Processes for controlling the rate and temperature of cooling fluid through a heat exchange zone in, for example, an alkylation reactor using an ionic liquid catalyst. A cooling fluid system may be used to provide the cooling fluid which includes a chiller and a reservoir. The cooling fluid may pass from the reservoir through the heat exchange zone. A bypass line may be used to pass a portion of the cooling fluid around the heat exchange zone. The amount of cooling fluid may be adjusted, with a valve, based upon the temperature of the cooled process fluid flowing out of the heat exchange zone. Some of the cooling fluid from the chiller may be circulated back to the chiller in a chiller loop.