scholarly journals Effects of Different Surface Heat Transfer Coefficients on Predicted Heating and Cooling Loads towards Sustainable Building Design

Buildings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 609
Author(s):  
Yanwen Wu ◽  
Wenna Jian ◽  
Liu Yang ◽  
Tengyue Zhang ◽  
Yan Liu
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Energy Consumption ◽  
Building Design ◽  
Building Energy ◽  
Surface Heat ◽  
Outdoor Environment ◽  
Transfer Coefficients ◽  
Surface Heat Transfer ◽  
Heat Transfer Coefficients

The transfer of surface heat between a building and the outdoor environment is the energy transfer channel and it is important for the energy efficiency of buildings. Early stage building design is a critical stage and it can directly determine the energy consumption by a building. Therefore, selecting appropriate surface heat transfer coefficients (SHTCs) is a key issue in building energy consumption prediction. In this study, EnergyPlus was employed to investigate the building load in Chinese cities with different SHTCs: (1) constant SHTCs based on national standards; and (2) dynamically changing SHTCs based on the Thermal Analysis Research Program (TARP). Based on investigations of the hourly load, daily cumulative load in a typical day, and annual cumulative load with different SHTCs, corrections for the annual cumulative load were obtained according to the relative deviations between the results produced with the TARP model and traditional SHTCs. The greatest relative deviations were 67.5% and 25.3% for the building shape factor φ = 0.49 and 0.29 in Lhasa. The relative deviations were 13.3% and 12.0% for φ = 0.49 in Xi’an and Beijing, respectively. Corrections were not essential for other conditions because the relative deviations were lower than 5.0%. Considering the current characteristics of engineering calculations and the need to obtain more accurate design results, dynamically changing SHTCs should be applied. These correction factors can obtain more accurate results for the current building energy efficiency system with traditional SHTCs.

Effect of Uneven Wall Temperature on Local Heat Transfer in a Rotating Square Channel With Smooth Walls and Radial Outward Flow

1992 ◽  
Vol 114 (4) ◽  
pp. 850-858 ◽  
Author(s):  
J.-C. Han ◽  
Y. M. Zhang
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Surface Heat ◽  
Transfer Coefficients ◽  
Surface Heat Transfer ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
Rotation Numbers

The influence of uneven wall temperature on the local heat transfer coefficient in a rotating square channel with smooth walls and radial outward flow was investigated for Reynolds numbers from 2500 to 25,000 and rotation numbers from 0 to 0.352. The square channel, composed of six isolated copper sections, has a length-to-hydraulic diameter ratio of 12. The mean rotating radius to the channel hydraulic diameter ratio is kept at a constant value of 30. Three cases of thermal boundary conditions were studied: (A) four walls uniform temperature, (B) four walls uniform heat flux, and (C) leading and trailing walls hot and two side walls cold. The results show that the heat transfer coefficients on the leading surface are much lower than that of the trailing surface due to rotation. For case A of four walls uniform temperature, the leading surface heat transfer coefficient decreases and then increases with increasing rotation numbers, and the trailing surface heat transfer coefficient increases monotonically with rotation numbers. The decreased (or increased) heat transfer coefficients on the leading (or trailing) surface are due to the cross-stream and centrifugal buoyancy-induced flows from rotations. However, the trailing surface heat transfer coefficients, as well as those for the side walls, for case B are higher than for case A and the leading surface heat transfer coefficients for cases B and C are significantly higher than for case A. The results suggest that the local uneven wall temperature creates the local buoyancy forces, which change the effect of the rotation. Therefore, the local heat transfer coefficients on the leading, trailing, and side surfaces are altered by the uneven wall temperature.

Influence of Inlet Mass Flow Rate on Heat Transfer of Supercritical Liquefied Natural Gas in Horizontal Tubes

2014 ◽  
Vol 960-961 ◽  
pp. 433-437 ◽  
Author(s):  
Hai Yu Meng ◽  
Shu Zhong Wang ◽  
Lu Zhou ◽  
Zhi Qiang Wu ◽  
Jun Zhao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Surface Heat ◽  
Bulk Temperature ◽  
Transfer Coefficients ◽  
Surface Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

The submerged combustion vaporizer (SCV) is a new kind of vaporizer for liquefied natural gas (LNG). In this paper, a numerical study has been carried out to investigate the heat transfer characteristics of supercritical LNG in horizontal tubes. The thermo-physical properties of supercritical LNG were used for this study, and the influence of inlet LNG mass flow rate on heat transfer was investigated. Numerical results showed that the LNG flow in horizontal tubes included two stages. In the first stage, the surface heat transfer coefficients increased significantly with the increase of the fluid bulk temperature and reached a maximum value when the fluid bulk temperature equaled the pseudo-critical point . After the maximum, the surface heat transfer coefficients fell rapidly with the increase of the fluid bulk temperature. With increasing the inlet LNG mass flow rate, the surface heat transfer coefficients increased due to the increased fluid velocity in horizontal tubes.

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