Online educational resource on achieving indoor environmental quality with radiant based HVAC systems
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Effects of tube depth and layouts on radiant systems using finite-element analysis (FEA)
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Radiant cooling and heating systems are on-site fabricated heat exchanger where tube depth, layouts and spacing have an effect on back losses and thermal efficacy of the surface. Thermal efficacy describes the quality of the surface temperature or how much the temperature changes across the surface between tubes as a result of changing the depth and spacing. For high quality floors such as bathrooms, kitchens, operating rooms, child day care centers or any floor where it is desirable to have consistent surface temperatures, finite-element analysis (FEA) can predict the best combination of tube depth, spacing and flooring to optimize the design for energy and indoor environmental quality. Above we have modeled effects of tube depth in a sequence of slides and have overlaid some guidelines so you can better see the results. If you have any questions on this or other items related to energy and indoor environmental quality please post your question at our linked-in discussion forum.

Note: You can see the lower the tubes are in the slab, the better the efficacy but the greater the back losses; likewise the closer the tubes to the top the lower the back losses but the poorer the surface efficacy. There are ideal depths for each combination of slab and floor covering, tube spacing and layouts.

Conditioned hollow core floors
Note: air space has been assigned an "effective R-value" to handle the radiant transfer within the core. In practice the airspace should be modeled differently but for our purpose of understanding the conductive transfer in the concrete mass and most importantly the surface efficacy this approach is accurate enough.

Embedded tubes in topping on insulation on hollow core Embedded tubes in topping on hollow core Embedded tubes in hollow core

Conditioned metal deck
Note: Here we are showing the pipes running parallel with the ribs, supported by a layer of WWM (not shown). The layer of WWM would have some effect on the model as would running the pipes perpendicular to the ribs.

The metal deck (Q-deck) system is supported with steel trusses and provides for fast, light weight, fireproof construction in relative terms to other construction techniques. It as well as the hollow core, formed in place and slab on grade also make for an ideal radiant cooling and heating system.


Viewers of this presentations all visted: Scanning electron micrograph, Windows for cold climates, Walls for cold climates, Mean radiant temperature, housing performance categories, and embedded piping.

Keywords: Finite Element Analysis, (FEA), radiant, tube, depth, effects, back loss, fluid temperature, tube patterns

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