Heat exchangers are often subjected to increasing demands on their efficiency with a reduced volumetric footprint. With the advancement in additive manufacturing technologies, topology optimization can be a viable strategy to derive novel designs to improve product performance. Topology optimization has been vastly investigated in the past few decades for structural designs. In this presentation, a thermo-flow topology optimization workflow was developed for heat exchanger applications which performs a multi-physics analysis (e.g. with coupled flow dynamics and heat transfer). In the thermo-flow topology optimization workflow, thermo-flow solver in STAR-CCM+ was utilized to evaluate thermal and flow performance metrics. Adjoint sensitivity was computed with the adjoint solver based on a defined objective function. The adjoint sensitivity was then used as an input to a method of moving asymptotes (MMA) optimizer to identify new designs. This integrated workflow is demonstrated through the design optimization for application to heat exchangers with single phase fluids in a dual flow arrangement. The multi-physics topology optimization enables objectives of different physics to be evaluated in a single optimization run. The major complicating factor compared to earlier optimization work on the gas turbine components, is the dual flow character of the problem that requires optimization on both sides of the heat exchanger. Future efforts on several individual flows involved in the heat exchange problem, as well as single phase versus two-phase flow phenomena will be discussed.