ENERGY
Back to school: the Mollier diagram
The state of the room air, inlet air and outside air is an important influential factor, but correctly understanding the notorious Mollier diagram is essential to correctly
understanding the state of the air. Do you remember the details? By Jan Gielen, DLV PLant Mushrooms,
j.gielen@
dlvplant.nl
T
This article was made possible due a contribution from the Dutch Steering Committee for Clean & Effi cient Mushroom Growing. This committee unites LTO Mushroom Group, the Product Board for Horticulture, the Ministry of Economic Aff airs, the Netherlands Enterprise Agency and Dutch mushroom growers and aims to facilitate energy savings and the application of renewable energy.
he title above might not seem to have all that much to do with energy saving. However, one of the greatest opportunities to save energy is our
own behaviour: the way growers interact with the crop and the equipment in order to achieve optimal growth results. Monitoring data reveals situations where energy consumption is prac- tically double without there being any technical differences that could offer an explanation. Optimally utilising all the options available (certainly when faced with challenging growing conditions) often comes down to good insight and understanding of the influential factors that play a role.
The state of the room air, inlet air and outside air is a significant influential factor directly linked with yields and energy saving, is. To correctly understand of the state of the air and its possibil- ities, thorough knowledge of the Mollier diagram is essential. Despite the Mollier diagram being a permanent feature of professional training, and the attention paid to it in training courses, not every grower is familiar with, or remembers, all its details. This means that many of the new control-technical features of installations are not sufficiently clear, so their potential is not fully realised. This article aims to explain the basics of the diagram and the corresponding terminology as practically as possible. The following article in this series will handle the reaction of air during cooling, heating, humidifying and dehumidifying.
Mollier diagram
The Mollier diagram plots the most important parameters of the air and enables them to be looked up. Two parameters are needed to deter- mine a certain climate condition in the diagram: the temperature (dry bulb) and relative humidity (RH) are usually available, or otherwise the temperature and the wet bulb values. These values
26 MUSHROOM BUSINESS
can be used to determine the absolute humidity (AH / moisture content) and the enthalpy (heat content) of the air In fact, knowledge of just four lines on the chart is sufficient (see example 1): the horizontal temperature line, the RH curve, the vertical moisture content line and the sloping heat content line (to understand the basics, you can ignore all the other lines on the chart).
Temperature (dry bulb) and RH (example 1)
In the example below (which zooms into Mollier diagram), a temperature of 18°C and RH of 85% have been assumed. The corresponding climate state is found at the intersection of these (red) lines. From this point, you can find the moisture content by tracing vertically upwards (11 g/kg) and the heat content (46 kJ/kg) by tracing the sloping line downwards to the right. This is the entire foundation of the Mollier diagram!
Example 1.
Temperature (dry bulb) and wet bulb (example 2) The second example assumes a temperature / dry bulb of 18°C and a wet bulb of 16.3°C. The corresponding climate condition is now found by starting with the wet bulb temperature and looking for the point on the 100% RH line on the
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