Correlations between multiplicity of charge particles and mean transverse momentum was observed experimentally in p + p collisions from top SPS energy to LHC energy. The change of the correlation function’s shape with collision energy was successfully described by the multi-pomeron exchange model as an interplay of string fusion and energy-momentum conservation. The situation at lower collision energies where role of resonance decays would increase can be studied by the NA61/SHINE experiment at SPS and by the forthcoming MPD experiment at NICA. In prior to the experimental analysis the phenomenon was studied using Monte Carlo event generators. In this contribution Monte-Carlo simulations results will be presented for the pt-n correlation function. The role of limited experimental acceptances of NA61/SHINE and MPD facilities will be discussed.