Internal Wall Surface Research Articles

Mould Risk in Technical Room in Four Underground Water Reservoirs

Abstract This conference article analyses the indoor climate of a technical room in four underground water reservoirs. This indoor climate with minimal input energy is specific by high relative humidity and low air temperature, as shown in the experimental measurement. The unsteady 2D numerical simulation of the detail section (partly sub-terrain peripheral wall and floor) in software Calculation Area 4.0e calculates fluctuation of internal surface temperature and relative humidity. Finally, the empirical predictive Finnish VVT model predicts the seasonal mould risk on the internal surface of the peripheral wall.

Evaluation of Calcarenite Degradation by X-ray Photoelectron Spectroscopy Analysis inside the Rupestrian Church of San Pietro Barisano (Matera, Southern Italy)

We report on the XPS analysis of degraded surfaces inside San Pietro Barisano, the rupestrian church carved into the calcarenite rock of ancient Matera, which has been a UNESCO World Heritage Site since 1993. As reported in previous works, the “Sassi” district and the park of rupestrian churches were available as open laboratories for the National Smart Cities SCN_00520 research project dedicated to the sustainable recovery of this remarkable architectural heritage. In that context, XPS functionality was shown to reside in the possibility of analyzing surfaces by feasible sampling, acquiring spectra without any preliminary sample treatment, and processing data using a well-established curve fitting procedure. The obtained results allowed us to identify the degradation products of the investigated surfaces, thus contributing to defining a diagnostic framework for subsequent actions. Accordingly, the samples here considered, collected from the internal wall surfaces of the church, were all analyzed in comparison with the reference calcarenite, and the XPS results were evaluated as a function of local environmental factors and the historical context of the church itself. The final aim was to provide, for each sample, the most representative indicator(s) of biotic and/or abiotic degradation for reliable use, in a multidisciplinary context, in planning care interventions for building heritage.

A simple parameter configuration scheme for a simplified dynamic model of pipe-embedded wall

A pipe-embedded wall (PE-wall) can effectively reduce the building load through the water circulation in the embedding pipes. Using renewable energy as an alternative, the water may be produced by solar water heater, or by cooling tower etc. This PE-wall may be used to reduce the building energy consumption, which is beneficial to achieve nearly zero energy building (nZEB) target. In this study, a simple parameter configuration scheme is proposed for the RC simplified dynamic model of the PE-wall. Based on the wall geometry and thermal properties, the scheme can directly determine thermal resistance (R) values and thermal capacitance (C) values for a 5R3C simplified dynamic model. The finite element frequency domain (FEFD) models and time-domain CFD models of three typical (i.e., light-weight, medium-weight and heavy-weight) PE-walls are established as reference. The simplified 5R3C model with parameters determined by the configuration scheme is validated in terms of their thermal responses both in frequency domain and time domain. Under specified dynamic boundaries, mean relative errors of heat flow on the internal wall surface and internal pipe surface are less than 5 %. The comparison results indicate the good accuracy and reliability of the parameter configuration scheme for the RC simplified dynamic model.

Mounting of Embryos, Larvae, and Pupae for Live Drosophila Dendritic Arborization Neuron Imaging.

Live imaging approaches are essential for monitoring how neurons go through a coordinated series of differentiation steps in their native mechanical and chemical environment. These imaging approaches also allow the study of dynamic subcellular processes such as cytoskeleton remodeling and the movement of organelles. Drosophila dendritic arborization (da) neurons are a powerful experimental system for studying the dendrite arbor in live animals. da neurons are located on the internal surface of the body wall and, therefore, are easily accessible for imaging. Moreover, many genetic tools target da neurons to disrupt genes or proteins of interest and allow the investigator to visualize fluorescent markers and endogenously tagged proteins in the neurons. This protocol introduces methods for preparing and mounting intact Drosophila embryos, larvae, and pupae, allowing live imaging of dynamic cellular processes in da neurons.

Design and control intended low-order model for transient investigation of an electric oven: Static mode

In general, electric ovens represent a low-efficiency class among home appliances, contributing to overall environmental changes in buildings and apartments. To improve their low efficiency, which is typically between 10% to 12%, industries are increasingly focused on developing effective technologies. One suitable strategy is to design and control the oven's center temperature, as specified by the EN 60350-1 European standard, which regulates the energy efficiency index (EEI) test. The present simulation study explains the transient thermo-fluid behavior of a domestic electric oven subjected to free convection, i.e., static mode. For this purpose, appropriate dynamic models are employed, intended for design and control. A lumped-parameter based methodology is considered to develop a low-order dynamic model, resulting in reduced computational cost and run time. A finite level of discretization is introduced into the model, enabling the capture of limited insights, such as temperature, heat flux, mass flow rate, pressure drop, etc., particularly at the cavity center, internal and external cavity wall surfaces, and at suction and exit openings. The electric oven is mainly divided into four sub-systems: door, cavity, ventilation, and cabinet. Each sub-system has a suitable level of discretization signifying a lumped mass parameter to reproduce the transient behavior within the electric oven. Heaters are considered as individual lumped masses and are integrated within the cavity sub-system. The above sub-systems employ both the first principle equations and correlations based on experimental data, giving a low-order grey-box identity to the system. In addition to conduction and convection, a non-linear form of radiation is considered to increase model accuracy. The developed model is further calibrated with available physical data. Once calibrated, the model is then compared with the remaining physical data produced at different heat loads to understand the accuracy in terms of transient temperature prediction at various temperature set points.

Prospective PCM–Desiccant Combination with Solar-Assisted Regeneration for the Indoor Comfort Control of an Office in a Warm and Humid Climate—A Numerical Study

Favorable thermal conditions within buildings are a necessity. Mechanical air conditioning, although effective, contributes a significant percentage of the world’s total energy use, which contributes to global warming. In addition, the refrigerants used in air conditioning also contribute to global warming. Passive means to provide thermal comfort have therefore been considered as alternative solutions. Phase-change materials (PCMs) have been considered as one passive cooling option. Although this option achieves a certain degree of effectiveness, especially in warm and dry climatic conditions, its effectiveness in warm humid climates is subdued due to its inability to handle humidity. In the present study, the suitability of a novel passive comfort provision strategy that combines a PCM and a desiccant is assessed. The passive system operates in a cycle of two phases: the moderating phase and the regenerating phase. For the proposed strategy, the regeneration process first involves the external desiccant bed, then night air drying using the regenerated external bed; the dried air subsequently regenerates the internal wall surface. The study involves the modeling of the proposed strategy and simulation of its performance. The simulation results indicate the significant potential for providing satisfactory comfort and health conditions through application of a combination of a desiccant and a PCM.

Structural Analysis and Optimization of Urban Gas Pressure Regulator Based on Thermo-Hydro-Mechanical Coupling

As a core component in the gas transmission process, the internal wall surface of a gas pressure regulator is prone to failure due to long-term exposure to a high-pressure gas environment, resulting in poor reliability of the regulator. Thus, a thermo-hydro-mechanical coupling model for the FL gas pressure regulator is established in this paper, and the thermo-hydro-mechanical coupling results are verified by engineering data. The effect of valve opening on the parameters (temperature, deformation, and stress) of the gas pressure regulator is studied in detail through simulation. The results show that the stress is greater at the sleeve, valve bore, and outlet valve seat wall under the opening of 20% of the regulator. Finally, the response surface method is used to optimize the regulator to obtain a good fit and high predictive ability of the response surface equation. The optimal parameters for the gas pressure regulator are as follows: the wall thickness of the sleeve is 7.25 mm, the diameter of the valve bore is 25 mm, and the wall thickness of the outlet seat is 31.05 mm. The maximum equivalent stress with this combination of parameters is 135.62 MPa.

Power consumption of model houses with and without PCM plaster lining using different heating methods

Thermal behaviour and power demand of two container model houses were studied. One of them was equipped with plaster lining with incorporated PCM microcapsules, and the second one served as reference during two successive winter periods. In the first winter period of 2019/20, an electric radiator was applied for heating the houses during the daytime, and then they were let cool down from evening to the next morning. The dynamic thermal behaviour and power demand of the model houses were investigated during the heating up periods, then in a quasi-thermal equilibrium, as well as along their spontaneous cooling down process at changing environmental temperatures. The indoor and environmental air temperatures, internal and external wall surface temperatures were collected by data logger during the whole winter periods for both model houses. Through the second winter period of 2020/21 the same methodology was used; nevertheless, the model houses were heated by air-air heat pumps. The performance coefficient (COP) of heat pumps was compared to the electric radiators. The estimated COP showed significant correlation with the temperature differences between the outdoor and indoor air temperatures, considerable worsening from COP = 3.1–3.4 to COP = 2.0–2.1 with increasing temperature drop to be overcome by the applied air-air heat pumps. However, there was no considerable dependence observed between the reference and PCM plaster lined houses. Equations were suggested to estimate the power demand in quasi-thermal equilibrium for both model houses and both heating methods as a function of the temperature differences between indoor and outdoor air. The power demand of PCM plaster lined model house compared to the reference house was lower by 10.3 % and 7.0 % using electric radiators or heat pumps, respectively, throughout the whole winter period, considering a medium temperature drop of 20 °C through the walls.

Experimental and numerical studies on the enhanced heat transfer performance and the flow resistance characteristics of the double-wall cooling structure with jet impingement holes and pin fins

The double-wall cooling as one of the most important cooling techniques of the hot-end components of aero-engine, the heat transfer performance of double-wall cooling structure can be significantly enhanced by the combination of jet impingement cooling and pin fins. Therefore, the double-wall cooling structure with jet impingement holes and pin fins has very important engineering application value. For the double-wall cooling structures with jet impingement holes and pin fins, the experimental studies have been carried out based on various of geometrical and flow parameters. Furthermore, the corresponding numerical simulations have also been carried out according to the corresponding experimental study conditions. In order to approximate to the real double-wall enhanced heat transfer structure of the hot-end components of the aero-engine, in present experimental and numerical studies, the double-wall enhanced heat transfer structure with the double-side outflow channel and the advantage of structural symmetry is adopted. Based on the numerical simulation results, the internal flow field structure, the flow resistance characteristics and the interior enhanced heat transfer performance of the double-wall cooling structure with jet impingement holes and pin fins are analyzed in detail. In addition, the main reasons why the pin fins can enhance the heat transfer performance of the double-wall cooling structure that with jet impingement holes and pin fins are further revealed. Actually, the enhanced heat transfer performance of the double-wall cooling structure is the results of the interactions between the internal jet impingement cooling, the internal crossflow and the turbulent flow of pin fins. Moreover, the influences of the jet impingement Reynolds number (Re), the non-dimensional row spacing (X/D) and the non-dimensional hole pitch (Y/D) of jet impingement holes, and the dimensionless diameter (Dp/D) of the pin fins on the enhanced heat transfer performance, the internal flow characteristics, the distributions of local Nusselt number Nu and the flow resistance characteristics of the double-wall cooling structure with jet impingement holes and pin fins are further revealed. Importantly, for all numerical simulation conditions, the distribution differences of the enhanced heat transfer performances on the wall surface of the pin fins and on the wall surface of the jet impingement target plate with the variations of the geometrical parameters and the flow parameters are analyzed in detail. The numerical results indicate that the area-averaged Nusselt number Nu═ on the wall surface of the pin fins is higher than that on the internal wall surface of the jet impingement target plate. With the increase of the pin fins diameter Dp/D, the Nu═ on the whole internal wall surface of the double-wall cooling structure presents a tendency of firstly decrease and then gradually increase. In addition, the Nu═ on the entire interior wall surface of the double-wall cooling structure decreases with the increase of row spacing X/D, but it is not sensitive to the variation of hole pitch Y/D. Moreover, for the discharge coefficient of the double-wall cooling structure, it gradually increases with the increase of the jet impingement Reynolds number Re, the row spacing X/D and hole pitch Y/D of jet impingement holes, but it decreases with the increase of the diameter Dp/D of pin fins. Finally, for 3 ≤ X/D ≤ 5, 3 ≤ Y/D ≤ 5, 1≤Dp/D ≤ 2, and 9000 ≤ Re ≤ 30,000, a correlation of the area-averaged Nusselt number Nu═ is given, which is in good agreement with the experimental results.

Three-dimensional temperature profile in a dome-shaped habitat structure on the moon

This paper presents the methodology to determine the temperature profile at the surface and through the wall thickness of a monolithic hemispherical dome-shaped habitat structure built on the lunar surface. The three-dimensional thermodynamic equation of heat diffusion is used to determine the temperature profiles using the explicit finite difference scheme. The direct solar radiation and lunar albedo are taken as the heat sources on the habitat structure whereas non-blackbody radiation and habitat albedo were taken as heat sinks. In this study, all the applicable modes of heat transfer – radiation in the external wall surface, convection in the internal wall surface (interior habitat will have air for human missions), and conduction in the structural wall body – have been considered. This temperature analysis study also takes into consideration of the self-shadowing effect of the habitat structure itself. The temperatures at the surface and through the wall thickness of the monolithic dome habitat structure were determined for the habitat structure made of sintered lunar regolith simulant, and for the purpose of comparison, regular terrestrial concrete, for three complete lunar day-and-night cycles. While the maximum temperature of around 390 K was observed at the apex of the sintered lunar regolith simulant dome during the lunar noon, the minimum temperature observed was around 213.5 K during the night time on the external surface of the habitat wall. The corresponding results for the lunar habitat structure made of terrestrial concrete were 364 K and 222.5 K, respectively. At the inner surface of the 40 cm thick habitat structure (in contact with interior habitat environment), the temperature fluctuation (difference between maximum and minimum temperatures) can be up to 30 K for each material type. The results from this study should help to determine the structural stresses and deflections caused by such lunar environment temperature fluctuations and the heat regulation for habitability in the future habitat structure on the Moon. Moreover, the methodology presented in this study should be applicable to conduct parametric studies to evaluate the effect of different parameters on the structural habitat temperature results.

Graphitic carbon-doped SnO2 nanosheets-wrapped tubes for chemiresitive ppb-level nitric oxide sensors operated near room temperature

The development of low-temperature metal oxide-based sensors with high sensing response towards harmful ppb-level gases remains challenging. Based on the idea of biological structure imitation, we choose wooden hydrangea petals as biotemplate and carbon source to controllably replicate graphitic carbon-doped SnO2 material (GC/SnO2-6) by simply calcining the salt solution-soaked precursor at 600 °C. Its morphology is tube bundle wrapped by corrugated sheets that formed by cross-linkage of nanoparticles. The internal surface of tube wall is decorated with nanoaggregates. The fabricated GC/SnO2-6 sensor exhibits response value of 256.3 towards 1 ppm NO at 50 ℃, which is 9.9 times higher than that (S = 26.0) of pure SnO2-7 material obtained by calcining at 700 ℃ in air. Meanwhile, this sensor also has short recovery time (42 s), low actual detection limit (50 ppb), satisfactory moisture resistance and long-term stability. Such excellent comprehensive gas-sensing performance is attributed to the homogeneous mesopore and large specific surface area of its biomorphic structure, as well as the synergism of graphitic carbon doping and abundant oxygen vacancies. In addition, the enhanced sensing mechanism is also explored in detail.

Integration of PCM as an external wall layer in reducing excessive heat of building walls

Innovative building approaches, which take advantage of heat energy in buildings, have recently appeared as part of a global effort to save energy. Incorporating phase change material (PCM) into the building envelope helps in reducing energy consumption and regulating energy demand by managing the thermal inertia of designed PCM thermal characteristics. A study was conducted to assess the performance benefits provided by the latent heat of the concrete wall combined with PCM. This study focuses on developing and testing heat barrier performance by incorporating PCM into wall external finishing, i.e. cement plaster and gloss paint. The effect of PCM inclusion in building wall were investigated by experimental work. The results indicate that incorporating PCM into the building wall reduced the surface temperature by up to 9 °C. Furthermore, the application of the PCM in the plaster layer is more reliable in reducing the internal wall surface temperature by a value of 8.1 °C when compared to the PCM in a painted coating. Painted wall panels experienced more significant temperature reduction differences than other wall panels, i.e. 9.2 °C and 9.5 °C, respectively. However, painted wall panels experienced higher internal surface temperatures than external surface temperatures compared to plastered wall panel at night. This could be due to the paint reactions, which are ineffective at releasing internal heat from the building at night. The yearly energy demand is decreased by 64.3% by incorporating PCM to the building wall, with a total annual electricity bill savings of 42.3% (8695.8 kWh yr−1). Therefore, it was concluded that wrapped PCM integrated into plaster layers on external surface building walls could decrease the indoor building temperature and thus contribute to conserving the energy required for an air conditioning system.

Mechanical Characteristics of the Flebogrif System-The New System of Mechano-Chemical Endovenous Ablation.

Non-thermal endovenous ablations, due to the lowest probability of complications, are the new method of treating chronic venous insufficiency—one of the most common diseases globally. The Flebogrif system (Balton Sp. z o.o., Warsaw, Poland) is a new mechano-chemical ablation system causing the mechanical damage of endothelium that allows for better sclerosant penetration into its wall. The purpose of the article is to provide mechanical characteristics in the form of force–displacement dependence for a single cutting element, and a bundle of cutting elements of Flebogrif as a whole for different levels of protrusion of the bundle of cutting elements. A TA.HD plus (Stable Micro Systems, Godalming, UK) analyzer equipped with special handles, was used for characteristics testing. The head movement speed used was 5 mm·s−1. The Flebogrif system was tested for three cutting element protrusion levels: L = Lmax, L = 0.9·Lmax, and L = 0.8·Lmax. Before testing, geometric measurement of the spacing of the cutting elements for three proposed protrusions was performed. It was established that decreasing the working length of the cutting elements will increase their rigidity, and, as a result, increase the force exerted on the internal surface of the vein wall. The obtained characteristics will allow for specifying contact force variability ranges and the corresponding diameter ranges of operated veins.

Low-impact techniques for seismic strengthening fair faced masonry walls

Two techniques for the seismic strengthening of fair faced rubble masonry walls are proposed and tested on a shake table. The first solution entails the use of carbon fibre reinforced polymer connectors installed from outside through the natural stone units, without perforating the entire wall thickness, thus leaving the internal wall surface undisturbed. In the second solution, stainless-steel cords are embedded in repointed mortar joints of the fair face and connected, by means of stainless-steel bars, to a thermo-insulating composite reinforced mortar applied to the internal side. Shake table tests were performed under natural accelerograms on real scale multi-leaf rubble masonry walls, built with the stone units retrieved from the debris of a hamlet heavily damaged in the 2016 Central Italy earthquakes. Both strengthening solutions proved effective in enhancing the seismic capacity by preventing leaf separation and masonry disintegration, and in limiting damage development under earthquake excitation. Thanks to the compatibility with original materials and the preservation of the fair face, they are suitable for mitigating the seismic vulnerability of architectural heritage.

Experimental and Theoretical Study on the Internal Convective and Radiative Heat Transfer Coefficients for a Vertical Wall in a Residential Building

Experimental studies on internal convective (CHTC) and radiative (RHTC) heat transfer coefficients are very rarely conducted in real conditions during the normal use of buildings. This study presents the results of measurements of CHTC and RHTC for a vertical wall, taken in a selected room of a single-family building during its everyday use. Measurements were performed using HFP01 heat flux plates, Pt1000 sensors for internal air and wall surface temperatures and a globe thermometer for mean radiant temperature measured in 10 min intervals. Measured average CHTC and RHTC amounted to 1.15 W/m2K and 5.45 W/m2K, compared to the 2.50 W/m2K and 5.42 W/m2K recommended by the EN ISO 6946, respectively. To compare with calculated CHTC, 14 correlations based on the temperature difference were applied. Obtained values were from 1.31 W/m2K (given by Min et al.) to 3.33 W/m2K (Wilkes and Peterson), and in all cases were greater than the 1.15 W/m2K from measurements. The average value from all models amounted to 2.02 W/m2K, and was greater than measurements by 75.6%. The quality of models was also estimated using average absolute error (AAE), average biased error (ABE), mean absolute error (MAE) and mean bias error (MBE). Based on these techniques, the model of Fohanno and Polidori was identified as the best with AAE = 68%, ABE = 52%, MAE = 0.41 W/m2K and MBE = 0.12 W/m2K.

An experimental study of the thermal behavior of bricks integrated with PCM-capsules in building walls

Buildings are the major energy users and by 2035, they will be the fourth largest source of greenhouse gas emissions. Phase change materials (PCMs) are applied to shift the peak-load to the off-peak-load, positively effecting the efficiency of the building. In this paper, an experimental embedding of PCM (Paraffin) with bricks in conventional wall layers is carried out. The effect of this on the thermal diffusion of the inner surface of the wall is studied. Capsules are manufactured to fit the size of the holes inside the bricks and they are filled with Paraffin (147 kJ/kg latent heat, 38oC solidified and 43oC liquidised) and closed in a way that prevents leakage. Each brick contained two rows of holes (5 holes per row). Capsules are placed in the holes at a rate of 5 capsules per brick and 10 capsules per brick. Three wall samples are experimentally tested: traditional wall, wall containing 5 capsules/brick and a wall containing 10 capsules/brick. The indoor test with light intensity has been fixed on 900 W/m2 during the heating period for 4 hours and the remaining period of cooling. The temperature measured and recorded for the internal, external surfaces and the middle of the wall using K-type thermocouples and datalogger. The results indicated that, bricks wall with 10 PCM- capsules per brick reduced the heat flux by 34.17% compared with traditional wall sample, and energy stored 50% more than a wall with 5PCM-capsules per brick. The lowest temperature of the internal wall surface of sample 10 capsules per brick is recorded compared to the reference wall where the difference is more than 3°C.

Thermal and environmental impact analysis of rice husk ash-based mortar as insulating wall plaster

The energy used to maintain the thermal comfort of buildings significantly contributes to the GHG emissions and global warming. In this study, a sustainable and cost-effective rice husk ash (RHA)-based mortar for wall plastering has been developed to provide better thermal insulation, reduce the operational energy and enhance the thermal comfort. Consequently, RHA was partially replaced with the sand in the conventional mortar to produce the RHA-based plaster. Initially, compressive strengths and thermal conductivities of the selected mortar mixes were assessed. The results highlight that the RHA can be replaced up to 30% instead of sand in mortar to produce the thermally enhanced wall plaster. Further, two identical prototype model houses were constructed with RHA-based (i.e. 30% of RHA) and conventional plasters to evaluate their heat transfer, heat flux, and the characteristics of internal and external wall surface temperatures in open weather conditions. It was noted that the average peak heat flux reduction formed by the RHA-based plaster was 10%. The average daily heat transfer reduction across the wall with RHA-based plaster was about 26%. Results also show that RHA-based plaster can reduce the energy that required to maintain thermal comfort by about 9% than the conventional plaster. Moreover, the environmental impact analysis was also conducted to assess the sustainability performance of RHA-based mortars. The environmental impact assessment revealed that the RHA-based plaster has less environmental impact than the conventional mortar. Furthermore, the CO2 emission generated by the production of RHA-based mortar is about 14% less than the conventional plaster.

Understanding Deterioration due to Salt and Ice Crystallization in Scandinavian Massive Brick Masonry

Extensive durability problems such as weathering and degradation are found in historic Scandinavian brick masonry buildings, especially from the neo-Gothic period. These are largely due to the crystallization of salts and frost action in the bricks and mortars. This article aims to show and illustrate which salts and crystals are found in historic brick masonry buildings and to describe their appearance and behavior. An additional aim is to explore possibilities of preventing salt-related damage on internal masonry wall surfaces, such as using hemp-lime sacrificial plaster beneath the plaster. The objective is to show the mechanisms behind salt-related problems and to perform a case study and a laboratory study on salt-damaged brick masonry containing sodium sulphate. In order to prevent and stop damage to the masonry, it is important to be able to identify the nature of the salt damage and the type of salt that caused the damage. Neo-Gothic brick masonry buildings require well-planned, continuous maintenance of the masonry. It is therefore of the utmost importance to have an understanding of the complex functions of the masonry and of the salts that can cause damage to these historic buildings.

Effect of geometrical parameters on entropy generation during R134a boiling flow inside unique internally grooved tubes: Experimental approach

Generally, using heat transfer enhancement techniques in heat exchangers always accompanies frictional pressure drop amplification; entropy generation analysis is a suitable technique to investigate the heat transfer and pressure drop together. In this study, the effects of tube's geometrical parameters and flow conditions on entropy generation during two-phase boiling flow of R134a refrigerant in horizontal internally grooved tubes are experimentally investigated. The experimental tests are conducted in a wide range of operating conditions, including mass flux of 16.5–105 kg/m2s, vapor quality of 0.06–0.98, and heat flux of 3.5–25 kW/m2. Test evaporator tubes are made up of copper of 20 mm inner diameter with nine types of discrete inclined grooves on the tubes' internal wall surface. The results represent that using the grooved tubes is desirable for the majority of test conditions except for mass fluxes between 20 and 80 kg/m2s at vapor qualities higher than about 0.4–0.5. The ratio of groove pitch length to groove width within the geometrical parameters has the most notable effect on the total entropy generation. Besides, a new correlation is developed for entropy generation of R134a evaporating flow inside internally grooved tubes with discrete inclined grooves.

Dehydration of lithium dihydrogenphosphate in a ball‐mill rotary‐kiln (BaMRoK) reactor

AbstractLithium dihydrogenphosphate (LHP) needs to be dehydrated to be safely applied for the melt casting process to produce lithium iron phosphate (LFP). The dehydration reaction consists of several consecutive melting, oligomerization, and crystallization steps resulting in a solid product stuck to the reaction vessel at around 400°C. Here we applied an electrical shell‐heated rotary kiln containing grinding media (ball‐mill rotary‐kiln, BaMRoK) to dehydrate LHP at 400°C and recover the ground product without needing any extra processing. The bulk convective heat transfer coefficient of the kiln has been calculated in the presence of the grinding media and the temperature profile has been modelled using COMSOL Multiphysics. The kinetic model of the reaction from thermogravimetric analysis (TGA) and the thermal profile suggest that the dehydration reaction mostly happens on the internal surface of the BaMRoK wall.