Abstarct: One of the challenges that the world is facing is supply of fresh water. nowadays the increase of population and industrialization, more cities and countries, the demand for fresh water is increasing too. Desalination of seawater is one of the most important processes for producing water demand. Among the various methods of desalination, HumidificationDehumidification has some advantages such as the use of low temperature energy sources and use in low water production capacities. This type of desalinator consists of two main units, humidifier and dehumidifier. The condensing unit of this type of desalination plant has always been studied and researched due to saline water in order to reduce its related problems, especially during operation; Therefore, in this research, first the process of humidification and dehumidification is described and then the modeling of this desalination plant has been done by considering two different modes of dehumidification, direct contact and indirect contact in MATLAB software. Validation of the two main parts of the model was performed using existing data. Then the effect of basic parameters on freshwater production in both systems was investigated. Modeling and analysis of this system has been done using the laws of thermodynamics and mass and heat in different parts of the desalination unit. In the next step, according to the costs considered for the capital cost and operation cost, including energy costs and maintenance, the two condenser models were compared from an economic point of view. In the end, it was found that considering the cost and amount of fresh water production, fresh water with indirect contact with the condenser has a higher cost for design and construction and production per cubic meter of fresh water is about 383715 Rials, but the amount of fresh water production per year is estimated at 375 cubic meters. But in direct desalination condenser has a lower cost for construction and therefore less production with the same conditions, so that the cost of production per cubic meter of fresh water is about 328820 Rials and the amount of fresh water production per year is estimated at 325 cubic meters. By comparing these two cases, it can be said that with the superiority of the need for fresh water production over the cost of the indirect contact condenser, and conversely to reduce production costs per cubic meter of fresh water, the total annual production will be lower.