A heat exchanger comprising: a first flow path positioned between an air intake and an air discharge outlet of the heat exchanger; a second flow path between an air intake and an air discharge outlet of the heat exchanger; a fluid conduit comprising: a first cooling region positioned within the first flow path; and a second cooling region positioned within the second flow path; an airflow generator (106, 107) configured to move air through the first and second flow paths; at least one dispenser comprising a first dispenser positioned within the first airflow path to dispense evaporative fluid on the first cooling region and a second dispenser positioned within the second airflow path to dispense evaporative fluid on the second fluid region, wherein each of the first and second dispensers are configured to operate in a wet mode whereby the dispenser dispenses evaporative liquid and a dry mode whereby the dispenser does not dispense evaporative fluid; and a controller in communication with the airflow generator (106, 107) and the dispenser, characterised in that the controller is configured to regulate airflow through the first flow path and the second flow path, and wherein the controller is configured to set the dispensing mode of the at least one dispenser, wherein the controller is configured so that the dispense mode of the first dispenser can be set independently of the dispense mode of the second dispenser, wherein the first and second dispensers can thus be operated both in a wet mode, both in a dry mode, or in a hybrid mode in which the controller is configured to operate one of the first or second dispenser is operated in the wet mode while simultaneously operating the other dispenser in the dry mode, wherein when operating in the hybrid mode the controller is configured to generate a first airflow rate through the flow path having a dispenser operating in the dry mode and to generate a second airflow rate through the flow path having a dispenser operating in the wet mode, wherein the first airflow rate is greater than the second airflow rate. a first flow path positioned between an air intake and an air discharge outlet of the heat exchanger; a second flow path between an air intake and an air discharge outlet of the heat exchanger; a fluid conduit comprising: a first cooling region positioned within the first flow path; and a second cooling region positioned within the second flow path; a first cooling region positioned within the first flow path; and a second cooling region positioned within the second flow path; an airflow generator (106, 107) configured to move air through the first and second flow paths; at least one dispenser comprising a first dispenser positioned within the first airflow path to dispense evaporative fluid on the first cooling region and a second dispenser positioned within the second airflow path to dispense evaporative fluid on the second fluid region, wherein each of the first and second dispensers are configured to operate in a wet mode whereby the dispenser dispenses evaporative liquid and a dry mode whereby the dispenser does not dispense evaporative fluid; and a controller in communication with the airflow generator (106, 107) and the dispenser, characterised in that the controller is configured to regulate airflow through the first flow path and the second flow path, and wherein the controller is configured to set the dispensing mode of the at least one dispenser, wherein the controller is configured so that the dispense mode of the first dispenser can be set independently of the dispense mode of the second dispenser, wherein the first and second dispensers can thus be operated both in a wet mode, both in a dry mode, or in a hybrid mode in which the controller is configured to operate one of the first or second dispenser is operated in the wet mode while simultaneously operating the other dispenser in the dry mode, wherein when operating in the hybrid mode the controller is configured to generate a first airflow rate through the flow path having a dispenser operating in the dry mode and to generate a second airflow rate through the flow path having a dispenser operating in the wet mode, wherein the first airflow rate is greater than the second airflow rate. the controller is configured to regulate airflow through the first flow path and the second flow path, and wherein the controller is configured to set the dispensing mode of the at least one dispenser, wherein the controller is configured so that the dispense mode of the first dispenser can be set independently of the dispense mode of the second dispenser, wherein the first and second dispensers can thus be operated both in a wet mode, both in a dry mode, or in a hybrid mode in which the controller is configured to operate one of the first or second dispenser is operated in the wet mode while simultaneously operating the other dispenser in the dry mode, wherein when operating in the hybrid mode the controller is configured to generate a first airflow rate through the flow path having a dispenser operating in the dry mode and to generate a second airflow rate through the flow path having a dispenser operating in the wet mode, wherein the first airflow rate is greater than the second airflow rate.