Humidity control in a refrigerated transport container with an intermittently operated compressor

Abstract

There is a growing need for dehumidification control in refrigerated transport containers with an intermittently operated compressor. The disclosed system and method of dehumidification control, controlling the speed of one or more evaporator fans and a heating unit, meets that need using one or more dehumidification need indicators and one or more condensation indicators. More specifically a system for and method is disclosed, comprising: controlling the operation of the one or more evaporator fans (10) for dehumidification purposes according to: if a need for dehumidification is determined using at least one dehumidification need indicator and if at least one condensation indicator indicates that the evaporator (16) is sufficiently cold respectively too warm for condensation or deposition of water vapor on its external surface, then setting or maintaining the speed of the one or more evaporator fans (10) to a reduced speed (LOW) in order to increase a condensation or deposition rate respectively to an increased speed (HIGH) in order to increase heat load to the evaporator (16), respectively. In other embodiments the system and method controls the heating unit as well.

Description

[0001]The present invention relates to a method of and a system for dehumidification control in a refrigerated transport container thereby controlling relative humidity within a refrigerated storage space with an intermittently operated compressor.BACKGROUND OF THE INVENTION[0002]Temperature in a refrigerated storage space is controlled within a temperature range adjacent to a setpoint or target temperature. The refrigerated storage space may for example comprise a transport volume of a refrigerated transport container. The setpoint temperature is chosen to keep perishable produce such as meat, vegetables and fruit or other, at correct temperatures to avoid quality degradation.[0003]In many shipments of perishable goods, not only should the temperature be controlled, but the humidity should be decreased as well to protect the carried commodity from mould growth and / or condensation. Humidity in a refrigerated storage space is then controlled within a humidity range adjacent to a setp...

AI Technical Summary

Benefits of technology

The patent describes a method for controlling the speed of evaporator fans and activating the heating unit of a dehumidifier based on the humidity level and the duration of the dehumidification process. The control system minimizes energy usage and prevents damage to unit hardware by only changing the state of the heating unit, compressor, and evaporator fans when there is a minimum duration of being in a given state. The technical effects of the patent include increased efficiency of the dehumidifier, reduced energy usage, and improved unit reliability.

Problems solved by technology

However, using an intermittently operated compressor as opposed to using a continuously running compressor in order to save energy presents a new situation for dehumidification control.

The two factors of increasing condensation or deposition rate of water vapour described above are not working so straightforwardly in relation to an intermittently operated compressor.

A further issue is how to indicate a need for dehumidification when using an intermittently operated compressor as an intermittently operated compressor naturally will introduce minor temperature variations where the temperature variations will cause variations in relative humidity.

So simply the difference between current relative humidity and a relative humidity setpoint, an otherwise classical and reliable dehumidification need indicator in systems with a continuously running compressor, is no longer an optimal dehumidification need indicator in systems with an intermittently operated compressor.

Dehumidification is a very energy-consuming process.

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