Dissolution of solid grains in a porous medium is important in many applications, such as groundwater transport, carbon storage, mineral systems, formation of geologic features, and enhancement of near-wellbore permeability in carbonate reservoirs. Many models for dissolution in porous media are continuum-scale descriptions, but the flow, reactive transport, and subsequent increase in porosity and permeability occur at the pore scale. Thus, proper inclusion of parametric inputs is challenging. We present a single-phase, 3D, pore network model of dissolution for porous media in the mass-transfer-limited regime. A novel mass transfer coefficient correlation and pore-merging criterion are developed from finite element simulations that greatly improve the pore-scale physics and the quantitative accuracy of the network. The optimal Damkohler number determined from our network simulations closely matches the optimum of 0.29 reported experimentally for mass transfer dissolution in porous media.