scholarly journals Mechanical and Thermal Performance Characterisation of Compressed Earth Blocks

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2978 ◽  
Author(s):  
Elisabete R. Teixeira ◽  
Gilberto Machado ◽  
Adilson de P. Junior ◽  
Christiane Guarnier ◽  
Jorge Fernandes ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Compressive Strength ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Water Absorption ◽  
Thermal Performance ◽  
Pulse Velocity ◽  
Building Envelope ◽  
Compressed Earth Blocks ◽  
Earth Blocks

The present research is focused on an experimental investigation to evaluate the mechanical, durability, and thermal performance of compressed earth blocks (CEBs) produced in Portugal. CEBs were analysed in terms of electrical resistivity, ultrasonic pulse velocity, compressive strength, total water absorption, water absorption by capillarity, accelerated erosion test, and thermal transmittance evaluated in a guarded hotbox setup apparatus. Overall, the results showed that compressed earth blocks presented good mechanical and durability properties. Still, they had some issues in terms of porosity due to the particle size distribution of soil used for their production. The compressive strength value obtained was 9 MPa, which is considerably higher than the minimum requirements for compressed earth blocks. Moreover, they presented a heat transfer coefficient of 2.66 W/(m2·K). This heat transfer coefficient means that this type of masonry unit cannot be used in the building envelope without an additional thermal insulation layer but shows that they are suitable to be used in partition walls. Although CEBs have promising characteristics when compared to conventional bricks, results also showed that their proprieties could even be improved if optimisation of the soil mixture is implemented.

Thermal Analysis and Design Applications of the Spiral Groove Tubes in Condensers

2014 ◽  
Vol 1070-1072 ◽  
pp. 1705-1708
Author(s):  
Xiao Lu Wang ◽  
Da Yu Huang
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Tube Bundle ◽  
Spiral Groove ◽  
Analysis And Design ◽  
Grooved Tube ◽  
The Heat Transfer Coefficient

In this paper, condensation mechanism of the Freon refrigerants outside spiral grooved tube is discussed. The heat transfer coefficient of Freon refrigerants condensation outside spiral grooved tube is obtained. A calculation example of heat transfer coefficient on the tube bundle of condenser with baffle bars is presented. It shows the excellent thermal performance of the spiral groove tubes compared to smooth tubes.

scholarly journals Influence of airtightness of steel sandwich panel joints on heat losses

2020 ◽  
Vol 172 ◽  
pp. 05008
Author(s):  
Markus Kuhnhenne ◽  
Vitali Reger ◽  
Dominik Pyschny ◽  
Bernd Döring
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Building Envelope ◽  
The Finite Element Method ◽  
Transmission Losses ◽  
Building Envelopes ◽  
Metal Building ◽  
Effective Heat Transfer Coefficient ◽  
The Heat Transfer Coefficient

Energy saving ordinances requires that buildings must be designed in such a way that the heat transfer surface including the joints is permanently air impermeable. The prefabricated roof and wall panels in lightweight steel constructions are airtight in the area of the steel covering layers. The sealing of the panel joints contributes to fulfil the comprehensive requirements for an airtight building envelope. To improve the airtightness of steel sandwich panels, additional sealing tapes can be installed in the panel joint. The influence of these sealing tapes was evaluated by measurements carried out by the RWTH Aachen University - Sustainable Metal Building Envelopes. Different installation situations were evaluated by carrying out airtightness tests for different joint distances. In addition, the influence on the heat transfer coefficient was also evaluated using the Finite Element Method (FEM). The combination of obtained air volume flow and transmission losses enables to create an "effective heat transfer coefficient" due to transmission and infiltration. This summarizes both effects in one value and is particularly helpful for approximate calculations on energy efficiency.

An Experimental Investigation of the Rib Surface-Averaged Heat Transfer Coefficient in a Rib-Roughened Square Passage

1997 ◽  
Vol 119 (2) ◽  
pp. 381-389 ◽  
Author(s):  
M. E. Taslim ◽  
C. M. Wadsworth
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Blockage Ratio ◽  
Transfer Coefficients ◽  
Height Ratio ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
The Heat Transfer Coefficient

Turbine blade cooling, a common practice in modern aircraft engines, is accomplished, among other methods, by passing the cooling air through an often serpentine passage in the core of the blade. Furthermore, to enhance the heat transfer coefficient, these passages are roughened with rib-shaped turbulence promoters (turbulators). Considerable data are available on the heat transfer coefficient on the passage surface between the ribs. However, the heat transfer coefficients on the surface of the ribs themselves have not been investigated to the same extent. In small aircraft engines with small cooling passages and relatively large ribs, the rib surfaces comprise a large portion of the passage heat transfer area. Therefore, an accurate account of the heat transfer coefficient on the rib surfaces is critical in the overall design of the blade cooling system. The objective of this experimental investigation was to conduct a series of 13 tests to measure the rib surface-averaged heat transfer coefficient, hrib, in a square duct roughened with staggered 90 deg ribs. To investigate the effects that blockage ratio, e/Dh and pitch-to-height ratio, S/e, have on hrib and passage friction factor, three rib geometries corresponding to blockage ratios of 0.133, 0.167, and 0.25 were tested for pitch-to-height ratios of 5, 7, 8.5, and 10. Comparisons were made between the rib average heat transfer coefficient and that on the wall surface between two ribs, hfloor, reported previously. Heat transfer coefficients of the upstream-most rib and that of a typical rib located in the middle of the rib-roughened region of the passage wall were also compared. It is concluded that: 1 The rib average heat transfer coefficient is much higher than that for the area between the ribs; 2 similar to the heat transfer coefficient on the surface between the ribs, the average rib heat transfer coefficient increases with the blockage ratio; 3 a pitch-to-height ratios of 8.5 consistently produced the highest rib average heat transfer coefficients amongst all tested; 4 under otherwise identical conditions, ribs in upstream-most position produced lower heat transfer coefficients than the midchannel positions, 5 the upstream-most rib average heat transfer coefficients decreased with the blockage ratio; and 6 thermal performance decreased with increased blockage ratio. While a pitch-to-height ratio of 8.5 and 10 had the highest thermal performance for the smallest rib geometry, thermal performance of high blockage ribs did not change significantly with the pitch-to-height ratio.

Rib Heat Transfer Coefficient Measurements in a Rib-Roughened Square Passage

1998 ◽  
Vol 120 (2) ◽  
pp. 376-385 ◽  
Author(s):  
G. J. Korotky ◽  
M. E. Taslim
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Blockage Ratio ◽  
Average Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Height Ratio ◽  
Average Heat ◽  
Heat Transfer Coefficients

Three staggered 90 deg rib geometries corresponding to blockage ratios of 0.133, 0.167, and 0.25 were tested for pitch-to-height ratios of 5, 8.5, and 10, and for two distinct thermal boundary conditions of heated and unheated channel walls. Comparisons were made between the surface-averaged heat transfer coefficients and friction factors for ribs with rounded corners and those with sharp corners, reported previously. Heat transfer coefficients of the furthest upstream rib and that of a typical rib located in the middle of the rib-roughened region of the passage wall were also compared. It was concluded that: (a) For the geometries tested, the rib average heat transfer coefficient was much higher than that for the area between the ribs. For the sharp-corner ribs, the rib average heat transfer coefficient increased with blockage ratio. However, when the corners were rounded, the trend depended on the level of roundness. (b) High-blockage-ratio (e/Dh = 0.25) ribs were insensitive to the pitch-to-height ratio. For the other two blockage ratios, the pitch-to-height ratio of 5 produced the lowest heat transfer coefficient. Results of the other two pitch-to-height ratios were very close, with the results of S/e = 10 slightly higher than those of S/e = 8.5. (c) Under otherwise identical conditions, ribs in the furthest upstream position produced lower heat transfer coefficients for all cases except that of the smallest blockage ratio with S/e of 5. In that position, for the rib geometries tested, while the sharp-corner rib average heat transfer coefficients increased with the blockage ratio, the trend of the round-corner ribs depended on the level of roundness, r/e. (d) Thermal performance decreased with the blockage ratio. While the smallest rib geometry at a pitch-to-height ratio of 10 had the highest thermal performance, thermal performance of high blockage ribs at a pitch-to-height ratio of 5 was the lowest. (e) The general effects of rounding were a decrease in heat transfer coefficient for the midstream ribs and an increase in heat transfer coefficient for ribs in the furthest upstream position.

Overall Thermal Performance of a Rectangular Channel With an Array of Elongated Pedestals

2013 ◽  
Author(s):  
S. Huang ◽  
Y. Y. Yan ◽  
J. D. Maltson ◽  
E. Utriainen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Rectangular Channel ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Flow Area ◽  
Coefficient Distribution

Experiments have been conducted to investigate the overall thermal performance of a rectangular channel implemented with an elongated pedestal array. The staggered pedestals were elongated in the spanwise direction in order that the jet flow from between the pedestals impinges at the centre of the pedestals in the downstream row. The average heat transfer coefficient of the pedestal and the local heat transfer coefficient distribution of the bottom channel wall were investigated for different geometrical arrangements. The pressure drop across the pedestal bank was measured. The transient liquid crystal method was used to obtain the local heat transfer coefficient distribution on the bottom channel wall and the lumped capacitance method was used to measure the average heat transfer coefficient of the pedestals in the last two rows of the bank. Five pressure taps were arranged on the centerline of each gap between two pedestal rows to measure the pressure drop. The heat transfer coefficients were measured over the Reynolds number range from 10,000 to 30,000. The minimum flow area to the channel cross-section flow area ratio ranged from 0.149 to 0.333. The effects of pedestal geometry and array distribution were investigated in detail showing the relationship between the pedestal array geometry, heat transfer enhancement and pressure drop. Conclusions were drawn on the effects of geometry and flow conditions on overall thermal performance of the respective channels.

Thermal Performance Enhancement of an Industrial Shell and Tube Heat Exchanger

2015 ◽  
Author(s):  
Fadi A. Ghaith ◽  
Ahmed S. Izhar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Numerical Study ◽  
Thermal Design ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Shell And Tube

This paper aims to enhance the thermal performance of an industrial shell-and-tube heat exchanger utilized for the purpose of cooling raw natural gas by means of mixture of Sales gas. The main objective of this work is to provide an optimum and reliable thermal design of a single-shelled finned tubes heat exchanger to replace the existing two- shell and tube heat exchanger due to the space limitations in the plant. A comprehensive thermal model was developed using the effectiveness-NTU method. The shell-side and tube-side overall heat transfer coefficient were determined using Bell-Delaware method and Dittus-Boelter correlation, respectively. The obtained results showed that the required area to provide a thermal duty of 1.4 MW is about 1132 m2 with tube-side and shell-side heat transfer coefficients of 950 W/m2K and 495 W/m2K, respectively. In order to verify the obtained results generated from the mathematical model, a numerical study was carried out using HTRI software which showed a good match in terms of the heat transfer area and the tube-side heat transfer coefficient.

scholarly journals Thermal performance prediction of heat pipe with TiO2 nanofluids using RSM

2021 ◽  
pp. 199-199
Author(s):  
Lakshmi Reddy ◽  
Srinivasa Bayyapureddy Reddy ◽  
Kakumani Govindarajulu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Tilt Angle ◽  
Heat Load ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Heat pipe is a two phase heat transfer device with high effective thermal conductivity and transfer huge amount of heat with minimum temperature gradient in between evaporator and condenser section. This paper objective is to predict the thermal performance in terms of thermal resistance (R) and heat transfer coefficient (h) of screen mesh wick heat pipe with DI water-TiO2 as working fluid. The input process parameters of heat pipe such as heat load (Q), tilt angle (?) and concentration of nanofluid (?) were modeled and optimized by utilizing Response Surface Methodology (RSM) with MiniTab-17 software to attain minimum thermal resistance and maximum heat transfer coefficient. The minimum thermal resistance of 0.1764 0C/W and maximum heat transfer coefficient of 1411.52 W/m2 0C was obtained under the optimized conditions of 200 W heat load, 57.20 tilt angle and 0.159 vol. % concentration of nano-fluid.

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