Heat transfer through bark, and the resistance of trees to fire.

1968 ◽  
Vol 16 (3) ◽  
pp. 499 ◽  
Author(s):  
RG Vines
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Thermal Diffusivity ◽  
Moisture Content ◽  
Rate Of Change ◽  
Experimental Measurements ◽  
Simple Mathematical Model ◽  
Bark Thickness ◽  
Calculate Heat Transfer ◽  
Bark Structure

Measurements have been made of cambium temperatures in living trees subjected to mild and fierce fires. Fire resistance depends upon bark thickness: thus only big trees with thick bark can survive unharmed in really severe fires. The rate of change in cambium temperature is related to the thermal diffusivity of the bark, and is largely independent of bark structure or moisture content. A simple mathematical model is used to calculate heat transfer in bark, and the results obtained agree well with experimental measurements made on a variety of trees. Studies of soil temperature and results from experiments on pines are referred to briefly in appendices.

Heat Transfer in the Furnaces of Shell Type Boilers

1973 ◽  
Vol 187 (1) ◽  
pp. 809-816
Author(s):  
D. C. Gunn
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
At Risk ◽  
Current Practice ◽  
Heat Fluxes ◽  
Simple Mathematical Model ◽  
Shell Type ◽  
Not At Risk

Peak heat fluxes which occur near the oil burner can be predicted by a simple mathematical model to within 12 per cent and thus help to estimate peak metal temperatures. Although peaks of 150 000 Btu/ft2 h can occur in current practice, the metal of the furnace is not at risk provided the waterside is clean. Conversely, the risk is great when even a small amount of scale has built up.

The Mathematical Model of Online Quenching for Extruding Bar of 6061 Aluminum Alloy

2011 ◽  
Vol 117-119 ◽  
pp. 1798-1801
Author(s):  
Yi Lin ◽  
De Zhi Li ◽  
Jian Min Zeng ◽  
Ping Chen ◽  
Li Hua Liang
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Aluminum Alloy ◽  
Simple Mathematical Model ◽  
Extrusion Speed ◽  
6061 Aluminum Alloy ◽  
Different Temperatures ◽  
Set Up ◽  
The Mathematical Model ◽  
Quenching Apparatus

A simple mathematical model that correlates the temperature and extrusion speed of a 6061 aluminum bar extruded from the die has been established based on the principle of heat transfer in this paper. The 6061 alloy bar is extruded from the die orifice and is cooled through heat exchanged between the bar and ambient. The temperature of the bar decreases as the distance increases away from the die orifice. The more rapidly the temperature drops, the slower the extrusion speed is. A flexible online quenching apparatus has been set up before the critical quenching position to guarantee good supersaturation of alloying elements. The calculations have shown that at the extrusion speeds of 10m/min, 15 m/min and 20 m/min, the critical quenching positions are 0.44m, 0.88m and 1.30m from the die orifice, respectively for the temperature of 520°C; and for the different temperatures, the critical quenching positions from the die orifice are 0.66m, 1.31m, 1.95m at 530°C and 0.88m, 1.75m, 2.6m at 540°C, respectively.

Numerical and Experimental Analysis of Convection Heat Transfer in a Lean-To Type Greenhouse

Solar Energy ◽  
2004 ◽  
Author(s):  
Wei Chen ◽  
Wei Liu
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Moisture Content ◽  
Gas Flow ◽  
Solar Irradiation ◽  
Wall Material ◽  
Insulation Material ◽  
Remarkable Effect ◽  
The North ◽  
North Wall

In this paper, heat transfer and flow in a lean-to passive solar greenhouse has been studied. A mathematical model based on energy equilibrium and a one-dimensional mathematical model for the unsaturated porous medium have been founded and developed to predict the temperature and moisture content in soil and the enclosed air temperature in the greenhouse. On the condition that plant and massive wall is neglected, the air is mainly heated by the soil surface in the greenhouse, which absorbs the incident solar radiation. With increase in depth, the variation of the temperature and moisture content in soil decreases on account of ambient, and the appearance of the peak temperature in soil postpones. Solar irradiation absorber, heat storage and insulation are the main effects of the north massive wall on greenhouse, which is influenced by the structure and the material. The specific heat capacity and thermal conductivity of wall material have a remarkable effect on the north wall temperature. The build-up north wall with thermal insulation material may be chosen for greenhouse. The temperature distribution and gas flow in greenhouse is influenced by the cover material of the inside surface of the north wall. All results should be taken into account for a better design and run of a greenhouse.

Developing an Accurate Heat Transfer Simulation Model of Alaska Pollock Surimi Paste by Estimating the Thermal Diffusivities at Various Moisture and Salt Contents

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Hyeon W. Park ◽  
Myeong G. Lee ◽  
Jae W. Park ◽  
Won B. Yoon
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusivity ◽  
Moisture Content ◽  
Simulation Model ◽  
Strong Dependence ◽  
Salt Content ◽  
Salt Dependence ◽  
Heat Penetration ◽  
Heat Transfer Simulation ◽  
Thermal Diffusivities

AbstractAlaska pollock (AP) surimi paste was prepared (0–3% salt and 76–84% moisture). The density, specific heat, and thermal conductivity were measured and modelled in temperatures between 25 and 90 °C (R2 > 0.92). The thermal diffusivity (α) function showed a strong dependence on the moisture content and a unique salt dependence at 84% of the moisture content and applied to the heat transfer simulation of surimi paste. The simulation model coupled with the empirical thermal properties accurately predicted the heat penetration curves during heating with RMSE values ranging from 0.43 to 1.22 °C. The salt dependence on thermal diffusivity was identified and modeled only at 84% moisture content. With a model for 84% moisture content, the RMSE value of 3% salt content decreased from 1.11 °C to 0.56 °C. This study demonstrated that an accurate prediction of the heat transfer of the surimi paste needs to be coupled with the nonlinear thermal diffusivity functions.

Mathematical Modelling of Heat Transfer in Mortadella Bologna PGI during Evaporative Pre-Cooling

2014 ◽  
Vol 10 (2) ◽  
pp. 233-241 ◽  
Author(s):  
Massimiliano Rinaldi ◽  
Emma Chiavaro ◽  
Roberto Massini
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mathematical Model ◽  
Heat Transfer Coefficient ◽  
Thermal Diffusivity ◽  
Cooling Process ◽  
Continuous Film ◽  
Cooking Process ◽  
Proposed Model ◽  
Product Surface

Abstract Mortadella evaporative pre-cooling process from 70 to 50°C at core was investigated: the thermal diffusivity and the apparent heat transfer coefficient were experimentally estimated. The effects of ventilation and water spraying with different intervals (0, 5, 10 and 15 min) were tested and core and surface temperatures, cooling times and cook values were compared. Water spraying every 5 min combined with ventilation allowed obtaining both lowest cooling time and cook values in the product. On the contrary, continuous spraying (no interval) presented higher cooling times since probably, after a certain time, water formed a continuous film on product surface, which prevented evaporation. Based on the experimental data, a finite differences mathematical model, previously applied to Mortadella cooking process, was developed and validated by means of two cooling procedures. Acceptable approximation and low percentage errors on final core temperature were obtained, confirming the usefulness and reliability of the proposed model.

Heat Transfer in the Furnaces of Shell Type Boilers

1973 ◽  
Vol 187 (1) ◽  
pp. 809-816 ◽  
Author(s):  
D. C. Gunn
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
At Risk ◽  
Current Practice ◽  
Heat Fluxes ◽  
Simple Mathematical Model ◽  
Shell Type ◽  
Not At Risk

Peak heat fluxes which occur near the oil burner can be predicted by a simple mathematical model to within 12 per cent and thus help to estimate peak metal temperatures. Although peaks of 150 000 Btu/ft2 h can occur in current practice, the metal of the furnace is not at risk provided the waterside is clean. Conversely, the risk is great when even a small amount of scale has built up.

scholarly journals TRANSIENTS PROCESSES UNDER DRYING WITH CONVECTION AND INFRARED RADIATION

2017 ◽  
Vol 60 (10) ◽  
pp. 94
Author(s):  
Anatoly M. Afanas’ev ◽  
Arina V. Nikishova ◽  
Boris N. Siplivy
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Mathematical Model ◽  
Mass Transfer ◽  
Steady State ◽  
Moisture Content ◽  
Infrared Radiation ◽  
Transition Process ◽  
Convective Drying ◽  
Infrared Drying

Based on the theory of the A.V. Lykov for heat and mass transfer the mathematical model of propagation of heat and moisture in a flat sample, which is blown by the air flow and is exposed to infrared radiation. The model is based on the following views: the density of heat loss is determined by the heat transfer by convection and heat exchange by radiation, and the intensity of the mass exchange surface with the environment depends on the difference in partial pressure of water vapor through the thickness of the boundary layer (the boundary condition of mass transfer in the form of Dalton); temperature field inside the material is determined by the heat transfer due to the phenomenon of thermal conductivity, and the presence of internal heat sources caused by the absorption of penetrating electromagnetic radiation and the processes of evaporation (condensation); the transfer of moisture inside the material is partly liquid and partly in vapor form, and is caused by moisture content gradients (diffusion) and temperature (thermal diffusion). The results of analytical calculation of steady-state fields of temperature and moisture content for cases of convective drying and infrared drying, and the results of numerical calculation of the same field in transient conditions are presented. Numerical experiment allows us to estimate the duration of the transition process, as well as the behavior of the differential moisture content between the borders of the plate, with the increase which increases the probability of failure of the sample from mechanical deformation. It is shown that for convective drying of such a danger occurs in the transitional regime, and for infrared drying – mode steady-state. To reduce internal mechanical stresses when drying by convection, avoid sudden temperature changes of the air flow; the time during which there is an increase in air temperature, should be around the time of the transition process. When drying with infrared rays, if the differences of moisture content in the steady state are invalid for their reduction can be used or drying in the oscillating radiation, or drying under the combined effect of the sample electromagnetic waves with large and small penetration depth. The distinction in the nature of transients, infrared drying and drying with hot air can be explained using the formula of Dalton, which is part of the used mathematical model and determining the intensity of the problem through the boundary layer. Due to the great inertia of thermal processes, even in the case where the intensity of the infrared radiation changes rapidly in time (for example at the initial time gap of the first kind), the surface temperature of the material, and with it the intensity of drying, continue to be continuous functions; on the contrary, an abrupt change in air temperature in convective drier automatically leads to a gap function of the flux density of moisture on the surface.Forcitation:Afanas'ev A.M., Nikishova A.V., Siplivy B.N. Transients processes under drying with convection and infrared radiation. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 10. P. 94-101 

Design of the Blast Furnace Wall Structure Made of Efficient Materials. Part 4. Calculation Examples

2020 ◽  
Vol 786 (11) ◽  
pp. 30-34
Author(s):  
A.M. IBRAGIMOV ◽  
◽  
L.Yu. GNEDINA ◽  
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Blast Furnace ◽  
Boundary Value Problems ◽  
Transfer Process ◽  
Rational Design ◽  
Boundary Value ◽  
Heat Transfer Process ◽  
Furnace Wall ◽  
Time Interval

This work is part of a series of articles under the general title The structural design of the blast furnace wall from efficient materials [1–3]. In part 1, Problem statement and calculation prerequisites, typical multilayer enclosing structures of a blast furnace are considered. The layers that make up these structures are described. The main attention is paid to the lining layer. The process of iron smelting and temperature conditions in the characteristic layers of the internal environment of the furnace is briefly described. Based on the theory of A.V. Lykov, the initial equations describing the interrelated transfer of heat and mass in a solid are analyzed in relation to the task – an adequate description of the processes for the purpose of further rational design of the multilayer enclosing structure of the blast furnace. A priori the enclosing structure is considered from a mathematical point of view as the unlimited plate. In part 2, Solving boundary value problems of heat transfer, boundary value problems of heat transfer in individual layers of a structure with different boundary conditions are considered, their solutions, which are basic when developing a mathematical model of a non-stationary heat transfer process in a multi-layer enclosing structure, are given. Part 3 presents a mathematical model of the heat transfer process in the enclosing structure and an algorithm for its implementation. The proposed mathematical model makes it possible to solve a large number of problems. Part 4 presents a number of examples of calculating the heat transfer process in a multilayer blast furnace enclosing structure. The results obtained correlate with the results obtained by other authors, this makes it possible to conclude that the new mathematical model is suitable for solving the problem of rational design of the enclosing structure, as well as to simulate situations that occur at any time interval of operation of the blast furnace enclosure.

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