Microscopic mechanisms of externally controlled reversable heat flow through the carbon nanotube junctions (NJ) are studied theoretically. Our model suggests that the heat is transfered along the tube section T by electrons (e) and holes (h) moving ballistically in either in parallel or in opposite directions and accelerated by the bias source-drain voltage VSD (Peltier effect). We compute the Seebeck coefficient α, electric σ and thermal κ conductivities and find that their magnitudes strongly depend on VSD and VG. The sign reversal of α versus the sign of VG formerly observed experimentally is interpreted in this work in terms of so-called chiral tunneling phenomena (Klein paradox).PACS numbers: 73.23. Hk, 73.63.Kv, 73.40.Gk Physics of the heat transfer determines functionality, precision and effectiveness of solid state nanocoolers [1,2,3,5] which are environment friendly and have a lot of applications in the experimental physics, nanoelectronics, chemistry, industry and medicine. Therefore exploiting of new thermoelectric materials with high figures of merit Z · T (T being the temperature) attracts a lot of attention. Recently such interest arose toward the carbon nanotube and graphene junctions which electronic properties are highly unconventional [5]. The thermoelectric power experiments [5] addressed single wall carbon nanotube junctions. In Ref.[5] a temperature difference ∆T induced a finite bias voltage ∆V p across the junction which sign changed versus the gate voltage V G . A question here is how that unconventional thermoelectric behavior is related to the intrinsic nature of the carbon nanotube and graphene? It is widely accepted that the charge carrier motion in carbon nanotubes and in graphene is essentially phase-correllated. For such a reason the conducting electrons and holes in that materials behave as relativistic massless 'chiral fermions' (CF) characterized by a 'pseudospin' (see review [6] and references thereis).In this Letter we argue that the phase-correlated thermoelectric transport of charge carriers implicates a voltage-controlled and reversable heat flow through the single wall carbon nanotube junctions (Peltier effect). The enhancement of Z · T in those 1D devices where the charge carriers propagate ballistically occurs due to strong van Hove singularities (VHS). The VHS position is tuned by the gate voltage V G in respect to the Fermi level ε F of the electrodes. When an VHS and ε F match each other, it results in a sufficient density of charge carriers which contribute to the electric conductivity despite the Fermi energy itself is relatively small. A finite gate voltage V G = 0 is not just merely supplies either the electrons or holes into T , but rather creates a potential barrier (U 0 > 0) or well (U 0 < 0) for chiral fermions transmitted across the junction as illustarted in Figs across the junction tilts the chiral barrier and causes the electric charge carriers to accelerate. This means that the energy of the charge carriers changes by δ = eV SD , which inflicts a local...