scholarly journals Simulation of heat transfer at the junction of the attic floor to the building envelope

2020 ◽  
Vol 35 ◽  
pp. 26-33
Author(s):  
G. Ratushnyak ◽  
O. Horiun ◽  
A. Lialiukk
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Thermal Resistance ◽  
Heat Loss ◽  
Residential Buildings ◽  
Building Envelope ◽  
Junction Point ◽  
Transfer Coefficients ◽  
Linear Heat ◽  
Junction Points

Numerous studies and thermal imaging inspection of multi-storey residential buildings indicate characteristic places with increased heat loss. In houses built in accordance with modern domestic regulatory requirements for the thermal resistance of enclosing structures, the actual thermal resistance of walls and windows coincides with the standard. However, nodes of elements of external enclosing structures with increased values of heat loss were found. Insulation of the junction points allows increasing the thermal resistance of the external enclosing structures. In order to increase the energy efficiency of a building, the design of the insulation of the junction of the ceiling in the technical attic has been proposed, which is protected by a patent for a useful model. The linear heat transfer coefficients of the junction point of the ceiling in the attic are analyzed. It was revealed that such information was not indicated in the regulatory documents. Reducing heat loss is achieved by arranging additional layers of insulation in the form of aerogel slabs at the junction of the ceiling to the external enclosing structures. The analysis of the energy efficiency of the proposed design of the junction unit of the attic floor as a "cold bridge" was carried out according to the results of mathematical modeling in the DAMWERK software package. Based on the simulation results, the temperature distribution in the junction of the ceiling in the technical attic was established. The linear heat transfer coefficient of the recommended junction point of the ceiling in the technical attic has been determined, the value of which should be taken into account when developing the Energy Efficiency section. The results obtained confirm the feasibility of introducing the proposed structural design of the floor abutment unit in the technical attic, which will improve the energy efficiency of the building's thermal insulation envelope.

Experimental Investigation of Heat Transfer in Impingement Air Cooled Plate Fin Heat Sinks

2005 ◽  
Vol 128 (4) ◽  
pp. 412-418 ◽  
Author(s):  
Zhipeng Duan ◽  
Y. S. Muzychka
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Transfer Model ◽  
Heat Sinks ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Developing Flow ◽  
Rectangular Channels

Impingement cooling of plate fin heat sinks is examined. Experimental measurements of thermal performance were performed with four heat sinks of various impingement inlet widths, fin spacings, fin heights, and airflow velocities. The percent uncertainty in the measured thermal resistance was a maximum of 2.6% in the validation tests. Using a simple thermal resistance model based on developing laminar flow in rectangular channels, the actual mean heat transfer coefficients are obtained in order to develop a simple heat transfer model for the impingement plate fin heat sink system. The experimental results are combined into a dimensionless correlation for channel average Nusselt number Nu∼f(L*,Pr). We use a dimensionless thermal developing flow length, L*=(L∕2)∕(DhRePr), as the independent parameter. Results show that Nu∼1∕L*, similar to developing flow in parallel channels. The heat transfer model covers the practical operating range of most heat sinks, 0.01<L*<0.18. The accuracy of the heat transfer model was found to be within 11% of the experimental data taken on four heat sinks and other experimental data from the published literature at channel Reynolds numbers less than 1200. The proposed heat transfer model may be used to predict the thermal performance of impingement air cooled plate fin heat sinks for design purposes.

PERFORMANCE INDICATORS FOR ENERGY EFFICIENCY RETROFITTING IN MULTIFAMILY RESIDENTIAL BUILDINGS

2019 ◽  
Vol 14 (2) ◽  
pp. 109-136
Author(s):  
Chaitali Basu ◽  
Virendra Kumar Paul ◽  
M.G. Matt Syal
Keyword(s):  
Energy Efficiency ◽  
Performance Assessment ◽  
Performance Indicators ◽  
Residential Buildings ◽  
Building Energy ◽  
Energy Performance ◽  
Building Envelope ◽  
Assessment Process ◽  
Second Phase ◽  
A Priority

The energy performance of an existing building is the amount of energy consumed to meet various needs associated with the standardized use of a building and is reflected in one or more indicators known as Building Energy Performance Indicators (EnPIs). These indicators are distributed amongst six main factors influencing energy consumption: climate, building envelope, building services and energy systems, building operation and maintenance, occupants' activities and behaviour, and indoor environmental quality. Any improvement made to either the existing structure or the physical and operational upgrade of a building system that enhances energy performance is considered an energy efficiency retrofit. The main goal of this research is to support the implementation of multifamily residential building energy retrofits through expert knowledge consensus on EnPIs for energy efficiency retrofit planning. The research methodology consists of a comprehensive literature review which has identified 35 EnPIs for assessing performance of existing residential buildings, followed by a ranking questionnaire survey of experts in the built-environment to arrive at a priority listing of indicators based on mean rank. This was followed by concordance analysis and measure of standard deviation. A total of 280 experts were contacted globally for the survey, and 106 completed responses were received resulting in a 37.85% response rate. The respondents were divided into two groups for analysis: academician/researchers and industry practitioners. The primary outcome of the research is a priority listing of EnPIs based on the quantitative data from the knowledge-base of experts from these two groups. It is the outcome of their perceptions of retrofitting factors and corresponding indicators. A retrofit strategy consists of five phases for retrofitting planning in which the second phase comprises an energy audit and performance assessment and diagnostics. This research substantiates the performance assessment process through the identification of EnPIs.

scholarly journals Evaluation of the Summer Overheating Phenomenon in Reinforced Concrete and Cross Laminated Timber Residential Buildings in the Cold and Severe Cold Regions of China

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6305
Author(s):  
Haibo Guo ◽  
Lu Huang ◽  
Wenjie Song ◽  
Xinyue Wang ◽  
Hongnan Wang ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Reinforced Concrete ◽  
Building Materials ◽  
Residential Buildings ◽  
Building Envelope ◽  
Thermal Design ◽  
Cold Regions ◽  
Cross Laminated Timber ◽  
Design Standard

As the climate changed in recent years, an increase in summer indoor temperatures in severe cold and cold regions of China has started to affect thermal comfort. However, the local design standard for energy efficiency does not recognize this phenomenon. This paper reports the potential overheating phenomenon in residential buildings and examines the rationale for the current thermal designs adopted in severe cold and cold regions of China. In this study, the two most commonly used building materials, reinforced concrete (RC) and cross laminated timber (CLT), are used separately in the design of an 18-story residential building envelope located in six different cities in the severe cold and cold regions. The energy consumption and indoor operative temperatures during the operation of these buildings are simulated using Integrated Environmental Solutions Virtual Environment (IES VE). The results demonstrate that both the RC and the CLT buildings experience varying degrees of overheating in any climate subregion. The CLT buildings have longer overheating hours compared to the RC buildings, especially in the cold regions. The results also indicate that for apartments on higher stories, the cooling energy consumption and indoor temperature also increase gradually. The research results suggest that the local design standard for energy efficiency needs to be adjusted by adding thermal design methods for summer to reduce the periods of overheating.

Numerical Simulation Study of Impinging Jet Impact Fin Surface on Heat Transfer Characteristics

2013 ◽  
Vol 663 ◽  
pp. 586-591 ◽  
Author(s):  
Li Ming Zhou ◽  
Lei Zhu ◽  
Jing Quan Zhao ◽  
Meng Zheng
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Thermal Resistance ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Transfer Characteristics ◽  
Jet Impact ◽  
Jet Array

Three-dimensional numerical simulation was implemented to analyze the heat transfer characteristics for jet impingement impact fin surface. 60 calculation cases were simulated to investigate the effects of different fin surfaces on heat transfer characteristics, and 12 jet array impingement cases were calculated for comparison. The results shown that the fin shape, the height and the fin arrangement were the critical factors to affect the jet impingement and the best combination were existed in a certain range. The thermal resistance of cylinder fin arranged in order was34.7 percent higher than that of cylinder fin arranged staggered. The thermal resistance of square fin arranged in order was38.9 percent higher than that of square fin arranged staggered .The heat transfer coefficients of impinging jet impact fin surface were better than that of jet array impingement. The fitting correlations on heat transfer of impinging jet impact fin surface were given.

scholarly journals Prediction of the impact of climate change on the thermal performance of walls and roof in Morocco

2021 ◽  
Author(s):  
Yassine Kharbouch ◽  
Mohamed Ameur
Keyword(s):  
Climate Change ◽  
Heat Transfer ◽  
Heat Loss ◽  
Thermal Performance ◽  
Building Energy ◽  
Building Envelope ◽  
Heat Gain ◽  
Impact Of Climate Change ◽  
Summer Heat ◽  
The Impact

Abstract Climate change has become a real challenge in different fields, including the building sector. Understanding and assessing the impact of climate change on building energy performance is still necessary to elaborate new climate-adaptive design measures for future buildings. The building energy consumption for heating and cooling is mainly related to the building envelope thermal performance. In this study, the winter heat loss and summer heat gain indicators are proposed to assess and analyse the potential impact of climate change on opaque building envelope elements for different climate zones in Morocco over the next 40 years. For that purpose, a one-dimensional heat transfer model is used to simulate the heat transfer through the multi-layer structure of the wall/roof. A medium climate change scenario is considered in this study. The results showed that the current average walls and roof summer heat gain is expected to increase of about 19.2–54.3% by the 2060s depending on the climate zone, versus a less important decrease in winter heat loss varies between –10.6 and –20.6%. This paper provides a reliable evaluation of the climate change impact on building envelope thermal performance, which leads to better adjustments in future building envelope designs.

scholarly journals Additional heat loss of jamb in enclosing structures

2021 ◽  
Vol 263 ◽  
pp. 03017
Author(s):  
Maria Samsonova ◽  
Elvira Semenova ◽  
Christina Kotova ◽  
Leonid Salogub
Keyword(s):  
Heat Flux ◽  
Energy Efficiency ◽  
Heat Loss ◽  
Energy Efficient ◽  
Residential Buildings ◽  
Temperature Fields ◽  
Design Stage ◽  
Design Solution ◽  
Additional Heat ◽  
Aerated Concrete

One of the urgent problems today is to increase the energy efficiency of civil buildings. There is a need at the design stage to choose structures and design solutions that will compensate for the increasing consumption of energy resources in civil engineering. This article compares different building envelopes used in the construction of residential buildings: a volumetric block and a wall made of aerated concrete blocks. To determine the most energy efficient design solution construction is compared in different climatic regions. One of the most vulnerable places of a wall, from the point of view of energy efficiency, is a window jamb. In this article, an analysis is carried out to determine the construction with the lowest heat loss window jambs. Using the ELCUT software temperature fields and additional heat flux densities are calculated. According to the calculation, the proportion of heat loss due to window slope from heat loss according to the surface of the structure was determined. The heat flux density of the homogeneous section of the wall of the volume block is 1.28 times higher on average than in the aerated concrete wall. Regardless of the climatic conditions, the junction of the window jamb in buildings made of insulated panels of volumetric blocks is more energy efficient than the same junction in a building with aerated concrete walls.

scholarly journals Finnish design ventilation rates for residential buildings

2019 ◽  
Vol 111 ◽  
pp. 02016 ◽  
Author(s):  
Jorma Säteri ◽  
Olli Seppänen ◽  
Mervi Ahola
Keyword(s):  
Energy Efficiency ◽  
Residential Buildings ◽  
Design Guidelines ◽  
Building Envelope ◽  
Building Regulations ◽  
Zero Energy Building ◽  
Guideline Values ◽  
Ventilation Rates ◽  
New Buildings

Implementation of EU directives has forced EU member countries to revise the building regulations related energy efficiency. The 2017 revision of the building codes is due to the requirement set in the EPBD 2010 for all new buildings to be nearly zero buildings by 2020. The Finnish Ministry of the Environment (in charge of building regulations) invited FINVAC Federation of Finnish HVAC Associations to revise the guidelines values of ventilation rates as part of the nearly zero energy building regulations. At the same time, the Finnish Society of Indoor Air Quality and Climate updated its voluntary Classification of Indoor Environment. Several methods were used in the study to collect information and develop the new guideline values. European studies, such as HEALTHVENT, and relevant CEN standards were taken into consideration in drafting the design ventilation rates. Existing legislation on housing conditions gave the minimum levels and, finally, the recommended values were defined using expert interviews, workshops and public review process. Earlier studies had indicated that earlier design ventilation rates were too high for small apartments. Ventilation rates were considered too low for homes of elderly people and residential kitchen hoods, and some larger apartments. Furthermore, the balance of outdoor and exhaust air flows needed revision due to the improved tightness of the building envelope. Energy efficiency and avoidance of draught and noise were also taken into account. This paper presents the numeric values of the ventilation rates in the new building regulations and the design guidelines supporting them.

scholarly journals To the determination of heat exchange conditions near the inner surface of walls with reflective thermal insulation from aluminium foil

2018 ◽  
Vol 196 ◽  
pp. 02035 ◽  
Author(s):  
Nina Umnyakova ◽  
Mikhail Gandzhuntsev
Keyword(s):  
Heat Transfer ◽  
Thermal Insulation ◽  
Experimental Studies ◽  
Building Envelope ◽  
Surface Radiation ◽  
Thermal Engineering ◽  
Transfer Coefficients ◽  
Concrete Wall ◽  
Heat Transfer Coefficients ◽  
Inner Surface

Materials with a low coefficient of surface radiation intensively reflect the radiant component of the heat flux and reduce heat losses through the building envelope. When designing building structures with reflective thermal insulation it is necessary to evaluate the efficiency of its application. However, at present there are no methods for calculating the value of thermal losses through external walls in the presence of reflective thermal insulation on internal surface of the wall, as well as there are no data on the values of heat transfer coefficients at the inner surface of building envelope with reflective thermal insulation. In this regard, in the climatic chambers of NIISF RAABS, complex thermal engineering studies were carried out. For this a cellular concrete wall 2,8 x1,2 m was put up into the chamber with reflective thermal insulation on the inner surface and without it. The obtained results of experimental studies, presented in the work, allowed obtaining numerical values of heat transfer coefficients at the inner surface of walls with reflective thermal insulation, and use the obtained data in further calculations.

Study on Energy-Saving Renovation of Existing Heating Masonry-Concrete Residential Buildings

2011 ◽  
Vol 280 ◽  
pp. 147-151 ◽  
Author(s):  
Hong Guo ◽  
Min Fang Su ◽  
Xiao Jun Jin
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Energy Saving ◽  
Thermal Environment ◽  
Residential Buildings ◽  
Residential Building ◽  
Building Envelope ◽  
Indoor Thermal Environment ◽  
Consumption Situation ◽  
Current Energy

Based on the current energy consumption situation of existing masonry-concrete residential buildings in China, it discussed the main energy-saving renovation policies and technologies. Taking existing masonry-concrete residential building of Taiyuan city as a case, it analyzed its heat loss situations, energy-saving renovation design and reconstruction technologies of building envelope. It discussed energy-saving renovation effects. Energy efficiency and indoor thermal environment improved significantly after energy-saving renovation. The building life is extended.

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