1. Lecture Objectives:
Learn about Boundary Conditions at Internal Surfaces
solar radiation and heat transfer through windows
Internal heat loads
Introduce HW Assignments 1b, and HW2

2. Transmission for single and double glazed window, , ,

3. Heat transfer for double glazed window

4. Internal Boundaries Window Internal sources Transmitted
Solar radiation

5. Distribution of transmitted solar radiation DIRECT solar radiation

6. Distribution of transmitted solar radiation diffuse solar radiation

7. Internal Heat sources Occupants, Lighting, Equipment
Typically - Defined by heat flux
Convective
Directly affect the air temperature
Radiative
Radiative heat flux “distributed” to surrounding surfaces according to the surface area and emissivity

8. Internal Heat sources Lighting systems
Source of convective and radiative heat flux
Different complexity for modeling

9. Surface Balance For each surface – external or internal :
All radiation components
Conduction
Convection
Convection + Conduction + Radiation = 0

10. Air balance - Convection on internal surfaces + Ventilation + Infiltration
Uniform temperature Assumption
Affect the air temperature
- h, and Q as many as surfaces
- maircp.air DTair= Qconvective+ Qventilation
Tsupply
Qconvective= ΣAihi(TSi-Tair)
Ts1 mi
Qventilation= Σmicp,i(Tsupply-Tair) Q1 Q2
Tair h1 h2

11. Air balance – steady state Convection on internal surfaces + Infiltration = Load
Uniform temperature Assumption
h, and Qsurfaces as many as surfaces
infiltration – mass transfer (mi – infiltration)
Qair= Qconvective+ Qinfiltration
T outdoor air
Qconvective= ΣAihi(TSi-Tair)
Ts1 mi
Qinfiltration= Σmicp(Toutdoor_air-Tair) Q1 Q2
In order to keep constant air
Temperate, HVAC system needs
to remove cooling load
Tair h1 h2
QHVAC= Qair= m·cp(Tsupply_air-Tair)
HVAC

12. Homework assignment 1b Top view T_north_o Tnorth_i Tinter_surf Tair_in
IDIR
Idif
Glass
Tinter_surf
Teast_i
Teast_o
Tnorth_i
T_north_o
Tair_out
Styrofoam
Surface radiation
Surface
radiation
2.5 m
8 m
8 m
conduction
East
North