Thermopneumatic micropump is one type of positive displacement micropump, which has many applications due to its relatively large stroke volume, low working voltage, and simple fabrication in microscale. In this paper, a numerical study of heat transfer and fluid flow in a valveless thermopneumatically driven micropump is presented. For rectifying the bidirectional flow, a nozzle and a diffuser are used as the inlet and outlet channels of the chamber. Since the fluid flow is induced by the motion of a diaphragm, the numerical simulation includes fluid structure interaction, which requires applying a dynamic mesh. The domain of solution is divided into two sections; the actuator unit, which contains the secondary fluid, and the main chamber through which the working fluid is passing. The temperature distribution, the pressure variations, and the center deflection of the diaphragm are obtained. In order to validate the model, the numerical results are compared with some experimental data, which shows fair consistency. According to the results of the three dimensional simulation, the rectification efficiency for the nozzle and diffuser channels depends on the frequency.
