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Photovoltaic (PV)-based solar chimneys could assist stack ventilation within a large space hall. This study considered a comprehensive office building with a PV-based solar chimney as a case study to explore measures for enhancing stack ventilation. A computational fluid dynamics (CFD) model was established, and the influences of the inner heat source, chimney inlet position, solar heat gain and photovoltaic (PV) arrangement on the ventilation rate were investigated. The results revealed that PV-based solar chimneys could assist stack ventilation and would effectively provide a suitable indoor environment for occupied areas during the transitional season. Raising the chimney inlet position is conducive to improving the ventilation rate and cooling performance. The increase in the inlet position from a height of 0.2 m to 3.8 m would increase the ventilation rate up to 5%. The heat gain from the PV backside is an important method of enhancing the ventilation rate. A 200 W/m2 heat gain can lead to a 16.4% increase in ventilation. Moreover, the lower the heat source location, the higher the ventilation efficiency. This study provides basic strategies for optimising design schemes to improve natural ventilation efficiency. [ABSTRACT FROM AUTHOR]

The relationship between the volumetric thermodynamic coefficients of liquid metals at the melting point and interatomic bond energy was studied. Using dimensional analysis, we obtained equations that connect cohesive energy with thermodynamic coefficients. The relationships were confirmed by experimental data for alkali, alkaline earth, rare earth, and transition metals. Cohesive energy is proportional to the square root of the ratio of melting point Tm divided by thermal expansivity αp. Thermal expansivity does not depend on the atomic size and atomic vibration amplitude. Bulk compressibility βT and internal pressure pi are related to the atomic vibration amplitude by an exponential dependence. Thermal pressure pth decreases with an increasing atomic size. Fcc and hcp metals with high packing density, as well as alkali metals, have the relationships with the highest coefficient of determination. The contribution of electrons and atomic vibrations to the Grüneisen parameter can be calculated for liquid metals at their melting point. [ABSTRACT FROM AUTHOR]

The ventilation rate of a greenhouse is one of the major factors to consider when assessing its ventilation performance. Compared with plain areas, high-altitude areas have lower air pressure, thinner air, and stronger solar radiation, which in turn affect the magnitude of the local greenhouse ventilation rate. This paper is based on the use of online monitoring and computational fluid dynamics (CFD) techniques for modeling and model validation. The average relative error (ARE), mean absolute error (MAE), root-mean-square error (RMSE), and determination coefficient (R2) of the temperature were 4.88%, 1.396 °C, 1.428 °C, and 0.9982, respectively. The ARE, MAE, RMSE, and R2 of the velocity were 9.525%, 0.035 m/s, 0.049 m/s, and 0.9869, respectively. Then, the distributions of the wind pressure, Reynolds number (Re), thermal pressure, air density, air speed, and temperature in greenhouses in high-altitude and plain areas were researched to obtain the relevant factors affecting the ventilation rates of greenhouses in high-altitude areas. In addition, correlation analyses were conducted for five variables affecting the ventilation rate: the inlet velocity, the temperature difference between the inside and outside of the greenhouse, the air density difference between the inside and outside of the greenhouse, total indoor radiation, and the internal heat source of the crop, and the coefficients of their correlations with the greenhouse ventilation rate were 1.0, −0.83, −0.72, −0.72, and 0.68, respectively. A natural ventilation rate model for plateau areas was developed, with the ARE, RMSE, and R2 between the sample values and fitted values determined to be 4.55%, 0.543 m3/s, and 0.9997, respectively. The model was validated by predicting the greenhouse ventilation rate in winter (3 January 2022), and the ARE, RMSE, and R2 of the sample values and predicted values were 9.726%, 8.435 m3/s, and 0.9901, respectively. This study provides a theoretical basis for further research on greenhouse ventilation characteristics in high-altitude areas. [ABSTRACT FROM AUTHOR]

The primary objective of this research is to study the bearing performance characteristics having different operating conditions. Experimental investigations are carried out on phosphorous bronze hydrodynamic journal bearing with a surface textured at different loading conditions with multi-grade oil as lubricating at different constant rotational speeds (i.e.,1000 to 4000 rpm) for studying the dynamic characteristics. Results reported that oil film pressure and temperature distribution profile obtained experimentally are in good agreement with the theoretical results. Fuzzy-based Taguchi optimisation has been used in this experimental analysis to predict the optimal input parameters, which result in the optimal combination of temperature and reported that the oil film pressure and temperature distribution profile obtained experimentally are in good agreement the theoretical results. This analysis also attempts to describe the application of the fuzzy logic-based Taguchi analysis to optimise the performance parameters. [ABSTRACT FROM AUTHOR]

The ventilation rate of a greenhouse is one of the major factors to consider when assessing its ventilation performance. Compared with plain areas, high-altitude areas have lower air pressure, thinner air, and stronger solar radiation, which in turn affect the magnitude of the local greenhouse ventilation rate. This paper is based on the use of online monitoring and computational fluid dynamics (CFD) techniques for modeling and model validation. The average relative error (ARE), mean absolute error (MAE), root-mean-square error (RMSE), and determination coefficient (R2) of the temperature were 4.88%, 1.396 °C, 1.428 °C, and 0.9982, respectively. The ARE, MAE, RMSE, and R2 of the velocity were 9.525%, 0.035 m/s, 0.049 m/s, and 0.9869, respectively. Then, the distributions of the wind pressure, Reynolds number (Re), thermal pressure, air density, air speed, and temperature in greenhouses in high-altitude and plain areas were researched to obtain the relevant factors affecting the ventilation rates of greenhouses in high-altitude areas. In addition, correlation analyses were conducted for five variables affecting the ventilation rate: the inlet velocity, the temperature difference between the inside and outside of the greenhouse, the air density difference between the inside and outside of the greenhouse, total indoor radiation, and the internal heat source of the crop, and the coefficients of their correlations with the greenhouse ventilation rate were 1.0, −0.83, −0.72, −0.72, and 0.68, respectively. A natural ventilation rate model for plateau areas was developed, with the ARE, RMSE, and R2 between the sample values and fitted values determined to be 4.55%, 0.543 m3/s, and 0.9997, respectively. The model was validated by predicting the greenhouse ventilation rate in winter (3 January 2022), and the ARE, RMSE, and R2 of the sample values and predicted values were 9.726%, 8.435 m3/s, and 0.9901, respectively. This study provides a theoretical basis for further research on greenhouse ventilation characteristics in high-altitude areas.

The present study aims to study the thermohydrodynamic performance of noncircular journal bearings lubricated with multigrade oil. Experimental investigations are carried out on phosphorous bronze hydrodynamic journal bearing with a surface textured at different loading conditions with multigrade oil (MAK 2T oil) as lubricant at different constant rotational speeds (i.e., 1000-4000 rpm) for studying the dynamic characteristics. The journal-bearing's thermodynamic behavior is analyzed by simplifying modified Reynolds and energy equations to obtain surface-textured bearing performance characteristics, such as load-carrying capacity, mass flow rate, and power loss. The noncircular bearings suggest several design parameters, such as a tilt angle for designers. By considering thermal effects for MAK 2T oil lubricant, the requirements of a specific application can be fulfilled. [ABSTRACT FROM AUTHOR]

The primary objective of this research is to study the bearing performance characteristics having different operating conditions. Experimental investigations are carried out on phosphorous bronze hydrodynamic journal bearing with a surface textured at different loading conditions with multi-grade oil as lubricating at different constant rotational speeds (i.e.,1000–4000 rpm) for studying the dynamic characteristics. Results reported that oil film pressure and temperature distribution profile obtained experimentally are in good agreement with the theoretical results. Fuzzy-based Taguchi optimization has been used in this experimental analysis to predict the optimal input parameters, which result in the optimal combination of temperature and reported that the oil film pressure and temperature distribution profile obtained experimentally, are in good agreement the theoretical results. This analysis also attempts to describe the application of the fuzzy logic-based Taguchi analysis to optimize the performance parameters.

Thermal pressure is an inevitable thermodynamic consequence of heating a volumetrically constrained sample in the diamond anvil cell. Its possible influences on experimentally determined density‐mineralogy correlations are widely appreciated, yet the effect itself has never been experimentally measured. We present here the first quantitative measurements of the spatial distribution of thermal pressure in a laser‐heated diamond anvil cell (LHDAC) in both olivine and AgI. The observed thermal pressure is strongly localized and closely follows the distribution of the laser hotspot. The magnitude of the thermal pressure is of the order of the thermodynamic thermal pressure (αKTΔT) with gradients between 0.5 and 1.0 GPa/10 μm. Remarkably, we measure a steep gradient in thermal pressure even in a sample that is heated close to its melting line. This generates consequences for pressure determinations in pressure‐volume‐temperature (PVT) equation of state measurements when using an LHDAC. We show that an incomplete account of thermal pressure in PVT experiments can lead to biases in the coveted depth versus mineralogy correlation. However, the ability to spatially resolve thermal pressure in an LHDAC opens avenues to measure difficult‐to‐constrain thermodynamic derivative properties, which are important for comprehensive thermodynamic descriptions of the interior of planets. Plain Language Summary: The primary window into the interior of the Earth below ~10‐km depth are earthquake waves that give us a three‐dimensional elasticity/density image of the planet. In order to translate this into a geological model of the Earth, we need to know the physical and chemical response of rocks with the composition of the Earth's interior at high pressures and temperatures. This is achieved by experiments in which samples are subjected to the high pressures and temperatures of the deep Earth using laser‐heated diamond anvil cells. A long‐standing problem of such experiments is a hard to quantify pressure term caused by the heating of the sample. This paper, for the first time, experimentally quantifies the spatial distribution of thermal pressure in a typical experiment and explores the effect of its incomplete knowledge on the deduced mineralogical composition of the Earth. Key Points: Thermal pressure and its gradient in a diamond anvil cell have been measured and found close to the magnitude expected based on the thermodynamic limitThe observed gradients in thermal pressure are very steep. This can lead to an underestimation of the real pressure experienced by a heated sampleUnderestimating the thermal pressure by only 20% can have a significant effect on inferred deep mantle iron content derived from laser‐heated diamond anvil cell experiments [ABSTRACT FROM AUTHOR]

Dealing with buoyancy-driven flow to reduce infiltration heat is challenging for buildings such as cold storages where the indoor-outdoor temperature differences are significant. In this study, a segmented recirculating horizontal air curtain (SRHAC) is proposed to respond to the vertical thermal buoyancy profile in doorways and recover the cold air entrained by the air curtain. Specifically, SRHAC is a planar turbulent impingement jet discharged through a vertically mounted rectangular nozzle. The discharge nozzle is divided into segments and the return vent recirculates the discharged air to the rear of the discharge nozzle. In this study, the aerodynamic sealing performance of the SRHAC is investigated by considering structural, operational, and ambient parameters. Orthogonal analysis reveals the flow rate, nozzle width, and discharge angle as significant factors affecting the thermal separation efficiency of the SRHAC. Increasing the flow rate and decreasing the nozzle width leads to an increase in the jet momentum flux, thereby enhancing the thermal separation efficiency, with a maximum efficiency of 75.9 %. Setting the discharge parameters in the three sections along the height improves the thermal separation efficiency by 16.5% points. The maximum efficiencies of two-, three-, and five-segment air curtains are 83.6 %, 87.3 %, and 90.3 %, respectively. The separation efficiency of the SRHAC remains relatively stable even when the indoor-outdoor temperature difference varies between 32 and 57 K. These results establish that the SRHAC is an efficient energy-saving device, with the ratio of reduced infiltration load to energy consumption as high as 110.9. [Display omitted] • Segmented recirculating horizontal air curtain (SRHAC) was proposed for thermal separation. • Key impact factors based on ANOVA: flow rate, nozzle width, segmented discharge angle. • The thermal separation efficiency of five-segment SRHAC reaches 90.3 %. • SRHAC efficiency remains stable against temperature fluctuations. [ABSTRACT FROM AUTHOR]

Abstract The understanding of heat and mass transfer phenomena and underlying flow and thermal mechanisms in a tunnel fire is critical for smoke control and human evacuation. Critical velocity has been acknowledged as the most critical parameter to guarantee the effectiveness of smoke control using longitudinal ventilation in tunnels. However, in slopping tunnels, even under the conditions where the expected smoke flow route and the corresponding critical velocity can be achieved, another flow pattern which has an opposite smoke flow direction and higher gas temperatures is also likely to be generated. This phenomenon has not attracted enough attention. In this paper, multiple patterns of heat and mass flow in a slopping tunnel induced by the competition of buoyancy and forced ventilation were examined using laboratory experiments, Computational Fluid Dynamics simulations and theoretical analysis. Both dynamic and steady state analyses were performed to explain the transient evolution behaviors and final steady solutions for these flow patterns. The constraints and the prerequisite conditions for the existence of multiple flow patterns or only a certain pattern were expressed in terms of three main influencing parameters including fire heat release rate, pressure rise induced by mechanical ventilation system and the fire source location. For the regime where both fan-dominated and buoyancy-dominated patterns can occur, the initial flow state and the flow evolution process determines the steady state solutions, indicating the activation time of the mechanical ventilation plays an important role in the final flow pattern. This study has particular relevance to understanding the complex heat and mass flow behaviors in a sloping tunnel fire and it provides new implications for smoke control. [ABSTRACT FROM AUTHOR]

In the present simulation study, the performance characteristics of vertical offset non-circular journal bearing have been evaluated. During study, the thermal pressures have been found of increasing nature with increase in speed in both the lobes of the bearing. A considerable rise in oil-film temperature and thermal pressure has been found in lower lobe and comparatively a low rise in oil-film temperature and thermal pressures has been found in upper lobe of the bearing. The trend for variation of oil-film temperature with speed has been found of increasing nature. The load capacity, power loss in the bearing and bearing characteristics Sommerfeld number has been observed to be of increasing nature with speed. It has been concluded that more than one lobe have been reported in the bearing profile under study, thus the profile can be considered as an alternate to circular journal bearing for better stability applications.

Tunnels are of key importance to the ventilation network in underground buildings. For sloping tunnels, the effect of thermal pressure on the underground ventilation system has not been clarified in the existing research. A field test in an underground sloping tunnel was carried out and the results showed that the temperature decreases in the form of exponent. Based on an exponential model of temperature decrease, an equation to predict thermal pressure is proposed for sloping underground tunnels. Four factors on the thermal pressure, surface roughness of the tunnel wall, air velocity, dimensions of the underground tunnel and temperature difference between the air and the tunnel wall are discussed in detail. Surface roughness of the tunnel wall, air velocity and dimensions of the tunnel have been found having little impact on the thermal pressure efficiency when the tunnel is beyond the length of L min . The temperature difference between the air and the tunnel wall is the main factor on the thermal pressure efficiency. A simplified method is recommended to calculate the thermal pressure for sloping underground tunnels. [ABSTRACT FROM AUTHOR]

The paper presents the emergence of thermoelastic distortions at the contact of the drum with the brake shoe from a vehicle. The critical sliding speed is determined, assuming the existence of small initial sinusoidal undulations and their growth. For higher speeds than the critical speed, the size of the 'hot-spots' expands at different rates. It is also taken into consideration the influence of wear rate on the size of the 'hot-spot' surface. [ABSTRACT FROM AUTHOR]

A new correlation function for the calculation of viscosity for five typical supercritical gases is presented using the rainwater-Friend and modified Enskog theory. It is shown that by using accurate value for the thermal pressure and co-volume in the modified Enskog theory, this correlation function is suitable for calculation of the viscosity of supercritical gases, without any density and temperature limitation. For this purpose, two new correlation functions for the calculation of the thermal pressure coefficient and co-volume are presented. It is also shown that the co-volume in the modified Enskog theory depends not only on temperature, but also on density. The accuracy of the calculated viscosity is about 1%, which is much better than the previous work. It is also shown that the modified Enskog theory can be extended to very high density-temperature ranges by choosing correct values for the thermal pressure and co-volume.

In order to analyze the influence of opening area ratio on natural ventilation in city tunnel under block transportation, dimensionless analysis, model experiment and CFD (computational fluid dynamics) simulation are used to evaluate the velocity distribution, temperature distribution and the pollutants concentration. The similarity criterion of thermal-pressure ventilation and proportional constant of the heat with the same temperature distribution are obtained by the dimensionless analysis about the thermal buoyancy and gravity of the most adverse section at block transportation. According to the similarity conditions, several groups of model experiments and computer models are built. Results of the model experiments and CFD simulations show that with the increase of opening area ratio, the effect of the natural ventilation improves at the beginning, but as opening area ratio continues to increase, the role of natural wind pressure outside tunnel is strengthened. There are some uncertainties of the natural wind pressure which might lead to the ventilation effect decline. With the increase of opening area ratio, the construction cost of vent shaft increases observably at the same time. So it is of great significance for city tunnel to choose an appropriate opening area ratio which can meet the requirements of ventilation under the block transportation without superfluous cost of blindly increasing opening area ratio investment. [ABSTRACT FROM AUTHOR]

• The distributions of temperature and air velocity for a curved double-skin façade (CDSF) were investigated. • The nonuniformity of solar irradiation on a curved surface is higher than that of a planar surface. • The thermal pressures of a CDSF show different values at different positions. • Solar irradiances show a power function relationship with the air velocity. • There should be transverse flows and heat transfers in the cavity of a CDSF. Curved architectural forms are becoming popular in modern building designs, resulting in more demanding requirements of curved double-skin façades (CDSF). However, CDSF's natural ventilation performance is barely known, as most current studies investigate planar DSF (PDSF). This paper experimentally evaluated the thermal performance of a reduced scale CDSF model. Experimental results show that CDSF can form natural ventilation by buoyancy, however, with significant discrepancies in the distribution of solar irradiances on the curved surface. Observed nonuniformity shows 30.05 % on average vertically and 9.12 % on average horizontally. The thermal pressures vary at different horizontal positions with a fluctuation range between 0.056 Pa and 0.063 Pa, indicating the influence of gradients and the existence of transverse flows and heat transfers in the cavity. Moreover, the effects of solar irradiation and outdoor air temperature on the CDSF are discussed. The results show that solar irradiation is the main influencing factor on the thermal performance of a CDSF, which are correlated with air velocities in the form of power functions. The influence of solar irradiation on CDSF is similar to that of PDSFs, but CDSF exhibits a bigger exponent. In comparison, outdoor air temperature shows very limited effects, and the influence of outdoor air temperature on CDSF is similar to that of PDSF. For the analyzed CDSF, the thermal pressures only fluctuate from 0.053 Pa to 0.055 Pa when the outdoor air temperature raises from 24 °C to 36 °C. [ABSTRACT FROM AUTHOR]

We have presented an analysis of the volume expansion data for periclase (MgO), lime (CaO), corundum (AlO) and spinel (MgAlO) determined experimentally by Fiquet et al () from 300K up to 3000K. The thermal equation of state due to Suzuki et al () and Shanker et al () are used to study the relationships between thermal pressure and volume expansion for the entire range of temperatures starting from room temperature up to the melting temperatures of the solids under study. Comparison of the results obtained in the present study with the corresponding experimental data reveal that the thermal pressure changes with temperature almost linearly up to quite high temperatures. At extremely high temperatures close to the melting temperatures thermal pressure deviates significantly from linearity. This prediction is consistent with other recent investigations. A quantitative analysis based on the theory of anharmonic effects has been presented to account for the nonlinear variation of the thermal pressure at high temperatures. [ABSTRACT FROM AUTHOR]