The first step in designing cooling-heating systems is to calculate the refrigerant-thermal load for the desired space. After this stage, in order to provide the refrigerant-thermal load, the required system flow rate must be calculated and the appropriate tube size is calculated based on the allowable head loss. In this program, the cooling system (10 ° C) and the heating system (60 ° C) are used to determine the head loss and the pipe size. The necessity of taking into account head loss in designing of cooling and heating systems is due to the fact that the performance of these systems outside of this range will reduces the efficiency and ultimately reduces the lifetime of the system. The permissible head loss across all cooling and heating systems is 3 to 3.5 feet per 100 feet of pipe (0.35-0.30 meter of water per pipe meter). The basis of the calculation of the head loss, is roughness and the diameter of the inner tubes of different sizes.