The　LBM　is　used　to　investigate　three-dimensional　nanofluid　(NFs)　flow　inside　a　square　enclosure　with　a　heat　source　in　this　research.　The　heat　source　is　located　in　the　enclosure＇s　middle　and　operates　at　a　high　temperature.　The　sidewalls　have　a　thickness,　leading　to　heat　transfer　(HE-TR)　from　the　sidewalls　that　are　at　low　temperatures　to　the　internal　fluid　due　to　their　thermal　conductivity.　An　inclined　magnetic　field　(MF)　uniformly　affects　the　fluid　flow.　The　effect　of　parameters　such　as　Rayleigh　number　(Ra),　thickness　and　thermal　conductivity　of　the　sidewall,　dimensions　of　the　heat　source,　Hartmann　number　(Ha),　the　volume　fraction　of　nanoparticles　(phi),　and　the　angle　of　the　MF　on　two-　and　three-dimensional　field　flow　and　HE-TR　is　investigated.　Optimization　is　made　on　the　parameters　for　maximum　HE-TR.　The　lattice　Boltzmann　method　has　been　used　to　simulate　nanofluid　flow.　The　results　show　that　an　enhancement　in　the　Ha　and　the　angle　of　the　MF　reduces　the　amount　of　HE-TR.　HE-TR　is　improved　by　increasing　the　thermal　conductivity　of　thick　walls.　The　quantity　of　HE-TR　is　increased　when　nanoparticles　are　added　to　water.