  Non-equilibrium dynamics for relativistic fluid or quark gluon plasma (QGP)
have already been calculated earlier upto third order using both kinetic and
thermodynamic approaches. Calculations presented in this manuscript are based
on thermodynamics principles. The expressions for third order dissipative
fluxes have been derived from equation for entropy 4-current developed earlier
by A. Muronga. The relaxation equations in the present work have been developed
in a simple Bjorken (1+1)D scenario and Eckart frame. The relaxation equations
are found to have slightly different values for the coupling coefficients as
compared to calculations from earlier models. The solutions to the differential
equations have been found to be sensitive to values of these coefficients. The
shear relaxation equations derived in third order theory are discussed term by
term. Effects of third order theory on shear relaxation time has been
discussed. Thermodynamic quantities related to hot and dense matter have been
calculated as functions of proper time. Moreover, various initial conditions
for the relaxation equations have been assumed to study their effects on above
mentioned observables. A LHC QGP formation time of $\tau_0$ = 0.4 fm/c and
temperature of T$_0$ = 500 MeV have been assumed.
