In this work, the effect of various parameters involved in the design of a natural convection micropump using density-based topology optimization are studied. The motion of fluid in a natural convection micropump is caused by the differential heating of the walls. The problem is modeled as a conjugate heat transfer problem. The goal is to determine the fluid flow path within design domain to maximize the flow rate in the system. A steady-state, laminar, incompressible flow is assumed, with the coupled Navier-Stokes equations and convection-diffusion equations solved using the Boussinesq approximation. Various interpolation schemes for material properties in density-based topology optimization methods, such as RAMP, SIMP, and sigmoid functions, are tested and compared for the micropump problem. Use of projection schemes, along with the parameters used in them, are examined. The problem is analyzed for varying Grashof numbers, Prandtl numbers and channel width, with particular attention given to the challenges associated with higher Grashof numbers