The refrigeration industry is undergoing a structural transition as environmental regulations accelerate the phase-out of high-GWP refrigerants. One concept that has recently re-emerged in engineering discussions is the use of water (R718) as a refrigerant. When operated under deep vacuum conditions, water can function as a sustainable working fluid for cooling systems.
For engineers working in industrial refrigeration systems, the adoption of R718 introduces a new set of technical considerations — particularly for the design of high-efficiency condensers and plate heat exchangers.
Among all refrigerants currently available, water has the most favorable environmental profile. It has zero ozone depletion potential (ODP) and zero global warming potential (GWP), making it completely compliant with long-term climate regulations.
Beyond environmental advantages, water also has excellent thermodynamic characteristics. Its latent heat of vaporization is significantly higher than most synthetic refrigerants, meaning a relatively small mass flow can transport substantial heat energy.
Although the working fluid is different, the thermodynamic cycle of an R718 system remains conceptually similar to conventional vapor-compression refrigeration.
Inside the evaporator, water evaporates under deep vacuum and absorbs heat from the cooling load. The resulting low-pressure vapor must then be compressed — usually by a high-speed centrifugal compressor — to raise its saturation temperature.
The vapor then enters the condenser where heat is rejected to a cooling water loop. After condensation, the liquid water returns to the evaporator and completes the refrigeration cycle.
In compact refrigeration equipment, these condensation processes are often implemented using a copper brazed plate heat exchanger, which provides extremely high heat transfer efficiency in a small footprint.
Unlike conventional refrigeration systems that operate above atmospheric pressure, R718 systems typically run between 20 and 100 mbar absolute pressure.
When plate heat exchangers are used as condensers in R718 systems, they operate under highly asymmetric conditions. The vapor side may be under deep vacuum, while the cooling water loop operates at several bar.
Under these conditions, mechanical stiffness of the plate pack becomes critical. Even small structural deformation can restrict condensation channels, increase pressure drop, and disturb two-phase flow regimes.
For this reason, properly designed gasket plate heat exchangers are often preferred in large industrial installations where structural robustness and maintainability are required.
Additionally, vacuum refrigeration systems are highly sensitive to non-condensable gases. If air enters the system, it tends to accumulate in the condenser and create a diffusion barrier that suppresses heat transfer performance.
Although water refrigeration systems are still emerging, they are increasingly considered for environmentally sensitive applications such as data center cooling, industrial process cooling, and sustainable refrigeration systems.
In particular, high-pressure refrigeration applications such as CO₂ refrigeration systems demonstrate how heat exchanger engineering plays a decisive role in enabling new cooling technologies.
Download the HEXNOVAS engineering brochure for high-pressure refrigeration heat exchanger applications.
Download HEXNOVAS CO₂ High Pressure Brazed Plate Heat Exchanger Guide
