Русский Русский

Zhangabay N.Zh.

Candidate of Technical Sciences (PhD), Associate Professor, M. Auezov South Kazakhstan University, Department of Architecture and Urban Planning

A field comparison of the thermal performance of ventilated and plastered façades in hot conditions using the climate of Southern Kazakhstan as an example: internal surface temperature and air conditioning energy efficiency

https://doi.org/10.58224/2618-7183-2026-9-5-2
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Аннотация
This paper presents a field (full-scale) study comparing the thermal performance of a ventilated rainscreen façade (VRF) and a traditional plastered (“wet”) façade on the eastern façade of a nine-story reinforced concrete frame residential building in Southern Kazakhstan during a hot summer period. Sensor-equipped sections of the multilayer wall structure from the 1st to the 9th floors were monitored simultaneously using DS18B20 multichannel contact temperature sensors, an unmanned thermal imaging system (DJI Mavic 3 Thermal), and a handheld thermal imager (Testo 875), providing double, independent validation of surface temperature data. Measurements were taken at 9:00, 12:00, 15:00, and 18:00 on a typical hot day. Although the temperature of the VRF exterior cladding during peak insolation hours exceeded the temperature of the wet façade by up to 2.2°C (reaching 60.1°C on the ninth floor at midday), the temperature of the VRF internal surface was consistently lower than the temperature of the wet façade internal surface on virtually all floors and at all times, the decrease reached 1.55°C, and averaged 1.0-1.3°C during the hottest hours. This apparent paradox, a hotter exterior cladding with a cooler internal surface, is explained by convective decoupling, which is provided by the ventilated air gap: it removes solar-heated air before it has a chance to transfer heat to the load-bearing wall via conduction. Based on the measured temperature difference of the internal surface and its standard heat transfer coefficient, it was shown that the conductive-convective component of the air-conditioning load for rooms behind the VRF is reduced by approximately 7-10% compared to a wet façade during typical hot daytime hours. These results, which relate to the relatively little-studied hot arid/continental climate of Central Asia, expand the evidence base, formed primarily from Mediterranean and Western European studies, and create a natural experimental basis for further thermal and aerodynamic modeling of the ventilated air gap.
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Modeling of an engineering method for calculating the thermal stability of walls with a shielded external surface

https://doi.org/10.58224/2618-7183-2026-9-2-6
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Аннотация
This paper presents a modeling methodology for an engineering calculation of the thermal stability of external walls with a shielded outer surface forming a ventilated façade system. The objective of the study is to develop a practical design tool for assessing the amplitude attenuation and phase shift of the internal surface temperature under daily climatic fluctuations. The method is based on the solution of a one-dimensional transient heat conduction problem for a multilayer structure subjected to periodic climatic effects. The external boundary condition is defined through an equivalent heat transfer formulation that accounts for shortwave solar radiation, longwave radiative exchange between the screen and the ambient environment, convective heat transfer, and possible ventilation of the air cavity. An engineering calculation algorithm is proposed that incorporates the effect of equivalent solar loading and harmonic variations of outdoor air temperature with high amplitudes of environmental and near-wall air layer fluctuations. A numerical procedure is provided for the “screen – air gap” subsystem, followed by the evaluation of internal surface temperature attenuation and transient heat transfer characteristics. Validation against numerical simulations and experimental data demonstrates a deviation not exceeding 5-10%. The results indicate a significant influence of screen reflectivity, air gap ventilation intensity, and wall heat capacity on improving thermal stability and reducing heat gains during the hot season. The proposed enhanced assessment algorithm can be widely applied in design practice, including the selection of thermal insulation thickness for building envelopes in southern regions, the determination of design loads for ventilation and air-conditioning systems, and the evaluation of indoor thermal conditions under intermittent heating and ventilation regimes. The practical significance lies in the ability to optimize façade system parameters with shielded external surfaces to prevent overheating and improve building energy efficiency. The study is conducted within the framework of ensuring thermal safety of buildings in warm climate conditions.
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Experimental evaluation of the thermophysical performance of an adaptive composite wall system under dynamic climatic conditions

https://doi.org/10.58224/2618-7183-2026-9-1-8
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Аннотация
In the sharply continental and hot climate of Kazakhstan, improving building energy efficiency requires adaptive composite envelope systems capable of dynamically responding to external thermal loads. This study provides experimental validation of a newly developed adaptive energy-efficient wall assembly with alternating air channels and a radiant barrier, previously proposed and numerically investigated by the authors. The experiments were conducted in a climatic chamber using a full-scale 3×3 m wall fragment under two operating modes: cold conditions (–14.3 °C) and hot conditions (+26.4 °C with exterior cladding heated up to +46 °C). Interlayer temperatures, heat flux density, and thermal bridging in the bracket zone were measured, and both calculated and effective thermal transmittance resistance values were determined in accordance with regulatory requirements. The experimental results demonstrated strong agreement with numerical simulations: deviations in interlayer temperatures did not exceed 3-7%, while heat flux density differed by 6-9%. The wall configuration Scheme 3/50/75/50 exhibited pronounced adaptive behavior; switching to the ventilation mode during the hot period reduced heat flux density by up to 14% and decreased the temperature gradient within the air channel by an average of 3-5 °C. Under cold conditions, the system increased thermal resistance by up to 18% compared with assemblies without a reflective layer. The obtained effective thermal resistance values comply with the building standards of the Republic of Kazakhstan and confirm the energy efficiency of the wall system for operation in extreme climates. Overall, the experimental validation confirms the reliability of the model and the high practical applicability of the adaptive wall technology. The findings provide a scientifically grounded basis for the development of façade design standards optimized for Central Asian climates and demonstrate the potential for implementation in both new construction and retrofit projects.
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Analysis of the influence of temperature loads on the stress-strain state of a pre-stressed cylindrical shell

https://doi.org/10.58224/2618-7183-2025-8-4-5
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Аннотация
The progressiveness of the idea of prestressing consists, on the one hand, in the possibility to regulate the stress state in accordance with the peculiarity of the structure operation, and on the other hand, in the expansion of the economically advantageous range of application of high- and high-strength steels. Such strengthening is also relevant for cylindrical shells, the throughput or storage volumes of which are directly proportional to the operating pressure. The most effective type of prestressing in this case is considered to be winding on the shell body at an angle to the longitudinal axis or in the annular direction without tilting the high-strength profile. In this regard, in this work, a theoretical study of the influence of temperature loads on the stress state of the combined shell was carried out. As a result of the study, an analytical evaluation method was developed that takes into account the mechanical, geometric values of the wall and wrapping material, as well as the parameters of the prestress, taking into account temperature effects. The developed method also found that the established ring stresses in the shell wall increase with an increase in the temperature gradient, and the stresses in the wrapping decrease. At a temperature gradient of 70°C, the ring stresses increased by 1.8 times, and the stresses in the wrapping decreased by 1.3 times. At the same time, the change in operating temperature has a noticeable effect on the distribution of stresses in the wall of the shell and wrapping. Thus, calculations of a main pipeline pre-stressed with steel wire showed that at a temperature gradient of ΔΤ=30°C, the achieved level of prestressing can decrease by 10-12% compared to the initial one, and at ΔΤ=50°C, the pre-stressed wrapping does not affect the stress state of the shell wall. The obtained results of the study indicate that, taking into account the temperature loads on the structure, it is possible to adopt the necessary design parameters for further design of steel shells even more accurately.
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