Engineering Methods of Estimating the Effect of the Surroundings on the Building Envelope: Control of the Heat Transfer through the Building Envelope (Arrangement of the Thermal Resistances within a Structure Consisting of Solid Wall Elements)

2015 ◽  
pp. 206-277
Keyword(s):  
Heat Transfer ◽  
Solid Wall ◽  
Building Envelope

Full 3D Conjugate Heat Transfer Simulation and Heat Transfer Coefficient Prediction for the Effusion-Cooled Wall of a Gas Turbine Combustor

2008 ◽  
Author(s):  
Andreas Jeromin ◽  
Christian Eichler ◽  
Berthold Noll ◽  
Manfred Aigner
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Gas Turbine ◽  
Conjugate Heat Transfer ◽  
Solid Wall ◽  
Heat Fluxes ◽  
Computational Domain ◽  
Transfer Coefficients ◽  
Wall Functions ◽  
Numerical Predictions

Numerical predictions of conjugate heat transfer on an effusion cooled flat plate were performed and compared to detailed experimental data. The commercial package CFX® is used as flow solver. The effusion holes in the referenced experiment had an inclination angle of 17 degrees and were distributed in a staggered array of 7 rows. The geometry and boundary conditions in the experiments were derived from modern gas turbine combustors. The computational domain contains a plenum chamber for coolant supply, a solid wall and the main flow duct. Conjugate heat transfer conditions are applied in order to couple the heat fluxes between the fluid region and the solid wall. The fluid domain contains 2.4 million nodes, the solid domain 300,000 nodes. Turbulence modeling is provided by the SST turbulence model which allows the resolution of the laminar sublayer without wall functions. The numerical predictions of velocity and temperature distributions at certain locations show significant differences to the experimental data in velocity and temperature profiles. It is assumed that this behavior is due to inappropriate modeling of turbulence especially in the effusion hole. Nonetheless, the numerically predicted heat transfer coefficients are in good agreement with the experimental data at low blowing ratios.

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.

Effects of Interfacial Interactions Between Fluid and Solid Wall on Microscale Flows

2006 ◽  
Author(s):  
Xingang Liang
Keyword(s):  
Heat Transfer ◽  
Solid Wall ◽  
Mean Free Path ◽  
Characteristic Size ◽  
Interfacial Interactions ◽  
Interfacial Effects ◽  
Flow And Heat Transfer ◽  
Microscale Flow ◽  
Flow Phenomena ◽  
Microscale Flows

This work discusses the interfacial effects on flow and heat transfer at micro/nano scale. Different from bulk cases where interfaces can be simply treated as a boundary, the interfacial effects are not limited to the interface at microscale but extend into a significant, even the whole domain of the flow and heat transfer field when the characteristic size of the domain is close to the mean free path (MFP) of fluid particles. Most of microscale flow phenomena result from interfacial interactions. Any changes in the interactions between the fluid and solid wall particles could affect the flow and heat transfer characteristics, such as flow and temperature profiles, friction coefficient. The interactions depend on many parameters, such as the force between fluid and solid wall particles, microstructure of interfaces. The flow and heat transfer features does not only depend on the fluid itself, but also on the interaction with the solid wall because the interface impact can go deep inside the flow. Same fluid, same channel shape but different wall materials could have different flow characters.

An Overview of Artificial Intelligence-Based Methods for Building Energy Systems

2003 ◽  
Vol 125 (3) ◽  
pp. 331-342 ◽  
Author(s):  
Moncef Krarti
Keyword(s):  
Heat Transfer ◽  
Artificial Intelligence ◽  
Neural Networks ◽  
Energy Use ◽  
Energy Systems ◽  
Building Energy ◽  
Building Envelope ◽  
Building Energy Systems ◽  
Intelligence Approach ◽  
Artificial Intelligence Approach

An overview of commonly used methodologies based on the artificial intelligence approach is provided with a special emphasis on neural networks, fuzzy logic, and genetic algorithms. A description of selected applications to building energy systems of AI approaches is outlined. In particular, methods using the artificial intelligence approach for the following applications are discussed: Prediction energy use for one building or a set of buildings (served by one utility), Modeling of building envelope heat transfer, Controlling central plants in buildings, and Fault detection and diagnostics for building energy systems.

Experimental Investigation on the Electrokinetic Motions of Colloidal Particles at an Interfacial Boundary Between Solid and Liquid

2019 ◽  
Author(s):  
Katsuaki Shirai ◽  
Shoichiro Kaji ◽  
Shigeo Hosokawa ◽  
Tsuyoshi Kawanami ◽  
Shigeki Hirasawa
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Electric Fields ◽  
Spatial Resolution ◽  
Measurement System ◽  
Colloidal Particles ◽  
Solid Wall ◽  
Wall Region ◽  
And Performance ◽  
Solid Liquid

Abstract We investigate electrokinetic behavior of colloidal particles in the vicinity of a solid-liquid interface. Colloidal liquids are expected to be used as thermal transport media for heat transfer applications such as nanofluids and phase change emulsions. They contain submicrometer-sized particles in liquid, and electrokinetic behavior of the solute particles should play an important role in the heat transfer between solid-liquid interfacing boundaries. However, experimental investigation of the behavior remains difficult due to the required spatial resolution beyond diffraction limit. We developed a measurement system based on laser Doppler principle using an interference of evanescent waves generated at total internal reflections of incident lasers at a solid wall. The system was developed for the measurement of velocities of colloidal particles at an interfacing boundary of colloidal liquid and a solid wall. The system has a unique advantage of a high spatial resolution in the direction perpendicular to the boundary due to the short penetration depth of an evanescent wave in the range of a few hundred nanometers. The principle and performance of the measurement system were investigated using a scanning probe in the measurement volume. We experimentally confirmed the validity of the measurement and characterized the uncertainty of velocity measurement. The system was further applied in a series of measurements of alumina particles dispersed in water in a square-shaped cell under induced electric fields. The measured velocities are proportional to the field strengths at different particle concentrations. The linear relationship is consistent with theoretical predictions, which demonstrates the feasibility of the system for the measurement of velocities of colloidal particles in the near wall region.

Three-Dimensional Fluid Flow and Coupled Heat Transfer in Simplified Bipolar Plates

2007 ◽  
Author(s):  
Jianfei Wu ◽  
Jianhu Nie ◽  
Yitung Chen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Solid Wall ◽  
Three Dimensional ◽  
Cathode Side ◽  
Uniform Heat Flux ◽  
Bipolar Plates ◽  
Coupled Heat Transfer ◽  
Temperature Distributions

Numerical simulations were performed for three-dimensional fluid flow and coupled heat transfer in simplified bipolar plates. The Reynolds number of inlet flow is varied from 100 to 900 on the anode side while the Reynolds number is maintained as a constant of 100 on the cathode side. The solid wall surfaces of the bipolar plates are assumed to be adiabatically insulated, except that the active areas of the channels are supplied with uniform heat flux. Results of velocity and temperature distributions for different Reynolds numbers are presented and discussed. It is shown that effects of flow pattern on temperature distributions in channels becomes negligible when the Reynolds number is as high as 900.

scholarly journals Analysis of the temperature distribution in the place of fixing the ventilated facade

2019 ◽  
Vol 97 ◽  
pp. 01041
Author(s):  
Adam Ujma ◽  
Marta Pomada
Keyword(s):  
Heat Transfer ◽  
Thermal Conditions ◽  
Building Envelope ◽  
Heat Demand ◽  
Thermal Bridges ◽  
Ventilated Facade ◽  
The Impact ◽  
New Buildings ◽  
The Heat Balance ◽  
Very High

Designers more and more often choose facade systems with ventilated layers for external walls, especially in the case of new buildings. They are also used to modernize existing buildings. Mechanical connectors are a characteristic element of these constructions. Often, they are ignored in calculating the heat balance of rooms and the entire building. Because they pierce the thermal insulation layer they cause point thermal bridges. The influence of thermal point bridges, usually made of aluminum, i.e. a material with very high thermal conductivity, for heat transfer turns out to be significant. Such thermal bridges significantly increase heat losses through building partitions. This situation increases the heat demand in the rooms to compensate for the heat loss. The article presents the results of the analysis of the impact of mechanical fasteners in ventilated facade systems on heat transfer in the building envelope. The influence of various materials and constructional solutions on the thermal conditions in these walls was investigated.

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.

scholarly journals The rising damp in two traditional clay-brick masonry walls and influence on heat transfer performance

2019 ◽  
Vol 282 ◽  
pp. 02097 ◽  
Author(s):  
Zhenyi Kong ◽  
Yonghui Li ◽  
Shuichi Hokoi ◽  
Shi Hu
Keyword(s):  
Heat Transfer ◽  
Solid Wall ◽  
Cavity Wall ◽  
Wall Structure ◽  
Capillary Water ◽  
Historical Building ◽  
Water Rise ◽  
Heating Load ◽  
Wall Foundation ◽  
The Heat Transfer Coefficient

This paper studies the law of capillary water rise in the brick solid wall and the brick cavity wall under the influence of high-humidity wall foundation. It is found that the rising height of the capillary water sharp front is proportional to the time to the 0.5 power, but the coefficient is related to the wall structure, and the speed in cavity wall is higher than that in the solid wall. The heat flow meter method was used to compare the influence of the capillary water to the heat transfer when it rises to different heights. It is found that the presence of capillary water has a direct impact on the heat transfer coefficient of the wall. The presence of capillary water may increase the heating load by 11.1% and the cooling load by 15% of a common historical building in hot summer and cold winter area of China.

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