This paper examines the heat absorption fluid on natural convection flow in a vertical concentric annulus under a radial applied magnetic field. Exact solution momentum and energy equation are solved. The aim is to see the influence of each governing parameter on dimensionless velocity, temperature, volume flow rate, rate of heat transfer, skin friction and bulk temperature are discussed. During the course of the numerical computation, it is observed that the role of the heat sink parameter is to reduce the velocity and temperature of the fluid but increase the critical value of the annular gap. It is also found that the magnitude of the maximum value of the temperature and velocity is greater in the case of isothermal condition when compared with constant heat flux when the annular gap of the cylinder is less than or equal to 1.87, while the reverse trend occurs when annular gap of the cylinder is greater than 1.87.

Keywords: Natural convection, heat absorption fluid, annulus, magnetic field.