Experimental techniques for measuring temperature and velocity fields to improve the use and validation of building heat transfer models

Conference · Wed Apr 01 04:00:00 EST 1998

OSTI ID:828538

Griffith, Brent ^[1]; Turler, Daniel; Goudey, Howdy; Arasteh, Dariush

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1. LBNL Library

When modeling thermal performance of building components and envelopes, researchers have traditionally relied on average surface heat-transfer coefficients that often do not accurately represent surface heat-transfer phenomena at any specific point on the component being evaluated. The authors have developed new experimental techniques that measure localized surface heat-flow phenomena resulting from convection. The data gathered using these new experimental procedures can be used to calculate local film coefficients and validate complex models of room and building envelope heat flows. These new techniques use a computer-controlled traversing system to measure both temperatures and air velocities in the boundary layer near the surface of a building component, in conjunction with current methods that rely on infrared (IR) thermography to measure surface temperatures. Measured data gathered using these new experimental procedures are presented here for two specimens: (1) a Calibrated Transfer Standard (CTS) that approximates a constant-heat-flux, flat plate; and (2) a dual-glazed, low-emittance (low-e), wood-frame window. The specimens were tested under steady-state heat flow conditions in laboratory thermal chambers. Air temperature and mean velocity data are presented with high spatial resolution (0.25- to 25-mm density). Local surface heat-transfer film coefficients are derived from the experimental data by means of a method that calculates heat flux using a linear equation for air temperature in the inner region of the boundary layer. Local values for convection surface heat-transfer rate vary from 1 to 4.5 W/m{sup 2} {center_dot} K. Data for air velocity show that convection in the warm-side thermal chamber is mixed forced/natural, but local velocity maximums occur from 4 to 8 mm from the window glazing.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: USDOE. Assistant Secretary for Energy Efficiency and Renewable Energy. Building Technologies Program. State and Community Programs. Office of Building Systems (US)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 828538
• Report Number(s): LBNL--41772
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
BOUNDARY LAYERS
CONVECTION
GLAZING MATERIALS
HEAT FLUX
HEAT TRANSFER
PERFORMANCE
SIMULATION
SPATIAL RESOLUTION
THERMOGRAPHY
VALIDATION
VELOCITY