A dehumidification method for a refrigeration system of a transport container, the refrigeration system comprising a refrigeration circuit, a control unit, a cooling compartment, a target air temperature, and a target air moisture percentage;
- wherein the refrigeration circuit comprises a compressor, an expansion valve, a condenser, and an evaporator;
- wherein the cooling compartment comprises a cooling space for cooling air, which is separated from the rest of the cooling compartment and which defines an air flow channel for providing cooled air into the cooling compartment, the cooling space comprising means to blow air through the cooling space, the evaporator, a temperature sensor placed adjacent to the surface of the evaporator, a moisture sensor arranged upstream of the evaporator, and heating elements arranged downstream of the evaporator;
- wherein the control unit determines a first shift condition to shift from a dehumidification mode to a re-establish mode, and a second shift condition to shift from the re-establish mode to the dehumidification mode;
- wherein the first shift condition to shift from dehumidification mode to re-establish mode is when an air temperature in the cooling compartment is more than a first preselected non-zero number of degrees Celsius different from the target air temperature;
- and
- the dehumidification method comprising the steps of:
- the control unit entering the refrigeration system into the dehumidification mode,
- the control unit shifting the refrigeration system to the re-establish mode when the first shift condition is reached,
- the control unit shifting the refrigeration system to the dehumidification mode when the second shift condition is reached,
- repeating the steps of shifting to the re-establish mode and shifting to the dehumidification mode until the target air moisture percentage is reached;
- wherein the dehumidification mode comprises the steps of:
- blowing air over the evaporator,
- measuring with the moisture sensor an air moisture percentage and air temperature of air blown through the cooling space before the air reaches the evaporator,
- determining by the control unit a dew point temperature based on the measured air moisture percentage and air temperature of the air blown through the cooling space,
- determining by the control unit a target evaporator surface temperature that is lower than the dew point temperature,
- regulating by the control unit the surface temperature of the evaporator by controlling the refrigeration circuit so the surface temperature of the evaporator corresponds to the determined target evaporator surface temperature, and
- warming up the air with the heating elements after the air passes over the evaporator;
- and
- wherein, during repeating the steps of shifting to the re-establish mode and shifting to the dehumidification mode until the target air moisture percentage is reached, each target evaporator surface temperature determined by the control unit is lower than the preceding determined target evaporator surface temperature
- wherein the second shift condition to shift from re-establish mode to dehumidification mode is that an air temperature in the cooling compartment is less than a second preselected number of degrees Celsius different from the target air temperature, the second preselected number degrees being less than the first preselected numbers of degrees;
- and
- wherein during the re-establish mode the refrigeration system is operated so as to cause the air temperature in the cooling compartment to increase up toward, or decrease down toward the target air temperature.