Assessing the effect of barns structures and environmental conditions in dairy cattle farms monitored in Northern Italy

Animal welfare is a fundamental pillar for livestock farming, and it can be endangered by a series of aspects, among which is the presence of undesired microclimates. This condition can be monitored by measuring the temperature-humidity index (THI), an index able to inform about the emergence of heat-stressing conditions in the barns. The THI can be influenced by the external environmental conditions and the barn structure, orientation, thermal buoyancy, and roof insulating materials. In order to evaluate these structural aspects of buildings and the consequent microclimate, in this study, a survey was carried out in 8 dairy cattle barns located in the northern part of Italy that were monitored continuously during thermoneutral, warm, and cold periods. Experts observed the structural aspects ,and the environmental parameters were measured with sensors. From the results emerged that the barns had structural characteristics that considerably affect the internal microclimate, with openings, roof height, forced ventilation, and building orientation playing a significant role in estimating of the THI in the barn. The more critical period was the warm one when the structures could not mitigate the external conditions, and THI exceeded the threshold of 72 for a big share of the period in all monitored farms (range between 50-80% of observations). In the best situation, the cooling systems were able to maintain the external conditions. The results confirm the importance of the barn design and of an appropriate ventilation to improve air exchanges.

Nanofluidic thermal-fluid transport in a split-driven porous system working under a magnetic environment

Purpose This study aims to focus on a thermo-fluid flow in a partially driven cavity (PDC) using Cu-water nanoliquid, magnetic field and porous substance. The cooling and sliding motion are applied on the upper half of the vertical walls and the bottom wall is heated. Thermal characteristics are explored to understand magnetohydrodynamic convection in a nanoliquid filled porous system from a fundamental viewpoint. The governing parameters involved to cater to the moving speed of the sidewalls and partial translation direction are the relative strength of thermal buoyancy, porous substance permeability, magnetic field intensity, nanoparticle suspension and orientation of the cavity. Design/methodology/approach The coupled transport equations of the problem are solved using an in-house developed finite volume-based computing code. The staggered nonuniform grids along the x and y directions are used. The SIMPLE algorithm technique is considered for the iterative solution of the discretized equations with the convergence check of the continuity mass defect below 10–10. Findings The present study unveils that the heat transfer enhances at higher Ri with the increasing value of Re, irrespective of the presence of a porous substance or magnetic field or the concentration of nanofluid. Apart from different flow controlling parameters, the wall motions have a significant contribution to the formation of flow vortices and corresponding heat transfer. Orientation of the cavity significantly alters the transport process within the cavity. The upward wall velocity for both the sidewalls could be a better choice to enhance the high heat transfer (approximately 88.39% at Richardson and Reynolds numbers, respectively, 0.1 and 200). Research limitations/implications Considering other multi-physical scenarios like porous layers, conducting block, microorganisms and the present investigation could be further extended to analyze a problem of complex flow physics. Practical implications In this study, the concept of partially driven wall motion has been adopted under the Cu-water nanoliquid, magnetic field, porous substance and oblique enclosure. All the involved flow-controlling parameters have been experimented with under a wide parametric range and associated thermo-flow physics are analyzed in detail. This outcome of this study can be very significant for designing as well as controlling thermal devices. Originality/value The convective process in a partially driven cavity (PDC) with the porous medium has not been investigated in detail considering the multi-physical scenarios. Thus, the present effort is motivated to explore the thermal convection in such an oblique enclosure. The enclosure is heated at its bottom and has partially moving-wall cold walls. It consists of various multi-physical conditions like porous structure, magnetic field, Cu–H2O nanoliquid, etc. The system performance is addressed under different significant variables such as Richardson number, Reynolds number, Darcy number, Hartmann number, nanoliquid concentration and orientation of cavity.

Moisture safety in ventilated cathedral roofs

Cathedral roofs are commonly used when constructing small houses in Sweden. In contrast to roof constructions with a cold attic, where frequent moisture damage has been noted, the cathedral roof is difficult to access for inspection. Furthermore, Swedish building regulations sets high demands regarding moisture safety, although there are no clear guidelines for their compliance. Hence, designing a cathedral roof must be done with great care. Previous studies investigating moisture safety in cathedral roofs, applies a constant air exchange in the ventilated air cavity. In this study a cathedral roof, ventilated from eave to eave, was analysed by examining the relevance of considering the variation in cavity air flow when conducting coupled heat and moisture calculations. The varied cavity air flow was calculated in an air flow model, considering wind and thermal buoyancy as driving forces. The accuracy of moisture safety assessments using the MRD model via hygrothermal calculations in WUFI Pro were also studied. Comparing moisture calculations with measurements showed high similarity when using a model with constant cavity air flow, and even higher resemblance when using a model with varied air flow. When actual conditions are sought, the study indicated that pinpointing important parameters, such as initial moisture content and moisture related material properties, would further increase precision in moisture calculations.

Augmentation of heat transfer via nanofluids in duct flows using Fourier-type conditions: Theoretical and numerical study

Motivated by developments in thermal duct processing, an investigation is presented to study the behavior of viscous nanoparticle suspensions flowing in a vertical duct subject to Fourier-type conditions. The left wall temperature is kept lower than that of the right wall. Brownian motion and thermophoresis which are invoked via the presence of nanoparticles are incorporated in the study. Numerical solutions with an efficient Runge–Kutta shooting method are also presented at all values of the control parameters. The impact of thermal Grashof number [Formula: see text], Eckert number [Formula: see text], thermophoresis [Formula: see text], and Brownian motion parameters [Formula: see text] on the velocity, temperature, and nanoparticle concentration distributions for identical [Formula: see text] and differing Biot numbers [Formula: see text] (at the duct walls) are computed and visualized graphically. With vanishing thermophoresis and Brownian motion parameters, the solutions match exactly with the earlier Newtonian viscous flow computations. Symmetric and asymmetric wall heat conditions are also acknowledged. Intensifying the thermal Grashof number, Eckert number, thermophoresis parameter, and Brownian parameter serve to amplify magnitudes of the velocity and temperature, whereas the nanoparticle concentration field is suppressed. The skin friction and Sherwood number are also computed with various combinations of the flow control parameters. Nusselt number values at the hot duct wall are enhanced with an increase in thermal buoyancy parameter, Eckert number, Brownian motion parameter, and thermophoresis parameter for equal Biot numbers. The opposite trend is computed for different Biot numbers. For any given values of Biot numbers, the mean velocity and bulk temperature are boosted with increase in thermal buoyancy parameter, Eckert number, Brownian motion parameter, and thermophoresis parameter. Hence, it may be inferred that the transport characteristics computed using Fourier-type boundary conditions are substantially different from those based on isothermal boundary conditions in nanofluid duct flows.

Impact of gap-ratios on buoyancy-assisted mixed convection flow and heat transfer in unconfined framework with two side-by-side cylinders

An analysis has been carried out to understand the consequences of side-by-side gap-ratio on thermal buoyancy-assisted two-dimensional flow past a pair of heated circular cylinders for a dominant viscous flow field. This is implemented through studies at Reynolds number ( Re) ranging from 5 to 40, Prandtl number ( Pr) 0.7, gap-ratio ( T/D) 1.5 to 4 and Richardson number ( Ri) 0 to 1. An ANSYS-based incompressible flow solver is used with Boussinesq approximation to account for density variations in the momentum equation. One can realize features like the steady-separated and steady-unseparated flow on varying flow and thermal parameters. Unlike streamlines, non-interacting isotherms are non-existent in the current numerical framework. The influence of gap-ratio on enhancement in Nusselt number ( Nu) is the best realized at T/D = 1.5 and buoyancy-aided effects play a dominant role for enhancement in Nu at diffusion and/or viscous-dominant conditions occurring at Re = 5. Correlations are developed to quantify the impact of T/D, Re, and Richardson number Ri on Nu. For the first time, Nu’s correlation based on varying side-by-side gap-ratio has been stated in a single expression. Finally, a comparison for the heat transfer enhancement/reduction in Nu under a similar numerical framework is provided with cases of high-Pr flow and/or different relatable flow arrangements for circular and square cylinders.

Analysis of the thermo-fluidic transport around counter-rotating tandem circular cylinders

The work physically relates to the influence of thermal buoyancy on the flow and heat transfer of an incompressible fluid around two counter-rotating circular cylinders arranged in tandem configuration within an unconfined domain. Two-dimensional numerical simulations are conducted using a finite volume based computational fluid dynamics tool to explore the problem. The Reynolds number is taken as 100 with Prandtl number 0.71, keeping the non-dimensional spacing between the cylinders fixed at 1.5. The cylinder rotations are considered in the range of a dimensionless speed of 0 to 5. The upstream cylinder is rotating in the clockwise sense, whereas, the downstream one in the counter-clockwise sense. The buoyancy effect is analyzed for the Richardson number range 0 to 1. The flow is unsteady periodic characterized by vortex shedding around the stationary cylinders at the chosen value of the Reynolds number. The flow shows unsteadiness with vortex shedding initially with increasing rotational speed; however, at a critical value of the rotation, the flow becomes stabilized with suppression of vortex shedding. On the contrary, the cross thermal buoyancy effect destabilizes the flow into an unsteady periodic pattern. This complex interplay among the free stream flow, cross buoyancy, and counter-rotation produces intriguing fluid dynamic and thermal phenomena. The critical rotational speeds for the range of Richardson numbers are obtained as [Formula: see text] respectively for Ri = 0, 0.25, 0.5 and 1. A corresponding regime diagram is also constructed to depict the unsteady and steady zones of operation.

A review of airflow rate estimation techniques for natural ventilation in buildings

As natural ventilation involves local and global interactions, the estimation of these interactions can be performed by many approaches. Such approaches, rather more experimental and numerical than analytical, often require a great deal of instrumentation and equipment, which results in higher demands on project budget and funding. The present work is devoted to comprehending the natural ventilation concept, and to assess the existing experimental techniques already implemented for past researchers in the estimation of the ventilation airflow rate due to the wind and thermal buoyancy effects. A brief review of modeling techniques is also presented. This will provide a strong theoretical grasp of the natural ventilation process as part of the main elements in the thermal behavior of buildings. Ultimately, these bases are intended to help choose the most suitable techniques to estimate the natural ventilation airflow rate. The adequate benefit-to-budget technique appears to be the airtightness tests (blower door tests), since empirical Equations relating the airflow directly to the pressure difference in the building for both cases: infiltrations (openings closed) and openings opened, can be obtained. Also, the location of the leakages can be identified without complications, and this technique has the potential to estimate in situ the airflow capacity and friction characteristics of the openings.