Onset of the Mutual Thermal Effects of Solid Body and Nanofluid Flow over a Flat Plate Theoretical Study

The falling and settling of solid particles in gases and liquids is a natural phenomenon happens in many industrial processes. This phenomenon has altered pure forced convection to a combination of heat conduction and heat convection in a flow over a plate. In this paper, the coupling of conduction (inside the plate) and forced convection of a non-homogeneous nanofluid flow (over a flat plate) is investigated, which is classified in conjugate heat transfer problems. Two-component four-equation non-homogeneous equilibrium model for convective transport in nanofluids (mixture of water with particles<100nm) has been applied that incorporates the effects of the nanoparticles migration due to the thermophoresis and Brownian motion forces. Employing similarity variables, we have transformed the basic non-dimensional partial differential equations to ordinary differential ones and then solved numerically. Moreover, variation of the heat transfer and concentration rates with thermal resistance of the plate is studied in detail. Setting the lowest dependency of heat transfer rate to the thermal resistance of the plate as a goal, we have shown that for two nanofluids with similar heat transfer characteristics, the one with higher Brownian motion (lower nanoparticle diameter) is desired

Evaluating Deck Fire Performance—Limitations of the Test Methods Currently Used in California’s Building Codes

Combustible decks are identified as vulnerable components of buildings in wildfire-prone areas. In California, combustible deck boards can comply with the requirements of Chapter 7A of the California Building Code if they pass an under-deck flame-impingement exposure test. It is desirable if standard test methods can simplify procedures while not adversely affecting the reliability of the test. The test methods should also be able to discriminate the fire performance between products on the market. In this research, the specified conditions in the under-deck flame-impingement test, SFM 12-7A-4A and ASTM E2632, were evaluated. Different deck assemblies were exposed to above-deck ember and under-deck flame-impingement exposures. During the above-deck ember exposure tests, it was observed that embers accumulated in the gaps between deck boards, on top of the support joists, and, when ignition occurred, ignited in this area. Flames spread by burning into unburned areas of the deck boards and joists, thereby providing a pathway to the building. During the under-deck flame-impingement tests, the three assumptions in the standard test method were evaluated, namely, (1) a small deck size can adequately represent the performance of larger decks, (2) the absence of wind will not noticeably influence performance, and (3) differences in joist material would not noticeably change the performance of the deck boards. Results of experiments suggested that the current Chapter 7A compliant deck boards burned intensely and exposed the cladding of the test building, resulting in an elevated temperature at the wall. It is argued that the current assumptions are an oversimplification of real-world fire performance and a change in the current California’s building code is necessary. This research demonstrated the necessity of evaluating an entire deck assembly rather than only the walking surfaces

Evaluating Deck Fire Performance&mdash;Limitations of the Test Methods Currently Used in California&rsquo;s Building Codes

Combustible decks are identified as vulnerable components of buildings in wildfire-prone areas. In California, combustible deck boards can comply with the requirements of Chapter 7A of the California Building Code if they pass an under-deck flame-impingement exposure test. It is desirable if standard test methods can simplify procedures while not adversely affecting the reliability of the test. The test methods should also be able to discriminate the fire performance between products on the market. In this research, the specified conditions in the under-deck flame-impingement test, SFM 12-7A-4A and ASTM E2632, were evaluated. Different deck assemblies were exposed to above-deck ember and under-deck flame-impingement exposures. During the above-deck ember exposure tests, it was observed that embers accumulated in the gaps between deck boards, on top of the support joists, and, when ignition occurred, ignited in this area. Flames spread by burning into unburned areas of the deck boards and joists, thereby providing a pathway to the building. During the under-deck flame-impingement tests, the three assumptions in the standard test method were evaluated, namely, (1) a small deck size can adequately represent the performance of larger decks, (2) the absence of wind will not noticeably influence performance, and (3) differences in joist material would not noticeably change the performance of the deck boards. Results of experiments suggested that the current Chapter 7A compliant deck boards burned intensely and exposed the cladding of the test building, resulting in an elevated temperature at the wall. It is argued that the current assumptions are an oversimplification of real-world fire performance and a change in the current California&rsquo;s building code is necessary. This research demonstrated the necessity of evaluating an entire deck assembly rather than only the walking surfaces