Impact of low-temperature electrical resistance heating on subsurface flow and transport

The effects of subboiling electrical resistance heating (ERH) on subsurface flow and transport were examined in a series of two‐dimensional tank experiments, with temperatures reaching 50°C. To analyze the experiments and determine the dominant mechanisms affecting flow and transport, a fully coupled two‐dimensional finite difference electrothermal model was developed to simulate electrical current flow, temperature‐dependent fluid flow, and mass transport. The model incorporates temperature‐dependent equations for density, viscosity, diffusion coefficient, and electrical conductivity, capturing the nonisothermal processes dominant in the subsurface. The model was validated with laboratory‐scale experiments in which voltage distribution, instantaneous electrical power, temperature, and tracer transport were measured. Tracer experiments and transport modeling indicated that temperature‐induced buoyant flow and contaminant movement could be significant when applying ERH in the subsurface, even at 50°C. A sensitivity study was performed to assess the impact of including temperature‐dependent properties such as water density, viscosity, and electrical conductivity. A change in water density of 1.3% (at 50°C) resulted in buoyant flow and increased velocity through the heated zone, indicating that heating contaminated zones to 50°C can have a large impact on mass transport. Temperature‐dependent electrical conductivity had a direct impact on ERH power consumption as well as the time to reach desired temperatures. Key Points A 2D model for ERH was developed and validated with experimental data Buoyant flow produced by low temperature ERH can impact contaminant transport Temperature dependent EC and density is critical when modeling ERH