TM52 - Summer (elevated) air speed

[pran]

When carrying out the IES TM52 analysis, we are able to change a parameter named 'summer (elevated) air speed'. I understand from TM52 that this is to take account of air movement within the room, and determines the relative importance of air and radiant temperature in the resultant temperature figure.

I can't find any guidance from IES or in TM52 as to what this figure should be. The default is 0.8m/s, but why? It makes quite a bit of difference to the results if I edit this variable. It would be good to hear that there is some sort of justification behind the 0.8 figure, if not a method for estimating it on individual projects.

[JohnM]

Hi pran,

The VisaPro TM52 user guide may help you out.

Unfortunately i can't help you with the 0.8m/s default value.

John

[ScottIES]

Pran,

did you ever get an answer to your query, having the same problem.

[JohnM]

After doing some digging, I believe the 0.8 m/s may come from the ASHRAE 55 standard, specifically section 5.3.3.2 on Limits to Average Air Speed (Va) without Occupant Control.