an experimental investigation to study temperature distribution and thermal transfer in a crucible furnace with oscillating combustion.
The introduction of energy is one of the most critical input resources in the heat transfer industry, and new combustion concepts are needed to improve energy efficiency and reduce emissions.
The increasing energy demand, coupled with limited energy resources, the increase in fossil fuel costs and the huge impact on the environment deserve attention and efforts should be made to improve the utilization efficiency of fuel and thermal energy [1].
The concept of heat transfer or the so-called film
Newton proposed high efficiency, depending on the properties of the flow fluid, the thermal conductivity, viscosity, density and specific heat are called transmission properties that play a vital role in better heat transfer [j]2].
The magnitude of the heat transfer of any furnace from hot gas to load depends on the temperature distribution inside the furnace.
Usually, the temperature distribution through the body changes with location and time.
The temperature distribution in the furnace crucible is an important operating variable and is a function of the material used in the building, the temperature in the metal
Refractory interface, etc. [3].
According to Sang Heon Han and others.
The mathematical temperature field of a plate or load is controlled by the following transient heat conduction equation [rho]c [
Partial derivativeT/[
Partial derivativet = [
Partial derivative/[
Partial derivativex ([lambda][
Partial derivativeT/[
Partial derivativex)+ [
Partial derivative/[
Partial derivativey ([lambda][
Partial derivativeT/[
Partial derivativey)+ [
Partial derivative/[
Partial derivativez ([lambda][
Partial derivativeT/[
Partial derivativez)where [rho], c, [lambda]
Mass density, specific heat and thermal conductivity of [plates]4]. K.
Kurpisz applied the inverse thermal conductivity method to determine the temperature distribution by measuring the temperature of some selected points to overcome the common difficulties in any numerical method that requires information on all boundary conditions.
It is also assumed that the temperature distribution in the area under consideration satisfies Fourier-
Kirchoff equation [5]. ([[
Partial derivative. sup. 2]T/[
Partial derivative[x. sup. 2])+ ([[
Partial derivative. sup. 2]T/[
Partial derivative[y. sup. 2])+ ([[
Partial derivative. sup. 2]T/[
Partial derivative[z. sup. 2])= 1/[alpha]([
Partial derivativeT/[
Partial derivative[tau])Where [alpha]= k/[c. sub. p]\'[alpha]
Known as the diffusion coefficient of the material, it illustrates the propagation of heat through the material.
This is an important factor in the general method of thermal conductivity.
However, usually in the furnace, as the relative height of the furnace increases, the temperature distribution along the width of the furnace wall decreases.
In the lower part of the furnace, the temperature and heat flow distribution are very different
Uniform and asymmetrical width along the furnace wall. [6].
It is well known that radiation heat transfer is a major heat transfer mode for the heating load inside the furnace. According to R. Ford, N. V.
Surya Narayana et al. Carried out more than 90% heat transfer through radiation [in the furnace]7].
Oscillating combustion is a modified technology involving forced oscillation of fuel flow rate to [furnace]8].
These vibrations produce continuous fuel. rich and fuel-
Lean area in the furnace.
Due to the brighter fuel-rich zone, the heat transfer from flame to load increases, the load heats up faster, and the turbulence increases due to the turbulence flow [9].
The length of the oscillating flame is longer and due to the fuel-rich and fuel -
Only when the thermal energy of the flame in the rich fuel area passes heat to the load will the lean area be mixed, resulting in a reduction in the low peak furnace temperature and additional NOx generation [10].
John C. Proposed a scaling analysis.
Transient boundary layer established by Patterson and others on non-following vertical walls
Instantaneous heating in the form of applied wall temperature, for a period of time, the Wall temperature increases linearly to the specified steady state value [11].
The enhanced heat transfer rate depends on the temperature gradient inside the furnace, and it is usually found that the top surface temperature is always higher than the bottom surface temperature.
Oscillating combustion is a new improvement and effective method to enhance the heat transfer to the load by utilizing the oscillating flow field with different flame zones.
This can reduce energy consumption and directly reduce emission levels.
It is reported that the working of the oscillating combustion mode is limited.
By measuring the temperature of the selected point in the furnace in the stable and oscillating combustion mode, the temperature distribution data is obtained, and these values show how different they are from the predicted ones.
This paper summarizes the work of improving furnace efficiency with diesel as fuel, by closely monitoring the temperature of several selected points in the furnace at an equal time interval, and studies the temperature distribution and heat transfer rate.
Non-transient changes in mean temperature and temperature
Observe the uniformity of the load and compare between oscillation and non-oscillation
Oscillation modes and methods of combustion materials description of experimental equipment: experimental equipment has a small stove with different cruci racks, a blower with a motor and an air-box.
The air box is connected to the \"u\" tube force gauge to calculate the air flow into the furnace.
The gun burner used can adjust the fuel and air volume through the nozzle.
A digital temperature indicator with a thermocouple, placed in different positions of the furnace used to record temperature and heat transfer.
It is located in about 2 barrels of oil.
The burner is equipped with 3-5 m above the level-
Road Cocks and pressure measuring tubes are used to measure fuel consumption from time to time during operation to obtain a consistent value of total fuel consumption = 0. 0829 [m. sup. 3]
Model: 3 PH induction motor, rotation speed: 2880 rpm, Power: 2. 2 kW, 3 HP, 4. 5 A, 415 V.
Burner data: Manufacturer: Bajaj Engineering, model: gun blower data: Manufacturer: Bajaj Engineering, blower model: l motor power: 2. 2 kW.
Fuel drum: inner diameter = 0.
457 m, the cross section area of the drum = 0. 164[m. sup. 2]
Metal Processing = aluminum thermocouple used = \"k\" type, range = 276-1000[degrees]
Sensing probes and digital temperature indicators, test points = 3 experimental study of temperature distribution and heat transfer in the furnace it is quite complicated to determine the temperature distribution in the furnace around the load.
The thermal conductivity of the furnace wall, the convection heat transfer of hot gas to the load and the penetration of heat into the load through conduction are not simple, because the temperature distribution inside the furnace is not measured in the axial direction.
The temperature in the furnace changes rapidly in the y directionaxis (
Towards the height of the Furnace)
Along x-axis (
Radius of the Furnace)
Towards load).
The method of any numerical method requires information about all boundary conditions, and it is sometimes troublesome to determine the boundary conditions.
These difficulties can be overcome by selecting several points to measure the temperature inside the furnace.
The furnace is divided into three areas in the middle and higher areas, and two points in the middle area are selected, because the load is placed in the area, heat transfer is considered to be higher in the area.
The third point is selected at the entrance of the chimney close to the furnace wall for the escape of high temperature flue gas.
Molten aluminum is contained within the region, defined by a thermal gradient, which assumes a higher heat transfer.
As we all know, in order to improve the efficiency of the crucble furnace, one of the main factors is the heat transfer between the hot gas and the load.
Therefore, it is important to study the heat transfer coefficient between furnace wall and load.
Due to the oscillation generated by the oscillation valve, the performance features of the oscillation valve and the non-oscillation valve are different
Oscillating combustion.
Due to the oscillation of load and non-
The oscillation mode of combustion and heat transfer depends directly on the operating parameters.
Through experiments on these combustion heat transfer modes, the melting load process can be realized from the obtained data.
The heat transfer coefficient can be represented by the equation below. q = -(k [
Partial derivativeT/[
Partial derivativey| [sub. y=0](1)
According to Newton\'s law, heat flow can be written by heat transfer coefficient \"h\" q = h [DELTA]T (2)
By combining the equation, we have h =-[(k [
Partial derivativeT/[
Partial derivativey). sub. y]/[DELTA]T (3)
Therefore, we need the temperature gradient at the furnace wall and load to determine the heat transfer co-
This in turn requires a temperature distribution inside the furnace.
Sometimes it is difficult to determine by experimental measurements, because the temperature changes depending on the point and the point, and because of the difference in the thermal boundary layer in the furnace.
Obviously, heat transfer is common.
The efficient \"h\" depends on the properties of the fluid. i. e. density \'[rho]\', viscosity \'[mu]
Heat conductivity \'K\' and specific heat. [c. sub. p].
So h = f ([u. sub. m], [rho], [mu], k, [c. sub. p], D)(4)
And give the relevant infinite number ,[Re. sub. L]. = u D/[gamma]and Nu. . = hD/k, (5)
Since the Reynolds number is found to be high and the flow of a fluid or gas is considered as turbulence, Dittus and Boelter associations are used to calculate the nosel number.
Nu tus is related to Boelter, Nu. = 0. 023 [([Re. sub. L]). sup. . 8][(Pr). sup. 4](6)Where [Re. sub. L]
= Renault, Nu
= Number of Nusselt.
Operating conditions diesel for melting aluminum loads.
Tested at different aluminum loads of 6, 10, 15, 20 and 25 kg
10, 15 and 20 kg in the oscillation mode and oscillation mode of the parameter Air
The fuel ratio, load, amplitude and frequency of the oscillation valve.
From the data obtained from these experiments, in the oscillating combustion mode, the melting time is short, lower than the energy consumption, and the thermal efficiency is improved.
Oscillation mode. .
These values were found to be higher in the air of 13:1 and 15:1fuel ratios.
Maximum efficiency observed in 13:1 Airfuel ratio.
As shown in the figure, in the schematic diagram crucble furnace in the figure, several points in the furnace are selected
1, where the heat transfer rate of the load is considered to be the largest, especially under the load that is processed.
Place several thermocouple with digital temperature indicator and study the temperature distribution and heat transfer rate of oscillation and non-oscillation
Periodic oscillating combustion mode.
The analysis given here is 13:1 air-
Fuel ratio, 20 kg load, 20 [degrees]
Amplitude and 5hz frequency.
The melting of aluminum depends on the thermal conditions in the furnace.
Temperature, conductivity, speed, viscosity, density, furnace diameter of the gas.
Of all the measurable parameters of the combustion process, temperature is the most important parameter in the combustion process.
The temperature distribution in the furnace affects the heat transfer rate of the load and its effect on the performance properties.
The influence of oscillation on temperature distribution conditions.
A/F ratio = 13:1 load = 20 kg amplitude = 20 [degrees]N.
O = no oscillation W.
Oscillation frequency = 5Hz [
Figure 1 slightly][
Figure 2:[
Figure 3 slightly]
Table space nuclear power source and non-temperature distribution in the monthly furnace
Measure the oscillation and oscillating combustion modes at equal intervals (
Every 10 minutes)
For the conditions mentioned.
However, the temperature distribution in both combustion modes is shown and analyzed separately. From the Fig.
3 points 【T. sub. 1]
The oscillating combustion mode shows that the temperature range is not
The oscillation mode and higher temperature were observed at the end of the operation of 40 to 50 minutes.
The maximum temperature difference is about 130 [degrees]
C. The end of the operation was 20 minutes, and the Edge was found after 40 minutes of the operation.
The results show that the maximum difference still exists before reaching a stable state and a high radiation state.
Due to the minimum thermal gradient at the position, the difference decreases at the end regardless of the combustion mode.
However, the temperature obtained in the oscillation mode must ensure the process operation of melting aluminum due to increased heat transfer and thermal conductivity in the load. [
Figure 4 slightly][
Figure 5 Slightly]
Degree of temperature]T. sub. 2]
Observed in Africa
It can be observed from the diagram that the oscillating combustion ratio is oscillating combustion4.
This trend continues until the end of the operation.
Although the temperature change under the oscillation condition shows an increase, in the non-
Oscillating and oscillating combustion modes.
The temperature difference is on the rise, or the non-
The oscillation mode reaches 940 [degrees]C.
Even after 30 minutes of operation, the maximum difference in temperature still exists when the furnace has to reach a high radiation temperature. Fig.
4 explain that high-incidence light and long-length flame generated during the fuel process
The rich area of the oscillating combustion mode transfers heat from the flame to the load before mixing with the continuous fuel
Lean area in furnace.
This leads to lower availability of thermal energy in temperature measurements.
Where, as a non-heat transfer rate
The oscillation mode is in a steady state, so the temperature is higher at the specified point.
Designated point 【T. sub. 3]
Table 1 and Figure
5 shows a higher temperature at the end of the non-processing time
The oscillation mode burns more than the oscillation mode.
Thermal gradient in two operating modes [T. sub. 2]as well as [T. sub. 3]
In non-high
Oscillation mode opposite to point [T. sub. 1].
The specified point is closer to the furnace wall and closer to the furnace stack.
The temperature distribution along the furnace varies with the increase of height and width.
In the middle area and near the chimney, the flue gas or hot gas contains the highest temperature.
As we all know, the temperature change is very high for non-high temperature environment
Oscillation mode. In the non-
In the oscillation mode, the slow propagation of heat to the load increases the temperature of the isolated part or the point near the furnace and is away from the load, and at the same time, the heat loss in the environment is also increasing.
In addition, as the heat radiates to the nearby area over time, reaching the highest temperature on the furnace wall helps to record the highest temperature.
However, in the oscillating mode of combustion, at this point, the temperature is lower than the steady state mode at the beginning, and the running time is up to 20 minutes, but within the gradual time interval, the temperature lags far behind the steady state mode.
This is due to the impact and penetration mass of the high turbulent oscillation flame on the load resulting in low temperatures.
Measurement uncertainty is well known that the reduction of measurement errors leads to convergence and accuracy.
The uncertainty of the direct measurement of temperature, flow rate, fuel consumption, operating conditions of the oscillation valve and the state of metal melting is inevitable.
In the hypothetical measurement, the marginal error of 2 [degrees]to 4[degrees]
In terms of temperature, taking into account the temperature difference between the two temperatures, the measurement error may be [+ or -]10[degrees]
Depending on the state of the measurement.
The calculation error may be similar to other physical values.
However, when the temperature gradient exists, the influence of oscillation on heat transfer is minimized, and experience shows that heat is transferred from high temperature to low temperature area, heat transfer is proportional to the temperature gradient and to the area perpendicular to the direction of heat flow.
The heat flow of the load is analyzed and calculated from the temperature distribution in the furnace
Oscillation and oscillation modes of combustion. [
Figure 6 slightly]Here, Fig.
6 and Table II show The Infinite Reynolds number of [different temperature fields]T. sub. 1], [T. sub. 2]and [T. sub. 3]
In both combustion modes, every once in a while.
Number of Renault [T. sub. 3]
It was observed to be larger [T. sub. 2]and [T. sub. 1]during non-
Oscillating combustion, but found a higher mode of oscillating combustion.
Over time, Renault numbers gradually began to decay.
It is well known that the heat transfer rate of the load depends on the Reynolds number.
As the number increases, the flow becomes more turbulent and the heat transfer rate changes.
The change of the 3-point Reynolds number can be analyzed as that the turbulent flame spreads rapidly upward in the radial direction in the oscillating combustion mode (
In the direction of \'y)
Greater than axial (
\"X\" in the direction of load)
To the position of the specified temperature point.
In addition, the Reynolds number depends on its weekly distance from the load and the change in the viscosity of the gas movement.
Over time, the heat transfer to the load increases, and the number of Renault [s] changes dramaticallyT. sub. 3]
But the temperature field in [T. sub. 1]
Renault number.
Relatively high. [
Figure 7 Slightly]Fig.
7 and table 3 explain the relationship between the Nusselt number and the time interval.
The convection coefficient of heat transfer or the number of nusel is a function of the Reynolds number and the number of prantel.
The nosel number is a non-dimensional temperature gradient on the surface and a measure of the convection energy transfer on the surface.
We see that the convection coefficient in forced convection heat transfer is a function of the Reynolds number and the Prandtle number. [
Figure 8:[
Figure 9 omitted
As can be seen from the figure
8 found a high number of Renault during non-period
The oscillating combustion mode is more than the oscillating mode, so the Nusselt number.
It is found that the number of Nusselt is proportional to the temperature gradient during the oscillation mode of the specified point, and it shows a downward trend over time.
The larger the Reynolds number and the nosel number, the higher the heat transfer rate to the load.
The heat transfer rate to the load has a point on the nosel number and the Renault number. [
Figure 10 slightly]From the Fig.
9 and Table 4, it can be clearly seen that the heat transfer rate of the load is higher at [temperature]T. sub. 1]
During the period of oscillation combustion, the continuous time interval continues to remain high. [T. sub. 2]and [T. sub. 3]
The area is the next high temperature area.
Under steady state conditions, the thermal gradient between the load and the gas at the temperature field is higher [T. sub. 2]
Higher than the temperature between the [furnace wall] and the hot gasT. sub. 3].
Temperature difference is a potential factor driving the radiation flux. Since the fuel-
The rich zone flame is brighter, longer in length and more turbulent, it can impact into the crucible, and most of the radiation flux in the flame will flow into the load.
Analysis of the experimental results when the load is heated, usually the heating speed at its corner is faster than in any other area.
Heat penetrates into the load in all directions or in x, y, z directions.
However, the highest temperature point is located in the corner of the load, not in the internal area of the load surface.
Therefore, there is also a temperature gradient on the load surface in different regions, which is due to the rapid heating of the surface corners.
In the normal combustion mode of the furnace, the thermal boundary layer is a major concern.
It has a bad effect on the heat transfer rate of the load.
The rupture of the thermal boundary layer is the result of an increase in the heat transfer rate from the hot gas to the oscillating combustion of the load.
With the increase of time during the experiment, it is clear that the temperature difference between the hot gas and the load becomes very small in the oscillating combustion mode.
In this combustion mode, the radiation heat flow or hot gas temperature in the reactor area is lower compared to the steady state.
This is because the load at its location receives a large part of the radiation flux or heat from the gas and from the radiation from the furnace wall.
Therefore, it is found that the temperature is low at a higher position.
However, the gas will escape as the heat enters the chimney.
The cumulative heat transfer of hot gas directly or indirectly to the load through the refractory is a function of time.
Higher speeds shorten the time to complete heat transfer within a given flow path length or furnace size.
Fossil fuel combustion converts chemical energy into a visible heat that increases the temperature of the combustion gas.
The resulting hot gas immediately passes the heat to the cooler solid at a rate proportional to its temperature difference by convection and gas radiation.
If the dwell time is lower than the heat transfer rate, it is shown that the firing rate increases due to the increase in gas volume and temperature.
Therefore, the gas flow rate increases in the air-rich mixing areafuel ratio.
The radiation emitted by the hot gas impacts the wall of the fire-proof brick of the furnace as well as the inventory or load.
The temperature gradient is the main reason for driving the radiation flux from the furnace wall and the convection and radiation heat transfer of hot gas to load or inventory.
When there is a large radiation flux between the hot gas and the load, it can be understood to form a large heat flow around the Crucible or load.
Since the thermal gradient between the load and the hot gas is greater than the thermal gradient between the furnace wall and the hot gas, most of the radiation flux of the hot gas flows into the load, so the load heats up faster.
Therefore, a thermal gradient was found between the furnace wall and the hot gas and between the hot gas and the load.
Continuous fuel caused by oscillating combustion mode-
Rich areas, thanks to the thermal gradient between the hot gas and the load, are able to break the thermal boundary layer that develops around the furnace load.
Emissions in experiments for different air the stack gas of the furnace was observed
The fuel ratio, load, frequency and amplitude of the oscillating combustion valve.
Significantly reduced smoke volume and reduced pollution emissions were observed.
It was found that the amount of exhaust gas was clean and no soot or black smoke was observed.
Conclusion experimental studies were carried out to study the temperature distribution and radiation heat transfer properties of aluminum load in fuel combustion crucble furnace in steady state and oscillating combustion mode.
The temperature measurements of different selected points in the furnace were recorded using a thermocouple with a digital indicator, and the heat transfer rate in the furnace was analyzed using data.
Reynolds number and nussel number are important non-dimensional numbers to predict the heat transfer behavior in the furnace.
The two combustion modes were accurately observed for heating properties at equal time intervals, and the effects of changes in heating time on furnace load during melting were studied.
It is observed that most of the radiation flux and convection heat transfer to the load are the result of different heat gradients ([DELTA]T)
Between the wall and the heat, heat and load.
Similarly, when melting the load, the conduction of heat in the load has also received a lot of attention.
Due to the fact that in the oscillating combustion mode, the thermal gradient under the hot gas and the load is greater than the furnace wall and the hot gas, thereby maximizing the heat transfer to the load, thus shortening the melting time and reducing the fuel consumption, lower than the energy, improve the efficiency of the furnace.
The analysis shows that if the time required for temperature growth on the furnace wall is large enough, the thermal boundary layer will reach a quasi-
The furnace wall reaches a stable state before the highest temperature.
This happened in Africa.
Oscillation mode of combustion.
In this combustion mode, the thickness of the thermal boundary layer increases first, and then shrinks with the increase of time, and the fluid acceleration also changes the properties.
If the growth period of the furnace wall temperature is short enough, the start of the hot boundary layer will be different.
The following important conclusions are drawn from the experimental research work: * temperature difference is a potential factor driving the radiation flux.
The load temperature observed during oscillating combustion indicates a high heat transfer rate.
* The high Reynolds number and the nosel number indicate that the heat transfer rate of the load is higher in the oscillating combustion mode.
Over time, both Renault and nussel numbers are low, but the heat transfer rate is high compared to non-Renault numbers
Oscillation mode.
* Due to oscillation, the heat transfer rate in the furnace seems to be more unstable, and these conditions are important in many applications of heat transfer.
* The heat transfer rate at 3 Selected points gives different data.
However, it is mainly the heat transfer rate flow from [T. sub. 2]zone to [T. sub. 1]zone. That [T. sub. 2]to [T. sub. 1]
Indicates the maximum heat transfer to the load.
At the beginning, the heat transfer rate is higher, and the heat transfer rate is reduced as the load is heated further.
* However, the heat transfer rate is higher in the oscillating combustion mode.
Heat transfer speed from 2. 72% to 8.
45% * Low melting time.
* Low energy consumption.
* According to the conditions, the change of fuel savings in the oscillating combustion mode is 7% to 38%.
* Furnace efficiency increased from 2% to 6%.
With all of the above features, the concept of oscillating combustion technology is superior to the standard steady-state combustion technology currently used in the heat transfer industry in terms of energy conservation and corresponding fuel cost savings, and significantly helps to reduce pollutant emissions.
The author thanks P for its management. R. R. M.
School of Engineering, R. R. Dist.
Andhra Pradesh, India.
To provide facilities for performing this experimental analysis in the production technology laboratory of mechanical engineering department.
Naming [rho]= Density, [mu]= Viscosity, [alpha]= Thermal co-eff.
Diffusion coefficient, q = heat flow, h = heat transfer rate ,[u. sub. m]
= Average speed, v = moving viscosity, k or [lambda]
= Thermal conductivity ,[DELTA]
T = thermal gradient ,[c. sub. p]
Or c = specific heat, T = temperature, Q = heat transfer rate, Hz = frequency ,[infinity]= Free-
Flow conditions, x, y = horizontal and vertical co-ordinates, [Re. sub. L]
= Renault number, Pr = prantel number, Nu = nusel number.
References [1]Fadare, D. A. , Bamiro, O. A. , and Oni, A.
O, \"energy analysis of power and pallet organic fertilizer production in Nigeria\", Journal of ARPN Engineering and Applied Science, Vol. 4, NO. 4, Jun 2009. [2]Arora, C.
Textbook \"Heat Transfer. \" [3]
Luis Felip Verdeja, Robert Gonzalez and Alejandro Ordonez, using the finite element method to determine the temperature distribution in the blast furnace cylinder, \"JOM, February 2000. [4]
Sangheon, Seung Wook Back, Man Young Kim, transient radiation heating properties of plates in a walking beam heating furnace, International Journal of Heat Transfer and mass transfer, 52 (2009)1005-1011 [5]
Kurpisz, K, \"a method for determining the steady-state temperature distribution of the furnace cylinder lining by measuring the temperature of the selected point\"28, 1988 (927). [6]
SenLi, Tongma KU, Qulon et al, \"the role of coalover-
In the International Journal of Thermal Science, coal reburns on the temperature and heat flow distribution of a 1 MW cut-round combustion furnace. [7]R. Ford, N. V.
Surya Narayana et al. Established a heat transfer model of the heating furnace solid plate/water-cooled slide tube, iron mark, steel mark, 7 (1980), 140-146. [8]
Spring 2002-Energy
Office of Industrial Technology. \" [9]
Wagner John C, \"demonstration of oscillation combustion of high temperature forging furnace\", Final Report project work of GTI Project No. 40444, 2001. [10]
Lunitin O de La Broy
Wait, \"oxygen combustion in re-heating furnace\" 2001: 5: 217-Joint International Workshop on combustion240. [11]John C.
Patterson, Cheng Wang Lei, et al. , \"the scale of the non-stationary natural convection boundary layer and the scale of the non-stationary natural convection boundary layer
\"J. Govardhan (1)and G. V. S. Rao (2)(1,2)
Department of Mechanical Engineering, PRRM College of Engineering, Shabad, 509 217, JNTUH, Hyderabad, A. P. , India (1)E-
Email: govardhan58
The increasing energy demand, coupled with limited energy resources, the increase in fossil fuel costs and the huge impact on the environment deserve attention and efforts should be made to improve the utilization efficiency of fuel and thermal energy [1].
The concept of heat transfer or the so-called film
Newton proposed high efficiency, depending on the properties of the flow fluid, the thermal conductivity, viscosity, density and specific heat are called transmission properties that play a vital role in better heat transfer [j]2].
The magnitude of the heat transfer of any furnace from hot gas to load depends on the temperature distribution inside the furnace.
Usually, the temperature distribution through the body changes with location and time.
The temperature distribution in the furnace crucible is an important operating variable and is a function of the material used in the building, the temperature in the metal
Refractory interface, etc. [3].
According to Sang Heon Han and others.
The mathematical temperature field of a plate or load is controlled by the following transient heat conduction equation [rho]c [
Partial derivativeT/[
Partial derivativet = [
Partial derivative/[
Partial derivativex ([lambda][
Partial derivativeT/[
Partial derivativex)+ [
Partial derivative/[
Partial derivativey ([lambda][
Partial derivativeT/[
Partial derivativey)+ [
Partial derivative/[
Partial derivativez ([lambda][
Partial derivativeT/[
Partial derivativez)where [rho], c, [lambda]
Mass density, specific heat and thermal conductivity of [plates]4]. K.
Kurpisz applied the inverse thermal conductivity method to determine the temperature distribution by measuring the temperature of some selected points to overcome the common difficulties in any numerical method that requires information on all boundary conditions.
It is also assumed that the temperature distribution in the area under consideration satisfies Fourier-
Kirchoff equation [5]. ([[
Partial derivative. sup. 2]T/[
Partial derivative[x. sup. 2])+ ([[
Partial derivative. sup. 2]T/[
Partial derivative[y. sup. 2])+ ([[
Partial derivative. sup. 2]T/[
Partial derivative[z. sup. 2])= 1/[alpha]([
Partial derivativeT/[
Partial derivative[tau])Where [alpha]= k/[c. sub. p]\'[alpha]
Known as the diffusion coefficient of the material, it illustrates the propagation of heat through the material.
This is an important factor in the general method of thermal conductivity.
However, usually in the furnace, as the relative height of the furnace increases, the temperature distribution along the width of the furnace wall decreases.
In the lower part of the furnace, the temperature and heat flow distribution are very different
Uniform and asymmetrical width along the furnace wall. [6].
It is well known that radiation heat transfer is a major heat transfer mode for the heating load inside the furnace. According to R. Ford, N. V.
Surya Narayana et al. Carried out more than 90% heat transfer through radiation [in the furnace]7].
Oscillating combustion is a modified technology involving forced oscillation of fuel flow rate to [furnace]8].
These vibrations produce continuous fuel. rich and fuel-
Lean area in the furnace.
Due to the brighter fuel-rich zone, the heat transfer from flame to load increases, the load heats up faster, and the turbulence increases due to the turbulence flow [9].
The length of the oscillating flame is longer and due to the fuel-rich and fuel -
Only when the thermal energy of the flame in the rich fuel area passes heat to the load will the lean area be mixed, resulting in a reduction in the low peak furnace temperature and additional NOx generation [10].
John C. Proposed a scaling analysis.
Transient boundary layer established by Patterson and others on non-following vertical walls
Instantaneous heating in the form of applied wall temperature, for a period of time, the Wall temperature increases linearly to the specified steady state value [11].
The enhanced heat transfer rate depends on the temperature gradient inside the furnace, and it is usually found that the top surface temperature is always higher than the bottom surface temperature.
Oscillating combustion is a new improvement and effective method to enhance the heat transfer to the load by utilizing the oscillating flow field with different flame zones.
This can reduce energy consumption and directly reduce emission levels.
It is reported that the working of the oscillating combustion mode is limited.
By measuring the temperature of the selected point in the furnace in the stable and oscillating combustion mode, the temperature distribution data is obtained, and these values show how different they are from the predicted ones.
This paper summarizes the work of improving furnace efficiency with diesel as fuel, by closely monitoring the temperature of several selected points in the furnace at an equal time interval, and studies the temperature distribution and heat transfer rate.
Non-transient changes in mean temperature and temperature
Observe the uniformity of the load and compare between oscillation and non-oscillation
Oscillation modes and methods of combustion materials description of experimental equipment: experimental equipment has a small stove with different cruci racks, a blower with a motor and an air-box.
The air box is connected to the \"u\" tube force gauge to calculate the air flow into the furnace.
The gun burner used can adjust the fuel and air volume through the nozzle.
A digital temperature indicator with a thermocouple, placed in different positions of the furnace used to record temperature and heat transfer.
It is located in about 2 barrels of oil.
The burner is equipped with 3-5 m above the level-
Road Cocks and pressure measuring tubes are used to measure fuel consumption from time to time during operation to obtain a consistent value of total fuel consumption = 0. 0829 [m. sup. 3]
Model: 3 PH induction motor, rotation speed: 2880 rpm, Power: 2. 2 kW, 3 HP, 4. 5 A, 415 V.
Burner data: Manufacturer: Bajaj Engineering, model: gun blower data: Manufacturer: Bajaj Engineering, blower model: l motor power: 2. 2 kW.
Fuel drum: inner diameter = 0.
457 m, the cross section area of the drum = 0. 164[m. sup. 2]
Metal Processing = aluminum thermocouple used = \"k\" type, range = 276-1000[degrees]
Sensing probes and digital temperature indicators, test points = 3 experimental study of temperature distribution and heat transfer in the furnace it is quite complicated to determine the temperature distribution in the furnace around the load.
The thermal conductivity of the furnace wall, the convection heat transfer of hot gas to the load and the penetration of heat into the load through conduction are not simple, because the temperature distribution inside the furnace is not measured in the axial direction.
The temperature in the furnace changes rapidly in the y directionaxis (
Towards the height of the Furnace)
Along x-axis (
Radius of the Furnace)
Towards load).
The method of any numerical method requires information about all boundary conditions, and it is sometimes troublesome to determine the boundary conditions.
These difficulties can be overcome by selecting several points to measure the temperature inside the furnace.
The furnace is divided into three areas in the middle and higher areas, and two points in the middle area are selected, because the load is placed in the area, heat transfer is considered to be higher in the area.
The third point is selected at the entrance of the chimney close to the furnace wall for the escape of high temperature flue gas.
Molten aluminum is contained within the region, defined by a thermal gradient, which assumes a higher heat transfer.
As we all know, in order to improve the efficiency of the crucble furnace, one of the main factors is the heat transfer between the hot gas and the load.
Therefore, it is important to study the heat transfer coefficient between furnace wall and load.
Due to the oscillation generated by the oscillation valve, the performance features of the oscillation valve and the non-oscillation valve are different
Oscillating combustion.
Due to the oscillation of load and non-
The oscillation mode of combustion and heat transfer depends directly on the operating parameters.
Through experiments on these combustion heat transfer modes, the melting load process can be realized from the obtained data.
The heat transfer coefficient can be represented by the equation below. q = -(k [
Partial derivativeT/[
Partial derivativey| [sub. y=0](1)
According to Newton\'s law, heat flow can be written by heat transfer coefficient \"h\" q = h [DELTA]T (2)
By combining the equation, we have h =-[(k [
Partial derivativeT/[
Partial derivativey). sub. y]/[DELTA]T (3)
Therefore, we need the temperature gradient at the furnace wall and load to determine the heat transfer co-
This in turn requires a temperature distribution inside the furnace.
Sometimes it is difficult to determine by experimental measurements, because the temperature changes depending on the point and the point, and because of the difference in the thermal boundary layer in the furnace.
Obviously, heat transfer is common.
The efficient \"h\" depends on the properties of the fluid. i. e. density \'[rho]\', viscosity \'[mu]
Heat conductivity \'K\' and specific heat. [c. sub. p].
So h = f ([u. sub. m], [rho], [mu], k, [c. sub. p], D)(4)
And give the relevant infinite number ,[Re. sub. L]. = u D/[gamma]and Nu. . = hD/k, (5)
Since the Reynolds number is found to be high and the flow of a fluid or gas is considered as turbulence, Dittus and Boelter associations are used to calculate the nosel number.
Nu tus is related to Boelter, Nu. = 0. 023 [([Re. sub. L]). sup. . 8][(Pr). sup. 4](6)Where [Re. sub. L]
= Renault, Nu
= Number of Nusselt.
Operating conditions diesel for melting aluminum loads.
Tested at different aluminum loads of 6, 10, 15, 20 and 25 kg
10, 15 and 20 kg in the oscillation mode and oscillation mode of the parameter Air
The fuel ratio, load, amplitude and frequency of the oscillation valve.
From the data obtained from these experiments, in the oscillating combustion mode, the melting time is short, lower than the energy consumption, and the thermal efficiency is improved.
Oscillation mode. .
These values were found to be higher in the air of 13:1 and 15:1fuel ratios.
Maximum efficiency observed in 13:1 Airfuel ratio.
As shown in the figure, in the schematic diagram crucble furnace in the figure, several points in the furnace are selected
1, where the heat transfer rate of the load is considered to be the largest, especially under the load that is processed.
Place several thermocouple with digital temperature indicator and study the temperature distribution and heat transfer rate of oscillation and non-oscillation
Periodic oscillating combustion mode.
The analysis given here is 13:1 air-
Fuel ratio, 20 kg load, 20 [degrees]
Amplitude and 5hz frequency.
The melting of aluminum depends on the thermal conditions in the furnace.
Temperature, conductivity, speed, viscosity, density, furnace diameter of the gas.
Of all the measurable parameters of the combustion process, temperature is the most important parameter in the combustion process.
The temperature distribution in the furnace affects the heat transfer rate of the load and its effect on the performance properties.
The influence of oscillation on temperature distribution conditions.
A/F ratio = 13:1 load = 20 kg amplitude = 20 [degrees]N.
O = no oscillation W.
Oscillation frequency = 5Hz [
Figure 1 slightly][
Figure 2:[
Figure 3 slightly]
Table space nuclear power source and non-temperature distribution in the monthly furnace
Measure the oscillation and oscillating combustion modes at equal intervals (
Every 10 minutes)
For the conditions mentioned.
However, the temperature distribution in both combustion modes is shown and analyzed separately. From the Fig.
3 points 【T. sub. 1]
The oscillating combustion mode shows that the temperature range is not
The oscillation mode and higher temperature were observed at the end of the operation of 40 to 50 minutes.
The maximum temperature difference is about 130 [degrees]
C. The end of the operation was 20 minutes, and the Edge was found after 40 minutes of the operation.
The results show that the maximum difference still exists before reaching a stable state and a high radiation state.
Due to the minimum thermal gradient at the position, the difference decreases at the end regardless of the combustion mode.
However, the temperature obtained in the oscillation mode must ensure the process operation of melting aluminum due to increased heat transfer and thermal conductivity in the load. [
Figure 4 slightly][
Figure 5 Slightly]
Degree of temperature]T. sub. 2]
Observed in Africa
It can be observed from the diagram that the oscillating combustion ratio is oscillating combustion4.
This trend continues until the end of the operation.
Although the temperature change under the oscillation condition shows an increase, in the non-
Oscillating and oscillating combustion modes.
The temperature difference is on the rise, or the non-
The oscillation mode reaches 940 [degrees]C.
Even after 30 minutes of operation, the maximum difference in temperature still exists when the furnace has to reach a high radiation temperature. Fig.
4 explain that high-incidence light and long-length flame generated during the fuel process
The rich area of the oscillating combustion mode transfers heat from the flame to the load before mixing with the continuous fuel
Lean area in furnace.
This leads to lower availability of thermal energy in temperature measurements.
Where, as a non-heat transfer rate
The oscillation mode is in a steady state, so the temperature is higher at the specified point.
Designated point 【T. sub. 3]
Table 1 and Figure
5 shows a higher temperature at the end of the non-processing time
The oscillation mode burns more than the oscillation mode.
Thermal gradient in two operating modes [T. sub. 2]as well as [T. sub. 3]
In non-high
Oscillation mode opposite to point [T. sub. 1].
The specified point is closer to the furnace wall and closer to the furnace stack.
The temperature distribution along the furnace varies with the increase of height and width.
In the middle area and near the chimney, the flue gas or hot gas contains the highest temperature.
As we all know, the temperature change is very high for non-high temperature environment
Oscillation mode. In the non-
In the oscillation mode, the slow propagation of heat to the load increases the temperature of the isolated part or the point near the furnace and is away from the load, and at the same time, the heat loss in the environment is also increasing.
In addition, as the heat radiates to the nearby area over time, reaching the highest temperature on the furnace wall helps to record the highest temperature.
However, in the oscillating mode of combustion, at this point, the temperature is lower than the steady state mode at the beginning, and the running time is up to 20 minutes, but within the gradual time interval, the temperature lags far behind the steady state mode.
This is due to the impact and penetration mass of the high turbulent oscillation flame on the load resulting in low temperatures.
Measurement uncertainty is well known that the reduction of measurement errors leads to convergence and accuracy.
The uncertainty of the direct measurement of temperature, flow rate, fuel consumption, operating conditions of the oscillation valve and the state of metal melting is inevitable.
In the hypothetical measurement, the marginal error of 2 [degrees]to 4[degrees]
In terms of temperature, taking into account the temperature difference between the two temperatures, the measurement error may be [+ or -]10[degrees]
Depending on the state of the measurement.
The calculation error may be similar to other physical values.
However, when the temperature gradient exists, the influence of oscillation on heat transfer is minimized, and experience shows that heat is transferred from high temperature to low temperature area, heat transfer is proportional to the temperature gradient and to the area perpendicular to the direction of heat flow.
The heat flow of the load is analyzed and calculated from the temperature distribution in the furnace
Oscillation and oscillation modes of combustion. [
Figure 6 slightly]Here, Fig.
6 and Table II show The Infinite Reynolds number of [different temperature fields]T. sub. 1], [T. sub. 2]and [T. sub. 3]
In both combustion modes, every once in a while.
Number of Renault [T. sub. 3]
It was observed to be larger [T. sub. 2]and [T. sub. 1]during non-
Oscillating combustion, but found a higher mode of oscillating combustion.
Over time, Renault numbers gradually began to decay.
It is well known that the heat transfer rate of the load depends on the Reynolds number.
As the number increases, the flow becomes more turbulent and the heat transfer rate changes.
The change of the 3-point Reynolds number can be analyzed as that the turbulent flame spreads rapidly upward in the radial direction in the oscillating combustion mode (
In the direction of \'y)
Greater than axial (
\"X\" in the direction of load)
To the position of the specified temperature point.
In addition, the Reynolds number depends on its weekly distance from the load and the change in the viscosity of the gas movement.
Over time, the heat transfer to the load increases, and the number of Renault [s] changes dramaticallyT. sub. 3]
But the temperature field in [T. sub. 1]
Renault number.
Relatively high. [
Figure 7 Slightly]Fig.
7 and table 3 explain the relationship between the Nusselt number and the time interval.
The convection coefficient of heat transfer or the number of nusel is a function of the Reynolds number and the number of prantel.
The nosel number is a non-dimensional temperature gradient on the surface and a measure of the convection energy transfer on the surface.
We see that the convection coefficient in forced convection heat transfer is a function of the Reynolds number and the Prandtle number. [
Figure 8:[
Figure 9 omitted
As can be seen from the figure
8 found a high number of Renault during non-period
The oscillating combustion mode is more than the oscillating mode, so the Nusselt number.
It is found that the number of Nusselt is proportional to the temperature gradient during the oscillation mode of the specified point, and it shows a downward trend over time.
The larger the Reynolds number and the nosel number, the higher the heat transfer rate to the load.
The heat transfer rate to the load has a point on the nosel number and the Renault number. [
Figure 10 slightly]From the Fig.
9 and Table 4, it can be clearly seen that the heat transfer rate of the load is higher at [temperature]T. sub. 1]
During the period of oscillation combustion, the continuous time interval continues to remain high. [T. sub. 2]and [T. sub. 3]
The area is the next high temperature area.
Under steady state conditions, the thermal gradient between the load and the gas at the temperature field is higher [T. sub. 2]
Higher than the temperature between the [furnace wall] and the hot gasT. sub. 3].
Temperature difference is a potential factor driving the radiation flux. Since the fuel-
The rich zone flame is brighter, longer in length and more turbulent, it can impact into the crucible, and most of the radiation flux in the flame will flow into the load.
Analysis of the experimental results when the load is heated, usually the heating speed at its corner is faster than in any other area.
Heat penetrates into the load in all directions or in x, y, z directions.
However, the highest temperature point is located in the corner of the load, not in the internal area of the load surface.
Therefore, there is also a temperature gradient on the load surface in different regions, which is due to the rapid heating of the surface corners.
In the normal combustion mode of the furnace, the thermal boundary layer is a major concern.
It has a bad effect on the heat transfer rate of the load.
The rupture of the thermal boundary layer is the result of an increase in the heat transfer rate from the hot gas to the oscillating combustion of the load.
With the increase of time during the experiment, it is clear that the temperature difference between the hot gas and the load becomes very small in the oscillating combustion mode.
In this combustion mode, the radiation heat flow or hot gas temperature in the reactor area is lower compared to the steady state.
This is because the load at its location receives a large part of the radiation flux or heat from the gas and from the radiation from the furnace wall.
Therefore, it is found that the temperature is low at a higher position.
However, the gas will escape as the heat enters the chimney.
The cumulative heat transfer of hot gas directly or indirectly to the load through the refractory is a function of time.
Higher speeds shorten the time to complete heat transfer within a given flow path length or furnace size.
Fossil fuel combustion converts chemical energy into a visible heat that increases the temperature of the combustion gas.
The resulting hot gas immediately passes the heat to the cooler solid at a rate proportional to its temperature difference by convection and gas radiation.
If the dwell time is lower than the heat transfer rate, it is shown that the firing rate increases due to the increase in gas volume and temperature.
Therefore, the gas flow rate increases in the air-rich mixing areafuel ratio.
The radiation emitted by the hot gas impacts the wall of the fire-proof brick of the furnace as well as the inventory or load.
The temperature gradient is the main reason for driving the radiation flux from the furnace wall and the convection and radiation heat transfer of hot gas to load or inventory.
When there is a large radiation flux between the hot gas and the load, it can be understood to form a large heat flow around the Crucible or load.
Since the thermal gradient between the load and the hot gas is greater than the thermal gradient between the furnace wall and the hot gas, most of the radiation flux of the hot gas flows into the load, so the load heats up faster.
Therefore, a thermal gradient was found between the furnace wall and the hot gas and between the hot gas and the load.
Continuous fuel caused by oscillating combustion mode-
Rich areas, thanks to the thermal gradient between the hot gas and the load, are able to break the thermal boundary layer that develops around the furnace load.
Emissions in experiments for different air the stack gas of the furnace was observed
The fuel ratio, load, frequency and amplitude of the oscillating combustion valve.
Significantly reduced smoke volume and reduced pollution emissions were observed.
It was found that the amount of exhaust gas was clean and no soot or black smoke was observed.
Conclusion experimental studies were carried out to study the temperature distribution and radiation heat transfer properties of aluminum load in fuel combustion crucble furnace in steady state and oscillating combustion mode.
The temperature measurements of different selected points in the furnace were recorded using a thermocouple with a digital indicator, and the heat transfer rate in the furnace was analyzed using data.
Reynolds number and nussel number are important non-dimensional numbers to predict the heat transfer behavior in the furnace.
The two combustion modes were accurately observed for heating properties at equal time intervals, and the effects of changes in heating time on furnace load during melting were studied.
It is observed that most of the radiation flux and convection heat transfer to the load are the result of different heat gradients ([DELTA]T)
Between the wall and the heat, heat and load.
Similarly, when melting the load, the conduction of heat in the load has also received a lot of attention.
Due to the fact that in the oscillating combustion mode, the thermal gradient under the hot gas and the load is greater than the furnace wall and the hot gas, thereby maximizing the heat transfer to the load, thus shortening the melting time and reducing the fuel consumption, lower than the energy, improve the efficiency of the furnace.
The analysis shows that if the time required for temperature growth on the furnace wall is large enough, the thermal boundary layer will reach a quasi-
The furnace wall reaches a stable state before the highest temperature.
This happened in Africa.
Oscillation mode of combustion.
In this combustion mode, the thickness of the thermal boundary layer increases first, and then shrinks with the increase of time, and the fluid acceleration also changes the properties.
If the growth period of the furnace wall temperature is short enough, the start of the hot boundary layer will be different.
The following important conclusions are drawn from the experimental research work: * temperature difference is a potential factor driving the radiation flux.
The load temperature observed during oscillating combustion indicates a high heat transfer rate.
* The high Reynolds number and the nosel number indicate that the heat transfer rate of the load is higher in the oscillating combustion mode.
Over time, both Renault and nussel numbers are low, but the heat transfer rate is high compared to non-Renault numbers
Oscillation mode.
* Due to oscillation, the heat transfer rate in the furnace seems to be more unstable, and these conditions are important in many applications of heat transfer.
* The heat transfer rate at 3 Selected points gives different data.
However, it is mainly the heat transfer rate flow from [T. sub. 2]zone to [T. sub. 1]zone. That [T. sub. 2]to [T. sub. 1]
Indicates the maximum heat transfer to the load.
At the beginning, the heat transfer rate is higher, and the heat transfer rate is reduced as the load is heated further.
* However, the heat transfer rate is higher in the oscillating combustion mode.
Heat transfer speed from 2. 72% to 8.
45% * Low melting time.
* Low energy consumption.
* According to the conditions, the change of fuel savings in the oscillating combustion mode is 7% to 38%.
* Furnace efficiency increased from 2% to 6%.
With all of the above features, the concept of oscillating combustion technology is superior to the standard steady-state combustion technology currently used in the heat transfer industry in terms of energy conservation and corresponding fuel cost savings, and significantly helps to reduce pollutant emissions.
The author thanks P for its management. R. R. M.
School of Engineering, R. R. Dist.
Andhra Pradesh, India.
To provide facilities for performing this experimental analysis in the production technology laboratory of mechanical engineering department.
Naming [rho]= Density, [mu]= Viscosity, [alpha]= Thermal co-eff.
Diffusion coefficient, q = heat flow, h = heat transfer rate ,[u. sub. m]
= Average speed, v = moving viscosity, k or [lambda]
= Thermal conductivity ,[DELTA]
T = thermal gradient ,[c. sub. p]
Or c = specific heat, T = temperature, Q = heat transfer rate, Hz = frequency ,[infinity]= Free-
Flow conditions, x, y = horizontal and vertical co-ordinates, [Re. sub. L]
= Renault number, Pr = prantel number, Nu = nusel number.
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\"J. Govardhan (1)and G. V. S. Rao (2)(1,2)
Department of Mechanical Engineering, PRRM College of Engineering, Shabad, 509 217, JNTUH, Hyderabad, A. P. , India (1)E-
Email: govardhan58
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