Method and system for temperature control in refrigerated storage spaces

Abstract

The present invention relates to a method of controlling air temperature within a refrigerated storage space based on a temperature-error integral of supply air discharged into the storage space. Another aspect of the invention relates to a refrigerated storage space comprising a corresponding temperature control system.

Description

[0001]The present invention relates to a method of controlling air temperature within a refrigerated storage space based on a temperature-error integral of supply air discharged into the storage space. Another aspect of the invention relates to a refrigerated storage space comprising a corresponding temperature control system.BACKGROUND OF THE INVENTION[0002]It is important to maintain the temperature of perishable produce held in refrigerated storage spaces at a desired or setpoint temperature. The setpoint temperature is chosen to keep the perishable produce such as meat, vegetables and fruit, at correct temperature to avoid quality degradation. It is known in the art to apply temperature control protocols that selectively control operational states of heaters, cooling devices and internal fans such as evaporator fans of cooling units, coupled to the refrigerated storage space, to maintain a setpoint air temperature inside the refrigerated storage space. The refrigerated storage s...

AI Technical Summary

Benefits of technology

[0015]In accordance with the present invention, the temperature of the cooled supply air or supply air is adjusted based on the temperature-error integral, which is an integral over the difference between the supply air temperature and the predetermined reference temperature. The use of the supply air temperature-error integral allows wider fluctuation of instantaneous supply air temperature while yet providing accurate control of average supply air temperature over time. In contrast, traditional temperature control algorithms or schemes seek to maintain the instantaneous supply air temperature at setpoint temperature, possibly within upper and lower temperature limits. The wider fluctuations of the instantaneous supply air temperature afforded by the present temperature control methodology or scheme enables exclusively switching operational states of the cooling unit or device between ON and OFF while maintaining accurate control over the time-averaged supply air temperature. The exclusive switching of operational states of the cooling unit between ON and OFF, while maintaining accurate control over the time-averaged supply air temperature such as within the above-mentioned temperature deviations, may be provided by pure integral control (1-control) based adjustment of the supply air temperature based on a current value of an error signal derived from, or constituted by, the temperature-error integral.

[0061]According to an advantageous embodiment, the temperature control system of the refrigerated storage space is adapted to adjust the reference temperature as a function of a setpoint temperature and a temperature of the return air measured by a return air temperature sensor. In this embodiment, the temperature control system is preferably further adapted to adjust the reference temperature such that the average of the supply air temperature and the return air temperature substantially equals the setpoint temperature. By controlling the average of the supply air temperature and the return air temperature to the setpoint temperature, improved produce quality preservation can be achieved due to improved produce temperature control. The present inventors have exploited the fact that average produce temperature in the refrigerated transport volume is closer to the mean of the supply and return air temperature than to the supply air temperature.

Problems solved by technology

Despite various attempts to lower energy consumption of the cooling units, substantial amounts of energy are still consumed in today's refrigerated storage spaces.

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