Re: Ceiling mass air heater options

Hi Nick

On 29 Nov 2003 09:06:28 -0500,
[EMAIL PROTECTED] wrote:

>Would an unstratified mass (eg a poly film duct containing 1" of water over
>a shiny ceiling, with insulation above that) be warmer with David Delaney's
>flow separator 

See "Solar air heater with flow organizer baffle
array for right-angle crossing of hot and cold air
sheets",
<http://geocities.com/davidmdelaney/flow-organiser/flow-organiser.html>

>or 70 F house return air filling a sunspace/air heater?
>
>Consider 2 steady-state 8' R10 cubes with 64 ft^2 of R2 glazing with 80%
>solar transmission, after a long string of 30 F average January days in
>Phila, with 1000 Btu/ft^2 of sun on a south wall...
>
>1.  --------------
>   |fs|    Tc     |          Cube 1 has a flow separator and a transpired
>   | .|           | R10      mesh collector. We might assume the air hear the 
>   | .|           |          glazing is about the same as the ceiling temp Tc. 
>S  | .|   70 F    | 30 F     This sunspace might be uncomfortably hot, but the
>   | .|           |          amount of airflow is not limited by the cube temp.
>   | .|           |          How does the ceiling keep the cube 70 F? 
>   | .|           |        
>    --------------   
 
I don't understand why Cube 1 is worth analysing.
If I understand your text and drawing, the flow
separator (I prefer "flow organiser", hmmm...
perhaps "flow intersector" would be even better)
can have no useful effect because there are not
two moving sheets of air of different temperatures
that need the flow organiser in order to cross
through each other.

David Delaney

>
>2.  --------------
>   | .     Tc     |          Cube 2 has a ventilation slot at the top and 
>   | .|           | R10      a transpired mesh collector and a potentially-
>   | .|           |          unreliable motorized damper at the bottom which
>S  | .|   70 F    | 30 F     is controlled by a thermostat that keeps the 
>   | .|           |          cube air 70 F during the day. We might assume
>   | .|           |          the air near the glazing is about 70 F. We might
>   | .d           |          need another layer of glazing south of the mesh
>    --------------           to ensure this. The ceiling might keep the cube
>                             70 F with a thermostat and a slow ceiling fan.
>
>In each case, the glazing transmits 0.8x1000x64tft^2 = 51.2K Btu/day of sun. 
>
>In case 1,
>
>   51.2K = 6h(Tc-30)64ft^2/R2+18h(70-30)64ft^2/R12   [south wall]
>         +24h(Tc-30)64ft^2/R10                       [ceiling]
>         +24h(70-30)4x64ft^2/R10                     [remainder of cube.]
>
>which makes Tc = 96 F, if I did that right. 
>
>In case 2,
>
>   51.2K = 6h(70-30)64ft^2/R2+18h(70-30)64ft^2/R12   [south wall]
>         +24h(Tc-30)64ft^2/R10                       [ceiling]
>         +24h(70-30)4x64ft^2/R10                     [remainder of cube.]
>
>which makes Tc = 128 F.
>
>Nick