scholarly journals The Influence of Window-Wall Ratio on Heating Energy Consumption of Rural House in Severe Cold Regions of China

2020 ◽  
Vol 173 ◽  
pp. 03008
Author(s):  
Teng Shao ◽  
Hong Jin ◽  
Wuxing Zheng ◽  
Jin Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Energy Consumption ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Outdoor Environment ◽  
Shape Coefficient ◽  
Heating Energy Consumption ◽  
The Heat Transfer Coefficient ◽  
Large Shape

Rural houses in severe cold areas of China are mostly single-storey independent buildings with large shape coefficient. Compared with urban residential, it has larger contact area between envelope and outdoor environment of each household. Meanwhile, the heat transfer coefficient of window is usually greater than that of external wall and roof. The window-wall ratio is one of the important indicators affecting the energy consumption of rural house. This paper takes window-wall ratio as the main variable, building orientation, thermal performance of envelope and window heat transfer coefficient as the auxiliary variables, and applies DesignBuilder software to quantitatively analyse the mechanism of window-wall ratio on rural house’s heating energy consumption under the interactive influence of multiple factors. Results show that the influence rule of window-wall ratio with different orientations on heating energy consumption will change when the thermal performance of envelope or window heat transfer coefficient changed. The synthetic effect of various factors should be considered in the design to reasonably determine the windowwall ratio of rural house.

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.

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.

Performance Experimental Study and Energy Consumption Calculation of Hollow Glass Window Film

2011 ◽  
Vol 250-253 ◽  
pp. 356-359
Author(s):  
Dan Ping Yang ◽  
Jia Peng He ◽  
Zheng Song Zhang
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Energy Consumption ◽  
Transfer Coefficient ◽  
Window Glass ◽  
Hollow Glass ◽  
Window Film ◽  
The Heat Transfer Coefficient ◽  
Energy Consumption Calculation

This paper taked hollow glass window as the model, and heat transfer coefficient, sunshading coefficient and energy consumption of the window glass were obtained in the situations of window glass with and without low-E film by doing experiment and theoretical calculation. The results show that both heat transfer coefficient and sunshading coefficient decrease comparing the hollow glass window film with no film. For the fixed and push-pull window of the whole window, the heat transfer coefficient decrease by 24.2% and 28.9% respectively and sunshade coefficient decreases by 31.37%. And the low-E film by this study adopting reduces energy consumption of the summer greatly by 32.96%, and has no too large effect on winter heating, so the annual energy consumption reduces and the window film saves annual energy consumption 14.62% .

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

1994 ◽  
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 thirteen tests to measure the rib surface-averaged heat transfer coefficient, in a square duct roughened with staggered 90° 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, hflor, 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 mid-channel 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.

scholarly journals Tip gap size effects on thermal performance of cavity-winglet tips in transonic turbine cascade with endwall motion

2017 ◽  
Vol 1 ◽  
pp. CR5JBC ◽  
Author(s):  
Fangpan Zhong ◽  
Chao Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Tip Clearance ◽  
Pressure Side ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
High Heat Transfer ◽  
The Heat Transfer Coefficient

AbstractThe thermal performance of two cavity-winglet tips with endwall motion is investigated in a transonic high pressure turbine cascade, which operates at an engine representative exit Mach number of 1.2 and an exit Reynolds number of 1.7 × 106. The numerical method is first validated with experimental data and then used to investigate blade heat transfer at three different tip clearances of 1.1, 2.1 and 3.1% chord. The effects of relative endwall motion are considered. The present results show that as the size of the tip gap increases, the heat transfer coefficient and heat load on the tip increases. The winglet geometries on the blade tip mainly affect the tip flow structure close to them. At a larger tip clearance, the size of the separation bubble above the pressure side winglet increases. The heat transfer coefficient is high on the pressure side winglet due to the flow reattachment at all tip clearances. Within the tip gap, when the size of the tip clearance increases, the size of the cavity vortex increases and the cavity scraping vortex due to relative endwall motion becomes smaller. The impingement of the both two vortexes can lead to high heat transfer coefficient on the cavity floor surface. On the blade suction surface, when the size of the tip clearance increases, the heat transfer coefficient of the cavity tip increases, but those of the winglet tips decreases. The heat transfer coefficient is high on the side surface of the suction side winglet at all tip clearances because of the tip leakage flow impingement.

scholarly journals Experimental Estimation of the Heat Transfer Coefficient of an Unglazed Solar Plate for Unsteady Humid Outdoor Condition

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Felix Uba ◽  
Eric Osei Essandoh ◽  
Gilbert Ayine Akolgo ◽  
Richard Opoku ◽  
Lawrence Oppong-Kyereh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Mild Steel ◽  
Transfer Coefficient ◽  
Specific Heat ◽  
Steel Plate ◽  
Outdoor Environment ◽  
Empirical Equations ◽  
Outdoor Condition ◽  
The Heat Transfer Coefficient

This research presents a study on the heat transfer coefficient for an unglazed solar plate collector in an unsteady humid outdoor environment. The purpose for undertaking this research is to investigate the correlation between the heat transfer coefficient and air speed and also verify whether heat transfer from unglazed solar thermal collectors under outdoor conditions can be experimentally determined using a particular mathematical relationship for different locations. In estimating the heat transfer coefficient for an unglazed solar plate in an unsteady humid outdoor condition, an experiment was held using an outdoor setup that measured temperatures, wind speeds, and solar radiations from 11:00 A.M. to 2:00 P.M. The solar plate collector was placed on a flat bed of height 2.2 m and a collection area of 0743 m2. An average temperature of 45°C was recorded for a mild steel plate collector which was initially exposed to an ambient temperature which ranges from 25°C to 32°C. The interfacial temperature between the plate and an asbestos board ranges from 42°C to 52°C, and that of the asbestos and a plywood is 40°C to 46°C. The specific heat capacity of the mild steel plate and the asbestos board used for the construction of the experimental setup are 25.00 kJ/kg and 950.00 kJ/kg, respectively, while the thermal conductivity of these materials is 0.46 W/m·K and 0.25 W/m·K, respectively. The novelty of this work is the use of such a study to generate empirical equations for Ghana and to produce representative equations for determining the heat transfer coefficient for solar plate collectors in unsteady humid outdoor conditions in West Africa. This work is expected to contribute data alongside similar works done for different areas to help propose empirical equations for estimating global and not site-specific heat transfer coefficients.

CFD Study of the Thermal Performance Improvement of a Counter-Flow Heat Exchanger Using Enhanced Surface Tubes

2021 ◽  
Author(s):  
Humberto Santos ◽  
Wei Li ◽  
David Kukulka
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Working Fluid ◽  
Operational Parameters ◽  
Ansys Fluent ◽  
Flow Heat ◽  
The Heat Transfer Coefficient

Abstract A CFD investigation was carried out to compare the thermal performance of the 1EHT-1 and 1EHT-2 tubes with a smooth surface tube using R410A at 311K as working fluid. These tubes have enhanced heat transfer area generated by a series of dimples/protrusions and petals distributed over its surface. All the stages of this simulation were conducted using Ansys Fluent. Initially, the physical model of the fluid domain was developed using the Design Modeler module, with an internal tube diameter of 8.32mm, and then imported to the meshing module for the griding process. To ensure accuracy in the results, the mesh average orthogonal quality was kept above 0.7, with the minimum orthogonal quality higher than 0.1. For the numerical simulation, SST k-omega model was used, with Reynolds number ranging from 16000 to 35000. The results of the heat transfer coefficient were validated based on previous experimental work. As expected, at the lowest Reynolds number tested, the heat transfer coefficient for the 1EHT-1 tube was 1097.5 W.K−1.m−2, followed by 1058 W.K−1.m−2 for the 1EHT-2 and nearly 846 W.K−1.m−2 for the smooth tube. When compared with the experimental results, a good agreement was observed, and the HTC relative error (RE) for all tubes tested was below 10%. It is possible to conclude that the CFD model used here presents as powerful tool to simulate and predict heat transfer with good accuracy, allowing optimization in heat exchangers design and operational parameters.

scholarly journals Winter Thermal Environment and Thermal Performance of Rural Elderly Housing in Severe Cold Regions of China

2020 ◽  
Vol 12 (11) ◽  
pp. 4543
Author(s):  
Huibo Zhang ◽  
Ya Chen ◽  
Hiroshi Yoshino ◽  
Jingchao Xie ◽  
Zhendong Mao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Thermal Environment ◽  
The Elderly ◽  
Living Room ◽  
Cold Regions ◽  
Indoor Thermal Environment ◽  
The Heat Transfer Coefficient

Understanding the thermal performance of the residential envelope is important for optimizing the indoor thermal environment. In this study, the indoor thermal environment and thermal performance of rural residences housing the elderly was determined through field measurements in Qiqihar in 2017 and 2019. The results revealed that the living room temperatures in more than 50% of homes were below the thermal neutral temperature for the elderly (17.32 °C). Moreover, the indoor thermal environment changed significantly during the day, with the predicted mean vote during the day fluctuating from 2 to 4 units. The air change rate of living rooms in 2017 and 2019 was 0.20–2.20 h−1 and 0.15–1.74 h−1, respectively. Residential ventilation times detected by an air-tightness detector ranged from 0.40–1.49 h−1. Furthermore, infrared thermography (IRT) detected air leakage in the windows of the all houses in this study, as well as thermal bridges and condensation on the exterior walls of several houses. The heat transfer coefficient of the exterior walls of all houses detected by IRT was 0.25–0.74 W/(m2·K), and a significant positive correlation was observed between the heat transfer coefficient of the south wall and the window-to-wall ratio. Finally, the heat transfer coefficient of the external walls exhibited a negative but not significant correlation with indoor temperature. This study provides detailed data and guidance for improving the indoor environment of rural houses in severe cold regions.

scholarly journals Research on Energy-Saving Design of Rural Building Wall in Qinba Mountains Based on Uniform Radiation Field

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Qin Zhao ◽  
Xiaona Fan ◽  
Qing Wang ◽  
Guochen Sang ◽  
Yiyun Zhu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Energy Consumption ◽  
Transfer Coefficient ◽  
Energy Saving ◽  
Radiation Field ◽  
Thermal Environment ◽  
Residential Buildings ◽  
South Wall ◽  
Heating Energy Consumption

How to create a healthy and comfortable indoor environment without causing a substantial increase in energy consumption has become a strategic problem that the development of all countries must face and solve. According to the climatic conditions of Qinba Mountains in China, combined with the characteristics of local rural residential buildings and residents’ living habits, the field survey and theoretical analysis were used to study the thermal environment status and the heating energy consumption condition of local rural residential buildings. The thermal design method of walls for the local rural energy-saving buildings based on the indoor uniform radiation field was explored by using the outdoor comprehensive temperature function expressed by the fourth-order harmonic Fourier series as the boundary condition of the wall thermal analysis. ANSYS CFX was adopted to study the suitability of the energy-saving wall structure designed by the above method. The results show that the indoor thermal environment of local rural residential buildings in winter is not ideal and the heating energy consumption is high, but this area has the geographical advantage to develop solar energy buildings. It is proposed that the indoor thermal comfort temperature of local rural residential buildings in winter should not be lower than 14°C. When the internal surface temperature of the external walls in different orientations are equally based on the design principle of uniform radiation field, the heat transfer coefficient of the east wall, the west wall, and the north wall of the local rural residential buildings is 1.13 times, 1.06 times, and 1.14 times of the south wall heat transfer coefficient, respectively. The energy-saving structural wall with KPI porous brick as the main material and the south wall heat transfer coefficient of 0.9 W/(m2·K) is the most suitable energy-saving wall for local rural residential buildings.

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