RADIANT COOLING EXPLAINED

Pivot Building Solutions pte Ltd

Improvement of thermal comfort in tropical climates by using high temperature cooling.

Our engineer is explaining you the concept and addressing the myths & facts.

Radiant cooling in tropical climates

Hydronic based radiant cooling refers to temperature-controlled surfaces embedded in building components that cool a space by removing sensible heat from its surroundings via thermal radiation and convection. Heat will flow from objects, occupants, equipment’s and lights to a cooled surface as long as their temperatures are warmer and within the line of sight of the cooled surface. A radiant ceiling cooling system has high cooling capacity since it triggers additional cooling by natural convection. A floor cooling system, further referred to as chilled slab, removes sensible heat almost only via thermal radiation and supports air stratification in spaces with high floor to ceiling height. Chilled slabs are most effective at removing direct solar heat gain on the floor surface before it causes an increase of the space temperature. 

Radiant cooling systems do not replace mechanical ventilation systems. The hygienic fresh air ventilation rate according to code and the internal latent loads are recommended to be addressed with a heat recovery ventilation unit with dehumidification function.

By definition, the design approach of a hydronic based radiant cooling systems in parallel with heat recovery ventilation is know as sensible and latent load decoupling.       

Why using radiant cooling systems?

Conventional cooling systems removing space sensible and latent loads entirely via convection. A typical convective system design in Southeast Asia uses approximately 80% of the total supply air flow rate to remove internal sensible loads and 20% for the minimum hygienic ventilation rate. Internal latent load removal is a by product of the design and is never specifically addressed.

Comparing water and air as a thermal transport media to remove cooling loads of a space, the operation cost of a hydronic circulation pump is much lower than a fan. This saves approximately 20-40% cost in a building alone.   

Using a dedicated chiller with smart hydronic distribution network for the radiant system further contribute to 5-15% energy savings. 

Typically, FCU or VAV design are estimated to over cool the space by 30% in 9 out of 10 projects built. This mainly occurs due to scale-able design approaches, high safety factors in cooling load calculations as well as maintaining positive pressure of the space by not applying exhaust air systems with heat recovery ventilation. Looking at individual project design and the right application will enable even more energy savings.

As a conclusion, removing as much fan power required for sensible cooling and replacing it with radiant cooling systems will reduce your electricity bill.

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