CULTIVATION AND TECHNOLOGY English grower goes Dutch HOW DOES THE HEATING SYSTEM OPERATE? The heaters prevent the temperature of the product from dropping as a result of which you can continue the drying process. In hot and wet conditions, it remains a challenge to dry the potatoes in the store, because these conditions are ideal for rot. To prevent quality and weight losses as much as possible, it is essential to speed up the drying process. It is essential to have a heating system in place, according to Omnivent. Let’s go back to the basis: You can only dry potatoes when the outside air has a lower humidity than the air in the storehouse. In physical terms, this is called Relative Humidity (RH). For each temperature, there is a maximum quantity of water the air can contain. This is called the dew point. The well-known Mollier chart shows these figures accurately. As long as the dew point of the outside air is lower than that point in the storehouse, you can dry your potatoes without any problem. So, what exactly is the problem if the temperature of the potatoes and the outside temperature is approximately the same? Drying is a natural process whereby air flows along the potato and absorbs moisture as long as the dew point is lower. This absorption process costs energy and this is extracted from the storage product. As a result, the temperature of the potato drops. This means that the temperature drops as the potatoes dry. This process accelerates when the outside temperature is lower than the product temperature. Once the temperature of the potato is on equal level with the outside air temperature, the drying process stops. The dew point of the outside air and the temperature of the product are then equal. This is a situation that was seen virtually everywhere in Europe this year. Should you decide to continue to ventilate with outside air at this point, you take unnecessary moisture into the storehouse. By using the heating system, you put, in fact, extra energy into the air which is used for the energy necessary to evaporate the water of the product (potatoes). As a result, the temperature of the product will not drop and you can continue your drying process. It is, of course, necessary to bring in fresh air when you are using gas heaters. How you do this, depends on the type of heater you have installed, for which you can consult your storage advisor. Large propane tanks ensure the gas reserves. 36 Potato World 2012 • number 2 Pagina 35
Pagina 37Scoor meer met een webwinkel in uw gidsen. Velen gingen u voor en publiceerden artikelen online.
Potatoworld 2012/2 Lees publicatie 24Home