Diffusions of multiple components have numerous applications such as underground water flow

pollutant movement

stratospheric warming

and food processing. Particularly

liquid hydrogen is used in the cooling process of the aeroplane. Further

liquid nitrogen can find applications in cooling equipment or electronic devices

i.e

.

high temperature superconducting (HTS) cables. So

herein

we have analysed the entropy generation (EG)

nonlinear thermal radiation and unsteady (time-dependent) nature of the flow on quadratic combined convective flow over a permeable slender cylinder with diffusions of liquid hydrogen and nitrogen. The governing equations for flow and heat transfer characteristics are expressed in terms of nonlinear coupled partial differential equations. The solutions of these equations are attempted numerically by employing the quasilinearization technique with the implicit finite difference approximation. It is found that EG is minimum for double diffusion (liquid hydrogen and heat diffusion) than triple diffusion (diffusion of liquid hydrogen

nitrogen and heat). The enhancing values of the radiation parameter

R

d

and temperature ratio

θ

w

augment the fluid temperature for steady and unsteady cases as well as the local Nusselt number. Because

the fluid absorbs the heat energy released due to radiation

and in turn releases the heat energy from the cylinder to the surrounding surface.