From previously, the perpendicular temperature field due to temperature particles distributed over a surface is,
pd=TE=ρTτo
where ρT is the temperature charge density per unit area, τo is the analogue to εo.
The force on a temperature charge, T− due to two temperature charge distributions, between a hot and cold surface is,
T−.(pdh−pdc)=mTdvdt
where mT is the mass of the temperature charge. Over a contact surface, Ac,
T−∫Acpdh−pdcdA=T−∫Acρhτh−ρcτcdA=∫AcmT(A)dvdtdA
where mT(A) is the area mass distribution of the temperature charge in area Ac. When we consider an area the size of one temperature charge, AT,
T−mT∫ATρhτh−ρcτcdA=∫ATdvdtdA
ATT−mT(ρhτh−ρcτc)=dvdtAT
When we replace, ρh with T−ρn,
ρ=T−.ρn
where ρn is the number density of temperature particle per unit area, the velocity of one temperature charge crossing from the hot body to the cold body is,
dvdt=(T−)2mT(ρnhτh−ρncτc)
At thermal equilibrium,
dvdt=0⟹ρnhτh=ρncτc --- (*)
Only if both the hot and cold bodies are of the same material, in particular,
τh=τc then,
ρnh=ρnc
If everything attain the same temperature on thermal contact at equilibrium, then there cannot be any sort of thermal insulation. Expression (*) allows for materials of different τ to attain different ρn.
This points to ρn, the surface area number density of temperature particles as the temperature we measure with a contact thermometer.