial and total heat recovery.

Parameters that influence system operation
The parameters that most affect the process are room temperature and humidity and heat recovery efficiency.
Outdoor air is also important, because the lower it is, the more the room can be maintained at a lower relative humidity, thereby increasing system efficiency. It is important for energy saving assessments to be made considering the real values of system operation.

Main features

The crossed flow recovery unit features aluminium fins protected against corrosion by a special non-toxic hydrophilic epoxy paint, which guarantees on the one hand a high resistance to corrosion of the different types of water used to supply the humidification system and on the other allows the formation of a wet micro-layer on the exchange fins increasing the useful effect of the system.
The water is micro-sprayed by an atomiser with a high-pressure pump that creates an ultra-fine mist by cooling the air both by direct evaporative effect and by water retention on the surface of the heat recovery unit, thus providing a greater cooling capacity and reducing water consumption. The ramps of nozzles with head and baffle made of stainless steel come complete with anti-spill valve and are completely removable.
Greater evaporation efficiency and speed
Greater exchange efficiency thanks to the damp micro-layer on the heat recovery unit
Unvaried pressure drops on the air side
Lower air consumption
No contamination

Additional sections

The RIGENERA recovery unit section can be combined with the air handling sections to complete the required system functions:
• Additional cold water coil.
• Additional hot water coil.
• Steam humidifier or with evaporating pack.
• Silencers.
• G4 pre-filters.

Full Safety O3 Option

The IAC recovery system is provided with an ozone self-cleaning device to keep efficiency unaltered, prevent mould, algae and bacteria from forming and guarantee the microbiological control of the entire system.

Full Control Option
The Full Control option allows you to obtain maximum energy saving compatible with the desired heat and hygrometric comfort: no waste whatsoever.

Control and regulation functions
Besides the traditional regulation functions for full air system treatments, the ADIABATICA range comes complete with the following specific functions:
• heat recovery management with indirect adiabatic cooling integrated in Maximum Economy mode with:
automatic enthalpy free-cooling management, indirect adiabatic cooling activation for enthalpic comparison and recirculation dampers and outdoor air management via air quality probe.
• Increased management during system start up phase for quick and inexpensive implementation.
• Delivery temperature compensation in relation to the outdoor temperature.
• Fan operation with constant delivery flow, based on how dirty the filters are.
• Management of the heat transfer fluids according to time schedule with 3- or 2-way valves depending on the system.
• Weekly time bands control.
• Signal or alarm management (also on request).
• Integrated system management of ozone sanitation of air and humidification water for microbiological control.
• BMS interface with Modbus or Lon protocol.
• Supervision via Web-Ethernet port on TCP/IP technology.
• GSM modem kit for remote monitoring via SMS with alarm control.

Nominal air flow m³/h
Available delivery static pressure Pa
Available return static pressure Pa
Summer mode
Recovery cooling capacity kW
Additional cold water coil cooling capacity kW
Summer energy savings %
Reheating coil heating capacity kW
Winter mode
Recovery heating capacity kW
Hot water coil heating capacity kW
Winter energy savings %
Total consumed power of delivery and return fans kW
Length mm
Height mm
Depth mm
920 2080 2920 4300 6060
3.5 7 10 15 20
200 200 200 200 200
150 150 150 150 150
12,3 24,5 35,4 52,6 70,6
27,1 54,2 77,5 116,2 155,0
31% 31% 31% 31% 31%
7 14 20 30 40
21,5 43,0 61,0 91,6 122,0
20,4 41,0 58,0 87,4 116,0
51% 51% 51% 51% 51%
2,3 4,5 6,2 9,7 12,5
920 2080 2920 4300 6060
4.075 4.45 4.825 5.2 5.385
1.87 2 2.1 2.7 2.9
1.35 1.6 2 2.5 2.88

Data at the following conditions:

Outdoor air T/RH 32°C/50%; return air T/RH 26°C/50%.

Water T in out =7/12°C; delivery air T = 13°C.

Water T in out =40/35°C; delivery air T = 19°C.

Outdoor air T/RH -5°C/80%; return air T/RH 22°C/50%.

Water T in out =40/35°C; delivery air T = 32°C.

Maximum depth (including the technical compartment to house the control).