A dehumidification system comprising - a sorption dehumidifier unit; - a process air circuit arranged to conduct a process air flow through desiccant material in the dehumidifier unit; - a regeneration air circuit arranged to conduct a regeneration air flow through desiccant material in the dehumidifier unit; and - a heat pump comprising an evaporator and a condenser, wherein the system further comprises - a process air cooling heat exchanger arranged before inlet of the process air into the dehumidifier unit, - an intermediate fluid circuit with a cooling fluid, arranged to cool the process air in the heat exchanger before inlet of the process air into the dehumidifier unit, said intermediate fluid circuit comprising a fluid pump and a main conduit arranged to conduct cooling fluid through the process air cooling heat exchanger and through the evaporator of the heat pump, and the intermediate fluid circuit further comprising a flow control system arranged to control the flow of cooling fluid in the intermediate fluid circuit to obtain a measured cooling fluid temperature dependent parameter value in the intermediate fluid circuit upstream of the process air cooling heat exchanger, which corresponds to a given set-point cooling fluid temperature dependent parameter value (T1 set), wherein the flow control system includes a control unit, and measuring equipment for determining the cooling fluid temperature dependent parameter value, wherein said measuring equipment is suitably arranged in the system in the flow conduit between the pump and the process air cooling heat exchanger, and wherein means are provided for forwarding information of the determined parameter value to the control unit, which is arranged to compare the determined parameter value with a given set-point cooling fluid temperature dependent parameter value (T1 set) of the cooling fluid, and means are provided for acting on the flow control system to adjust the cooling fluid flow in the different parts of the intermediate fluid circuit based on the value. - a sorption dehumidifier unit; - a process air circuit arranged to conduct a process air flow through desiccant material in the dehumidifier unit; - a regeneration air circuit arranged to conduct a regeneration air flow through desiccant material in the dehumidifier unit; and - a heat pump comprising an evaporator and a condenser, - a process air cooling heat exchanger arranged before inlet of the process air into the dehumidifier unit, - an intermediate fluid circuit with a cooling fluid, arranged to cool the process air in the heat exchanger before inlet of the process air into the dehumidifier unit, said intermediate fluid circuit comprising a fluid pump and a main conduit arranged to conduct cooling fluid through the process air cooling heat exchanger and through the evaporator of the heat pump, and the intermediate fluid circuit further comprising a flow control system arranged to control the flow of cooling fluid in the intermediate fluid circuit to obtain a measured cooling fluid temperature dependent parameter value in the intermediate fluid circuit upstream of the process air cooling heat exchanger, which corresponds to a given set-point cooling fluid temperature dependent parameter value (T1 set), wherein the flow control system includes a control unit, and measuring equipment for determining the cooling fluid temperature dependent parameter value, wherein said measuring equipment is suitably arranged in the system in the flow conduit between the pump and the process air cooling heat exchanger, and wherein means are provided for forwarding information of the determined parameter value to the control unit, which is arranged to compare the determined parameter value with a given set-point cooling fluid temperature dependent parameter value (T1 set) of the cooling fluid, and means are provided for acting on the flow control system to adjust the cooling fluid flow in the different parts of the intermediate fluid circuit based on the value.