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Heat Transfer Analysis (heat + transfer_analysis)

Distribution by Scientific Domains
Engineering75%

Selected Abstracts

Determination of activation temperature of glass bulb sprinklers using a thermal liquid bath

FIRE AND MATERIALS, Issue 4 2006
Mohammed M. Khan
Abstract A thermal liquid bath was used to determine the activation temperature of a wide range of temperature rated (57,182°C) glass bulb (3 and 5 mm diameters) sprinklers using water and glycerine. An optical switch and a thermocouple were installed adjacent to each sprinkler (within 10 mm) to record the activation of each glass bulb in the liquid bath having a uniform temperature distribution (±0.5°C). All the tests for determining the activation temperatures of glass bulb sprinklers were conducted in the liquid bath using a 0.277°C/min rate of temperature rise. Based on a heat transfer analysis, this rate is within the maximum allowable rate of rise of water and glycerine temperatures, which allows the glass bulb temperature to closely follow the liquid temperature. The sprinkler activation temperature was evaluated in terms of percentage rating, which is expressed as the percent variation of the average activation temperature, as measured in the liquid bath, from the nominal rated temperature. Sprinklers (93°C rated or lower) activation temperatures in water were consistently within ±3.5% of rating. In glycerine, the activation temperatures of sprinklers rated between 93 and 182°C performed within 3.5% of their rating. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Boiling heat transfer coefficient of R22 and an HFC/HC refrigerant mixture in a fin-and-tube evaporator of a window air conditioner

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2010
M. Herbert Raj
Abstract The commonly used refrigerant in unitary type air conditioners is R22 and its phase out schedule in developing countries is to commence from 2015. Many alternatives to R22 are found in published literature in which R407C has similar characteristics to those of R22 except for its zeotropic nature. However, R407C which is an HFC is made compatible with the mineral oil lubricant in the system compressor by the addition of 20% of HC. This HFC/HC mixture called the M20 refrigerant mixture is reported to be a retrofit refrigerant for R22. Though its latent heat value is greater than that of R22, its refrigerating capacity is lower when it is used to retrofit R22 window air conditioners. Hence, a heat transfer analysis was conducted in the evaporator of a room air conditioner, for practically realized heat flux conditions during standard performance testing. The tests were conducted as per the BIS and ASHRAE standards. Kattan,Thome,Favrat maps are used to confirm the flow patterns, which prevail inside the fin-and-tube evaporator in the tested operating conditions. It is revealed that the heat transfer coefficient/heat fluxes are poorer for M20 because of the lower mass flow rate and higher vapor fraction at the entry of the evaporator than that of R22 in the prevailing operating conditions. The heat transfer coefficients of the M20 refrigerant mixture under various test conditions are lower in the range of 14% to 56% than those of R22. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/htj.20299 [source]

Enhanced heat transfer analysis of latent functionally thermal fluid

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2004
Fengwu Bai
Abstract A physical model has been developed to analyze the enhanced heat transfer process of the latent functionally thermal fluid with microencapsulated phase-change material. The problem is solved by the combination of the finite difference method and the moving heat source method. The calculated results reveal that putting the phase-change microcapsules into the fluids can enhance the heat transfer capabilities of the mixture. The effects of capsule radius and concentration of particles are numerically predicted. The numerical results provide the theoretical basis for the application and design of the latent functionally thermal fluid. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(6): 383,392, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20025 [source]

Particle surface temperature measurements with multicolor band pyrometry

AICHE JOURNAL, Issue 1 2009
Hong Lu
Abstract A noncontact, color-band pyrometer, based on widely available, inexpensive digital imaging devices, such as commercial color cameras, and capable of pixel-by-pixel resolution of particle-surface temperature and emissivity is demonstrated and described. This diagnostic instrument is ideally suited to many combustion environments. The devices used in this method include color charge-coupled device (CCD), or complementary metal oxide semiconductor (CMOS) digital camera, or any other color-rendering camera. The color camera provides spectrally resolved light intensity data of the image, most commonly for three color bands (Red, Green, and Blue,), but in some cases for four or more bands or for a different set of colors. The CCD or CMOS sensor-mask combination has a specific spectral response curve for each of these color bands that spans the visible and often near infrared spectral range. A theory is developed, based on radiative heat transfer and camera responsivity that allows quantitative surface temperature distribution calculation, based on a photograph of an object in emitted light. Particle surface temperature calculation is corrected by heat transfer analysis with reflection between the particle and reactor wall for particles located in furnace environments, but such corrections lead to useful results only when the particle temperature is near or below the wall temperatures. Wood particle-surface temperatures were measured with this color-band pyrometry during pyrolysis and combustion processes, which agree well with thermocouple measured data. Particle-surface temperature data simultaneously measured from three orthogonal directions were also mapped onto the surface of a computer generated 3-D (three-dimensional) particle model. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]