Simplified Procedure for Prediction of Asphalt Pavement Subsurface Temperatures Based on Heat Transfer Theories

1997 ◽  
Vol 1568 (1) ◽  
pp. 114-123 ◽  
Author(s):  
Lisheng Shao ◽  
Sun Woo Park ◽  
Y. Richard Kim
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Air Temperature ◽  
Asphalt Pavement ◽  
Prediction Method ◽  
Point Of View ◽  
Temperature History ◽  
Climatic Regions ◽  
Simplified Procedure ◽  
Subsurface Temperatures

Surface deflection measurements and backcalculation of layer moduli in flexible pavements are significantly affected by the temperature of the asphalt concrete (AC) layer. Correction of deflections or backcalculated moduli to a reference temperature requires determination of an effective temperature of the AC layer. For routine deflection testing and analysis in state highway agencies, it is preferable, from a practical point of view, to use a nondestructive prediction method for determining the effective AC layer temperature instead of measuring the temperature directly from a small hole drilled into the AC layer. A simplified procedure to predict asphalt pavement subsurface temperatures is presented. The procedure is based on fundamental principles of heat transfer and uses the surface temperature history since yesterday morning to predict the AC layer mid-depth temperature at the time of falling weight deflectometer (FWD) testing today. The surface temperature history is determined using yesterday’s maximum air temperature and cloud condition, the minimum air temperature of today’s morning, and surface temperatures measured during FWD tests. FWD tests and temperature measurements have been conducted on seven pavement sections with varying structural designs located in three different climatic regions of North Carolina. The field temperature records from these pavements have provided values of pavement thermal parameters and coefficients in temperature functions that are needed in the prediction procedure. A set of verification results are presented using examples with different climatic regions, changing AC layer thicknesses, and varying weather patterns in different seasons.

Experimental Modeling of Air Temperature and Velocity Distribution in an Engine Compartment

2006 ◽  
Author(s):  
A. A. Mozafari ◽  
M. H. Saidi ◽  
J. Neyestani ◽  
A. E. Sany
Keyword(s):  
Heat Transfer ◽  
Velocity Distribution ◽  
Air Temperature ◽  
Gasoline Engine ◽  
Point Of View ◽  
Vehicle Body ◽  
Air Distribution ◽  
Wind Effect ◽  
Engine Compartment ◽  
Air Velocity

Investigation of air distribution and wind effect on a vehicle body from the point of view of underhood heat transfer effect and proper positioning of vehicle elements such cooler, condenser and engine configuration is an important area for engine researchers and manufacturers as well. In this research, the effect of air velocity distribution and wind effect around a vehicle is simulated and temperature and velocity distribution around engine block which is influenced by the wind effect is investigated. Thermal investigation of the engine compartment components is performed using results of underhood air temperature and velocity distribution. The heat transfer from engine surface is calculated from the engine energy balance in which their input data are obtained from a comprehensive experimental study on a four cylinder gasoline engine.

Determination of Time-Resolved Heat Transfer Coefficient and Adiabatic Effectiveness Waveforms With Unsteady Film Cooling

2012 ◽  
Author(s):  
James L. Rutledge ◽  
Jonathan F. McCall
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Random Noise ◽  
Temperature History ◽  
Flow Conditions ◽  
Adiabatic Effectiveness

Traditional hot gas path film cooling characterization involves the use of wind tunnel models to measure the spatial adiabatic effectiveness (η) and heat transfer coefficient (h) distributions. Periodic unsteadiness in the flow, however, causes fluctuations in both η and h. In this paper we present a novel inverse heat transfer methodology that may be used to approximate the η(t) and h(t) waveforms. The technique is a modification of the traditional transient heat transfer technique that, with steady flow conditions only, allows the determination of η and h from a single experiment by measuring the surface temperature history as the material changes temperature after sudden immersion in the flow. However, unlike the traditional transient technique, this new algorithm contains no assumption of steadiness in the formulation of the governing differential equations for heat transfer into a semi-infinite slab. The technique was tested by devising arbitrary waveforms for η and h at a point on a film cooled surface and running a computational simulation of an actual experimental model experiencing those flow conditions. The surface temperature history was corrupted with random noise to simulate actual surface temperature measurements and then fed into an algorithm developed here that successfully and consistently approximated the η(t) and h(t) waveforms.

Reduction Effects of Urban Heat Island by Water-Retentive Pavement

2012 ◽  
Vol 724 ◽  
pp. 147-150 ◽  
Author(s):  
Ree Ho Kim ◽  
Jong Bin Park ◽  
Jung Soo Mun ◽  
Jung Hun Lee
Keyword(s):  
Surface Temperature ◽  
Urban Heat Island ◽  
Air Temperature ◽  
Asphalt Pavement ◽  
Sensible Heat Flux ◽  
Heat Island ◽  
Sensible Heat ◽  
Summer Period ◽  
Island Effect ◽  
Urban Heat

Recently, increasing of impervious surface as concrete or asphalt pavement with urban development brought increasing of air temperature in city. So many researchers have explored ways to reduce the urban heat island effect and water-retentive or water absorbing pavements have been found to be very effective. In this study, to evaluate the reduction effects of urban heat reduction of water-retentive pavement, surface temperature of pavement, air temperature, wind speed and albedo were measured for 3 years (2008~2010, summer period). And the intensity of sensible heat flux was calculated to estimate a influence on air temperature. Experimental results indicated that water-retentive was effective to reduction of air temperature by decreasing of surface temperature of pavement compare to other pavements. This is showed that water-retentive pavement can be contributed to mitigation of urban heat island.

scholarly journals DETERMINING HEAT TRANSMISSION RESISTANCE OF ENCLOSING STRUCTURES

2018 ◽  
Vol 61 (1) ◽  
pp. 47-59 ◽  
Author(s):  
B. M. Khroustalev ◽  
V. D. Sizov
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Thermal Resistance ◽  
Surface Temperature ◽  
Rate Of Change ◽  
Temperature History ◽  
Transfer Coefficients ◽  
Thermophysical Characteristics ◽  
Time Intervals ◽  
Relative Temperature

Fulfillment of the activities aimed to an increase of the thermal resistance of enclosing structures requires the determination of their thermophysical characteristics with the use of the determination method based on the solution of problems of heat conduction, establishing the con- nection between the spatial and temporal temperature changes under the effect of heat source. This work uses the solution of the problem under nonstationary heating of the enclosing structure in the form of unrestricted plate with boundary conditions of the III kind. According to the known relations and graphs alterations in surface temperature depending on warm-up time, on thermal resistance of constructions and on arguments of Fo and Bi, i. e. initial and boundary conditions are determined. The graphic dependencies that have been obtained show that the surface temperature depends on the thermal resistance, while the temperature at the opposite surface during heat expo- sure remains practically unchanged during t = 5 h. Thus, if the outside air temperature is altered, then the rate of change of surface temperature or relative temperature q make it possible to deter- mine the thermophysical characteristics by solving the inverse problem of thermal conductivity with the use of the converted ratio to determine R as a function R = f(q, t). If the constructed graphic dependencies R = f(q, t) are used at different heat transfer coefficients, then according to the measured temperatures at different time intervals it is possible to determine thermal resistance in the same time intervals and, according to their average value, determine the required resistance to heat transfer R. The estimated ratio of analytical and graphic dependencies that we have obtained demonstrate the adequacy of the conducted full-scale measurements, if the areas with homogeneous temperature field and temperature history are chosen, and they can be used in determining the heat resistance of the enclosing structure in the form of unrestricted plate with boundary conditions of the III kind.

Heat transfer from starlings sturnus vulgaris during flight

1999 ◽  
Vol 202 (12) ◽  
pp. 1589-1602 ◽  
Author(s):  
S. Ward ◽  
J.M.V. Rayner ◽  
U. Möller ◽  
D.M. Jackson ◽  
W. Nachtigall ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Convective Heat Transfer ◽  
Heat Loss ◽  
Convective Heat ◽  
Air Temperature ◽  
Sturnus Vulgaris ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Infrared thermography was used to measure heat transfer by radiation and the surface temperature of starlings (Sturnus vulgaris) (N=4) flying in a wind tunnel at 6–14 m s-1 and at 15–25 degrees C. Heat transfer by forced convection was calculated from bird surface temperature and biophysical modelling of convective heat transfer coefficients. The legs, head and ventral brachial areas (under the wings) were the hottest parts of the bird (mean values 6.8, 6.0 and 5.3 degrees C, respectively, above air temperature). Thermal gradients between the bird surface and the air decreased at higher air temperatures or during slow flight. The legs were trailed in the air stream during slow flight and when air temperature was high; this could increase heat transfer from the legs from 1 to 12 % of heat transfer by convection, radiation and evaporation (overall heat loss). Overall heat loss at a flight speed of 10.2 m s-1 averaged 11. 3 W, of which radiation accounted for 8 % and convection for 81 %. Convection from the ventral brachial areas was the most important route of heat transfer (19 % of overall heat loss). Of the overall heat loss, 55 % occurred by convection and radiation from the wings, although the primaries and secondaries were the coolest parts of the bird (2.2-2.5 degrees C above air temperature). Calculated heat transfer from flying starlings was most sensitive to accurate measurement of air temperature and convective heat transfer coefficients.

The Application of Thin Film Gauges on Flexible Plastic Substrates to the Gas Turbine Situation

1995 ◽  
Author(s):  
S. M. Guo ◽  
M. C. Spencer ◽  
G. D. Lock ◽  
T. V. Jones ◽  
N. W. Harvey
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Surface Temperature ◽  
Guide Vane ◽  
Single Layer ◽  
Temperature History ◽  
Plastic Substrates ◽  
Free Stream Turbulence ◽  
Thermal Boundary Conditions ◽  
Nozzle Guide

Thin film heat transfer gauges have been instrumented onto flexible plastic substrates which can be adhesively bonded to plastic or metal models. These new gauges employ standard analysis techniques to yield the heat flux to the model surface and have significant advantages over gauges fired onto machinable glass or those used with metal models coated with enamel. The main advantage is that the construction of the gauges is predictable and uniform, and thus calibration for thickness and geometric properties is not required. The new gauges have been used to measure the heat transfer to an annular turbine nozzle guide vane in the Oxford University Cold Heat Transfer Tunnel. Engine-representative Mach and Reynolds numbers were employed and the free-stream turbulence intensity at NGV inlet was 13%. The vanes were either precooled or preheated to create a range of different thermal boundary conditions. The gauges were mounted on both perspex and aluminium NGVs and the heat transfer coefficient was obtained from the surface temperature history using either a single layer analysis (for perspex) or double layer (for aluminium) analysis. The surface temperature and heat transfer levels were also measured using rough and polished liquid crystals under similar conditions. The measurements have been compared with computational predictions.

Uncertainties on HTC Measurement of Water Spray Quenching of Aluminum Alloys

2011 ◽  
Author(s):  
S. Bikass ◽  
B. Andersson ◽  
A. Pilipenko
Keyword(s):  
Heat Transfer ◽  
Computer Simulation ◽  
Surface Temperature ◽  
High Strength ◽  
Sample Surface ◽  
Temperature History ◽  
Water Spray ◽  
Uncertainty Sources ◽  
Transfer Equations ◽  
Accuracy And Repeatability

Water spray cooling of profiles right after extrusion is critical for control over the mechanical properties of high strength alloys. To design the optimum distribution of spray, computer simulation is a powerful tool. For that purpose a quantification of the heat-transfer boundary conditions is challenging, especially as the heat transfer coefficient (HTC) changes with the surface temperature. It is possible to record temperature history during the quenching in laboratory/plant experiments and then HTC values can be calculated by means of inverse modeling. These values are applicable only if they are accurate enough. In this paper, it is assumed the maximum allowed tolerance for calculated HTC to be 5%. This work is based on the computer simulation of the real experiments with thermocouples installed inside the sample to estimate the heat flux at the surface of the sample as well as the sample surface temperature using heat transfer equations. Error sources are typically: inaccurate thermocouple positioning and contact quality, sample geometry, thermocouple accuracy and repeatability, thermal properties, initial temperature and etc. In this study, some of these errors and uncertainty sources are selected and their impact on calculated HTC values is investigated. Finally, maximum allowance for every parameter to achieve calculated HTC within ±5% is calculated. Since HTC is not constant but a curve vs. temperature, the calculated HTC values must be between two parallel curves which represent +5% and −5% of nominal HTC.

An Inverse Analysis Method for Estimation of Heat Flux and Temperature-Dependence of Heat Transfer Coefficient

2011 ◽  
Author(s):  
Shiro Kubo ◽  
Seiji Ioka
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Inverse Method ◽  
Thermal Stresses ◽  
Temperature History ◽  
Inner Surface ◽  
History Of ◽  
Transient Thermal ◽  
The Relationship ◽  
Inverse Analysis Method

Transient thermal stresses develop in pipes during start-up and shut-down. In previous papers the present authors [1–4] proposed an inverse method for determining the optimum thermal inlet liquid temperature history which reduced the maximum transient thermal stress in pipes. The papers considered multiphysics including heat conduction, heat transfer, and elastic deformation. The inverse method used the relationship between inner surface temperature history, transient temperature distribution and transient thermal stresses. The coefficient of heat transfer plays an important role in the evaluation of thermal stress. In this study an inverse method was developed for estimating heat flux and temperature-dependence of the coefficient of heat transfer from the history of the outer surface temperature and the liquid temperature. The method used the relationship between the outer surface temperature and the inner surface temperature. For the regularization of solution the function expansion method was applied in expressing the history of flux on the inner surface. Numerical simulations demonstrated the usefulness of the proposed inverse analysis method. By examining the effect of measurement errors of temperature on the estimation, the robustness of the method was shown.

Determination of Time Resolved Heat Transfer Coefficient and Adiabatic Effectiveness Waveforms With Unsteady Film

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
James L. Rutledge ◽  
Jonathan F. McCall
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Random Noise ◽  
Computational Simulation ◽  
Temperature History ◽  
Flow Conditions ◽  
Adiabatic Effectiveness

Traditional hot gas path film cooling characterization involves the use of wind tunnel models to measure the spatial adiabatic effectiveness (η) and heat transfer coefficient (h) distributions. Periodic unsteadiness in the flow, however, causes fluctuations in both η and h. In this paper we present a novel inverse heat transfer methodology that may be used to approximate the η(t) and h(t) waveforms. The technique is a modification of the traditional transient heat transfer technique that, with steady flow conditions only, allows the determination of η and h from a single experiment by measuring the surface temperature history as the material changes temperature after sudden immersion in the flow. However, unlike the traditional transient technique, this new algorithm contains no assumption of steadiness in the formulation of the governing differential equations for heat transfer into a semi-infinite slab. The technique was tested by devising arbitrary waveforms for η and h at a point on a film cooled surface and running a computational simulation of an actual experimental model experiencing those flow conditions. The surface temperature history was corrupted with random noise to simulate actual surface temperature measurements and then fed into an algorithm developed here that successfully and consistently approximated the η(t) and h(t) waveforms.

scholarly journals Introduction to the Dynamics of Heat Transfer in Buildings

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6469
Author(s):  
Bożena Babiarz ◽  
Władysław Szymański
Keyword(s):  
Heat Transfer ◽  
Air Temperature ◽  
Thermal Inertia ◽  
Weather Conditions ◽  
Climatic Conditions ◽  
Point Of View ◽  
Thermal Dynamics ◽  
Annual Cycles ◽  
Gains And Losses ◽  
Over Time

Changing climatic conditions cause the variability of the parameters of the building’s surroundings, which in turn causes both the gains and losses of heat to change over time. There is variability in both daily and annual cycles. Meeting the requirements of thermal comfort in rooms requires maintaining the required parameters, including constant temperature. Heat gains and losses must be balanced, and this balance is ensured through appropriate heating systems. At the same time, the above means that the demand for heating buildings is not constant but depends on external weather conditions and the energy efficiency of the building. This, in turn, affects the thermal inertia, causing changes in the partition temperature to occur slower than the changes in air temperature. Therefore, the amplitude of the heating power changes is not proportional to the amplitude of the outside air temperature change. The paper presents an example of the analysis of thermal dynamics in buildings. Various aspects of heat transfer in the building were investigated taking into account the transient conditions. The variability of temperature over time at different depths of the partition was analysed, showing the results graphically. The periodic variability of the outside air temperature and the intensity of solar radiation were described by the Fourier series. Moreover, the article shows the influence of the thermal insulation thickness of the external wall on the annual amplitude of temperature changes and on the duration of the heating season, which is important from the point of view of optimization.

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