Radiation heat loss

For simplicity of the model, it is assumed that the natural convection, radiation, and ionic wind effect are ignored. The ignorance of the radiation loss from the spark channel during the discharge may be reasonable, because the radiation heat loss is found to be negligibly small in the previous studies [5,6]. The amount of heat transfer from the flame kernel to the spark electrodes, whose temperature is 300 K, is estimated by Fourier s law between the electrode surface and an adjacent cell. 

Transient computations of methane, ethane, and propane gas-jet diffusion flames in Ig and Oy have been performed using the numerical code developed by Katta [30,46], with a detailed reaction mechanism [47,48] (33 species and 112 elementary steps) for these fuels and a simple radiation heat-loss model [49], for the high fuel-flow condition. The results for methane and ethane can be obtained from earlier studies [44,45]. For propane. Figure 8.1.5 shows the calculated flame structure in Ig and Og. The variables on the right half include, velocity vectors (v), isotherms (T), total heat-release rate ( j), and the local equivalence ratio (( locai) while on the left half the total molar flux vectors of atomic hydrogen (M ), oxygen mole fraction oxygen consumption rate... 

If the fuel is modified such that k l-1/2, then the radiant flux for 1 small becomes consistent with conduction as q" l1/2, and the radiation heat loss goes as required, l5/2. Alternatively, if radiation is believed to dominate, it might be useful to consider k large and ignore II5 but require that... 

Computational studies of partially premixed flames have also been reported [11-16], Authors have tried to explain the variation of NO emission indices with the level of partial premixing using one or more of the following residence time, flame stretch, radiation heat loss, and chemical mechanism-based arguments. However, a complete explanation of the NO emission has not been offered in the literature. 

The heat conducted through the plate must be equal to the sum of convection and radiation heat losses ... 

An infinite plate of thickness 2L is suddenly exposed to a constant-temperature radiation heat source or sink of temperature T,. The plate has a uniform initial temperature of T,. The radiation heat loss from each side of the plate is given by q - surface area. Assuming that the plate behaves as a lumped capacity, that is, k — =0, derive an expression for the temperature of the plate as a function of time. 

A long pipe 5 cm in diameter passes through a room and is exposed to air at atmospheric pressure and temperature of 20°C. The pipe surface temperature is 93°C. Assuming that the emissivity of the pipe is 0.6, calculate the radiation heat loss per foot of length of pipe. 

A long steel pipe with a 5-cm ID and 3.2-mm wall thickness passes through a large room maintained at 30°C and atmospheric pressure 0.6 kg/s of hot water enters one end of the pipe at 82°C. If the pipe is 15 m long, calculate the exit water temperature, considering both free convection and radiation heat loss from the outside of the pipe. 

A 30-cm-long, 0.5-cm-diamcter electric resistance wire is used to detenniiie the convection heat transfer coefficient in air at 25°C experimentally. The surface temperature of the wire is measured to be 230°C when the electric power consumption is 180 W. If the radiation heat loss from the wire is calculated to be 60 W, Ihe convection heat transfer coefficient is (a) 186 W/m -X (b) 158 W/m -X... 

Sensible heat from the clothed skin is first transferred to the clothing and then from the clothing to the enviromneot, The convection and radiation heat losses from the outer surface of a clothed body can be expressed as... 

Total sensible heat loss can also be expressed conveniently by combining the convection and radiation heat losses as... 

Analysis (a) The emissivity of liquid water is given in Table A-18 to be 0.95. Then the radiation heat loss from the water to the surrounding surfaces. becomes... 

Radiation heat loss from the fryer, furnace, and other ancillaries. 

It may be assumed that 7.5 lb of dry gas is generated for every 10,000 Btu of waste burned in the incinerator. In addition, 0.51 lb of moisture is produced for every 10,000 Btu of waste fired. Air cools the incinerator shell at a flow of 10,000 Ib/h (this air is discharged to the atmosphere at 400°F). Assume the air entering the incinerator has a humidity of 0.015 lb of moisture per pound of dry air and the ash produced has a heating value of lOOBtu/lb (assume no fly ash). The radiation heat loss from the shell is 1% of the total heating value of the waste. The temperature of the products of combustion (the flue gas) must not be less than 2000°F. The following information is required ... 

Other factors also contribute to improved furnace efficiency. Higher oxy/fuel flame temperatures improve heat transfer to the glass melt by radiation. Tighter control of stoichiometry in the flame region allows the furnace to run with a lower excess oxygen ratio. For full oxy/fuel, radiation heat losses through ports are reduced since fewer ports are needed. 

Convection and radiation depend upon whether the tanks are insulated or not, and the ambient air temperature, especially during the winter. Measurements of convection and radiation heat losses are, on average, 5% or less of total heat of fermentation (winter and uninsulated tanks). 

The temperature of seawater is fixed at the sea surface by heat exchange with the atmosphere. The average incoming energy from the Sun at the Earth s surface is about four times higher at the equator than at the poles. The average infrared radiation heat loss... 

Abstract Results from the four-year long heating phase of the Drift-Scale Heater Test at the Exploratory Studies Facility at Yucca Mountain, Nevada, provide a basis to evaluate conceptual and numerical models used to simulate thermal-hydrological coupled processes expected to occur at the proposed repository. A three-dimensional numerical model was built to perform the analyses. All model simulations were predicated on a dual (fracture and matrix) continuum conceptualization. A 20-percent reduction in the canister heat load to account for conduction and radiation heat loss through the bulkhead, a constant pressure boundary condition at the drift wall, and inclusion of the active fracture model to account for a reduction in the number of fractures that were hydraulically active provided the best agreement between model results and observed temperatures. The views expressed herein are preliminary and do not constitute a final judgment of the matter addressed or of the acceptability of its use in a license application... 

This method was applied to produce carbides of titanium, zirconium, lead, and bismuth (Barcicki Myrdzik, 1974). Applications ofthe method are limited becanse of insufficient contact between solid particles in the presence of plasma flow if the solid mixtnre is not bricked or sintered. The efficiency of the process arranged in bricks or sintered solid mixture is limited by radiation heat losses and insufficient heat transfer inside of the brick, especially taking into account the decrease of density dne to CO formation (7-92). The most effective condensed-phase synthesis of carbides (7-92) is that from melt containing carbon compounds (Tumanov, 1981). A relevant example is the synthesis of carbides of uraninm and plutonium from a melt containing their nitrites and carbon compoimds (Coppinger Johnson, 1969). 

Transparent honeycomb covers with channels parallel to the sunlight have proven effective in decreasing the convection within the collector and the radiation heat losses, while reducing the amount of light entering less than the additional cover sheet that they replace. Honeycombs have been successfully constructed from PVF, FEP, and PC. 

To ensure the best possible accuracy, the sample may be placed under vacuum to minimize convection. The measuring chamber is wrapped in thermal blankets to maintain the temperature and minimize radiation heat losses. Finally, the thermocouples are chosen to minimize heat losses. Using this method, the thermal conductivity of the metal heated to 600 °C can be measured. 

During the simulation, radiation heat losses from the exposed surfaces are considered, with the assumption that the ambient temperature, the voltage drop, or... 

Radiation heat losses from the solar reactor (Qre-radiation)... 

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