where we approximated the density difference for a fluid of average mass density , thermal expansion coefficient and a temperature difference across distance .
wHere we approxiMated tHe deNsitY differeNcE fOr a fLuID of averAGE MASs DENsity , tHErmaL expaNSion CoeffICient AND A TEmperatUre diFfEreNCE across DisTance 