Optimizing air flow distribution in maritime refrigerated containers

In many types of maritime reefer container shipments there is a wish to reduce product temperature gradients. Temperature gradients are aggravated by poor air flow distribution. T-bars are the air ducts of reefer containers. Unfortunately most air escapes from the ducts before reaching the container door-end if no further measures are taken. The main aim of this experimental study is to design an optimised T-bar floor cover and assess its effect on cargo temperature distribution. In a series of 20 climate chamber tests it is investigated how temperature gradients are affected by evaporator fan speed, humidity setting, and four different T-bar cover designs. During the tests the container is stuffed with palletized empty cartons, with zero autonomous heat production. The results show clear positive effects of T-bar covers. The best of the four covers is non-perforated, of a trapezoidal-like shape, installed in the container with the narrowest end towards the door-end. It reduces the temperature difference between warmest and coldest measurement location directly around the cargo by nearly 50%, and also accelerates temperature recovery after a power off period. It is therefore recommended to follow- up on these results with real transport tests, and to investigate how a simple cheap robust version of this prototype floor cover can be made available to Maersk Line customers.