Using CFD to investigate the ventilation performance of storage systems for potatoes

Gepubliceerd op
11 juni 2014

Potato storage is critical to all facets of the modern potato industry. To maintain potato quality during storage, the storage environment must be adjusted to minimize tuber deterioration. Temperature, humidity and air movement can always affect the keeping quality of stored potatoes.

The conditions in stores are dynamic; the crop is respiring and reacting to its environment. To guarantee a top quality product, storage conditions must be well controlled, which require a knowledge of heat transfer as well as moisture loss and their dependency on the airflow within the storage chamber. The unscientific approaches to reduce the energy consumption generally result in increased storage losses and vice versa, because the parameters governing the energy consumption and storage loses are interrelated. Therefore, understanding of these problems is the first step towards possible improvements. To get an insight view of the problems of energy consumption and storage losses, a thorough knowledge of airflow, temperature and relative humidity distribution in the storage chamber is necessary. The required knowledge can be obtained either through experimentation or numerical simulation.

To the direction of improvement the performance of storage systems with respect to energy consumption and product losses, the use of CFD as design tool offer unlimited capabilities in the potato processing industry, such as:

  • To identify the weak parts in the design and operation of an existing storage system and propose the subsequent cost effective improvements.
  • To investigate the effect of air velocity, storage air temperature and relative humidity
  • To investigate how the initial quality of potatoes affects the storage ability of the tuber.
  • To study the effect of stack dimensions, stacking arrangement and gaps between the stacks
  • To determine the gaseous composition of storage environment and hence, the required frequency for air refresh
  • To calculate the rate of loading the potatoes in the chamber compatible with the cooling capacity
  • To propose modifications in the arrangement of cooling coils and fans
  • To identify of the probable conditions of storage air leading to quality deterioration
  • To design a completely new storage system

One of the most popular storage systems for potatoes is the “Box storage with a pressure-wall”. The pressurized air either is sucked or is blown via the pallets through the product in the boxes. The operators tend to adjust the system to the box with minimum ventilation rate, which means to over ventilate. In order to investigate this type of storage system, experiments have been conducted to measure the air velocity in different locations and a CFD computational model has been developed to analyse the air flow patterns and to propose design improvements.

Contours of velocity magnitude (m/s) inside the wooden boxes filled with potatoes)
Contours of velocity magnitude (m/s) inside the wooden boxes filled with potatoes)