HEAT TRANSFER TO A SUNROOM the affect of window type on heat transfer

The Situation  Clear Day  Mid June  Provo, UT  The Pate’s have recently added a sunroom to the exterior of their home. In the summer the temperature rises in that room a considerable amount. Should they have installed double pane windows instead? Should they invest in windows with reflective coating? How much of a difference would these windows make?

What We Know:  Incident Solar Radiation  East Wall: 5015 W/m 2  South Wall: 2997 W/m 2  West Wall: 5015 W/m 2  Temperature Data  T sur, interior = 20° C  T sur, exterior = 35° C  Physical Properties  Glass (T=300K) 1.4 W/mK  Air K=.0263 W/mK (T=300K)  Areas of Windows:  East Wall 8.09 m 2  South Wall: 6.77 m 2 (x 2) 2.60 m 2 (x2)  West Wall 8.09 m 2  Volume of the Room  60 m 3

What We Assume:  Radiation Properties of Glass  Transmissivity =.95  Absorbtivity = 0  Reflectivity =.05  Emissivity =.9  Neglect radiation out of the room (only consider incident radiation)  No heat transfer through the walls  T sur stays constant  Window areas are all square (see diagram)

Single Pane Glass  h o,i = 6 W/m 2  q conv+cond = 728 W  q rad = 1606 W  q total = 2324 H o, T o H i, T i

Double Pane Glass  Ra L =91.37 Δ T  Ra L max = 1307  1307 < 1708  Convection between planes is negligible.  Transmissivity:.9  Reflectivity:.1  h = 6 W/m 2  q conv+cond = 168 W  q rad = 1522 W  q total = 1690 W H o, T o H i, T i

Double Pane Glass with Coating  Reflective glass  Reflectivity:.28  Transmissivity:.72  Heat transfer from convection and conduction stays the same.  q conv+cond = 168 W  q rad = 1217 W  q total = 1385 W H i, T i H o, T o

Air Conditioning Cost  Single Pane: $  Double Pane: $  Coated Double Pane: $  $.08/KWhr  COP = 3.4  Summer Savings: $94.05  Coating: $36/Window  Estimate: $216 to upgrade, 2.5 Summers to recover the savings

Presented By:  Nathan Honka  Dallin Shaw  Jenny Pate

Appendix A: Radiation Data

Appendix B: Equations  Inside Convection Coefficient  Thermal Resistances

Appendix B: Equations  q conv,i on inner surface:  q cond through window:  q conv,o = q cond = q conv,i  Could not solve that system so we assumed h=6W/m 2 to determine q conv,i and q conv,o.

Appendix C: Spreadsheet Solution SINGLE PANE Area (m 2 )q (cond + conv) q (rad) q (total)

Appendix C: Spreadsheet Solution DOUBLE PANE Area (m 2 )q (cond + conv) q (rad) q (total)

Appendix C: Spreadsheet Solution DOUBLE PANE WITH COATING Area (m 2 )q (cond + conv) q (rad) q (total)

Sources  Incident Solar Radiation Values: olar/images/data_tables/slcbld.jpg