A thermal lattice Boltzmann method has been applied to simulate gas-solid heat transfer in a random assembly of spheres using an immersed moving boundary approach. The numerical data was correlated to propose an expression for the Nusselt number as a function of the Reynolds number and solid volume fraction over a wide range of solid volume fractions (phi = [0, 0.5]) for Reynolds numbers up to 100. It is hoped that the new Nusselt number correlation for gas-solid systems improves the accuracy of Euler-Euler and Euler-Lagrangian simulations of gas-solid heat transfer in packed and fluidized beds.