Circumferential Variations of Bore Heat Flux and Outside Surface Temperature for a Solar Collector Tube

1977 ◽  
Vol 99 (3) ◽  
pp. 360-366 ◽  
Author(s):  
E. M. Sparrow ◽  
R. J. Krowech
Keyword(s):  
Heat Flux ◽  
Thermal Properties ◽  
Surface Temperature ◽  
Outer Surface ◽  
Solar Collector ◽  
Heat Conduction Problem ◽  
Flow Conditions ◽  
Collector Plate ◽  
Closed Form Solutions ◽  
Large Heat

An analysis is made of the heat transfer processes in a solar collector tube subjected to large circumferential heat flux variations on its outer surface. The analysis is carried out for a collector plate configuration in which the tubes are situated in embossments in the otherwise flat surface of the plate. The solar energy absorbed by the collector plate is conducted to the tubes and gives rise to large heat flux spikes at discrete circumferential locations on the outer surface of a tube. The two-region heat conduction problem encompassing the embossed portion of the collector plate and the tube is solved by a novel procedure which provides closed form solutions of high numerical accuracy. The influence of system dimensions, thermal properties, and tube bore convection is examined by means of five dimensionless parameters, of which the Biot number was found to be the most important. The results showed that for realistic dimensions and thermal properties of the plate and tube, circumferential variations of the outside surface temperature and bore heat flux can be neglected, provided that the tube flow is laminar. For turbulent flow conditions, the variations in bore heat flux are substantially greater than for laminar flow.

Effect of a Surface Film on the Surface Temperature of a Rotating Cylinder

1986 ◽  
Vol 108 (1) ◽  
pp. 92-97 ◽  
Author(s):  
B. Gecim ◽  
W. O. Winer
Keyword(s):  
Thermal Properties ◽  
Heat Source ◽  
Film Thickness ◽  
Surface Temperature ◽  
Temperature Rise ◽  
High Speed ◽  
Integral Transform ◽  
Heat Conduction Problem ◽  
Surface Film ◽  
Layer Effect

Solution to the steady heat conduction problem of a rotating layered cylinder is presented. The governing differential equations (for the film and the substrate) are solved by using an integral transform technique. It is shown that the presence of a surface film measured in micrometers can substantially change the level of the surface temperature. The effect of the surface film on the surface temperature depends on: respective thermal properties of the film and the substrate; relative surface speed; heat source (contact) size; and surface film thickness. However, the range in which the effect of the film on the surface temperature is dependent on these parameters is limited. Outside this range (i.e., thin film/low speed or thick film/high speed) the surface temperature rise is determined by the thermal properties of the substrate, or by the properties of the film alone, respectively. Hence, outside this range, a further change in the film thickness does not influence the surface temperature rise. Dimensionless plots showing the change in surface temperature rise as a function of material thermal properties, surface speed, heat source size, and film thickness are presented. Behavior for specific material combinations are also presented. The present information can be utilized to predict the layer effect on the partition of heat between the layered cylinders.

A Study of Cooling and Heating Energy Reduction Effects for Applying of Blind-Integrated Window System in Buildings

2014 ◽  
Vol 525 ◽  
pp. 392-396
Author(s):  
Bo Hye Choi ◽  
Gyeong Seok Choi ◽  
Jae Sik Kang ◽  
Seung Yeong Song
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Outer Surface ◽  
Electricity Consumption ◽  
Building Envelope ◽  
Test Bed ◽  
Window System ◽  
Window Systems ◽  
Heating Load ◽  
Heating Energy Consumption

Recently, the window-to-wall ratio in the building envelope has gradually increased. In summer, as a result, cooling load significantly increases because of a large amount of sunlight coming through the windows. And in winter, thermal comfort can decrease at night because of heat loss and cold radiation which take place through the windows which have relatively low thermal resistance. To evaluate on characteristics of cooling and heating energy consumption under the blind-integrated window system which can fundamentally block this kind of cooling and heating load, this study has measured inner & outer surface temperature of glazing, electricity consumption and heat flux after installing the general and blind-integrated window systems in the test bed. According to the inner & outer surface temperature of glazing, the blind-integrated window system was 20.4°C while the general one was 14.4°C in summer. And in winter, the blind-integrated window system was 2.1°C while the general one was 0.8°C. Under the blind-integrated window system, in other words, electricity consumption was saved by up to 26% (about 11% daily), and heat flux decreased by approximately 34%. In addition, it's been confirmed that heater electricity consumption in winter could be saved up to 17%.

scholarly journals Verification of heat flux and temperature calculation on the control rod outer surface

2011 ◽  
Vol 32 (3) ◽  
pp. 157-173
Author(s):  
Jan Taler ◽  
Artur Cebula
Keyword(s):  
Heat Flux ◽  
Outer Surface ◽  
Nuclear Power ◽  
Heat Conduction Problem ◽  
Numerical Test ◽  
Thermal Fluctuations ◽  
Inverse Heat Conduction Problem ◽  
Control Rod ◽  
Temperature Calculation ◽  
Comparison Of The Results

Verification of heat flux and temperature calculation on the control rod outer surfaceThe paper presents heat transfer calculation results concerning a control rod of Forsmark Nuclear Power Plant (NPP). The part of the control rod, which is the object of interest, is surrounded by a mixing region of hot and cold flows and, as a consequence, is subjected to thermal fluctuations. The paper describes a numerical test which validates the method based on the solution of the inverse heat conduction problem (IHCP). The comparison of the results achieved by two methods, computational fluid dynamics (CFD) simulations and IHCP, including a description of the IHCP method used in the calculation process, shows a very good agreement between the methods.

Measurement of Surface Heat Flux and Surface Temperature in Nucleate Pool Boiling Using Micro-Thermocouples

2009 ◽  
Author(s):  
Wei Liu ◽  
Kazuyuki Takase
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Temperature Change ◽  
Surface Heat Flux ◽  
Heat Conduction Problem ◽  
Pool Boiling ◽  
Surface Heat ◽  
Heat Transfer Analysis ◽  
Boiling Process

In this paper, a measurement system for surface temperature and surface heat flux was developed to study heat transfer mechanism in boiling process. The system was consisted by two parts: (1) inner block temperatures were measured using micro-thermocouples set at two layers inside heating block; (2) with using the measured temperatures, inverse heat transfer analysis was performed to get surface heat flux and surface temperature. For the inner block temperature measurement, special T-type micro thermocouples with a common positive pole were developed. Totally 20 thermocouples were set at two layers at the depths 3.1μm and 4.905mm beneath the boiling surface, in a radius of 5mm. The developed system was used to research the change of surface heat flux and surface temperature in a boiling process. Experiments were performed to pool boiling at atmospheric pressure. The experiments showed the developed special T-type micro thermocouples could trace temperature change in boiling process successfully. With comparison to images from a high-speed camera, temperature change tendencies in boiling process were tried to understand. Then one dimensional inverse heat conduction problem was solved to get surface heat flux and surface temperature. Increase in surface heat flux with the generation of big bubble was derived successfully.

scholarly journals The transient response for different types of erodable surface thermocouples using finite element analysis

2007 ◽  
Vol 11 (4) ◽  
pp. 49-64 ◽  
Author(s):  
Hussein Mohammed ◽  
Hanim Salleh ◽  
Mohd Yusoff
Keyword(s):  
Finite Element Analysis ◽  
Heat Flux ◽  
Thermal Properties ◽  
Surface Temperature ◽  
Transient Response ◽  
Temperature History ◽  
Two Dimensional ◽  
Flux Variation ◽  
Element Analysis ◽  
Different Types

The transient response of erodable surface thermocouples has been numerically assessed by using a two dimensional finite element analysis. Four types of base metal erodable surface thermocouples have been examined in this study, included type-K (alumel-chromel), type-E (chromel-constantan), type-T (copper-constantan), and type-J (iron-constantan) with 50 mm thick- ness for each. The practical importance of these types of thermocouples is to be used in internal combustion engine studies and aerodynamics experiments. The step heat flux was applied at the surface of the thermocouple model. The heat flux from the measurements of the surface temperature can be commonly identified by assuming that the heat transfer within these devices is one-dimensional. The surface temperature histories at different positions along the thermocouple are presented. The normalized surface temperature histories at the center of the thermocouple for different types at different response time are also depicted. The thermocouple response to different heat flux variations were considered by using a square heat flux with 2 ms width, a sinusoidal surface heat flux variation width 10 ms period and repeated heat flux variation with 2 ms width. The present results demonstrate that the two dimensional transient heat conduction effects have a significant influence on the surface temperature history measurements made with these devices. It was observed that the surface temperature history and the transient response for thermocouple type-E are higher than that for other types due to the thermal properties of this thermocouple. It was concluded that the thermal properties of the surrounding material do have an impact, but the properties of the thermocouple and the insulation materials also make an important contribution to the net response.

Estimation of Surface Temperature and Heat Flux Using Inverse Solution for One-Dimensional Heat Conduction

2003 ◽  
Vol 125 (2) ◽  
pp. 213-223 ◽  
Author(s):  
Masanori Monde ◽  
Hirofumi Arima ◽  
Yuhichi Mitsutake
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Power Series ◽  
Surface Temperature ◽  
Heat Conduction Problem ◽  
Time Lag ◽  
Inverse Heat Conduction Problem ◽  
Inverse Solution ◽  
Initial Temperature Distribution ◽  
Laplace Transform Technique

An analytical method has been developed for the inverse heat conduction problem using the Laplace transform technique when the temperatures are known at two positions within a finite body. On the basis of these known temperatures, a closed form to the inverse solution can be obtained to predict surface conditions. The method first approximates the measured temperatures with a half polynomial power series of time as well as a time lag, which takes for a monitor to sense the temperature change at the point. The expressions for the surface temperature and the surface heat flux are explicitly obtained in the form of the power series of time. The surface temperature and heat flux calculated for some representative problems show agreement with the known values. The method can be applied to the case where an initial temperature distribution exists.

Determination of Surface Heating Condition for a Desired Thermal Growth Environment in an Industry-Size Hydrothermal Autoclave

2003 ◽  
Author(s):  
Hongmin Li ◽  
Edward A. Evans ◽  
G.-X. Wang
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Outer Surface ◽  
Heat Conduction Problem ◽  
Power Input ◽  
Inverse Heat Conduction Problem ◽  
Insulation Layer ◽  
Growth Environment ◽  
Inner Surface ◽  
Metal Wall

Hydrothermal growth is the most common technique to grow piezoelectric single crystals such as quartz. Due to a high-temperature and high-pressure growth condition, hydrothermal autoclaves are designed to operate as a closed system. During operation, the only control mechanism that crystal growers have is adjusting the power input of the heaters, based on the temperature readings obtained by the thermocouples along the centerline inside the autoclaves. The power adjusting process, however, is purely experience dependent, and, normally, uniform heating conditions from electric heaters are employed along the autoclave wall. This study develops an inverse algorithm, with which the required heat flux distributions from the heaters can be obtained for a desired growth environment inside an autoclave. The algorithm involves solving three sub-models step by step. The first step is to solve a two-dimensional axisymmetric model of solution in the autoclave to obtain the temperature and heat flux on the solution/wall interface. Using these temperature and heat flux conditions as thermal boundary conditions, the second step solves an inverse heat conduction problem in the metal wall. The solution provides the heat flux and temperature on the outer surface of the metal wall. The final step is to solve a heat conduction problem in the insulation layer to obtain the heat flux on the inner surface of the insulation layer. The heat flux distributions for heaters are then determined by the heat flux on the outer surface of the metal wall and heat flux on the inner surface of the insulation layer. The paper describes the details of each model. As an example, the method is used to find the required heat flux distributions of heaters for the growth environment predicted by a 2-D isothermal wall model. The result is then used to develop a two-patch heater for industry autoclaves.

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