scholarly journals Thermal Conductivity of Building Materials in Iraq

2021 ◽  
Vol 28 (4) ◽  
pp. 37-49
Author(s):  
Madgeed A. Al-Doury ◽  
Atif Ali Hasan ◽  
Raheem Kadhim Mohammed ◽  
Riyadh H. Al-Jawad

Thermophysical Properties of Building Materials are Considered to have high importance in predicting building thermal performance, calculating thermal loads inside building, and optimizing the use of a building and insulating materials. Due to the lack of measurements of local building materials properties, designers and air- conditioning engineers have no choice but to use the published foreign data, which probably leads to inaccurate predictions of thermal loads and may give a false thermal performance. At the same time, it leads to an over-designed capacity of air- conditioning systems that lead to increased energy consumption in the building. Thus, it is clear that it was important to conduct this research to evaluate the thermal conductivity and thermal resistance of Iraqi building materials. The number of the local building materials were listed, and specimens were collected from their sites, factories, and suppliers such as bricks, stones, concrete products, gypsum, etc. Those samples were dimensioned to the specific size required when a measurement was conducted by the Hot Wire method. All measurements were carried out at room temperature. The relationship between thermal conductivity, density, moisture content, and pressure for a number of materials was Studied. A comparison between the measurements of the Iraqi building materials and results published in the ASHRAE, CIBS Guide, Australian Specifications, and Jordanian Specifications was made. However, the availability of such data is important for the climatic design of buildings, thermal load calculations for air- conditioning, and choosing the insulating materials.

2013 ◽  
Vol 779-780 ◽  
pp. 1419-1422 ◽  
Author(s):  
Lin Lu ◽  
Li Jiang ◽  
Qing Feng ◽  
He Ping Wang

Agricultural residues from straw are widely used for energy and other applications. The thermal conductivity is one of the most important thermophysical properties considered when using agricultural residues, such as rice straw, in renewable energy engineering. In this paper, the thermal conductivity of rice straw was measured using a thermal probe by the transient hot wire method at selected moisture contents, temperatures and dry densities. The moisture contents of the samples ranged from 0 to 21.47 percent wet basis and the dry densities ranged from 90.7 to 136.4 kg/m3 and the temperature ranged from 0 to 170°C. Under those conditions, the thermal conductivity was measured and analyzed. Experiment results showed that the thermal conductivity increases with the increases of the density, moisture content and temperature, and the relationship among them is approximately described in a linear way. A new model to predict the thermal conductivity of agricultural residues from straw was proposed. The calculated results by the proposed model are in good agreement with the experimental data.


Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1199 ◽  
Author(s):  
Marie Viel ◽  
Florence Collet ◽  
Sylvie Prétot ◽  
Christophe Lanos

In order to meet the requirement of sustainable development, building materials are increasingly environmentally friendly. They can be partially or fully bio-based or recycled. This paper looks at the development of fully bio-based composites where agro-resources are valued as bio-based aggregates (hemp) and as binding materials (wheat). In a previous work, a feasibility study simultaneously investigated the processing and ratio of wheat straw required to ensure a gluing effect. In this paper, three kinds of hemp-straw composites are selected and compared with a hemp-polysaccharides composite. The gluing effect is analyzed chemically and via SEM. The developed composites were characterized multi-physically. They showed sufficiently high mechanical properties to be used as insulating materials. Furthermore, they showed good thermal performances with a low thermal conductivity (67.9–69.0 mW/(m · K) at 23 ° C, dry).


2019 ◽  
pp. 49-53
Author(s):  
Євген Іванович Трушляков ◽  
Микола Іванович Радченко ◽  
Андрій Миколайович Радченко ◽  
Сергій Георгійович Фордуй ◽  
Сергій Анатолійович Кантор ◽  
...  

Maintaining the operation of refrigeration compressors in nominal or close modes by selecting a rational design thermal load and distributing it in response to the behavior of the current thermal load according to the current climatic conditions is one of the promising reserves for improving the energy efficiency of air conditioning systems, which implementation ensures maximum or close to it in the annual cooling production according to air conditioning duties. In general case, the total range of current thermal loads of any air-conditioning system includes a range of unstable loads caused by precooling of ambient air with significant fluctuations in the cooling capacity according to current climatic conditions, and a range of relatively stable cooling capacity expended for further lowering the air temperature from a certain threshold temperature to the final outlet temperature. If a range of stable thermal load can be provided within operating a conventional compressor in a mode close to nominal, then precooling the ambient air with significant fluctuations in thermal load requires adjusting the cooling capacity by using a variable speed compressor or using the excess of heat accumulated at reduced load. Such a stage principle of cooling ensures the operation of refrigerating machines matching the behavior of current thermal loads of any air-conditioning system, whether the central air conditioning system with ambient air procession in the central air conditioner or its combination with the local indoors recirculation air conditioning systems in the air-conditioning system. in essence, as combinations of subsystems – precooling of ambient air with the regulation of cooling capacity and subsequent cooling air to the mouth of the set point temperature under relatively stable thermal load.


Author(s):  
Jianghong Wu ◽  
Shuangfeng Wang ◽  
Yunting Ge

Two type condensers of R22 residential air conditioning systems were investigated in this study. Two R22 residential air-conditioning systems, one with a microchannel condenser and the other with a round-tube condenser, were examined experimentally, while the other components of the two systems were identical except the condensers. Based on the principle of the microchannel condensation, the analysis of heat transfer along parallel heat exchanger was conducted. The non-uniform air velocity distribution at the face of the microchannel condenser and refrigerant distribution in headers were taken into account in this research. The mechanism and possibility of the superior thermal performance as compared with conventional fin-tube heat exchangers were discussed. In addition, the maximum of thermal performance influenced by the running parameter was experimentally measured. The experimental results show that with one third face area of round tube heat exchanger, microchannel condenser’s pressure drop increase around 12–23% and refrigeration output increase 2–5%, refrigerant charge decreases around 50%, it is found to be a promising candidate for residential air conditioning condenser.


2014 ◽  
Vol 716-717 ◽  
pp. 1002-1005
Author(s):  
Heng Luo ◽  
Lu Gao ◽  
Xiao Yan Ye ◽  
Tong Jing ◽  
Ning Wang ◽  
...  

Indoor air quality has become a major concern in the past three decades due to the air-tight structure design and usage of synthetic building materials. A number of measures have been presented in order to improve the indoor air conditions via ventilation and air conditioning systems. We distinguished ourselves by adopting a self-managed plant based method in which a mini-car is used to carry vegetation to places where air conditions are poor.


2014 ◽  
Vol 22 (02) ◽  
pp. 1440005 ◽  
Author(s):  
MARK SPATZ ◽  
SAMUEL YANA MOTTA ◽  
CHRISTOPHER SEETON ◽  
YONGMING NIU

Due to the growing global concerns around the use of refrigerants with relatively high global warming potential, new refrigerants with the positive attributes of both high thermal performance and low environmental impact are currently in development by Honeywell. These new refrigerants exhibit promising performance when compared with refrigerants currently used in stationary AC systems such as those that use R-410A, R-407C, and R-134a, for example. These new refrigerants also show significantly lower flammability characteristics than the much more flammable hydrocarbons. Replacements of common HFC refrigerants such as R-410A and R-407C are discussed for residential air conditioning applications. Thermal properties as well as experimental results in representative air conditioning systems are presented, showing the benefits of using these new refrigerants.


2016 ◽  
Vol 675-676 ◽  
pp. 569-572
Author(s):  
Lukáš Fiala ◽  
Monika Čáchová ◽  
Eva Vejmelková ◽  
Robert Černý

Measurements of basic materials properties of building materials with pozzolanic waste admixture originated from grinding of thermally insulating bricks were performed by means of pycnometry method. Besides, the thermal conductivity dependence on the moisture content measurements were carried out by using a non-stationary pulse method. Obtained data were subsequently analyzed by simple Wiener’s bounds and sophisticated homogenization formula taking into account the shape of ellipsoidal pore inclusions. Validity of applied homogenization models were assessed by comparison of the measured and the calculated data. On the basis of experimental data and homogenization analysis, the shape effect on the thermal conductivity is discussed.


2018 ◽  
Vol 17 (1) ◽  
pp. 149-156
Author(s):  
Viacheslav Konkov

Provision of comfortable conditions in the premises with simultaneous optimization of costs throughout the life cycle of the building was the main objective of the study. The analysis of the world engineering practice of troweling compounds with high moisture-regulating ability is performed. Information on the features of the manufacture of plasters with moisture-regulating ability is given. Usage of expanded aggregates that have the ability to quickly collect, store, and then slowly release moisture is an effective way to regulate moisture in living areas of buildings under construction as well as of newly erected ones. As a result of this study, it has been shown that it is possible to produce environmental control in residential premises not only through the operation of costly air conditioning systems that consume a significant amount of power, but also by using accumulating and easily releasing moisture building materials, providing a dampening effect. Studies have been carried out and troweling compounds with a high moisture-regulating ability with the use of domestic components have been developed, allowing, in addition to the above-mentioned purposes, to reduce the risk of water vapour condensation on the walls and the occurrence of fungi and mould in the room.


2019 ◽  
Vol 91 ◽  
pp. 04007 ◽  
Author(s):  
Kseniya Perovskaya ◽  
Daria Petrina ◽  
Evgeniy Pikalov ◽  
Oleg Selivanov

The research presents the experimental results devoted to the charge composition development for the production of wall ceramic products, based on low plasticity clay using additives. One of the additives is polymer waste in the amount of 15 wt. %, in particular it is unplasticized polyvinyl chloride used as a combustible additive for increasing ceramics porosity thus decreasing its density and consequently the load on the basement when the walls are constructed. Besides it decreases thermal conductivity and improves energy efficiency of developed wall ceramics application. Boric acid is a second additive used as a fuse thus reducing the temperature of ceramics liquid-phase sintering and forming a vitreous phase, which increases the strength characteristics and reduces water absorption, and therefore increases the product frost resistance. However the vitreous phase amount is insignificant and the products still are characterized by porosity sufficient for density and thermal conductivity reduction up to the level of conditionally effective thermal performance. Thus the application of the developed wall ceramics facilitate the production of energy effective products, which can be used for multi-layers walls construction providing modern thermal engineering standards and rational consumption of building materials. Herewith the developed materials properties correspond to the requirements of solid ceramic bricks used in Russian climatic conditions and help to combine the functions of bearing, heat-insulating and partly facing layers to a certain extend thus expanding their application.


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