The knowledge related to the methodology of the FIELD trial study as a type of intervention studies, yet for many of our researchers is not fully understood. The aim of the current study was a better understanding of conducting this type of research. FIELD trial studies are done on healthy individuals and aim to prevent. These types of studies such as clinical trials are performed on both individual and collective levels. One type of these studies is Community Intervention Trial which is usually done on a large scale population. FIELD trial study should be carried out in stages, such as the formulation of hypotheses, selection of the population (reference population, study population, and sampling), measuring the baseline variables (before conducting preventive intervention), random allocation of subjects to intervention and control groups, doing interventions and measuring outcome. The methodology of FIELD trial studies is very similar to clinical trials. The difference is that FIELD trials are conducted on healthy individuals and aim to prevent and also the sample size required to this type of study is relatively more, and these studies are usually time consuming and costly.

This study aimed to investigate the HEAT transfer of water/Fe3O4 nanofluid in a square cross-sectional channel with dimensions of 80 cm ⨯1 cm ⨯1 cm under the influence of a uniform HEAT flux perpendicular to the laminar flow of ferrofluid in the presence of a magnetic FIELD. Firstly, the production of ferrofluid with concentrations of 0.5 vol.% and 1vol.%, their quality, and the quality of the production method was investigated. The results of zeta potential and vibrating-sample magnetometer tests show the good quality and stability of the produced ferrofluid. The thermophysical properties of the made ferrofluid are compared and evaluated with existing experimental correlations. The HEAT transfer of the produced ferrofluids under the influence of HEAT fluxes of 134-546 Watts is investigated in the absence of an external magnetic FIELD. Then, the effect of the external magnetic FIELD on the HEAT transfer at 0.5 vol.%, under the influence of a total HEAT flux of 1258.2 Watts is investigated. The magnitude of increase of HEAT transfer coefficient compared to pure water, without external FIELD, for ferrofluid with 1 vol.%, under total HEAT fluxes of 134, 545, and 321.3 Watts, are 30%, 48%, and 38% respectively. At a HEAT flux of 1258.2 Watts, the HEAT transfer coefficient in the presence of an external magnetic FIELD increases by 3.16% at 0.5 vol.% compared to the absence of a magnetic FIELD.

The aim of the present numerical investigation is to analyze the effects of transverse magnetic FIELD on HEAT transfer and fluid flow characteristics in a rectangular microchannel HEAT sink (MCHS). The effects of Hartmann number, channel aspect ratio, total channel height and total channel width on HEAT transfer and fluid flow characteristics are widely investigated. The governing equations for three-dimensional steady, laminar flow and conjugate HEAT transfer of a microchannel are solved using the finite volume method. The obtained results are discussed with various combinations of pertinent parameters involved in the study. The results reveal that magnetic FIELD can enhance the thermal performance of the MCHS but it is accompanied with a slight increase in pressure drop.

Research study presents an experimental investigation on forced convection HEAT transfer of an aqueous ferro-fluid flow passing through a circular copper tube in the presence of an alternating magnetic FIELD. The flow passes through the tube under a uniform HEAT flux and laminar flow conditions. The primary objective was to intensify the particle migration and disturbance of the boundary layer by utilizing the magnetic FIELD effect on the nanoparticles for more HEAT transfer enhancement. Complicated convection regimes caused by interactions between magnetic nanoparticles under various conditions were studied. The process of HEAT transfer was examined with different volume concentrations and under different frequencies of the applied magnetic FIELD in detail. The convective HEAT transfer coefficient for distilled water and ferro-fluid was measured and compared under various conditions. The results showed that applying an alternating magnetic FIELD can enhance the convective HEAT transfer rate. The effects of magnetic FIELD, volume concentration and Reynolds number on the convective HEAT transfer coefficient were widely investigated, and the optimum conditions were obtained. Increasing the alternating magnetic FIELD frequency and the volume fraction led to better HEAT transfer enhancement. The effect of the magnetic FIELD in low Reynolds numbers was higher, and a maximum of 27.6% enhancement in the convection HEAT transfer was observed.

Increasing the HEAT transfer rate in various industries in order to improve the efficiency of equipment, prevent damage to parts and reduce costs is one of the essential discussions in the industry. One of the solutions to increase HEAT transfer is the use of active HEAT sink. In this research, an active HEAT sink with Galinsten liquid metal fluid was used and the discretization of Navier-stokes equations was done using the second order upstream finite volume method. The effect of applying the magnetic FIELD in the Y direction (perpendicular to the flow axis) to the HEAT sink has caused the creation of a force against the flow direction called the Lorentz force, which has caused the M-shaped velocity distribution. According to the constant flux boundary condition, increasing the flow velocity in the vicinity of the walls has caused the surface temperature to decrease and the HEAT transfer to improve. The results showed that the effect of applying a uniform external magnetic FIELD in both Y and X directions with a Hartmann number of 517 improved the Nusselt number by 38% and 13%, respectively, compared to a Hartmann number of zero. The effect of applying a magnetic FIELD in the Y direction to the HEAT well with a Hartmann number of 517, 38%, Hartmann number of 258, 22% and Hartmann number of 129, 13% has improved the HEAT transfer.

In this paper, multi-objective optimization (MOO) of HEAT transfer and flow FIELD in cross-flow HEAT exchangers with triangular and square arrangement is performed using Computational Fluid Dynamics (CFD) techniques and Non-dominated Sorting Genetic Algorithms (NSGA II). At first, fluid flow is solved numerically in 150 various HEAT exchanger using CFD techniques. Finally, the CFD data will be used for Pareto based multi-objective optimization of fluid flow in cross flow HEAT exchanger using NSGA II algorithm. In the MOO process there are two geometrical parameters and the conflicting objective functions are to simultaneously maximize the amount of HEAT transfer and minimize the pressure drop. The Pareto front including optimum design variables and objective functions for two triangular and square HEAT exchangers are shown in results. It is shown that the achieved Pareto solution includes important design information on fluid flow in the HEAT exchangers.