Tunnel testing

Tunnel Test. The tunnel test is widely used to test the flame spread potential of building products such as electrical cable (15) and wall coverings (16). The test apparatus consists of a tunnel 7.62 x 0.445 m x 0.305 m ia cross section, one end of which contains two gas burners. The total heat suppHed by the burners is 5.3 MJ/min. The test specimen (7.62 m x 50.8 cm), attached to the ceiling, is exposed to the gas flames for 10 minutes while the maximum flame spread, temperature, and smoke evolved are measured. The use of this and other flame spread test methods has been reviewed (17). 

The PVC formulations shown in Table 2 represent typical compounds used by the wine and cable industry. PVC compounders have developed new PVC-based formulations with very good fire and smoke properties (can pass the UL 910 Steiner Tunnel test) that compete with the more expensive fluoropolymers. These can be used in fabricating telecommunication cables usable for plenum area appHcations. 

Flame Resistance. Traditionally, small-scale laboratory flammabiUty tests have been used to initially characterize foams (38). However, these do not reflect the performance of such materials in bulk form. Fire characteristics of thermal insulations for building appHcations are generally reported in the form of quaHtative or semiquantitative results from ASTM E84 or similar tunnel tests (39). Similar larger scale tests are used for aircraft and marine appHcations. 

Two coefficients have been defined. Cl and Co, relating velocity, density, area, and lift or drag forces. These coefficients can be calculated from wind-tunnel tests and plotted as shown in Figure 7-6b versus the angle of attack... 

Another method is a series of exhaust dilution equations based on Wilson and Lamb " and a series of earlier papers summarized in ASHRAE. This method is based on wind tunnel tests on simplified buildings and is intended to provide conservative (low dilution) results. Wilson and Lamb compared the model to actual field data collected at a university campus and found that the model did indeed predict dilutions similar to measured worst-case dilutions suitable for a screening model. However, many cases resulted in conservative Linderpredictions of dilutions. ... 

Murakami, S., A. Mochida, R. Ooka, S. Kato, and S. lizuka. 1996. Numerical prediction of flow around a building with various turbulence models Comparison of fe-e, EVM, ASM, DSM, and LES with wind tunnel tests. ASHRAE Transactions, vol. 102, no. I. 

Data are available only for simple building geometries. In Allard," a tool for the calculation of wind pressure coefficients for simple geometries is made available, and another tool is described in Knoll et al. Existing wind pressure data have to be examined carefully, because many data represent peak pressure values needed for static building analysis. Real cases with obstructions and buildings in the close surroundings are difficult to handle. Wind-tunnel tests on scale models or CFD analysis will be required. 

They chose an airfoil shape that, based on the collective data from their wind tunnel tests, would give a high L/D. The airfoil used on the... 

The drag coefficient for an antomohile body is typically estimated from wind-tunnel tests. In the wind tunnel, the drag force acting on a stationaiy model of the vehicle, or the vehicle itself, is measured as a stream of air is blown over it at the simulated vehicle speed. Drag coefficient depends primarily on the shape of the body, but in an actual vehicle is also influenced by other factors not always simulated in a test model. 

A technique which can assist in the scale-up of commercial plants designs is the use of scale models. A scale model is an experimental model which is smaller than the hot commercial bed but which has identical hydrodynamic behavior. Usually the scale model is fluidized with air at ambient conditions and requires particles of a different size and density than those used in the commercial bed. The scale model relies on the theory of similitude, sometimes through use of Buckingham s pi theorem, to design a model which gives identical hydrodynamic behavior to the commercial bed. Such a method is used in the wind tunnel testing of small model aircraft or in the towing tank studies of naval vessels. 

Tunnel Test. NBS Tech. Note 945. National Bureau of Standards Washington, DC, 1977. 

The use of field cages or semifield tunnel tests was originally devised by Gerig [71] and has constituted a useful and cost-effective part of the hazard evaluation... 

Tunneling, in QEDs, 22 169 Tunnel test, 11 458 Turbidimetric agglutination immunoassays, 14 140-142 Turbidimetry, 13 143 Turbidity... 

Large frontal areas create air turbulence and drag. Bodies derived from wind tunnel testing can provide a more smooth air flow around the vehicle. Details such as mirrors, rain gutters, trim, wheel wells and covers can also be more appropriate for air flow. Radial tires can reduce fuel consumption as much as 3%. Puncture-proof tires of plastic could save even more and eliminate the cost and weight of a spare tire and wheel. 

Lourenco, L., and A. Krothapalli. 1994. Application of PIV in high-speed wind tunnel testing. 32nd Aerospace Sciences Meeting Proceedings. AIAA Paper No. 94-0084. 

Since many polymeric materials are used as clothing, household items, components of automobiles and aircraft, etc. flammability is an important consideration. Some polymers such as polytetrafluoroethylene and PVC are naturally flame-resistant, but most common polymers such as PE and PP are not. Small-scale horizontal flame tests have been used to estimate the flammability of solid (ASTM D-635), cellular (ASTM D-1692-74), and foamed (ASTM D-1992) polymers, but these tests are useful for comparative purposes only. Large-scale tunnel tests (ASTM E-84) are more accurate, but they are also more expensive to run than ordinary laboratory tests cited before. 

VJ As yet we have only done wind tunnel tests of sampling and they look promising, no more. 

Small-scale horizontal flame tests have been used to estimate the flammability of solid (ASTM-D635) and foamed polymers (ASTM-D1992), but these tests are useful for comparative purposes only. Large-scale tunnel tests (ASTM-E84) and corner wall tests are more significant, but they are also more expensive than laboratory tests. 

Wind tunnel test methods were developed to determine wind induced stresses in cooling towers using aeroelastic models as part of a detailed model of a power station site. The turbulence and shear in the atmospheric wind are simulated. Tests on a model of Ferrybridge C Power Station show that resonant stresses are significant at the design wind speed. These increase as the fourth power of wind speed and can be greatly enhanced by turbulent wakes of upstream structures. 6 refs, cited. 

Although the tunnel test is widely accepted, conditions and orientations involved are not those normally found in installed insulations. New laige-scale tests have been developed the results can be taken to represent actual performance more closely. Such tests include the International Conference of Building Officials (ICBO) and ASTM E603 full-scale room tests, ASTM E108 roofing test, the UL roof deck construction test, the Factory Mutual Calorimeter Test, and both alaige- and small-scale comer test. 

Many tests have been devised to evaluate the fire and flame resistance of surface-treated acoustical fiberboard. The most widely accepted test, recognized by both the building industry and the building code agencies, is the fire-resistance test specified in federal specification (3). Other tests under consideration, but not universally adopted, are the tunnel test of the Underwriters Laboratories, Inc. (11), and the Factory Mutual room burn out test (2). A small scale test that is being employed for plant control and quick finish evaluation is the Class F fire test (12). 

---