Temperature Distribution in a Cylindrical Rod Moving From a Chamber at One Temperature to a Chamber at Another Temperature

1964 ◽  
Vol 86 (2) ◽  
pp. 265-270 ◽  
Author(s):  
G. Horvay ◽  
M. Dacosta
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Arbitrary Constant ◽  
Families Of Curves ◽  
Special Cases ◽  
Method Of Solution ◽  
Lower Chamber ◽  
Higher Temperature ◽  
Hopf Method ◽  
The Heat Transfer Coefficient

When an infinitely long cylindrical rod travels from a chamber at one temperature ϑa to a chamber (insulated from the first) at a higher temperature ϑf, then heat will leak out along the rod from the second chamber to the first, whose amount decreases as the speed of the rod increases. Using the Wiener-Hopf method of solution, we determine the temperature distribution in the rod for the case where in the second chamber the heat-transfer coefficient h+ is infinite, while in the first chamber it has an arbitrary constant value h. Families of curves illustrate the temperature distribution in the two special cases where h = ∞ (isothermal boundary conditions in lower chamber) and where h = 0 (rod is insulated in lower chamber).

Experimental and Numerical Evaluation of Small-Scale Cryosurgery Using Ultrafine Cryoprobe

2013 ◽  
Vol 4 (4) ◽  
Author(s):  
Junnosuke Okajima ◽  
Atsuki Komiya ◽  
Shigenao Maruyama
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Numerical Evaluation ◽  
Small Scale ◽  
Outer Diameter ◽  
Cooling Performance ◽  
The Heat Transfer Coefficient

The objective of this work is to experimentally and numerically evaluate small-scale cryosurgery using an ultrafine cryoprobe. The outer diameter (OD) of the cryoprobe was 550 μm. The cooling performance of the cryoprobe was tested with a freezing experiment using hydrogel at 37 °C. As a result of 1 min of cooling, the surface temperature of the cryoprobe reached −35 °C and the radius of the frozen region was 2 mm. To evaluate the temperature distribution, a numerical simulation was conducted. The temperature distribution in the frozen region and the heat transfer coefficient was discussed.

Using ProCAST to Study the Effects of SEED Process Parameters on the Radial Temperature Distribution in Semi-Solid Slugs

2020 ◽  
Vol 993 ◽  
pp. 1004-1010
Author(s):  
Min Luo ◽  
Da Quan Li ◽  
Wen Ying Qu ◽  
Stephen P. Midson ◽  
Qiang Zhu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Transfer Coefficient ◽  
Solid Fraction ◽  
Process Parameters ◽  
Radial Temperature ◽  
Fraction Distribution ◽  
Semi Solid ◽  
The Heat Transfer Coefficient

The SEED (Swirled Enthalpy Equilibrium Device) process was used to produce semi-solid slurries. One of the factors that controls whether or not a slug can be used to produce high quality castings is the solid fraction distribution within the slug, and the solid fraction distribution is strongly dependent upon the temperature distribution. In this study, a model has been developed using ProCAST to investigate the relationship between process parameters and the temperature distribution within slugs. The parameters examined included the heat transfer coefficient between the crucible and slug, the heat transfer coefficient between the crucible and air, the slug diameter, and the initial melt temperature (pouring temperature). It was found that the most important parameters controlling the temperature distribution within slugs were the crucible size and the heat transfer coefficient between crucible and air. Adjustment of other parameters had little influence on the temperature distribution. Processing parameters will be discussed in order to allow the SEED process to be used for the production of large diameter slugs (>100 mm), and for narrow freezing range (0.3<fs<0.5, fs is fraction solid) alloys such as 6063.

Research on the Inversion of Equivalent Surface Heat Transfer Coefficient of Mass Concrete by Calculating its Heat Flux

2012 ◽  
Vol 188 ◽  
pp. 264-269
Author(s):  
Li Xin Qu ◽  
Yi Hong Zhou ◽  
Yao Ying Huang ◽  
Guo Qing Tang ◽  
Shao Wu Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Optical Fiber ◽  
Transfer Coefficient ◽  
Surface Heat ◽  
Mass Concrete ◽  
Surface Heat Transfer Coefficient ◽  
The Heat Transfer Coefficient

Most of the cracks on concrete dam are external ones, while external heat preservation is an important measure to prevent cracking. In order to obtain the actual thermal parameters, according to thermal conduction theory and the temperature distribution conditions of optical fiber on concrete surface, the surface temperature distribution of concrete pouring deck was real-time monitored by setting optical fiber in different depths; then the surface heat flux of mass concrete was calculated, thereby the equivalent surface heat transfer coefficient, which varied as time goes, was inversed. It is indicated that the inversion process is relatively simple and reliable, and the heat transfer coefficient obtained can well reflect the real performance of the insulation materials. Meanwhile, it is also indicated that the heat transfer coefficient of equivalent surface varies as time goes, which can contribute to back analysis calculation and actual engineering practice.

scholarly journals Effect of Velocity and Temperature Distribution at the Hole Exit on Film Cooling of Turbine Blades

1997 ◽  
Vol 119 (2) ◽  
pp. 343-351 ◽  
Author(s):  
V. K. Garg ◽  
R. E. Gaugler
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Turbine Blades ◽  
Suction Surface ◽  
Free Stream Turbulence ◽  
The Heat Transfer Coefficient ◽  
Coolant Velocity

An existing three-dimensional Navier–Stokes code (Arnone et al., 1991), modified to include film cooling considerations (Garg and Gaugler, 1994), has been used to study the effect of coolant velocity and temperature distribution at the hole exit on the heat transfer coefficient on three film-cooled turbine blades, namely, the C3X vane, the VKI rotor, and the ACE rotor. Results are also compared with the experimental data for all the blades. Moreover, Mayle’s transition criterion (1991), Forest’s model for augmentation of leading edge heat transfer due to free-stream turbulence (1977), and Crawford’s model for augmentation of eddy viscosity due to film cooling (Crawford et al., 1980) are used. Use of Mayle’s and Forest’s models is relevant only for the ACE rotor due to the absence of showerhead cooling on this rotor. It is found that, in some cases, the effect of distribution of coolant velocity and temperature at the hole exit can be as much as 60 percent on the heat transfer coefficient at the blade suction surface, and 50 percent at the pressure surface. Also, different effects are observed on the pressure and suction surface depending upon the blade as well as upon the hole shape, conical or cylindrical.

Analytical Study of Heat Transfer When Heating or Cooling a Limited Volume of Liquid

2021 ◽  
pp. 17-34
Author(s):  
A.A. Aleksandrov ◽  
V.A. Akatev ◽  
M.P. Tyurin ◽  
E.S. Borodina ◽  
O.I. Sedlyarov
Keyword(s):  
Heat Transfer ◽  
Exact Solution ◽  
Heat Exchanger ◽  
Analytical Study ◽  
Integral Transform ◽  
Heat Transfer Surface ◽  
Limited Volume ◽  
Special Cases ◽  
The Given ◽  
The Heat Transfer Coefficient

The paper shows the results of analytical studies of heat transfer when heating or cooling a limited volume of liquid. The purpose of the research was to determine the size of the heat transfer surface, with the initial parameters of the coolants, the final temperature in the reactor and its thermal equivalent, as well as the flow rate of the second coolant through the heat exchanger corresponding to the water equivalent at a given cooling time τo. Moreover, if intensive mixing is carried out in the vessel, i.e., if the temperature of the second heat carrier practically does not change along the length of the heat transfer surface, then W2 → ∞. The solution was based on the Laplace --- Carson integral transform. The exact solution was converted for special cases of heat transfer. In particular, it should be noted that in many practical cases formulas give a fairly good approximation to the exact solution. Only at low values of the heat transfer coefficient, as well as when the volume occupied by the coolant inside the heat exchanger is commensurate with the volume of the liquid contained in the vessel, it is necessary to apply the given exact solution

Application of Steady State and Transient IR-Thermography Measurements to Film Cooling Experiments for a Row of Shaped Holes

2005 ◽  
Author(s):  
Dennis Brauckmann ◽  
Jens von Wolfersdorf
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Film Cooling ◽  
Measured Temperature ◽  
Ir Thermography ◽  
Adiabatic Wall ◽  
Test Plate ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
The Heat Transfer Coefficient

This paper presents experimental investigations for the measurement of the adiabatic film cooling effectiveness as well as the heat transfer coefficient distribution in film cooling experiments with a row of fanshaped holes on a flat plate. The temperature distribution on the flat plate is measured using infrared-thermography (IR). Adiabatic wall effectiveness data are obtained using a high-temperature plastic material. Although a low thermal conductivity material is used, the measured temperature distribution is not identical with the adiabatic temperature distribution. The measured temperature field shows influences of 3D heat conduction inside the test plate. The effects of the heat conduction inside the test plate are modeled using the FE-method to re-evaluate the adiabatic wall temperature and to calculate the coolant gas exit temperature, which is used for the adiabatic film cooling effectiveness. For the measurement of the heat transfer coefficient ratio with and without film cooling (hf/h0) a transient method is used. Temperature transients on the test surface are initiated by switching the coolant flow and are recorded using IR-thermography. The measured wall temperature histories are converted into heat flux values assuming a semi-infinite wall model during the experiment.

Exact solution of a nonlinear fin problem of temperature-dependent thermal conductivity and heat transfer coefficient

2020 ◽  
Vol 98 (7) ◽  
pp. 700-712 ◽  
Author(s):  
Sheng-Wei Sun ◽  
Xian-Fang Li
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Transfer Coefficient ◽  
Power Law ◽  
Temperature Dependent ◽  
Fin Efficiency ◽  
Special Cases ◽  
Temperature Dependent Thermal Conductivity

This paper studies a class of nonlinear problems of convective longitudinal fins with temperature-dependent thermal conductivity and heat transfer coefficient. For thermal conductivity and heat transfer coefficient dominated by power-law nonlinearity, the exact temperature distribution is obtained analytically in an implicit form. In particular, the explicit expressions of the fin temperature distribution are derived explicitly for some special cases. An analytical expression for fin efficiency is given as a function of a thermogeometric parameter. The influences of the nonlinearity and the thermogeometric parameter on the temperature and thermal performance are analyzed. The temperature distribution and the fin efficiency exhibit completely different behaviors when the power-law exponent of the heat transfer coefficient is more or less than negative unity.

scholarly journals Modelling of the 1D Convective Heat Exchange between Logs Subjected to Freezing and to Subsequent Defrosting and the Surrounding Environment/ Egydimenziós konvektív hővezetés modellezése fagyott és normál állapotú rönk és környezte között

2015 ◽  
Vol 11 (1) ◽  
pp. 77-88
Author(s):  
Nencho Deliiski ◽  
Veselin Brezin ◽  
Natalia Tumbarkova
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Temperature Distribution ◽  
Radial Direction ◽  
Initial Temperature ◽  
Convective Heat Exchange ◽  
Surrounding Environment ◽  
Effective Specific Heat ◽  
The Heat Transfer Coefficient

Abstract A 1D mathematical model for the computation of the temperature on the surface of cylindrical logs, tsr, and the non-stationary temperature distribution along the radiuses of logs subjected to freezing and subsequent defrosting at convective exponentially changing boundary conditions has been suggested. The model includes mathematical descriptions of the thermal conductivity in radial direction, λr, the effective specific heat capacity, ce, and the density, ρ, of the non-frozen and frozen wood, and also of the heat transfer coefficient between the surrounding air environment and the radial direction of horizontally situated logs, αr. With the help of the model, computations have been carried out for the determination of αr, tsr, λsr, and 1D temperature distribution along the radiuses of beech logs with diameters of 0.24 m, initial temperature 20 °C, and moisture content 0.4 kg·kg-1, 0.8 kg·kg-1, and 1.2 kg·kg-1, during their freezing at -20 °C, and during subsequent thawing at 20 °C.

Effects of Averaging the Heat-Transfer Coefficient on the Predicted Material Temperature Distribution

2015 ◽  
Author(s):  
T. I-P. Shih ◽  
C.-S. Lee ◽  
K. M. Bryden
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Transfer Coefficient ◽  
Computational Study ◽  
Maximum Temperature ◽  
Bulk Temperature ◽  
Spanwise Direction ◽  
Gas Temperature ◽  
The Heat Transfer Coefficient

The heat-transfer coefficient (HTC) in internal-coolant passages can vary appreciably about a heat-transfer enhancement feature such as a pin fin, a rib, and a concavity because of stagnation regions and wakes about the enhancement feature. However, the computed or measured HTC is often averaged spatially in the spanwise direction or over some region when used in the design of cooling strategies. Since the variation in the HTC could be a factor of eight or more about an enhancement feature, it is of interest to understand the effects of averaging the HTC on the predicted temperature distribution in the solid subjected to the heating and cooling. In this computational study, a flat plate of thickness H (1 mm) and length L = 20H is heated on one side by either a constant heat flux (68 W/cm2) or a constant HTC (1,167.2 W/m2-K) and a constant hot-gas temperature (1,482 °C). On the cooled side, the free stream or bulk temperature is kept constant (400 °C) and the average HTC (1,442.5 W/m2-K) is kept constant as well. This average HTC on the cooled side is the average of a higher HTC (hH) and a lower HTC (hL). Two types of changes from hH to hL are considered — abrupt (or step) and gradual. When the HTC changes abruptly, hH is imposed over LH, and hL is imposed over LL=L–LH. When the HTC changes gradually from hH to hL, hH is imposed from from x = 0 to LH/2, and hL is imposed from x = 3LH/2 to L with a smooth variation in the HTC to connect hH and hL. Results obtained show that when the averaged HTC is used, the maximum temperature in the plate is 900 °C on the heated side of the plate. However, if the variation in the HTC is accounted for, then the maximum temperature in the plate could be as high as 1.363 times the maximum temperature predicted by assuming an averaged HTC. Also, for the range of parameters studied, the difference in the maximum and minimum temperature in the plate can increase by a factor of 16, which strongly affects thermal stress.

scholarly journals Enhancement of Temperature Distribution and Heat Transfer Coefficient of Ribbed Tube by Simulation

2021 ◽  
Vol 7 (1) ◽  
pp. 21-28
Author(s):  
Rahul Kunar ◽  
Dr Sukul Lomash
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Flow Analysis ◽  
Total Heat ◽  
Total Heat Transfer ◽  
The Heat Transfer Coefficient

The heat transfer from surface may in general be enhanced by increasing the heat transfer coefficient between a surface and its surrounding or by increasing heat transfer area of the surface or by both. The main objective of the study and calculate the total heat transfer coefficient. Improve the heat transfer rate by using ANSYS CFD. During the CFD calculations of the flow in internally ribbed tubes. And calculated the temperature distribution and pressure inside the tube by using ansys. The model was created using CatiaV5 and meshed with Ansys, and the flow analysis is done with Ansys 19.2. The results showing that the heat transfer is increased. The enthalpy and temperature increase with flow is advancing when compare with normal boiler tube. In this study the total heat transfer rate of the pipe increase with the increase the rib height. Total heat transfer rate increase up to 7.7kw. The study show that the improvement in furnace heat transfer can be achieved by changing the internal rib design.

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