An electrohydrodynamic evaporator device (EHD) has an EHD electrode. An electric field is generated upon a fluid of low conductivity inside the evaporator device and an enhanced thermal transport effect is then achieved since a thermal boundary layer near a thermal transport surface is caused to have a greater perturbation while a very small voltage drop. With the EHD utilized, size, weight, cost and required refrigerant amount of the evaporator device are reduced. Further, thermal transport efficiency of the alternative refrigerant is improved, making the EHD evaporator device in compliance with associated refrigerant regulations made by CFC and achieve the purposes of environmental protection and energy saving.