Window Convection and Surface Temperature

asked 2020-05-07 16:08:00 -0500

morronini's avatar

updated 2020-05-08 18:13:12 -0500

Hello folks. I'm using EnergyPlus, and I'm having some general problems with surface temperatures being much higher than expected in a zone. In analyzing a window, I've found a problem with the heat transfer coefficients and surface temperatures not lining up.

For a single timestep, I performed a basic calculation relying on the fact that temperature difference across a construction layer should be approximately proportional to the ratio (R_layer/R_tot). The window is a single layer window, modeled as a SimpleGlazingSystem.

These are the outputted temperatures:

T_inside-air = 22 [C]; T_inside-face = 10.5 [C]; T_outside-face = -16 [C]; T_outside-air = -22 [C]

These are the outputted heat transfer coefficients: (neglecting radiation)

h_inside-face = 2 [W/(m^2K)]; U_window = 1.7 [W/(m^2K)]; h_outside-face = 5.5 [W/(m^2*K)]

The ratios (R_layer/R_tot) from inside to outside are [0.4, 0.46, 0.14]. For this timestep, the temperature differences should then be [17.5, 20.5, 6] [C], but instead, they are [11.5, 26.5, 6] [C].

This seems like too big of a difference to come from neglecting radiation. Besides this, I turned off all internal gains in this room. I've played around with changing conduction and convection algorithms, but since this calculation takes the convective heat transfer coefficients themselves, the algorithm should have no effect. Any help diagnosing this problem would be appreciated.

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