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The size of the wall panel was smaller than the inner part of the climatic chamber , and the remaining space of the chamber was filled hermetically with insulation . The temperatures of the chamber one and two were set at −24 ° C ( Tcold ) and + 22 ° C ( Thot ), respectively . The temperature and heat flux density meters were programmed to measure and record the values of temperature and heat flow every 15 min during the day .
The ANSYS CFX software package , a computation fluid dynamics ( CFD ) programme , was employed to assess the heat convection and conduction in the 3D-printed block enclosing structures . The Boussinesq approximation was utilised to describe the airflow in laminar formulation , while the Newton – Richmann law was used to describe the convective temperature on the outer boundaries of the blocks .
OBSERVATIONS The study analysed the most common 3D-printed enclosing structures and new enclosing structures . The heat fluxes and temperature outside and inside a 3D-printed structure were measured in climatic chambers for the first time . Energy modeling of a building with 3D-printed enclosing structures with various construction configurations was also conducted successfully .
In the physical experiment , the cold chamber temperature Tcold was dialed in less than 40 min from the start . In the first 120 min , a precipitate drop in the temperature was observed at the sides of the structure / additive wall panel with 0-35 mm thickness , while a significant reduction in temperature was observed inside the structure with 185-255 mm thickness .
After 120 min , the time interval was more than two hours for the comparing isotherms . The CFD modeling of the experimental structure showed that the air was hotter in the upper part of the structure compared to the concrete lintel in the middle part , while the air was colder in the lower part compared to the middle part . The difference in local temperature between air and concrete was 15 oC .
Additionally , the temperature isoline becomes more curved while moving from the cold or hot side to the center of the structure . The temperature difference between the upper and lower sides in the center of the structure ’ s side face was 5 oC .
Moreover , the heat flux through the air parts was significantly lower compared to the solid parts of the structure . The convection also influenced the surface heat flux distribution as the heat flux changed from 100 to 70 W / m 2 along the vertical coordinate when the temperature gradients changed due to convection .
Three cold rectangular cavities , two hot triangle cavities , and one rectangular cavity were observed in the structure . All cavities , excluding the small triangle cavities , led to stabilising effects on the concrete temperature , with notable differences in air temperature present only in the boundary layers . The average heat flux through the U-value of the construction was 1.18 .
The CFD simulations of the 3D-printed enclosing structures with various configurations demonstrated that some heat resistance can be added due to the convection in the enclosed structures compared to the empirical approach . Moreover , the influence of convection was stronger on more uneven cavern distributions . Thus , empirical formulas were unsuitable for engineering purposes for structures with insulation as they provided lower U-values .
The energy consumption of a 3D-printed building composed of additive enclosing structures with various construction configurations was between 3026 and 8536 kWh per year .
Thermal imaging of the 3D-printed enclosing structure displayed surface irregularities , leading to thermal inhomogeneity . More research is required on inhomogeneities to properly determine the thermophysical properties of the structures .
To summarise , the findings of this study effectively demonstrated the thermal performance of 3D-printed enclosing structures . RACA
Article by Samudrapom Dam via AZO Materials . Sourced from Nemova , D ., Kotov , E ., Andreeva , D . et al : Experimental Study on the Thermal Performance of 3D-Printed Enclosing Structures .
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RACA Journal I November 2022 www . refrigerationandaircon . co . za