As thermal power plants are one of the basic and important sections in the industry of every country, investigation and simulation of different sections of a power plant aiming their improvement of performance and increase of efficiency seem essential, condensers and cooling towers, as important parts of each power plant, are not exceptions to this generalization. One of the methods of cooling the coolants used in power plants’ condensers is using dry cooling towers. Increase in wind velocity as well as increase in ambient temperature results in decrease in efficiency of dry cooling tower. In conditions with high temperature, one of the methods of increasing the efficiency of dry cooling towers is using the water spray in order to decrease the temperature of the inlet air flow to the exchanger. The water is spattered between radiator and louvers tower by the specific water sprayers which are setup near the tower. The passing air flow is cooled by little drops of water and inters into the radiator and decreases the temperature of outlet water. The present work has studied the previous investigations and also tried to precisely model and simulate working conditions of Heller-type cooling towers using Gambit and Fluent softwares. In the present research, the second order upwind scheme was used for discretization of the governing equatio PRESTO! state was used to solve pressure equation; the implicit method was used for linearization of the equatio the SIMPLE algorithm was used for simultaneous solving of velocity and pressure equatio the standard k— turbulence model was used for the turbulence flow; Radiator model was used for simulation of the heat exchangers located around the tower; and finally, Solid cone model was used for water spray modeling. In the present work, Heller-type dry cooling towers of Isfahan’s Shahid Mohammad Montazeri thermal power plant were simulated. Inside and outside of tower was simulated in conditions with both presence and absence of wind. Next, contours of temperature, pressure and velocity were analyzed. The cooling tower was simulated in different ambient temperatures. Also, effect of increase of ambient temperature on the efficiency of the cooling tower in ambient temperatures of 306.35 k and 312 k with and without spray was studied. Effects of water spray in different flow rate and different diameters of droplets were studied. The effect of simultaneous presence of wind and water spray in different flow rates and also the effect of nozzle distance to the radiator on the efficiency of the cooling tower were studied numerically. Temperature of water spray was maintained constant at 298.15k. There was a good agreement betwee between experimental results and the numerical results adopted in current work in absence-of-wind condition. Water spraying increase the average of evaporation rate, relative humidity, rate of heat transfer and difference of flow temperature between radiator’s inlet and outlet but decreases the mass fraction air on the radiator. The optimumdistance between nozzles and the radiator is 2.5 m. Optimal mass flow rate of water spray is 179.2 m 3 /hr. In flow rate of water spray equal to 183 kg/s (2.57 percent inlet water to tower) and velocity of wind equal to 2.8 m/s, the rate of heat transfer on the radiator increases by 30.23 percent compared with the condition without water spray. Keywords: Heller-Type Dry Cooling Tower, Numerical Simulation, Water Spray, Efficiency of Cooling Tower, Fluent, Radiator Model, Solid Cone Spray Model